Tue·Aug 13, 2024Tuesday·August 13, 2024

1. 01*

   Testing Bell inequalities and probing quantum entanglement at a muon collider

   Alim Ruzi🇨🇳 · Youpeng Wu🇨🇳 · Ran Ding🇨🇳 · Sitian Qian🇨🇳 · Andrew Micheal Levin🇨🇳 · Qiang Li🇨🇳

   A muon collider represents a promising candidate for the next generation of particle physics experiments after the expected end of LHC operations in the early 2040s. Rare or hard-to-detect processes at the LHC, such as the production of multiple gauge bosons, become accessible at a TeV muon collider. We present here the prospects of detecting quantum entanglement and the violation of Bell inequalities in H to ZZ to 4l events at a potential future muon collider. We show that the spin density matrix of the Z boson pairs can be reconstructed using the kinematics of the charged leptons from the Z boson decays. Once the density matrix is determined, it is straightforward to obtain the expectation values of various Bell operators and test the quantum entanglement between the Z boson pair. Through a detailed study based on Monte-Carlo simulation, we show that the generalized CGLMP inequality can be maximally violated, and testing Bell inequalities could be established with high significance.

   hep-phhep-exquant-phJHEP(2024)·36 citations
2. 02*

   Search for Light $H^{+}$ via $e^{+}{e}^{-}\to H^{+}{H}^{-}\to c\bar{b}\bar{c}b$ @ ILC500

   George Wei-Shu Hou🇹🇼

   Our current {\it impasse}: no new physics seen beyond the $h(125)$ boson. We advocate the {\it general} two Higgs doublet model without $Z_2$ symmetry, allowing extra Yukawa couplings, where we present 5 clear merits. We report on the search effort at LHC for $pp\to tt\bar{c}$, then on the new effort of $pp\to b{H}^{+}\to bt\bar{b}$ search for $H^{+}$, and comment on our \underline{\bf Decadal Mission} program in Taiwan. Finally, we turn to the $e^{+}{e}^{-}\to H^{+}{H}^{-}\to c\bar{b}\bar{c}b$ program at ILC500 as a {\it what-if} situation at the LHC, demonstrating light $H^{+}$ reconstruction without $c$-tagging. We then end with discussion and conclusion.

   hep-phhep-ex0 citations
3. 03*

   Charged pions asymmetry from the decay of light neutral axial mesons due to interference

   Fabio L. Braghin🇧🇷

   Effective three meson couplings, based in flavor U(3) quark-antiquark interactions, are considered to describe two light neutral axial meson Strong decays, $A\sim f_1(1285)$ and $f_{1S}(1420)$, and the charged rho meson decay in the following channels: $A\to {\rho }^{\mp }(770)+{\pi }^{\pm }$, $A\to a_0^{\mp }(980)+{\pi }^{\pm }$ and ${\rho }^{\pm }\to {\pi }^{\pm }{\pi }^0$. By considering neutral meson mixings, such as $f_1(1285)-a_1^0(1260)$, $f_{1S}(1420)-a_1^0(1260)$ and $\eta -{\pi }^0$ for the channels investigated, the leading three-meson interactions may lead to decay amplitudes that undergo interference and a resulting ratio of decay rate into charged pions, ${\Gamma }_{{\pi }^{+}}/{\Gamma }_{{\pi }^{-}}$, slightly smaller than one. For that it will be assumed that the produced charged vector mesons or charged scalar mesons undergo absorption, decay into channels without charged pions, or any other inelastic process that may suppress their decays into charged pions.

   hep-phnucl-thJ.Phys.G(2025)·1 citation
4. 04*

   Zh Production, a Tool to Constrain 2HDM

   Zeynab Bozorgtabar🇮🇷 · Saeid Paktinat Mehdiabadi🇮🇷

   Since the SM Higgs boson, h, is the superposition of two unequal-mass neutral Higgs bosons in 2HDM, therefore the associated production cross section for h and Z in SM and 2HDM can be different. In this paper, the possibility of using this difference to discover or constrain 2HDM is studied. As a main result, the allowed parameter space of 2HDM type-II is found in the light of possible precise measurements from the LHC experiments. It is shown that combination of the constraints from these measurements with the previous constraints on 2HDM, from direct search and flavour physics, can rule out the main part of the 2HDM parameter space.

   hep-phInt.J.Theor.Phys.(2024)·0 citations
5. 05*

   TMD evolution effect on $\cos 2\varphi$ azimuthal asymmetry in a back-to-back production of $J/\psi$ and jet at the EIC

   Raj Kishore🇪🇸 · Asmita Mukherjee🇮🇳 · Amol Pawar🇮🇳 · Sangem Rajesh🇮🇳 · Mariyah Siddiqah🇮🇳

   A back-to-back semi-inclusive $J/\psi +jet$ production is a promising process to study gluon transverse momentum distribution (TMDs) at the future electron-ion collider (EIC). A back-to-back configuration allows a higher transverse momentum for $J/\psi$. We present an extension of a previous work where we studied $\cos 2\varphi$ azimuthal asymmetry within the TMD factorization framework for this process. We present and compare the effect of TMD evolution on the asymmetry, in two approaches that differ in the parameterization of the perturbative tails of the TMDs and the non-perturbative factors. We show that the asymmetry depends on the parameterizations of the non-perturbative Sudakov factors in the larger $b_T$ region and on the perturbative part of the evolution kernel. We use NRQCD to estimate the $J/\psi$ production and show the effect of using different long-distance matrix element (LDME) sets. Overall, the asymmetry after incorporating TMD evolution is small, but increases with the transverse momentum imbalance of the $J/\psi$-jet pair.

   hep-phPRD(2025)·5 citations
6. 06*

   Constraints on non-standard cosmological models from Planck data

   Hoernisa Iminniyaz🇨🇳 · Alimasi Aisha🇨🇳 · Fangyu Liu🇨🇳

   We review the relic density of dark matter in the non-standard cosmological scenarios which includes kination models, brane world cosmology and shear dominated universe. Then we use the Planck data to find constraints on the parameter spaces as dark matter cross sections and the five dimentional Planck mass for brane cosmology, enhancement factor for kination model and the inverse-scaled shear temperature for shear dominated universe.

   hep-phPhys.Part.Nucl.(2025)·0 citations
7. 07*

   QCD condensates and ${\alpha }_s$ from $\tau$-decay

   S. Narison (LUPM, CNRS/Univ. Montpellier-FR and iHEPMAD, Univ. Antananarivo (MG))🇫🇷

   We improve the determinations of the QCD condensates within the SVZ expansion in the axial-vector (A) channel using the ratio of Laplace sum rule (LSR) ${\mathcal{R}}_{10}^A(\tau )$ within stability criteria and $\tau$-like higher moments $R_{n,A}$ within stability for arbitrary $\tau$-mass squared $s_0$. We find the same violation of the factorization by a factor 6 of the four-quark condensate as from $e^{+}{e}^{-}\to$ Hadrons data. One can notice a systematic alternate sign and no exponential growth of the size of these condensates. Then, we extract ${\alpha }_s$ from the lowest $\tau$-decay like moment and find: ${\alpha }_s(M_{\tau }){|}_{V-A}=0.3135(83)$ (FO) and 0.3322 (81) (CI) leading to: ${\alpha }_s(M_Z){|}_{V-A}=0.1177(10{)}_{fit}(3{)}_{evol.}$ (FO) and $0.1200(9{)}_{fit}(3{)}_{evol.}$\,(CI). We extend the analysis to the V--A channel and find: ${\alpha }_s(M_{\tau }){|}_{V-A}=0.3135(83)$ (FO) and 0.3322 (81) (CI) leading to: ${\alpha }_s(M_Z){|}_{V-A}=0.1177(10{)}_{fit}(3{)}_{evol.}$ (FO) and $0.1200(9{)}_{fit}(3{)}_{evol.}$\,(CI). We observe that in different channels ($e^{+}{e}^{-}\to$ Hadrons, \, A,\,V-A), the extraction of ${\alpha }_s(M_{\tau })$ at the observed $\tau$-mass leads to an overestimate of its value. Our determinations from these different channels lead to the mean: ${\alpha }_s(M_{\tau })=0.3140(44)$ (FO) and 0.3346 (35) (CI) leading to: ${\alpha }_s(M_Z)=0.1178(6{)}_{fit}(3{)}_{evol.}$ (FO) and $0.1202(4{)}_{fit}(3{)}_{evol.}$(CI). Comparisons with some other results are done.

   hep-phNPA(2025)·1 citation
8. 08*

   Leptonic dipole operator with ${\Gamma }_2$ modular invariance in light of Muon $(g-2{)}_{\mu }$

   Takaaki Nomura🇨🇳 · Morimitsu Tanimoto🇯🇵 · Xing-Yu Wang🇨🇳

   We have studied the leptonic EDM and the LFV decays relating with the recent data of anomalous magnetic moment of muon, $(g-2{)}_{\mu }$ in the leptonic dipole operator. We have adopted the successful ${\Gamma }_2$ modular invariant model by Meloni-Parriciatu as the flavor symmetry of leptons. Suppose the anomaly of $(g-2{)}_{\mu }$, $\Delta a_{\mu }$ to be evidence of New Physics (NP), we have related it with the anomalous magnetic moment of the electron $\Delta a_e$, the electron EDM $d_e$ and the $\mu \to e\gamma$ decay. We found that the NP contributions to $\Delta a_{e(\mu )}$ are proportional to the lepton masses squared likewise the naive scaling $\Delta a_{\ell }\propto m_{\ell }^2$. The experimental constraint of $|d_e|$ is much tight compared with the one from the branching ratio $\mathcal{B}(\mu \to e\gamma )$ in our framework. Supposing the phase of our model parameter ${\delta }_{\alpha }$ for the electron to be of order one, we have estimated the upper-bound of $\mathcal{B}(\mu \to e\gamma )$, which is at most $10^{-21}-10^{-20}$. If some model parameters are real, leptonic EDMs vanish since the CP phase of the modular form due to modulus $\tau$ does not contribute to the EDM. However, we can obtain $\mathcal{B}(\mu \to e\gamma )\simeq 10^{-13}$ with non-vanishing $d_e$ in a specific case. The imaginary part of a parameter can lead to $d_e$ in the next-to-leading contribution. The predicted electron EDM is below $10^{-32}$e\,cm, while $\mathcal{B}(\mu \to e\gamma )$ is close to the experimental upper-bound. The branching ratios of $\tau \to e\gamma$ and $\tau \to \mu \gamma$ are also discussed.

   hep-phhep-exEPJC(2024)·2 citations
9. 09*

   Study of gluon GPDs in exclusive $J/\psi$ production in electron-proton scattering

   S.V. Goloskokov🇷🇺 · Ya-Ping Xie🇨🇳 · Xurong Chen🇨🇳

   Exclusive photoproduction of heavy $J/\psi$ meson is performed within handbag factorization method. The General Parton Distributions (GPDs) for gluons which are an essential ingredient here, are constructed using double distribution (DD) representation. The calculated cross section for few sets of gluon GPDs $H_g$ describe fine $J/\psi$ production experimental data from HERA to LHC energies. Based on this approach we estimate $J/\psi$ spin asymmetries determined by $E_g$ and ${\tilde{H}}_g$. The GPDs factorization approach can be employed to analyse heavy vector meson production in electron-proton scattering. Investigations of this reactions at future electron-ion colliders in USA and China can give an essential information on gluon GPDs.

   hep-phPRD(2024)·14 citations
10. 10*

    $X(4630)$ and $Y(4626)$ production in the $B^{+}$ and $B_s^0$ decays

    Zhuo Yu🇨🇳 · Qi Wu🇨🇳 · Dian-Yong Chen🇨🇳

    In the present work, we investigate the production of $X(4630)$ and $Y(4626)$ in $B^{+}$ and $B_s^0$ decays, where $X(4630)$ and $Y(4626)$ are considered as the $C-$ parity pigeon pair in the $D_s^{\ast +}{D}_{s1}(2536{)}^{-}$ molecular frame. The branching fractions of $B^{+}\to K^{+}X(4630)/Y(4626)$ and $B_s^0\to \eta X(4630)/Y(4626)$ have been evaluated using an effective Lagrangian approach, which are of the order of $10^{-5}$ and the ratios of these branching fractions are almost independent on the model parameter. Based on the present estimations, we propose to search $Y(4626)$ in the process $B^{+}\to K^{+}J/\psi {\eta }^{(\prime )}$, which should be accessible by the LHCb and Belle II Collaborations.

    hep-phPRD(2025)·1 citation
11. 11*

    Cross Sections and Inelasticity Distributions of High-Energy Neutrino Deep Inelastic Scattering

    Philip L. R. Weigel🇺🇸 · Janet M. Conrad🇺🇸 · Alfonso Garcia-Soto🇪🇸

    This study presents a comprehensive model for neutrino deep inelastic scattering (DIS) cross sections spanning energies from 50 GeV to 5$\times 10^{12}$ GeV with an emphasis on applications to neutrino telescopes. We provide calculations of the total charged-current DIS cross sections and inelasticity distributions up to NNLO for isoscalar nucleon targets and up to NLO order for nuclear targets. Several modifications to the structure functions are applied to improve the modeling of the cross sections at low energies where perturbative QCD is less accurate and at high energies where there is non-negligible top quark production, and small-$x$ logarithms need to be resumed. Using the FONLL general-mass variable-flavor number scheme, we account for heavy quark mass effects and separate the heavy flavor components of the structure functions, obtaining predictions of their relative contributions to the cross sections and the uncertainties arising from the parton distribution functions. Additionally, the effects of final state radiation are implemented in the calculation of the double-differential cross section and discussed in terms of their impact on measurements at neutrino telescopes.

    hep-phastro-ph.HEPRD(2025)·16 citations
12. 12*

    Neutrino Mass Hierarchy and Axion--Lepton Couplings in a Minimal Flavored $\nu$KSVZ Model

    Zhen-Yu Lei🇨🇳 · Jian-Wei Cui🇨🇳

    By treating the PQ symmetry as a flavor symmetry, we construct a minimal flavored axion model by combining the KSVZ axion framework with the type-I seesaw mechanism. This minimal setup introduces flavor-dependent PQ charge assignments and two additional SM singlet scalar fields, leading to a specific zero texture in the inverse Majorana neutrino mass matrix. This texture, together with the observed smallness of ${\theta }_{13}$, predicts an approximate inverted GST-like relation, implying an inverted neutrino mass ordering with $17\lesssim m_1/m_3\lesssim 45$. Assuming no strong hierarchy among the relevant Majorana Yukawa couplings, this ordering is naturally determined by the ratio of the vacuum expectation values of the two SM-singlet scalar fields. This predicted inverted structure is the most readily testable feature of our model, given that current experiments favor the normal ordering. Nevertheless, since the inverted one has not been ruled out, a viable parameter space still remains. We also perform a comprehensive study of the axion--lepton interactions in this framework. The induced axion--neutrino couplings satisfy current astrophysical constraints while potentially affecting neutrino oscillations under suitable conditions. Furthermore, we derive analytical expressions for the axion couplings to charged leptons by evaluating the one-loop radiative corrections in a largely model independent framework and assess the corresponding experimental constraints.

    hep-phNPB(2026)·0 citations
13. 13*

    Construction of Isoscalar $2^{-+}$ Mesonic States Inspired by the $X(2600)$ Discovery

    Li-Ming Wang🇨🇳 · Wen-Xin Tian🇨🇳 · Ting-Yan Li🇨🇳 · Cheng-Xi Liu🇨🇳 · Xiang Liu🇨🇳

    The BESIII observation of the $X(2600)$ suggests that one possible assignment for its spin-parity quantum numbers is $J^{PC}=2^{-+}$. This finding motivates us to systematically revisit isoscalar pseudotensor mesonic states through a comprehensive spectroscopic study. In this work, we employ a potential model to calculate the mass spectrum of isoscalar pseudotensor meson states with varying radial quantum numbers. Additionally, we analyze their strong decay behaviors, as allowed by the Okubo-Zweig-Iizuka (OZI) rule, using the quark pair creation model. Our findings yield valuable information about their resonant parameters and partial decay widths, which can aid in identifying the observed isoscalar pseudotensor states when combined with current experimental data. Importantly, we also predict several radial excitations of isoscalar pseudotensor mesons that remain unobserved experimentally. Furthermore, we exclude the $X(2600)$ from being classified as an isoscalar pseudotensor meson, which is critical for elucidating the properties of the $X(2600)$.

    hep-phhep-exPRD(2024)·9 citations
14. 14*

    Application of partial wave analysis in multiphoton pair production

    Hong-Hao Fan🇨🇳 · Li-Na Hu🇨🇳 · Suo Tang🇨🇳 · Zi-Liang Li🇨🇳 · Bai-Song Xie🇨🇳

    Electron-positron pair production is investigated in the multiphoton regime under polarized fields. Partial wave analysis can be applied to reveal the momentum spectral structure and identify the positions of valleys/peaks of the multiphoton rings by combining with $CP$ conservation. Moreover, considering the spin states of created pairs in partial wave analysis, the particle orbital angular momentum associated with the valleys/peaks can also be identified from multiphoton rings. It is found that the results for angular distribution by this approximate analytical treatment and by the Dirac-Heisenberg-Wigner formalism are consistent with each other. The present results are helpful for understanding the angular momentum information in momentum spectra, and they also have an implication for revealing the vortex structure near the valleys.

    hep-phPRD(2024)·3 citations
15. 15*

    Searching for long-lived light neutralinos and axionlike particles at the SHiNESS experiment

    Zeren Simon Wang🇹🇼 · Yu Zhang🇨🇳 · Wei Liu🇨🇳

    Recently Soleti et al. [JHEP03(2024)148] proposed a new experiment called SHiNESS at the upcoming European Spallation Source (ESS) facility, making use of the 2-GeV proton beam there impinging on a fixed target, in order to search for hidden sterile neutrinos that could lie in different mass ranges and arise with distinct signatures. Such signatures include excesses in electron-positron pairs that may originate from displaced decays of long-lived particles (LLPs). At the ESS, the dominant sources of such LLPs are decays at rest of ${\pi }^{+}$ mesons and ${\mu }^{+}$ leptons. We choose to investigate theoretical scenarios of long-lived light neutralinos in the R-parity-violating supersymmetry and long-lived weak-violating electrophilic axionlike particles, as these LLPs can be produced from decays of ${\pi }^{+}$ and ${\mu }^{+}$. Since the ${\pi }^{+}$'s and ${\mu }^{+}$'s decay at rest at the ESS, we compute the spectra of the therefrom produced LLPs, and thus estimate the expected sensitivity reach of SHiNESS to the LLPs in these two scenarios. Our calculation shows that in multiple relevant benchmark scenarios, SHiNESS can probe large parameter regions of these models beyond the existing bounds, in just a couple of years of data-collection time.

    hep-phhep-exPRD(2024)·5 citations
16. 16*

    Logic and numbers related to solar neutrinos

    L.M.Slad🇷🇺

    In this work, first of all, we analyze a number of hidden aspects of the concept of particle oscillations. The key element of this concept, which do not comply with the principle of least action, is the notion of a mixture of particles, introduced by Gell-Mann and Pais for neutral $K$-mesons. It has been proven that the law of conservation of energy-momentum in the processes of electron neutrino production does not allow solving the problem of solar neutrinos based on the assumption of Gribov and Pontecorvo about their oscillations. It has been established that the consequences of Wolfenstein's equation contradict the results of the SNO and Super-Kamiokande collaborations and that the assertion by Mikheev and Smirnov on the conversion of solar neutrinos is erroneous. Another part of the work is devoted to a logically clear solution to this problem based on the hypothesis of the existence of a new interaction, the carrier of which is a massless pseudoscalar boson, which has a Yukawa coupling with electron neutrinos and nucleons. At each act of interaction of an electron neutrino with the nucleons of the Sun, caused by such interaction, the handedness of the neutrino changes from left to right and vice versa, and also the neutrino energy decreases. The hypothesis provides good agreement between the theoretical and experimental values of the rates of all five observed processes with solar neutrinos. This serves as a significant criterion for both the confidence of such a solution to the problem of solar neutrinos and the confidence of the existence of a new interaction.

    hep-phastro-ph.SRhep-exnucl-thAnnalen Phys.(2024)·2 citations
17. 17*

    Nonperturbative four-gluon vertex in soft kinematics

    A. C. Aguilar🇧🇷 · F. De Soto🇪🇸 · M. N. Ferreira🇨🇳 · J. Papavassiliou🇪🇸 · F. Pinto-Gómez🇪🇸 · J. Rodríguez-Quintero🇪🇸 · L. R. Santos🇧🇷

    We present a nonperturbative study of the form factor associated with the projection of the full four-gluon vertex on its classical tensor, for a set of kinematics with one vanishing and three arbitrary external momenta. The treatment is based on the Schwinger-Dyson equation governing this vertex, and a large-volume lattice simulation, involving ten thousand gauge field configurations. The key hypothesis employed in both approaches is the ``planar degeneracy'', which classifies diverse configurations by means of a single variable, thus enabling their meaningful ``averaging''. The results of both approaches show notable agreement, revealing a considerable suppression of the averaged form factor in the infrared. The deviations from the exact planar degeneracy are discussed in detail, and a supplementary variable is used to achieve a more accurate description. The effective charge defined through this special form factor is computed within both approaches, and the results obtained are in excellent agreement.

    hep-phhep-lathep-thnucl-thPLB(2024)·9 citations
18. 18*

    Boson propagator under rigid rotation; Mode expansion approach

    E. Siri🇮🇷 · N. Sadooghi🇮🇷

    To explore how rigid rotation affects the thermodynamic properties of free relativistic bosons, we employ the standard imaginary time formalism of thermal field theory to calculate the free propagator of complex scalar fields under rotation. We introduce the corresponding partition function and explicitly compute it by expanding the modes in cylindrical coordinates. The resulting propagator is in full agreement with similar findings in the existing literature.

    hep-phmath-phmath.MPTrans.Theor.Math.Phys.(2024)·3 citations
19. 19*

    One-loop impact factors for heavy quarkonium production: $S$-wave case

    Maxim Nefedov🇫🇷

    With the aim to extend the study of inclusive heavy quarkonium production at forward rapidities with the resummation of high partonic center-of-momentum-energy logarithms beyond Leading Logarithmic Approximation (LLA), the explicit analytic results for one-loop corrections to the following impact factors had been obtained: $\gamma R\to Q\bar{Q}\left[{}^1{S}_0^{[8]}\right]$, $gR\to Q\bar{Q}\left[{}^1{S}_0^{[1]}\right]$, $gR\to Q\bar{Q}\left[{}^1{S}_0^{[8]}\right]$ and $gR\to Q\bar{Q}\left[{}^3{S}_1^{[8]}\right]$, with $R$ being the Reggeized gluon and $Q$ is the heavy quark. The computation is done in the framework of Lipatov's gauge-invariant EFT for Multi-Regge processes in QCD with the tilted-Wilson-line regularisation for rapidity divergences. As expected, only single-logarithmic rapidity divergence proportional to the one-loop Regge trajectory of a gluon remains in the final result for impact-factors. Numerical comparison with Regge limits ($s/(-t)\gg 1$) of one-loop QCD amplitudes, described in the paper, provides a strong cross-check of obtained results. The relations of obtained results with other regularisation schemes for rapidity divergences used in low-$x$ physics, such as BFKL scheme, High-Energy Factorisation (HEF) scheme and shockwave scheme, are given.

    hep-phJHEP(2024)·10 citations
20. 20*

    Testing for coherence and nonstandard neutrino interactions in COHERENT data

    Jiajun Liao🇨🇳 · Danny Marfatia🇺🇸 · Jiajie Zhang🇨🇳

    We analyze data from the CsI, liquid Ar and Ge detectors of the COHERENT experiment and confirm within $1.5\sigma$ that the measured elastic neutrino-nucleus scattering cross section is proportional to the square of the number of neutrons in the nucleus, as expected for coherent scattering in the standard model. We also show how various degeneracies involving nonstandard neutrino interaction parameters are broken in a combined analysis of the three datasets.

    hep-phhep-exnucl-exnucl-thPRD(2024)·11 citations
21. 21*

    Dissecting Lepton Number Violating Interactions in the Left-Right Symmetric Model: $0\nu \beta \beta$ decay, Møller scattering, and collider searches

    Gang Li🇨🇳 · Michael J. Ramsey-Musolf🇨🇳 · Sebastián Urrutia Quiroga🇺🇸 · Juan Carlos Vasquez🇺🇸

    In the context of the left-right symmetric model, we study the interplay of neutrinoless double beta ($0\nu \beta \beta$) decay, parity-violating Møller scattering, and high-energy colliders, resulting from the Yukawa interaction of the right-handed doubly-charged scalar to electrons, which could evade the severe constraints from charged lepton flavor violation. The $0\nu \beta \beta$ decay amplitude receives additional contributions from right-handed sterile neutrinos. The half-life, calculated in the effective field theory (EFT) framework, allows for an improved description of the contributions involving non-zero mixing between left- and right-handed $W$ bosons and those arising from exchanging a light right-handed neutrino. We find that the relative sensitivities between the low-energy (or high-precision) and high-energy experiments are affected by the left-right mixing. On the other hand, our results show how the interplay of collider and low-energy searches provides a manner to explore regions that are inaccessible to $0\nu \beta \beta$ decay experiments.

    hep-phnucl-exnucl-thPLB(2026)·8 citations
22. 22*

    On the finite basis topologies for multi-loop high-multiplicity Feynman integrals

    Piotr Bargiela🇨🇭 · Tong-Zhi Yang🇨🇭

    In this work, we systematically analyse Feynman integrals in the `t Hooft-Veltman scheme. We write an explicit reduction resulting from partial fractioning the high-multiplicity integrands to a finite basis of topologies at any given loop order. We find all of these finite basis topologies at two loops in four external dimensions. Their maximal cut and the leading singularity are expressed in terms of the Gram determinant and Baikov polynomial. By performing an Integration-By-Parts reduction without any cut constraint on a numerical probe for one of these topologies, we show that the computational complexity drops significantly compared to the Conventional Dimensional Regularization scheme. Formally, our work implies an upper bound on the rigidity of special functions appearing in the iterated integral solutions at each loop order in perturbative Quantum Field Theory. Phenomenologically, the integrand-level reduction we present will substantially simplify the task of providing high-precision predictions for future high-multiplicity collider observables.

    hep-phPRD(2024)·5 citations
23. 23*

    Thermodynamical string fragmentation and string density effects in jets

    Robert Vertesi🇭🇺 · Antonio Ortiz🇲🇽

    It has been proposed to search for thermal and collective properties arising from parton-fragmentation processes by examining high jet charged-constituent multiplicities ($N_{\mathrm{j},\mathrm{ch}}$) in proton-proton (pp) collisions. This proposal was initially tested using the PYTHIA~8 event generator with the Monash tune, which incorporates multiparton interactions (MPI) and the MPI-based colour reconnection (CR) model. These studies did not reveal any conclusive evidence for the presence of radial flow. In this paper, we expand upon the proposed Monte Carlo study by eliminating selection biases associated with triggering on charged particle multiplicities. Furthermore, MPI are disabled to focus exclusively on jet fragments. We analyse pp collisions at $\sqrt{s}$=13 TeV simulated with PYTHIA~8, exploring different implementations of the generator: thermodynamical string fragmentation and the standard Lund fragmentation model. The impact of colour-string juctions was also explored. Surprisingly, the thermodynamical string fragmentation together with the close-packing of strings mechanism predicts a hint of baryon enhancement in jets. Additionally, the light-flavor baryon-to-meson ratios as a function of $j_{\mathrm{T}}$ exhibit similarities across all PYTHIA~8 implementations, and hint at radial flow-like effects. In contrast, the ratio of heavy-flavor hadrons (\LcToDz) at low $j_{\mathrm{T}}$ as a function of $N_{\mathrm{j},\mathrm{ch}}$ shows a trend similar to that observed as a function of charged-particle multiplicity in minimum-bias data, suggesting that colour-string junctions may play a crucial role in heavy baryon production in jets. The same mechanism also predicts a $j_{\mathrm{T}}$-integrated \LcToDz ratio that increases with increasing $N_{\mathrm{j},\mathrm{ch}}$.

    hep-phPRD(2025)·5 citations
24. 24*

    Production characteristics of light nuclei, hypertritons and $\Omega$-hypernuclei in Pb+Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV

    Rui-Qin Wang🇨🇳 · Xin-Lei Hou🇨🇳 · Yan-Hao Li🇨🇳 · Jun Song🇨🇳 · Feng-Lan Shao🇨🇳

    We extend an analytical nucleon coalescence model with hyperons to study productions of light nuclei, hypertritons and $\Omega$-hypernuclei in Pb+Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV. We derive the formula of the momentum distribution of two bodies coalescing into dibaryon states and that of three bodies coalescing into tribaryon states. We explain the available data of the coalescence factors $B_2$ and $B_3$, the transverse momentum spectra, the averaged transverse momenta, the yield rapidity densities, yield ratios of the deuteron, antihelium-3, antitriton, hypertriton measured by the ALICE collaboration, and give predictions of different $\Omega$-hypernuclei, e.g., $H(p{\Omega }^{-})$, $H(n{\Omega }^{-})$ and $H(pn{\Omega }^{-})$. We find two groups of interesting observables, the averaged transverse momentum ratios of light (hyper-)nuclei to protons (hyperons) and the centrality-dependent yield ratios of theirs. The former group exhibits a reverse-hierarchy of the nucleus size, and the latter is helpful for the judgements of the nucleus production mechanism as well as the nucleus own size.

    hep-phnucl-thNucl.Sci.Tech.(2025)·6 citations
25. 25*

    A Novel Model of Charged Leptons

    Dianfu Wang🇨🇳 · Xiao Liang🇨🇳 · Yanqing Guo🇨🇳

    A novel model of charged leptons is presented, which contains two basics hypotheses. The first hypothesis is that the Yukawa coupling between Higgs field and charged leptons is the weak interaction, the Higgs field is a scalar intermediate boson which changes the chirality of charged leptons in the weak interaction. The other hypothesis is that the flavor eigenstates of charged leptons are the superposition states of left-handed and right-handed elementary Weyl spinors before the electroweak symmetry breaking. According to this model, the Yukawa coupling constants between Higgs field and three generations of charged leptons are considered to be a universal constant, and the difference of the masses of different charged leptons is due to the different left-right mixing angles of their flavor eigenstates.

    hep-ph0 citations
26. 26*

    Renormalization, Decoupling and the Hierarchy Problem

    Kang-Sin Choi🇰🇷

    The hierarchy problem is associated with renormalization and decoupling. We can account for the smallness of the scalar mass against loop corrections and its insensitivity to ultraviolet physics through the decoupling of heavy fields. It is essential to correctly identify the observable physical mass as the renormalized one that depends on the external momentum, as opposed to the constant mass. We reconsider the properties of the renormalized loop corrections, which are finite, independent of regularization and admit a well-defined perturbation. By explicit calculation, we show that any loop corrections to the scalar mass-squared are suppressed as $(p^2-m^2{)}^2/M^2$, where $p,m$ and $M$ are the external momentum, the scalar pole mass and the heavy field mass in the loop, respectively. This is in accordance with the Appelquist-Carazzone decoupling theorem, which we have explicitized and completed for the case of the scalar mass.

    hep-phhep-th8 citations
27. 27*

    On the Validity of Bounds on Light Axions for $f\lesssim 10^{13}$ GeV

    Martin Bauer🇬🇧 · Sreemanti Chakraborti🇬🇧

    Light bosonic dark matter fields that can be treated like a classical wave have non-linear field values close to massive bodies. Here we make the important observation that the quadratic interactions of axion dark matter lead to non-perturbative axion field values for values of the decay constant of $f\lesssim 10^{13}$ GeV and masses $m_a\lesssim 7\times 10^8/f\mathrm{e}{\mathrm{V}}^2$ and generalise this result for axion-like particles. We identify experimental observables impacted by this effect.

    hep-phPRD(2025)·18 citations
28. 28*

    Axion Bounds from Quantum Technology

    Martin Bauer🇬🇧 · Sreemanti Chakraborti🇬🇧 · Guillaume Rostagni🇬🇧

    A consistent treatment of the quantum field theory of an axion-like particle (ALP) interacting with Standard Model fields requires to account for renormalisation group running and matching to the low-energy theory. Quantum sensor experiments designed to search for very light ALPs are particularly sensitive to these effects because they probe large values of the decay constant for which running effects become important. In addition, while linear axion interactions are set by its pseudoscalar nature, quadratic interactions are indistinguishable from scalar interactions. We show how the Wilson coefficients of linear and quadratic ALP interactions are related, including running effects above and below the QCD scale and provide a comprehensive analysis of the sensitivity of current and future experiments. We identify the reach of different experiments for the case of ALP dark matter and comment on how it could be distinguished from the case where it is not the dark matter. We present novel search strategies to observe quadratic ALP interactions via fifth force searches, haloscopes, helioscopes and quantum sensors. We emphasize the nonlinear behaviour of the ALP field close to the surface of the earth and point out which experimental results are independent on the local background field value.

    hep-phJHEP(2025)·21 citations
29. 29*

    Model-independent search for T violation with T2HK and DUNE

    Sabya Sachi Chatterjee🇩🇪 · Sudhanwa Patra🇮🇳 · Thomas Schwetz🇩🇪 · Kiran Sharma🇮🇳

    We consider the time reversal (T) transformation in neutrino oscillations in a model-independent way by comparing the observed transition probabilities at two different baselines at the same neutrino energy. We show that, under modest model assumptions, if the transition probability $P_{{\nu }_{\mu }\to {\nu }_e}$ around $E_{\nu }\simeq 0.86$ GeV measured at DUNE is smaller than the one at T2HK the T symmetry has to be violated. Experimental requirements needed to achieve good sensitivity to this test for T violation are to obtain enough statistics at DUNE for $E_{\nu }\lesssim 1$ GeV (around the 2nd oscillation maximum), good energy resolution (better than 10%), and near-detector measurements with a precision of order 1% or better.

    hep-phJHEP(2024)·3 citations
30. 30*

    On the Origin of Magnetar Fields: Chiral Magnetic Instability in Neutron Star Crusts

    Clara Dehman🇪🇸 · José A. Pons🇪🇸

    We investigate the chiral magnetic instability in the crust of a neutron star as a potential mechanism for amplifying magnetic fields. This instability may become active when small deviations from chemical equilibrium are sustained over decades, driven by the star's gradual spin-down or residual heat loss. Our findings suggest that this mechanism can produce strong, large-scale magnetic fields consistent with models that align with observational data. Additionally, this instability naturally generates magnetic helicity in the star's crust, which is crucial for forming and maintaining strong dipolar toroidal fields, often invoked to explain magnetar observational phenomena. Our results offer a microphysically-based alternative to classical hydrodynamical dynamos for the origin of magnetar magnetic fields, addressing a long-standing debate in the field.

    ↳ astro-ph.HEhep-phhep-th7 citations
31. 31*

    Inner radius and energy conditions of dark matter halos surrounding Schwarzschild black holes

    Zibo Shen🇺🇸 · Anzhong Wang🇺🇸 · Shaoyu Yin🇨🇳

    We study a class of analytic models for a dark matter halo surrounding a Schwarzschild black hole sitting at the center of a galaxy, with a variable inner radius $r_{\text{in}}$ at which the density profile of the dark matter halo vanishes. We examine in detail how the three energy conditions are satisfied in such models. In particular, independent of concrete profile, we find that the three energy conditions are satisfied when $r_{\text{in}}\ge 5M/2$, where $M$ denotes the mass of the black hole. This indicates it is crucial to include inner radius when discussing dark matter distributions. All our solutions expressed explicitly in closed form are particularly valuable for the studies of the gravitational waveforms of extreme/intermediate mass ratio inspirals and the nature of dark matter in galaxies.

    ↳ gr-qcastro-ph.COhep-phPLB(2025)·33 citations
32. 32*

    Covariant Electromagnetism in Past-Light-Cone Formalism

    Daiju Nakayama · Kin-ya Oda🇯🇵 · Koichiro Yasuda🇺🇸

    We present a manifestly covariant formulation of relativistic electromagnetism, focusing on the computation of electromagnetic fields from moving charges in a manifestly Lorentz-covariant manner. The electromagnetic field at a given spacetime point is determined by the motion of point charges at the intersection of their worldlines with the past light cone of the spacetime point, ensuring causal consistency. This formalism provides a manifestly covariant generalization of the Liénard-Wiechert potentials and allows direct implementation on computers. We compare our formulation with standard textbook approaches and analyze its behavior in various physical limits.

    ↳ physics.class-phhep-phphysics.comp-phphysics.ed-ph1 citation
33. 33*

    Interacting Models of Dark Energy and Dark Matter in Einstein scalar Gauss Bonnet Gravity

    Saddam Hussain🇮🇳 · Simran Arora🇮🇳 · Yamuna Rana🇺🇸 · Benjamin Rose🇺🇸 · Anzhong Wang🇺🇸

    We study the dynamics of the interacting models between the Gauss-Bonnet (GB) coupled scalar field and the dark matter fluid in a homogeneous and isotropic background. A key feature of GB coupling models is the varying speed of gravitational waves (GWs). We utilize recent constraints on the GW speed and conduct our analysis in two primary scenarios: model-dependent and model-independent. In the model-dependent scenario, where determining the GW speed requires a specific GB coupling functional form, we choose an exponential GB coupling. We adopt a dynamical system analysis to obtain the necessary constraints on the model parameters that describe different phases of the universe and produce a stable late-time accelerating solution following the GW constraint, and find that to satisfy all these constraints, fine-tuning of the free parameters involved in the models is often needed. In the model-independent scenario, the GW speed is fixed to one, and we construct the autonomous system to identify the late-time stable accelerating critical points. Furthermore, we adopt a Bayesian inference method using late-time observational data sets, including 31 data points from cosmic chronometer data (Hubble data) and 1701 data points from Pantheon+ and find that all the observational constraints can be satisfied without fine-tuning. In addition, we also utilize simulated binned Roman and LSST data to study the evolution of the universe in the model-independent scenario. We find that the model shows significant deviation at higher redshifts from $\Lambda$CDM and fits the current data much better than $\Lambda$CDM within the error bars.

    ↳ gr-qchep-phJCAP(2024)·18 citations
34. 34*

    Electroweak Primordial Magnetic Blackhole: Cosmic Production and Physical Implication

    Y.M. Cho🇰🇷 · Sang-Woo Kim🇰🇷 · Seung Hun Oh🇰🇷

    The electroweak monopole, when coupled to gravity, turns to the Reissner-Nordstrom type primordial magnetic blackhole whose mass is bounded below, with the lower bound $M_P\sqrt{\alpha }$. This changes the overall picture of the monopole production mechanism in the early universe drastically and has deep implications in cosmolpgy. In particular, this enhances the possibility that the electroweak monopoles turned to the primordial magnetic blackholes could become the seed of stellar objects and galaxies, and account for the dark matter of the universe. Moreover, this tells that we have a new type of primordial blackhole different from the popular primordial blackhole in cosmology, the electroweak primordial magnetic blackhole based on a totally different production mechanism. We discuss the physical implications of the electroweak primordial magnetic blackhole.

    ↳ hep-thhep-ph5 citations
35. 35*

    SymTFT for (3+1)d Gapless SPTs and Obstructions to Confinement

    Andrea Antinucci🇮🇹 · Christian Copetti🇬🇧 · Sakura Schafer-Nameki🇬🇧

    We study gapless phases in (3+1)d in the presence of 1-form and non-invertible duality symmetries. Using the Symmetry Topological Field Theory (SymTFT) approach, we classify the gapless symmetry-protected (gSPT) phases in these setups, with particular focus on intrinsically gSPTs (igSPTs). These are symmetry protected critical points which cannot be deformed to a trivially gapped phase without spontaneously breaking the symmetry. Although these are by now well-known in (1+1)d, we demonstrate their existence in (3+1)d gauge theories. Here, they have a clear physical interpretation in terms of an obstruction to confinement, even though the full 1-form symmetry does not suffer from 't Hooft anomalies. These igSPT phases provide a new way to realize 1-form symmetries in CFTs, that has no analog for gapped phases. The SymTFT approach allows for a direct generalization from invertible symmetries to non-invertible duality symmetries, for which we study gSPT and igSPT phases as well. We accompany these theoretical results with concrete physical examples realizing such phases and explain how obstruction to confinement is detected at the level of symmetric deformations.

    ↳ hep-thcond-mat.str-elhep-phSciPost Phys.(2025)·50 citations
36. 36*

    Free Streaming in Warm Wave Dark Matter

    Siyang Ling🇺🇸 · Mustafa A. Amin🇺🇸

    We provide a framework for numerically computing the effects of free-streaming in scalar fields produced after inflation. First, we provide a detailed prescription for setting up initial conditions in the field. This prescription allows us to specify the power spectra of the fields (peaked on subhorizon length scales and without a homogeneous field mode), and importantly, also correctly reproduces the behaviour of density perturbations on large length scales consistent with superhorizon adiabatic perturbations. We then evolve the fields using a spatially inhomogeneous Klein-Gordon equation, including the effects of expansion and radiation-sourced metric perturbations. We show how gravity enhances, and how free streaming erases the initially adiabatic density perturbations of the field, revealing more of the underlying, non-evolving, white-noise isocurvature density contrast. Furthermore, we explore the effect of non-gravitational self-interactions of the field, including oscillon formation, on the suppression dynamics. As part of this paper, we make our code, $\mathsf{Cosmic}-\mathsf{Fields}-\mathsf{Lite}$ ($\mathsf{CFL}$), publicly available. For observationally accessible signatures, our work is particularly relevant for structure formation in light/ultralight dark matter fields.

    ↳ astro-ph.COhep-phJCAP(2025)·19 citations
37. 37*

    Constraining the competition between the deconfinement and chiral phase transitions in light of the multimessenger era

    Wen-Li Yuan🇨🇳 · Bikai Gao🇯🇵 · Yan Yan🇨🇳 · Bo-Lin Li🇨🇳 · Renxin Xu🇨🇳

    We extend the parity doublet model for hadronic matter and study the possible presence of quark matter inside the cores of neutron stars with the Nambu-Jona-Lasinio (NJL) model. Considering the uncertainties of the QCD phase diagram and the location of the critical endpoint, we aim to explore the competition between the chiral phase transition and the deconfinement phase transition systematically, regulated by the vacuum pressure $-B$ in the NJL model. Employing a Maxwell construction, a sharp first-order deconfinement phase transition is implemented combining the parity doublet model for the hadronic phase and the NJL model for the high-energy quark phase. The position of the chiral phase transition is obtained from the NJL model self-consistently. We find stable neutron stars with a quark core within a specific parameter space that satisfies current astronomical observations. The observations suggest a relatively large chiral invariant mass $m_0=600$ MeV in the parity doublet model and a larger split between the chiral and deconfinement phase transitions while assuming the first-order deconfinement phase transition. The maximum mass of the hybrid star that we obtain is $\sim 2.2M_{\odot }$.

    ↳ nucl-thastro-ph.HEhep-phMod.Phys.Lett.A·6 citations
38. 38*

    Modified Trento initial condition and its impact on collective flows and global polarization in Cu+Au collisions

    Ze-Fang Jiang🇨🇳 · Shanshan Cao🇨🇳 · Ben-Wei Zhang🇨🇳

    Collective flow coefficients and spin polarization are valuable probes of the geometry and flow velocity field of the quark-gluon plasma (QGP) produced in relativistic heavy-ion collisions. Using a modified TRENTo initial condition coupled to a (3+1)-dimensional (D) viscous hydrodynamic model CLVisc, we study the directed flow and elliptic flow coefficients of hadrons, together with the global polarization of $\Lambda$ and $\bar{\Lambda }$ hyperons in asymmetric Cu+Au collisions. We extend the 2D TRENTo model to the 3D space, and find that the initial tilted geometry of the QGP fireball with respect to the longitudinal direction leads to a decrease of directed flow from positive to negative values with increasing pseudorapidity, an enhancement of elliptic flow at forward and backward pseudorapidities, and a non-monotonic dependence of global polarization on the transverse momentum of hyperons. The initial longitudinal flow velocity gradient further enhances the values of directed flow and global polarization. Our model calculation provides a satisfactory description of the rapidity, transverse momentum, and centrality dependences of the directed flow of charged hadrons in Cu+Au collisions for the first time, and proposes that such asymmetric heavy-ion collisions create a better environment for studying the initial tilted geometry and longitudinal flow field of the QGP than symmetric Au+Au collisions do.

    ↳ nucl-thhep-phnucl-exPRC(2025)·3 citations
39. 39*

    Gravitational Radiation in Generalized Brans Dicke Theory: Compact Binary Systems

    S. Mahmoudi🇮🇷 · S. H. Hendi🇮🇷

    This paper investigates the generation and properties of gravitational radiation within the framework of Generalized Brans-Dicke (GBD) theory, with a specific emphasis on its manifestation in compact binary systems. The primary focus of this study lies in the comprehensive exploration of gravitational radiation generated by compact binaries. The energy momentum tensor and the associated gravitational wave (GW) radiation power in GBD theory are investigated, elucidating the relationship between these fundamental concepts. Furthermore, detailed calculations are provided for the GW radiation power originating from both tensor fields and scalar fields. Based on our calculations, both scalar fields contribute to GW radiation by producing dipole radiation. We also study the period derivative of compact binaries in this theory. By comparing with the observational data of the orbital period derivative of the quasicircular white dwarf-neutron star binary PSR J1012+5307, we put bounds on the two parameters of the theory: the Brans-Dicke coupling parameter ${\omega }_0$ and the mass of geometrical scalar field $m_f$, \textcolor{black}{resulting in a lower bound ${\omega }_0>6.09723\times 10^6$ for a massless BD scalar field and the geometrical field whose mass is smaller than $10^{-29}\text{GeV}$. The obtained bound on ${\omega }_0$ is two orders of magnitude stricter than those derived from solar system data.} Finally, we find the phase shift that GWs experience in the frequency domain during their propagation.

    ↳ gr-qchep-phEPJC(2024)·4 citations
40. 40*

    Systematic Uncertainties from Gribov Copies in Lattice Calculation of Parton Distributions in the Coulomb gauge

    Xiang Gao🇺🇸 · Jinchen He🇺🇸 · Rui Zhang🇺🇸 · Yong Zhao🇺🇸

    Recently, it has been proposed to compute parton distributions from boosted correlators fixed in the Coulomb gauge within the framework of Large-Momentum Effective Theory. This method does not involve Wilson lines and could greatly improve the efficiency and precision of lattice QCD calculations. However, there are concerns about whether the systematic uncertainties from Gribov copies, which correspond to the ambiguity in lattice gauge-fixing, are under control. This work gives an assessment of the Gribov copies' effect in the Coulomb-gauge-fixed quark correlators. We utilize different strategies for the Coulomb-gauge fixing, selecting two different groups of Gribov copies based on the lattice gauge configurations. We test the difference in the resulted spatial quark correlators in the vacuum and a pion state. Our findings indicate that the statistical errors of the matrix elements from both Gribov copies, regardless of the correlation range, decrease proportionally to the square root of the number of gauge configurations. The difference between the strategies does not show statistical significance compared to the gauge noise. This demonstrates that the effect of the Gribov copies can be neglected in the practical lattice calculation of the quark parton distributions.

    ↳ hep-lathep-phnucl-thChin.Phys.Lett.(2024)·11 citations
41. 41*

    Isotropization by shock waves generation in anisotropic hydrodynamics

    Aleksandr Kovalenko🇷🇺

    Anisotropic hydrodynamics (aHydro) has proven successful in modeling the evolution of quark-gluon matter created in heavy-ion collisions. The hydrodynamic description of quark-gluon plasma has also been widely used to study sound phenomena, such as shock waves. It has recently been shown that initial fluctuations in energy density and supersonic partons can generate fairly strong shock waves. However, significant anisotropic properties of the system due to the rapid longitudinal expansion of matter have not been taken into account in such studies. Moreover, the process of isotropization and its characteristic time-scales were not considered along with the question of the shock waves formation. Previous studies on shock discontinuous solutions in anisotropic hydrodynamics assumed constant anisotropy, leading to flow refraction towards the anisotropy axis and flow acceleration, characteristics of rarefaction waves, indicating limitations in this approach. This paper investigates discontinuous solutions for normal shock waves without flow refraction, introducing two compression parameters for longitudinal and transverse pressures. The resulting analytical solutions, as well as numerical computations, provide an isotropization mechanism of the system.

    ↳ nucl-thhep-phEPJC(2024)·0 citations
42. 42*

    The Connection between the Stochastic Schrödinger Equation and Boltzmann Equation

    Zichao Li🇨🇳 · Xingbo Zhao🇨🇳

    The heavy quarks present in the quark-gluon plasma (QGP) can act as a probe of relativistic heavy ion collisions as they retain the memory of their interaction history. In a previous study, a stochastic Schrödinger equation (SSE) has been applied to describe the transport process of heavy quarks, where an external field with random phases is used to simulate the thermal medium. In this work, we study the connection between the SSE and the Boltzmann equation (BE) approach in the Keldysh Green's function formalism. By comparing the Green's function of the heavy quark from the SSE and the Keldysh Green's functions leading to the Boltzmann equation, we demonstrate that the SSE is consistent with the Boltzmann equation in the weak coupling limit. We subsequently confirm their consistency through numerical calculations.

    ↳ nucl-thhep-phNucl.Phys.Rev.(2025)·0 citations
43. 43*

    Thermal false vacuum decay in (1+1)-dimensions: Evidence for non-equilibrium dynamics

    Dalila Pîrvu🇨🇦 · Andrey Shkerin🇨🇦 · Sergey Sibiryakov🇨🇦

    We numerically study the evolution of a classical real scalar field in $(1+1)$ dimensions with initial conditions describing thermal fluctuations around a metastable vacuum. We track false vacuum decay in real time and compare several observables to the predictions of the standard Euclidean formalism. We find agreement for the shape of the critical bubble and the exponential suppression of the decay rate. However, the decay rate prefactor is almost an order of magnitude lower than the predicted value. We argue that this signals a breakdown of thermal equilibrium during the bubble nucleation. In addition, the inefficient thermalization in the system biases the properties of the statistical ensemble and leads to further decrease of the decay rate with time. We substantiate our interpretation with a suite of stochastic field simulations with controlled thermalization time. Varying this time we find that the predictions of the standard equilibrium formalism are recovered when it is sufficiently short. We propose an upper bound on the thermalization time that must be satisfied in order to ensure the applicability of the Euclidean rate calculation. We discuss that this bound is unavoidably violated in common single-field models, irrespective of the number of spacetime dimensions, implying that deviations from equilibrium in these models cannot be neglected. In theories with multiple fields, the bound may or may not hold, depending on the setup details. We investigate one more signature of non-equilibrium dynamics -- coherent oscillonic precursors to the critical bubble nucleation. We show that they get suppressed in the stochastic dynamical simulations when the thermalization time is reduced.

    ↳ hep-thastro-ph.COcond-mat.stat-mechhep-lat+1Int.J.Mod.Phys.A(2024)·21 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.