Thu·May 8, 2025Thursday·May 8, 2025

1. 01*

   Pseudorapidity density, transverse momentum spectra, and elliptic flow studies in Xe-Xe collision systems at $\sqrt{{\mathrm{s}}_{\mathrm{NN}}}=5.44TeV$ using the HYDJET++ model

   Saraswati Pandey🇮🇳 · S.K. Tiwari🇮🇳 · B.K. Singh🇮🇳

   In this paper, we present a systematic study of Xe--Xe collisions at $\sqrt{s_{\mathrm{NN}}}=5.44$~TeV center-of-mass energy. We employ the Monte Carlo (hydrodynamics plus jets) HYDJET++ model to calculate the pseudorapidity distribution, transverse momentum ($p_{\mathrm{T}}$) spectra, and the elliptic flow ($v_2$) of charged hadrons with different parameters in two geometrical configurations: body-body and tip-tip types of Xe--Xe collisions. The kinematic ranges $0<p_{\mathrm{T}}<50\mathrm{GeV}/c$ and $|\eta |<0.8$ are considered in our study. Results are obtained for seven classes of centrality. For comparison, we have shown results from the AMPT model with the string-melting version. The results obtained for Xe--Xe collision systems for minimum bias at midrapidity match well with the experimental data from the ALICE and CMS Collaborations. We observe that the pseudorapidity density depends on the size and geometry of the colliding system. The centrality dependence of average transverse momentum ($⟨p_{\mathrm{T}}⟩$) and average elliptic flow ($⟨v_2⟩$) is also observed. The charged hadron properties also show clear dependence on the geometrical configuration of the collisions. Our model results have been compared to results obtained from the AMPT model. The HYDJET++ model matches the experimental data more closely than the AMPT model, which tends to overpredict the data.

   hep-phPRC(2021)·13 citations
2. 02*

   Higher-order anisotropic flow correlations in Xe-Xe collisions at $\sqrt{{\mathrm{s}}_{\mathrm{NN}}}=5.44TeV$

   Saraswati Pandey🇮🇳 · B. K. Singh🇮🇳

   By employing the Monte Carlo HYDJET++ model (HYDrodynamics plus JETs), we produce anisotropic harmonic flow coefficients $v_n$ ($n=4$-$7$) in deformed Xe-Xe collisions at $\sqrt{s_{NN}}=5.44\mathrm{TeV}$. These harmonics are measured with respect to a plane constructed using the lower-order Fourier harmonics $v_2$ and $v_3$, produced using the reaction plane method. The cross-talk between elliptic and triangular flows in the model generates both even and odd higher-order harmonics. By combining analyses of higher harmonics with those of $v_2$ and $v_3$, one can eliminate uncertainties in modeling anisotropic flow from initial conditions and define quantities that involve only nonlinear hydrodynamic response coefficients. In this context, we study the individual response of higher-order flow coefficients to the lower-order ones through a power-law scaling technique of the form $v_n/v_m^m$, as a function of collision centrality. We report that the higher-order flow coefficients $v_n$ ($n=4$-$7$) exhibit strong centrality dependence and are significantly correlated with the elliptic and triangular flow. The results are compared with data from recent ALICE, ATLAS, and CMS experiments at the LHC.

   hep-phEur.Phys.J.Plus(2024)·2 citations
3. 03*

   Constraints on Asymmetric Dark Matter Self Annihilation Cross Sections

   Qiquan Li🇨🇳 · Hoernisa Iminniyaz🇨🇳 · Fangyu Liu🇨🇳

   We investigate the evolution of the relic density for asymmetric dark matter incorporating self annihilation processes in both the shear-dominated universe and Gauss-Bonnet braneworld. Under the same conditions where the ratio of final asymmetry to the initial asymmetry $R\equiv {\Delta }_{-\infty }/{\Delta }_{\text{in}}$ is identical, the shear-dominated universe, due to its enhanced Hubble expansion rate, leads to an earlier freeze-out point of wash-out asymmetry process and allows a higher upper limit on the self annihilation cross section. Conversely, the Gauss-Bonnet braneworld, with a weakened Hubble expansion rate, delays the freeze-out point and permits a lower upper limit on the self annihilation cross section. We further constrain the wino mass $M_2$ for sneutrino and higgsino asymmetric dark matter in both scenarios, showing that, compared to the standard model, the lower limit of $M_2$ is smaller in the shear-dominated universe but higher in the Gauss-Bonnet braneworld.

   hep-phFortsch.Phys.(2025)·0 citations
4. 04*

   Study of $B\to \pi \rho$, $\pi \omega$ decays in the modified perturbative QCD approach

   Sheng Lü🇨🇳 · Mao-Zhi Yang🇨🇳

   We investigate the $B\to \pi \rho$ and $\pi \omega$ decay processes using the modified perturbative QCD (PQCD) approach. Sudakov factors arising from the resummation of the double logarithms for the contributions of the transverse momenta of partons can increase the applicability of perturbative calculations. In this work we find that infrared contributions cannot be fully suppressed by Sudakov factors alone when the $B$ meson wave function obtained by solving the wave equation in the QCD-inspired relativistic potential model is used in the calculation of $B$ decays. Therefore, it is necessary to introduce a soft cutoff scale ${\mu }_c$ to separate the hard and soft contributions. Color-octet contributions for the intermediate quark-antiquark pairs are considered. Such contributions are crucial to deminish the discrepancies between the theoretical calculation and experiemntal data. Using the isospin symmetry, we do find the optimal parameter space for the nonperturbative inputs, which can result in excellent agreement between the theoretical calculation and experimental data of $B\to \pi \rho$ and $B\to \pi \omega$ decays.

   hep-phEPJC(2025)·1 citation
5. 05*

   Neutrino-jet correlations in charged-current SIDIS

   Weihua Yang🇨🇳 · Jing Zhao🇨🇳 · Zhe Zhang🇨🇳

   Charged-current deep inelastic scattering plays a significant role in determining parton distribution functions with flavour separation.In this work, we present a systematic calculation of the charged-current semi-inclusive deep inelastic scattering (SIDIS) in the $eN$ collinear frame up to twist-3 level at leading order. Semi-inclusive refers to the process in which a jet is detected in addition to the scattered neutrino. We focus on neutrino-jet correlations in our calculation. We first present the differential cross section in terms of structure functions, followed by the differential cross section expressed in term of transverse momentum dependent parton distribution functions. We derive the complete set of azimuthal asymmetries and intrinsic asymmetries. We also introduce an observable $A^C$, defined as the ratio of the difference to the sum of differential cross sections for electron and positron semi-inclusive deep inelastic scattering.We notice that $A^C$ provides a sensitive probe for valence and sea quark distribution functions

   hep-phPRD(2025)·2 citations
6. 06*

   Role of ${\Sigma }^{\ast }(1/2^{-})$ baryons in ${\Lambda }_c\to \Lambda {\pi }^{+}{\pi }^{+}{\pi }^{-}$ decay

   Jun He🇨🇳

   Based on Belle data, the structure around 1435 MeV and the role of the $\Sigma (1380)$ resonance in the decay process ${\Lambda }_c\to \Lambda {\pi }^{-}{\pi }^{+}{\pi }^{+}$ are investigated. The $\Lambda {\pi }^{\pm }$ invariant mass spectra are approximately reproduced by the contribution from the $\Sigma (1385)$, modeled as a Breit-Wigner resonance combined with background. However, an additional contribution is required to account for the pronounced enhancement near 1435 MeV. To describe this structure, two scenarios are considered for the $\Sigma (1435)$: one as a Breit-Wigner resonance with spin-parity $1/2^{-}$ described via effective Lagrangians, and the other as a rescattering effect arising from coupled-channel interactions. Specifically, the channels ${\bar{K}}^{0}p$, ${\pi }^0{\Sigma }^{+}$, ${\pi }^{+}{\Sigma }^0$, ${\pi }^{+}\Lambda$, and $\eta {\Sigma }^{+}$ are included for the positively charged mode, and $K^{-}n$, ${\pi }^0{\Sigma }^{-}$, ${\pi }^{-}{\Sigma }^0$, ${\pi }^{-}\Lambda$, and $\eta {\Sigma }^{-}$ for the negatively charged mode. The rescattering contributions are evaluated using the quasipotential Bethe-Salpeter equation approach. Simulated invariant mass spectra are generated and fitted to the experimental data. Both the Breit-Wigner and rescattering mechanisms provide reasonable descriptions of the enhancement near 1435 MeV. The rescattering approach naturally generates a cusp-like structure near threshold, which closely resembles the feature observed in the data. Furthermore, the inclusion of the $\Sigma (1380)$ resonance with spin-parity $1/2^{-}$ significantly improves the fit in the low-energy region and further enhances the description near 1435 MeV through interference effects. These results underscore the essential roles of the two ${\Sigma }^{\ast }(1/2^{-})$ states in accurately describing the invariant mass distributions in the decay ${\Lambda }_c\to \Lambda {\pi }^{+}{\pi }^{+}{\pi }^{-}$.

   hep-phPRC(2025)·7 citations
7. 07*

   Exact parametrization of a minimal seesaw model

   Zi-Qiang Chen🇨🇳 · Xi-He Hu🇨🇳 · Ye-Ling Zhou🇨🇳

   We propose a parametrization of neutrino masses and mixing in the minimal seesaw model (MSM). The MSM, which introduces two heavy sterile neutrinos, is the minimal extension of the Standard Model in addressing the tiny masses of active neutrinos. The parametrization includes 11 free parameters: 6 neutrino oscillation parameters (2 mass-squared differences $\Delta m_{21}^2$, $\Delta m_{31}^2$, 3 mixing angles ${\theta }_{12}$, ${\theta }_{13}$, ${\theta }_{23}$, and 1 Dirac phase ${\delta }_{\mathrm{CP}}$), 1 mass parameter in $0\nu 2\beta$ decay $m_{ee}$, and 4 additional parameters: 2 heavy neutrino masses $M_1$ and $M_2$, 1 active-sterile mixing angle ${\theta }_{14}$ and 1 CP-violating phase ${\delta }_{14}$. This parametrization is derived exactly from the most general neutrino mass matrix in the MSM without any approximation. We further discuss its implications in phenomenological studies.

   hep-phPRD(2025)·3 citations
8. 08*

   Examining scalar portal inelastic dark matter with lepton fixed target experiments

   I. V. Voronchikhin🇷🇺 · D. V. Kirpichnikov🇷🇺

   Inelastic dark matter scenarios have attracted considerable attention in contemporary particle physics. In this study, we investigate the phenomenology of sub-GeV inelastic dark matter interacting via a lepton-specific scalar portal. By solving the Boltzmann equations, we obtain thermal target curves for several inelastic DM mass splittings in the sub-GeV mediator-mass range. We study the discovery potential of lepton fixed-target experiments, particularly NA64e, LDMX, and NA64$\mu$, via their missing-energy signatures. Our analysis focuses on the $\varphi$-strahlung process, $lN\to lN\varphi$, followed by the invisible decay of the scalar mediator into Majorana dark matter particles $\varphi \to {\chi }_1{\chi }_2$. We use this channel to probe the mediator coupling to charged leptons of the Standard Model. For phenomenologically viable parameters of the inelastic dark matter scenario, we derive projected sensitivities for NA64e, LDMX, and NA64$\mu$, assuming that the boosted state ${\chi }_2$ decays visibly via ${\chi }_2\to {\chi }_1{e}^{+}{e}^{-}$ outside the detector acceptance. Our results demonstrate the complementary roles of electron- and muon-beam experiments in exploring the sub-GeV inelastic dark matter sector interacting via a scalar portal.

   hep-phPRD(2026)·9 citations
9. 09*

   Probing millicharged particles with NA64$\mu$ and LDMX

   Sergei N. Gninenko🇷🇺 · N. V. Krasnikov🇷🇺 · Sergey Kuleshov🇨🇱 · Valery E. Lyubovitskij🇨🇱 · P. Crivelli🇨🇭 · D. V. Kirpichnikov🇷🇺 · L. Molina Bueno🇪🇸 · Alexey S. Zhevlakov🇷🇺 · H. Sieber🇨🇭 · I. V. Voronchikhin🇷🇺

   Millicharged particles emerge as compelling candidates in numerous theoretically well-motivated extensions of the Standard Model. These hypothetical particles, characterized by an electric charge that is a small fraction of the elementary charge, have attracted significant attention in contemporary experimental physics. Their potential existence motivates dedicated search strategies across multiple experimental platforms, leveraging their distinctive electromagnetic interactions while evading conventional detection methods. In the present paper we estimated the projected sensitivity of fixed-target experiments, specifically NA64$\mu$ and LDMX, to the parameter space of millicharged particles. For the NA64$\mu$ experiment, with an anticipated muon flux of $\text{mbox}MOT\lesssim 10^{14}$, our analysis reveals a detectable mass window of $10\text{mbox}MeV\lesssim m_{\chi }\lesssim 150\text{mbox}MeV$ and charge parameter range $10^{-4}\lesssim ϵ\lesssim 7\times 10^{-4}$. This sensitivity arises from the bremsstrahlung-like missing energy signature $\mu N\to \mu N{\gamma }^{\ast }(\to \chi \bar{\chi })$. Furthermore, we evaluate the discovery potential of the LDMX facility, considering its projected electron beam statistics, $\text{mbox}EOT\lesssim 2\times 10^{16}$, and energy, $E_{\mathrm{e}}\simeq 8\text{mbox}GeV$. Our results demonstrate that LDMX can probe heavier MCPs in the mass range $250\text{mbox}MeV\lesssim m_{\chi }\lesssim 400\text{mbox}MeV$, with sensitivities reaching $10^{-3}\lesssim ϵ\lesssim 1.5\times 10^{-3}$. This parametric window can be accessible through the distinctive invisible decay channel $\rho \to \chi \bar{\chi }$, where $\rho$-meson photo-production $\gamma N\to N\rho$ plays a pivotal role.

   hep-phEPJC(2026)·7 citations
10. 10*

    The ratio of $\gamma /{\pi }^0$ production rates in neutrino-nucleus interactions at the $\Delta$ resonance mass region

    Ara N. Ioannisian🇦🇲

    We study the dependence of neutrino-induced $\gamma /{\pi }^0$ production ($\stackrel{(-)}{{\nu }_{\mu }}+A\to \stackrel{(-)}{{\nu }_{\mu }}(\mu )+\gamma /{\pi }^0+X$) on the target nucleus A, at the $\Delta$ resonance mass region. Our conclusion is based on experimental data for ${\pi }^0$ production rates at photon-nucleus interactions from the A2 collaboration at the Mainz MAMI accelerator. We assume that $\Delta$ resonance decays are independent of the production mechanism (via photon, Z, or W boson). In Neutral Current (NC) interactions, the $1{\pi }^0+X$ production scales as A${}^{2/3}$. In contrast, photons from $\Delta$ decays typically escape the nucleus, resulting in a cross-section proportional to the atomic number A. Thus, in NC interactions, the ratio of $\gamma$ production to ${\pi }^0$ production is proportional to A${}^{1/3}$. In Charged Current (CC) ${\nu }_{\mu }$(${\bar{\nu }}_{\mu }$) -induced production of ${\Delta }^{+}$ (${\Delta }^0$) will be proportional to the number of neutrons (protons) in the nucleus. After $\Delta$ decay, due to the charge universality in strong interactions, the suppression factor for ${\pi }^0$ escaping the nucleus must also follow A${}^{-1/3}$, as in NC interactions. We predict the ratio of the $\gamma /{\pi }^0$ production rates in NC and CC interactions and for ${\nu }_{\mu }$ and ${\bar{\nu }}_{\mu }$ beams: {Argon target}: $\sim$3.1\% (NC/CC ${\nu }_{\mu }/{\bar{\nu }}_{\mu }$). {\bf Water target}: $\sim$1.9\% (NC), $\sim$2.3\% (CC ${\nu }_{\mu }$), $\sim$1.7\% (CC ${\bar{\nu }}_{\mu }$). {Liquid Scintillator target}: $\sim$1.7\% (NC), $\sim$2.1\% (CC ${\nu }_{\mu }$), $\sim$1.6\% (CC ${\bar{\nu }}_{\mu }$). We also discuss solving the MiniBooNE anomaly by looking at the CC single photon and single neutral pion production rates at the SBN program experiments at Fermilab.

    hep-phPRD(2025)·3 citations
11. 11*

    Next-to-leading-order QCD corrections to double prompt $J/\psi$ hadroproduction

    Zhi-Guo He🇨🇳 · Xiao-Bo Jin🇨🇳 · Bernd A. Kniehl🇩🇪

    Within the framework of nonrelativistic-QCD (NRQCD) factorization, we perform a comprehensive investigation of the color singlet (CS) contribution to prompt $J/\psi$ pair production at the CERN Large Hadron Collider at next-to-leading order (NLO) in ${\alpha }_s$. Specifically, we compare our NLO predictions with measurements from the LHCb, CMS, and ATLAS Collaborations. We find that the CS contribution itself can well describe the LHCb data in most of the experimental bins, except in the regions where the fixed-order calculation is spoiled by the emission of soft or hard-collinear gluons. In the CMS and ATLAS cases, however, the CS predictions greatly undershoot both the measured total and differential cross sections, despite sizable $K$ factors, of 2--3, for the total cross sections.

    hep-phPRD(2025)·3 citations
12. 12*

    Normal mode analysis within relativistic massive transport

    Xin Lin🇨🇳 · Qiu-Ze Sun🇨🇳 · Xin-Hui Wu🇨🇳 · Jin Hu🇨🇳

    In this paper, we address the normal mode analysis on the linearized Boltzmann equation for massive particles in the relaxation time approximation. One intriguing feature of massive transport is the coupling of the secular equations between the sound and heat channels. This coupling vanishes as the mass approaches zero. By utilizing the argument principle in complex analysis, we determine the existence condition for collective modes and find the onset transition behavior of collective modes previously observed in massless systems. We numerically determine the critical wavenumber for the existence of each mode under various values of the scaled mass. Within the range of scaled masses considered, the critical wavenumbers for the heat and shear channels decrease with increasing scaled mass, while that of the sound channel exhibits a non-monotonic dependence on the scaled mass. In addition, we analytically derive the dispersion relations for these collective modes in the long-wavelength limit. Notably, kinetic theory also incorporates collisionless dissipation effects, known as Landau damping. We find that the branch cut structure responsible for Landau damping differs significantly from the massless case: whereas the massless system features only two branch points, the massive system exhibits an infinite number of such points forming a continuous branch cut.

    hep-phcond-mat.stat-mechhep-thnucl-th+1PRD(2026)·2 citations
13. 13*

    Portal Matter Models of Kinetic Mixing with Two Light Dark Gauge Bosons

    Thomas G. Rizzo🇺🇸

    The kinetic mixing (KM) portal mandates the existence of at least one new gauge boson, the dark photon (DP) based on the group $U(1{)}_D$, which mixes with the Standard Model (SM) photon via loops of other new heavy particles carrying both SM and dark charges called portal matter (PM). Arguments exist based on the RGE running of the $U(1{)}_D$ gauge coupling suggesting that at higher scales $U(1{)}_D$ becomes part of a more complex non-Abelian group, a simple example being just the SM-like $G_D=SU(2{)}_I\times U(1{)}_{Y_I}$. In our past analyses it was always assumed that $G_D$ broke in a SM-like manner directly to the DP's $U(1{)}_D$ which then subsequently broke at low energies $\text{lsim}1$ GeV. However, this need not be the case and $G_D$ can instead break to $U(1{)}_{T_{3I}}\times U(1{)}_{Y_I}$, with $T_{3I}$ being the diagonal generator of $SU(2{)}_I$, now producing two light gauge bosons which obtain masses at the $\text{lsim}1$ GeV scale. In this paper we will explore the phenomenology of a very simple realization of this kind of alternative setup employing non-abelian KM and having a minimal, lepton-like PM sector, demonstrating its distinctive nature in comparison to the previously examined symmetry breaking path. The effects of interference between these gauge bosons on thermal dark matter annihilation, the production of new heavy gauge, Higgs and PM states at colliders, as well as the corresponding signatures for the light dark gauge bosons are examined.

    hep-phPRD(2025)·3 citations
14. 14*

    Hot Holographic 2-flavor Quark Star

    Le-Feng Chen🇨🇳 · Jing-Yi Wu🇨🇳 · Hao Feng🇨🇳 · Tian-Shun Chen🇨🇳 · Kilar Zhang🇨🇳

    Applying the holographic 2-flavor Einstein--Maxwell-dilaton model, the parameters of which are fixed by lattice QCD, we extract the equations of state for hot quark--gluon plasma around the critical point at T=182 MeV, and have corresponding quark star cores constructed. By further adding hadron shells, the mass range of the whole stars spans from 2 to 17 solar masses, with the maximum compactness around 0.22. This result allows them to be black hole mimickers and candidates for gap events. The I--Love--Q--C relations are also analyzed, which show consistency with the neutron star cases when the discontinuity at the quark--hadron interface is not large. Furthermore, we illustrate the full parameter maps of the energy density and pressure as functions of the temperature and chemical potential and discuss the constant thermal conductivity case supposing a heat source inside.

    hep-phastro-ph.HEgr-qchep-thUniverse(2025)·3 citations
15. 15*

    Deep Learning to Improve the Sensitivity of Higgs Pair Searches in the $4b$ Channel at the LHC

    Yongcheng Wu🇨🇳 · Liang Xiao🇨🇳 · Yan Zhang🇨🇳

    The Higgs self-coupling is crucial for understanding the structure of the scalar potential and the mechanism of electroweak symmetry breaking. In this work, utilizing deep neural network based on Particle Transformer that relies on attention mechanism, we present a comprehensive analysis of the measurement of the trilinear Higgs self-coupling through the Higgs pair production with subsequent decay into four $b$-quarks ($HH\to b\bar{b}b\bar{b}$) at the LHC. The model processes full event-level information as input, bypassing explicit jet pairing and can serves as an event classifier. At HL-LHC, our approach constrains the ${\kappa }_{\lambda }$ to $(-0.53,6.01)$ at 68\% CL achieving over 40\% improvement in precision over conventional cut-based analyses. Comparison against alternative machine learning architectures also shows the outstanding performance of the Transformer-based model, which is mainly due to its ability to capture the correlations in the high-dimensional collision data with the help of attention mechanism. The result highlights the potential of attention-based networks in collider phenomenology.

    hep-phCPC(2026)·5 citations
16. 16*

    Production of heavy quark bound states in rare exclusive decays of Higgs boson

    F. A. Martynenko🇷🇺 · A. P. Martynenko🇷🇺 · A. V. Eskin🇷🇺

    The processes of pair production of S- and P- wave charmonium, as well as the production of the tetraquark (cc \bar{c} \bar{c}) in the Higgs boson decays are investigated within the framework of relativistic quark model. Relativistic decay amplitudes are constructed and decay widths are calculated taking into account relativistic corrections both in the decay amplitude and in the wave function of bound heavy quarks.

    hep-ph2 citations
17. 17*

    SIDIS at small $x$ at next-to-leading order: transverse photon

    Tolga Altinoluk🇵🇱 · Filip Bergabo · Jamal Jalilian-Marian🇺🇸 · Cyrille Marquet🇫🇷 · Yu Shi🇫🇷

    We calculate the next-to-leading order corrections to single inclusive hadron production in deep inelastic scattering at small $x$ using the color glass condensate formalism, for the case when the exchanged photon is transversely polarized. We show all UV and soft divergences cancel while collinear and rapidity divergences result in scale evolution of quark-hadron fragmentation function and small-x evolution of dipole amplitudes, respectively.

    hep-phPRD(2025)·12 citations
18. 18*

    Assessing the Reconstruction of the Critical Line in the QCD Phase Diagram from Imaginary to Real Chemical Potential

    Fabrizio Murgana🇮🇹 · Marco Ruggieri🇮🇹

    We test a technique adopted in the lattice simulations framework, to reconstruct the chiral-phase boundary at real chemical potential, $\mu$, via extrapolation from imaginary $\mu$. We use a low-energy effective model, the Quark-Meson model, both in the mean-field approximation and within the Functional Renormalization Group, the latter in the Local Potential Approximation. The model provides results both for real and imaginary values of $\mu$, thus a direct comparison can be performed between the prediction of the model for real values of $\mu$ and the ones obtained via extrapolation from the results at imaginary $\mu$. We compute an effective convergence radius for the reconstruction technique, ${\mu }_{\mathrm{conv}}$, and find ${\mu }_{\mathrm{conv}}\approx 146$ MeV. This value sustains the validity of the reconstruction technique also for finite and moderate values of the chemical potential. On the other hand, within our model, ${\mu }_{\mathrm{conv}}$ is quite smaller then the value of $\mu$ where we find the actual critical endpoint. Near this point of the phase diagram, we find a discrepancy between the actual phase boundary and the one pbtained via extrapolatin of $\approx 150\%$. Therefore, our results show that the location of the critical endpoint obtained via reconstruction from imaginary $\mu$ should be considered with due caution

    hep-phhep-lathep-thPRD(2025)·2 citations
19. 19*

    Testing Thermal-Relic Dark Matter with a Dark Photon Mediator

    Gordan Krnjaic🇺🇸

    In light of recent DAMIC-M results, we present the status of thermal-relic dark matter $\chi$ coupled to a kinetically-mixed dark photon $A^{\prime }$. In the predictive "direct annihilation" regime, $m_{A^{\prime }}>m_{\chi }$, the relic abundance depends on the kinetic mixing parameter, and there is a minimum value compatible with thermal freeze out. Using only electron and nuclear recoil direct detection results, we find that for complex scalar dark matter, the direct-annihilation regime is now excluded for nearly all values of $m_{\chi }$; the only exception is the resonant annihilation regime where $m_{A^{\prime }}\approx 2m_{\chi }$. Direct annihilation relic targets for other representative models, including Majorana and Pseudo-Dirac candidates, remain viable across a wide range of model parameters, but will be tested with a combination of dedicated accelerator searches in the near future. In the opposite "secluded annihilation" regime, where $m_{\chi }>m_{A^{\prime }}$, this scenario is excluded by cosmic microwave background measurements for all $m_{\chi }\lesssim 30$ GeV. Similar conclusions in both the direct and secluded regimes hold for all anomaly-free vector mediators that couple to the first generation of electrically-charged Standard Model particles.

    hep-phastro-ph.COhep-exPRD(2026)·28 citations
20. 20*

    A Quantal Theory of Restoration of Strong CP Symmetry

    Nemanja Kaloper🇺🇸

    We propose a mechanism for relaxing a gauge theory CP violating phase in discrete steps to very small values. The idea is that the CP violating phase includes the magnetic dual of a $4$-form flux which can discharge by the nucleation of membranes. Inside the bubbles surrounded by the membranes, the total CP violating phase is reduced. When the bubbles are produced rapidly during radiation domination in the early universe, near the chiral symmetry breaking scale, they will collide and percolate, melting away into gauge theory radiation and dramatically relaxing CP violation.

    hep-phastro-ph.COgr-qchep-thPRD(2026)·11 citations
21. 21*

    Antinuclei from Primordial Black Holes

    Valentina De Romeri🇪🇸 · Fiorenza Donato🇮🇹 · David Maurin🇫🇷 · Lorenzo Stefanuto🇮🇹 · Agnese Tolino🇪🇸

    Light primordial black holes (PBHs) may have originated in the early Universe, and could contribute to the dark matter in the Universe. Their Hawking evaporation into particles could eventually lead to the production of antinuclei, which propagate and arrive at Earth as cosmic rays with a flux peaked at GeV energies. We revisit here the antiproton and antideuteron signatures from PBH evaporation, relying on a lognormal PBH mass distribution, state-of-the-art propagation models, and an improved coalescence model for fusion into antideuterons. Our predictions are then compared with AMS-02 data on the antiproton flux. We find that the AMS-02 antiproton data severely constrain the Galactic PBH density, setting bounds that depend significantly on the parameters of the lognormal mass distribution, and that are comparable to or slightly stronger than bounds set from diverse messengers. We also discuss prospects for future detection of antideuterons. Given the bounds from AMS-02 antiproton data, we predict that if antideuterons were to be measured by AMS-02 or GAPS, since the secondary contribution is subdominant, they would clearly be a signal of new physics, only part of which could, however, be explained by PBH evaporation.

    hep-phastro-ph.HEPRD(2025)·4 citations
22. 22*

    Improved cosmological limits on $Z^{\prime }$ models with light right-handed neutrinos

    Tim Herbermann🇩🇪 · Manfred Lindner🇩🇪

    We improve limits on $Z^{\prime }$ extensions of the Standard Model (SM) with light right-handed neutrinos. The presence of shared gauge interactions between the light right-handed neutrinos and other SM fermions allows for production of ${\nu }_R$ in the early Universe and we use the excess in the effective number of neutrino species $\Delta N_{\text{eff}}$ to place limits. Our benchmark model is a minimal gauged $U(1{)}_{B-L}$ that often arises as a building block in other models, and we discuss applicability to more general $U(1)$ extensions. We devise an improved Monte Carlo integration scheme convenient for implementation of generic integrated Boltzmann equations with minimal simplifying assumptions. We sketch our numerical implementation in detail for future reference. Using the new ACT DR6 limit $\Delta N_{\text{eff}}<0.17$, we improve constraints on the gauge coupling for $1\mathrm{GeV}<m_{Z^{\prime }}<100\mathrm{TeV}$ by orders of magnitude and find the strongest limits thus far, surpassing even current and future colliders, and explore the potential of future CMB experiments to test $U(1)$ extensions up to the GUT scale. We perform a detailed analysis of the robustness of cosmological limits within standard and non-standard thermal histories and find that a strong first order phase transition, early dark energy or early matter domination could dilute ${\nu }_R$ abundances beyond detection. We investigate the effect of reheating on ${\nu }_R$-genesis and provide results and prescriptions to apply our bounds to non-standard thermal histories. Limits are generically weakened for reheating $T_{\text{reh}}\ll m_{Z^{\prime }}$. Our results suggest that projected limits on $Z^{\prime }$ with Dirac neutrinos can only be accommodated for in non-standard thermal histories, thus limiting the options to include dark matter candidates or Dirac leptogenesis.

    hep-phastro-ph.COJCAP(2025)·7 citations
23. 23*

    Ultra-Relativistic Freeze-Out During Reheating

    Stephen E. Henrich🇺🇸 · Mathieu Gross🇫🇷 · Yann Mambrini🇫🇷 · Keith A. Olive🇺🇸

    We perform a thorough investigation of (ultra)relativistic freeze-out (UFO) during reheating. While the standard WIMP (non-relativistic freeze-out) and FIMP (freeze-in) paradigms have been explored in detail during the reheating epoch, UFO has not been systematically studied, despite the fact that it is operative in a broad region of parameter space. Although dark matter (DM) is ``hot" at the time of relativistic freeze-out, we show that it can easily undergo enough cooling by the time of structure formation to be compatible with $\Lambda$CDM. Unlike standard WIMP-like freeze-out, there can be significant out-of-equilibrium DM production after UFO, similar to the freeze-in mechanism. However, unlike freeze-in, UFO can accommodate much stronger couplings. The UFO parameter space consistent with ${\Omega }_{\chi }{h}^2=0.12$ is quite large, with DM masses spanning about 13 orders of magnitude ($10^{-7}\text{ GeV}\lesssim m_{\chi }\lesssim 10^6$ GeV), reheating temperatures spanning 17 orders of magnitude ($10^{-2}\text{ GeV}\lesssim T_{\mathrm{RH}}\lesssim 10^{15}\text{ GeV}$) and Beyond the Standard Model (BSM) effective interaction scales spanning 11 orders of magnitude ($10^3\text{ GeV}\lesssim \Lambda \lesssim 10^{14}\text{ GeV}$). Interestingly, the most suitable range of couplings for UFO lies precisely between the typical couplings for WIMPs and FIMPs, rendering UFO quite attractive from the standpoint of detection. Particle physics models that are easily amenable to UFO include heavy vector or scalar portal interactions, along with nonrenormalizable effective interactions. Finally, we show there is a distinction between UV UFO and IR UFO, where the relic abundance for the former is sensitive to the freeze-out temperature, while the abundance for the latter is sensitive to the DM mass and the reheating temperature but insensitive to the freeze-out temperature.

    hep-phastro-ph.COPRD(2025)·14 citations
24. 24*

    Perturbation theory for a systematic account of the bound-state motion

    Alexander N. Kvinikhidze🇬🇪 · Hagop Sazdjian🇫🇷 · Boris Blankleider🇦🇺

    We derive a perturbation theory (PT) for the Lorentz boost operator in the space of two-nucleon wave functions. The latter is expressed in terms of the nucleon-nucleon ($NN$) potentials, developed so far in great detail for their use in the $NN$ scattering studies. The PT is designed to take into account the boost relativistic corrections in a systematic way and, as such, it is the only missing part in the corresponding approaches developed up to now in the low-energy effective field theories.

    ↳ nucl-thhep-phPRC(2025)·0 citations
25. 25*

    Towards nucleon structure function moments and parton momentum fractions from lattice QCD

    K. U. Can🇦🇺 · R. Horsley🇬🇧 · P. E. L. Rakow🇬🇧 · G. Schierholz🇩🇪 · H. Stüben🇩🇪 · R. D. Young🇦🇺 · J. M. Zanotti🇦🇺

    We calculate the lowest even isovector moment of the $F_2$ structure function in $2+1$-flavour lattice QCD with varying quark masses corresponding to $m_{\pi }\approx [410,360,300]\mathrm{MeV}$, at a fixed volume of $V=48^3\times 96$ and coupling $\beta =5.65$ ($a=0.068(3)\mathrm{fm}$). We directly compute the physical Compton amplitude using the Feynman-Hellmann approach and extract moments of the physical structure function. We report on the quark-mass dependence of the lowest isovector moment and estimate its value at the physical quark-mass point with $\sim 10\%$ uncertainty at fixed $Q^2$. By analysing the $Q^2$ dependence of the moments at the $SU(3)$ symmetric point ($m_{\pi }\approx 410\mathrm{MeV}$), we separate the leading- and higher-twist contributions and estimate the parton momentum fraction, $⟨x{⟩}_{u-d}$, which agrees with existing results.

    ↳ hep-lathep-phPoS(2025)·0 citations
26. 26*

    Orders-of-magnitude improvement in precision spectroscopy of an inner-shell orbital clock transition in neutral ytterbium

    Taiki Ishiyama🇯🇵 · Koki Ono🇯🇵 · Hokuto Kawase🇯🇵 · Tetsushi Takano🇯🇵 · Reiji Asano🇯🇵 · Ayaki Sunaga🇭🇺 · Yasuhiro Yamamoto🇹🇼 · Minoru Tanaka🇯🇵 · Yoshiro Takahashi🇯🇵

    An inner-shell orbital clock transition ${}^1{S}_0\leftrightarrow 4f^{13}5d6s^2(J=2)$ in neutral ytterbium atoms has attracted much attention as a new optical frequency standard as well as a highly sensitive probe for several new physics phenomena, such as ultralight dark matter, violation of local Lorentz invariance, and a new Yukawa potential between electrons and neutrons. Here, we demonstrate almost two-orders-of-magnitude improvement in precision spectroscopy over the previous reports on this transition, achieved by trapping atoms in a three-dimensional magic-wavelength optical lattice. In particular, we successfully observe the coherent Rabi oscillation, the relaxation dynamics of the excited state and the interorbital Feshbach resonance. To highlight the high precision of our spectroscopy, we carry out precise isotope shift measurements between five stable bosonic isotopes well below 10 Hz uncertainties, successfully setting bounds for a hypothetical boson mediating a force between electrons and neutrons. These results open up the way for various new physics search experiments and a wide range of applications to quantum science with this clock transition.

    ↳ physics.atom-phhep-exhep-phnucl-exNature Photon.(2026)·4 citations
27. 27*

    Discontinuity Method for Evaluating Scattering Amplitudes within the Worldline Formalism

    Victor Miguel Banda Guzmán🇲🇽

    The worldline formalism offers an alternative framework to the standard diagrammatic approach in quantum field theory, grounded in first-quantized relativistic path integrals. Over recent decades, this formalism has attracted growing interest due to its potential applications and computational advantages. As a result, a collection of worldline master integrals has been derived within this approach. However, efficient mathematical tools for evaluating these integrals remain limited. Motivated by unitarity methods used in the conventional formalism of quantum field theory, this work proposes a novel framework for evaluating one-loop worldline master integrals, up to a rational function in the kinematical external invariants, through the computation of their discontinuities. Similarly to standard unitarity techniques, the method involves decomposing an $n$-point one loop amplitude in $D=4$ dimensions into a linear combination of tadpole, bubble, triangle, and box master integrals. The coefficients of this decomposition are rational functions of the external kinematic invariants. Each master integral exhibits a characteristic discontinuity with respect to a specific kinematic invariant. Consequently, the rational coefficients can be determined by directly computing the discontinuities of the corresponding worldline master integrals. In the three-point and four-point on-shell cases, this computation is particularly tractable, as the discontinuities involve Dirac delta functions arising from the Sokhotski-Plemelj formula, which simplify the resulting integrals. For the four-point on-shell case, a set of master formulas for the discontinuities is derived. The practical implementation of the proposed discontinuity method is demonstrated through several illustrative examples.

    ↳ hep-thhep-phJHEP(2025)·3 citations
28. 28*

    Jet Quenching in Heavy-Ion Collisions at RHIC and the LHC experiments

    Nihar Ranjan Sahoo🇮🇳

    Jet quenching serves as a key probes of the Quark-Gluon Plasma (QGP) in heavy-ion collisions. This proceedings presents recent results from RHIC and LHC on jet energy loss, acoplanarity, and the flavour and path-length dependence of Parton energy loss, providing critical constraints on QGP properties and theoretical models. Upcoming data taking campaigns at RHIC and the LHC will offer enhanced precision and extended kinematic reach to further advance our understanding of jet-medium interactions.

    ↳ nucl-exhep-exhep-phJ.Subatomic Part.Cosmol.(2026)·1 citation
29. 29*

    Warming up the Fibres

    Dibya Chakraborty🇮🇳 · Rudnei O. Ramos🇧🇷

    Fibre inflationary models are constructed in type-IIB string flux compactification. These models have been shown to be in agreement with the cosmological observations under appropriate choices of parameters, which originate from their string theory construction. In the present work, we embed such models, originally studied in the cold inflation picture, in the context of warm inflation. We study the viability of different fibre inflation potentials in both strong and weak dissipative regime of warm inflation. In fibre inflation, the inflaton is a four-dimensional complex manifold -- a fibre of a $K3$ fibred Calabi-Yau. The potential in this case is generated by an interplay of various perturbative and non-perturbative corrections. The former type of corrections consists of leading-order ${\alpha }^{\prime 3}-$ term, higher derivative $F^4-$ correction, and various string loop corrections of KK, log-loop and winding type. Depending on the balance between several corrections, we present four different fibre inflationary potentials and show that the warm inflationary pictures for all of them can successfully fall in the viable window from both Planck and recent Atacama Cosmology Telescope (ACT) data. We show that warm inflation makes it possible to extend the range of parameters of applicability of these models. Our results also indicate that with the help of a large dissipation ratio, one can achieve a sub-Planckian field excursion, although, this runs on the possibility of moving away from the perturbative control of low-energy four-dimensional supergravity theory.

    ↳ hep-thastro-ph.COgr-qchep-phJHEP(2025)·14 citations
30. 30*

    Gravitational waves from low-scale cosmic strings without scaling

    Kai Schmitz🇩🇪 · Tobias Schröder🇩🇪

    Cosmic strings are predicted in many extensions of the Standard Model and constitute a plausible source of gravitational waves (GWs) from the early Universe. In a previous article arXiv:2405.10937v2, we pointed out that the GW spectrum from a population of string loops in the scaling regime can exhibit a sharp cutoff frequency associated with the fundamental oscillation mode of string loops. In this paper, we study the effect of particle decay due to kink-kink collisions and cusps on the GW spectrum in the nonscaling scenario introduced in Ref. arXiv:1911.12066. We find analytical conditions for the existence of a cutoff frequency in the fundamental spectrum and provide expressions for this frequency. In large regions of parameter space, our results in the nonscaling model turn out to be identical to those in the scaling model. Finally, we demonstrate how the spectrum changes when transitioning from the regime with a cutoff frequency to the regime without a cutoff frequency. Our analytical estimates are validated at qualitatively different benchmark points by comparing them with numerical spectra.

    ↳ astro-ph.COgr-qchep-phPRD(2025)·3 citations
31. 31*

    Axion Dark Matter Archaeology with Primordial Gravitational Waves

    Andrew Cheek🇨🇳 · Anish Ghoshal🇵🇱 · Debarun Paul🇮🇳

    We investigate the complementary information to be gained from inflationary gravitational wave (IGW) signals and searches for QCD axion dark matter. We focus on post-inflationary Peccei-Quinn (PQ) breaking axion models that are cosmologically safe. Recent work has shown that a greater number of such models exist. This is because the heavy quarks required for the colour anomaly can provoke a period of heavy quark domination (HQD), which, through decay, dilutes the axion abundance. In this work we show for the first time that the axion dark matter mass can be as low as $m_a\sim 10^{-8}\mathrm{eV}$ for models where the heavy quarks decay via dimension 6 terms. This is achieved by allowing the mass of the heavy quarks to differ from the axion decay constant, $m_Q\ne f_a$. Consequently, the observables that would distinguish between pre- and post-inflationary PQ breaking, $m_a$ and the additional relativistic degrees of freedom $\Delta N_{\mathrm{eff}}$, now become indiscernible. To solve this, we propose using blue-tilted IGWs to probe HQD. In scenarios where such a blue tilt is present, the enhanced GW signal allows future interferometers to place non-trivial constraints on the parameters $m_Q$ and $f_a$, thereby complementing haloscope searches. While some degeneracies with other parameters such as $m_Q$ remain, detectors such as BBO and ET will be able to optimistically probe $f_a\gtrsim 10^{14}\mathrm{GeV}$.

    ↳ astro-ph.COhep-phPRD(2026)·4 citations
32. 32*

    Improved Predictions on Higgs-Starobinsky Inflation and Reheating with ACT DR6 and Primordial Gravitational Waves

    Md Riajul Haque🇮🇳 · Sourav Pal🇮🇳 · Debarun Paul🇮🇳

    We investigate the implications of recent CMB observations for Higgs-Starobinsky inflationary models and their associated reheating dynamics, utilizing data from ACT DR6, Planck 2018, BICEP/Keck 2018, and DESI, collectively referred to as P-ACT-LB-BK18. In addition to direct CMB constraints, we incorporate indirect bounds arising from the potential overproduction of primordial gravitational waves (PGWs), particularly through limits on the effective number of relativistic species, $\Delta N_{\mathrm{eff}}$, during Big Bang Nucleosynthesis (BBN). These constraints become especially relevant in scenarios featuring a stiff post-inflationary equation of state $w_{\mathrm{RH}}\ge 0.58$. Our analysis shows that, when both P-ACT-LB-BK18 data and $\Delta N_{\mathrm{eff}}$ bounds are considered, the viable number of inflationary e-folds is restricted to the range ($57.9$-$62.2$) at the $2\sigma$ confidence level (C.L.). Correspondingly, the reheating temperature is constrained to lie between the BBN energy scale and $10^{12}$ GeV, with the post-inflationary equation-of-state parameter satisfying $w_{\mathrm{RH}}>0.41$. However, no parameter space remains viable at the $1\sigma$ C.L. once $\Delta N_{\mathrm{eff}}$ constraints from PGWs are included, rendering the Higgs-Starobinsky model highly restricted.

    ↳ astro-ph.COhep-phPLB(2025)·59 citations
33. 33*

    First Observations of Solar Halo Gamma Rays Over a Full Solar Cycle

    Tim Linden🇸🇪 · Jung-Tsung Li🇺🇸 · Bei Zhou🇺🇸 · Isabelle John🇮🇹 · Milena Crnogorčević🇸🇪 · Annika H. G. Peter🇺🇸 · John F. Beacom🇺🇸

    We analyze 15 years of Fermi-LAT data and produce a detailed model of the Sun's inverse-Compton scattering emission (solar halo), which is powered by interactions between ambient cosmic-ray electrons and positrons with sunlight. By developing a novel analysis method to analyze moving sources, we robustly detect the solar halo at energies between 31.6 MeV and 100 GeV, and angular extensions up to 45${}^{\circ }$ from the Sun, providing new insight into spatial regions where there are no direct measurements of the galactic cosmic-ray flux. The large statistical significance of our signal allows us to sub-divide the data and provide the first $\gamma$-ray probes into the time-variation and azimuthal asymmetry of the solar modulation potential, finding time-dependent changes in solar modulation both parallel and perpendicular to the ecliptic plane. Our results are consistent with (but with independent uncertainties from) local cosmic-ray measurements, unlocking new probes into both astrophysical and beyond-standard-model processes near the solar surface.

    ↳ astro-ph.HEastro-ph.SRhep-phPRD(2025)·11 citations
34. 34*

    Electromagnetic Field Momentum in Theoretical Magnetic Monopole-like Models

    Isaiah Ruz🇺🇸 · Douglas Singleton🇺🇸

    We show that some standard models of magnetic charge, the Banderet potential, the Dirac string potential, and the Wu-Yang fiber bundle approach, carry an electromagnetic field momentum in the presence of an electrostatic field. This electromagnetic field momentum suggests a violation of the center-of-energy theorem. We show that each of these monopole models also carry a hidden mechanical momentum, which saves the center-of-energy theorem.

    ↳ hep-thhep-phAm.J.Phys.(2025)·0 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.