HEP Phenomenology·hep-ph

Thu·Jul 11, 2024Thursday·July 11, 2024

29 papers—19 primary·10 cross-listed·reconstructed*

01*
Towards Beyond Standard Model Model-Building with Reinforcement Learning on Graphs
George N. Wojcik🇺🇸 · Shu Tian Eu🇺🇸 · Lisa L. Everett🇺🇸
We provide a framework for exploring physics beyond the Standard Model with reinforcement learning using graph representations of new physics theories. The graph structure allows for model-building without a priori specifying definite numbers of new particles. As a case study, we apply our method to a simple class of theories involving vectorlike leptons and a dark U(1) inspired by the portal matter paradigm. Using modern policy gradient methods, the agent successfully explores a model space consisting of both continuous and discrete parameters and identifies consistent theories. The minimal models found include both known and previously unstudied examples that can accommodate the muon anomalous magnetic moment and satisfy precision electroweak and flavor constraints. The method represents a step forward in enabling an automated model-building process for physics beyond the Standard Model.
hep-phhep-exhep-th6 citations
02*
Graph Reinforcement Learning for Exploring BSM Model Spaces
George N. Wojcik🇺🇸 · Shu Tian Eu🇺🇸 · Lisa L. Everett🇺🇸
We present a methodology for performing scans of BSM parameter spaces with reinforcement learning (RL). We identify a novel procedure using graph neural networks that is capable of exploring spaces of models without the user specifying a fixed particle content, allowing broad classes of BSM models to be explored. In theory, the technique is applicable to nearly any model space with a pre-specified gauge group. We provide a generic procedure by which a suitable graph grammar can be developed for any BSM model which features user-specified symmetry groups and a finite number of different possible particle species. As a proof of concept, we construct the graph grammar for theories with vector-like leptons that may or may not be charged under a dark U(1) group, inspired by portal matter extensions of the sub-GeV vector portal/kinetic mixing simplified dark matter models. We then use this graph grammar to create a RL environment tasked with creating models with these vector-like leptons that are consistent with a list of a variety of precision observables. The RL agent succeeds in developing models that can address the observed muon anomalous magnetic moment discrepancy while remaining consistent with flavor violation and electroweak precision observables, including both constructions that have previously been studied as well as new models which have not, to our knowledge, previously been identified. By inspecting the resulting ensembles of models that the agent produces and experimenting with different configurations for our RL environment and graph grammar, we also infer various lessons about the development of these environments that can be transferable to RL scans of more complicated model spaces, and comment on future directions for the development of this technique into a more mature tool.
hep-phhep-exhep-thPRD(2025)·9 citations
03*
Estimating centrality in heavy-ion collisions using Transfer Learning technique
Dipankar Basak🇮🇳 · Kalyan Dey🇮🇳
In this study, we explore the applicability of Transfer Learning techniques for estimating collision centrality in terms of the number of participants ( $N_{part}$ ) in high-energy heavy-ion collisions. In the present work, we leverage popular pre-trained CNN models such as VGG16, ResNet50, and DenseNet121 to determine $N_{part}$ in Au+Au collisions at $s = 200$ GeV on an event-by-event basis. Remarkably, all three models achieved good performance despite the pre-trained models being trained for databases of other domains. Particularly noteworthy is the superior performance of the VGG16 model, showcasing the potential of transfer learning techniques for extracting diverse observables from heavy-ion collision data.
hep-phnucl-thNPA(2025)·1 citation
04*
New constraints on CPT symmetry violation in charm mesons
Wojciech Krzemien🇵🇱 · Mateusz Kmiec🇵🇱 · Adam Szabelski🇵🇱 · Wojciech Wislicki🇵🇱
Small CPT-violating effects are admissible in several theories beyond the Standard Model of interactions. We analyse experimental data obtained with neutral flavoured meson mixing and place bounds on the scale of such phenomena. The constraints on the CPT-violating parameter $z$ are derived by reinterpreting the LHCb measurement of the time-dependent asymmetry in the Cabbibo-favoured $D^{0} \to K^{-} π^{+}$ and $D ˉ^{0} \to K^{+} π^{-}$ decay rates. The bounds provided in this paper are two orders of magnitude stricter compared to the results obtained by the FOCUS Collaboration. Among other constraints, we report bounds on the difference in the decay widths and masses of the neutral D meson flavour states at a 95 % confidence level. The decay width difference is bounded by $(- 4.7 < δ Γ_{D} < 2.1) \times 1 0^{- 16}$ GeV. The mass difference lies within~ $(- 2.0 < δ m_{D} < 2.0) \times 1 0^{- 15}$ GeV for 95% of $arg (z)$ values. The paper includes an assessment of the influence of CP violation on the results and a discussion of the future prospects.
hep-phPRD(2024)·3 citations
05*
Advances at the $γ_{5}$ -Frontier
Paul Kühler🇩🇪 · Dominik Stöckinger🇩🇪 · Matthias Weißwange🇩🇪
These proceedings discuss the current progress of the no-compromise approach to the dimensional renormalization of chiral gauge theories in the context of the BMHV scheme with non-anticommuting $γ_{5}$ . Despite spuriously breaking BRST-invariance in intermediate steps, it is the only scheme which handles the well-known $γ_{5}$ -problem mathematically consistently. We begin with a brief motivation, followed by an exposition of our methodology. Specifically, we illustrate the symmetry restoration procedure to obtain the required symmetry-restoring counterterms and provide insights into our computational setups, including recent developments. Building up on this, we present recent results and advances for the multi-loop renormalization of Abelian and non-Abelian chiral gauge theories, before concluding this article with a discussion on prospective implementations of the BMHV regularization in SM-like models.
hep-phPoS(2024)·7 citations
06*
Light-cone sum rules study on the purely non-factorizable $Λ_{c}^{+} \to Ξ^{0} K^{+}$ decay
Yu-Ji Shi🇨🇳 · Zhen-Xing Zhao🇨🇳
We investigate the purely non-factorizable $Λ_{c}^{+} \to Ξ^{0} K^{+}$ decay using light-cone sum rules. To extract the decay amplitudes, a three-point correlation function is defined and calculated at hadron and quark-gluon level, respectively. Both the W-exchange and the W-inward emission diagrams are considered in the quark-gluon level calculation, where the two-particle light-cone distribution amplitudes (LCDAs) of kaon are used as non-perturbative input. We obtain the decay amplitudes contributed from the twist-2 and twist-3 kaon LCDAs, respectively. The obtained P-wave amplitude is consistent with those predicted in the literature, while the S-wave one is much smaller. This significant difference between the S- and P- wave amplitudes leads to small up-down spin asymmetry, closing to the experimental measurement.
hep-phhep-exPRD(2024)·6 citations
07*
Radiative symmetry breaking from the on-shell perspective
Bartosz Sojka🇵🇱 · Bogumila Swiezewska🇵🇱
Models with classical scale symmetry, which feature radiative symmetry breaking, generically lead to a supercooled first-order phase transition in the early Universe resulting in a strong gravitational-wave signal, potentially observable by LISA. This is thanks to the absence of mass terms in the potential and the resulting logarithmic structure of the zero-temperature effective potential. It is known that imposing a symmetry at classical level does not prohibit breaking it by quantum corrections. In the case of scale symmetry, a mass term can in principle appear through renormalisation. This is not the case in the commonly used $MS$ or Coleman-Weinberg schemes. In this work, we renormalise a scale-invariant model in the on-shell scheme to check whether parameterising it with the physical masses will introduce mass terms to the potential. We find that indeed mass terms appear for an arbitrary choice of the physical masses. However, we formulate an on-shell condition for radiative symmetry breaking, sufficient and necessary for the cancellation of mass terms in the renormalised potential, yielding a logarithmic potential needed for supercooled phase transitions.
hep-phastro-ph.COhep-thPLB(2025)·4 citations
08*
Refactorisation and Subtraction
Lorenzo Magnea🇮🇹 · Calum Milloy🇮🇹 · Chiara Signorile-Signorile🇩🇪 · Paolo Torrielli🇮🇹
Infrared subtraction algorithms beyond next-to-leading order necessitate the analysis of multiple infrared limits of scattering amplitudes, where several particles sequentially become soft or collinear. In this contribution, we report on the study performed in arXiv:2403.11975, which investigates these limits from the perspective of infrared factorisation, offering general definitions for strongly-ordered soft and collinear kernels, expressed in terms of gauge-invariant operator matrix elements. These definitions facilitate the identification of local subtraction counterterms for strongly-ordered configurations, whose integrals are designed to cancel the IR poles of real-virtual counterterms. This framework is validated at tree level for multiple emissions, and at one loop for single and double emissions.
hep-phPoS(2024)·1 citation
09*
Kaluza-Klein Graviton Freeze-In and Big Bang Nucleosynthesis
Mathieu Gross🇫🇷 · Dan Hooper🇺🇸
In models featuring extra spatial dimensions, particle collisions in the early universe can produce Kaluza-Klein gravitons. Such particles will later decay, potentially impacting the process of Big Bang nucleosynthesis. In this paper, we consider scenarios in which gravity is free to propagate throughout $n$ flat, compactified extra dimensions, while the fields of the Standard Model are confined to a 3+1 dimensional brane. We calculate the production and decay rates of the states that make up the Kaluza-Klein graviton tower and determine the evolution of their abundances in the early universe. We then go on to evaluate the impact of these decays on the resulting light element abundances. We identify significant regions of previously unexplored parameter space that are inconsistent with measurements of the primordial helium and deuterium abundances. In particular, we find that for the case of one extra dimension (two extra dimensions), the fundamental scale of gravity must be $M_{⋆} > 2 \times 1 0^{13} GeV$ ( $M_{⋆} > 1 0^{10} GeV$ ) unless the temperature of the early universe was never greater than $T \sim 2 TeV$ ( $T \sim 1 GeV$ ). For larger values of $n$ , these constraints are less stringent. For the case of $n = 6$ , for example, our analysis excludes all values of $M_{⋆}$ less than $\sim 1 0^{6} GeV$ , unless the temperature of the universe was never greater than $T \sim 3 TeV$ . The results presented here severely limit the possibility that black holes were efficiently produced through particle collisions in the early universe's thermal bath.
hep-phastro-ph.COPRD(2024)·3 citations
10*
Time-Like Heavy-Flavour Thresholds for Fragmentation Functions: the Light-Quark Matching Condition at NNLO
Christian Biello🇩🇪 · Leonardo Bonino🇨🇭
Matching conditions are universal ingredients that describe how fragmentation functions change when heavy-flavour thresholds are crossed during the factorisation scale evolution. They are the last missing piece for a consistent description of observables with identified final-state hadrons at next-to-next-to leading order accuracy in quantum chromodynamics. We present an analytical form of the matching condition for light-flavour to hadron fragmentation function at next-to-next-to leading order. The derivation is performed by extending the formalism employed in the extraction of the next-to leading order matching conditions to the subsequent order, making use of $e^{+} e^{-}$ annihilation cross sections. We obtain the first non-trivial heavy-quark effect in the light-quark fragmentation functions and provide results in Mellin space.
hep-phEPJC(2024)·17 citations
11*
Confirming the glueball-like particle $X (2370)$ productions in $e^{+} e^{-}$ collisions at BESIII energy with PACIAE model
Zhi-Lei She🇨🇳 · An-Ke Lei🇨🇳 · Wen-Chao Zhang🇨🇳 · Yu-Liang Yan🇨🇳 · Dai-Mei Zhou🇨🇳 · Hua Zheng🇨🇳 · Ben-Hao Sa🇨🇳
The parton and hadron cascade model {\footnotesize PACIAE} is employed to confirm the BESIII newest observation of glueball-like particle $X (2370)$ production in $e^{+} e^{-}$ collisions at $s = 4.95 GeV$ . We coalesce the $X (2370)$ glueball state with two gluons in the simulated partonic final state by the Dynamically Constrained Phase-space Coalescence ({\footnotesize DCPC}) model. Alternative configuration of $X (2370)$ molecular state is recombined in the simulated hadronic final state with $π^{+}, π^{-}, K^{+}, K^{-}, K_{S}^{0}, K_{S}^{0}$ and $η^{'}$ by {\footnotesize DCPC} model. The resulted particle transverse momentum spectrum and rapidity distribution, etc. show a significant discrepancy between the two states. They are not only serving as criteria to distinguish the $X (2370)$ glueball state or molecular state, but also confirming the BESIII observation of glueball-like particle $X (2370)$ productions in $e^{+} e^{-}$ collisions.
hep-ph4 citations
12*
Quark spin effects in $e^{+} e^{-}$ annihilation: a Monte Carlo event generator study
A. Kerbizi🇮🇹 · L. Lönnblad🇸🇪 · A. Martin🇮🇹
Quark spin effects in $e^{+} e^{-}$ annihilation to pseudoscalar and vector mesons are implemented for the first time in the PYTHIA Monte Carlo event generator. The spin-dependent fragmentation of the string stretched between the produced quark-antiquark pair with correlated spin states is described by the string+ $^{3} P_{0}$ model implemented in the string fragmentation routine of PYTHIA by using the StringSpinner package. The simulated events are used to study the model predictions for the Collins asymmetries of mesons produced back-to-back in the $e^{+} e^{-}$ center of mass system by using both the thrust axis method and the hadronic plane method. The obtained asymmetries are compared to the available data from the BELLE and BABAR experiments and the underlying Collins analysing power from the string+ $^{3} P_{0}$ model is compared with phenomenological extractions.
hep-phPRD(2024)·4 citations
13*
Diphoton signals for the Georgi-Machacek scenario at the Large Hadron Collider
Satyaki Bhattacharya🇮🇳 · Rituparna Ghosh🇮🇳 · Biswarup Mukhopadhyaya🇮🇳
The diphoton channel for exploring the Georgi-Machacek (GM) scenario containing scalar triplets at the Large Hadron Collider (LHC) has been identified as germane, and subjected to a detailed study. The scalar spectrum of the model, which imposes a custodial SU(2) on the potential, gets classified into a 5-plet, a 3-plet and two singlets under the custodial symmetry. While most attempts to probe or constrain the scenario at the LHC depend largely on signals of charged scalars, we point out that the custodial SU(2) singlet state H can have a substantial branching ratio (amounting to a few percent) into two photons. We carry out a detailed simulation of the resulting signal and the standard model backgrounds, obtaining the signal significance in different regions of the parameter space using the profile likelihood ratio method. Substantial regions of the GM parameter space is thus shown to be accessible to LHC studies, both at the high-luminosity run with $\int L d t = 3000 f b^{- 1}$ , and also in Run-3 with $\int L d t = 300 f b^{- 1}$ , even after folding in systematic errors. We have also demonstrated that a rather subtantial improvement in the signal significance is achieved by switching over from a cut-based analysis to one based on neural network.
hep-phPRD(2025)·4 citations
14*
Dispersive determination of the fourth generation lepton masses
Hsiang-nan Li🇹🇼
We continue our previous determination of the masses of the sequential fourth generation quarks in an extension of the Standard Model, and predict the mass $m_{4}$ ( $m_{L}$ ) of the fourth generation neutrino $ν_{4}$ (charged lepton $L$ ) by solving the dispersion relation associated with heavy fermion decays. The results $m_{4} \approx 170$ GeV and $m_{L} \approx 270$ GeV are extracted from the dispersive analyses of the $t \to d e^{+} ν_{4}$ and $L^{-} \to ν_{1} t ˉ d$ decay widths, respectively, where $t$ ( $d$ , $e^{+}$ , $ν_{1}$ ) denotes a top quark (down quark, positron, light neutrino). The predictions are cross-checked by examining the $L^{-} \to ν_{4} u ˉ d$ decay, $u ˉ$ being an anti-up quark. It is shown that the fourth generation leptons with the above masses survive the current experimental bounds from Higgs boson decays into photon pairs and from the oblique parameters. We also revisit how the existence of the fourth generation leptons impacts the dispersive constraints on the neutrino masses and the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) matrix elements. It is found that the unitarity of the $3 \times 3$ PMNS matrix holds well up to corrections of $O (m_{ν}^{2} / m_{W}^{2})$ , $m_{ν}$ ( $m_{W}$ ) being a light neutrino (the $W$ boson) mass, whose mixing angles and $C P$ phase prefer the values $θ_{12} \approx 3 4^{\circ}$ , $θ_{23} \approx 4 7^{\circ}$ , $θ_{13} \approx 5^{\circ}$ and $δ \approx 20 0^{\circ}$ in the normal-ordering scenario for neutrino masses.
hep-phhep-exJ.Phys.G(2025)·8 citations
15*
Inhibition of splitting of the chiral and deconfinement transition due to rotation in QCD: the phase diagram of linear sigma model coupled to Polyakov loop
Pracheta Singha🇷🇴 · Victor E. Ambrus🇷🇴 · Maxim N. Chernodub🇫🇷
We discuss the effect of rigid rotation on the critical temperatures of deconfinement and chiral transitions in the linear sigma model coupled to quarks and the Polyakov loop. We point out the essential role of the causality condition, which requires that any point of the system should rotate slower than the velocity of light. We show that imposing this physical requirement leads to inhibition of the splitting between the chiral and confining transitions, which becomes negligibly small ({\Delta}T ~ 1 MeV or less) for experimentally relevant, slow angular velocities {\Omega} ~ 10 MeV of a 5-10 fm-sized systems. Moreover, the boundedness of the system has a much bigger effect on temperature splitting than the rotation itself: the splitting reaches 10 MeV in a small, one-fermi-sized non-rotating system. The temperature splitting may, however, become enhanced in an academic limit of ultra-relativistic regimes when the boundary of the system rotates at near-to-light velocities.
hep-phhep-lathep-thnucl-thPRD(2024)·21 citations
16*
Equivalence of two component spinor mechanism and four component spinor mechanism in top quark pair production
Malvika Deo🇮🇳 · Anuradha Misra🇮🇳 · Sharada Subramaniam🇮🇳 · Radhika Vinze🇮🇳
In this article, we calculate the $S$ -matrix elements for the process $e^{+} e^{-} \to t t ˉ$ mediated by SM photon, $Z$ boson and an additional $Z^{^{'}}$ boson indicating the contribution from new physics. We calculate the amplitude square using two component spinor formalism and four component spinor formalism and show the equivalence of the results using the two formalisms. We also establish the relations between the couplings of $Z^{^{'}}$ boson to fermions in the two component spinor formalism and four component spinor formalism.
hep-phhep-th0 citations
17*
Towards an Interpretation of the First Measurements of Energy Correlators in the Quark-Gluon Plasma
Carlota Andres🇫🇷 · Fabio Dominguez🇪🇸 · Jack Holguin🇬🇧 · Cyrille Marquet🇫🇷 · Ian Moult🇺🇸
Energy correlators have recently been proposed as a class of jet substructure observables that directly link experimental measurements of the asymptotic energy flux with the field theoretic description of the underlying microscopic dynamics. This link holds particular promise in heavy-ion physics, where both experimental measurements and theoretical interpretations are inherently complex. With recent measurements of energy correlators in proton-proton collisions, the first measurement of these observables on inclusive jets in heavy-ion collisions underscores the importance of a theoretical understanding of their behavior in this complex environment. In this manuscript, we extend our previous calculations to account for several effects necessary for a qualitative understanding of the behavior of energy correlators on inclusive jets in heavy-ion collisions. Through a semi-analytic approach implemented in a hydrodynamically expanding quark-gluon plasma (QGP), we account for medium-induced radiation with leading broadening effects, selection biases arising from energy loss, and a description of the confinement transition. Our results represent a crucial first step towards interpreting the measurements of energy correlators on inclusive jets in heavy-ion collisions, which marks a significant milestone in connecting heavy-ion experiment and fundamental quantum field theory, in the quest to disentangle the microscopic dynamics of the QGP.
hep-phhep-exhep-thnucl-ex+1JHEP(2025)·46 citations
18*
A Stress Test of Global PDF Fits: Closure Testing the MSHT PDFs and a First Direct Comparison to the Neural Net Approach
L. A. Harland-Lang🇬🇧 · T. Cridge🇩🇪 · R.S. Thorne🇬🇧
We present a first global closure test of the fixed parameterisation (MSHT) approach to PDF fitting. We find that the default MSHT20 parameterisation can reproduce the features of the input set in such a closure test to well within the textbook uncertainties. This provides strong evidence that parameterisation inflexibility in the MSHT20 fit is not a significant issue in the data region. We also present the first completely like--for--like comparison between two global PDF fits, namely MSHT and NNPDF, where the only difference is guaranteed to be due to the fitting methodology. To achieve this, we present a fit to the NNPDF4.0 data and theory inputs, but with the MSHT fixed parameterisation. We find that this gives a moderately, but noticeably, better fit quality than the central NNPDF4.0 fits, both with perturbative and fitted charm, and that this difference persists at the level of the PDFs and benchmark cross sections. The NNPDF4.0 uncertainties are found to be broadly in line with the MSHT results if a textbook $T^{2} = 1$ tolerance is applied, but to be significantly smaller if a tolerance typical of the MSHT20 fit is applied. This points to an inherent inconsistency between these approaches. We discuss the need for an enlarged tolerance criterion in global PDF fits in detail, and demonstrate the impact of data/theory inconsistencies in the closure test setting; namely, these do not lead to any increase in the $T^{2} = 1$ PDF uncertainty. We also investigate the impact of restricting the PDF parameterisation to have fewer free parameters than the default MSHT20 case, and find this can be significant at the level of both closure tests and the full fit.
hep-phhep-exEPJC(2025)·27 citations
19*
Dimension-8 SMEFT contact-terms for vector-pair production via on-shell Higgsing
Jared M Goldberg🇮🇱 · Hongkai Liu🇮🇱 · Yael Shadmi🇮🇱
We derive the dimension-8 standard-model effective theory (SMEFT) contact terms relevant for vector-pair production at the LHC and lepton colliders. We first list the relevant dimension-8 massless SMEFT amplitudes, and then obtain the low-energy amplitudes using on-shell Higgsing. In all cases, the contributions we calculate are the leading-order contributions to 4-point contact-terms; the dimension-6 SMEFT merely corrects the three-point couplings entering the amplitudes. Since they are given in terms of physical quantities, namely momenta and polarizations, the results allow for a direct mapping of EFT effects to low-energy observables. The vector amplitudes are sensitive to both anomalous vector couplings and Higgs self-couplings. The left-handed fermion amplitudes feature SU(2) violating effects first generated at dimension-8. We also compare our results to HEFT predictions. Interestingly, the dimension-8 SMEFT populates almost all the novel structures generated by the dimension-8 HEFT.
hep-phhep-thJHEP(2024)·15 citations
20*
Unravelling the role of merger histories in the population of In situ stars: linking IllustrisTNG cosmological simulation to H3 survey
Razieh Emami · Lars Hernquist🇺🇸 · Randall Smith · James F. Steiner · Grant Tremblay · Douglas Finkbeiner · Mark Vogelsberger🇺🇸 · Josh Grindlay · Federico Marinacci🇮🇹 · Kung-Yi Su · Cecilia Garraffo🇺🇸 · Yuan-Sen Ting and 7 other authors
We undertake a comprehensive investigation into the distribution of in~situ stars within Milky Way-like galaxies, leveraging TNG50 simulations and comparing their predictions with data from the H3 survey. Our analysis reveals that 28% of galaxies demonstrate reasonable agreement with H3, while only 12% exhibit excellent alignment in their profiles, regardless of the specific spatial cut employed to define in~situ stars. To uncover the underlying factors contributing to deviations between TNG50 and H3 distributions, we scrutinise correlation coefficients among internal drivers(e.g., virial radius, star formation rate [SFR]) and merger-related parameters (such as the effective mass-ratio, mean distance, average redshift, total number of mergers, average spin-ratio and maximum spin alignment between merging galaxies). Notably, we identify significant correlations between deviations from observational data and key parameters such as the median slope of virial radius, mean SFR values, and the rate of SFR change across different redshift scans. Furthermore, positive correlations emerge between deviations from observational data and parameters related to galaxy mergers. We validate these correlations using the Random Forest Regression method. Our findings underscore the invaluable insights provided by the H3 survey in unravelling the cosmic history of galaxies akin to the Milky Way, thereby advancing our understanding of galactic evolution and shedding light on the formation and evolution of Milky Way-like galaxies in cosmological simulations.
↳ astro-ph.GAastro-ph.COastro-ph.SRhep-phPubl.Astron.Soc.Austral.(2025)·0 citations
21*
Bootstrapping spinning two body problem in dynamical Chern-Simons gravity using worldline QFT
Arpan Bhattacharyya🇮🇳 · Debodirna Ghosh🇮🇳 · Saptaswa Ghosh🇮🇳 · Sounak Pal🇮🇳
In this paper, we compute the WQFT partition function, specifically the eikonal phase in a black hole scattering event in the dynamical Chern-Simons theory, using the techniques of spinning worldline quantum field theory. We consider the scattering of spinning black holes and highlight the necessary details for the calculation of the partition function. We present the $ϵ$ -expansion of the essential two-loop integrals using Integration-by-Parts (IBP) reduction and differential equation techniques, which we then utilize to compute the linear-in-order spin eikonal phase up to 3PM. Additionally, we discuss the dependence of the phase on the spin orientations of the black holes.
↳ hep-thgr-qchep-phJHEP(2025)·18 citations
22*
The spatial correlations between pulsars for interfering sources in Pulsar Timing Array and evidence for gravitational-wave background in NANOGrav 15-year data set
Yu-Mei Wu🇨🇳 · Yan-Chen Bi🇨🇳 · Qing-Guo Huang🇨🇳
Pulsar timing arrays (PTAs), aimed at detecting gravitational waves (GWs) in the $1 \sim 100$ nHz range, have recently made significant strides. Compelling evidence has emerged for a common spectrum signal spatially correlated among pulsars, following a Hellings-Downs (HD) pattern, which is crucial for detecting a gravitational-wave background (GWB). However, the HD curve is expected for discrete and non-interfering sources, which is unlikely to hold in realistic scenarios with potential interference among numerous GW sources, such as the supermassive black-hole binaries. Incorporating interference was previously expected to introduce an irreducible uncertainty (known as "cosmic variance") in discerning the HD correlation; however, our work reveals how this interference generates measurable frequency-dependent spatial correlations distinct from the HD curve. The spatial correlations for interfering sources (referred to as "ISC") still exhibit contributions in the quadrupole and higher orders, resembling the HD correlation and encoding the nature of GW radiations. We apply these novel correlations to search for a GWB in the NANOGrav 15-year data set. In an optimistic estimation, our findings show a Bayes factor of $33.7 \pm 3.2$ comparing ISC to the HD correlation, and an improvement in optimal statistic signal-to-noise ratio from $4.9 \pm 1.1$ for the HD correlation to $6.6 \pm 1.7$ for the ISC, highlighting the significant enhancement in evidence for detecting a GWB through incorporating interference.
↳ astro-ph.COastro-ph.HEgr-qchep-ph+1PRD(2025)·10 citations
23*
Testing the Cosmic Distance Duality Relation Using Strong Gravitational Lensing Time Delays and Type Ia Supernovae
Jing-Zhao Qi🇺🇸 · Yi-Fan Jiang🇨🇳 · Wan-Ting Hou🇨🇳 · Xin Zhang🇺🇸
We present a comprehensive test of the cosmic distance duality relation (DDR) using a combination of strong gravitational lensing (SGL) time delay measurements and Type Ia supernovae (SNe Ia) data. We investigate three different parameterizations of potential DDR violations. To bridge the gap between SGL and SNe Ia datasets, we implement an artificial neural network (ANN) approach to reconstruct the distance modulus of SNe Ia. Our analysis uniquely considers both scenarios where the absolute magnitude of SNe Ia ( $M_{B}$ ) is treated as a free parameter and where it is fixed to a Cepheid-calibrated value. Using a sample of six SGL systems and the Pantheon+ SNe Ia dataset, we find no statistically significant evidence for DDR violations across all parameterizations. The consistency of our findings across different parameterizations not only reinforces confidence in the standard DDR but also demonstrates the robustness of our analytical approach.
↳ astro-ph.COgr-qchep-phApJ(2025)·25 citations
24*
A Decade of Collectivity in Small Systems
Jan Fiete Grosse-Oetringhaus🇨🇭 · Urs Achim Wiedemann🇨🇭
Signatures of collectivity, including azimuthally anisotropic and radial flow as well as characteristic hadrochemical dependencies, have been observed since long in (ultra)relativistic nucleus-nucleus collisions. They underpin the interpretation of these collision systems in terms of QGP formation and close-to-perfect fluidity. Remarkably, however, essentially all these signatures of collectivity have been identified within the last decade in collision systems as small as pp and p-Pb, where collective phenomena had been assumed to be absent traditionally. Precursor phenomena may have been found even in ep and $e^{+} e^{-}$ collisions. This article provides a complete review of all data on small system collectivity. It reviews model simulations of these data where available. However, in the absence of a phenomenologically fully satisfactory description of collectivity across all system sizes, we focus in particular on the theoretical basis of all dynamical frameworks of collectivity invoked in heavy ion collisions, and their expected scaling with system size. Our discussion clarifies to what extent all dynamical explanations are challenged by the available data.
↳ hep-exhep-phnucl-ex85 citations
25*
Flattenicity as "centrality" estimator in p-Pb collisions simulated with PYTHIA 8.312 Angantyr
Antonio Ortiz🇲🇽 · Gyula Bencedi🇭🇺 · Feng Fan🇨🇳
In this paper, a "centrality" estimator based on flattenicity ( $ρ$ ) is studied in proton-led (p-Pb) collisions at $s_{NN} = 5.02$ TeV using PYTHIA 8 Angantyr. Although Angantyr is still under development, the existing implementation is enough to study the particle production in systems where medium effects are absent. Firstly, ALICE data on pseudorapidity distributions as a function of the forward multiplicity (V0M), as well as transverse momentum distributions of identified particles in non-single diffractive p-Pb collisions, are compared with Angantyr. Secondly, the average number of binary nucleon-nucleon ( $N_{coll}$ ) collisions for different "centrality" estimators are compared. The studies include the following "centrality" estimators: V0M, $ρ$ and midrapidity multiplicity (CL1). On one hand, the "centrality" dependence of $⟨ N_{coll} ⟩$ for the $ρ$ selection shows the smallest deviations ( $< 8$ %) with respect to that obtained using impact parameter $b$ ; on the other hand, the V0M and CL1 yield huge deviations (up to a factor 2) with respect to the results using $b$ . The particle ratios and nuclear modification factors ( $Q_{pPb}$ ) as a function of $p_{T}$ are also studied. The proton-to-pion ratio exhibits a flow-like peak at intermediate $p_{T}$ (2-8 GeV/ $c$ ) with little or no "centrality" dependence for V0M, $ρ$ and $b$ selections. The kaon-to-pion ratio as a function of $p_{T}$ is "centrality" independent for the same selections. On the contrary, for the CL1 class the ratios exhibit the typical behaviour associated with hard physics. Regarding $Q_{pPb}$ , a peak at intermediate $p_{T}$ ( $2 - 8$ GeV/ $c$ ) for different particle species is observed when the "centrality" is obtained with $b$ or $ρ$ . The observed features diminish for the selections based on V0M and CL1.
↳ nucl-exhep-phJ.Phys.G(2024)·5 citations
26*
The Cosmological Preference for Negative Neutrino Mass
Daniel Green🇺🇸 · Joel Meyers🇺🇸
The most precise determination of the sum of neutrino masses from cosmological data, derived from analysis of the cosmic microwave background (CMB) and baryon acoustic acoustic oscillations (BAO) from the Dark Energy Spectroscopic Instrument (DESI), favors a value below the minimum inferred from neutrino flavor oscillation experiments. We explore which data is most responsible of this puzzling aspect of the current constraints on neutrino mass and whether it is related to other anomalies in cosmology. We demonstrate conclusively that the preference for negative neutrino masses is a consequence of larger than expected lensing of the CMB in both the two- and four-point lensing statistics. Furthermore, we show that this preference is robust to changes in likelihoods of the BAO and CMB optical depth analyses given the available data. We then show that this excess clustering is not easily explained by changes to the expansion history and is likely distinct from the preference for for dynamical dark energy in DESI BAO data. Finally, we discuss how future data may impact these results, including an analysis of Planck CMB with mock DESI 5-year data. We conclude that the negative neutrino mass preference is likely to persist even as more cosmological data is collected in the near future.
↳ astro-ph.COhep-phhep-thPRD(2025)·130 citations
27*
Linear dynamical stability and the laws of thermodynamics
Blaise Goutéraux🇫🇷 · Eric Mefford🇨🇦
We show that the dynamical stability under linear perturbations of interacting systems in the hydrodynamic regime follows from the first and the second laws of thermodynamics. Our argument extends to systems with spontaneously or softly broken symmetries and in the presence of magnetic fields.
↳ hep-thcond-mat.quant-gascond-mat.stat-mechcond-mat.str-el+16 citations
28*
Reviving QFT in $2 + 1$ de Sitter Spacetime
Guido D'Amico🇮🇹 · Nemanja Kaloper🇺🇸
We consider a conformally coupled scalar QFT on $2 + 1$ dimensional static Einstein universe $R \times S^{2}$ , and write down the free theory Hilbert space. We explain that this theory is secretly a QFT in $2 + 1$ de Sitter space because all the quantum observables experience {\it quantum revivals}, which naturally restricts the timelike $R$ to the appropriate de Sitter time range. Our construction circumvents the causal obstruction to formulating QFT in de Sitter due to event horizons. There aren't any in static Einstein. The `unitary gauge' description of the theory is realized by the zonal harmonics $P_{ℓ} (n^\cdot n^^{'})$ . We verify that interactions with conformally invariant external sources are mediated only by these modes. Hence these modes comprise the complete basis of the "bulk" theory. When the theory is cut off in the UV the basis dimension scales as the Bekenstein-Hawking formula.
↳ hep-thastro-ph.COgr-qchep-ph+1PRD(2024)·2 citations
29*
Inflationary Gravitational Waves as a probe of the unknown post-inflationary primordial Universe
Athul K. Soman🇮🇳 · Swagat S. Mishra🇬🇧 · Mohammed Shafi🇮🇳 · Soumen Basak🇮🇳
One of the key predictions of the standard inflationary paradigm is the quantum mechanical generation of the transverse and traceless tensor fluctuations due to the rapid accelerated expansion of space, which later constitute a stochastic background of primordial gravitational waves (GWs). The amplitude of the (nearly) scale-invariant inflationary tensor power spectrum at large scales provides us with crucial information about the energy scale of inflation in the case of the minimal inflaton coupling to gravity. Furthermore, the spectral energy density, $Ω_{_{GW}} (f)$ , of the GWs at sufficiently small scales (or, large frequencies $f$ ) serves as an important observational probe of post-inflationary primordial dynamics. In fact, the small-scale spectral tilt, $n_{_{GW}} = \frac{d l o g Ω _{_{GW}}}{d l o g f}$ , of the spectral energy density of GWs is sensitive to the (unknown) post-inflationary equation of state (EoS), $w$ , of the universe; with a softer EoS ( $w < 1/3$ ) leading to a red tilt: $n_{_{GW}} < 0$ , while a stiffer EoS ( $w > 1/3$ ) resulting in a blue tilt: $n_{_{GW}} > 0$ . The post-inflationary dynamics, however, is generically expected to be quite complex, potentially involving a number of distinct phases. Hence, in this work, we discuss the possibility of multiple sharp transitions, namely $w_{1} \to w_{2} \to w_{3} \to ... \to w_{n}$ , in the EoS of the post-inflationary universe and compute the corresponding spectral energy density of the inflationary GWs. We explicitly determine the region of the parameter space ${w_{1}, w_{2}, w_{3}, ..., w_{n}}$ which leads to a potentially detectable signal in the upcoming GW detectors, without violating the current constraints.
↳ gr-qcastro-ph.COhep-phhep-thPRD(2025)·13 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.