HEP Phenomenology·hep-ph
52 papers—34 primary·18 cross-listed·reconstructed*
We renormalize generalized 3-quark operators that relate to baryon states using the method devised by Kränkl and Manashov at four loops in the MSbar scheme. The anomalous dimensions of the four core operators used to compute nucleon matrix elements are determined and their associated critical exponents are studied in the conformal window using the Banks-Zaks expansion.
Carlo Branchina🇮🇹 · Angela Conaci🇮🇹 · Stefania De Curtis🇮🇹 · Luigi Delle Rose🇮🇹
We study how out-of-equilibrium effects modify the steady-state propagation of bubble walls during a cosmological first-order electroweak phase transition. Going beyond the local thermal equilibrium approximation, we numerically solve the coupled system of scalar field, hydrodynamic and Boltzmann equations using a spectral algorithm that allows a first-principle treatment of the collision integral. This approach enables a quantitative assessment of non-equilibrium perturbations in the plasma and their backreaction on the wall motion. Focusing on the singlet extension of the Standard Model as a minimal benchmark scenario, we find that out-of-equilibrium corrections substantially enhance the effective friction on the expanding front, leading to slower wall velocities and broader wall profiles compared to the equilibrium case. These modifications have significant implications for cosmological observables. For instance, they enhance the efficiency of electroweak baryogenesis, thus improving the viability of baryon asymmetry generation within realistic parameter regions that can also be probed by future gravitational wave interferometers.
The low energy effective field theory of interacting neutrinos derived from the Standard Model may be framed as a pointlike interaction and thereby modeled on a lattice of neutrino momenta. We identify a path to take a continuum limit of this lattice problem in the center of momentum frame. In this limit, the weak interaction is found to become trivial between incoming plane waves describing ultrarelativistic particles, unless finite neutrino wave packet sizes are taken into consideration. We follow up with an analytic treatment of interacting neutrino wave packets, demonstrating the importance of the wave packet size for characterizing neutrino-neutrino scattering in dense environments.
Chao-Qiang Geng🇨🇳 · Xiang-Nan Jin🇨🇳 · Chia-Wei Liu🇨🇳 · Xin-Yi Liu🇨🇳 · Xiao Yu🇨🇳
We propose to search for in the decay , which serves as a tagged and reconstructible source of , providing an experimentally clean environment for its discovery. A possible fully charged final state is , where the subscripts indicate the parent hadron in the decay chain. We estimate the branching fraction to be , while the fully charged final state corresponds to an effective branching fraction of order . These results indicate that LHCb has the potential to discover the . The prospects for observing are also briefly discussed.
Francesco Giovanni Celiberto🇪🇸 · Luigi Delle Rose🇮🇹 · Alessandro Papa🇮🇹
We present updated predictions for rapidity and transverse-momentum spectra in Higgs-plus-jet production at proton colliders, combining NLO fixed-order QCD with next-to-leading energy-logarithmic resummation. Preliminary results for the -boson case are also discussed. Our study underscores the importance of improving fixed-order predictions for Higgs- and -plus-jet observables to meet the precision demands of Higgs and electroweak measurements at the LHC and future FCC energies.
Francesco Giovanni Celiberto🇪🇸 · Francesca Lonigro🇪🇸
We present recent progress on the Heavy-Flavor Non-Relativistic Evolution (HF-NRevo) framework, designed to describe leading-power fragmentation of heavy-flavored hadrons at moderate to large transverse momentum. Starting from NLO NRQCD calculations for all partonic channels into pseudoscalar quarkonia, we construct the NRFF1.0 collinear fragmentation functions via DGLAP evolution in a variable-flavor number scheme. We outline future prospects in the heavy-ion context, where HF-NRevo can serve as a baseline for modeling in-medium modifications of heavy-flavor fragmentation in nuclear collisions. Its accurate modeling of the partonic hierarchy and threshold effects makes it ideally suited to explore jet-quenching sensitivity, energy-loss mechanisms, and the emergence of medium-modified fragmentation functions in the quark-gluon plasma. Moreover, it provides a natural baseline for implementing in-medium hadronization scenarios, including quarkonium regeneration and fragmentation-function apparent-shape distortion. These developments provide new handles for exploring heavy-flavor dynamics at the HL-LHC and future collider facilities.
Collisions of protons with lead nuclei (pPb), such as those measured by the LHCb experiment, provide a unique environment to study the surprising emergence of collective, fluid-like phenomena in small systems. A key signature of this hydrodynamic behavior is the predicted formation of a toroidal vorticity structure. In this work, I use two-particle femtoscopic correlations of non-identical hadrons, specifically proton-pion () pairs, as a novel probe for this phenomenon. Previous works indicate that the collective flow of the system is consistent with the formation of a vortex ring created by the passage of the proton through the lead nucleus, which modifies the collective flow profile. I establish that the resulting emission asymmetry between protons and pions, driven by their mass difference and differential response to the vortical flow, is directly linked to the initial vorticity and can be measured using femtoscopy. This method therefore presents a new, sensitive observable for characterizing the rotational dynamics of the matter created in small collision systems.
Zi-Miao Huang🇨🇳 · Changqian Li🇨🇳 · Zuowei Liu🇨🇳
The supernova (SN) core, characterized by its extreme temperature and density, serves as a unique laboratory for new-physics searches. Low-energy supernovae (LESNe) provide particularly powerful probes, as their low explosion energies place stringent limits on any additional energy deposition in the mantle by new particles. We present refined LESN constraints on lepton-flavor-violating (LFV) axions and axion-like particles (ALPs) with electron-muon couplings. We consider four production channels in the SN: muon decay, lepton bremsstrahlung, electron-muon coalescence, and semi-Compton scattering, the last of which is investigated here for the first time in the context of LFV-ALPs. We find that muon decay dominates in the low-mass regime, electron-muon coalescence in the high-mass regime, and semi-Compton scattering in the intermediate-mass range. To derive accurate limits, we compute both the energy transfer from the SN core to the mantle and the energy loss due to ALP production in the mantle, which can be substantial for both large and small couplings -- the latter case, to our knowledge, not previously noted in the literature. We find that LESNe provide the most stringent constraints on the parameter space for ALP masses above MeV. These refined results strengthen previous SN bounds and highlight the exceptional sensitivity of LESNe to LFV new physics.
Zhan Cao🇨🇳 · Zhong-Jun Yang🇨🇳 · Jin-Lei Yang🇨🇳 · Tai-Fu Feng🇨🇳
In this papar, we study the production and decay of a charged Higgs boson, a pseudoscalar Higgs boson, and a boson at the LHC within the flavor-dependent model (FDM), at the LHC. Considering the constraints from perturbative unitarity and experimental measurements (e.g., the flavor physics data, higgs signal strengths, electroweak precision observables), we investigate the relevant processes by analyzing several common LHC search channels. Motivated by the excess in reported by ATLAS, which suggests a charged Higgs boson with a mass near 130 GeV and consistent with B-anomaly expectations, we perform a dedicated simulation for a charged Higgs around this mass. Our results support the experimental hint and predict that this particle has a high discovery potential at the future High-Luminosity Large Hadron Collider (HL-LHC). In contrast, for the pseudoscalar and bosons predicted in our model, they remain beyond the reach of current experiments as well as the expected sensitivity at a 14 TeV collider with an integrated luminosity of 300 fb.
We introduce a mechanism for multi-component dark matter (DM) that originates from axion mixing and present some of its defining properties. In this context, multi-component DM implies that the cold DM is composed of the QCD axion and many ultra-light axion-like particles (ALPs). This framework can be realized in the type IIB string axiverse with hierarchical axion masses and decay constants. Our investigation reveals that in the light QCD axion scenario, the energy density of the lightest ALP often dominates after mixing. On the other hand, in the heavy QCD axion scenario, both the QCD axion and non-lightest ALPs may dominate, depending on the ALP decay constants. Under certain conditions, the QCD axion can dominate the DM budget. Finally, we briefly discuss a theoretical framework featuring axions, with hierarchical axion masses and decay constants.
Raoul Serao🇮🇹 · Gianpaolo Torre🇭🇷 · Antonio Capolupo🇮🇹
This review explores the interplay between quantum information theory and high-energy physics, emphasizing how decoherence effects and unconventional neutrino oscillation patterns may unveil fundamental properties such as the Dirac or Majorana nature of neutrinos and potential CPT violation. It further discusses the use of entanglement measures as novel probes of axion-mediated interactions, outlining interdisciplinary strategies to test the limits of the Standard Model and explore new physics beyond it.
Kshitish Kumar Pradhan🇮🇳 · Dushmanta Sahu🇲🇽 · Raghunath Sahoo🇮🇳
The behavior of vector mesons in extreme environments provides a unique probe of non-perturbative Quantum Chromodynamics. We investigate the conditions for Bose-Einstein condensation (BEC) of spin-1 mesons in dense rotating hadronic matter, a regime relevant to the peripheral heavy-ion collisions and the interiors of rapidly rotating neutron stars. When the meson chemical potential () approaches its effective mass (), a phase transition to BEC occurs. We demonstrate that this transition is non-trivially influenced by global rotation, which couples to the spin of the mesons, leading to a macroscopic spin alignment of the condensate along the axis of rotation. This interplay between condensation and rotation results in distinct polarization patterns, which can serve as a possible signature of a BEC in experiments. The results suggest that rapidly rotating neutron stars may harbor an anisotropic, spin-polarized -condensed phase, which could impact their equation of state.
We analyze the thermal behavior of heavy vector and axial-vector mesons (, , and ) within the finite-temperature QCD sum-rule framework. Using updated PDG-2024 quark masses, modern lattice-informed gluon condensates, and a temperature-dependent continuum threshold constrained by vacuum stability, we compute the evolution of the masses and decay constants up to . At the sum rules are calibrated to reproduce the experimental and LHCb masses and reference decay constants within the expected accuracy of a leading-order phenomenological analysis. The subsequent finite-temperature evolution should therefore be interpreted as a calibrated model prediction within this framework rather than as a fully parameter-free determination. Near the critical temperature, the relative suppression follows a clear hierarchy , consistent with their binding energies and lattice spectral trends. The predicted -- splitting for the system, , is consistent with the LHCb observation of orbitally excited states. The results provide a coherent finite-temperature baseline for future extensions including radiative, higher-dimensional, and width effects.
The QCD axion is investigated within the minimal supersymmetric SO(10) grand unified theory, where the Yukawa sector involves Higgs multiplets and . The relative phase between the VEVs of and under is identified with the axion. The Peccei-Quinn and symmetry breaking scales coincide through . The scalar partner of the lightest right-handed neutrino plays the role of the inflaton, realizing hybrid inflation consistent with the observed CMB density fluctuations. After inflation, both fields acquire VEVs, and the domain-wall problem is resolved through the Lazarides-Shafi mechanism, which naturally restricts the model to three generations.
Qing Chen🇨🇳 · Shuang-Yong Zhou🇨🇳
We develop a general framework for the computation of light portal dark matter direct detection, incorporating a consistent treatment of finite momentum transfer. In this framework, dark matter interacts with Standard Model matter through a light mediator, which simultaneously serves as the force carrier for dark matter self-interaction, potentially with a distinct coupling strength. The corresponding effective theory relevant for detecting this class of dark matter is systematically constructed. Our analysis focuses on light (semi)relativistic dark matter, which may originate from cosmic-ray boosting and can be probed in high threshold experiments such as large-volume neutrino detectors. In this context, the nucleon matrix elements of the effective operators at finite momentum transfer are required, made available through recent advances in lattice QCD and related nonperturbative methods. The relativistic Fermi gas model is used to convert the nucleon-level momentum transfer to the nuclear level, thereby incorporating nuclear effects pertinent to heavy target experiments. To demonstrate the utility of the framework, we present ultraviolet-complete examples featuring spin-1 and spin-2 portal dark matter. For these models, we compute the differential cross sections with respect to momentum transfer, adopting parameter choices that address the so-called core-cusp problem in astrophysical observations via dark matter self-interactions.
Bose-Einstein Condensation (BEC) cosmology is analyzed in the framework of a string-inspired axion model. The dispersion relation of the axionic mode includes both gravitational and self-interaction terms, the latter being small in magnitude but crucial for inducing instability of the condensate. The generation rate of BEC around redshift is primarily governed by gravity, consistent with a phenomenological value eV adopted in previous work and realizable for the QCD axion. The relation between this early BEC epoch and the later formation of supermassive black holes at is also discussed.
I.R. Gabdrakhmanov🇷🇺 · N.A Gramotkov🇷🇺 · A.V. Kotikov🇷🇺 · O.V. Teryaev🇷🇺 · D.A. Volkova🇷🇺 · I.A.Zemlyakov🇨🇱
We investigate the Gross-Llewellyn Smith sum rule within the framework of analytic QCD. A comparison is performed between experimental data, lattice calculations, and perturbative QCD based on conventional and analytic versions of perturbation theory with different parametrizations for the twist-four contribution. We show that conventional perturbation theory fails to reproduce the data, while the analytic version demonstrates good agreement with experiment and lattice calculations. We also discuss the relation between the Gross-Llewellyn Smith sum rule and the Bjorken sum rule.
Fangchao Liu🇨🇳 · Shota Nakagawa🇨🇳 · Yuichiro Nakai🇨🇳 · Yaoduo Wang🇨🇳
The strong CP problem remains one of the most important unresolved issues in the Standard Model. Spontaneous CP violation (SCPV) is a promising approach to the problem by assuming that CP is an exact symmetry of the Lagrangian but broken spontaneously at the vacuum, which enables the generation of the observed Cabibbo-Kobayashi-Maskawa (CKM) phase without reintroducing a nonzero strong CP phase. Supersymmetry (SUSY) provides a natural framework to accommodate such a mechanism, as SUSY can not only protect the scale of SCPV from radiative corrections but also suppress problematic higher-dimensional operators generating a strong CP phase. In the present study, we explore the realization of SCPV in two distinct SUSY scenarios. First, we investigate SCPV in the exact SUSY limit by extending the spurion formalism developed in non-supersymmetric theories to identify the necessary condition for stabilizing CP-violating phases, and by analyzing the stabilization of radial vacuum expectation values through R-symmetry constraints on the superpotential. Second, we construct a model in which CP is spontaneously broken at an intermediate scale along pseudo-flat directions, stabilized by soft SUSY breaking and non-perturbative effects of a gauge theory. The latter setup predicts light scalars in the SCPV sector whose masses are determined by the SUSY breaking scale.
H. Denizli🇹🇷 · A. Senol🇹🇷 · M. Köksal🇹🇷
Rare decays of the Z boson provide a sensitive probe for physics beyond the Standard Model (SM). This study investigates the process within the context of the Tera-Z programmes at future colliders such as the FCC-ee and CEPC. The SM predicts a one-loop branching ratio of for , a value four times smaller than the current experimental limit from the LEP. To explore this window for new physics, we parameterize anomalous interactions using an Effective Field Theory framework, considering both dimension-6 and dimension-8 operators. A detailed simulation is performed by generating signal and background events with MadGraph, modeling particle showers with Pythia, and simulating detector effects with Delphes. The analysis employs key kinematic variables-including the photon energy (), missing transverse energy (), and the missing transverse energy significance () to isolate the signal. The results yield upper limits on the anomalous couplings, from which we infer branching ratios for on the order of . This represents a significant improvement of several orders of magnitude over the LEP sensitivity. Consequently, this study demonstrates the unique potential of the Tera-Z runs not only to test the SM loop-level predictions with unprecedented precision but also to tightly constrain or reveal new anomalous interactions.
Xiao-Yun Wang🇨🇳 · Liu-Lin Wang🇨🇳 · Xiao-Hai Liu🇨🇳 · Qiang Zhao🇨🇳
The BESIII collaboration has recently observed a resonant structure in , whose origin remains unresolved. In this study, we analyze the cross section line shape of by taking into account the state and intermediate charmed meson loops. By treating as both a pure -wave state and - mixed states, and introducing the resonance, we find that the peak at arises from the triangle singularity mechanism in the -mediated rescattering processes, supporting its interpretation as a threshold effect rather than a conventional resonance.
Qing-Hong Cao🇨🇳 · Jian-Nan Ding🇨🇳 · Yandong Liu🇨🇳 · Jin-Long Yuan🇨🇳
We investigate CP-violating effects in electroweak interactions at future high-energy muon colliders within the Standard Model Effective Field Theory (SMEFT) framework. Focusing on four dimension-six CP-odd operators -- -- we analyze vector boson fusion production of and Higgs bosons using CP-odd observables and their asymmetries. With detailed simulations including parton showering, hadronization, and detector effects, we derive exclusion sensitivities through a binned likelihood analysis. For example, at TeV with 2 ab, the coefficient can be constrained at the level, improving to at 10 TeV with 2 ab, and with 10 ab. These results significantly surpass current LHC and projected ILC sensitivities, demonstrating the unique potential of high-energy muon colliders to provide direct and model-independent probes of CP violation in the electroweak sector.
Zhong-Lv Huang🇨🇳 · Xin-Yu Du🇨🇳 · Xiao-Gang He🇨🇳 · Chia-Wei Liu🇨🇳 · Zi-Yue Zou🇨🇳
Among the charged leptons, the electric dipole moment~() is the least constrained. We show that the Im[] imposes strong constraints on new physics that have yet to be discussed. Motivated in particular by the Super Tau-Charm Facility (STCF), which will provide a uniquely clean environment for precision -physics, we study the momentum-transfer dependence of and compare the projected sensitivities of STCF and Belle II. Our analysis shows that an axion-like coupling of the lepton can induce sizable real and imaginary components of the EDM. The predicted EDM values may approach the present experimental sensitivities, making them accessible to future measurements at Belle II and the STCF.
Kai-sa Qiao🇨🇳 · Bing-song Zou🇨🇳
We investigate the production of hyperons, charmed baryons, and potential hadronic molecular states in neutrino-proton reaction, a process characterized by a particularly clean final state. Employing effective Lagrangians, chiral perturbation theory, and a hadronic molecular model, we perform theoretical calculations for several relevant channels, including those leading to the formation of the hadronic molecular candidate and . Our results indicate that future neutrino facilities could serve as a complementary platform for exploring exotic baryonic states and provide valuable insights into the dynamics of strong interactions in the strange and charm sectors.
Yu Yao🇨🇳 · Xuejie Liu🇨🇳 · Xiaoyun Chen🇨🇳 · Yuheng Wu🇨🇳 · Jialun Ping🇨🇳 · Yue Tan🇨🇳 · Qi Huang🇨🇳
In this work, we investigate the resonance structures in the system from both three-quark and five-quark perspectives within the framework of the chiral quark model. An accurate few-body computational approach, the Gaussian Expansion Method, is employed to construct the orbital wave functions of multiquark states. To reduce the model dependence on parameters, we fit two sets of parameters to check the stability of the results. The calculations show that our results remain stable despite changes in the parameters. In the three-quark calculations, two states are obtained with energies around 1.8~GeV, which are good candidates for the experimentally observed and . In the five-quark configuration, several stable resonance states are identified, including , , and . These resonance states survive the channel-coupling calculations under the complex-scaling framework and manifest as stable structures. Our results support the existence of a two-pole structure for the system, predominantly composed of and configurations, analogous to the well-known - (-) system. On the other hand, although the energy of the configuration is close to that of and , the obtained width is not consistent with the experimental values. This suggests that the state needs to mix with three-quark components to better explain the experimental and states. According to our decay width calculations, the predicted two resonance states are primarily composed of and , with their main decay channel being .
Kento Akamatsu🇯🇵 · Takuya Hirose🇯🇵 · Nobuhito Maru🇯🇵 · Akio Nago🇯🇵
We study a six-dimensional U(1) gauge theory compactified on a magnetized torus, where the zero mode of the extra-dimensional gauge field (a Wilson-line (WL) scalar field) plays the role of a pseudo-Nambu-Goldstone (pNG) dark matter (DM) candidate. The pNG DM is naturally included by construction without introducing an additional scalar field. We show that the leading spin-independent DM-nucleus amplitude is suppressed by momentum transfer in our model as expected from the pNG DM model. This suppression allows the model to evade the current severe direct-detection bounds while achieving the observed thermal relic abundance in well-defined regions of parameter space.
Nicholas Miesch🇺🇸 · Edward Shuryak🇺🇸 · Ismail Zahed🇺🇸
In previous papers we developed the light front formulation for Hamiltonians and wave functions (WFs) for mesons and baryons, with both confinement and chiral symmetry breaking. For baryons limited to the lowest Fock component with three quarks, the longitudinal WF is valued in an equilateral triangle with momentum fractions . The WF was developed both numerically and using a basis function that diagonalizes the Laplacian with Dirichlet boundary conditions. In this paper we extend this analysis to quark states, and specialize to pentaquarks (). We determine their masses and WFs, and address the mixing between baryons and pentaquarks, the issue central to understanding the observed antiquark sea of baryons.
Yong-Hui Lin🇩🇪 · Hans-Werner Hammer🇩🇪 · Ulf-G. Meißner🇩🇪
We propose a novel observable for the precision measurements of a wide class of near-threshold dimer states: the short-range production rate of a dimer--spectator two-body system, composed of the given near-threshold state and one of its constituents. Within the framework of nonrelativistic effective field theory, these production rates exhibit characteristic line shapes for the specific partial wave and reach a model-independent minimum. This feature enables a precise extraction of their masses from experimental data, provided that the line shape can be resolved with sufficient accuracy. Applying this novel method to both the and systems allows for a precise determination of the binding energy of the and via the relation of once the respective dip position is experimentally identified.
The FCC-ee phase of a Future Circular Collider is generating great interest due to its versatility, allowing the study of various electroweak thresholds, , , , and . Electroweak precision physics is complemented by flavour physics measurements based on the unprecedented statistics attainable at the pole, and benefiting from the low-background experimental environment (similar to Belle II), and from the production of the full spectrum of hadron species together with large boosts (similar to LHCb). A wide range of measurements is possible, spanning a rich variety of physics cases in both quark and lepton flavour physics sectors. Other electroweak thresholds can also be considered in this endeavour. A commensurate effort from the theory community will be needed to interpret future measurements. I present an overview of the broad potential of the FCC-ee flavour physics program.
Tae Hyun Jung🇰🇷 · Takemichi Okui🇺🇸 · Kohsaku Tobioka🇺🇸 · Jiabao Wang🇺🇸
We study Big Bang Nucleosynthesis (BBN) constraints on heavy QCD axions. BBN offers a powerful probe of new physics that modifies the neutron-to-proton ratio during the process, thanks to the precisely measured primordial Helium-4 abundance. A heavy QCD axion provides an attractive target for this probe, because not only is it a well-motivated hypothetical particle by the strong CP problem, but also it dominantly decays to hadrons if kinematically allowed. A range of its lifetime is thus excluded where the hadronic decays would significantly alter the neutron-to-proton ratio. We compute axion-induced modification of the neutron-to-proton ratio, and obtain robust upper bounds on the axion lifetimes, as low as 0.017 s for the axion mass higher than 300 MeV. Remarkably, this is stronger than projected future CMB bounds via . Our bounds are largely insensitive to uncertainties in hadronic cross sections and the axion's branching fractions into various hadrons, as well as to the precise value of the initial axion abundance. We also incorporate, for the first time, several key improvements, such as scattering processes by energetic and secondary hadrons, that can also be important for studying general hadronic injections during BBN, not limited to those from axion decays.
Elias Bernreuther🇺🇸 · Nicoline Hemme🇩🇪 · Felix Kahlhoefer🇩🇪 · Suchita Kulkarni🇦🇹 · Maksym Ovchynnikov🇨🇭
In models of strongly-interacting dark sectors, the production of dark quarks at accelerators can give rise to dark showers with multiple dark mesons in the final state. If some of these dark mesons are sufficiently light and long-lived, they can be detected with searches for displaced vertices at beam-dump experiments and electron-positron colliders. In this work we focus on the case that dark quark production proceeds via effective operators, while the dark sector analogue of the meson can decay via kinetic mixing. We evaluate current constraints from NA62 and BaBar as well as sensitivity projections for SHiP and Belle II. We find that there exists a sizable parameter region where SHiP may detect several displaced vertices in a single event and thus obtain valuable information about the structure of the dark sector.
Gino Isidori🇨🇭 · Paride Paradisi🇮🇹 · Andrea Sainaghi🇨🇭 · Nudzeim Selimovic🇮🇹
We investigate the neutrino sector in the framework of flavor deconstruction with an inverse-seesaw realization. This setup naturally links the hierarchical charged-fermion masses to the anarchic pattern of light-neutrino mixing. We determine the viable parameter space consistent with oscillation data and study the phenomenology of heavy neutral leptons (HNL) and lepton-flavor-violating (LFV) processes. Current bounds from direct HNL searches and LFV decays constrain the right-handed neutrino scale to a few TeV, while future experiments will probe most of the region with . Among possible realizations, models deconstructing or are those allowing the lowest deconstruction scale.
Rishav Roshan🇬🇧 · Sudipta Show🇮🇳
While most studies of the \textit{minimal type-I seesaw} neglect the heaviest decoupled right-handed neutrino, assuming negligible contributions to neutrino masses and leptogenesis, we demonstrate that its cosmological role can be significant. When long-lived, the presence of this particle can substantially modify the charged lepton Yukawa equilibration temperature in the early universe, necessitating reassessment of lepton flavor effects in thermal leptogenesis and potentially shifting flavor regime boundaries. Additionally, we identify experimental probes, including neutrino oscillation measurements and gravitational wave observations to investigate this scenario. More broadly, the resulting modification of the cosmic expansion history carries implications beyond leptogenesis, impacting dark matter production and evolution, the matter-antimatter asymmetry generation, and the primordial gravitational wave spectrum.
Hooman Davoudiasl🇺🇸 · Peter B. Denton🇺🇸 · Anna M. Suliga🇺🇸
The growing evidence for nano-hertz gravitational waves, from NANOGrav and other observations, may be pointing to a cosmological first-order phase transition at temperatures of . Such an interpretation requires dynamics beyond the Standard Model in this energy range. If so, it may well be the case that core-collapse supernova explosions would recreate the first-order phase transition leaving a unique imprint on the spectrum of neutrinos emitted in the initial few seconds. This scenario is also suggestive of a low-mass seesaw mechanism to explain neutrino masses. We outline the prospects for future observations of Galactic supernovae to uncover the signals of this scenario, which could get further confirmation with additional pulsar timing array data establishing the primordial origin of the observed nano-hertz gravitational waves.
Saiyad Ashanujjaman🇩🇪 · Guglielmo Coloretti🇨🇭 · Andreas Crivellin🇨🇭 · Siddharth P. Maharathy🇿🇦 · Bruce Mellado🇿🇦
The decay is a characteristic signal of two-Higgs-doublet models (2HDMs), where and lie primarily within the same multiplet, leading to a coupling of order to the boson. The subsequent decay is particularly promising, as it gives rise to distinct final states involving multiple leptons and -jets. The required splitting between and can naturally occur near the electroweak scale while being consistent with perturbative unitarity. Whereas dedicated ATLAS and CMS searches focused on the region with both top-quarks on-shell, we cover lower masses where one top quark is off-shell by recasting Standard Model measurements of ATLAS and CMS. The obtained limits on are between pb and pb. Interestingly, we observe these stringent limits despite a preference (up to ) for a non-zero new physics signal, most pronounced around for GeV and GeV, with a best-fit value of pb. This cross section can be accommodated within a top-philic 2HDM for a top-Yukawa coupling of the second Higgs doublet of .
Adam Smith🇬🇧 · Emre Özülker🇹🇷 · Eleonora Di Valentino🇬🇧 · Carsten van de Bruck🇬🇧
We investigate the interplay between varying electron mass () and dynamical dark energy by analysing the Chevallier-Polarski-Linder (CPL) parametrization and its non-crossing variants, both with and without a varying- component. Our aim is to assess whether the preference for late-time dynamics and phantom divide line (PDL) crossing persists when early-time physics is introduced, and whether these combined models improve the alleviation of the Hubble tension compared to the varying- extension alone. Using the latest CMB, BAO, and supernova datasets, we derive updated constraints on CDM, CPL, and their extensions, and examine their impact on and the preference for late-time dynamics. We find that CDM+ yields the largest upward shift in , while replacing with the CPL parametrization or its non-crossing variants provides modest improvements in the overall fit. The data consistently favour dynamical dark energy and a phantom divide line crossing at scale factors , and these preferences remain robust, though somewhat weaker (), when the electron mass is also allowed to vary. Among the late-time models, CPL performs better than its non-crossing variants, further reinforcing the evidence for a genuine phantom divide crossing. The alleviation of the tension in the varying- case arises from late-time data breaking the strong - degeneracy in the CMB, while the additional degrees of freedom in CPL models allow the late-time dynamics to absorb this impact, thereby weakening the degeneracy breaking and further lowering through their ability to yield a decreasing dark energy contribution.
Chengrui Yang🇨🇳 · Weixin Cai🇨🇳 · Taotao Qiu🇨🇳
The Pulsar Timing Array (PTA) data of nano-Hertz gravitational waves released in 2023 implies that if such gravitational waves comes from the scalar perturbation induction at the end of inflation, the accompanied primordial black holes (PBHs) will be over-produced, with the fraction exceed the upper bound of unity. This is recognized as the ``overproduction problem", which calls for nontrivial features in the early universe. In this paper, we try to check out whether a modified dispersion relation (MDR) of the primordial perturbations can be helpful for solving the problem. From the constraint on PTA data, we obtain a posterior distribution of the parameters of primordial perturbation, and find that the MDR model, where the term becomes important at later time, can give rise to a broken-power-law (BPL) power spectrum which can alleviate the overproduction problem to nearly level. However, to improve furtherly into still needs small negative non-Gaussianity, e.g. . The mass distribution of the PBHs generated is also discussed.
Thibeau Wouters🇳🇱 · Anna Puecher🇩🇪 · Peter T. H. Pang🇳🇱 · Tim Dietrich🇩🇪
We study the gravitational-wave trigger GW231109_235456, a sub-threshold binary neutron star merger candidate observed in the first part of the fourth observing run of the LIGO-Virgo-KAGRA collaboration. Assuming the trigger is of astrophysical origin, we analyze it using state-of-the-art waveform models and investigate the robustness of the inferred source parameters under different prior choices in Bayesian inference. We assess the implications for population studies, nuclear physics, and multi-messenger astronomy. Analysing the component masses, we find that GW231109_235456 supports the proposed double Gaussian mass distribution of neutron star masses. Moreover, we find that the remnant most likely collapsed promptly to a black hole and that, because of the large distance, a possible kilonova connected to the merger was noticeably dimmer than AT2017gfo. In addition, we provide constraints on the equation of state from GW231109_235456 alone, as well as combined with GW170817 and GW190425. In our projections for the future, we simulate a similar event using the upcoming generation of gravitational-wave detectors. Our findings indicate that we can constrain the neutron star radius with an accuracy of 400 meters using the Einstein Telescope alone, or 300 meters when combined with the Cosmic Explorer, both at 90% credibility.
The thermal plasma induces a plasmon-like mass shift for gravitational perturbations, which can modify their dynamics near the horizon scale in the early radiation-dominated universe. However, there are several seemingly reasonable ways to introduce this mass shift, reflecting an ambiguity in how one specifies the initial plasma state on a perturbed FLRW background. Invariance under small diffeomorphisms and Weyl rescalings singles out the (grand) canonical ensemble defined in the decoupling limit of gravitational interactions, while excluding ensembles that violate the Weyl identity, including those perturbed by the metric. Large diffeomorphisms further require the mass shift to vanish in the infrared limit. With this consistent choice, primordial tensor modes exhibit stable damping, in agreement with Weinberg's kinetic theory analysis. This cosmological example indicates a more general picture in which local equilibrium in thermal quantum field theory is not an external input but an emergent, dynamical notion.
Jiang-Chuan Yu🇨🇳 · Yan Cao🇨🇳 · Zexin Hu🇨🇳 · Lijing Shao🇨🇳
Ultralight dark matter (ULDM) model is a leading dark matter candidate that arises naturally in extensions of the Standard Model. In the Galactic Center, ULDM manifests as dense hydrogen-like boson clouds or self-gravitating soliton cores. We present the first study of the gravitational effects of these ULDM structures on pulsar orbits around Sgr A*, using pulsar timing as a precision dynamical probe, based on a comprehensive and practical framework that includes various kinds of black hole and orbital parameters. Our analysis shows that long-term pulsar monitoring -- one of the key objectives of future SKA science -- could detect a boson cloud with a total mass as low as for boson mass , and probe a wide range of soliton core masses in the lower-mass regime, assuming a conservative timing precision of .
Ashu Kushwaha🇯🇵 · Rajeev Kumar Jain🇮🇳
In the presence of a background magnetic field, axions or axion-like particles (ALPs) can be resonantly converted to photons when their mass is nearly equal to the effective photon mass. In this paper, we propose a novel method to constrain the parameter space of ALPs by investigating the resulting imprints of axion-photon conversion in the cosmic microwave background (CMB) observations. We show that a helical magnetic field existing prior to the CMB epoch can generate an excess population of photons carrying net circular polarization due to the axion-photon conversion mechanism. Consequently, current measurements of the angular power spectrum of circular polarization (-mode) in the CMB can be used to constrain the parameter space of ALP mass and its coupling to photons. In the optimistic scenario of a maximally helical magnetic field with strength , we find that CLASS observations at can probe the previously unconstrained regions of axion-photon coupling corresponding to ALP masses in the range .
Tomoi Koide🇧🇷 · Armin van de Venn🇪🇪
We show that when a Brownian bridge is physically constrained to satisfy a canonical condition, its time evolution exactly coincides with an m-geodesic on the statistical manifold of Gaussian distributions. This identification provides a direct physical realization of a geometric concept in information geometry. It implies that purely random processes evolve along informationally straight trajectories, analogous to geodesics in general relativity. Our findings suggest that the asymmetry of informational ``distance" (divergence) plays a fundamental physical role, offering a concrete step toward an equivalence principle for information.
We study the dynamics of isolated closed domain walls with 3+1 numerical relativity. A closed wall shrinks due to its own surface tension, and its surface energy is converted to the kinetic energy, leading to implosion. Then, it can result in the formation of a black hole. First, we focus on spherically symmetric closed domain walls and clarify whether they finally evolve into black holes. Naively, the wall can collapse if its thickness is smaller than the Schwarzschild radius which is determined by the initial surface energy. Our numerical results support this naive criterion for the black hole formation, and indicate that more than 80% of the initial wall energy falls into the black hole. We also investigate the nonspherical collapse by considering the ellipsoidal configurations for the closed domain walls, and it turns out that black holes can be formed even when the ratio of semi-major to semi-minor axes is 1.5.
Mason Alexander Ross🇺🇸 · Zi-Wei Lin🇺🇸
It has been challenging to quantitatively understand the stopping of incoming nucleons in nuclear collisions, and recently it has been proposed that comparing the baryon stopping with electric charge stopping can help address the question. Here we focus on the ratio, which can strongly depend on rapidity although its value is one for the full phase space. We find that this ratio is very sensitive to the difference between strange and anti-strange rapidity distributions (the asymmetry), and slightly more anti-strange quarks at mid-rapidity would lead to a ratio well below one. This is the case for Zr+Zr and Ru+Ru isobar collisions at GeV from a multi-phase transport (AMPT) model. Without the asymmetry, the AMPT model would give a mid-rapidity ratio at or above one. In addition, the AMPT model gives at mid-rapidity for isobar collisions at all centralities, which strongly contradicts the recent data from the STAR Collaboration. We further find that the ratio is very sensitive to the net-light quark () stoppings, but it is less sensitive to the asymmetry than the ratio by a factor of 3.
Whereas local field operators play the crucial role in reconciling quantum mechanics and special relativity, they are not trivially compatible with the diffeomorphism invariance of gravity. In order to address this issue, we consider the background geometry which breaks the isometry spontaneously. Then the local gauge invariant operator can be constructed through the Stückelberg mechanism, where the fluctuation of the metric in the direction of the isometry breaking combines with that of matter whose classical solution breaks the isometry. This is equivalent to introducing the clock and the rod to promote the local field operators to the gauge invariant ones. A typical example is the curvature perturbation in quasi-de Sitter space arising from the spontaneous breaking of the timelike isometry. We also discuss the features of the local gauge invariant operator when the spacelike isometry is spontaneously broken. Meanwhile, even if the local gauge invariant operators exist, it does not guarantee the reliable construction of the gauge invariant operators on the local region like the island, which is regarded as an essential ingredient to resolve the black hole information paradox. This is because the fluctuation of the spacetime point is accumulated in time, which in fact also gives rise to eternal inflation in quasi-de Sitter space. In order to suppress the fluctuation at late time, the isometry must be strongly broken by the background. In the case of the evaporating black hole, it may be achieved by the transition to the higher dimensional black hole.
Charmonium is a bound state of a charmed quark and a charmed antiquark, and a charmoniumlike state is a resonant structure that contains at least a charmed quark-antiquark pair but has properties that are incompatible with a conventional charmonium state. The charmoniumlike states are also called XYZ particles to indicate their underlying nature is still unclear. The BESIII experiment has contributed significantly in the study of the XYZ particles, and here we review the discoveries of the Zc(3900), Zc(4020), and Zcs(3985) tetraquark states and the observations of several new vector charmoniumlike states at the BESIII experiment.
Yao Bai🇨🇳 · Cheng-Yang Lee🇨🇳 · Ruifeng Leng🇨🇳 · Siyi Zhou🇨🇳
We establish a new spin-statistics theorem for a class of free pseudo-Hermitian quantum field theories whose particles furnish unitary irreducible representations of the Poincaré group. In this framework, free pseudo-Hermitian fields with integer spin exhibit fermionic statistics, whereas those with half-integer spin exhibit bosonic statistics, opposite to the conventional case. This reversal arises from defining canonical field operators using pseudo-Hermitian conjugation rather than Hermitian conjugation, thereby circumventing the conventional spin-statistics theorem. The free fields retain locality, Lorentz covariance, and unitary evolution. However, interactions may violate unitarity due to the intrinsically non-Hermitian nature of the full Hamiltonian. We discuss potential resolutions to restore unitarity in interacting theories.
Longhua Qin🇨🇳 · Jiancheng Wang🇨🇳 · Chuyuan Yang🇨🇳 · Huaizhen Li🇨🇳 · Quangui Gao🇨🇳 · Ju Ma🇨🇳 · Ao Wang🇨🇳 · Weiwei Na🇨🇳 · Ming Zhou🇨🇳 · Zunli Yuan🇨🇳 · Chunxia Gu🇨🇳 · Guangbo Long🇨🇳
Very-high-energy (VHE; GeV) gamma rays are expected to experience strong attenuation during cosmological propagation due to electron-positron pair production on the extragalactic background light (EBL). Recent observations of GRB 221009A (z = 0.151), including photons up to detected by LHAASO and a event reported by Carpet-3, suggest a higher-than-expected transparency of the Universe at extreme energies. These observations cannot be explained by standard EBL absorption alone; moreover, neither Lorentz invariance violation (LIV) nor photon-axion-like particle (ALP) oscillations, when considered in isolation, appear sufficient to account for the survival of such photons over cosmological distances. In this work, we propose a joint propagation scenario that incorporates photon-ALP mixing in astrophysical magnetic fields together with subluminal quadratic LIV corrections to the pair-production threshold. Applying this framework to the broadband gamma-ray spectrum of GRB 221009A, we show that ALPs with coupling ( ) and mass (), combined with a quadratic LIV energy scale () adopted from the literature, can significantly enhance the photon survival probability in the energy range (10\text{-}300) TeV. The resulting enhancement exceeds that obtained from either ALP mixing or LIV effects alone. These results indicate that a combined ALP-LIV scenario may provide a viable interpretation of the extreme-energy gamma-ray observations of GRB 221009A and highlight the potential of VHE gamma-ray measurements as probes of physics beyond the Standard Model.
Claudio Galelli🇮🇹 · Lorenzo Caccianiga🇮🇹 · Lorenzo Apollonio🇮🇹 · Paolo Magnani🇮🇹 · Vincent Breton🇫🇷
We present a phenomenological study demonstrating the feasibility of using olivine xenoliths from the Chaîne des Puys as a time-resolved paleo-detector array to probe the cosmic-ray flux over the last 40,000 years. This volcanic region provides a unique chronosequence of samples brought to the surface by well-dated eruptions. By modeling the expected density of nuclear recoil tracks induced by cosmic-ray muons in olivine, we show that the signal is detectable and above backgrounds from natural radioactivity. We demonstrate that by analyzing samples with different exposure ages, it is possible to construct a time-differential measurement of the cosmic-ray flux. This method shows sensitivity to historical variations, such as the enhanced flux expected during the Laschamp geomagnetic excursion (41~kyr) and the potential contribution from nearby supernovae, for which we use the Antlia supernova remnant precursor as a benchmark. This work establishes a new application of the paleo-detector technique for long-scale time-domain high-energy astrophysics and provides the direct scientific motivation for experimental efforts to measure these track records.
Giacomo D'Amico🇪🇸 · Michele Doro🇮🇹 · Michela De Caria🇮🇹
We present a novel method for both forecasting and recasting upper limits (ULs) on dark matter (DM) annihilation cross sections, , or decay lifetime . The forecasting method relies solely on the instrument response functions (IRFs) to predict ULs for a given observational setup, without the need for full analysis pipelines. The recasting procedure uses published ULs to reinterpret constraints for alternative DM models or channels. We demonstrate its utility across a range of canonical annihilation channels, including , , , and , and apply it to several major gamma-ray experiments, including MAGIC, \textit{Fermi}-LAT, and CTAO. Notably, we develop a recasting approach that remains effective even when the IRF is unavailable by extracting generalized IRF-dependent coefficients from benchmark channels. We apply this method to reinterpret ULs derived from standard spectra (e.g., PPPC4DMID) in terms of more recent DM scenarios, including a Higgsino-like model with mixed final states and spectra generated with the CosmiXs model. Extensive Monte Carlo simulations and direct comparison with published results confirm the robustness and accuracy of our method, with discrepancies remaining within statistical uncertainties. The algorithm is generally applicable to any scenario where the expected signal model is parametric, offering a powerful tool for reinterpreting existing gamma-ray limits and efficiently exploring the DM parameter space in current and future indirect detection experiments.
Jan Steinheimer🇩🇪 · Tom Reichert🇩🇪 · Marcus Bleicher🇩🇪
Nuclear experiments near and below the threshold of hyperon production have shown that the production of Kaons is a sensitive probe for the dense QCD equation of state. At beam energies up to 1.5AGeV, strangeness production can probe the equation of state for densities up to approximately twice nuclear saturation. In this paper we will discuss the possibilities of extending this range in density by the study of multi-strange baryons as well as charmed hadrons in the SIS100 beam energy range up to GeV. Here, densities up to five times nuclear saturation can be reached and the production of multi-strange and charmed hadrons shows a strong sensitivity to the equation of state. On the other hand a precise prediction of the effect of the equation of state will require knowledge of the fundamental production cross section near the elementary production threshold in p+p collisions which is yet not measured for the hadrons discussed.
C. E. P. Robin🇩🇪 · M. J. Savage🇺🇸
Non-local non-stabilizerness and anti-flatness provide a measure of the quantum complexity in the wavefunction of a physical system. Supported by entanglement, they cannot be removed by local unitary operations, thus providing basis-independent measures, and sufficiently large values underpin the need for quantum computers in order to perform precise simulations of the system at scale. Towards a better understanding of the quantum-complexity generation by fundamental interactions, the building blocks of many-body systems, we consider non-local non-stabilizerness and anti-flatness in two-particle scattering processes, specifically focusing on low-energy nucleon-nucleon scattering and high-energy Moller scattering. We find that the non-local non-stabilizerness induced in both interactions is four times the anti-flatness (which is found to be true for any two-qubit wavefunction), and verify the relation between the Clifford-averaged anti-flatness and total non-stabilizerness. For these processes, the anti-flatness is a more experimentally accessible quantity as it can be determined from one of the final-state particles, and does not require spin correlations. While the MOLLER experiment at the Thomas Jefferson National Accelerator Facility does not include final-state spin measurements, the results presented here may add motivation to consider their future inclusion.
Marc Kamionkowski🇺🇸 · Kris Sigurdson🇨🇦
Self-gravitating galactic halos composed of self-interacting dark matter exhibit the formation of a highly dense core at the galactic center--a gravothermal collapse. Analytic models to describe this evolution have been developed and calibrated to numerical simulations initialized with isotropic particle velocity distributions, an assumption not necessarily warranted by the theory of halo formation. Here we study the dependence of the timescale for gravothermal collapse on the velocity distribution. To do so, we consider self-consistent initial conditions for halos with the same density distribution but with different velocity distributions. We consider models with constant anisotropy and with an anisotropy that increases with radius. The velocity distributions that we explore have collapse times that differ from that assuming isotropic distributions by more than a factor of two. We argue that these variations may depend on the global changes in velocity-dispersion profiles in these anisotropic models and not just on the degree of anisotropy.
* 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.