Thu·Jan 25, 2024Thursday·January 25, 2024

1. 01*

   Jovian Signal at BOREXINO

   Saeed Ansarifard🇮🇷 · Yasaman Farzan🇮🇷

   The BOREXINO experiment has been collecting solar neutrino data since 2007, providing the opportunity to study the variation of the event rate over a decade. We find that at 96 \% C.L., the rate of low energy events shows a time modulation favoring a correlation with a flux from Jupiter. We present a new physics model, the Jovian Whisper Model, based on dark matter of mass $\sim 0.1-4$ GeV captured by Jupiter that can account for such modulation. We discuss how the Jovian Whisper Model (JWM) can be tested.

   hep-phastro-ph.EPastro-ph.SRPRD(2024)·6 citations
2. 02*

   Using Machine Learning to Improve PDF Uncertainties

   Jason P. Gombas🇺🇸 · Reinhard Schwienhorst🇺🇸 · Binbin Dong🇺🇸 · Jarrett Fein🇺🇸

   Parton Distribution Functions (PDFs) contribute significantly to the uncertainty on the determination of the top-quark pole mass and other precision measurements at the Large Hadron Collider (LHC). It is crucial to understand these uncertainties and reduce them to obtain the next generation of precision measurements at the LHC. The region of high momentum fraction offers an opportunity to make improvements to the PDFs. This study uses machine learning techniques in $t\bar{t}$ production to target this region of the PDF set and has potential to significantly reduce its uncertainty.

   hep-ph0 citations
3. 03*

   Singlet Dirac dark matter streamlined

   Carlos E. Yaguna🇨🇴 · Óscar Zapata🇨🇴

   We propose a new and compact realization of singlet Dirac dark matter within the WIMP framework. Our model replaces the standard $Z_2$ stabilizing symmetry with a $Z_6$, and uses spontaneous symmetry breaking to generate the dark matter mass, resulting in a much simplified scenario for Dirac dark matter. Concretely, we extend the Standard Model (SM) with just two new particles, a Dirac fermion (the dark matter) and a real scalar, both charged under the $Z_6$ symmetry. After acquiring a vacuum expectation value, the scalar gives mass to the dark matter and mixes with the Higgs boson, providing the link between the dark sector and the SM particles. With only four free parameters, this new model is extremely simple and predictive. We study the dark matter density as a function of the model's free parameters and use a likelihood approach to determine its viable parameter space. Our results demonstrate that the dark matter mass can be as large as $6$ TeV while remaining consistent with all known theoretical and experimental bounds. In addition, a large fraction of viable models turns out to lie within the sensitivity of future direct detection experiments, furnishing a promising way to test this appealing scenario.

   hep-phJCAP(2024)·7 citations
4. 04*

   Collectivity inside high-multiplicity jets in high-energy proton-proton collisions

   Wenbin Zhao🇺🇸 · Zi-Wei Lin🇨🇳 · Xin-Nian Wang

   We present the first study of collectivity inside jets with high charged multiplicity $N_{\mathrm{ch}}^j$ in proton-proton collisions at the Large Hadron Collider. By incorporating final-state partonic and hadronic interactions through cascade models among jet shower partons and final hadrons, we investigate and compare to the CMS experimental data on multiplicity distribution, pseudorapidity distribution, and elliptic anisotropy coefficient $v_2^j$ of two-particle correlations within the jet. We show that final-state partonic interactions are essential for producing the flow-like long-range correlation, which leads to the enhanced tail in the $N_{\mathrm{ch}}^j$ dependence of $v_2^j$ above the non-flow correlation from jet parton showering at high multiplicities ($N_{\mathrm{ch}}^j\gtrsim 70$) as observed in the CMS experimental data. In addition, we provide predictions for the pseudorapidity-gap dependence of $v_2^j$ that can be tested in future experimental measurements.

   hep-phnucl-exnucl-th11 citations
5. 05*

   Extracting transition generalized parton distributions from hard exclusive pion-nucleon scattering

   Jian-Wei Qiu🇺🇸 · Zhite Yu🇺🇸

   We study the extraction of transition generalized parton distributions (GPDs) from production of two back-to-back high transverse momentum photons ($\gamma \gamma$) and a massive pair of leptons (${\ell }^{+}{\ell }^{-}$) in hard exclusive pion-nucleon scattering. We argue that the exclusive scattering amplitude of both processes could be factorized into nonperturbative pion distribution amplitude and nucleon transition GPDs that are convoluted with perturbatively calculable short-distance matching coefficients. We demonstrate that the exclusive diphoton production not only is complementary to the Drell-Yan-type dilepton production for extracting the GPDs, but also provides enhanced sensitivities for extracting the parton momentum fraction $x$ dependence of the GPDs. We show that both exclusive observables are physically measurable at the J-PARC and AMBER experiment energies. If the target nucleon can be polarized, corresponding spin asymmetries can offer additional sensitivities for extracting transition GPDs.

   hep-phhep-exhep-latnucl-ex+1PRD(2024)·22 citations
6. 06*

   Heavy photophobic ALP at the LHC

   Masashi Aiko🇯🇵 · Motoi Endo🇯🇵 · Kåre Fridell🇯🇵

   We study the photophobic ALP model in high-mass regions under LHC Run-II. Since the ALP is predominantly coupled with electroweak gauge bosons such as $ZZ$, $WW$, and $Z\gamma$, and less with di-photon, the model may be probed via multi-boson final-state processes. We find that on-shell ALP productions with $Z\gamma$ final states currently provide the best sensitivities for $m_a>40\mathrm{GeV}$.

   hep-phJHEP(2024)·11 citations
7. 07*

   Metastable strings and grand unification

   Wilfried Buchmuller🇩🇪

   The structure of the Standard Model (SM) of particle physics points toward grand unified theories (GUTs) where strong and electroweak interactions are unified in a non-Abelian GUT group. The spontaneous breaking of the GUT symmetry to the SM symmetry, together with cosmic inflation, generically leads to metastable topological defects, the most prominent example being cosmic strings. The gravitational-wave background (GWB) produced by a cosmic string network is one of the candidates for an explanation of the GWB recently observed by pulsar timing array (PTA) experiments. We review some properties of the predicted GWB with emphasis on potential implications for GUT model building. The most striking prediction is a GWB in the LIGO-Virgo-KAGRA band that could be discovered in the near future.

   hep-phastro-ph.COhep-thPoS(2024)·3 citations
8. 08*

   Vector Dark Matter in the Fundamental Representation of $SU(2{)}_L$: Sommerfeld Enhancement and Indirect Detection

   Sebastián Acevedo-Espinoza🇨🇱 · Amanda Rodríguez🇨🇱 · Alfonso R. Zerwekh🇨🇱

   In this work, we study an extension of the Standard Model that includes a new massive vector field in the fundamental representation of $SU(2{)}_L$. The neutral component of this field provides a natural dark matter candidate. We compute the annihilation cross-section including Sommerfeld enhancement and the gamma-ray flux arising from dark matter annihilation. We derive constraints on the model parameter space using current gamma-ray observations and investigate the prospects for future searches. We find that the model exhibits resonances for dark matter masses in the range $2-10$ TeV, whose properties are influenced by the value of the Higgs portal coupling. We show that part of the remaining parameter space can be probed by CTA in the near future.

   hep-ph4 citations
9. 09*

   Effect of continuum states on the double-heavy hadron spectra

   Jaume Tarrús Castellà🇺🇸

   We present the leading order coupling of double-heavy hadrons to heavy hadron pairs in Born-Oppenheimer effective field theory. We obtain the expressions for the contribution of heavy hadron pairs to the masses and widths of double-heavy hadrons. We apply our result for the specific case of the coupling of the lowest lying heavy hybrids and $D_{(s)}^{(\ast )}{\bar{D}}_{(s)}^{(\ast )}(B_{(s)}^{(\ast )}{\bar{B}}_{(s)}^{(\ast )})$ obtaining a set of selection rules for the decays. We build a model for the coupling potential and compute the corresponding decay widths and the contributions to the mass of the heavy hybrids. We compare our results with the experimental exotic quarkonium spectrum and discuss the most likely experimental candidates for quarkonium hybrids.

   hep-phhep-exhep-latJHEP(2024)·11 citations
10. 10*

    One-loop electroweak radiative corrections to polarized $e^{+}{e}^{-}\to ZZ$ process

    S. Bondarenko (1,2)🇷🇺 · Ya. Dydyshka (3,4)🇷🇺 · L. Kalinovskaya (3)🇷🇺 · R. Sadykov (3)🇷🇺 · V. Yermolchyk (3,4) ((1) Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Dubna, 141980 Russia, (2) Dubna State University, Dubna 141980, Russia, (3) Dzhelepov Laboratory of Nuclear Problems, Joint Institute for Nuclear Research, Dubna, 141980 Russia, (4) Institute for Nuclear Problems, Belarusian State University, Minsk, 220006 Belarus)🇷🇺

    In the paper we recalculate and discuss high-precision theoretical predictions for cross sections of the process $e^{+}{e}^{-}\to ZZ$. We assume a complete one-loop implementation and a possibility of estimating the initial state polarizations, as well as the full-phase calculation. Numerical results are provided by our Monte-Carlo tools MCSANC integrator and ReneSANCe generator for typical energies and degrees of polarization of ILC and CLIC projects in two $\alpha (0)$ and G${}_{\mu }$ electroweak schemes.

    hep-phPRD(2024)·2 citations
11. 11*

    Theoretical aspects of relativistic spin hydrodynamics coupled with electromagnetic fields

    Rajeev Singh🇺🇸 · Masoud Shokri🇩🇪 · S. M. A. Tabatabaee🇮🇷

    We expand the classical phase-space distribution function to incorporate couplings between spin and electromagnetic fields. This extension has led to the derivation of modified constitutive relations for the charge current, energy-momentum tensor, and spin tensor. Due to these couplings, the new tensors are revised from their perfect fluid analogues, creating an interplay between the background and spin fluid equations of motion. The corrections introduced in our framework have the potential to shed light on the experimentally observed discrepancies in the spin polarization measurements of Lambda hyperons.

    hep-phnucl-thPoS(2024)·0 citations
12. 12*

    Visualisation of $CP$-violation effects in decay-time-dependent analyses of multibody $B$-meson decays

    Tim Gershon🇬🇧 · Thomas Latham🇬🇧 · Andy Morris🇫🇷 · Wenbin Qian🇨🇳 · Mark Whitehead🇬🇧 · Ao Xu🇮🇹

    Decay-time-dependent $CP$-violation effects in transitions of neutral $B$ mesons to $CP$-eigenstates can be visualised by oscillations in the asymmetry, as a function of decay time, between decay yields from mesons tagged as initially having $\overline{B}$ or $B$ flavour. Such images, for example for $B^0\to J/\psi K_{\mathrm{S}}^0$ decays where the magnitude of the oscillation is proportional to $\sin (2\beta )$ with $\beta$ being an angle of the Cabibbo--Kobayashi--Maskawa Unitarity Triangle, provide a straightforward illustration of the underlying physics. Until now there has been no comparable method to provide visualisation for the case of decays to multibody final states that are not $CP$-eigenstates, where interference between $CP$-even and -odd amplitudes provides additional physics sensitivity. A method is proposed to weight the data so that the terms of interest can be projected out and used to obtain asymmetries that visualise the relevant effects. Application of the weighting to $B_s^0$ decays, where effects due to non-zero width difference are not negligible, provides a novel method to observe $CP$ violation in interference between mixing and decay without tagging the production flavour.

    hep-phhep-exEPJC(2024)·1 citation
13. 13*

    $\rho$-meson spectroscopy and diffractive production using the holographic light-front Schrödinger equation and the 't Hooft equation

    Bheemsehan Gurjar🇮🇳 · Chandan Mondal🇨🇳 · Satvir Kaur🇨🇳

    We determine the mass spectroscopy and light-front wave functions (LFWFs) of the $\rho$-meson by solving the holographic Schrödinger equation of light-front chiral QCD along with the 't Hooft equation of (1+1)-dimensional QCD in the large $N_c$ limit. Subsequently, we utilize the obtained LFWFs in conjunction with the color glass condensate dipole cross-section to calculate the cross sections for the diffractive $\rho$-meson electroproduction. Our spectroscopic results align well with the experimental data. Predictions for the diffractive cross sections demonstrate good consistency with the available experimental data at different energies from H1 and ZEUS collaborations. Additionally, we show that the resulting LFWFs for the $\rho$-meson can effectively describe various properties, including its decay constant, distribution amplitudes, electromagnetic form factors, charge radius, magnetic and quadrupole moments. Comparative analyses are conducted with experimental measurements and the available theoretical predictions.

    hep-phPRD(2024)·15 citations
14. 14*

    Non-linearities in cosmological bubble wall dynamics

    Stefania De Curtis🇮🇹 · Luigi Delle Rose🇮🇹 · Andrea Guiggiani🇮🇹 · Ángel Gil Muyor🇪🇸 · Giuliano Panico🇮🇹

    A precise modelling of the dynamics of bubbles nucleated during first-order phase transitions in the early Universe is pivotal for a quantitative determination of various cosmic relics, including the stochastic background of gravitational waves. The equation of motion of the bubble front is affected by the out-of-equilibrium distributions of particle species in the plasma which, in turn, are described by the corresponding Boltzmann equations. In this work we provide a solution to these equations by thoroughly incorporating the non-linearities arising from the population factors. Moreover, our methodology relies on a spectral decomposition that leverages the rotational properties of the collision integral within the Boltzmann equations. This novel approach allows for an efficient and robust computation of both the bubble speed and profile. We also refine our analysis by including the contributions from the electroweak gauge bosons. We find that their impact is dominated by the infrared modes and proves to be non-negligible, contrary to the naive expectations.

    hep-phastro-ph.COhep-thJHEP(2024)·46 citations
15. 15*

    Masked Particle Modeling on Sets: Towards Self-Supervised High Energy Physics Foundation Models

    Tobias Golling🇨🇭 · Lukas Heinrich🇩🇪 · Michael Kagan🇺🇸 · Samuel Klein🇨🇭 · Matthew Leigh🇨🇭 · Margarita Osadchy🇮🇱 · John Andrew Raine🇨🇭

    We propose masked particle modeling (MPM) as a self-supervised method for learning generic, transferable, and reusable representations on unordered sets of inputs for use in high energy physics (HEP) scientific data. This work provides a novel scheme to perform masked modeling based pre-training to learn permutation invariant functions on sets. More generally, this work provides a step towards building large foundation models for HEP that can be generically pre-trained with self-supervised learning and later fine-tuned for a variety of down-stream tasks. In MPM, particles in a set are masked and the training objective is to recover their identity, as defined by a discretized token representation of a pre-trained vector quantized variational autoencoder. We study the efficacy of the method in samples of high energy jets at collider physics experiments, including studies on the impact of discretization, permutation invariance, and ordering. We also study the fine-tuning capability of the model, showing that it can be adapted to tasks such as supervised and weakly supervised jet classification, and that the model can transfer efficiently with small fine-tuning data sets to new classes and new data domains.

    hep-phcs.LGhep-exphysics.data-anMach.Learn.Sci.Tech.(2024)·82 citations
16. 16*

    System size dependence of thermodynamic variables at kinetic freeze-out in high-energy collisions using the Tsallis distribution

    Rishabh Sharma🇮🇳 · Krishan Gopal🇮🇳 · Sharang Rav Sharma🇮🇳 · Chitrasen Jena🇮🇳

    We use a thermodynamically consistent form of Tsallis distribution to study the dependence of various thermodynamic quantities on the system size in high-energy collisions. The charged hadron spectra obtained in $p$+$p$, $p$+Pb, Xe+Xe, and Pb+Pb collisions at LHC are used to determine the energy density, pressure, particle density, entropy density, mean free path, Knudsen number, heat capacity, isothermal compressibility, expansion coefficient, and speed of sound at the kinetic freeze-out surface. These quantities are studied as a function of the system size. Notably, the rate of increase (or decrease) in these thermodynamic variables is found to be more rapid in small systems such as $p$+$p$ and $p$+Pb collisions than in large systems such as Xe+Xe and Pb+Pb collisions. This may be due to the small volume of the hadronic system in small collision systems at kinetic freeze-out. It is observed that high-multiplicity $p$+$p$ collisions produce similar thermodynamic conditions as peripheral heavy-ion collisions at kinetic freeze-out.

    hep-phhep-ex3 citations
17. 17*

    Analytic Solutions of the DGLAP Evolution and Theoretical Uncertainties

    Andrea Simonelli🇺🇸

    The energy dependence for the singlet sector of Parton Distributions Functions (PDFs) is described by an entangled pair of ordinary linear differential equations. Although there are no exact analytic solutions, it is possible to provide approximated results depending on the assumptions and the methodology adopted. These results differ in their sub-leading, neglected terms and ultimately they are associated with different treatments of the theoretical uncertainties. In this work, a novel analytic approach in Mellin space is presented and a new methodology for obtaining closed and exponentiated analytic solutions is devised. Different results for the DGLAP evolution at Next-Lowest-Order are compared, discussing advantages and disadvantages for each solution. The generalizations to higher orders are addressed.

    hep-phEPJC(2024)·9 citations
18. 18*

    Superheavy SUSY-kind dark matter and high energy cosmic rays

    E.V. Arbuzova🇷🇺

    The search for supersymmetric partners at Large Hadron Collider revealed negative result. Though, strictly speaking, it does not exclude low energy supersymmetry, but still it leads to strong constraints of the parameter space. Therefore the search for supersymmetric particles at higher energies becomes of interest. It is shown that in $R^2$-modified cosmology heavy particles with the interaction strength typical for supersymmetry could be promising candidates for carriers of dark matter. We consider the heating of the Universe at the post-inflationary stage via particle production by oscillating curvature scalar (scalaron). The bounds on the masses of dark matter particles are obtained for different dominant decay modes of the scalaron. Possible impact of superheavy particle decays on the spectrum of ultra high energy cosmic rays is discussed.

    hep-phgr-qcPoS(2024)·1 citation
19. 19*

    Astrophysical Axion Bounds: The 2024 Edition

    Andrea Caputo🇨🇭 · Georg Raffelt🇩🇪

    We review the current status of astrophysical bounds on QCD axions, primarily based on the observational effects of nonstandard energy losses on stars, including black-hole superradiance. Over the past few years, many of the traditional arguments have been reexamined both theoretically and using modern data and new ideas have been put forth. This compact review updates similar Lecture Notes written by one of us in 2006 [Lect. Notes Phys. 741 (2008) 51-71].

    hep-phastro-ph.HEhep-exPoS(2024)·221 citations
20. 20*

    Dynamical Generation of the Baryon Asymmetry from a Scale Hierarchy

    Jae Hyeok Chang🇺🇸 · Kwang Sik Jeong🇰🇷 · Chang Hyeon Lee🇰🇷 · Chang Sub Shin🇰🇷

    We propose a novel baryogenesis scenario where the baryon asymmetry originates directly from a hierarchy between two fundamental mass scales: the electroweak scale $v$ and the Planck scale $M_P$, in the form of \begin{equation} Y_B \sim \sqrt{\frac{v}{M_P}} \, . \nonumber \end{equation} This relation straightforwardly gives the observed baryon yield today $Y_B$, which can be a hint for underlying fundamental physics. We provide an example of baryogenesis models that yield this relation. Our model is based on the neutrino-portal Affleck-Dine mechanism, which generates the asymmetry of the Affleck-Dine sector during the radiation-dominated era and subsequently transfers it to the baryon number before the electroweak phase transition. The observed baryon asymmetry is then a natural outcome of this scenario. The model is testable as it predicts the existence of a Majoron with a keV mass and an electroweak scale decay constant. The impact of the relic Majoron on the effective number of neutrinos ($\Delta N_{\mathrm{eff}}$) can be measured through near-future cosmic microwave background observations.

    hep-phPRD(2024)·3 citations
21. 21*

    Generalized Models for Inflationary Preheating: Oscillations and Symmetries

    Leia Barrowes · Fred C. Adams · Anthony M. Bloch · John T. Giblin · Jr. · Scott Watson

    The paradigm of the inflationary universe provides a possible explanation for several observed cosmological properties. In order for such solutions to be successful, the universe must convert the energy stored in the inflaton potential into standard model particles through a process known as reheating. In this paper, we reconsider the reheating process for the case where the inflaton potential respects an approximate (but spontaneously broken) conformal symmetry during the reheating epoch. After reviewing the Effective Field Theory of Reheating, we present solutions for the nonlinear oscillations of the inflaton field, derive the corresponding Hill's equation for the coupled reheating field, and determine the stability diagram for parametric resonance. For this class of models -- the simplest realization being a scalar field with a quartic term -- the expansion of the universe drives the coupled field toward a more unstable part of parameter space, in contrast to the standard case. We also generalize this class of models to include quadratic breaking terms in the potential during the reheating epoch and address the process of stability in that universality class of models.

    ↳ astro-ph.COhep-phmath-phmath.MPPRD(2024)·4 citations
22. 22*

    Choose Your Diffusion: Efficient and flexible ways to accelerate the diffusion model in fast high energy physics simulation

    Cheng Jiang🇬🇧 · Sitian Qian🇨🇳 · Huilin Qu🇨🇭

    The diffusion model has demonstrated promising results in image generation, recently becoming mainstream and representing a notable advancement for many generative modeling tasks. Prior applications of the diffusion model for both fast event and detector simulation in high energy physics have shown exceptional performance, providing a viable solution to generate sufficient statistics within a constrained computational budget in preparation for the High Luminosity LHC. However, many of these applications suffer from slow generation with large sampling steps and face challenges in finding the optimal balance between sample quality and speed. The study focuses on the latest benchmark developments in efficient ODE/SDE-based samplers, schedulers, and fast convergence training techniques. We test on the public CaloChallenge and JetNet datasets with the designs implemented on the existing architecture, the performance of the generated classes surpass previous models, achieving significant speedup via various evaluation metrics.

    ↳ physics.ins-dethep-exhep-phSciPost Phys.(2025)·14 citations
23. 23*

    Lattice QCD calculation of the $D_s^{\ast }$ radiative decay with (2+1)-flavor Wilson-clover ensembles

    Yu Meng🇨🇳 · Jin-Long Dang🇨🇳 · Chuan Liu🇨🇳 · Zhaofeng Liu🇨🇳 · Tinghong Shen🇨🇳 · Haobo Yan🇨🇳 · Ke-Long Zhang🇨🇳

    We perform a lattice calculation on the radiative decay of $D_s^{\ast }$ using the (2+1)-flavor Wilson-clover gauge ensembles generated by CLQCD collaboration. A method allowing us to calculate the form factor with zero transfer momentum is proposed and applied to the radiative transition $D_s^{\ast }\to D_s\gamma$ and the Dalitz decay $D_s^{\ast }\to D_s{e}^{+}{e}^{-}$. After a continuum extrapolation using three lattice spacings, we obtain $\Gamma (D_s^{\ast }\to D_s\gamma )=0.0549(54)$ keV, where the error is purely statistical. The result is consistent with previous lattice calculations but with a error reduced to only a fifth of the before. The Dalitz decay rate is also calculated for the first time and the ratio with the radiative transition is found to be $R_{ee}=0.624(3)\%$. A total decay width of $D_s^{\ast }$ can then be determined as 0.0587(54) keV taking into account the experimental branching fraction. Combining with the most recent experimental measurement on the branching fraction of the purely leptonic decay $D_s^{+,\ast }\to e^{+}{\nu }_e$, we obtain the quantity $f_{D_s^{\ast }}|V_{cs}|=(190.5_{-41.7_{\text{stat.}}}^{+55.1}\pm 12.6_{\text{syst.}})$ MeV, where the stat. is only the statistical error from the experiment, and syst. results from the experimental systematic uncertainty and the lattice statistical error. Our result leads to an improved systematic uncertainty compared to $42.7_{\text{syst.}}$ obtained using previous lattice prediction of total decay width $0.070(28)$ keV as the input.

    ↳ hep-lathep-exhep-phPRD(2024)·23 citations
24. 24*

    Finetuning Foundation Models for Joint Analysis Optimization

    Matthias Vigl🇩🇪 · Nicole Hartman🇩🇪 · Lukas Heinrich🇩🇪

    In this work we demonstrate that significant gains in performance and data efficiency can be achieved in High Energy Physics (HEP) by moving beyond the standard paradigm of sequential optimization or reconstruction and analysis components. We conceptually connect HEP reconstruction and analysis to modern machine learning workflows such as pretraining, finetuning, domain adaptation and high-dimensional embedding spaces and quantify the gains in the example usecase of searches of heavy resonances decaying via an intermediate di-Higgs system to four $b$-jets.

    ↳ hep-excs.LGhep-phphysics.data-anMach.Learn.Sci.Tech.(2024)·27 citations
25. 25*

    Relativistic meson-exchange currents in semi-inclusive lepton scattering

    Valerio Belocchi🇮🇹 · Maria Benedetta Barbaro🇮🇹 · Arturo De Pace🇮🇹 · Marco Martini🇫🇷

    We assess the impact of two-particle--two-hole excitations on the semi-inclusive electron scattering process (e,e'p) using a fully relativistic nuclear model calculation that precisely incorporates antisymmetrization. The calculation encompasses all contributions involving the exchange of a single pion and the excitation of a Delta resonance. Our results are compared with (e,e'p) data on carbon at kinematics where two-nucleon emission dominates. This work represents an essential step towards the microscopic computation of the two-particle--two-hole contribution to semi-inclusive neutrino reactions, crucial in the analysis of neutrino oscillation experiments.

    ↳ nucl-thhep-exhep-phPRC(2024)·9 citations
26. 26*

    Varying primordial state fractions in exo- and endothermic SIDM simulations of Milky Way-mass haloes

    Aidan Leonard (1) · Stephanie O'Neil (1)🇺🇸 · Xuejian Shen (1)🇺🇸 · Mark Vogelsberger (1,2)🇺🇸 · Olivia Rosenstein (1)🇺🇸 · Hoatian Shangguan (3) · Yuanhong Teng (4) · Jiayi Hu (5) ((1) MIT, (2) AIFAI MIT, (3) BU, (4) USTC, (5) Columbia)

    Self-interacting dark matter (SIDM) is increasingly studied as a potential solution to small-scale discrepancies between simulations of cold dark matter (CDM) and observations. We examine a physically motivated two-state SIDM model with both elastic and inelastic scatterings. In particular, endothermic, exothermic, and elastic scattering occur with equal probability at high relative velocities ($v_{\mathrm{rel}}\gtrsim 400km/s)$. In a suite of cosmological zoom-in simulation of Milky Way-size haloes, we vary the primordial state fractions to understand the impact of inelastic dark matter self-interactions on halo structure and evolution. In particular, we test how the initial conditions impact the present-day properties of dark matter haloes. Depending on the primordial state fraction, scattering reactions will be dominated by either exothermic or endothermic effects for high and low initial excited state fractions respectively. We find that increasing the initial excited fraction reduces the mass of the main halo, as well as the number of subhaloes on all mass scales. The main haloes are cored, with lower inner densities and higher outer densities compared with CDM. Additionally, we find that the shape of the main halo becomes more spherical the higher the initial excited state fraction is. Finally, we show that the number of satellites steadily decreases with initial excited state fraction across all satellite masses.

    ↳ astro-ph.COastro-ph.GAhep-phMNRAS(2024)·9 citations
27. 27*

    Origin of the Stochastic Gravitational Wave Background: First-Order Phase Transition vs. Black Hole Mergers

    Martin Wolfgang Winkler🇺🇸 · Katherine Freese🇸🇪

    The NANOGrav, Parkes and European Pulsar Timing Array (PTA) experiments have collected strong evidence for a stochastic gravitational wave background in the nHz-frequency band. In this work we perform a detailed statistical analysis of the signal in order to elucidate its physical origin. Specifically, we test the standard explanation in terms of supermassive black hole mergers against the prominent alternative explanation in terms of a first-order phase transition. By means of a frequentist hypothesis test we find that the observed gravitational wave spectrum prefers a first-order phase transition at $2-3\sigma$ significance compared to black hole mergers (depending on the underlying black hole model). This mild preference is linked to the relatively large amplitude of the observed gravitational wave signal (above the typical expectation of black hole models) and to its spectral shape (which slightly favors the phase-transition spectrum over the predominantly single power-law spectrum predicted in black hole models). The best fit to the combined PTA data set is obtained for a phase transition which dominantly produces the gravitational wave signal by bubble collisions (rather than by sound waves). The best-fit (energy-density) spectrum features, within the frequency band of the PTA experiments, a crossover from a steeply rising power law (causality tail) to a softly rising power law; the peak frequency then falls slightly above the PTA-measured range. Such a spectrum can be obtained for a strong first-order phase transition in the thick-wall regime of vacuum tunneling which reheats the Universe to a temperature of $T_{\ast }\sim \text{GeV}$. A dark sector phase transition at the GeV-scale provides a comparably good fit.

    ↳ astro-ph.COgr-qchep-phPRD(2025)·32 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.