Showing new listings for Monday, 10 November 2025

New submissions (showing 16 of 16 entries)

In this short note we analyze the inflationary dynamics in Weyl-invariant Einstein-Cartan gravity coupled to the Standard Model of particle physics. We take the axion-like particle of gravitational origin to be approximately massless in the early Universe and show how inflation with the Higgs field materializes.

Algorithms for computing neutrino oscillation probabilities in sharply varying matter potentials such as the Earth are becoming increasingly important. As the next generation of experiments, DUNE and HyperK as well as the IceCube upgrade and KM3NeT, come online, the computational cost for atmospheric and solar neutrinos will continue to increase. To address these issues, we expand upon our previous algorithm for long-baseline calculations to efficiently handle probabilities through the Earth for atmospheric, nighttime solar, and supernova neutrinos. The algorithm is fast, flexible, and accurate. It can handle arbitrary Earth models with two different schemes for varying density profiles. We also provide a c++ implementation of the code called NuFast-Earth along with a detailed user manual. The code intelligently keeps track of repeated calculations and only recalculates what is needed on each successive call which can also help provide significant speed-ups.

There is an increasing interest in the community for the Neutron Stars and what we can learn from them. In this review we show how chiral effective field theory, combined with many-body methods, can provide important results that connect Neutron Star properties at zero temperature to nuclear physics and allows to use these compact objects as laboratories of new physics.

Cosmological determinations of the number of relativistic neutrino species, N^{ }_{rm eff}, are becoming increasingly accurate, and further improvements are expected both from CMB and BBN data. Given this context, we update the evaluation of N^{ }_{rm eff} and the current entropy density via the momentum-averaged approach. This allows for a numerically fast description of neutrino decoupling, easily portable to an array of new physics scenarios. We revisit all aspects of this approach, including collision terms with full electron mass dependence, finite temperature QED corrections to the equation of state, neutrino oscillations, and the modelling of neutrino ensembles with effective chemical potentials. For integrated observables, our results differ by less than 0.04% from the solution of the momentum-dependent evolution equation. We outline how to extend the approach to BSM settings, and will highlight its power in Part II. To facilitate the practical implementation, we release a Mathematica and Python code within nudec_BSM_v2, easily linkable to BBN codes.

Precision calculations in hadronic processes at high energy colliders are crucial for improving the understanding of the standard phenomena as well as for the discovery of new physics. Spinor-helicity formalism serves as one of the most efficient ways to simplify the calculations of S matrix elements. In this article, we compute the S matrix elements for the process qBar{q}rightarrow qBar{q}g mediated by photon and gluon. Ignoring the contribution of Z boson exchange, we show that the calculation of S matrix elements for this process simplifies to a great extent by using spinor-helicity formalism.

Low mass particles with small electric charges can be produced abundantly in large electric fields via the Schwinger effect. We study the production rate of such particles inside the polar gap of nearby pulsars. After production they are accelerated above MeV energies by the local electric fields. These pulsar-produced millicharged particles can be detected at Earth in low-threshold dark matter direct detection experiments. We find that the current XENONnT data constrains millicharged particles produced in the Crab pulsar to have charges less than O(10^{-6}) for sub-eV masses.

We analyze the excesses at 95 GeV in the light Higgs-boson searches in the di-photon decay channel reported by CMS and ATLAS, which combined are at the level of three standard deviations and are compatible with the excess in the bbar{b} final state observed at LEP, together with an excess in the di-photon channel at around 152 GeV reported based on a sideband analysis. We demonstrate that these excesses can be well described in a minimally extended Georgi-Machacek (meGM) model. This is enabled by four key features of the meGM model: (1) a natural prediction for scalar boson masses of lesssim200 GeV arising from the condition to describe both the Higgs boson signal at 125 GeV and the excesses at 95 GeV, (2) the prediction for a doubly charged Higgs boson that can potentially enhance the di-photon decay rates, (3) asymmetric WW and ZZ couplings to neutral scalar bosons that are induced by mild custodial symmetry breaking, and (4) the approximate preservation of the electroweak rho parameter to be 1 at tree level. We show in our numerical analysis that the meGM model naturally improves the fit to the LHC data around 152 GeV when describing the excesses at 95 GeV. At the same time, the model also predicts additional light CP-odd and charged scalar bosons that can be potentially probed in future experiments, which motivates dedicated searches in the upcoming LHC runs. We also present the results of sensitivity studies for the 95 and 125 GeV Higgs-boson couplings at the HL-LHC and future e^+e^- colliders, which demonstrate very interesting prospects for probing the meGM model at future colliders.

We calculate inclusive B-meson decay rates in the Mesogenesis framework, a model explaining baryogenesis and the existence of dark matter, using the Heavy Quark Expansion (HQE), up to the dimension-six two-quark Darwin term. By systematically studying the power-suppressed contributions, we identify regions of parameter space where subleading terms exceed the leading contribution, i.e., the free b-quark decay, highlighting the limits of the HQE in this BSM scenario. This behavior is reminiscent of the Standard Model only under artificially heavy charm masses, and can be used to study the HQE close to its breakdown. We further update the lower bounds on the exclusive decay mode B^+ to p^+ psi by incorporating the fully HQE-corrected inclusive width in the ratio Gamma_{mathrm{excl}}/Gamma_{mathrm{incl}}. Extending the analysis from total decay rates to the lifetime ratio tau(B_s)/tau(B_d), we find no additional constraints on the couplings beyond existing collider bounds, consistent with analogous results for tau(B^+)/tau(B_d). We further compare the sensitivity of both lifetime ratios.

We investigate dark matter (DM) phenomenology and cosmic inflation within a unified framework based on a dark U(1)_D gauge extension of the Standard Model (SM). The associated dark gauge boson, namely the dark photon, serves as a viable DM candidate, which we call dark photon dark matter (DPDM), whilst the dark Higgs field drives inflation. We explore a low-reheating scenario where DM production occurs during reheating, resulting in significant entropy dilution of the DPDM abundance. Both weakly interacting massive particle (WIMP) and feebly interacting massive particle (FIMP) DM scenarios are explored, depending on the dark gauge coupling strength. For FIMP-type DM, the entropy dilution allows for stronger couplings whilst maintaining the correct relic abundance, potentially bringing these candidates within the reach of current and near-future detection experiments. Similarly, WIMP-type DM can be realised with weaker couplings. We perform a comprehensive parameter scan incorporating constraints from collider data, DM direct and indirect detection experiments, and cosmological observations. Taking quantum corrections and running of the couplings into account, we demonstrate that dark Higgs inflation yields predictions for the spectral index n_s and the tensor-to-scalar ratio r that are consistent with the Planck, BICEP/Keck, and ACT data. The nonminimal coupling of the dark Higgs inflaton field to gravity is shown to be much smaller than in the case of the SM Higgs inflation scenario, avoiding unitarity concerns. We show that reheating temperatures as low as 1 GeV and 1 MeV can be achieved through the decay and scattering processes of the inflaton, respectively, with the latter allowing for larger Higgs mixing angles and enhanced detection prospects. Our results establish that this minimal extension successfully unifies DM physics with inflationary cosmology.

Recent CMS analyses report an excess in the diphoton-plus-b bar{b} channel, indicative of a heavy resonance around 650 GeV decaying into a Standard Model (SM)-like Higgs boson and a lighter scalar near 95 GeV. The case for a 95 GeV state is further supported by diphoton excesses observed by both CMS and ATLAS, as well as a bbar{b} excess previously observed at the Large Electron-Position collider. This study present a unified interpretation of these anomalies within the framework of the General Next-to-Minimal Supersymmetric Standard Model that naturally accommodates a light singlet-dominated CP-even scalar boson near 95 GeV and an heavier doublet-like scalar boson near 650 GeV. Through a comprehensive scan of the parameter space, we demonstrate that the model can explain these excesses at 2sigma level while satisfying constraints from the dark matter relic density, direct detection experiments, the properties of the 125 GeV Higgs boson, B-physics observables, and searches for electroweakinos at the Large Hadron Collider (LHC). The interpretation features a Bino-dominated lightest neutralino as the dark matter candidate, whose relic abundance is achieved primarily via A_s funnel annihilation or coannihilation with tilde{S}-like tilde{chi}^0_2s into h_sA_H final states. Our findings provide clear predictions for testing this scenario at the high-luminosity LHC and future colliders.

In this study, we employ a conventional deep neural network (NN) framework integrated with physics-based constraints to predict charged hadron multiplicity (N_{text{ch}}) in heavy-ion collisions. The goal is to assess the performance of a purely data-driven deep neural network in comparison to a physics-informed neural network (PINN). To accomplish this, we have taken data generated from the HYDJET++ model for testing and training purposes. We train our neural network frameworks using the data of one million individual ^{96}_{40}text{Zr}+^{96}_{40}text{Zr} collision events. Our PINN model successfully extracts the hard-scattering fraction (x) by learning its underlying relation from the event data. For further testing and comparison with the conventional NN, we take data of ^{96}_{44}text{Ru}+^{96}_{44}text{Ru} (isobar of Zr) and ^{197}_{79}text{Au}+^{197}_{79}text{Au} collisions using the same simulation model. We found that the NN model needs more time to train with physics. However, once trained, the PINN model is capable of accurately predicting data that it has not encountered during training, such as Au+Au collision results. Especially in a region of sparse data corresponding to high N_{text{ch}} in our study, PINN has a clear advantage over a simple NN.

We explore the observational consequences of resonant particle production during inflation, focusing on its impact on dark matter annihilation signals today. A transient burst of particle production generates localised features in the primordial power spectrum, enhancing the formation of compact small-scale dark matter structures known as prompt cusps. If dark matter consists of thermal WIMPs, the resulting small-scale structures substantially boost annihilation rates, leaving potentially detectable imprints in gamma-ray observations. Using 15 years of Fermi-LAT data targeting the Virgo cluster, we derive upper limits on the thermally averaged annihilation cross section langle sigma v rangle, connecting inflationary particle production in the early universe with present-day observations constraining dark matter annihilation.

The weak interactions of neutrinos with other Standard Model particles are well described within the Standard Model of particle physics. However, modern accelerator-based neutrino experiments employ nuclei as targets, where neutrinos interact with bound nucleons, turning a seemingly simple electroweak process into a complex many-body problem in nuclear physics. At the time of writing this Encyclopedia of Particle Physics chapter, neutrino-nucleus interactions remain one of the leading sources of systematic uncertainty in accelerator-based neutrino oscillation measurements.This chapter provides a pedagogical overview of neutrino interactions with nuclei in the medium-energy regime, spanning a few hundred MeV to several GeV. It introduces the fundamental electroweak formalism, outlines the dominant interaction mechanisms - including quasielastic scattering, resonance production, and deep inelastic scattering - and discusses how nuclear effects such as Fermi motion, nucleon-nucleon correlations, meson-exchange currents, and final-state interactions modify observable cross sections. The chapter also presents a brief survey of the foundational and most widely used theoretical models for neutrino-nucleus cross sections, together with an overview of current and upcoming accelerator-based neutrino oscillation experiments that are shaping the field.Rather than targeting experts, this chapter serves as a primer for advanced undergraduates, graduate students, and early-career researchers entering the field. It provides a concise foundation for understanding neutrino-nucleus scattering, its relevance to oscillation experiments, and its broader connections to both particle and nuclear physics.

We present a novel robust framework for systematically constructing D-dimensional four-point higher-derivative contact amplitudes. Our modular block ("LEGO"-like) approach builds amplitudes directly from manifestly gauge-invariant kinematic blocks, color-weight factors, and scalar Mandelstam polynomials. Symmetries (Bose/Fermi) are imposed algebraically, acting as filters on combinations of compatible pieces. This framework operates entirely in D dimensions, naturally incorporating evanescent operators crucial for loop-level consistency. Scaling to arbitrary mass dimension is achieved in a highly controlled manner using permutation-invariant scalar polynomials, avoiding combinatorial explosion. A key feature is its manifest compatibility with the double-copy program, allowing the systematic generation of operator towers not only for gauge theories but also for gravity and other theories within the double-copy web.

Superallowed (0^+rightarrow0^+) beta decays currently provide the most precise extraction of quark mixing in the Standard Model. Their interpretation as a measurement of |V_{ud}| relies on a reliable first-principles computation of QED radiative corrections expressed as a series in Zalpha and alpha. In this work, we provide the first model-independent result for two-loop, O(Zalpha^2), long-distance radiative corrections where the nuclei are treated as heavy point-like particles.We use renormalization group analysis to obtain new results at O(Zalpha^3) for the coefficient of double-logarithms in the ratio of the maximal beta energy to the inverse nuclear size, Em/R^{-1}. We use the Kinoshita-Lee-Nauenberg theorem to obtain new results at O(Z^2alpha^3) for the coefficient of logarithms in the ratio of maximal beta energy to the electron mass, log(2Em/me). We identify a structure-dependent, and therefore short-distance, contribution to the traditional Zalpha^2 correction that should be revisited.. We provide the first comprehensive update to the long-distance corrections in almost forty years and comment on the impact of our findings for extractions of |V_{ud}|. We find that shifts in the long-distance corrections are 2.5times larger than past estimates of their uncertainty, 1.5times larger than the statistical uncertainty from the combined fit of superallowed decays, and about 1/2 the size of estimated systematic error, which stems dominantly from nuclear structure effects.

We compute mathcal O(alpha^2 Z) radiative corrections to superallowed beta decays with a heavy-particle effective field theory that systematically describes the interactions of low-energy ultrasoft photons with nuclei. We calculate two-loop virtual and one-loop real-virtual amplitudes by reducing the Feynman integrals to a set of master integrals, which we solve analytically using a variety of techniques. These techniques can be applied to other phenomenologically interesting observables. The ultrasoft corrections can then be combined with contributions arising from the exchange of potential photons to obtain the complete mathcal O(alpha^2 Z) correction to the decay rate, with resummation of large logarithms of the electron energy times the nuclear radius. We find that mathcal O(alpha^2 Z) ultrasoft loops induce a relative correction to the decay rate that ranges from 0.7 cdot 10^{-3} in the decay of ^{10}C to 3.6 cdot 10^{-3} in the decay of ^{54}Co, and will thus impact the extraction of V_{ud} at the permille level. We show that the inclusion of these corrections reduces the residual renormalization scale dependence of the decay rate to a negligible level, making missing ultrasoft perturbative corrections a subdominant source of theoretical error.

Cross submissions (showing 5 of 5 entries)

We study the cosmology of axions in the post-inflationary scenario, where random initial conditions and the ensuing string-domain-wall network generate an isocurvature power spectrum. Axions radiated from strings behave as warm, wave-like dark matter: when they constitute the full dark matter abundance, free streaming sets the strongest bounds on their mass. For subdominant fractions, despite being warm, they still lead to an overall enhancement of structure growth in the dominant component, seeded by the axion white-noise fluctuations. We search for this effect using the ultraviolet luminosity function (UVLF) of galaxies at z=4-10, probing ksimeq0.5-10,mathrm{Mpc}^{-1}. Combining the UVLF analysis with Lyman-alpha and CMB data yields the leading cosmological limits on post-inflationary axion dark matter, sensitive to tiny fractions for m_alesssim10^{-21},mathrm{eV}. As a byproduct, we obtain new constraints on generic white-noise power spectra from the UVLF. These results apply broadly to scenarios that generate similar isocurvature perturbations, linking early-universe field dynamics to high-redshift structure formation.

We study QCD on AdS space with scalars or fermions in the fundamental representation, extending earlier results on pure Yang-Mills theory. In the latter, the Dirichlet boundary condition is conjectured to disappear via merger and annihilation, as signaled by the lightest scalar singlet operator approaching marginality as the coupling increases. With matter, there are two candidate operators for this mechanism. We compute their one-loop anomalous dimensions via broken conformal Ward identities and Witten diagrams. In the confining phase, with Dirichlet (Neumann) boundary condition, their anomalous dimensions are negative (positive), consistent with the disappearance (persistence) of the associated boundary CFT in the flat-space limit. In the conformal window, one of these operators becomes the displacement operator of the IR CFT, as signaled by the vanishing of its one-loop anomalous dimension in the perturbative Banks-Zaks regime. Possible scenarios for the lower edge of the conformal window are discussed. Finally, we consider general boundary conditions on fermions and discuss their relation to chiral symmetry breaking in flat space.

The Lorentz invariance violation (LIV) predicted by some quantum gravity theories would manifest as an energy-dependent speed of light, which may potentially distort the observed temporal profile of photons from astrophysical sources at cosmological distances. The dispersion cancellation (DisCan) algorithm offers a powerful methodology for investigating such effects by employing quantities such as Shannon entropy, which reflects the initial temporal characteristics. In this study, we apply the DisCan algorithm to search for LIV effects in the LHAASO observations of GRB 221009A, combining data from both the WCDA and KM2A detectors that collectively span an energy range of sim 0.2-13 TeV. Our analysis accounts for the uncertainties from both energy resolution and temporal binning. We derive 95% confidence level lower limits on the LIV energy scale of E_{rm{QG}}/10^{19}~text{GeV}>21.1 (13.8) for the first-order subluminal (superluminal) scenario, and E_{rm{QG}}/10^{11}~text{GeV}> 14.9 (13.7) for the second-order subluminal (superluminal) scenario.

We present a non-perturbative framework for the dynamics of slow-roll inflation that consistently incorporates quantum corrections, based on an alternative functional renormalisation group (RG) approach. We derive the coupled Friedmann-RG flow equations governing the joint evolution of spacetime, the inflaton field, and its effective potential. Applying this formalism to alpha-attractor E-models, we find that the RG flow induces a dynamical destabilisation of the inflationary trajectory, leading to a premature termination of slow roll. Remarkably, the resulting predictions bring alpha-attractors into full agreement with the latest ACT data without introducing new physics beyond a consistent quantum-corrected treatment of the inflaton dynamics.

We propose a resolution to the longstanding problem of perturbative normalizability in canonical quantum gravity of the Lorentzian Chern-Simons-Kodama (CSK) state with a positive cosmological constant in four dimensions. While the CSK state is an exact solution to the Hamiltonian constraint in the self-dual formulation and semiclassically describes de Sitter spacetime, its physical viability has been questioned due to apparent nonnormalizability and CPT asymmetry. Starting from a nonperturbative holomorphic inner product derived from the reality conditions of the self-dual Ashtekar variables, we show that the linearization, in terms of gravitons, of the CSK state is perturbatively normalizable for super-Planckian cosmological constant. Furthermore, we demonstrate that a rotation in phase space, a generalization of Thiemann's complexifier, can render the full perturbative state normalizable for all Lambda by analytically continuing the non-convergent modes in phase space. This provides the first concrete realization of a CPT-breaking, yet normalizable, gravitational vacuum state rooted in a nonperturbative quantum gravity framework. Our results establish the CSK state-long thought formal-as a viable candidate for the ground state of quantum gravity in de Sitter space.

Replacement submissions (showing 23 of 23 entries)

We present a detailed technical derivation of matching conditions at next-to-next-to-leading order in the sectorised VINCIA parton shower, by considering leading-colour 2-, 3- and 4-jet rates in hadronic Z-boson decays. In particular, we introduce a full subtraction-based calculation of the matching coefficient required to obtain the NLO 3-jet rate. This is achieved through a judicious choice of the counter-terms, which optimises the numerical evaluation of the subtracted double-real matrix element. We additionally give a consistent prescription for incorporating interference effects due to higher-order mixing between Born states with different flavour contents. Finally, we briefly comment on higher-order uncertainty estimates.

In this paper we present updated constraints on the top-quark sector of the Standard Model Effective Field Theory using data available from Tevatron, LEP and the LHC. Bounds are obtained for the Wilson coefficients from a global fit including the relevant two-fermion operators, four-quark operators and two-quark two-lepton operators. We compare the current bounds with the prospects for the high luminosity phase of the Large Hadron Collider and future lepton colliders.

The perturbative result for the quark-mass conversion factor between the overline{mathrm{MS}} and regularization-independent symmetric-momentum subtraction scheme (RI/SMOM) away from the chiral limit, i.e. at non-zero quark masses (RI/mSMOM), is derived up to three loops in QCD, extending the existing result by two additional orders. We further explore an illuminating possibility that in Dimensional Regularization, the original RI/(m)SMOM renormalization conditions may be interpreted merely in a weaker sense, namely as equations holding just in the 4-dimensional limit rather than exactly in d dimensions: they result in different, albeit simpler, renormalization constants but still the same finite conversion factor. This novel observation has the added benefit of reducing computational effort, particularly at high orders. Our high-order results for the conversion factor exhibit rich behaviors, and in particular a window is observed in the subtraction scale and mass where it receives less perturbative corrections than the RI/SMOM counterpart up to three loops; this finding may help to further improve the accuracy of overline{mathrm{MS}} quark-mass determinations with Lattice QCD.

New heavy resonances with sizeable couplings to top quarks can be probed through searches for beyond-the-Standard-Model effects in four-top production at the LHC. In this work, we present the first next-to-leading-order QCD predictions for the full on-shell and off-shell production of four-top events via new electroweak singlet states, along with dedicated analysis strategies based on the reconstruction and tagging of all final-state top quarks. We develop a detector-level simulation incorporating recent advances in top-tagging and boosted object reconstruction. Moreover, we demonstrate that searches at LHC Run 3 and high-luminosity phase in the zero-lepton, one-lepton and same-sign di-lepton channels can improve the sensitivity to the new physics cross sections by up to two orders of magnitude. In particular, colour-octet resonances with masses up to 2-2.5 TeV and colour-singlet states with masses up to 1-1.5 TeV are within reach for coupling values in the 0.1-1 range.

We present a model-independent extraction of the phi-4He scattering length from near-threshold phi photoproduction on helium-4, based on LEPS Collaboration data for the coherent process gamma + 4He -> phi + 4He and the Vector Meson Dominance framework. Assuming an energy-independent differential cross section, we extract the absolute value of the phi-4He scattering length |alpha_{phi4He}| = (3.33 +- 0.06) x 10^{-4} fm from a fit at threshold t_thr. This value is orders of magnitude smaller than those for phi-N and phi-d scattering lengths, indicating an inverse dependence of |alpha_VA| on the target nucleus mass. Our results provide new insight into the phi-nucleus interaction, supporting the notion of weak phi-nucleus coupling. We further explore the dependence of |alpha_VA| on the vector meson mass, the target atom mass, and the threshold energy. An approximate exponential suppression of |alpha_VA| is observed with increasing vector meson mass or target atom mass, indicating that heavier vector mesons or heavier target nuclei exhibit weaker couplings in vector meson-nucleus interactions.

Collider processes at the highest available partonic center-of-mass energies - 10 TeV and above - exhibit a new regime of electroweak interactions where electroweak gauge bosons mostly act as quasi-massless partons in vector boson fusion processes. We scrutinize these processes using the Equivalent Vector boson Approximation (EVA) based on its implementation in the Monte Carlo generator framework Whizard. Using a variety of important physics processes, including top pairs, Higgs pairs, neutrino pairs, and vector boson pairs, we study the behavior of processes initiated by transverse and longitudinal vector bosons, both W and Z induced. By considering several distributions for each process, we conclude that: there is no universal, process-independent prescription which minimizes the discrepancies between EVA- and matrix-element-based predictions; even by resorting to process-by-process prescriptions, we typically observe significant observable-dependent effects; the uncertainties associated with parameter dependencies in the EVA can be as large as mathcal{O}(100%), and can only possibly be reduced by careful process-dependent kinematical selections.

In this article, we summarise the recent experimental measurements and theoretical work on Higgs boson production via vector-boson fusion at the LHC. Along with this, we provide state-of-the-art predictions at fixed order as well as with parton-shower corrections within the Standard Model at 13.6 TeV. The results are presented in the form of multi-differential distributions as well as in the Simplified Template Cross Section bins. All materials and outputs of this study are available on public repositories. Finally, following findings in the literature, recommendations are made to estimate theoretical uncertainties related to parton-shower corrections.

We consider the thermodynamics of a color-confined phase of quantum chromodynamics (QCD) and pure gauge theory within a string-inspired model, corresponding to a physical spatial dimension, d = 3. We show that the physical mass spectrum of massive mesons--in both the strange and non-strange sectors separately--is reasonably well described and extended by the exponential mass spectrum of open strings, rho(m), characterized by a unique Hagedorn temperature, T_H = sqrt{3sigma/2pi}, expressed by the string tension, sigma. This T_H is the value appropriate for d = 3 spatial dimensions, and is of order T_H sim 300~rm MeV for typical values of the string tension. It is much larger than the values of T_H, which have been phenomenologically extracted so far to describe the meson spectrum. Glueball states in pure gauge theory, modeled by closed strings, exhibit a similarly large Hagedorn temperature, highlighting a universal feature of the exponential spectrum. We further analyze the thermodynamic properties of the equation of state at finite temperature and demonstrate that, in the confined phase, the string models agree with lattice QCD results. This lends further support to the recent interpretation of the QCD phase diagram that incorporates strings as relevant degrees of freedom.

We present a comparative study of Higgs event classification at the Large Hadron Collider that bypasses the traditional reconstruction chain. As a benchmark, we focus on distinguishing tbar{t}H from tbar{t} events with H to bbar{b}, a particularly challenging task due to their similar final-state topologies. Our pipeline begins with event generation in Pythia8, fast simulation with ACTS/Fatras, and classification directly from raw detector hits.We show for the first time that a transformer model originally developed for inner tracker hit-to-track assignment can be retrained to classify Higgs events directly from raw hits. For comparison, we reconstruct the same events with texttt{Delphes} and train object-based classifiers, including multilayer perceptrons and the Particle Transformer. We evaluate both approaches under varying dataset sizes and pileup levels. Although Higgsformer works exclusively with inner tracker hits (i.e., without calorimeter or muon information), it achieves strong performance with an AUC value of 0.792.

We study axion-like particles (ALPs) in beam dump experiments, focusing on the Search for Hidden Particles (SHiP, at CERN) experiment and the Beam Dump eXperiment (BDX, at JLab). Many existing projections for sensitivity to ALPs in beam dump experiments have focused on production from either the primary proton/electron beam, or - in the case of SHiP - the secondary (high-energy) photons produced by neutral meson decays (e.g., pi^0rightarrowgamma gamma). In this work, we study the subsequent production of axions from the full electromagnetic shower in the target, finding order-of-magnitude enhancements in the visible decay yields across a wide range of axion masses. We update SHiP's sensitivity curve and provide new projections for BDX. Both experiments will be able to reach currently unexplored regions of ALP parameter space.

Unfolding, for example of distortions imparted by detectors, provides suitable and publishable representations of LHC data. Many methods for unbinned and high-dimensional unfolding using machine learning have been proposed, but no generative method scales to the several hundred dimensions necessary to fully characterize LHC collisions. This paper proposes a 3-stage generative unfolding framework that is capable of unfolding several hundred dimensions. It is effective to unfold the jet-level kinematics as well as the full substructure of light-flavor jets and of top jets, and is the first generative unfolding study to achieve high precision on high-dimensional jet substructure.

Cosmological phase transitions are a frequent phenomenon in particle physics models beyond the Standard Model, and the corresponding gravitational wave signal offers a key probe of new physics in the early Universe. Depending on the underlying microphysics, the transition can exhibit either direct or inverse hydrodynamics, leading to a different phenomenology. Most studies to date have focused on direct transitions, where the cosmic fluid is pushed or dragged by the expanding vacuum bubbles. In contrast, inverse phase transitions are characterized by fluid profiles where the plasma is sucked in by the expanding bubbles. Using the sound shell model, we derive and compare the gravitational wave spectra from sound waves for direct and inverse phase transitions, providing new insights into the potential observable features and the possibility of discriminating among the various fluid solutions in gravitational wave experiments.

Heavy neutral leptons (HNLs) and axion-like particles (ALPs) are both considered well-motivated candidates for beyond the standard model (BSM) physics. ALPs with couplings to gluons will be abundantly produced at the LHC. Therefore, HNLs produced via the ALP portal may provide unprecedented sensitivities to HNL parameters. Here, we study the prospects for the high-luminosity LHC to search for long-lived HNLs. We consider future far detectors as well as ATLAS in our simulations. In the limit where the ALP mass is large, HNLs are effectively produced by a dimension-8 operator connecting HNL pairs to gluons. For completeness, we therefore also calculate future LHC sensitivities for HNLs produced via N_RSMEFT operators with gluons.

We investigate the trilinear Higgs boson coupling derived from the functional forms of various extended Higgs potentials. In light of experimental constraints on Higgs boson couplings, we focus on extended Higgs models in which the trilinear Higgs boson coupling is predominantly determined by the Standard Model (SM) Higgs field. Such models include the nearly aligned Higgs effective field theory, classically scale-invariant models, pseudo-Nambu-Goldstone boson scenarios, tadpole-induced models, and others. We also consider higher-order corrections, including top quark and new particle contributions that are often neglected, and discuss their impact on the trilinear Higgs boson coupling. Finally, we show to what extent the functional forms of the Higgs potentials can be probed at future colliders.

The discovery of the Higgs boson at the LHC completed the Standard Model (SM), yet the possibility of additional scalars remains open, provided their contributions to electroweak symmetry breaking are sufficiently small. Recent analyses of LHC data have revealed statistically significant anomalies in multi-lepton final states - events characterized by multiple leptons, missing transverse energy, and (b-)jets. These anomalies provide intriguing hints of physics beyond the SM. In this work, we present the signature of growing excesses for a new scalar resonance with a mass of 152 pm 1 GeV, observed in the gammagamma, Zgamma, and WW channels. The combined global significance reaches a level that points toward the growing signature of this resonance. The findings align with a simplified model in which a heavy scalar boson decays into two lighter scalars, thus providing a consistent framework explaining the observed multi-lepton anomalies.These results significantly advance the search for new scalar bosons at the electroweak scale. Future investigations, including precision studies with upcoming HL-LHC data, will be crucial for confirming the nature of this resonance and exploring its implications for extending the SM.

There are at least three physical arguments for some form of supersymmetry, based on experiment and observation, but conventional supersymmetry (SUSY) has not been observed up to surprisingly high experimental limits. Here we consider a radically different version, with initial bosonic fields in 32=16+overline{16} (primitive sfermion) and 10=5+overline{5} (primitive Higgs-related) representations of Spin(10) which do not satisfy Lorentz invariance. In the extremely early universe there is a reformation of these fields to achieve a stable Lorentz-invariant vacuum with two varieties of physical scalar-boson fields -- standard fields phi and fields varphi of a new kind. There are then two possible scenarios: If sfermion fields are in the phi sector, the present description leads back to standard physics, including the standard model, SO(10) grand unification, and conventional SUSY. But if sfermion fields belong to the varphi sector, the predictions for production and decays of sparticles are dramatically different, potentially explaining their previous nonobservation. The masses of scalar bosons are still protected from enormous radiative corrections, gauge unification can be achieved, and there is a lowest-mass superpartner as a dark matter candidate -- although it is presumed to be less abundant than the approx 70 GeV candidate we introduced earlier in this same general context. Calculations by Shankar, Tallman, and Martinez in separate papers explore the possibilities for detection in future colliders, beginning with the high-luminosity LHC.

String geometry theory is one of the candidates of the non-perturbative formulation of string theory. In this paper, in the bosonic closed sector of string geometry theory, we completely identify the perturbative vacua, which include general string backgrounds in bosonic closed string theory. From fluctuations around these configurations, we derive the path-integrals of perturbative strings on the string backgrounds up to any order.

The spontaneous breaking of a discrete symmetry can lead to the formation of domain walls in the early Universe. In this work, we explore the impact of bias directions on the dynamics of Z_N domain walls, mainly focusing on the N = 3 model with a biased potential. Utilizing the Press-Ryden-Spergel method, we numerically investigate the dynamics of domain walls with lattice simulations. We find notable differences in the dynamics of domain walls due to bias directions. Our results indicate that the annihilation time depends not only on the vacuum energy difference delta V but also on bias directions described by the relative potential difference zeta .

Quasi-periodic eruptions (QPEs), the repeated outbursts observed in soft X-ray bands, have attracted broad interest, but their physical origin is under debate. One of the popular models, the star-disk collision model, suggests that QPEs can be produced through periodic collisions of an orbiting star with the accretion disk of a central black hole (BH). However, previous tests of the star-disk collision model mainly focus on the timing analysis. Other observed properties, such as peak luminosities L_{rm{p}}, durations t_{rm{e}}, and radiation temperatures T_{rm{p}} of the eruptions, are not systematically investigated. For a sample of six QPE sources and two QPE-like sources, we test textbf{the shock-cooling emission model from star-disk collisions} by using these observables to derive the constraints on the stellar radius R_star. We find that, except for two sources (eRo-QPE3 and eRo-QPE4), the rest of the sample either has no allowed R_star to simultaneously reproduce the observed L_{rm{p}} and t_{rm{e}}, or the required R_star is too large to avoid being disrupted by the central BH. For the two exceptions, a stellar radius of the order of 1 R_{rm{odot}} is necessary to satisfy all the constraints. Another issue with the simplest version of this model is that it predicts k T_{rm{p}} sim 10 rm{eV}, one order of magnitude lower than the observed value.

The dynamics of quantum fields become nonperturbative when their interactions are probed by a large number of particles. To explore this regime we study correlation functions which involve a large number of fields, focussing on massive scalar theories that feature arbitrary self-interactions, phi^{2p}. Treating quantum fields as operator-valued distributions, we investigate n-point correlation functions at ultra-short distances and compute moments and cumulants of fields, using a semiclassical saddle point approximation in the double scaling limit of weak coupling, lambda to 0, large quantum number, n to infty, while keeping lambda n constant. Addressing the nonperturbative regime, where lambda n gtrsim 1, requires a resummation of the effective saddle point to all orders in lambda n. We perform this resummation in zero and one dimensions, and show that the moments, corresponding to correlation functions including disconnected contributions, grow exponentially with n. This growth is significantly reduced for higher-order self-interactions, i.e. for larger p. On the other hand, we argue that the cumulants, which represent connected correlation functions, grow even more rapidly and are mostly independent of p.

In bouncing cosmological models, either classical or quantum, the big bang singularity is replaced by a regular bounce. A challenging question in such models is how to keep the shear under control in the contracting phase, as it is well-known that the shear grows as fast as 1/a^{6} toward the bounce, where a is the average expansion factor of the universe. A common approach is to introduce a scalar field with an ekpyrotic-like potential which becomes negative near the bounce, so the effective equation of state of the scalar field will be greater than one, whereby it dominates the shear in the bounce region. As a result, a homogeneous and isotropic universe can be produced after the bounce. In this paper, we study how the ekpyrotic mechanism affects the inflationary phase in both loop quantum cosmology (LQC) and a modified loop quantum cosmological model (mLQC-I), because in these frameworks inflation is generic without such a mechanism. After numerically studying various cases in which the potential of the inflaton consists of two parts, an inflationary potential and an ekpyrotic-like one, we find that, despite the fact that the influence is significant, by properly choosing the free parameters involved in the models, the ekpyrotic-like potential dominates in the bounce region, during which the effective equation of state is larger than one, so the shear problem is resolved. As the time continuously increases after the bounce, the inflationary potential grows and ultimately becomes dominant, resulting in an inflationary phase. This phase can last long enough to solve the cosmological problems existing in the big bang model.

In curved space-time, a scalar field phi is generically expected to couple to curvature, via a coupling of the form xiphi^2R. Yet in the study of Hawking emission from regular black holes (RBHs), where scalar fields are often introduced as simple probes of the geometry, and the Ricci scalar is generically non-zero, this non-minimal coupling is almost always ignored. We revisit this assumption by studying scalar Hawking emission from four representative RBHs (the Bardeen, Hayward, Simpson-Visser, and D'Ambrosio-Rovelli space-times), within two benchmark cases: the conformal case xi=1/6, and a large negative value xi=-10^4 motivated by Higgs inflation. We compute the graybody factors and emission spectra, showing that the latter can be either enhanced or suppressed, even by several orders of magnitude. A crucial role is played by the sign of the term xi fR, with f(r)=-g_{tt} in Schwarzschild-like coordinates, as it determines whether the non-minimal coupling suppresses or enhances the geometric potential barrier. For the D'Ambrosio-Rovelli case with large negative xi, the low-energy emission spectrum is enhanced by up to five orders of magnitude, since xi fR<0 throughout the space-time, leading to a deep potential well which broadens the transmissive window. The deviations we find can be particularly relevant in the case where primordial RBHs are dark matter candidates, given the impact of the non-minimal coupling on their evaporation history.

We present a systematic investigation of particle number fluctuations in the crossover region near the critical endpoint of a first-order phase transition using molecular dynamics simulations of the classical Lennard-Jones fluid. We extend our prior studies to third- and fourth-order cumulants in both coordinate- and momentum-space acceptances and integrated correlation functions (factorial cumulants). We find that, even near the critical point, non-Gaussian cumulants equilibrate on time scales comparable to those of the second-order cumulants, but show stronger finite-size effects. The presence of interactions and of the critical point leads to strong deviations of the cumulants from the ideal-gas baseline in coordinate space; these deviations are expected to persist in momentum space in the presence of collective expansion. In particular, the kurtosis becomes strongly negative, kappa sigma^2 ll -1, on the crossover side of the critical point. However, this signal is significantly diluted once an efficiency cut used to distinguish protons from baryons is applied, leading to |kappa sigma^2| lesssim 1 even in the presence of the critical point. We discuss our results in the context of ongoing measurements of proton number cumulants in heavy-ion collisions in RHIC-BES-II.