Tue·Aug 8, 2023Tuesday·August 8, 2023

1. 01*

   A multistage framework for studying the evolution of jets and high-$p_T$ probes in small collision systems

   Abhijit Majumder · Aaron Angerami · Ritu Arora · Steffen Bass · Shanshan Cao · Yi Chen · Raymond Ehlers · Hannah Elfner · Wenkai Fan · Rainer J. Fries · Charles Gale · Yayun He and 39 other authors

   Understanding the modification of jets and high-$p_T$ probes in small systems requires the integration of soft and hard physics. We present recent developments in extending the JETSCAPE framework to build an event generator, which includes correlations between soft and hard partons, to study jet observables in small systems. The multi-scale physics of the collision is separated into different stages. Hard scatterings are first sampled at binary collision positions provided by the Glauber geometry. They are then propagated backward in space-time following an initial-state shower to obtain the initiating partons' energies and momenta before the collision. These energies and momenta are then subtracted from the incoming colliding nucleons for soft-particle production, modeled by the 3D-Glauber + hydrodynamics + hadronic transport framework. This new hybrid approach (X-SCAPE) includes non-trivial correlations between jet and soft particle productions in small systems. We calibrate this framework with the final state hadrons' $p_T$-spectra from low to high $p_T$ in $p$-$p$, and and then compare with the spectra in $p$-$Pb$ collisions from the LHC. We also present results for additional observables such as the distributions of event activity as a function of the hardest jet $p_T$ in forward and mid-rapidity for both $p$-$p$ and $p$-$Pb$ collisions.

   hep-phnucl-exnucl-thPoS(2024)·2 citations
2. 02*

   Future Top Quark Pole Mass Improvements from PDF Updates

   Jason Gombas🇺🇸 · Reinhard Schwienhorst🇺🇸 · Jarrett Fein🇺🇸 · Sara Sawford🇺🇸

   The dependence of the top-quark mass measurement in top-quark pair production on the parton distribution functions (PDF) is explored through differential mass distributions in $t\bar{t}$ and $t\bar{t}j$ production at the LHC and a future 100 TeV proton-proton collider. The top-quark mass uncertainty is obtained from chi-squared fits to invariant mass distributions from simulations assuming different top pole masses around the nominal value of 172.5 GeV. The PDF uncertainties of the differential distributions are used in the chi-square evaluation and reduced through a fit to differential distributions in $t\bar{t}$ and $t\bar{t}j$ production.

   hep-ph0 citations
3. 03*

   Improving sensitivity of trilinear RPV SUSY searches using machine learning at the LHC

   Arghya Choudhury🇮🇳 · Arpita Mondal🇮🇳 · Subhadeep Mondal🇮🇳 · Subhadeep Sarkar🇮🇳

   In this work, we have explored the sensitivity of multilepton final states in probing the gaugino sector of R-parity violating supersymmetric scenario with specific lepton number violating trilinear couplings (${\lambda }_{ijk}$) being non-zero. The gaugino spectrum is such that the charged leptons in the final state can arise from the R-parity violating decays of the lightest supersymmetric particle (LSP) as well as R-parity conserving decays of the next-to-LSP (NLSP). Apart from a detailed cut-based analysis, we have also performed a machine learning-based analysis using boosted decision tree algorithm which provides much better sensitivity. In the scenarios with non-zero ${\lambda }_{121}$ and/or ${\lambda }_{122}$ couplings, the LSP pair in the final states decays to $4l(l=e,\mu )+\mathrm{E}{/}_{\mathrm{T}}$ final states with $100\%$ branching ratio. We have shown that under this circumstance, a final state with $\ge 4l$ has the highest sensitivity in probing the gaugino masses. We also discuss how the sensitivity can change in the presence of $\tau$ lepton(s) in the final state due to other choices of trilinear couplings. We present our results through the estimation of the discovery and exclusion contours in the gaugino mass plane for both the HL-LHC and the HE-LHC. For ${\lambda }_{121}$ and/or ${\lambda }_{122}$ nonzero scenario, the projected 2$\sigma$ exclusion limit on NLSP masses reaches upto 2.37 TeV and 4 TeV for the HL-LHC and the HE-LHC respectively by using a machine learning based algorithm. We obtain an enhancement of $\sim$ 380 (190) GeV in the projected 2$\sigma$ exclusion limit on the NLSP masses at the 27 (14) TeV LHC. Considering the same final state ($N_l\ge 4$) for ${\lambda }_{133}$ and/or ${\lambda }_{233}$ non-zero scenario, we find that the corresponding 2$\sigma$ projected limits are $\sim$ 1.97 TeV and $\sim$ 3.25 TeV for the HL-LHC and HE-LHC respectively.

   hep-phhep-exPRD(2024)·14 citations
4. 04*

   Early time dynamics and constraints on medium evolution

   Kirill Boguslavski🇦🇹

   In relativistic heavy-ion collisions, a quark-gluon plasma (QGP) is created whose pre-equilibrium evolution includes a rich variety of exciting phenomena of Quantum Chromodynamics. In these Proceedings, we provide a short overview of our current understanding of the pre-equilibrium dynamics of the QGP from a weak-coupling perspective and highlight recent developments. Focusing on new studies, we then discuss how initial stages of the QGP medium may impact hard probes including direct photons, dileptons, jets, and heavy quarks. This introduces promising opportunities to obtain experimental signatures of the pre-equilibrium QGP.

   hep-phhep-exnucl-thPoS(2024)·0 citations
5. 05*

   Sizing the double pole resonant enhancement in $e^{+}{e}^{-}\to {\pi }^0{\pi }^0\gamma$ cross section and ${\tau }^{-}\to {\pi }^{-}{\pi }^0{\nu }_{\tau }\gamma$ decay

   Leonardo Esparza-Arellano🇲🇽 · Antonio Rojas🇲🇽 · Genaro Toledo🇲🇽

   The enhancement mechanism due to the resonant properties of the $\rho$ and $\omega$ mesons, which are close in mass, are analysed when such resonances carry different momenta. Considerations from the particular process where they appear to the individual resonant features are at play for the appearance of the global resonant manifestation. In this work, we first consider the $e^{+}{e}^{-}\to {\pi }^0{\pi }^0\gamma$ process. We use the differential cross section at a given angle of emission of one of the pions, to tune the individual features of the two resonances and exhibit how both resonances combine to produce the enhancement. Then, we incorporate the ${\rho }^{\prime }$ using the information obtained from the $e^{+}{e}^{-}\to {\pi }^0{\pi }^0\gamma$ total scattering process and show that, it becomes important thanks to the same enhancement mechanism between the $\rho$ and the $\omega$. In a second step, we use a similar approach to describe a model dependent contribution to the ${\tau }^{-}\to {\pi }^{-}{\pi }^0{\nu }_{\tau }\gamma$ decay, the so-called $\omega$ channel. We show that the dipion invariant mass distribution at particular angles is sensitive to the individual resonant states. We compute the interference of this channel with the known dominant model independent contribution, and show how a better knowledge of the $e^{+}{e}^{-}\to {\pi }^0{\pi }^0\gamma$ process can help to properly account for such model dependent effects. The implication on the isospin symmetry breaking correction to tau-based estimates of the muon magnetic dipole moment is assessed.

   hep-phPRD(2023)·6 citations
6. 06*

   Forward production of prompt neutrinos in the atmosphere and at high-energy colliders

   Yu Seon Jeong🇰🇷 · Weidong Bai🇨🇳 · Milind Diwan🇺🇸 · Maria Vittoria Garzelli🇩🇪 · Karan Kumar🇺🇸 · Mary Hall Reno🇺🇸

   The atmospheric neutrino flux at very high energies is dominated by prompt neutrinos, mostly contributed by the decays of charmed hadrons produced in the forward direction by cosmic ray interactions with air nuclei. Theoretical predictions of the prompt atmospheric neutrino flux have large uncertainties mainly related to charm hadron production. Prompt neutrinos can also be studied through high-energy colliders. In particular, two ongoing forward experiments and the proposed Forward Physics Facility at the LHC can detect forward prompt neutrinos. We will present the kinematic regions relevant to the prompt atmospheric neutrino flux in terms of collider kinematic variables, the collision energy $\sqrt{s}$ and the center-of-mass rapidity of charm hadrons $y$, and discuss implications of the forward experiments at the LHC on the theoretical predictions of the prompt atmospheric neutrino flux.

   hep-phastro-ph.HEPoS(2023)·5 citations
7. 07*

   Simulation-based inference in the search for CP violation in leptonic WH production

   Ricardo Barrué🇵🇹 · Patricia Conde-Muíño🇵🇹 · Valerio Dao🇨🇭 · Rui Santos🇵🇹

   Sources of CP violation beyond the Standard Model (BSM) are required to explain the baryonic asymmetry of the Universe. In this work, we study BSM CP-violating components in the HWW interaction in WH production, parametrized by an effective dimension-6 CP-odd operator. We explore a machine learning simulation-based inference method that estimates a detector-level optimal observable - SALLY - comparing it with energy-dependent and angular observables, exploring different binnings for their distributions. We show that in regions of phase space where the interference between SM and the effective operator dominates, a SALLY observable leads to optimal limits. In regions where effects of the quadratic term of the effective operator start becoming dominant, such an observable still leads to optimal limits. This work aims to test current multivariate techniques and inform analysis strategies for LHC Run 3 and beyond.

   hep-phJHEP(2024)·23 citations
8. 08*

   The effect of initial nuclear deformation on dielectron photoproduction in hadronic heavy-ion collisions

   Jiaxuan. Luo🇨🇳 · Xinbai. Li🇨🇳 · Zebo. Tang🇨🇳 · Xin. Wu🇨🇳 · Wangmei. Zha🇨🇳

   Significant excesses of $e^{+}{e}^{-}$ pair production at very low transverse momentum ($p_T<$ 0.15 GeV/c) were observed by the STAR collaboration in hadronic heavy-ion collisions. Such enhancement is assumed to be a sign of photon-photon production in heavy-ion collisions with hadronic overlap, based on comparisons with model calculations for spherical Au + Au collisions. However, there is a lack of calculations for $e^{+}{e}^{-}$ pair production from coherent photon-photon interactions in hadronic U + U collisions, due to the deformity of Uranium nuclei. In this article, we present calculations for $e^{+}{e}^{-}$ pair photoproduction at $\sqrt{s_{NN}}$ = 193 GeV in both spherical and deformed U + U collisions within STAR detector acceptance using the equivalent photon approximation (EPA). We conduct event-by-event analysis to investigate the effects of initial nuclear deformation on pair production. Our numerical results show good agreement with experimental data for the 40%--60% and 60%--80% centrality classes in U + U collisions, and the differences between spherical and deformed configurations are approximately 3\%. We also calculate the yields of the photoproduced $e^{+}{e}^{-}$ pair in hadronic deformed Ru + Ru and Zr + Zr collisions at $\sqrt{s_{NN}}$ = 200 GeV. The results reveal that the ratios of the yields of Ru to Zr exhibit very small differences ($<$ 1%) between spherical and deformed cases.

   hep-phnucl-thPRC(2023)·12 citations
9. 09*

   Inelastic and elastic parton scatterings in the strongly interacting quark-gluon plasma

   Ilia Grishmanovskii🇩🇪 · Olga Soloveva🇩🇪 · Taesoo Song🇩🇪 · Carsten Greiner🇩🇪 · Elena Bratkovskaya🇩🇪

   We investigate the role of inelastic processes in the strongly interacting quark-gluon plasma (sQGP) based on the effective dynamical quasi-particle model (DQPM). In the DQPM the non-perturbative properties of the sQGP at finite temperature $T$ and baryon chemical potential ${\mu }_B$ are described in terms of strongly interacting off-shell partons (quarks and gluons) with dynamically generated spectral functions whose properties are adjusted to reproduce the lQCD EoS for the QGP in thermodynamic equilibrium. For the first time the massive gluon radiation processes from the off-shell quark-quark ($q+q$) and quark-gluon ($q+g$) scatterings are calculated explicitly within leading order Feynman diagrams with effective propagators and vertices from the DQPM without any further approximations. We present the results for the energy and temperature dependencies of the total and differential radiative cross sections and compare them to the corresponding elastic cross sections. We show that our results reproduce the pQCD calculations in the limit of zero masses and widths of quasiparticles. Also we study the ${\mu }_B$ dependence of the inelastic cross sections. Moreover, we present estimates for the transition rate and relaxation time of radiative versus elastic scatterings in the sQGP.

   hep-phnucl-thPRC(2024)·13 citations
10. 10*

    Semileptonic $B_c$ meson decays to S-wave charmonia and $X(3872)$ within the covariant light-front approach

    Zhi-Jie Sun🇨🇳 · Si-Yang Wang🇨🇳 · Zhi-Qing Zhang🇨🇳 · You-Ya Yang🇨🇳 · Zi-Yu Zhang🇨🇳

    In this work, we investigate the semileptonic decays of $B_c$ meson to ${\eta }_c(1S,2S,3S)$, $\psi (1S,2S,3S)$ and $X(3872)$ within the framework of covariant light-front quark model (CLFQM). We combine the helicity amplitudes via the corresponding form factors to obtain the branching ratios of the semileptonic decays $B_c\to {\eta }_c(1S,2S,3S)\ell {\nu }_{\ell }$, $B_c\to \psi (1S,2S,3S))\ell {\nu }_{\ell }$ and $B_c\to X(3872)\ell {\nu }_{\ell }$ with $\ell =e,\mu ,\tau$. In view of the $R_{J/\Psi }$ anomaly released by the LHCb collaboration, it is necessary to calculate the ratios $R_X$ with $X=\psi (1S,2S,3S),{\eta }_c(1S,2S,3S),X(3872)$ systematically, which are helpful to check the lepton flavor universality (LFU). Furthermore, we also take into account another two physical observables, one is the longitudinal polarization fraction $f_L$ and the other is the forward-backward asymmetry $A_{FB}$, which can provide new clues to understand the $R_{J/\Psi }$ anomaly. Such theoretical predictions are necessary and interesting, which can be tested in the future LHCb experiments.

    hep-phhep-exEPJC(2023)·9 citations
11. 11*

    Bottom-charmed baryons in a nonrelativistic quark model

    Qing-Fu Song🇨🇳 · Qi-Fang Lü🇨🇳 · Atsushi Hosaka🇯🇵

    In this work, we study the low-lying mass spectra for bottom-charmed baryons in a nonrelativistic quark model by solving the three-body Schrödinger equation. The lowest ${\Xi }_{bc}$, ${\Xi }_{bc}^{\prime }$, ${\Omega }_{bc}$, and ${\Omega }_{bc}^{\prime }$ states are predicted to be about 6979, 6953, 7109, and 7092 MeV, respectively. Also, the strong decays for the low-lying excited states are investigated. Our results indicate that some of $\lambda -$mode $P-$wave bottom-charmed baryons are relatively narrow, which can be searched for in future experiments. For the low-lying $\rho -$mode and $\rho -\lambda$ hybrid states, their strong decays are highly suppressed and they can survive as extremely narrow states. Moreover, the mass spectra and strong decays for bottom-charmed baryons preserve the heavy quark symmetry well. We hope our calculations can provide helpful information for further experimental and theoretical researches.

    hep-phhep-exnucl-thEPJC(2024)·7 citations
12. 12*

    Interpretation of near-threshold peaks using the method of independent S-matrix poles

    Leonarc Michelle Santos🇵🇭 · Denny Lane B. Sombillo🇵🇭

    We propose a model-independent analysis of near-threshold enhancements using independent S-matrix poles. In this formulation, we constructed a Jost function with controllable zeros to ensure that no poles are generated on the physical Riemann sheet. We show that there is a possibility of misinterpreting the observed near-threshold signals if one utilized a limited parametrization and restrict the analysis to only one element of the S-matrix. Specifically, there is a possibility of the emergence of ambiguous pair of poles which are singularities of the full S-matrix but may not manifest in one of its elements. For a more concrete discussion, we focused on an effective two-channel scattering where the full S-matrix is a $2\times 2$ matrix. We apply our method to the coupled two-channel analysis of the $P_{\psi }^N(4312{)}^{+}$ and found that the compact pentaquark interpretation cannot be ruled out yet.

    hep-phnucl-thPRC(2023)·11 citations
13. 13*

    Cumulative activity of inelastic events under hadron collisions

    S.M. Troshin🇷🇺 · N.E. Tyurin🇷🇺

    We introduce the notion of cumulative activity for inelastic events generated under hadron collisions, discuss its energy dependence and connection with the reflective scattering mode. These issues are relevant for enlightening the asymptotic dynamics in view of the LHC measurements.

    hep-phhep-exInt.J.Mod.Phys.A(2023)·1 citation
14. 14*

    Probing the high-energy dynamics of QCD: selected theoretical and phenomenological studies

    Michael Fucilla🇮🇹

    The center-of-mass energies available at modern accelerators, such as the Large Hadron Collider (LHC), and at forthcoming generation accelerators, such as the Electron-Ion Collider (EIC), offer us a unique opportunity to investigate hadronic matter under the most extreme conditions ever reached. In particular, we can access the Regge-Gribov regime of QCD, described by the Balitsky-Fadin-Kuraev-Lipatov (BFKL) approach along with its non-linear generalizations (the set of B-JIMWLK equations). The aim of these approaches is to resum large-energy logarithmic corrections which spoil the convergence of perturbative series at high-energy. The aforementioned approaches are theoretically developed both in the leading (LL) and the next-to-leading (NLL) approximation, but precise full NLL predictions still remains an open challenge. Furthermore, extending BFKL beyond the NLL approximation has been an open problem for more than twenty years. We face the task of hunting precision in this field from different perspectives. In particular, within the BFKL approach, we calculate the next-to-leading order (NLO) impact factor for the Higgs boson production. This is the necessary ingredient to study the inclusive forward emissions of a Higgs boson in association with a backward identified jet. Moreover, by using already known NLO impact factors, we propose a series of new semi-hard reactions that can be used to investigate BFKL dynamics at the LHC within NLL accuracy. We consider also the problem of extending BFKL beyond the NLL approximation and compute one of the ingredients entering the BFKL kernel at the next-to-NLL (NNLL) accuracy. Finally, in the saturation (non-linear) framework, we calculate the diffractive double hadron photo- or electroproduction cross sections with full NLL accuracy, useful to detect saturation effects, at both the future EIC or already at LHC (via Ultra Peripheral Collisions).

    hep-ph5 citations
15. 15*

    Dalitz decays $D_{sJ}^{(\ast )}\to D_s^{(\ast )}{\ell }^{+}{\ell }^{-}$

    Pietro Colangelo🇮🇹 · Fulvia De Fazio🇮🇹 · Francesco Loparco🇮🇹 · Nicola Losacco🇮🇹

    The Dalitz decays of the positive parity $D_{sJ}^{(\ast )}$ charmed mesons, $D_{sJ}^{(\ast )}\to D_s^{(\ast )}{\ell }^{+}{\ell }^{-}$ with $J=0,1,2$ and $\ell =e,\mu$, are important processes to investigate the nature of the $D_{sJ}^{(\ast )}$ states. We analyze the full set of decays, considering the four lightest $D_{sJ}^{(\ast )}$ mesons as belonging to the heavy quark spin doublets $s_{\ell }^P={\frac{1}{2}}^{+}$ and ${\frac{3}{2}}^{+}$, with $s_{\ell }^P$ the spin-parity of the light degrees of freedom in mesons. The description implies relations among the observables in various modes. We study the decay distributions in the dilepton invariant mass squared and the distributions in the angle between the charged lepton momentum and the momentum of the produced meson, which are expressed in terms of universal form factors and of effective strong couplings. Such measurements are feasible at the present facilities.

    hep-phhep-exPRD(2023)·3 citations
16. 16*

    Investigation of spin-dependent dark matter in mono-photon production at high-energy colliders

    G. Gil da Silveira🇧🇷 · M. S. Mateus Jr🇧🇷

    Many theories about dark matter have emerged due to its strong theoretical appeal in explaining astrophysical phenomena. However, experimental and theoretical particle physics have yet not provided evidence that dark matter is part of the observable Universe. Our work aims to investigate the interaction between Standard Model (SM) fermions and different species of dark matter (DM) particles in high-energy collisions through interaction of a new massive vector mediator, Z'. The production of scalar and fermion DM pairs via fermion annihilation into the new vector boson is investigated near a resonance, where a SM signal from hard photon emission is considered as initial state radiation, namely a mono-photon production. Values of coupling constants between the DM and the SM particles are mapped in contrast to the Planck satellite data for thermal relic density DM computed in the correct framework for the relic density near a resonance, where a weaker suppression of the relic density is expected. We show for the CLIC and LHC kinematic regimes that certain mass ranges and coupling constants of these DM particles are in agreement with the expected relic density near a resonance and are not excluded by collider and astrophysical limits.

    hep-phhep-exEPJC(2024)·6 citations
17. 17*

    Sensitivity of octant of ${\theta }_{23}$, CP violation and mass hierarchy in NO$\nu$A with multinucleon and detector effects

    Paramita Deka🇮🇳 · Kalpana Bora🇮🇳

    In this work, we investigate how multinucleon enhancement and RPA (Random Phase Approximation) suppression can affect the measurement of three unknown neutrino oscillation parameters - the CP-violating phase ${\delta }_{CP}$, the octant of the atmospheric mixing angle ${\theta }_{23}$, and the determination of the mass hierarchy, in the appearance channel of the NO$\nu$A experiment. We include the presence of the detector effect as well in the analysis, which is crucial for capturing realistic experimental scenarios. We also conducted a comparison between the nuclear model Effective Spectral Function (calculated within the RFG model) with and without Transverse Enhancement in terms of sensitivity analysis. It is found that the analysis using our comprehensive model QE(+RPA)+2p2h along with Effective Spectral Function+Transverse Enhancement exhibits significantly enhanced sensitivity compared to the pure QE interaction process, in all the cases.Also, the higher octant of ${\theta }_{23}$, the lower half plane of ${\delta }_{CP}$, and the normal mass hierarchy (HO-LHP-NH) exhibit improved sensitivity, enabling a more precise determination of the corresponding parameters. Furthermore, it is also noted that improving the performance of the detector also improves the results. Thus, including multinucleon effects and improving detector efficiency have the potential to enhance the capabilities of the NO$\nu$A (and other long baseline) experiment in conducting precise parameter studies.

    hep-phJHEP(2024)·3 citations
18. 18*

    Quantum Gravity Effects on Dark Matter and Gravitational Waves

    Stephen F. King🇬🇧 · Rishav Roshan🇬🇧 · Xin Wang🇬🇧 · Graham White🇬🇧 · Masahito Yamazaki🇯🇵

    We explore how quantum gravity effects, manifested through the breaking of discrete symmetry responsible for both Dark Matter and Domain Walls, can have observational effects through CMB observations and gravitational waves. To illustrate the idea we consider a simple model with two scalar fields and two ${\mathcal{Z}}_2$ symmetries, one being responsible for Dark Matter stability, and the other spontaneously broken and responsible for Domain Walls, where both symmetries are assumed to be explicitly broken by quantum gravity effects. We show the recent gravitational wave spectrum observed by several pulsar timing array projects can help constrain such effects.

    hep-phastro-ph.HEhep-thPRD(2024)·31 citations
19. 19*

    Solar neutrinos and ${\nu }_2$ visible decays to ${\nu }_1$

    André de Gouvêa🇺🇸 · Jean Weill🇺🇸 · Manibrata Sen🇩🇪

    Experimental bounds on the neutrino lifetime depend on the nature of the neutrinos and the details of the potentially new physics responsible for neutrino decay. In the case where the decays involve active neutrinos in the final state, the neutrino masses also qualitatively impact how these manifest themselves experimentally. In order to further understand the impact of nonzero neutrino masses, we explore how observations of solar neutrinos constrain a very simple toy model. We assume that neutrinos are Dirac fermions and there is a new massless scalar that couples to neutrinos such that a heavy neutrino - ${\nu }_2$ with mass $m_2$ - can decay into a lighter neutrino - ${\nu }_1$ with mass $m_1$ - and a massless scalar. We find that the constraints on the new physics coupling depend, sometimes significantly, on the ratio of the daughter-to-parent neutrino masses, and that, for large enough values of the new physics coupling, the "dark side" of the solar neutrino parameter space - ${\sin }^2{\theta }_{12}\sim 0.7$ - provides a reasonable fit to solar neutrino data. Our results generalize to other neutrino-decay scenarios, including those that mediate ${\nu }_2\to {\nu }_1{\bar{\nu }}_3{\nu }_3$ when the neutrino mass ordering is inverted mass and $m_2>m_1\gg m_3$, the mass of ${\nu }_3$.

    hep-phastro-ph.SRPRD(2024)·6 citations
20. 20*

    Causal and stable first-order chiral hydrodynamics

    Nick Abboud🇺🇸 · Enrico Speranza🇺🇸 · Jorge Noronha🇺🇸

    We derive the set of inequalities that is necessary and sufficient for nonlinear causality and linear stability of first-order relativistic hydrodynamics with either a $U(1{)}_V$ conserved current or a $U(1{)}_A$ current with a chiral anomaly or both. Our results apply to generic hydrodynamic frames in which no relations among the transport parameters are imposed. Furthermore, our analysis yields, to the best of our knowledge, the first theory of viscous chiral hydrodynamics proven to be causal and stable. We find that causality demands the absence of vorticity-induced heat flux, forcing a departure from the thermodynamic frame in the chiral case. The inequalities for causality and stability define a hypervolume in the space of transport parameters, wherein each point corresponds to a consistent formulation. Notably, causality is determined by just three combinations of transport parameters. We present our results in a form amenable to numerical hydrodynamic simulations.

    ↳ hep-thgr-qchep-phnucl-thPRD(2024)·32 citations
21. 21*

    Heavy Flavour Spectroscopy

    Chang-Zheng Yuan🇨🇳

    The discovery of hadronic states beyond the conventional two-quark meson and three-quark baryon picture in the last two decades is one of the most amazing accomplishments in fundamental physics research. We review the experimental progress on the study of the exotic states (also known as the XYZ particles) beyond the conventional quark model. We give a general review and then focus on the lineshape measurement of the X(3872), observation of new decay modes of the Y(4230) and new vector charmoniumlike states Y(4500) and Y(4790), evidence for the neutral isospin partners of the charged charmoniumlike $Z_{cs}$ states, discoveries of the tetraquark state candidates with four different flavours or two-pairs of charm-anticharm quarks and the pentaquark states.

    ↳ hep-exhep-ph0 citations
22. 22*

    Lorentz Invariance Violation Limits from GRB 221009A

    Tsvi Piran🇮🇱 · Dmitry D. Ofengeim🇮🇱

    It has been long conjectured that a signature of Quantum Gravity will be Lorentz Invariance Violation (LIV) that could be observed at energies much lower than the Planck scale. One possible signature of LIV is an energy-dependent speed of photons. This can be tested with a distant transient source of very high-energy photons. We explore time-of-flight limits on LIV derived from LHAASO's observations of tens of thousands of TeV photons from GRB 221009A, the brightest gamma-ray burst of all time. For a linear ($n=1$) dependence of the photon velocity on energy, we find a lower limit on the subluminal (superluminal) LIV scale of $5.9(6.2)mpl$. These are comparable to the stringent limits obtained so far and, as an independent bound obtained from a different redshift, confirm their robustness. For a quadratic model ($n=2$, corresponding to $d=6$ SME operators), the limits, which are currently the best available with the time-of-flight method, are $5.8(4.6)\times 10^{-8}mpl$. Our analysis uses the publicly available LHAASO data, which is only in the $0.2-7$ TeV range. Higher energy data would enable us to improve these limits by a factor of 3 for $n=1$ and by an order of magnitude for $n=2$.

    ↳ astro-ph.HEgr-qchep-phPRD(2024)·29 citations
23. 23*

    Superradiant instabilities of massive bosons around exotic compact objects

    Lihang Zhou🇨🇳 · Richard Brito🇵🇹 · Zhan-Feng Mai🇨🇳 · Lijing Shao🇨🇳

    Superradiantly unstable ultralight particles around a classical rotating black hole (BH) can form an exponentially growing bosonic cloud, which have been shown to provide an astrophysical probe to detect ultralight particles and constrain their mass. However, the classical BH picture has been questioned, and different theoretical alternatives have been proposed. Exotic compact objects (ECOs) are horizonless alternatives to BHs featuring a reflective surface (with a reflectivity $\mathcal{K}$) in place of the event horizon. In this work, we study superradiant instabilities around ECOs, particularly focusing on the influence of the boundary reflection. We calculate the growth rate of superradiant instabilities around ECOs, and show that the result can be related to the BH case by a correction factor $g_{\mathcal{K}}$, for which we find an explicit analytical expression and a clear physical interpretation. Additionally, we consider the time evolution of superradiant instabilities and find that the boundary reflection can either shorten or prolong the growth timescale. As a result, the boundary reflection alters the superradiance exclusion region on the Regge plane, potentially affecting constraints on the mass of ultralight particles. For a mildly reflective surface ($|\mathcal{K}|\lesssim 0.5$), the exclusion region is not substantially changed, while significant effects from the boundary reflection can occur for an extreme reflectivity ($|\mathcal{K}|\gtrsim 0.9$).

    ↳ gr-qcastro-ph.HEhep-phPRD(2023)·12 citations
24. 24*

    Inclusive hadronic decay rate of the $\tau$ lepton from lattice QCD

    Antonio Evangelista🇮🇹 · Roberto Frezzotti🇮🇹 · Giuseppe Gagliardi🇮🇹 · Vittorio Lubicz🇮🇹 · Francesco Sanfilippo🇮🇹 · Silvano Simula🇮🇹 · Nazario Tantalo🇮🇹

    Inclusive hadronic decays of the $\tau$ lepton are very interesting from the phenomenological point of view since they give access to the CKM matrix elements $V_{ud}$ and $V_{us}$. In this paper, for the first time, by employing the HLT method for hadronic smeared spectral densities we compute on the lattice the inclusive decay rate of the processes $\tau \to X_{ud}{\nu }_{\tau }$, where $X_{ud}$ is a generic hadronic state with $\bar{u}d$ flavor quantum numbers. Our computation, which avoids any recourse to OPE and/or perturbative approximations, is carried out in isospin symmetric $N_f=2+1+1$ lattice QCD at physical quark masses, using ensembles produced by the ETMC at three lattice spacings and two volumes. All uncertainties, except for isospin breaking effects, are taken into account and a result with a subpercent error is obtained for $|V_{ud}|$, which is nicely consistent with the current world average. These findings validate our approach and also motivate the inclusion of isospin breaking corrections and its extension to the inclusive decay $\tau \to X_{us}{\nu }_{\tau }$, paving the way towards a high-precision first principles determination of $|V_{us}|$ and $|V_{ud}|$ from inclusive $\tau$ decay.

    ↳ hep-lathep-phPRD(2023)·51 citations
25. 25*

    Probing the QCD phase transition with chiral mixing in dilepton production

    Azumi Sakai🇯🇵 · Masayasu Harada🇯🇵 · Chiho Nonaka🇯🇵 · Chihiro Sasaki🇵🇱 · Kenta Shigaki🇯🇵 · Satoshi Yano🇯🇵

    We perform a systematic study of dilepton emission in a hot QCD medium based on three different scenarios of chiral mixing, each of which yields a characteristic structure in the vector spectral function. The in-medium spectral functions are accommodated into the state-of-the-art hydrodynamic simulations for a relativistic viscous fluid to calculate the dilepton production rate, fully accounting for the space-time evolution of a created fireball in relativistic heavy-ion collisions. We demonstrate that the low-temperature theorem of chiral mixing extrapolated toward a chiral crossover, often used in the literature, leads to critical shortcomings: the inadequacy of width broadening, and a substantial overestimate of the dilepton yield maximized around the invariant mass of $M=1.2$ GeV. The proper prescription offers a milder yet sizable increase in the window of $1.1<M<1.4$ GeV as the direct signature of chiral symmetry restoration.

    ↳ nucl-thhep-phnucl-ex3 citations
26. 26*

    Relativistic model-free prediction for neutrinoless double beta decay at leading order

    Y. L. Yang🇨🇳 · P. W. Zhao🇨🇳

    Starting from a manifestly Lorentz-invariant chiral Lagrangian, we present a model-free prediction for the transition amplitude of the process $nn\to pp{e}^{-}{e}^{-}$ induced by light Majorana neutrinos, which is a key process of the neutrinoless double beta decay ($0\nu \beta \beta$) in heavy nuclei employed in large-scale searches. Contrary to the nonrelativistic case, we show that the transition amplitude can be renormalized at leading order without any uncertain contact operators. The predicted amplitude defines a stringent benchmark for the previous estimation with model-dependent inputs, and greatly reduces the uncertainty of $0\nu \beta \beta$ transition operator in the calculations of nuclear matrix elements. Generalizations of the present framework could also help to address the uncertainties in $0\nu \beta \beta$ decay induced by other mechanisms. In addition, the present work motivates a relativistic {\it ab initio} calculation of $0\nu \beta \beta$ decay in light and medium-mass nuclei.

    ↳ nucl-thhep-lathep-phPLB(2024)·15 citations
27. 27*

    Search for Charged Lepton Flavor Violation in $J/\psi$ decays at BESIII

    Jingshu Li🇨🇳 · Zhengyun You🇨🇳

    The observation of any charged lepton flavor violation (CLFV) process would be a clear signal of new physics beyond the Standard Model. Various decay modes, including lepton ($\mu ,\tau$) decays, pseudoscalar meson ($K,\pi$) decays, vector meson ($\varphi ,J/\psi ,{\rm Y}$) decays, and Higgs decays, have been explored to detect CLFV. Focusing on the search for CLFV at the $\tau$-charm region, the results of the search for $J/\psi \to e\tau /e\mu$ using the 10 billion $J/\psi$ events collected by the BESIII experiment are presented. The upper limits (ULs) at the 90$\%$ confidence level are $\mathcal{B}(J/\psi \to e^{\pm }{\tau }^{\mp })<7.5\times 10^{-8}$ and $\mathcal{B}(J/\psi \to e^{\pm }{\mu }^{\mp })<4.5\times 10^{-9}$, respectively. Improving the previously published limits by two orders of magnitudes, the results are the most stringent CLFV searches in heavy quarkonium system.

    ↳ hep-exhep-ph1 citation
28. 28*

    A cosmic string solution to the radio synchrotron background

    Bryce Cyr🇬🇧 · Jens Chluba🇬🇧 · Sandeep Kumar Acharya🇬🇧

    We investigate the low-frequency spectral emission from a network of superconducting cosmic string loops in hopes of explaining the observed radio synchrotron background. After considering constraints from a variety of astrophysical and cosmological measurements, we identify a best-fit solution with string tension $G\mu \simeq 6.5\times 10^{-12}$ and current $\mathcal{I}\simeq 2.5\times 10^6$ GeV. This model yields a convincing fit to the data and may be testable in the near future by spectral distortion (TMS, BISOU) and 21 cm experiments (HERA, SKA, REACH). We also find that soft photon heating protects us against current constraints from global $21$ cm experiments.

    ↳ astro-ph.COgr-qchep-phPRD(2024)·23 citations
29. 29*

    Testing Parity Symmetry with the Polarized Cosmic Microwave Background

    Oliver H. E. Philcox🇺🇸 · Maresuke Shiraishi🇯🇵

    New physics in the early Universe could lead to parity-violation in the late Universe, sourcing statistics whose sign changes under point reflection. The best constraints on such phenomena have come from the Planck temperature fluctuations; however, this is already cosmic-variance-limited down to relatively small scales, thus only small improvements are expected in the future. Here, we search for signatures of parity-violation in the polarized CMB, using the Planck PR4 $T$- and $E$-mode data. We perform both a simulation-based blind test for any parity-violating signal at $\ell <518$, and a targeted search for primordial $U(1)$ gauge fields (and the amplitudes of a generic collapsed model) at $\ell <2000$. In all cases, we find no evidence for new physics, with the model-independent test finding consistency with the FFP10/NPIPE simulation suite at $(-)0.4\sigma$, and the gauge field test constraining the fractional amplitude of gauge fields during inflation to be below $6\times 10^{-19}$ at $95\%$ confidence level for a fiducial model. The addition of polarization data can significantly improve the constraints, depending on the particular model of primordial physics, and the bounds will tighten significantly with the inclusion of smaller-scale information.

    ↳ astro-ph.COgr-qchep-exhep-ph+1PRD(2024)·37 citations
30. 30*

    Bespoke Dual Resonance

    Clifford Cheung🇺🇸 · Grant N. Remmen🇺🇸

    Dual resonance is one of the great miracles of string theory. At a fundamental level, it implies that the particles exchanged in different channels are subtly equivalent. Furthermore, it is inextricably linked to the property of exceptionally tame high-energy behavior. In this paper, we present explicit, closed-form expressions for a new class of dual resonant amplitudes describing an infinite tower of spins for an arbitrary mass spectrum. In particular, the input of our construction is a user-defined, fully customizable choice of masses. The resulting "bespoke" amplitudes are well behaved in the ultraviolet and analytic except at simple poles whose residues are polynomial in the momentum transfer, in accordance with locality. The absence of branch cuts can be seen using Newton's identities, but can also be made manifest by expressing the amplitudes as a simple dlog integral of the Veneziano amplitude that remaps the linear Regge trajectories of the string to a tunable spectrum. We identify open regions of parameter space that firmly deviate from string theory but nevertheless comport with partial wave unitarity. Last but not least, we generalize our construction to the scattering of any number of particles in terms of a dlog transform of the Koba-Nielsen worldsheet integral formula.

    ↳ hep-thhep-phPRD(2023)·56 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.