Wed·Apr 26, 2023Wednesday·April 26, 2023

1. 01*

   Charged resonances and Minimal Dark Matter bound states at a multi-TeV muon collider

   Natascia Vignaroli🇮🇹

   A multi-TeV muon collider proves to be very efficient not only for the search for new heavy neutral particles, but also for the discovery of charged bosons of the $W^{\prime }$ type. We find that, by analyzing the associated production with a Standard Model W, charged resonances can be probed directly up to multi-TeV mass values close to the collision energy, and for very small couplings with the SM fermions, of the order of $10^{-3}-10^{-4}$ times the SM weak coupling. Additionally, charged bound states of WIMP Minimal Dark Matter, specifically a Majorana fermionic 5-plet, can be discovered with low statistics by running above the kinematic threshold, at a center-of-mass energy just slightly above the mass of the MDM bound state. This opens up a very interesting possibility for the discovery of WIMPs, complementary to the search for the resonant production of the neutral MDM bound state component, which relies on an on-peak search. For 5-plet MDM, indeed, the proposed search strategy is more efficient than the WIMP searches based on mono-X, missing-mass and disappearing tracks signatures.

   hep-phhep-exJHEP(2023)·19 citations
2. 02*

   Probing Gluon Bose Correlations in Nuclear Wave Function in Deep Inelastic Scattering

   Alex Kovner🇺🇸 · Ming Li🇺🇸 · Vladimir V. Skokov🇺🇸

   We extend the results of [Phys.Rev.Lett. 128 (2022) 18], where we argued that in the controlled environment of the Deep Inelastic Scattering experiments, Bose-Einstein correlation between gluons in a hadronic wave function can be accessed through the production of the diffractive dijet plus a third jet. In this observable, Bose-Einstein correlation causes the enhancement of the production cross sections at the zero relative angle between the transverse momentum imbalance of the photon-going dijet and the transverse momentum of the gluon jet, when the magnitude of the momentum imbalance is about the same as the magnitude of the produced gluon. In the present paper, we account for multiple scattering and non-linear effect in the target wave function. Although our equations can be applied to any high-energy DIS kinematics, to make them tractable numerically, we consider the high-momentum limit (momentum larger than $Q_s$) for the total momentum of the dijet, momentum imbalance, and the momentum of the produced gluon. By performing explicit numerical calculations, we confirm that the signal is present after accounting for multiple scattering.

   hep-phPRD(2023)·2 citations
3. 03*

   Probing gluon saturation via diffractive jets in ultra-peripheral nucleus-nucleus collisions

   E. Iancu🇫🇷 · A.H. Mueller🇺🇸 · D.N. Triantafyllopoulos🇮🇹 · S.Y. Wei🇨🇳

   We argue that semi-inclusive photo-production of a pair of hard jets via coherent diffraction in nucleus-nucleus ultra-peripheral collisions at high energy is a golden channel to study gluon saturation. The dominant contribution is the diffractive production of three jets in an asymmetric configuration. Two of the jets are hard and propagate at nearly central pseudo-rapidities. The third jet is semi-hard, with transverse momentum comparable to the nuclear saturation momentum, and is well separated in pseudo-rapidity from the hard dijets. The emission of the semi-hard jet allows for strong scattering, thus avoiding the "higher-twist" suppression of the exclusive dijet production due to colour transparency. We compute the trijet cross-section using the diffractive TMD factorisation which emerges from the CGC effective theory at high energy. The cross-section is controlled by gluon saturation, which leaves its imprints on the structure of the final state, notably on the rapidity distribution.

   hep-phnucl-thEPJC(2023)·29 citations
4. 04*

   Polarised parton distribution functions and proton spin

   Peng Cheng🇨🇳 · Yang Yu🇨🇳 · Hui-Yu Xing🇨🇳 · Chen Chen🇨🇳 · Zhu-Fang Cui🇨🇳 · Craig D. Roberts🇨🇳

   Supposing there exists an effective charge which defines an evolution scheme for both unpolarised and polarised parton distribution functions (DFs) that is all-orders exact and using Ansätze for hadron-scale proton polarised valence quark DFs, constrained by flavour-separated axial charges and insights from perturbative quantum chromodynamics, predictions are delivered for all proton polarised DFs at the scale ${\zeta }_{\mathrm{C}}^2=3$GeV${}^2$. The pointwise behaviour of the predicted DFs and, consequently, their moments, compare favourably with results inferred from data. Notably, flavour-separated singlet polarised DFs are small. On the other hand, the polarised gluon DF, $\Delta G(x;{\zeta }_{\mathrm{C}})$, is large and positive. Using our result, we predict ${\int }_{0.05}^{1}dx\Delta G(x;{\zeta }_{\mathrm{C}})=0.214(4)$ and that experimental measurements of the proton flavour-singlet axial charge should return $a_0^{\mathrm{E}}({\zeta }_{\mathrm{C}})=0.35(2)$.

   hep-phhep-exhep-latnucl-ex+1PLB(2023)·29 citations
5. 05*

   Ultra-peripheral nuclear collisions

   C. A. Bertulani🇺🇸

   This article presents a very brief review of the physics of Ultra-Peripheral Collisions (UPC) at the Large Hadron Collider (LHC) and other nuclear facilities. I discuss several processes of interest such as electron-position pair production, the anti-hydrogen atom, giant resonances, exotic meson production and parton distribution functions.

   hep-phnucl-exnucl-thJ.Phys.Conf.Ser.(2023)·5 citations
6. 06*

   Double Parton Distributions from Euclidean Lattice

   Jian-Hui Zhang🇨🇳

   We show that double parton distributions, which are important in describing double parton scattering processes in hadron collisions, can be directly computed from correlations of equal-time nonlocal Euclidean operators on the lattice in the large hadron momentum limit. We demonstrate this by taking the unpolarized color singlet quark double parton distribution as an example, and present a factorization formula connecting the corresponding lightcone and Euclidean correlations. This opens a new possibility of studying multiparton interactions on the Euclidean lattice.

   hep-phhep-latnucl-th14 citations
7. 07*

   Searching for high-frequency axion in quantum electromagnetodynamics through interface haloscopes

   Tong Li🇨🇳 · Chang-Jie Dai🇨🇳 · Rui-Jia Zhang🇨🇳

   The so-called Witten effect implies the existence of electromagnetic interactions between axion and magnetic monopole due to the axion-photon coupling. A sound quantization in the presence of magnetic monopoles, called quantum electromagnetodynamics (QEMD), was utilized to construct a more generic axion-photon Lagrangian in the low-energy axion effective field theory. This generic axion-photon Lagrangian introduces the interactions between axion and two four-potentials, and leads to new axion-modified Maxwell equations. The interface haloscopes place an interface between two electromagnetic media with different properties and are desirable to search for high-mass axions $m_a\gtrsim \mathcal{O}(10)\mu \mathrm{eV}$. In this work, for the generic axion-photon couplings built under QEMD, we perform comprehensive calculations of the axion-induced propagating waves and energy flux densities in different interface setups. We also obtain the sensitivity to new axion-photon couplings for high-mass axions.

   hep-phhep-exPRD(2024)·8 citations
8. 08*

   Type-II Majoron Dark Matter

   Carla Biggio🇮🇹 · Lorenzo Calibbi🇨🇳 · Toshihiko Ota🇪🇸 · Samuele Zanchini🇮🇹

   We discuss in detail the possibility that the ``type-II majoron'' -- that is, the pseudo Nambu-Goldstone boson that arises in the context of the type-II seesaw mechanism if the lepton number is spontaneously broken by an additional singlet scalar -- account for the dark matter (DM) observed in the universe. We study the requirements the model's parameters have to fulfill in order to reproduce the measured DM relic abundance through two possible production mechanisms in the early universe, freeze-in and misalignment, both during a standard radiation-dominated era and early matter domination. We then study possible signals of type-II majoron DM and the present and expected constraints on the parameter space that can be obtained from cosmological observations, direct detection experiments, and present and future searches for decaying DM at neutrino telescopes and cosmic-ray experiments. We find that -- depending on the majoron mass, the production mechanism, and the vacuum expectation value of the type-II triplet -- all of the three decay modes (photons, electrons, neutrinos) of majoron DM particles can yield observable signals at future indirect searches for DM. Furthermore, in a corner of the parameter space, detection of majoron DM is possible through electron recoil at running and future direct detection experiments.

   hep-phastro-ph.HEhep-exPRD(2023)·15 citations
9. 09*

   Thermal neutrino self-energy beyond the contact approximation

   Andrea Erdas🇺🇸

   Using the Schwinger proper time method I calculate exactly the bubble diagram contribution to the thermal neutrino self-energy, obtaining exact results that cannot be achieved using the contact approximation. These results allow me to obtain the dispersion relation for neutrino in a medium under several different conditions.

   hep-phInt.J.Mod.Phys.A(2023)·0 citations
10. 10*

    Analyzing the time spectrum of supernova neutrinos to constrain their effective mass or Lorentz Invariance Violation

    C. A. Moura🇧🇷 · L. Quintino🇧🇷 · F. Rossi-Torres🇧🇷

    We analyze the expected arrival time spectrum of supernova neutrinos using simulated luminosity and compute the expected number of events in future detectors such as the DUNE Far Detector and Hyper-Kamiokande. We develop a general method using minimum square statistics that can compute the sensitivity to any variable affecting neutrino time of flight. We apply this method in two different situations: First, we compare the time spectrum changes due to different neutrino mass values to put limits on electron (anti)neutrino effective mass. Second, we constrain Lorentz invariance violation through the mass scale, $M_{QG}$, at which it would occur. We consider two main neutrino detection techniques: 1. DUNE-like liquid argon TPC, for which the main detection channel is ${\nu }_e+{}^{40}\text{mbox}Ar\to e^{-}+{}^{40}\text{mbox}{K}^{\ast }$, related to the supernova neutronization burst; and 2. HyperK-like water Cherenkov detector, for which ${\bar{\nu }}_e+p\to e^{+}+n$ is the main detection channel. We consider a fixed supernova distance of 10~kpc and two different masses of the progenitor star: (i) 15~$M_{\odot }$ with neutrino emission time up to 0.3~s and (ii) 11.2~$M_{\odot }$ with neutrino emission time up to 10~s. The best mass limits at 3$\sigma$ are for $\mathcal{O}(1)$~eV. For ${\nu }_e$, the best limit comes from a DUNE-like detector if the mass ordering happens to be inverted. For ${\bar{\nu }}_e$, the best limit comes from a HyperK-like detector. The best limit for the Lorentz invariance violation mass scale at the 3$\sigma$ level considering a superluminal or subluminal effect is $M_{QG}\gtrsim 10^{13}$~GeV ($M_{QG}\gtrsim 5\times 10^5$~GeV) for linear (quadratic) energy dependence.

    hep-phUniverse(2023)·6 citations
11. 11*

    Non-thermal Higgs Spectrum in Reheating Epoch: Primordial Condensate vs. Stochastic Fluctuation

    Kunio Kaneta🇯🇵 · Kin-ya Oda🇯🇵

    Since electroweak symmetry is generally broken during inflation, the Standard Model Higgs field can become supermassive even after the end of inflation. In this paper, we study the non-thermal phase space distribution of the Higgs field during reheating, focusing in particular on two different contributions: primordial condensate and stochastic fluctuations. We obtain their analytic formulae, which agree with the previous numerical result. As a possible consequence of the non-thermal Higgs spectrum, we discuss perturbative Higgs decay during reheating for the case it is kinematically allowed. We find that the soft-relativistic and hard spectra are dominant in the decay rate of the stochastic fluctuation and that the primordial condensate and stochastic fluctuations decay almost at the same time.

    hep-phastro-ph.COJCAP(2023)·10 citations
12. 12*

    Enhanced Four-Body Decays of Charged Higgs Bosons into Off-Shell Pseudoscalar Higgs and $W^{\pm }$ Boson Pairs in a Lepton-Specific 2-Higgs Doublet Model

    Stefano Moretti🇬🇧 · Muyuan Song🇨🇳

    We study the time-honoured decay $H^{\pm }\to A{W}^{\pm }$ but for the first time, we do so for the case of both $A$ and $W^{\pm }$ being off-shell, therefore computing a $1\to 4$ body decay. We show that the corresponding decay rate not only extends the reach of $H^{\pm }$ searches to small masses of the latter but also that the results of our implementation differ significantly from the yield of the $1\to 3$ body decay over the phase space region in which the latter is normally used. We show the phenomenological relevance of this implementation in the case of the so-called lepton-specific 2-Higgs Doublet Model (2HDM) over the mass region wherein the aforementioned $1\to 4$ body decay can dominate just beyond the top (anti)quark mass. This mass region is accessible in the lepton-specific 2HDM as the Yukawa couplings are such that limits from $b\to s\gamma$ and $\tau \to \mu {\nu }_{\tau }\overline{{\nu }_{\mu }}$ observables on $M_{H^{\pm }}$ are rather mild. However, we emphasise that similar effects may occur in other 2HDM types, as the $W^{\pm }{H}^{\mp }A$ vertex is 2HDM type independent.

    hep-phEPJC(2024)·0 citations
13. 13*

    An Augmented QCD Phase Portrait: Mapping Quark-Hadron Deconfinement for Hot, Dense, Rotating Matter under Magnetic Field

    Gaurav Mukherjee🇮🇳 · D. Dutta🇮🇳 · D. K. Mishra🇮🇳

    The quark-hadron transition that happens in ultra-relativistic heavy-ion collisions is expected to be influenced by the effects of rotation and magnetic field, both present due to the geometry of a generic non-head-on impact. We augment the conventional $T$--${\mu }_B$ planar phase diagram for QCD matter by extending it to a multi-dimensional domain spanned by temperature $T$, baryon chemical potential ${\mu }_B$, external magnetic field $B$ and angular velocity $\omega$. Using two independent approaches, one from a rapid rise in entropy density and another dealing with a dip in the squared speed of sound, we identify deconfinement in the framework of a modified statistical hadronization model. We find that the deconfinement temperature $T_C({\mu }_B,\omega ,eB)$ decreases nearly monotonically with increasing ${\mu }_B,\omega$ and $eB$ with the most prominent drop (by nearly $40$ to $50$ MeV) in $T_C$ occurring when all the three quasi-control (via collision energy and centrality) parameters are simultaneously tuned to finite values that are typically achievable in present and upcoming heavy-ion colliders.

    hep-phnucl-exnucl-thPLB(2023)·14 citations
14. 14*

    More Synergies from Beauty, Top, $Z$ and Drell-Yan Measurements in SMEFT

    Cornelius Grunwald🇩🇪 · Gudrun Hiller🇩🇪 · Kevin Kröninger🇩🇪 · Lara Nollen🇩🇪

    We perform a global analysis of Beauty, Top, $Z$ and Drell-Yan measurements in the framework of the Standard Model effective theory (SMEFT). We work within the minimal flavor violation (MFV) hypothesis, which relates different sectors and generations beyond the $SU(2{)}_L$-link between left-handed top and beauty quarks. We find that the constraints on the SMEFT Wilson coefficients from the combined analysis are stronger than the constraints from a fit to the individual sectors, highlighting synergies in the global approach. We also show that constraints within MFV are strengthened compared to single-generation fits. The strongest bounds are obtained for the semileptonic four-fermion triplet operator $C_{lq}^{(3)}$, probing scales as high as $18$ TeV, followed by the gluon dipole operator $C_{uG}$ with $7$ TeV, and other four-fermion and penguin operators in the multi-TeV range. Operators with left-handed quark bilinears receive order one contributions from higher orders in the MFV expansion induced by the top Yukawa coupling as a result of the FCNC $b\to s\mu \mu$ anomalies combined with the other sectors. We predict the $68\%$ credible intervals of the dineutrino branching ratios within MFV as $5.3\cdot 10^{-6}\le \mathcal{B}(B^0\to K^{\ast 0}\nu \bar{\nu })\le 12.8\cdot 10^{-6}$ and $2.5\cdot 10^{-6}\le \mathcal{B}(B^{+}\to K^{+}\nu \bar{\nu })\le 5.9\cdot 10^{-6}$, which include the respective Standard Model predictions, and are in reach of the Belle II experiment. We show how future measurements of the dineutrino branching ratios can provide insights into the structure of new physics in the global fit.

    hep-phhep-exJHEP(2023)·69 citations
15. 15*

    Small $x$ Physics Beyond Eikonal Approximation: an Effective Hamiltonian Approach

    Ming Li🇺🇸

    Understanding the spin structure of hadrons in the small $x$ regime is an important direction to unravel the spin puzzle in hadronic physics. To include spin degrees of freedom in the small $x$ regime requires going beyond the usual eikonal approximation in high energy QCD. We developed an effective Hamiltonian approach to study spin related observables in the small $x$ regime using the shockwave formalism. The small-$x$ effective Hamiltonian incorporates both quark and gluon propagators in the background fields and the background field induced interaction vertices up to next-to-eikonal order. A novel feature of sub-eikonal interactions is the background gluon field induced gluon radiation inside the shockwave. Its relation to chromo-electrically polarized Wilson line correlator is established both in small $x$ helicity evolution and in longitudinal double-spin asymmetry for gluon production.

    hep-phJHEP(2023)·33 citations
16. 16*

    Tagging a Boosted Top quark with a $\tau$ final state

    Amit Chakraborty🇮🇳 · Amandip De🇮🇳 · Rohini M. Godbole🇮🇳 · Monoranjan Guchait🇮🇳

    Boosted top quark tagging is one of the challenging, and at the same time exciting, tasks in high energy physics experiments, in particular in the exploration of new physics signals at the LHC. Several techniques have already been developed to tag a boosted top quark in its hadronic decay channel. Recently tagging the same in the semi-leptonic channel has begun to receive a lot of attention. In the current study, we develop a methodology to tag a boosted top quark ($p_T>$ 200 GeV) in its semi-leptonic decay channel with a $\tau$-lepton in the final state. In this analysis, the constituents of the top fatjet are reclustered using jet substructure technique to obtain the subjets, and then $b$- and $\tau$- like subjets are identified by applying standard $b$- and $\tau$-jet identification algorithms. We show that the dominant QCD background can be rejected effectively using several kinematic variables of these subjects, such as energy sharing among the jets, invariant mass, transverse mass, Nsubjettiness etc., leading to high signal tagging efficiencies. We further assess possible improvements in the results by employing multivariate analysis techniques. We find that using this proposed top-tagger, a signal efficiency of $\sim 77\%$ against a background efficiency of $\sim 3\%$ can be achieved. We also extend the proposed top-tagger to the case of polarized top quarks by introducing a few additional observables calculated in the rest frame of the $b-\tau$ system. We comment on how the same methodology will be useful for tagging a boosted heavy BSM particle with a $b$ and $\tau$ in the final state.

    hep-phhep-exPRD(2023)·2 citations
17. 17*

    Automated choice of the best renormalization scheme

    S. Heinemeyer🇪🇸 · F. von der Pahlen🇨🇴

    High-precision predictions in BSM models require calculations at the loop-level and thus a renormalization of (some of) the BSM parameter. Here many choices for the renormalization scheme (RS) are possible. A given RS can be well suited to yield ``stable'' and ``well behaved'' higher-order corrections in one part of the BSM parameter space, but can fail completely in other parts. The latter may not even be noticed numerically if an isolated parameter point is investigated. Here we review a new method for choosing a ``well behaved'' RS. We demonstrate the feasibility of our new method in the chargino/neutralino sector of the Minimal Supersymmetric Standard Model (MSSM), but stress the general applicability of our method to all types of BSM models.

    hep-phPoS(2022)·2 citations
18. 18*

    Production rates of dark photons and $Z^{\prime }$ in the Sun and stellar cooling bounds

    Shao-Ping Li🇨🇳 · Xun-Jie Xu🇨🇳

    Light weakly interacting particles could be copiously produced in the Sun which, as a well-understood star, could provide severe constraints on such new physics. In this work, we calculate the solar production rates of light gauge bosons (e.g. dark photon) arising from various $U(1)$ extensions of the standard model. It is known that the dark photon production rate is suppressed by the dark photon mass if it is well below the plasmon mass of the medium. We show that for more general $U(1)$ gauge bosons, this suppression is absent if the couplings are not in alignment with those of the photon. We investigate a few frequently discussed $U(1)$ models including $B-L$, $L_{\mu }-L_{\tau }$, and $L_e-L_{\mu (\tau )}$, and derive the stellar cooling bounds for these models.

    hep-phastro-ph.COastro-ph.SRhep-exJCAP(2023)·57 citations
19. 19*

    Self-consistent optimization of the $z$-Expansion for $B$ meson decays

    Daniel Simons🇺🇸 · Erik Gustafson🇺🇸 · Yannick Meurice🇺🇸

    We discuss the self-consistency imposed by the analyticity of regular parts of form factors, appearing in the $z$-expansion for semileptonic $B$-meson decays, when fitted in different kinematic regions. Relying on the uniqueness of functions defined by analytic continuation, we propose four metrics which measure the departure from the ideal analytic self-consistency. We illustrate the process using Belle data for $B\to D\ell {\nu }_{\ell }$. For this specific example, the metrics provide consistent indications that some choices (order of truncation, BGL or BCL) made in the form of the $z$-expansion can be optimized. However, other choices ($z$-origin, location of isolated poles and threshold constraints) appear to have very little effect on these metrics. We briefly discuss the implication for optimization of the $z$-expansion for nucleon form factors relevant for neutrino oscillation experiments.

    hep-phhep-latPRD(2024)·2 citations
20. 20*

    Preheating in Einstein-Cartan Higgs Inflation: Oscillon formation

    Matteo Piani🇵🇹 · Javier Rubio🇪🇸

    We make use of classical lattice simulations in 3 + 1 dimensions to study the preheating stage of Higgs Inflation in Einstein-Cartan gravity. Focusing for concreteness on a simplified scenario involving the seminal Nieh-Yan term, we demonstrate the formation of dense and spatially localized oscillon configurations constituting up to 70% of the total energy density. The emergence of these meta-stable objects may lead to a prolonged period of matter domination, effectively modifying the post-inflationary history of the Universe as compared to the metric and Palatini counterparts. Notably, the creation of oscillons comes together with a significant gravitational wave signal, whose typical frequency lies, however, beyond the range accessible by existing and planned gravitational wave experiments. The impact of the Standard Model gauge bosons and fermions and the potential extension of our results to more general Einstein-Cartan settings is also discussed.

    hep-phastro-ph.COgr-qcJCAP(2023)·40 citations
21. 21*

    Universal dynamics and non-thermal fixed points in quantum fluids far from equilibrium

    Aleksandr N. Mikheev🇩🇪 · Ido Siovitz🇩🇪 · Thomas Gasenzer🇩🇪

    Closed quantum systems far from thermal equilibrium can show universal dynamics near attractor solutions, known as non-thermal fixed points, generically in the form of scaling behavior in space and time. A systematic classification and comprehensive understanding of such scaling solutions are tasks of future developments in non-equilibrium quantum many-body theory. In this tutorial review, we outline several analytical approaches to non-thermal fixed points and summarize corresponding numerical and experimental results. The analytic methods include a non-perturbative kinetic theory derived within the two-particle irreducible effective-action formalism, as well as a low-energy effective field theory framework. As one of the driving forces of this research field are numerical simulations, we summarize the main results of exemplary cases of universal dynamics in ultracold Bose gases. This encompasses quantum vortex ensembles in turbulent superfluids as well as recently observed real-time instanton solutions in one-dimensional spinor condensates.

    ↳ cond-mat.quant-gashep-phnlin.PSEur.Phys.J.ST(2023)·20 citations
22. 22*

    Evolution of Resonant Self-interacting Dark Matter Halos

    Ayuki Kamada🇵🇱 · Hee Jung Kim🇰🇷

    Recent analysis on the stellar kinematics of ultra-faint dwarf (UFD) galaxies has put a stringent upper limit on the self-scattering cross section of dark matter, i.e., $\sigma /m<\mathcal{O}(0.1)\mathrm{c}{\mathrm{m}}^2/g$ at the scattering velocity of $\mathcal{O}(10)km/s$. Resonant self-interacting dark matter (rSIDM) is one possibility that can be consistent with the UFDs and explain the low central densities of rotation-supported galaxies; the cross section is resonantly enhanced to be $\sigma /m=\mathcal{O}(1)\mathrm{c}{\mathrm{m}}^2/g$ around the scattering velocity of $\mathcal{O}(100)km/s$ while being suppressed at lower velocities. To further assess this possibility, since the inferred dark matter distribution of halos from astrophysical observations is usually compared to that in constant-cross section SIDM (cSIDM), whether the structures of rSIDM halos can be approximated by the cSIDM halo profiles needs to be clarified. In this work, we employ the grovothermal fluid method to investigate the structural evolution of rSIDM halos in a wide mass range. We find that except for halos in a specific mass range, the present structures of rSIDM halos are virtually indistinguishable from those of the cSIDM halos. For halos in the specific mass range, the resonant self-scattering renders a break in their density profile. We demonstrate how such a density-profile break appears in astrophysical observations, e.g., rotation curves and line-of-sight velocity dispersion profiles. We show that for halos above the specific mass range, the density-profile break thermalizes to disappear before the present. We demonstrate that such distinctive thermalization dynamics can leave imprints on the orbital classes of stars with similar ages and metallicities.

    ↳ astro-ph.COastro-ph.GAhep-phPRD(2024)·5 citations
23. 23*

    Random model of flow decorrelation

    Piotr Bozek🇵🇱 · Hadi Mehrabpour🇩🇪

    The collective flow generated in relativistic heavy-ion collisions fluctuates from event to event. The fluctuations lead to a decorrelation of flow vectors measured in separate bins in phase space. These effects have been measured in experiments and observed in numerical simulations in hydrodynamic models. We present a simple random model of flow decorrelation in pseudorapidity. Analytical expressions for the flow factorization breaking coefficients for flow vectors, flow vector magnitudes, and flow angles are derived. The model explains the relations between different factorization breaking coefficients found in experimental data and model simulations. In particular, it is found that the flow angle decorrelation constitutes about one half of the total flow vector decorrelation.

    ↳ nucl-thhep-phnucl-exPRC(2023)·3 citations
24. 24*

    Lorentz Violation in Finsler Geometry

    Jie Zhu🇨🇳 · Bo-Qiang Ma🇨🇳

    Lorentz invariance is one of the foundations of modern physics; however, Lorentz violation may happen from the perspective of quantum gravity, and plenty of studies on Lorentz violation have arisen in recent years. As a good tool to explore Lorentz violation, Finsler geometry is a natural and fundamental generalization of Riemann geometry. The Finsler structure depends on both coordinates and velocities. Here, we simply introduce the mathematics of Finsler geometry. We review the connection between modified dispersion relations and Finsler geometries and discuss the physical influence from Finsler geometry. We review the connection between Finsler geometries and theories of Lorentz violation, such as the doubly special relativity, the standard-model extension, and the very special relativity.

    ↳ gr-qcastro-ph.HEhep-phSymmetry(2023)·14 citations
25. 25*

    Exploring the effects of electromagnetic fields and tilted bulk distribution on directed flow of D mesons in small systems

    Yifeng Sun🇨🇳 · Salvatore Plumari🇮🇹 · Santosh K. Das🇮🇳

    We studied the directed flow of heavy quarks in small systems produced in p-Pb collisions due to both the impact of initial vorticity and electromagnetic fields. We employed a relativistic transport code to model the bulk evolution of the small systems and studied the heavy quark momentum evolution using Langevin dynamics. For the heavy quarks interaction with the bulk, we employed a quasiparticle model (QPM). We observed a large directed flow splitting ($\Delta v_1$) of charm quarks due to electromagnetic fields, which is comparable to the directed flow splitting of charm quarks in nucleus-nucleus collisions. However, the magnitude of the directed flow due to the initial tilted matter distribution in p-nucleus collisions is not substantial. The observed directed flow is not rapidity odd due to the asymmetry in the colliding system. The results presented in this manuscript provide an independent way to quantify the initial electromagnetic field produced and the matter distributed in small systems.

    ↳ nucl-thhep-exhep-phPLB(2023)·24 citations
26. 26*

    Searching For Stochastic Gravitational Waves Below a Nanohertz

    William DeRocco🇺🇸 · Jeff A. Dror🇺🇸

    The stochastic gravitational-wave background is imprinted on the times of arrival of radio pulses from millisecond pulsars. Traditional pulsar timing analyses fit a timing model to each pulsar and search the residuals of the fit for a stationary time correlation. This method breaks down at gravitational-wave frequencies below the inverse observation time of the array; therefore, existing analyses restrict their searches to frequencies above 1 nHz. An effective method to overcome this challenge is to study the correlation of secular drifts of parameters in the pulsar timing model itself. In this paper, we show that timing model correlations are sensitive to sub-nanohertz stochastic gravitational waves and perform a search using existing measurements of pulsar spin-decelerations and pulsar binary orbital decay rates. We do not observe a signal at our present sensitivity, constraining the stochastic gravitational-wave relic energy density to ${\Omega }_{\text{GW}}(f)<3.8\times 10^{-9}$ at 450~pHz with sensitivity which scales as the frequency squared until approximately 10 pHz. We place additional limits on the amplitude of a power-law spectrum of $A_{\star }\lesssim 1.8\times 10^{-14}$ for a reference frequency of $f_{\ast }=1{\mathrm{year}}^{-1}$ and the spectral index expected from supermassive black hole binaries, $\gamma =13/3$. If detection of a supermassive black hole binary signal above 1 nHz is confirmed, this search method will serve as a critical complementary probe of the dynamics of galaxy evolution.

    ↳ astro-ph.HEastro-ph.IMgr-qchep-phPRD(2023)·29 citations
27. 27*

    Do we have enough evidence to invalidate the mean-field approximation adopted to model collective neutrino oscillations?

    Shashank Shalgar🇩🇰 · Irene Tamborra🇩🇰

    Recent body of work points out that the mean-field approximation, widely employed to mimic the neutrino field within a neutrino-dense source, might give different results in terms of flavor evolution with respect to the correspondent many-body treatment. In this paper, we investigate whether such conclusions derived within a constrained framework should hold in an astrophysical context. We show that the plane waves, commonly adopted in the many-body literature to model the neutrino field, provide results that are crucially different with respect to the ones obtained using wavepackets of finite size streaming with a non-zero velocity. The many-body approach intrinsically includes coherent and incoherent scatterings. The mean-field approximation, on the other hand, only takes into account the coherent scattering in the absence of the collision term. Even if incoherent scatterings are included in the mean-field approach, the nature of the collision term is different from that in the many-body approach. Because of this, if only a finite number of neutrinos is considered, as often assumed, the two approaches naturally lead to different flavor outcomes. These differences are further exacerbated by vacuum mixing. We conclude that existing many-body literature, based on closed neutrino systems with a finite number of particles, is neither able to rule out nor assess the validity of the mean-field approach adopted to simulate the evolution of the neutrino field in dense astrophysical sources, which are open systems.

    ↳ astro-ph.HEhep-phnucl-thPRD(2023)·35 citations
28. 28*

    On Entropy Growth in Perturbative Scattering

    Clifford Cheung🇺🇸 · Temple He🇺🇸 · Allic Sivaramakrishnan🇺🇸

    Inspired by the second law of thermodynamics, we study the change in subsystem entropy generated by dynamical unitary evolution of a product state in a bipartite system. Working at leading order in perturbative interactions, we prove that the quantum $n$-Tsallis entropy of a subsystem never decreases, $\Delta S_n\ge 0$, provided that subsystem is initialized as a statistical mixture of states of equal probability. This is true for any choice of interactions and any initialization of the complementary subsystem. When this condition on the initial state is violated, it is always possible to explicitly construct a "Maxwell's demon" process that decreases the subsystem entropy, $\Delta S_n<0$. Remarkably, for the case of particle scattering, the circuit diagrams corresponding to $n$-Tsallis entropy are the same as the on-shell diagrams that have appeared in the modern scattering amplitudes program, and $\Delta S_n\ge 0$ is intimately related to the nonnegativity of cross-sections.

    ↳ hep-thhep-phquant-phPRD(2023)·28 citations
29. 29*

    Halo Formation from Yukawa Forces in the Very Early Universe

    Guillem Domènech🇩🇪 · Derek Inman🇯🇵 · Alexander Kusenko🇺🇸 · Misao Sasaki🇯🇵

    If long-range attractive forces exist and are stronger than gravity then cosmic halo formation can begin in the radiation-dominated era. We study a simple realization of this effect in a system where dark matter fermions have Yukawa interactions mediated by scalar particles, analogous to the Higgs boson in the standard model. We develop a self-consistent description of the system including exact background dynamics of the scalar field, and precise modelling of the fermion density fluctuations. For the latter, we provide accurate approximations for the linear growth as well as quantitative modelling of the nonlinear evolution using N-body simulations. We find that halo formation occurs exponentially fast and on scales substantially larger than simple estimates predict. The final fate of these halos remains uncertain, but could be annihilation, dark stars, primordial black holes, or even the existence of galaxy-sized halos at matter-radiation equality. More generally, our results demonstrate the importance of mapping scalar-mediated interactions onto structure formation outcomes and constraints for beyond the standard model theories.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2023)·48 citations
30. 30*

    Boson Star Normal Modes

    James Hung-Hsu Chan🇺🇸 · Sergey Sibiryakov🇨🇦 · Wei Xue🇺🇸

    Boson stars are gravitationally bound objects that arise in ultralight dark matter models and form in the centers of galactic halos or axion miniclusters. We systematically study the excitations of a boson star, taking into account the mixing between positive and negative frequencies introduced by gravity. We show that the spectrum contains zero-energy modes in the monopole and dipole sectors resulting from spontaneous symmetry breaking by the boson star background. We analyze the general properties of the eigenmodes and derive their orthogonality and completeness conditions which have non-standard form due to the positive-negative frequency mixing. The eigenvalue problem is solved numerically for the first few energy levels in different multipole sectors and the results are compared to the solutions of the Schrödinger equation in fixed boson star gravitational potential. The two solutions differ significantly for the lowest modes, but get close for higher levels. We further confirm the normal mode spectrum in 3D wave simulations where we inject perturbations with different multipoles. As an application of the normal mode solutions, we compute the matrix element entering the evaporation rate of a boson star immersed in a hot axion gas. The computation combines the use of exact wavefunctions for the low-lying bound states and of the Schrödinger approximation for the high-energy excitations.

    ↳ astro-ph.COhep-phhep-thJHEP(2023)·12 citations
31. 31*

    Bouncing and inflationary dynamics in quantum cosmology in the de Broglie-Bohm interpretation

    G. S. Vicente🇧🇷 · Rudnei O. Ramos🇧🇷 · Vitória N. Magalhães🇧🇷

    The quantum cosmology of the flat Friedmann-Lemaître-Robertson-Walker Universe, filled with a scalar field, is considered in the de Broglie-Bohm (dBB) interpretation framework. A stiff-matter quantum bounce solution is obtained. The bouncing and subsequent pre-inflationary and inflationary dynamics are studied in details. We consider some representative primordial inflation models as examples, for which analytical expressions characterizing the dynamical quantities can be explicitly derived. The dependence of the inflationary dynamics on the quantum bounce parameters is then analyzed. The parameters emerging from our description are constrained by requiring the produced dynamics to be in accordance with some key cosmological quantities. The constraining conditions are also illustrated through regions of parameter space in terms of the bounce quantities.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2023)·6 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.