Tue·Sep 30, 2025Tuesday·September 30, 2025

1. 01*

   BBN bounds on neutrinophilic ultralight Dark Matter

   Toni Bertólez-Martínez🇪🇸 · Justo López-Sarrión🇪🇸 · Jordi Salvado🇪🇸

   The high densities in the early Universe provide a unique laboratory to constrain couplings between feebly interacting particles, such as dark matter and neutrinos. In this article, we study how Big Bang Nucleosynthesis can constrain models of Ultra-Light Dark Matter diagonally coupled to neutrinos. We follow an adiabatic formalism which allows to average-out the rapid oscillations of the Dark Matter field and consistently take into account the feedback between the neutrino and the Dark Matter fields. This feedback alters the early Universe dynamics, causing the Dark Matter energy density to scale as radiation, while the neutrino mass scales as $a^{-1}$. These two effects modify primordial element abundances by modifying interaction rates and the expansion rate during nucleosynthesis. Then, we use primordial abundances to obtain leading cosmological bounds on the coupling in the range $m_{\varphi }/\mathrm{eV}\in (10^{-22},10^{-17})$, namely $g\lesssim 0.13(m_{\varphi }/\mathrm{eV})$ for $m_{\varphi }\gtrsim 3\times 10^{-20}\mathrm{eV}$ and $g\lesssim 1.8\times 10^{-11}\sqrt{m_{\varphi }/\mathrm{eV}}$ for $m_{\varphi }\lesssim 3\times 10^{-20}\mathrm{eV}$. This consistent cosmological treatment emphasizes that, in the mass interval where its physical assumptions hold, neutrino masses cannot be generated refractively by a direct coupling with an Ultra-Light Dark Matter field.

   hep-phastro-ph.COJCAP(2026)·1 citation
2. 02*

   BCS superconductivity in the presence of wave dark matter

   Yechan Kim🇰🇷 · Hye-Sung Lee🇰🇷 · Jiheon Lee🇰🇷 · Jaeok Yi🇰🇷

   In the established era of dark matter, condensed matter Hamiltonians-including those of superconductors-may require extension to account for the surrounding Galactic environment. We show that if dark matter is wave-like and couples weakly to electrons, superconducting parameters such as the gap and critical temperature become dynamical quantities that oscillate in time. This modifies the Bardeen-Cooper-Schrieffer framework and produces distinctive temporal signatures whose sensitivity increases with longer measurement durations. Our results illustrate how condensed matter systems, traditionally treated as isolated from their cosmological environment, may acquire new dynamical degrees of freedom from their cosmic embedding. This, in turn, offers a novel window into the dark sector.

   hep-phcond-mat.supr-con1 citation
3. 03*

   Theory of Quarkonia as Probes for Deconfinement

   Xiaojun Yao🇺🇸

   This is a plenary talk given at Quark Matter 2025, summarizing recent theoretical developments for the understanding of quarkonium production in relativistic heavy ion collisions and how quarkonium uniquely probes the deconfined phase of QCD matter.

   hep-phnucl-thEPJ Web Conf.(2026)·1 citation
4. 04*

   Spectroscopic study of $ss\bar{b}\bar{b}$ and $bb\bar{b}\bar{b}$ Tetraquarks using Regge phenomenology

   Vandan Patel🇮🇳 · Juhi Oudichhya🇮🇳 · Ajay Kumar Rai🇮🇳

   In this work, we investigate the mass spectra of doubly strange-doubly bottom (ssbb) and fully bottom (bbbb) tetraquark states using the framework of Regge phenomenology. By modeling these tetraquarks as bound diquark-antidiquark systems, we employ quasi-linear Regge trajectories to study both orbital and radial excitations. Within this formalism, we derive linear and quadratic mass inequalities that impose constraints on the masses of ground and excited states of tetraquarks in the (J, M^2) plane. We further extend the analysis to radial excitations through the construction of Regge trajectories in the (n, M^2) plane. Our results show that this phenomenological approach offers a simple yet robust tool for describing tetraquark mass spectra, reproducing trends consistent with other theoretical predictions. The findings serve as valuable references for future experimental searches and may aid in the spin-parity classification of exotic hadrons. Overall, this study contributes to a deeper understanding of multiquark dynamics and hadron spectroscopy within the framework of Quantum Chromodynamics.

   hep-phInt.J.Mod.Phys.A(2025)·8 citations
5. 05*

   Scrutinizing dark-matter scenarios with $B\to (K,K^{\ast })\bar{\nu }\nu$ decays

   Alexander Berezhnoy🇷🇺 · Wolfgang Lucha🇦🇹 · Dmitri Melikhov🇷🇺

   Conceivable explanations of Belle-II measurements of a (surprising) excess of missing-energy decays of the $B$ meson to the $K$ meson not covered by standard-model neutrino-antineutrino pairs might be offered by additional contributions of dark-matter fermion-antifermion pairs. Assuming the excessive missing-energy events to be mediated by a (generic) scalar or vector boson, a simultaneous inspection of both of the missing-energy $B$ decays into a pseudoscalar $K$ meson or a vector $K^{\ast }$ meson allows to gain information on the nature of bosons relating standard-model and dark-matter sectors, irrespective of any (unknown) dark-sector details. Upon availability of indispensable experimental data, most prominent among such insights might be the identification of the mediator spin from the differential $B$-meson decay widths.

   hep-phhep-exUniverse(2025)·5 citations
6. 06*

   Higher-order QCD and electroweak corrections for $t\bar{t}H$ production

   Nikolaos Kidonakis🇺🇸 · Nodoka Yamanaka🇯🇵

   We calculate higher-order soft-gluon corrections for the associated production of a top-antitop quark pair and a Higgs boson ($t\bar{t}H$ production) using resummation in one-particle-inclusive (1PI) kinematics. By adding these corrections to NLO QCD and NLO electroweak (EW) results, we present cross sections through approximate N${}^3$LO (aN${}^3$LO) in QCD and NLO in EW for $t\bar{t}H$ production at LHC energies. These aN${}^3$LO QCD + NLO EW results provide significant enhancements over lower orders and a reduced scale dependence. Based on our results and current experimental data, we derive a constraint on the deviation of the top quark Yukawa coupling from the Standard Model value which is a probe of new physics beyond it. We also calculate top-quark differential distributions in transverse momentum and rapidity.

   hep-phPLB(2026)·4 citations
7. 07*

   Complete Classification of Domain Wall Solutions in the ${\mathbb{Z}}_2$-symmetric 2HDM

   Richard A. Battye🇬🇧 · Steven J. Cotterill🇬🇧 · Adam K. Thomasson🇬🇧

   We present a complete classification of domain wall solutions in the two-Higgs Doublet Model (2HDM) with a global ${\mathbb{Z}}_2$ symmetry, categorised as superconducting, CP-violating, or neither, depending on the scalar particle masses and the ratio of the two Higgs doublets' vacuum expectation values. We demonstrate that any domain wall solution can be reduced to depend on only six of the eight general field components, with further field reductions possible within different regions of the parameter space. Furthermore, we show that the superconducting solutions can be used to construct stable, current-carrying domain walls in two spatial dimensions. Similarly, the CP-violating solutions allow for two-dimensional configurations where CP symmetry is locally broken on the ${\mathbb{Z}}_2$-symmetric wall, which could provide an out-of-equilibrium environment for CP-violating processes to occur.

   hep-phastro-ph.COhep-thPRD(2025)·3 citations
8. 08*

   The Light Neutralino Dark Matter at Future Colliders in the MSSM with the Generalized Minimal Supergravity (GmSUGRA)

   Imtiaz Khan🇨🇳 · Ali Muhammad🇨🇳 · Tianjun Li🇨🇳 · Shabbar Raza🇵🇰 · Pirzada🇨🇳 · Mussawir Khan🇨🇳

   We perform a detailed investigation of light right-handed slepton bulk regions, together with the Higgs- and $Z$-resonance regimes, in the Minimal Supersymmetric Standard Model (MSSM) with Generalized Minimal Supergravity (GmSUGRA), focusing on the higgsino mass parameter scenario $\mu <0$, given that the anomalous magnetic moment of the muon may now be consistent with the Standard Model (SM) prediction. A systematic numerical exploration of the parameter space is carried out, where the bulk region is conservatively defined by the mass-splitting ratio \[ \mathcal{R}_{\tilde{\phi}} = \frac{m_{\tilde{\phi}} - m_{\tilde{\chi}_1^0}}{m_{\tilde{\chi}_1^0}} \gtrsim 10\%. \] In particular, we analyze the case in which the right-handed stau (${\tilde{\tau }}_R$) emerges as the Next-to-Lightest Supersymmetric Particle (NLSP). We uncover a sizeable parameter space consistent with current experimental bounds, including limits from LHC supersymmetry searches, the Planck 2018 relic density measurement, and direct detection constraints on neutralino-nucleon scattering. This region naturally accommodates bulk annihilation channels mediated by right-handed sleptons. We obtain robust upper bounds on the masses of the lightest neutralino, $m_{{\tilde{\chi }}_1^0}\lesssim 143\text{GeV}$, and the right-handed stau, $m_{{\tilde{\tau }}_R}\lesssim 158\text{GeV}$. The identified bulk region lies within the prospective reach of forthcoming dark matter direct detection facilities such as LUX-ZEPLIN, as well as future high-energy $e^{+}{e}^{-}$ colliders including FCC${}_{\text{ee}}$ and CEPC. Conversely, scenarios with the right-handed selectron as the NLSP have already been excluded by current LHC data. Furthermore, the parameter space consistent with our findings yields contributions to the anomalous magnetic moment of the muon, $a_{\mu }=(g_{\mu }-2)/2$.

   hep-phJHEP(2026)·5 citations
9. 09*

   Study of the semileptonic decay $\Lambda \to p\ell {\bar{\nu }}_{\ell }$ in QCD

   M. Ahmadi🇮🇷 · Z. Rajabi Najjar🇮🇷 · K. Azizi🇮🇷

   We conduct a comprehensive study of the semileptonic decay process \(\Lambda \to p\,\ell\,\bar{\nu}_{\ell}\), focusing on the determination of all six vector and axial-vector form factors that govern the low-energy hadronic matrix elements of the underlying theory. These invariant form factors constitute the essential inputs for describing the decay, and their dependence on the momentum transfer \(q^{2}\) is analyzed across the entire physical kinematic region. To parametrize the \(q^{2}\)dependence, we adopt both the \(z\)-expansion formalism and a polynomial fitting approach. Utilizing parametrizations, we compute the exclusive decay widths for both the electron and muon channels, and subsequently extract the corresponding branching ratios. Furthermore, we evaluate the ratio of decay widths between the muon and electron channels defined as $R^{\mu e}\equiv \frac{\Gamma (\Lambda \to p\mu {\bar{\nu }}_{\mu })}{\Gamma (\Lambda \to pe{\bar{\nu }}_e)}$ obtaining \(R^{\mu e} = 0.196^{+0.009}_{-0.012}\) from the polynomial fit and \(R^{\mu e} = 0.174^{+0.002}_{-0.005}\) from the \(z\) expansion. While both ratios are compatible with previously reported values in the literature, the result from the \(z\) expansion exhibits particularly strong agreement with the averages reported by the Particle Data Group.

   hep-phhep-exhep-latPRD(2025)·6 citations
10. 10*

    Dipolar electroweak properties of Dirac massive neutrinos

    J. P. Gutiérrez-Montes🇲🇽 · J. Montaño-Domínguez🇲🇽 · F. Ramírez-Zavaleta🇲🇽 · E. S. Tututi🇲🇽 · O. Vázquez-Hernández🇲🇽

    Electroweak properties of Dirac neutrinos within the context of the Minimally Extended Standard Model are explored. In particular, the dipolar form factors that result from the radiative correction, at one-loop level, of the $Z\nu \bar{\nu }$ coupling are identified. The calculation is carried out in the covariant general gauge $R_{\xi }$. The results are shown to be independent of the gauge parameter. The outcome numerical evaluation establishes that the neutrino weak-magnetic dipole moment is of the same order of magnitude as the known prediction of the neutrino magnetic dipole moment.

    hep-ph0 citations
11. 11*

    Type I + II Seesaw Model in light of the New Neutrino Oscillation Measurements

    Maria Aguilar🇧🇷 · Juan Carlos Helo🇨🇱 · Toshihiko Ota🇨🇱 · Farinaldo S. Queiroz🇧🇷 · David Suarez🇧🇷 · Amanda Rodríguez🇧🇷

    Global analysis of neutrino oscillation data slightly favors normal mass ordering. In this work, we investigate an extended scalar sector that naturally gives rise to a type I + II seesaw mechanism after spontaneous symmetry breaking and explore the interplay between collider physics and lepton flavor violation, adopting normal ordering. In particular, we focus on the rare muon decays $\mu \to e\gamma$ and $\mu \to 3e$ and the same-sign dilepton searches at LHC, a canonical signature of a doubly charged scalar. We conclude that neither the precise value of the sum of the neutrino masses, taken from DESI data that favors $\sum m_{\nu }=0.07$~eV, nor alternative cosmological fits which prefer a more relaxed limit $\sum m_{\nu }=0.1$~eV, significantly changes the theoretical prediction for these rare decays. However, we observe an interesting interplay between collider physics and lepton flavor violation depending on the choices of the vacuum expectation value of the triplet scalar. In particular, we find that $\mu \to 3e$ is more constraining than $\mu \to e\gamma$, and the $\mu \to 3e$ decay can yield a lower mass limit of $3$~TeV on the doubly charged scalar, surpassing current LHC constraint.

    hep-ph0 citations
12. 12*

    Electric Dipole Moments and New Physics

    Maxim Pospelov🇺🇸 · Adam Ritz🇨🇦

    Searches for intrinsic electric dipole moments (EDMs) of nucleons, atoms and molecules are precision flavor-diagonal probes of new $CP$-odd physics, as motivated by the need to explain the matter-antimatter asymmetry in the universe. We review and summarise the effective field theory analysis of the observable EDMs in terms of a general set of $CP$-odd operators at 1~GeV, and the ensuing model-independent constraints on new physics. We also review and discuss the EDMs induced by $CP$-violation in the Standard Model, and the implications of EDM limits for various models of physics beyond the Standard Model.

    hep-ph10 citations
13. 13*

    Noninflationary solution to the monopole problem

    Daniele Perri🇵🇱

    Magnetic monopoles are a long-standing prediction of Grand Unified Theories, yet their efficient production in early universe phase transitions would lead to a monopole abundance that far exceeds observational limits. The standard solution of the problem invokes inflation occurring after monopole production, diluting their density to undetectable levels and eliminating any possibility of present-day observation. Here, we propose an alternative solution based on the breaking, in the early universe prior to Big Bang Nucleosynthesis, of the Weyl conformal symmetry of the gauge kinetic sector of the Lagrangian. This mechanism enhances monopole annihilation, thereby reducing their abundance to acceptable levels without requiring inflation. This scenario also predicts a residual flux of GUT monopoles potentially within the sensitivity of current and upcoming cosmic ray detectors, making their discovery possible in the near future.

    hep-phastro-ph.COhep-thPRD(2026)·3 citations
14. 14*

    Finite-temperature stability from doublet inflation field with right-handed neutrinos

    Seong Chan Park🇰🇷 · Shilpa Jangid🇰🇷

    We study the augmentation of the Standard Model (SM) with another $SU(2)$ Higgs doublet and right-handed neutrinos. The second Higgs doublet (${\Phi }_2$) is defined to be odd under the $Z_2$ symmetry, and hence, the lightest stable neutral particle from the additional doublet becomes the cold dark matter candidate. The right-handed neutrino field coupled to the Higgs field provides non-zero mass for the neutrinos. The inert doublet field coupled non-minimally to gravity as ${\zeta }_2{\Phi }_2^{†}{\Phi }_{2}R$ also acts as an inflaton field. The inflationary bounds restrict the interaction couplings as ${\lambda }_2/{\zeta }_2^2\approx 4\times 10^{-10}$. After inflation ends, the scalar bosonic degrees of freedom from the inert doublet can contribute to the electroweak phase transition. The strongly first-order phase transition bound, i.e., $\frac{{\varphi }_{+}(T_c)}{T_c}\ge 1.0$ restricts the bare mass parameter of the additional doublet to $m_{22}=400.0$ GeV, demanding GUT scale perturbative unitarity for $Y_N=0.01$. The increase in $Y_N$ reduces the strength of phase transition, and it is no longer satisfied even for vanishing bare mass parameter. The Planck scale perturbative unitarity allows for the first-order phase transition, $\frac{{\varphi }_{+}(T_c)}{T_c}\ge 0.6$, until $m_{22}=70.0$ GeV for $Y_N=0.01$, and none of the mass values satisfies the first-order phase transition for $Y_N=0.4$. The thermal corrections also affect the probability of tunneling from the false vacuum to the true vacuum, and hence, the finite temperature stability of the electroweak vacuum has been studied, including the finite-temperature effects.

    hep-phPTEP(2026)·0 citations
15. 15*

    Diffusion wake: a distinctive consequence of the Mach-cone wake induced by supersonic jets in high-energy heavy-ion collisions

    Zhong Yang🇺🇸 · Xin-Nian Wang🇨🇳

    In this Research Perspective, we briefly review the diffusion wake, a distinctive consequence of the Mach-cone wake induced by the supersonic jets in ultra-relativistic heavy-ion collisions. The diffusion wake depletes soft hadrons in the direction opposite to the propagating jet. According to coupled transport and hydrodynamic simulations, a valley in the 2-dimensional jet-hadron correlation in azimuthal angle and rapidity arises on the top of the multiple parton interaction ridge as an unambiguous signal of the diffusion wake induced by $\gamma$-jets in heavy-ion collisions. In dijet events with a finite rapidity gap, the rapidity asymmetry of the jet-hadron correlation has been shown to be a robust signal of the diffusion wake. The same rapidity asymmetry can also be applied to $\gamma$-jet events and both are background free. Experimental measurements of these signals can provide valuable insights into the properties of the quark-gluon plasma (QGP) formed in high-energy heavy-ion collisions.

    hep-phResearch(2025)·5 citations
16. 16*

    Revisiting constraints on magnetogenesis from baryon asymmetry

    Yuta Hamada🇯🇵 · Kyohei Mukaida🇯🇵 · Fumio Uchida🇯🇵

    Magnetic fields in the universe potentially serve as a messenger of primordial physics. The observationally suggested intergalactic magnetic fields may be a relic of helical primordial $\mathrm{U}(1{)}_Y$ magnetic fields, which may also explain the origin of the baryon asymmetry of the universe. This scenario has been considered to be not viable, which we revisit as well as the baryon isocurvature problem for non-helical primordial $\mathrm{U}(1{)}_Y$ magnetic fields, based on the recent discussion on the hot electroweak theory. We find that maximally helical fields can be the origin of both the intergalactic magnetic fields and the baryon asymmetry of the universe and that there can be a window for non-helical fields to explain the origin of the intergalactic magnetic fields if the Higgs dynamics during the electroweak crossover compensate the helicity decay with a $\lesssim 10^{-9\text{–}-10}$ precision.

    hep-phastro-ph.COPRD(2026)·5 citations
17. 17*

    Soft-hard factorization of heavy-quark transport in QCD matter at finite chemical potential

    Jiale Lou🇨🇳 · Wu Wang🇨🇳 · Jiazhen Peng🇨🇳 · Fei Sun🇨🇳 · Kejun Wu🇨🇳 · Wei Xie🇨🇳 · Zuman Zhang🇨🇳 · Shuang Li🇨🇳 · Sa Wang🇨🇳

    We calculate the collisional energy loss and momentum diffusion coefficients of heavy quarks traversing a hot and dense QCD medium at finite quark chemical potential, $\mu \ne 0$. The analysis is performed within an extended soft-hard factorization model (SHFM) that consistently incorporates the $\mu$-dependence of the Debye screening mass $M_D(\mu )$ and of the fermionic thermal distribution functions. Both the energy loss and the diffusion coefficients are found to increase with $\mu$, with the enhancement being most pronounced at low temperatures where the chemical potential effects dominate the medium response. To elucidate the origin of this dependence, we derive analytic high-energy approximations in which the leading $\mu$-corrections appear as logarithmic terms: a soft logarithm $\sim {\mu }^2\ln (|t^{\ast }|/M_D^2)$ from $t$-channel scattering off thermal gluonic excitations, and a hard logarithm $\sim {\mu }^2\ln (E_{1}T/|t^{\ast }|)$ from scattering off thermal quarks. In the complete result the dependence on the intermediate separation scale $t^{\ast }$ cancels, as required. We also confirm the expected mass hierarchy $-dE/dz(charm)<-dE/dz(bottom)$ at fixed velocity. Our findings demonstrate that finite chemical potential plays a significant role in heavy-quark transport and must be included in theoretical descriptions of heavy-flavor dynamics in baryon-rich environments, such as those probed in the RHIC Beam Energy Scan, and at FAIR and NICA.

    hep-phPRD(2025)·3 citations
18. 18*

    One-loop expressions for $H^{\pm }\to W^{\pm }Z$ and their implications at muon--TeV colliders

    Dzung Tri Tran (DTU)🇻🇳 · Quang Hoang-Minh Pham (HCMUS)🇻🇳 · Khoa Ngo-Thanh Ho (HCMUS)🇻🇳 · Khiem Hong Phan (DTU)🇻🇳

    One-loop contributions for decay process $H^{\pm }\to W^{\pm }Z$ within the Two-Higgs-Doublet Model are computed in the general ${\mathcal{R}}_{\xi }$ gauge, and its phenomenological applications at future muon--TeV colliders are studied in this paper. The analytic results are confirmed by several consistency tests, for example, the $\xi$-independence, the renormalization-scale stability and the ultraviolet finiteness of the one-loop amplitude. We first perform an updated parameter scan of the Type-X THDM in the phenomenological studies. The production of charged Higgs boson pairs at future muon--TeV colliders is investigated through the two processes ${\mu }^{+}{\mu }^{-}\to H^{+}{H}^{-}\to W^{\pm }{W}^{\mp }Zh$ and ${\mu }^{+}{\mu }^{-}\to \gamma \gamma \to H^{+}{H}^{-}\to W^{\pm }{W}^{\mp }Zh$. Both signal events and their significances are evaluated with taking into account the corresponding Standard Model backgrounds. We find that the signal significances can exceed $5\sigma$ at several benchmark points in the viable parameter space of the Type-X THDM.

    hep-phCPC(2026)·4 citations
19. 19*

    Probing Scalar-Mediated Sterile Neutrinos with Gravitational Wave and Colliders Signals

    Qi Bi🇨🇳 · Jinhui Guo🇨🇳 · Jian Liao🇨🇳 · Jia Liu🇨🇳 · Xiao-Ping Wang🇨🇳

    We propose a UV-complete extension of the Standard Model in which a gauge-singlet scalar $S$ acquires a vacuum expectation value, generates a Majorana mass for a sterile neutrino $N$, and mixes with the Higgs field. This framework addresses neutrino masses via a seesaw mechanism and, for sufficiently large scalar mixing, can also drive a strong first-order electroweak phase transition, producing gravitational-wave (GW) signals potentially detectable by GW observatories. The Higgs-$S$ mixing also enhances sterile-neutrino pair production at colliders through $s$-channel exchange of the Higgs and $S$. Owing to the small active-sterile mixing angle, $N$ is generically long-lived, yielding characteristic displaced-vertex signatures. The combination of GW observations and displaced-vertex searches at colliders provides complementary cross-checks of the model parameter space.

    hep-phPRD(2026)·1 citation
20. 20*

    Searching for axion-like particles from tau exotic decays at the Super Tau-Charm Facility and its far detectors

    Xu-Hui Jiang🇨🇳 · Chih-Ting Lu🇨🇳

    Leptophilic axion-like particles (ALPs) extend the Standard Model (SM) with brand-new interactions between the ALP and leptons. In this work, we focus on studying exotic $\tau$ decays to explore such ALPs. Both the tauphilic and lepton flavor universal (LFU) scenarios, with electroweak preserving and violating benchmarks, have been investigated at a future $\tau$-factory, namely the Super Tau-Charm Facility (STCF) under development in China. Both prompt and far detection are proposed, targeting on leptonic $\tau$ decays, ${\tau }^{-}\to {\ell }^{-}{\bar{\nu }}_{\ell }{\nu }_{\tau }a$. For prompt detection, the ${\tau }^{+}{\tau }^{-}$ threshold $\sqrt{s}=3.56$ GeV and higher central energy $\sqrt{s}=4.2$ GeV are taken into account. In addition, a cylinder-like far detector has been proposed to complement prompt detection. We demonstrate the huge potential to detect leptophilic ALPs at the STCF. Concretely, for tauphilic scenario, the STCF is mostly sensitive in the currently unprobed region with $m_a\sim 1000$ MeV. However, in the LFU scenario, the dilepton channel tremendously shortens the ALP lifetime, and eventually the STCF only allows a precise measurement in the new regime with $100\text{MeV}\lesssim m_a\lesssim 200\text{MeV}$.

    hep-phhep-ex5 citations
21. 21*

    Decoupling hydrodynamization from thermalization via nonlinear Boltzmann equation

    Xingjian Lu🇨🇳 · Shuzhe Shi🇨🇳

    The early thermalization puzzle arises from the unexpectedly early applicability of hydrodynamics in heavy-ion collisions. While hydrodynamics has traditionally been associated with the onset of local thermal equilibrium, its derivations -- whether microscopic or macroscopic -- rely instead on linearization around equilibrium. However, the linearization timescale -- the time at which a system's evolution begins to follow a linearized equation -- has not been systematically investigated. In this work, we employ the spectral nonlinear Boltzmann equation -- the lowest-order truncation of the spectral Bogoliubov--Born--Green--Kirkwood--Yvon (BBGKY) hierarchy -- to analyze the timescales of linearization and thermalization under three distinct truncation schemes. The first two truncations allow for analytic treatment via recursive spectral equations, while the third requires numerical methods for generic initial conditions. The analysis is performed for a homogeneous, massless system with a constant differential cross section. For this simplified setup, we find a robust separation: the linearization time is consistently about half the thermalization time (${\tau }_{\mathrm{lin}}/{\tau }_{\mathrm{therm}}\approx 1/2$). This separation of timescales suggests an explanation for the early applicability of hydrodynamics and points toward a possible quantitative resolution of the early thermalization puzzle.

    hep-phcond-mat.stat-mechmath-phmath.MP+13 citations
22. 22*

    Resonance Contributions to Radiative Corrections in Charged-Current Elastic (Anti)Neutrino-Nucleon Scattering at GeV Energies

    Oleksandr Tomalak🇨🇳

    We present the first evaluation of virtual resonance contributions to the charged-current (anti)neutrino-nucleon elastic scattering at GeV energies, focusing on the dominant $\Delta (1232)$ resonance. We approximate the vector part of the $N\to \Delta$ transition by the leading magnetic dipole term. Our results for the cross-section corrections at fixed neutrino energy indicate the permille-level contribution of resonance intermediate states to the elastic and radiative scattering cross sections. This calculation exhibits the expected infrared behavior of the invariant amplitudes and unpolarized cross sections. Our findings provide important insights into inelastic excitations in the charged-current (anti)neutrino-nucleon elastic scattering at GeV energies.

    hep-phnucl-exnucl-thPLB(2026)·2 citations
23. 23*

    Applications of Machine Learning in Constraining Multi-Scalar Models

    Darius Jurčiukonis🇱🇹

    Machine learning techniques are used to predict theoretical constraints such as unitarity and boundedness from below in extensions of the Standard Model. This approach has proven effective for models incorporating additional SU(2) scalar multiplets, in particular the quadruplet and sixplet cases. High predictive performance is achieved through the use of suitable neural network architectures and well-prepared training datasets. Moreover, machine learning provides a substantial computational advantage, enabling significantly faster evaluations compared to scalar potential minimization.

    hep-ph0 citations
24. 24*

    3D Structure of Jet-induced Diffusion Wake

    Zhong Yang · Xin-Nian Wang

    Jet-induced diffusion wake in heavy-ion collisions has a unique 3D structure as manifested in the jet-hadron correlations in rapidity and azimuthal angle. The rapidity asymmetry observable in dijets provides a robust measurement of the diffusion wake because it essentially background-free.

    hep-phEPJ Web Conf.(2026)·0 citations
25. 25*

    Energy loss of heavy-flavor quarks in color string medium

    Daria Prokhorova · Shuzhe Shi🇨🇳 · Evgeny Andronov🇷🇺

    The paper presents preliminary estimates of heavy-flavor (HF) quark energy loss during its propagation through the non-equilibrated medium formed in minimum bias proton-proton (p+p) collisions at LHC energies. The study is inspired by the ongoing hot debates on whether tiny droplets of Quark-Gluon Plasma can be created in collisions of small systems. In this work, we model a p+p event with a fluctuating number of color strings originated from multi-pomeron exchanges. Considered longitudinal oscillations of strings dynamically initialize medium at each time step. Their varying overlaps create fluctuations in the color field energy density that governs the elastic scattering rate of HF quarks with the gluons present within the string volume. We calculate the transverse momentum dependence of the momentum loss for charm (anti-)quarks that are produced in initial hard scatterings and traverse the described environment. The simulation is performed using a developed hybrid approach on an event-by-event basis. Our results show significantly lower HF quarks energy loss compared to that obtained in the expanding hydrodynamic scenario of the new EPOS4HQ model.

    hep-phIJMPE(2026)·0 citations
26. 26*

    Resonance sum rules: an application to the square well potential

    Zi-Xi Ou-Yang🇨🇳 · Philipp Gubler🇯🇵 · Makoto Oka🇯🇵 · Guang-Juan Wang🇯🇵 · Jia-Jun Wu🇨🇳

    We propose an extension of the Quantum Chromodynamics (QCD) sum rules, termed the Resonance sum rules (RSR), to access resonance poles in the complex energy plane. By strategically introducing a contour in the complex plane and conformal mapping, the method intends to reach resonance poles on the second Riemann sheet. To validate this approach, we apply RSR to the square-well potential model, for which the pole locations are known. The analysis demonstrates a successful extraction of the pole positions and residues for both the $S$-wave and $P$-wave resonances. The results are in good agreement with the analytic solutions, with discrepancies within $5\%$ for the pole positions and $20\%$ for the residues.This framework provides a basis for future applications to realistic hadronic resonances, promising new insights into spectral properties of QCD.

    hep-phPRD(2025)·1 citation
27. 27*

    High Energy Particle Production from Proton Synchrotron Radiation in Strong Magnetic Fields in Relativistic Quantum Field Theory

    Tomoyuki Maruyama🇯🇵 · A.Baha Balantekin🇺🇸 · Myung-Ki Cheoun🇰🇷 · Akira Dohi🇯🇵 · Ryo Higuch🇯🇵 · Toshitaka Kajino🇨🇳 · Grant J. Mathews🇺🇸

    We investigate photon, pion, and rho-meson production from proton synchrotron radiation in the presence of strong magnetic fields. The proton decay widths and the luminosities of the emitted particles are calculated within a relativistic quantum framework that incorporates Landau quantization. A scaling rule is derived for the transition probability between different Landau levels. This allows an evaluation of transitions for extremely high Landau numbers exceeding $10^{15}$. Furthermore, we calculate the momentum distribution of the emitted particles by properly including the proton recoil effect associated with particle emission. The results differ significantly from conventional semiclassical approaches.

    hep-phastro-ph.HEPRD(2026)·0 citations
28. 28*

    Heavy flavor correlations and Quarkonia production in high energy pp collisions in the EPOS4 framework

    Jiaxing Zhao🇩🇪 · Taesoo Song🇩🇪 · Pol Bernard Gossiaux🇫🇷 · Klaus Werner🇫🇷 · Joerg Aichelin🇫🇷 · Elena Bratkovskaya🇩🇪

    In QCD, the production of heavy quark-antiquark pairs can proceed through different mechanisms, each imprinting characteristic correlations between the heavy quarks. In this work, we use the EPOS4 event generator to study how these correlations affect quarkonium production in pp collisions. Our results demonstrate that the observed correlations between heavy mesons directly reflect the underlying production mechanisms and simultaneously shape the transverse-momentum distributions of quarkonia.

    hep-phnucl-thEPJ Web Conf.(2026)·1 citation
29. 29*

    Ultra high energetic neutrinos in their rest frame: can their time of arrival be determined?

    Fedele Lizzi🇮🇹

    In the light of the recent observation by the KM3NeT collaboration of an ultrahigh energetic neutrino, we analyse it in its rest frame, where shortly after creation of the neutrino a muon arrives and interacts. Since the neutrino is at rest we use (in this first analysis) a non relativistic Gaussian wave function, and consider its spread. Due to the finite size of the packet, the time of the interaction of the muon will have an uncertainty. This uncertainty is small in the neutrino rest frame, but boosted to our frame, increases 18 orders of magnitude, making it extremely large. This effectively prevents the possibility of the observation of bursts, or the correlation with other events. A similar analysis for less energetic neutrinos show that the uncertainty is smaller than the duration of the observed bursts.

    hep-ph0 citations
30. 30*

    A brief introduction to dispersive methods

    Gilberto Colangelo🇨🇭

    These lectures aim to provide a basic introduction to dispersive methods and their modern applications to the phenomenology of the Standard Model at low energy. This approach exploits analyticity properties of Green functions and scattering amplitude, often combined with unitarity constraints. To find a logically coherent set of topics in this vast subject, I start with the two-point Green's function, show that this needs the three-point function as input which in turn needs the four-point function. The sequence stops here, just like these lectures, because the four-point function is related only to itself (if one ignores inelastic effects), I will discuss these dispersion relations both in the case of toy models, simple scalar theories, as well as in the phenomenologically relevant case of QCD.

    hep-phhep-latEur.Phys.J.ST(2026)·5 citations
31. 31*

    Focusing the Axion Wind with Ferrite Flux Concentrators

    Christina Gao🇨🇳 · Yuxuan He🇨🇳 · Yubo Mo🇨🇳 · Peiran Yin🇨🇳

    Axion dark matter may couple to fermion spins through an effective oscillating magnetic field, the ``axion wind". Existing approaches for detecting axion wind via axion-electron coupling $g_{ae}$ face sensitivity limitations due to the extremely weak pseudomagnetic field generated, typically a few times $10^{-18}$ tesla for $g_{ae}\sim 10^{-10}$. We propose to use ferrimagnetic flux concentrators to amplify the pseudomagnetic field into a genuine magnetic field, which can then be measured using general precision magnetometry techniques. This greatly expands the experimental possibilities beyond conventional methods that rely on detecting small transverse magnetic fields from spin precession induced by axion wind. Here we utilize the libration mode of a levitated ferromagnet, which can achieve sub-femtotesla sensitivity, enabling detection of axion-electron coupling strengths $g_{ae}\lesssim 10^{-11}$ in the frequency range $1-500$ Hz.

    hep-phhep-ex2 citations
32. 32*

    Non-extensive NJL model study of QCD phase structure with chiral imbalance and strong magnetic fields

    Xiang-Qiong Liu🇨🇳 · Sheng-Qin Feng🇨🇳

    Based on the two-flavor NJL model with Tsallis non-extensive statistics, this work explores the QCD phase structure and thermodynamic properties under strong magnetic fields and chiral imbalance. The Tsallis parameter $q$ captures non-equilibrium effects relevant to heavy-ion collisions. Key findings reveal that the critical temperature $T_c$ decreases with increasing $q$, indicating that non-equilibrium conditions promote chiral symmetry restoration at lower temperatures. The chiral chemical potential ${\mu }_5$ significantly alters the magnetic response, with a transition from magnetic catalysis to inverse magnetic catalysis under certain conditions. For $q>1$, non-monotonic behavior of $T_c$ with magnetic field $eB$ emerges. Pressure becomes anisotropic under strong $eB$, and the speed of sound exhibits a dip near $T_c$, shifting to lower temperatures with larger $q$. These results highlight how non-extensive statistics, chiral imbalance, and magnetic fields collectively influence the QCD phase diagram and thermodynamic observables, offering insights for interpreting heavy-ion collision data.

    hep-phEPJC(2026)·0 citations
33. 33*

    Heavy flavor angular correlations as probes of the glasma

    Dana Avramescu🇫🇮 · Vincenzo Greco🇮🇹 · Tuomas Lappi🇫🇮 · Heikki Mäntysaari🇫🇮 · David I. Müller🇦🇹

    We study the effect of the glasma fields, formed in the early stage of heavy-ion collisions, on the transport of $Q\bar{Q}$ pairs produced back-to-back. We find that for pairs with moderate initial transverse momentum $p_T$ evolving in glasma fields with sufficiently large saturation momentum $Q_s$, the azimuthal correlation $C(\Delta \varphi )$ is quickly affected. The decorrelation widths ${\sigma }_{\Delta \varphi }$ during the glasma and Quark Gluon Plasma (QGP) phases are comparable.

    hep-phhep-latnucl-thEPJ Web Conf.(2026)·0 citations
34. 34*

    Lepton number violating signals of a parity symmetric model at $\mu$TRISTAN

    Keisuke Harigaya🇺🇸 · Ryuichiro Kitano🇯🇵 · Ryoto Takai🇯🇵

    The parity solution to the strong CP problem necessarily extends the Standard Model to include the SU$(2{)}_{\mathrm{R}}$ gauge sector and imposes restrictions on the structure of the Yukawa interactions. In this framework, one can consider an appealing structure of the neutrino sector in which the smallness of the neutrino masses is naturally explained, while lepton number symmetry is substantially violated at the TeV scale. Observation of distinctive lepton number violating signals at collider experiments can therefore be expected, since the rates are not suppressed by the small neutrino masses. We study the constraints from neutrinoless double beta decay and discuss the prospects for discovering new TeV-scale particles, such as the $W^{\prime }$ boson of SU$(2{)}_{\mathrm{R}}$, via lepton number violating processes at a ${\mu }^{+}{\mu }^{+}$ collider, ${\mu }^{+}{\mu }^{+}\to W^{+}{W}^{\prime +}$. A ${\mu }^{+}{\mu }^{+}$ collider with a center-of-mass energy of 10 TeV can probe the $W^{\prime }$ boson mass up to about 10 TeV through on-shell production, and the reach can extend to 16 TeV by studying processes involving off-shell $W^{\prime }$ boson.

    hep-phJHEP(2026)·4 citations
35. 35*

    The real-time QCD static potential at high temperature

    Margaret E. Carrington🇨🇦 · Cristina Manuel🇪🇸 · Joan Soto🇪🇸

    We develop a procedure to analytically calculate higher-order contributions to the high-temperature real-time static potential in QCD. It is based on the introduction of a semi-hard external scale, which lies between the hard scale (the temperature) and the soft scale (the screening mass), and the method of integration by regions. We calculate the leading and next-to-leading corrections in the region where bound states transit from narrow resonances to wide ones. The calculation involves both loop diagrams calculated in the Hard Thermal Loop (HTL) effective theory and power corrections to the HTL Lagrangian calculated in QCD. We also calculate the thermal corrections to the heavy quarkonium spectrum, and estimate the dissociation temperatures. We compare our results with recent lattice data and discuss their usefulness to guide lattice inputs in inverse problems.

    hep-phPRD(2026)·0 citations
36. 36*

    Relativistic Flux Tube Model Predictions from Charmed Mesons to Double-Charmed Baryons

    Pooja Jakhad🇮🇳 · Ajay Kumar Rai🇮🇳

    Utilizing comprehensive experimental data on charmed mesons, we systematically investigate masses of the higher radial and orbital excitations of the $D$ and $D_s$ meson families using the relativistic flux tube model. Our study employs mass splitting induced by spin-dependent interactions within the j-j coupling scheme. Our predicted masses align well with the experimental measurements for the well-established $D$ and $D_s$ states. However, anomalous resonances such as $D_{s0}(2317)$ and $D_{s1}(2460)$ do not align with conventional meson states within our theoretical framework. Based on our reliable mass predictions for low-lying states, we propose spectroscopic assignments for several recently observed high-mass resonances: $D_2(2740{)}^0$, $D_3^{\ast }(2750)$, $D_0(2550{)}^0$, $D_1^{\ast }(2600{)}^0$, $D_1^{\ast }(2760{)}^0$, $D_J^{\ast }(3000)$, $D_J(3000)$, $D_2^{\ast }(3000)$, $D_{s1}^{\ast }(2860{)}^{\pm }$ and $D_{s3}^{\ast }(2860{)}^{\pm }$.Additionally, the resonance $D_{sJ}(3040{)}^{+}$ is identified as a $2P$ excitation with spin-parity quantum numbers $J^P=1^{+}$. Extending our model, we also calculate the mass spectra of doubly charmed ${\Xi }_{cc}$ and ${\Omega }_{cc}$ baryons within the heavy-diquark-light-quark picture. These theoretical predictions provide crucial guidance for ongoing and future experimental searches for higher radial and orbital excitations in the charmed meson and doubly charmed baryon sectors.

    hep-phPRD(2026)·7 citations
37. 37*

    Dynamical Prevention of Topological Defect Formation

    Junseok Lee🇯🇵 · Kai Murai🇯🇵 · Kazunori Nakayama🇯🇵 · Fuminobu Takahashi🇯🇵

    Topological defects can have significant cosmological consequences, so their production must be examined carefully. It is usually assumed that topological defects are produced if the temperature becomes sufficiently high, but in reality their formation depends on the post-inflationary dynamics of a symmetry-breaking scalar. We analyze the dynamics of a symmetry-breaking scalar field in the early universe within models that provide an effective negative mass term at the origin, and show that the symmetry can remain broken so that topological defects are never formed. In particular, we demonstrate that nonthermally produced particles (such as the Standard Model Higgs) during preheating can generate such an effective negative mass term, allowing the scalar field to follow a time-dependent minimum even in renormalizable models with a quartic coupling. We also discuss the implications of this result for the Peccei-Quinn scalar in axion models.

    hep-phastro-ph.COJHEP(2026)·1 citation
38. 38*

    High Reheating Temperature without Axion Domain Walls

    Shota Nakagawa🇨🇳 · Yuichiro Nakai🇨🇳 · Yu-Cheng Qiu🇨🇳 · Lingyun Wang🇨🇳 · Yaoduo Wang🇨🇳

    We investigate a cosmological scenario in which the Peccei-Quinn (PQ) symmetry remains broken in the entire history of the Universe, thereby avoiding the formation of axion strings and domain walls. Contrary to the conventional expectation, it is demonstrated that appropriately chosen scalar interactions are able to keep the PQ symmetry broken at arbitrarily high temperatures. We carefully examine the finite-temperature effective potential in a model with two PQ breaking scalar fields. The existence of flat directions plays a vital role in suppressing axion isocurvature perturbations during inflation by stabilizing a PQ field at a large field value. The viable parameter space consistent with theoretical and observational constraints is identified. Our scenario provides a minimal path for PQ symmetry breaking that addresses both the axion domain wall and isocurvature problems while permitting arbitrarily high reheating temperatures accommodating high-scale baryogenesis scenarios such as thermal leptogenesis.

    hep-phastro-ph.COhep-thPLB(2026)·5 citations
39. 39*

    Direct detection of electromagnetically interacting ultraheavy dark matter

    Jason Kumar🇺🇸 · Biprajit Mondal🇮🇳 · Girish Muralidhara🇮🇳 · Nirmal Raj🇮🇳

    At a level too faint for astronomy, particle dark matter may interact with Standard Model states via the photon. We derive limits from direct detection experiments on photon-mediated nuclear interactions up to operator dimension-6, viz., via a millicharge, charge radius, electric and magnetic dipole moment, and anapole moment, up to dark matter masses $\lesssim 10^{17}$ GeV, where detectors become flux-limited. We derive constraints for XENON1T, XENONnT, LZ, PANDAX-II, PANDAX-4T, DarkSide-50, DEAP-3600, PICO-60, and CDMS-II, and estimate future sensitivities for the multi-deca-tonne scale experiments DarkSide-20k, DARWIN/XLZD, PANDAX-xT, and Argo. Special attention is paid to millicharged dark matter, for which we constrain new parameter space by deriving the ceiling on sensitivity to its electric charge, arising from the nuclear-vs-electron recoil discriminants used in liquid argon and bubble chamber detectors. This result goes beyond ceilings previously identified in liquid xenon and semiconductor detectors from electron recoil vetoes. In particular, the ceiling from PICO-60 closes a large window between direct detection and neutrino experiment limits for dark matter masses below $10^{12}$ GeV.

    hep-phJHEP(2026)·2 citations
40. 40*

    Vector dark matter production during inflation in the gradient-expansion formalism

    A.V. Lysenko🇺🇦 · O.O. Sobol🇩🇪 · S.I. Vilchinskii🇺🇦

    A massive vector field is a highly promising candidate for dark matter in the Universe. A salient property of dark matter is its negligible or null coupling to ordinary matter, with the exception of gravitational interaction. This poses a significant challenge in producing the requisite amount of dark particles through processes within the Standard Model. In this study, we examine the production of a vector field during inflation due to its direct interaction with the inflaton field through kinetic and axionlike couplings as well as the field-dependent mass. The gradient-expansion formalism, previously proposed for massless Abelian gauge fields, is extended to include the longitudinal polarization of a massive vector field. We derive a coupled system of equations of motion for a set of bilinear functions of the vector field. This enables us to address the nonlinear dynamics of inflationary vector field production, including backreaction on background evolution. To illustrate this point, we apply our general formalism to a low-mass vector field whose kinetic and mass terms are coupled to the inflaton via the Ratra-type exponential function. The present study investigates the production of its transverse and longitudinal polarization components in a benchmark inflationary model with a quadratic inflaton potential. It has been demonstrated that pure mass coupling is able to enhance only the longitudinal components. By turning on also the kinetic coupling, one can get different scenarios. As the coupling function decreases, the primary contribution to the energy density is derived from the transverse polarizations of the vector field. Conversely, for an increasing coupling function, the longitudinal component becomes increasingly significant and rapidly propels the system into the strong backreaction regime.

    hep-phastro-ph.COPRD(2026)·4 citations
41. 41*

    Reply to "There is no 690 GeV resonance"

    M. Consoli🇮🇹 · L. Cosmai🇮🇹 · F. Fabbri🇮🇹 · G. Rupp🇵🇹

    A recent paper has criticised the idea that, beside the resonance of mass $m_h=125$ GeV, the Higgs field might exhibit a relatively narrow, second resonance with a mass $M_H\sim 690$ GeV. Without considering the evidence we have provided, the criticism also concerned our claim that experimental signals for this new resonance might already be seen in some LHC data. Since our extensive work is covered by several papers, we will summarise here the whole issue, namely: i) the theoretical motivations for a two-mass structure in cutoff ${\Phi }^4$ theory; ii) the checks from lattice simulations and the prediction $(M_H{)}^{\mathrm{Theor}}=690(30)$ GeV; iii) the present experimental indications of a new, relatively narrow resonance in the expected mass range. This compact presentation will thus give the elements to objectively judge on a relevant question of present-day particle physics.

    hep-ph1 citation
42. 42*

    New insights from the flavor dependence of quark transverse momentum distributions in the pion

    Lorenzo Rossi🇮🇹 · Alessandro Bacchetta🇮🇹 · Matteo Cerutti🇫🇷 · Marco Radici🇮🇹

    We update our previous extraction of transverse momentum distributions of unpolarized quarks in the pion by implementing a more comprehensive description of theoretical uncertainties and, for the first time, by exploring possible differences among quark flavors. We extract such distributions from all available data for unpolarized pion-nucleus Drell-Yan processes, where the cross section is differential in the transverse momentum of the final lepton pair. The cross section involves transverse momentum distributions in the nucleon, that we consistently take from our previous studies.

    hep-phhep-exnucl-exnucl-thPLB(2026)·7 citations
43. 43*

    Fast, accurate, and precise detector simulation with vision transformers

    Luigi Favaro🇧🇪 · Andrea Giammanco🇧🇪 · Claudius Krause🇦🇹

    The speed and fidelity of detector simulations in particle physics pose compelling questions about LHC analysis and future colliders. The sparse high-dimensional data, combined with the required precision, provide a challenging task for modern generative networks. We present a comparison between solutions with different trade-offs, including accurate Conditional Flow Matching and faster coupling-based Normalising Flows. Vision Transformers allows us to emulate the energy deposition from detailed Geant4 simulations. We evaluate the networks using high-level observables, neural network classifiers, and sampling timings, showing minimum deviations from Geant4 while achieving faster generation. We use the CaloChallenge benchmark datasets for reproducibility and further development.

    hep-phhep-ex6 citations
44. 44*

    $\varphi$-Dwarfs: White Dwarfs probe Quadratically Coupled Scalars

    Kai Bartnick🇩🇪 · Konstantin Springmann🇮🇱 · Stefan Stelzl🇨🇭 · Andreas Weiler🇩🇪

    We study ultralight scalar fields with quadratic couplings to Standard-Model fermions and derive strong constraints from white-dwarf mass-radius data. Such couplings source scalar profiles inside compact stars, shift fermion masses, and can produce a new ground state of matter. We analyze couplings to electrons and to nucleons, incorporating composition and finite-temperature effects in white dwarf structure and equations of state. We identify two robust observables: (i) forbidden gaps - ranges of radii with no stable configurations - and (ii) characteristic shape distortions that drive white dwarf masses toward the Chandrasekhar limit (electron couplings) or shift the maximum mass (nucleon couplings). Confronting these predictions with precise measurements for Sirius B and Procyon B, together with the global white dwarf population, excludes large regions of unexplored parameter space and extends earlier QCD-axion-specific bounds to a broader class of scalar theories. Our stellar constraints rely only on sourcing and do not assume the scalar constitutes dark matter; where mass reductions are small, precision laboratory searches remain competitive. White-dwarf astrophysics thus provides a powerful, largely assumption-minimal probe of ultralight, quadratically coupled scalars.

    hep-phastro-ph.HEastro-ph.SRJHEP(2026)·17 citations
45. 45*

    Thermal Damping of Neutrino-Coupled Scalar Dark Matter

    Abhishek Banerjee🇺🇸 · Ngan H. Nguyen🇺🇸 · Erwin H. Tanin🇺🇸

    We point out that ultralight scalar dark matter that modulates neutrino masses can be significantly thermal damped by cosmic neutrinos in the early universe. This dissipative effect arises as a backreaction from the neutrinos which are being driven slightly out of thermal equilibrium by the scalar. We estimate the rate of such thermal damping and explore its phenomenological implications. For a scalar that is produced early, we find that the effect of thermal damping results in a predictable final abundance largely insensitive to its initial condition while circumventing late time limits. This motivates a parameter-space line to target experimentally.

    hep-phastro-ph.COgr-qc5 citations
46. 46*

    Direct Collapse Black Hole Candidates from Decaying Dark Matter

    Yash Aggarwal🇺🇸 · James B. Dent🇺🇸 · Philip Tanedo🇺🇸 · Tao Xu🇺🇸

    Injecting 1-13.6 eV photons into the early universe can suppress the molecular hydrogen abundance and alter the star formation history dramatically enough to produce direct collapse black holes. These, in turn, could explain the recently observed population of puzzling high-redshift supermassive black holes that appear to require super-Eddington accretion. We show that axion dark matter decay in the intergalactic medium can account for this energy injection. We use a single zone model of the gas core and semi-analytically evolve its chemo-thermal properties to track the conditions for which the system becomes an atomic cooling halo-a necessary precursor for the production of heavy black hole seeds to explain the high-redshift black hole population. Windows of axions masses between 24.5-26.5 eV with photon couplings as low as $4\times 10^{-12}$/GeV may realize this atomic cooling halo condition. We highlight the significance of the band structure of molecular hydrogen on the effectiveness of this process and discuss estimates of the heavy seed population and prospects for testing this model.

    hep-phastro-ph.COJCAP(2026)·4 citations
47. 47*

    CP-conserving SO(3) parameterization of the neutrino mixing matrix

    Jarosław Duda🇵🇱 · Janusz Gluza🇵🇱 · Biswajit Karmakar🇵🇱

    The pattern of neutrino mixing, usually parameterized by the Pontecorvo-Maki-Nakagawa-Sakata $U_{\mathrm{PMNS}}$ matrix, still remains a striking puzzle in particle physics. $U_{\mathrm{PMNS}}$ is one of six possible products of multiplying three Euler matrices. Here we discuss the neutrino mixing matrix parameterization for three known flavours of neutrinos based on the SO(3) group represented by one three-dimensional rotation matrix $U_{SO3}$ and the CP-conserving phases ${\delta }_{\mathrm{CP}}=0^{\circ }$ and $180^{\circ }$. The mixing matrix $U_{SO3}$ with cyclic order of the Lie group generators implies ${\delta }_{\mathrm{CP}}=180^{\circ }$ for clockwise rotation in three dimensions, a viable scenario for normal mass ordering. We determine a range of rotation angles for $U_{SO3}$ which deviate substantially from the almost maximal mixings in the standard $U_{\mathrm{PMNS}}$ scenario, yielding `democratic' values for the mixing angles. On the other hand, ${\delta }_{\mathrm{CP}}=0^{\circ }$ CP-conserving case supports near-maximal mixing scenario. With the fixed ${\delta }_{\mathrm{CP}}$ value, the $U_{SO3}$ parameterization can be validated or falsified by the next generation of neutrinoless double beta decay experiments and puts a stringent constraint on the absolute neutrino mass. The proposed $U_{SO3}$ neutrino mixing parameterization is suited for independent CP-conserving neutrino oscillation experimental analysis.

    hep-phPLB(2026)·0 citations
48. 48*

    Steady state of fast-oscillating neutrinos in an inhomogeneous medium

    Manuel Goimil-García🇩🇰 · Irene Tamborra🇩🇰

    The streaming of neutrinos in an inhomogeneous medium is known to affect the physics of flavor conversion. We employ an ensemble of single-crossed angular distributions and explore the physics of flavor conversion, while neutrinos propagate across a one-dimensional inhomogeneous medium. The advective term in the neutrino equations of motion is responsible for the cascade of flavor waves towards ever smaller spatial and angular scales. However, as the system evolves, perturbations with large wavenumbers are damped, with a resulting smearing of the flavor configuration. We provide a simple recipe that allows to forecast the steady-state flavor configuration achieved by neutrinos without solving their kinetic equations. In particular, we find that flavor equipartition on one side of the angular spectrum and the cancellation of the spectral crossing in the lepton number distributions, proposed in the literature as generic flavor outcome, is a special solution depending on the degree of neutrino-antineutrino asymmetry. This work constitutes a step forward towards the development of semi-analytic schemes to account for flavor conversion physics in hydrodynamic simulations of core-collapse supernovae and neutron-star merger remnants.

    ↳ astro-ph.HEhep-phPRD(2025)·11 citations
49. 49*

    Regularized Lednicky-Lyuboshitz formula for higher partial waves in femtoscopy

    Koichi Murase🇯🇵 · Tetsuo Hyodo🇯🇵

    Femtoscopy is one of the promising experimental approaches to put constraints on interactions between various species of hadrons from the momentum correlation functions measured in high-energy nuclear collision experiments. The Koonin-Pratt and Lednicky-Lyuboshitz formulae provide useful expressions of the correlation functions and have been widely used to analyze the experimental data based on the assumption that the effect of higher partial waves is negligible. Those formulae can be generalized for higher partial waves, but the generalized Lednicky-Lyuboshitz formula produces wrong results due to a singular behavior of the asymptotic wave function at the origin. In this study, we attempt to solve the problem by regularizing the generalized Lednicky-Lyuboshitz formula with a cutoff and validate it using the Koonin-Pratt formula as a reference. We also show the relationship between the cutoff in the regularized Lednicky-Lyuboshitz and the effective-range correction in the original Lednicky-Lyuboshitz formula. Using the obtained formula, we investigate the source-size dependence, the validity of the effective range expansion, and the cutoff dependence of the correlation function. We also discuss the interaction dependence using the heatmap as a function of the scattering-length parameter $1/a_l$ and the momentum $q$.

    ↳ nucl-thhep-ph3 citations
50. 50*

    Exploring parameter dependence of heavy-flavor dynamics in small collision systems

    Grace Pang🇺🇸

    Observations from high-multiplicity proton-lead ($p$-Pb) collisions indicate that small systems may exhibit collective behavior in both heavy and light hadrons. This work investigates the roles of initial- and final-state interactions in shaping the nuclear modification factor and elliptic flow of $D$ mesons measured in $p$-Pb collisions. Initial-state effects, including the Cronin and shadowing effects, are considered in the heavy-quark initial conditions, while final-state interactions are simulated through Langevin evolution combined with the coalescence model of hadronization. Different initial geometries attributed to fluctuations in the medium's energy density are parametrized and translated into the momentum anisotropies of both light and heavy quarks. The corresponding $R_{pPb}$ and $v_2$ of D mesons in 8.16 TeV $p$-Pb collisions are calculated under different assumptions for the final-state interactions. Assuming that the initial-state effects only modify the transverse momentum spectra without altering the azimuthal distribution of heavy quarks, the measured $R_{pPb}$ of D mesons can be qualitatively reproduced by the combined influence of initial- and final-state effects. However, the observed $v_2$ cannot be accounted for by final-state interactions alone. These results suggest that additional contributions to azimuthal anisotropies of heavy quarks originating from initial-state effects are required to explain the experimentally observed $v_2$.

    ↳ nucl-thhep-phPRC(2025)·0 citations
51. 51*

    Constraining Inflationary Particle Production with CMB Polarization

    Luca H. Abu El-Haj🇺🇸 · Oliver H.E. Philcox🇺🇸 · J. Colin Hill🇺🇸

    Following Philcox et al. (2025), we investigate a scenario with a massive partner to the inflaton ($O(100)$ times the inflationary Hubble scale), in which particles are produced during a narrow time period, leaving characteristic hot- or cold-spots in the cosmic microwave background (CMB). Using tools developed for thermal Sunyaev-Zel'dovich cluster-finding, we search component-separated Planck PR4 $E$-mode maps for these hotspots, and compare to analogous results in $T$. Our analysis pipeline is validated on simulated observations and gives unbiased constraints for sufficiently large and bright hotspots. At Planck sensitivities, the temperature data are more sensitive to small hotspots, but for sufficiently large hotspots the polarization data are more sensitive. We improve upon earlier work by building a full Poissonian likelihood for the hotspot abundance. We find no strong evidence for primordial hotspots and thereby place novel bounds on the couplings between the inflaton and massive scalars during inflation, probing physics at energies many orders of magnitude above any feasible terrestrial collider. The bounds derived from our new likelihood improve upon those of Philcox et al. (2025) by more than an order of magnitude for sufficiently light particles ($M_0\lesssim 100H_I$). We also forecast the inferred bounds on inflationary physics for a search using Atacama Cosmology Telescope (ACT) data, and from an optimistic cosmic-variance-limited experiment (CV), for which $E$-mode data provide stronger constraints than $T$ on nearly all scales. ACT should improve on the Planck constraints by $\gtrsim 10\%$, nearing the CV limit allowed by its sky coverage. Finally, we compare the constraining power of localized searches to that of a power spectrum analysis, and demonstrate that for sufficiently few produced particles the localized search performed herein is dominant.

    ↳ astro-ph.COgr-qchep-phPRD(2026)·3 citations
52. 52*

    Vector Horndeski black holes in nonlinear electrodynamics

    Che-Yu Chen🇯🇵 · Antonio De Felice🇯🇵 · Shinji Tsujikawa🇯🇵 · Taishi Sano🇯🇵

    On a spherically symmetric and static background, we study the existence of linearly stable black hole (BH) solutions in nonlinear electrodynamics (NED) with a Horndeski vector-tensor (HVT) coupling, with and without curvature singularities at the center ($r=0$). Incorporating the electric charge $q_E$ and the magnetic charge $q_M$, we first show that nonsingular BHs can exist only if $q_M=0$. We then study the stability of purely electric BHs by analyzing the behavior of perturbations in the metric and the vector field. Nonsingular electric BHs are unstable due to a Laplacian instability in the vector perturbation near the regular center. In the absence of the HVT coupling ($\beta =0$), singular BHs in power-law NED theories can be consistent with all linear stability conditions, while Born-Infeld BHs encounter strong coupling due to a vanishing propagation speed as $r\to 0$. In power-law NED and Born-Infeld theories with $\beta \ne 0$, the electric fields for singular BHs are regular near $r=0$, while the metric functions behave as $\propto r^{-1}$. Nevertheless, we show that Laplacian instabilities occur for regions inside the outer horizon $r_h$, unless the HVT coupling constant $\beta$ is significantly smaller than $r_h^2$. For $\beta \ne 0$, we also reconstruct the NED Lagrangian so that one of the metric functions takes the Reissner-Nordström form. In this case, there exists a branch where all squared propagation speeds are positive, but the ghost and strong coupling problems are present around the BH center. Thus, the dominance of the HVT coupling generally leads to BH instability in the high-curvature regime.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2026)·7 citations
53. 53*

    Emergence of General Relativity from Cosmological Constant Via Ghost Condensation

    Ichiro Oda🇯🇵

    We show that starting with a cosmological constant in a curved space-time, the Einstein-Hilbert term of general relativity is generated through a ghost condensation. We fix Weyl symmetry, or equivalently local scale symmetry by a gauge condition $R=0$ à la BRST formalism, and see that the condensation of the Faddeev-Popov ghosts, $⟨\bar{c}c⟩\ne 0$ leads to a generation of the Einstein-Hilbert action of general relativity. This dynamical mechanism of symmetry breakdown for a global scale symmetry is new in the sense that the reduction of fermionic degrees of freedom effectively leads to a generation of bosonic degrees of freedom. We also discuss this mechanism from the viewpoint of the problem of a bound state, and show that asymptotic fields corresponding to the bound states are ``confined'' to the unphysical Hilbert space.

    ↳ hep-thgr-qchep-phMod.Phys.Lett.A(2026)·1 citation
54. 54*

    Quantum Resonance Beyond Direct Measurement: Insights from Weak Measurement

    Daiki Ueda🇮🇱 · Izumi Tsutsui

    Aharonov's weak value amplification realized via weak measurement provides a versatile means to measure physical parameters with high accuracy, similar to quantum resonance epitomized by the Rabi and Ramsey resonances. The similarity between the two is not accidental: in fact, these two methods of precision measurement have recently been shown to be interconnected for the particular case of direct weak measurement. Here we show that this connection also holds in the case of indirect weak measurement, which is the standard scheme used mostly for studies of weak value amplification. We present a unified framework of weak measurements in which direct measurement appears as a special case of indirect measurement. This allows us to compare the measurement precision of different methods on a common basis, as demonstrated explicitly for the Rabi and Ramsey resonances, showing how the precision of the latter surpasses that of the former in the context of weak value amplification.

    ↳ quant-phhep-exhep-phhep-th0 citations
55. 55*

    Prospect on constraining environment-dependent dilaton model from gravitational redshift measurements

    Li Hu🇨🇳 · Rong-Gen Cai🇨🇳 · Song He🇨🇳 · Li-Fang Li🇨🇳 · Tong Liu🇨🇳 · Peng Xu🇨🇳 · Shao-Jiang Wang🇨🇳

    Scalar-tensor gravity represents a natural extension of general relativity. This paper investigates a conformal scalar-tensor gravity, the environmentally dependent dilaton model, and identifies regions of its parameter space potentially constrained by future experiments using atomic clocks to measure gravitational redshift. We propose an experimental scheme in which atomic clocks are placed in environments of different mass densities, such as ultrahigh vacuum, water, or osmium, and their frequency shifts are compared to probe the scalar field contribution to gravitational redshift. By further modeling the mass distribution in low-density environments with a discrete representation, we go beyond the standard continuous approximation. Despite limitations inherent to specific experimental configurations, our analysis reveals that a significant portion of the parameter space remains accessible. Importantly, the accessible regions are complementary to those constrained by existing tests, as they are primarily sensitive to relatively weak couplings. Consequently, high-precision gravitational redshift experiments hold the potential to exclude significant regions of this parameter space in the future.

    ↳ gr-qchep-ph2 citations
56. 56*

    A lattice QCD study of low-energy interactions of doubly charmed baryons

    Jing-Yu Yi🇨🇳 · Ze-Rui Liang🇨🇳 · Liuming Liu🇨🇳 · De-Liang Yao🇨🇳

    We present a lattice QCD calculation of the S-wave interactions between the spin-1/2 doubly charmed baryons (${\Xi }_{cc},{\Omega }_{cc}$) and Goldstone bosons ($\pi ,K,\bar{K}$) using the $N_f=2+1$ CLQCD ensembles with lattice spacing $a=0.07746$ fm and two pion masses $M_{\pi }\simeq 210$ and 300 MeV. Four single-channel interactions, $I=1/2$ ${\Omega }_{cc}\bar{K}$, $I=1$ ${\Xi }_{cc}K$, $I=0$ ${\Xi }_{cc}K$ and $I=3/2$ ${\Xi }_{cc}\pi$, are investigated, since they are free of disconnected diagrams. Lüscher's finite volume method is utilized to extract the scattering parameters in the effective range expansion, i.e., the scattering lengths and effective ranges, from the finite-volume spectra. Our obtained results agree well with previous baryon chiral perturbation theory predictions.

    ↳ hep-lathep-phPoS(2026)·0 citations
57. 57*

    Finite-volume formalism for $N\pi \pi$ at maximal isospin

    Maxwell T. Hansen🇬🇧 · Fernando Romero-López🇨🇭 · Stephen R. Sharpe🇺🇸

    We extend the relativistic field theoretic finite-volume formalism to $N\pi \pi$ scattering states at maximal isospin, $I=5/2$. As in previous work using the relativistic field theory approach, we work to all orders in a generic low-energy effective theory, and determine the quantization condition that relates finite-volume energies to intermediate K matrices, and the integral equations connecting the latter to the physical scattering amplitudes. We discuss the parametrization of the K matrices, and explain in detail the new features that arise in implementing the quantization condition due to the spin of the nucleon in combination with the use of non-degenerate particles. As a concrete example, we provide a sample numerical application including the $\Delta$ resonance in the $N\pi$ subchannel. The extension to the $I=3/2$ and $1/2$ channels is more involved, due to mixing with $N\pi$ states, and we do not provide a complete formalism for these cases. We explain why $N\pi$ states cannot be included by treating the nucleon as a pole in $p$-wave $N\pi$ scattering, an approach that has been successful in studying $D{D}^{\ast }$ scattering using the three-particle $DD\pi$ formalism. We additionally provide results for all isospins under the assumption of no two-to-three mixing, thereby laying the groundwork for a follow-up paper in which all $N\pi \pi \leftrightarrow N\pi$ systems are fully treated. Finally, we study the singularities in $N\pi \pi$ amplitudes arising from $N\pi \pi \pi$ intermediate states, and find that our subthreshold cutoff functions must be modified to avoid such singularities.

    ↳ hep-lathep-phnucl-thJHEP(2026)·12 citations
58. 58*

    Gravitational waves from axion inflation in the gradient expansion formalism. Part II. Fermionic axion inflation

    Richard von Eckardstein🇩🇪 · Kai Schmitz🇩🇪 · Oleksandr Sobol🇩🇪

    Axion inflation represents an intriguing source of gravitational waves (GWs) from the early Universe. In a companion paper, arXiv:2508.00798, we previously leveraged the gradient expansion formalism (GEF) to investigate pure axion inflation (PAI), i.e., axion inflaton coupled to a pure gauge sector. In this paper, we extend our analysis to fermionic axion inflation (FAI), i.e., we allow for the presence of fermions in the gauge sector. PAI predicts a strongly blue-tilted GW spectrum; in our GEF benchmark study, all parameter regions leading to observable GWs turned out to violate the upper limit on the number of extra relativistic degrees of freedom, $\Delta N_{\mathrm{eff}}$. As we demonstrate in this paper, the situation is different for FAI: Schwinger pair creation of the charged fermions results in a damping of gauge-field production, which attenuates the GW signal. As a result, the GW signal from FAI can fall into the sensitivity reach of LISA and ET without violating the upper limit on $\Delta N_{\mathrm{eff}}$. This result notably applies to the arguably most realistic variant of Abelian axion inflation, in which the axion couples to the hypercharge sector of the Standard Model. Besides, we discuss GW emission from the fermion gas, which may further enhance the total GW signal but which also requires a more quantitative investigation in future work. Additionally, we identify a new backreaction regime in which fermion production moderates the axion--vector dynamics. In this regime, the axion velocity and all energy-density components exhibit oscillations analogous to the strong backreaction in PAI, but here, the oscillations occur around the slow-roll trajectory and are damped by the presence of charged fermions. These observations define again an interesting GEF benchmark for future lattice studies.

    ↳ astro-ph.COgr-qchep-phJHEP(2026)·5 citations
59. 59*

    Extended mass distribution of PBHs during QCD phase transition: SGWB and mini-EMRIs

    Nilanjandev Bhaumik🇨🇳 · Huai-Ke Guo🇨🇳 · Si-Jiang Liu🇨🇳

    Primordial black holes (PBHs) are one of the most important tracers of cosmic history. In this work, we investigate the formation of PBHs around the time of the QCD phase transition from a broadly peaked inflationary scalar power spectrum, which naturally produces an extended PBH mass function. This scenario yields two distinct stochastic gravitational wave backgrounds (SGWB): (i) scalar-induced, second-order tensor perturbations generated at PBH formation, and (ii) a merger-driven SGWB from the subsequent PBH binary population. Using Bayesian analysis, we examine both SGWB channels with the data from the NANOGrav 15-year dataset and the first three observing runs of LVK. We also forecast continuous-wave signals from mini extreme mass ratio inspirals (mini-EMRIs) for direct comparison with NANOGrav and LVK constraints. Our parameter scans identify regions of the parameter space where the combined SGWB is detectable in future ground-based and space-based detectors. A broad PBH mass distribution naturally gives rise to mini-EMRIs, which future ground-based observatories, such as LVK A+, ET, and CE, can detect. For a large part of the PBH parameter space, the SGWB of astrophysical origin masks the primordial SGWB in the frequency band of ground-based detectors. Thus, for extended PBH mass distributions, we find that the detection of mini-EMRIs is a more robust channel for probing the PBH parameter space than the corresponding SGWB.

    ↳ astro-ph.COgr-qchep-phPRD(2025)·6 citations
60. 60*

    Null matter and the ultrarelativistic origin of hydrodynamics at zero temperature

    Jay Armas🇳🇱 · Emil Have🇩🇰 · Gianbattista-Piero Nicosia🇳🇱

    We uncover a universal sector of relativistic fluid dynamics by taking a novel ultrarelativistic limit in which the temperature tends to zero while the flow simultaneously approaches the speed of light. In this regime, hydrodynamics becomes an effective theory of \emph{null matter}, characterised by a preferred null vector, a preferred scale, and their gradients. We show that this theory of null matter constitutes an example of a hydrodynamic theory that can be linearly stable and causal in an arbitrary choice of frame. The framework developed here for null matter can offer insights into ultrarelativistic heavy-ion collisions, astrophysical phenomena with inherently large Lorentz factors, and the dynamics of black hole horizons.

    ↳ hep-thastro-ph.HEgr-qchep-ph2 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.