Fri·Aug 22, 2025Friday·August 22, 2025

1. 01*

   Helicity amplitudes of $N(1520)$ and $N(1535)$ including pentaquark components

   Kai Xu🇹🇭 · Attaphon Kaewsnod🇹🇭 · Zheng Zhao🇹🇭 · Ayut Limphirat🇹🇭 · Yupeng Yan🇹🇭

   We investigate the helicity amplitudes of the $N(1520)$ and $N(1535)$ resonances in the electromagnetic transition process ${\gamma }^{\ast }p\to N^{\ast }$, where the $N(1520)$ and $N(1535)$ are assumed to include both the $L=1$ three-quark and $L=0$ spatial symmetric $q^4\bar{q}$ pentaquark components. The helicity transition amplitudes $A_{1/2}$, $A_{3/2}$ (for spin 3/2 states) and $S_{1/2}$ are computed within the constituent quark model. The inclusion of the $q^4\bar{q}$ pentaquark components via the ${\gamma }^{\ast }\to q\bar{q}$ diagram significantly improves the theoretical description of the helicity amplitudes for both $N(1520)$ and $N(1535)$, yielding a closer agreement with experimental data compared to the pure three-quark picture. The work reveals that the $N(1520)$ and $N(1535)$ resonances may contain a considerable pentaquark components.

   hep-phhep-thnucl-thPRD(2025)·0 citations
2. 02*

   Dilepton Spectra and Even Flow Harmonics in a Magnetized QGP: An Ideal Hydrodynamic Study

   Ankit Kumar Panda🇮🇳 · Aritra Das🇺🇸 · Ashutosh Dash🇩🇪 · Aritra Bandyopadhyay🇷🇴 · Chowdhury Aminul Islam🇸🇮

   We present the first comprehensive study of dilepton production from a hot, magnetized quark-gluon plasma in heavy-ion collisions (HIC), incorporating realistic, time-dependent, and spatially inhomogeneous magnetic field profiles within an analytically solvable Gubser flow background. This framework provides a significant improvement over previous static calculations with homogeneous fields and moves toward the long-term goal of full $3+1$D magnetohydrodynamic simulations. We explore the effects of impact parameter, electrical conductivity, and invariant mass on the dilepton spectra and anisotropic even flow coefficients. It is found that transverse momentum spectra increase with impact parameter, dominated by annihilation processes, while decay contributions remain sub-leading. Strikingly, the elliptic flow $v_2$ from decay channels is nonzero even in nearly central collisions, exhibiting a characteristic shape--positive at low $p_T$ and negative at high $p_T$--that is largely independent of impact parameter and conductivity. In contrast, $v_2$ from annihilation processes is smaller in magnitude but dominates the total flow in magnitude due to its larger yield. Higher harmonics, such as $v_4$, are an order of magnitude smaller as compared to $v_2$ along with distinctive zero-crossing patterns. Conductivity enhances both spectra and flow but leaves no unambiguous signature for its extraction. Varying the invariant mass reveals the strongest enhancements at low mass, with harmonic coefficients suppressed at higher masses. Overall, our results suggest that central and semi-central collisions can carry imprints of the background magnetic field, and that characteristic correlations in even flow harmonics may provide a robust probe of electromagnetic effects in HICs.

   hep-phnucl-th3 citations
3. 03*

   Potential of di-Higgs observation via a calibratable jet-free $HH\to 4b$ framework

   Tianyi Yang🇨🇳 · Congqiao Li🇨🇳

   We present a calibratable, jet-free framework that enhances the search significance of the flagship LHC channel $HH\to 4b$ by more than a factor of five compared to existing approaches. The method employs a mass-decorrelated discriminant to identify $h_1{h}_2\to 4b$ with variable $h_{1,2}$ masses and a simultaneous estimator of $(m_{h_1},m_{h_2})$, both derived from multiclass classification on all-particle inputs. The $HH$ signal response can be calibrated using $ZZ\to 4b$. Using a highly realistic simulation framework validated through multiple tests, we demonstrate the method's robustness and identify two prerequisites essential for achieving this level of sensitivity. Results indicate that with LHC Run 2 and 3 data, observation-level sensitivity to $HH$ appears within reach, enabling constraints on ${\kappa }_{\lambda }$ comparable to HL-LHC projections and offering an accelerated path to precision measurements of the Higgs trilinear coupling.

   hep-phhep-ex0 citations
4. 04*

   Determination of the pion generalized parton distributions at zero skewness

   The MMGPDs Collaboration · Muhammad Goharipour · M. H. Amiri · Fatemeh Irani · Hadi Hashamipour · K. Azizi

   We perform a global QCD analysis of the pion electromagnetic form factor (FF) data from pion electroproduction and elastic pion scattering to extract the valence pion generalized parton distributions (GPDs) at zero skewness. The analysis uses three different sets of pion parton distribution functions (PDFs), namely xFitter, JAM21, and MAP23, to construct the GPD ansatz. Through a ${\chi }^2$ minimization and a careful parametrization scan, we determine the profile function parameters and find that only two parameters are sufficient to describe the data. The extracted valence pion GPDs from different analyses have similar $x$-dependence, with minor differences at small momentum transfer. The resulting theoretical predictions for the pion electromagnetic FF and its squared magnitude show good agreement with experimental measurements. Among the three analyses, the one using the MAP23 PDFs provides the best overall fit and is adopted as the final GPD set. Our results offer a consistent determination of the valence pion GPDs, indicating a minor impact of the choice of pion PDFs. The present study provides a solid foundation for future investigations of pion structure, including its charge radius, tomography, and mechanical properties.

   hep-phhep-exPRD(2025)·4 citations
5. 05*

   The $\sin (2\varphi )$ azimuthal asymmetry in exclusive ${\pi }^0$ production

   Chentao Tan🇨🇳 · Zhun Lu🇨🇳

   The $\sin (2\varphi )$ azimuthal angular correlation between the transverse momenta of the scattered electron and the recoil proton in the $ep\to e^{\prime }{p}^{\prime }{\pi }^0$ process provides a probe for quark orbital angular momentum. We numerically calculate this asymmetry for the future Electron-Ion Collider (EIC) in the U.S. and China (EicC) kinematics using a light-front quark-scalar-diquark model, in which the light-front wave functions (LFWFs) are derived from the soft-wall AdS/QCD framework. We also investigate the properties of the valence quark angular momentum expressed in terms of helicity-independent and helicity-dependent parton distributions. This study aims to establish theoretical constraints on the asymmetry sensitive to the quark orbital angular momentum prior to its first experimental measurement.

   hep-ph1 citation
6. 06*

   Phenomenological description of the $D_{s0}^{\ast }(2317)\to D_s{\pi }^0$ decay

   N. N. Achasov🇷🇺 · G. N. Shestakov🇷🇺

   For coupled channels $D^0{K}^{+}$, $D^{+}{K}^0$, $D_s^{+}\eta$, and $D_s^{+}{\pi }^0$, the $S$-wave scattering amplitudes are constructed taking into account the mixing of the isoscalar resonance $D_{s0}^{\ast }(2317{)}^{+}$ with nonresonance amplitudes with isospin $I=1$. The phenomenological approach we use allows us to quite simply clear up the general structure of the $D_{s0}^{\ast }(2317{)}^{+}\to D_s^{+}{\pi }^0$ decay amplitude violating isospin. We show that the phase of this amplitude coincides with the phase of the nonresonanct $D_s^{+}{\pi }^0$ scattering amplitude in agreement with the Watson theorem. Its modulus squared, as it should be, determines the width of the resonance peak in the $D_s^{+}{\pi }^0$ channel. Taking into account the ${\pi }^0-\eta$ mixing in internal lines up to the second order inclusively ensures that the unitarity condition is fulfilled. The presented analysis complements the description of the $D_{s0}^{\ast }(2317{)}^{+}\to D_s^{+}{\pi }^0$ decay based on the coupled channel unitarized chiral perturbation theory. The numerical estimates obtained by us for the $D_{s0}^{\ast }(2317{)}^{+}\to D_s^{+}{\pi }^0$ decay width do not contradict those available in the literature.

   hep-phhep-exhep-thPRD(2025)·4 citations
7. 07*

   Transversity Generalized Parton Distributions of $\Delta$ with the Diquark Spectator Model

   Dongyan Fu🇨🇳 · Yubing Dong🇨🇳 · S. Kumano🇨🇳

   We show quark transversity generalized parton pistributions (GPDs) of ${\Delta }^{+}$ isobar by using the diquark spectator model for the first time. First, this model is tested by electric charge, magnetic-dipole and axial charge form factors, and it is used for calculating the transversity GPDs $H_{1,3,5,7}^{qT}$ of ${\Delta }^{+}$. The quark transversity distribution $h_1$ is then obtained from the transversity GPDs in the forward limit. Then, helicity-flip amplitudes are shown numerically by using relations between the helicity amplitudes and the GPDs. Finally, by taking first moments of the GPDs, tensor form factors are obtained and we predict the tensor charge. Experimentally, $N$-$\Delta$ transition GPDs are investigated in deeply virtual Compton scattering and virtual meson-production processes, and generalized distribution amplitudes, which correspond to the $s$-channel GPDs, could be investigated by the two-photon processes ${\gamma }^{\ast }\gamma \to \Delta \bar{\Delta }$ at the electron-positron colliders. Therefore, the spin-3/2 $\Delta$ GPDs could become interesting quantities experimentally in future.

   hep-phhep-exhep-latnucl-thPRD(2025)·1 citation
8. 08*

   Study of Particle Production in Au+Au Collisions at $\sqrt{s_{NN}}=$ 11.5-200 GeV Using HYDJET++ Framework

   Gauri Devi🇮🇳 · Satya Ranjan Nayak🇮🇳 · B. K. Singh🇮🇳

   Using the HYDJET++ model, we study the production of multi-strange particles($\varphi$ and $\Omega$) in Au+Au collisions at $\sqrt{s_{NN}}=$ 11.5, 19.6, 27, 39, and 200 GeV as functions of transverse momentum and centrality. The model calculations employ earlier freeze-out hypersurfaces for multi-strange particle production and are compared with STAR experimental data. Results indicate that the HYDJET++ model demonstrates a better agreement with experimental data for multi-strange particles at higher energies, particularly in relation to early thermal freeze-out. Meanwhile, the default version performs more accurately for lighter, non-strange particles at the same energy scales. We also analyze identified particle and mixed particle ratios, providing insights into strangeness enhancement. The results provide additional constraints on parton energy loss models, contributing to a more precise determination of the transport properties of hot and dense QCD matter.

   hep-phPRC(2026)·1 citation
9. 09*

   Cosmology with an emergent Standard Model

   Steven D. Bass🇵🇱

   We discuss new ideas that the Standard Model might be emergent with connection to electroweak vacuum stability and related consequences for cosmology. In this scenario, the gauge symmetries and particles of the Standard Model would be ``born'' in some phase transition at a large scale about $10^{16}$ GeV with the Standard Model parameters constrained by the requirement of vacuum stability.Emergent gauge symmetries are well known in condensed matter physics. Perhaps the Standard Model might also be emergent. In this case the particles would be the stable long range excitations of degrees of freedom that operate above the scale of emergence. The dark energy scale comes out with similar size to the tiny masses of light Majorana neutrinos. The emergence scenario comes with interesting constraints on possible dark matter structure. New physics at energy scales around $10^{16}$ GeV might be explored through its effects in the neutrino mass matrix plus using high frequency gravitational waves and polarisation observables in the cosmic microwave background.

   hep-phastro-ph.COMod.Phys.Lett.A(2025)·1 citation
10. 10*

    On the Lagrangian and fermion mass of the unified $SU(2)\otimes SU(4)$ gauge field theory

    Eckart Marsch🇩🇪 · Yasuhito Narita🇩🇪

    In the Standard Model of elementary particles the fermions are assumed to be intrinsically massless. Here we propose a new theoretical idea of fermion mass generation (other than by the Higgs mechanism) through the coupling with the vector gauge fields of the unified $SU(2)\otimes SU(4)$ gauge symmetry, especially with the $Z$ boson of the weak interaction that affects all elementary fermions. The resulting small masses are suggested to be proportional to the self-energy of the $Z$ field as described by a Yukawa potential. Thereby the electrically neutral neutrino just gets a tiny mass through its $Z$-field coupling. In contrast, the electrically charged electron and quarks can become more massive by the inertia induced through the Coulomb energy of the electrostatic fields surrounding them in their rest frames.

    hep-phhep-th0 citations
11. 11*

    Critical Phenomena in Hadronic and DIS Processes

    L.L. Jenkovszky🇺🇦 · C. Merino🇪🇸

    We compare the critical phenomena (e.g. phase transitions, crossover) in proton-proton, proton-nucleus scattering and in lepton-proton deep inelastic scattering (DIS) systems.

    hep-phnucl-th0 citations
12. 12*

    Quark polarization and transverse momentum effects on double quarkonium production in hadronic collisions

    Carlo Flore🇮🇹 · Cristian Pisano🇮🇹

    We investigate the inclusive production of double quarkonia ($J/\psi$, $\psi (2S)$, ${\rm Y}$ mesons) in polarized hadron-hadron collisions, considering the kinematic configuration where the transverse momentum of each pair of bound states is much smaller than its invariant mass. Supported by nonrelativistic QCD arguments, we adopt the Color-Singlet Model for the quarkonium formation mechanism and assume the validity of transverse momentum dependent factorization. In strong analogy with dilepton production in the Drell-Yan processes, the azimuthal modulations of the cross section, calculated to the order ${\alpha }_s^4$ in the QCD coupling constant, can be expressed as convolutions of transverse momentum dependent distributions of light quarks and antiquarks inside the incoming hadrons. By adopting very recent parameterizations of these distributions, we show that a phenomenological study of these quantities in ${\pi }^{-}p\to J/\psi J/\psi X$ in the kinematic region covered by the COMPASS and AMBER fixed-target experiments at CERN, where the gluon contribution is found to be negligible, would provide direct access to the quark distributions. In particular, this will offer the possibility of a further sign change test of the quark Sivers function of the proton. The impact of our findings on similar studies about the gluon content of the proton in present and future fixed-target experiments at the LHC, like SMOG and LHCspin, is also demonstrated.

    hep-phhep-exJHEP(2026)·1 citation
13. 13*

    Sub-GeV Right-Handed Neutrino as a Probe of Neutrino Mass Generation in the Minimal Left-Right Symmetric Model

    Gang Li🇨🇳 · Ying-Ying Li🇨🇳 · Sida Lu🇨🇳 · Ye-Ling Zhou🇨🇳

    The minimal left-right symmetric model (mLRSM) provides an elegant and testable framework for addressing the origin of neutrino masses. We examine the constraints on the sub-GeV right-handed (RH) neutrino in the type-II seesaw scenario of the mLRSM without left-right mixing, taking limits from collider searches, meson decays, supernovae, neutrinoless double beta ($0\nu \beta \beta$) decay and cosmology. Specifically, we derive the $0\nu \beta \beta$ decay constraints using the advanced effective field theory approach and up-to-date nuclear matrix element calculations. Besides, we update the SN1987A cooling bound with the state-of-the-art simulations, provide new constraints from the energy deposition in the supernova ejecta, and incorporate the stringent RH neutrino lifetime upper limit $\tau \lesssim 0.023\text{ s}$ from the big bang nucleosynthesis. Our results identify the parameter region compatible with all current experimental and observational constraints, where the RH neutrino mass lies between 700 MeV and 1 GeV and the RH $W$ boson mass is slightly below 20 TeV. This region is exclusively probed by the future tonne-scale $0\nu \beta \beta$ decay experiments, providing a unique window to test the mLRSM and the possible origin of neutrino masses.

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

    The recoil corrections, correlation functions and possible double-strange hadronic molecules

    Xiao-Mei Tang🇨🇳 · Li-cheng Sheng🇨🇳 · Qi Huang🇨🇳 · Rui Chen🇨🇳

    In this work, we perform a systematic investigation of $K^{(\ast )}{K}^{(\ast )}$ interactions within a one-boson-exchange model.The framework incorporates both $S-D$ wave mixing and coupled-channel effects, with effective potentials retained up to order $\mathcal{O}(1/M^2)$. By solving the coupled channel Schrödinger equations, we can predict two double-strange molecular candidates: a $K{K}^{\ast }$ molecule with $I(J^P)=0(1^{+})$ and a $K^{\ast }{K}^{\ast }$ molecule with $0(1^{+})$. Our results also show that the recoil corrections play a crucial role in the formation of these two molecular candidates. Furthermore, the $S-D$ wave mixing effects contribute positively to the formation process. As a byproduct of this analysis, we extend our study to $K^{(\ast )}{\bar{K}}^{(\ast )}$ interactions with the same model. Our findings suggest that the $K{\bar{K}}^{\ast }$ states with $0(1^{+-},1^{++})$ and $K^{\ast }{\bar{K}}^{\ast }$ states with $0(0^{++},1^{+-},2^{++})$ can be promising molecular candidates. Additionally, we analyze the correlations between the constituent mesons, the resulting correlation functions provide additional support for our predictions of both double-strange and strangonium-like molecular states.

    hep-phPLB(2025)·4 citations
15. 15*

    New rephasing invariants and CP violation built from the trios of the CKM or PMNS matrix elements

    Shu Luo🇨🇳 · Zhi-zhong Xing🇨🇳

    Given the $3\times 3$ Cabibbo-Kobayashi-Maskawa (CKM) quark flavor mixing matrix $V$, we define a new set of rephasing invariants in terms of the "trios" of its nine elements: ${◊}_{\alpha \beta \gamma }^{ijk}\equiv (V_{\alpha i}^{}{V}_{\beta j}^{}{V}_{\gamma k}^{})/\det V$ with $\alpha \ne \beta \ne \gamma$ and $i\ne j\ne k$ running respectively over $(u,c,t)$ and $(d,s,b)$. We find that $\mathrm{Im}{◊}_{\alpha \beta \gamma }^{ijk}=-\mathcal{J}$ holds, where $\mathcal{J}$ is the well-known Jarlskog invariant of weak CP violation. Analogous rephasing invariants ${⧫}_{\alpha \beta \gamma }^{ijk}\equiv (U_{\alpha I}^{}{U}_{\beta j}^{}{U}_{\gamma k}^{})/\det U$ can be defined for the $3\times 3$ Pontecorvo-Maki-Nakagawa-Sakata (PMNS) lepton flavor mixing matrix $U$, where $\alpha \ne \beta \ne \gamma$ and $i\ne j\ne k$ run respectively over $(e,\mu ,\tau )$ and $(1,2,3)$. Taking into account small non-unitarity of $U$ based on the canonical seesaw mechanism for neutrino mass generation, we calculate $\mathrm{Im}{⧫}_{\alpha \beta \gamma }^{ijk}$ with the help of a full Euler-like block parametrization of the seesaw flavor structure and demonstrate that their leading terms converge to a universal invariant ${\mathcal{J}}_{\nu }^{}$ in the unitarity limit of $U$.

    hep-phhep-exNPB(2026)·5 citations
16. 16*

    Testing the heavy decaying sterile neutrino hypothesis at the DUNE near detector

    Sabya Sachi Chatterjee🇩🇪 · Stéphane Lavignac🇫🇷 · O. G. Miranda🇲🇽

    One of the most convincing explanations of the LSND and MiniBooNE anomalies relies on a heavy, mostly sterile neutrino with a small muon neutrino component, which decays to an electron neutrino and an invisible light scalar field. We investigate the possibility to test this hypothesis at the near detector complex of the upcoming DUNE experiment. We find that the DUNE liquid argon near detector (ND-LAr) can probe a larger region of the parameter space than the Fermilab SBN program, and may help to confirm or reject a possible hint of ${\nu }_e$ appearance in future MicroBooNE, SBND or ICARUS data. We also argue that it may be possible to distinguish between Dirac and Majorana neutrinos if this scenario is realized in Nature.

    hep-phhep-exJHEP(2025)·0 citations
17. 17*

    Constraining light dark matter in vector-scalar portals with COSI and AMEGO-X

    Maíra Dutra🇺🇸 · Clarissa Siqueira🇧🇷 · Tonia M. Venters🇺🇸

    Detecting gamma-ray signals that could be due to dark matter (DM) particles would give us invaluable information about the nature of DM. In particular, gamma-ray lines could provide a way to measure the DM mass. The excellent energy resolution of the upcoming Compton Spectrometer and Imager (COSI) will allow us to probe underexplored regions of the DM parameter space while being sensitive to distinctive spectral features of potential DM signals. In this work, we consider a fermionic sub-GeV DM charged under a new U(1) gauge symmetry. Both the DM and the new gauge boson $Z^{\prime }$ acquire mass from a new singlet scalar. The masses of the new particles in this class of vector-scalar portal models are naturally at the MeV scale, enabling detectable gamma-ray lines in the bandpasses of COSI and proposed missions such as the All-sky Medium Energy Gamma-ray Observatory eXplorer (AMEGO-X). We estimate the sensitivities of COSI and AMEGO-X to sub-GeV DM in this context, considering a B-L and a purely axial $Z^{\prime }$ as benchmark examples. We find regions of the parameter space where COSI will provide leading constraints, beyond the strong CMB limits. On the other hand, AMEGO-X would probe most of the viable parameter space leading to continuum gamma rays. The implementation of our generic vector-scalar portal model in the Hazma toolkit is available at GitHub.

    hep-phastro-ph.HEhep-thJHEP(2026)·2 citations
18. 18*

    Probing $0\nu \beta \beta$ and $\mu \to e\gamma$ via Fully Determined Dirac Mass Terms in LRSM with Double Seesaw

    Pratik Adarsh🇮🇳 · Rajrupa Banerjee🇮🇳 · Purushottam Sahu🇮🇳 · Utkarsh Patel🇮🇳 · Sudhanwa Patra🇮🇳

    Neutrinoless double beta decay ($0\nu \beta \beta$) and charged lepton flavor violation (cLFV) experiments provide promising avenues to probe new physics contributions from extended neutrino sectors in beyond Standard Model (BSM) scenarios. We consider a Left-Right Symmetric Model (LRSM) extended with three generations of sterile neutrinos to realize a double type-I seesaw mechanism for light neutrino mass generation. The double seesaw induces maximal lepton number violation in the right-handed sector and facilitates enhanced Majorana masses for right-handed neutrinos, thereby leading to their dominant contributions in both cLFV and $0\nu \beta \beta$ processes. We perform a comprehensive exploration of the parameter space for new-physics contributions to the cLFV decay $\mu \to e\gamma$ and to $0\nu \beta \beta$, considering two different textures for the Dirac mass matrices: (i) a symmetry-motivated limit with $M_D\propto 1$, and (ii) a texture fully determined by the model framework. A detailed analysis of the common parameter regions accessible to current experiments like KamLAND-Zen and LEGEND-200, and upcoming experiments, such as MEG-II and LEGEND-1000, is presented, underscoring the phenomenological relevance of this framework. Our results aim to provide optimistic benchmarks for future searches targeting right-handed current-mediated neutrino interactions.

    hep-phhep-exJHEP(2026)·1 citation
19. 19*

    Electroweak symmetry non-restoration and suppressed dark radiation in Supersymmetric Twin Higgs model

    Marcin Badziak🇵🇱 · Keisuke Harigaya🇺🇸 · Ignacy Nałęcz🇵🇱

    We investigate a possibility of electroweak symmetry non-restoration (SNR) below the Twin electroweak scale ($\sim$TeV) within the Twin Higgs model. We focus on supersymmetric extensions with light sfermions where SNR is driven by mirror symmetry breaking in the Yukawa couplings. The inclusion of light scalars not only stabilizes the electroweak scale, but also extends SNR into new regions of the parameter space and enables a first-order phase transition. When this model is augmented with right-handed neutrinos with unbroken $B^{\prime }-L^{\prime }$ in the twin sector, the number of dark relativistic degrees of freedom can be reduced to the level consistent with the constraints from CMB data. The SNR in the supersymmetric Twin Higgs framework can naturally be integrated with minimal axiogenesis, offering a simultaneous explanation for the origin of baryon asymmetry and dark matter and the resolution of the strong CP problem that is consistent with astrophysical constraints.

    hep-phJHEP(2026)·3 citations
20. 20*

    Proton Pressure: A Simplified Model

    Julliana Marinho Paszko🇧🇷 · Mauro Rogério Cosentino🇧🇷

    In this work, the authors present a simplified method for determining proton pressure, based on concepts from statistical mechanics, quantum chromodynamics - specifically asymptotic freedom of quarks - and other well-established physical concepts. The result obtained for the proton pressure was $0.3570\times 10^{35}$ Pa, which is consistent with recently reported experimental data.

    hep-phnucl-ex0 citations
21. 21*

    Disentangling the Origins of the NANOGrav Signal: Early Universe Models and $\Delta N_{eff}$ Bounds

    Ido Ben-Dayan🇮🇱 · Utkarsh Kumar🇨🇦 · Amresh Verma🇮🇱

    We investigate whether an Early-Universe stochastic gravitational-wave background (SGWB) can account for the common spectrum process reported by NANOGrav, while also being consistent with current and projected CMB measurements of extra radiation. We compute the contribution of effective number of relativistic species, $\Delta N_{eff}$, for a number of Early-Universe models proposed to explain the pulsar timing array (PTA) spectrum. We demonstrate that models predicting $\Delta N_{eff}$ above the CMB limit would be firmly excluded, implying that the NANOGrav signal in tension with these bounds must instead arise from astrophysical sources. We find that current NANOGrav 15-year dataset, sensitive up to 60 nHz, gives a negligible contribution to $\Delta N_{eff}$ and remains well below the present and future CMB detection threshold. However, when we project future PTA capabilities reaching upto 1 $\mu$Hz, even with our conservative estimate we find that Inflation, Scalar Induced Gravitational Waves (SIGW), and metastable cosmic strings can induce a $\Delta N_{eff}$ large enough for $>3.5\sigma$ detection by the Simons Observatory.

    ↳ astro-ph.COgr-qchep-phhep-thJHEAp(2026)·7 citations
22. 22*

    High-precision determination of radiative corrections to superallowed nuclear beta decays

    Chien-Yeah Seng🇺🇸

    Superallowed $0^{+}\to 0^{+}$ transitions between $T=1$ nuclei have been a perfect avenue avenue for determining the Cabibbo-Kobayashi-Maskawa matrix element $V_{ud}$, which imposes powerful constraints on physics beyond the Standard Model at low energies. For a long time, the precision of $V_{ud}$ has been limited by uncertainties in radiative corrections that arise from non-perturbative strong interaction physics at both the hadronic and nuclear levels. In this talk, I will describe some recent efforts to pin down these corrections by combining dispersive analysis with experimental data, lattice QCD, and nuclear many-body calculations.

    ↳ nucl-thhep-exhep-lathep-ph+1EPJ Web Conf.(2025)·2 citations
23. 23*

    Contribution of Globular Clusters to Diffuse Gamma-ray Emission from Galactic Plane

    Jiayin He🇨🇳 · Houdun Zeng🇨🇳 · Yi Zhang🇨🇳 · Xiaoyuan Huang🇨🇳 · Qiang Yuan🇨🇳

    The diffuse Galactic $\gamma$-ray emission (DGE) provides a valuable probe for investigating the cosmic ray propagation and interactions within our Galactic environment. Recent observations have demonstrated systematic excesses of DGE compared with the conventional cosmic-ray propagation model predictions. While $\gamma$-ray emissions have been detected in a subset of globular clusters, their undetected populations may significantly contribute to the DGE. Motivated by this possibility, we present a comprehensive assessment of potential contributions from unresolved globular clusters to the DGE. In our analysis, a nonparametric method is employed to estimate the luminosity function and spatial distribution function of globular clusters using the Fermi-LAT fourth source catalog (4FGL) combined with a reference globular cluster catalog. Based on these distributions, we calculate the cumulative contribution of unresolved globular cluster populations to the DGE observed by Fermi-LAT and the Large High Altitude Air Shower Observatory (LHAASO). Our results reveal that globular clusters account for only $\sim$2\% of the DGE at the TeV range, and smaller than $1\%$ in the GeV regime, which is effectively negligible.

    ↳ astro-ph.HEhep-phApJ(2025)·0 citations
24. 24*

    Robustness of Solutions of the Quantum Kinetic Equations in the Presence of Matter Density Fluctuations

    Shashank Shalgar🇩🇰 · Mariam Gogilashvili🇩🇰

    We investigate the role of fluctuations in the matter density on neutrino flavor evolution by studying their effects on the collision terms in the spherically symmetric quantum kinetics equations (QKEs). We solve the QKEs with varying radial resolution ($r_{\mathrm{bins}}=150,1500,15000$) to assess numerical convergence in angular distributions, number densities, and energy spectra for four neutrino flavors (${\nu }_e$, ${\bar{\nu }}_e$, ${\nu }_x$, ${\bar{\nu }}_x$). Our results demonstrate that the solutions are numerically converged already at the coarsest resolution, with higher resolutions yielding almost identical outcomes. We introduce random perturbations to each radial bin, thus adding perturbations with a length scale that is related to the radial resolution. We study both time-independent and time-dependent perturbations to the matter density that affect the collision term and analyze their effects on neutrino flavor evolution. We find that such fluctuations do not induce any significant instabilities or qualitative changes in flavor evolution. Angular structure remains robust, and flavor-dependent number densities and energy spectra show only minor deviations compared to the unperturbed case. These findings suggest that matter perturbations have a negligible effect on neutrino flavor evolution in spherically symmetric settings.

    ↳ astro-ph.HEhep-ph0 citations
25. 25*

    Bose-Einstein Condensates in Astrophysics and Cosmology: From Quantum Statistics to Cosmic Structures

    Nader Haddad🇬🇧

    We present a comprehensive theoretical investigation of Bose-Einstein condensates (BECs) and their manifestations in astrophysical and cosmological contexts. Building upon the foundations of quantum statistics in curved spacetime, we derive the conditions for BEC formation under extreme gravitational fields and explore their implications for compact objects and early universe physics. Through rigorous mathematical treatment incorporating general relativistic corrections to the Bose-Einstein distribution, we demonstrate that BEC phenomena may play crucial roles in neutron star interiors, primordial black hole formation, and dark matter halos. Our analysis reveals that the critical temperature for condensation exhibits non-trivial dependence on spacetime curvature, with corrections of order O(GM/rc2) becoming significant near compact objects. We further show that axion dark matter, if it exists, naturally forms a cosmic BEC with coherence length {\lambda}dB ~ 10^-3 pc for ma ~ 10^-22 eV, potentially explaining the observed core-cusp problem in galactic dark matter profiles. These findings suggest that quantum coherence effects at macroscopic scales may be more prevalent in the universe than previously recognized, with profound implications for our understanding of cosmic structure formation and the behaviour of matter under extreme conditions.

    ↳ astro-ph.COastro-ph.HEgr-qchep-ph0 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.