Fri·Aug 26, 2022Friday·August 26, 2022

1. 01*

   Constraining new physics in entangled two-qubit systems: top-quark, tau-lepton and photon pairs

   Marco Fabbrichesi🇮🇹 · Roberto Floreanini🇮🇹 · Emidio Gabrielli🇮🇹

   The measurement of quantum entanglement can provide a new and most sensitive probe to physics beyond the Standard Model. We use the concurrence of the top-quark pair spin states produced at colliders to constrain the magnetic dipole term in the coupling between top quark and gluons, that of $\tau$-lepton pairs spin states to bound contact interactions and that of $\tau$-lepton pairs or two-photons spin states from the decay of the Higgs boson in trying to distinguish between CP-even and odd couplings. These four examples show the power of the new approach as well as its limitations. We show that differences in the entanglement in the top-quark and $\tau$-lepton pair production cross sections can provide constraints better than those previously estimated from total cross sections or classical correlations. Instead, the final states in the decays of the Higgs boson remain maximally entangled even in the presence of CP odd couplings and cannot be used to set bounds on new physics. We discuss the violation of Bell inequalities featured in all four processes.

   hep-phhep-exEPJC(2023)·129 citations
2. 02*

   Quantum Gravitational Decoherence in the 3 Neutrino Flavor Scheme

   Dominik Hellmann🇩🇪 · Heinrich Päs🇩🇪 · Erika Rani🇩🇪

   In many theories of quantum gravity quantum fluctuations of spacetime may serve as an environment for decoherence. Here we study quantum-gravitational decoherence of high energy astrophysical neutrinos in the presence of fermionic dark sectors and for a realistic three neutrino scenario. We show how violation of global symmetries expected to arise in quantum gravitational interactions provides a possibility to pin down the number of dark matter fermions in the universe. Furthermore, we predict the expected total neutrino flux and flavor ratios at experiments depending on the flavor composition at the source.

   hep-phastro-ph.HEgr-qchep-thPRD(2022)·10 citations
3. 03*

   Pole Inflation in Supergravity

   C. Pallis🇬🇷

   We show how we can implement within Supergravity chaotic inflation in the presence of a pole of order one or two in the kinetic mixing of the inflaton sector. This pole arises due to the selected logarithmic Kahler potentials K, which parameterize hyperbolic manifolds with scalar curvature related to the coefficient -N of the logarithmic term. The associated superpotential W exhibits the same R charge with the inflaton-accompanying superfield and includes all the allowed terms. The role of the inflaton can be played by a gauge singlet or non-singlet superfield. Models with one logarithmic term in K for the inflaton, require N=2 and some tuning, of the order of 10^-5, between the terms of W and predict a tensor-to-scalar ratio r at the level of 0.001. The tuning can be totally eluded for more structured K's, with N values increasing with r and spectral index close or even equal to its present central observational value.

   hep-phastro-ph.COhep-thPoS(2022)·7 citations
4. 04*

   Constraining Non-Standard Interactions with Coherent Elastic Neutrino-Nucleus Scattering at the European Spallation Source

   Sabya Sachi Chatterjee🇫🇷 · Stéphane Lavignac🇫🇷 · O. G. Miranda🇲🇽 · G. Sanchez Garcia🇲🇽

   The European Spallation Source (ESS), currently under construction in Sweden, will provide an intense pulsed neutrino flux allowing for high-statistics measurements of coherent elastic neutrino-nucleus scattering (CE{\nu}NS) with advanced nuclear recoil detectors. In this paper, we investigate in detail the possibility of constraining non-standard neutrino interactions (NSIs) through such precision CE{\nu}NS measurements at the ESS, considering the different proposed detection technologies, either alone or in combination. We first study the sensitivity to neutral-current NSI parameters that each detector can reach in 3 years of data taking. We then show that operating two detectors simultaneously can significantly improve the expected sensitivity on flavor-diagonal NSI parameters. Combining the results of two detectors turns out to be even more useful when two NSI parameters are assumed to be nonvanishing at a time. In this case, suitably chosen detector combinations can reduce the degeneracies between some pairs of NSI parameters to a small region of the parameter space.

   hep-phPRD(2023)·25 citations
5. 05*

   Is magic texture for Majorana neutrino immanent in Dirac nature?

   Yuta Hyodo🇯🇵 · Teruyuki Kitabayashi🇯🇵

   The magic textures are successful candidates of the correct texture for the Majorana neutrinos. In this study, we show that some types of magic texture for Majorana neutrinos approximately immanent in the flavor mass matrix for Dirac neutrinos. In addition, it turned out that the normal mass ordering of the Dirac neutrino masses is slightly preferable to the inverted mass ordering in the context of the magic textures.

   hep-phCPC(2023)·4 citations
6. 06*

   Observable r, Gravitino Dark Matter, and Non-thermal Leptogenesis in No-Scale Supergravity

   Waqas Ahmed🇨🇳 · Muhammad Moosa🇵🇰 · Shoaib Munir🇷🇼 · Umer Zubair🇺🇸

   We analyse the shifted hybrid inflation in a no-scale SU(5) model with supersymmetry, which naturally circumvents the monopole problem. The no-scale framework is derivable as the effective field theory of the supersymmetric (SUSY) compactifications of string theory, and it yields a flat potential with no anti-de Sitter vacua, resolving the $\eta$ problem. The model predicts a scalar spectral tilt $n_s$ compatible with the most recent measurements by the Planck satellite, while also accommodating observable values of the tensor-to-scalar ratio $r$ ($\sim 0.0015$), potentially measurable by the near-future experiments. Moreover, the proton decay lifetime in the presence of the dimension-5 operators is found to lie above the current limit imposed by the Super-Kamiokande experiment. A realistic scenario of reheating and non-thermal leptogenesis is invoked, wherein the reheating temperature $T_r$ lies in the $\{2\times 10^6\lesssim T_r\lesssim 2\times 10^9\}$ GeV range, and at the same time the gravitino makes a viable dark matter (DM) candidate.

   hep-phgr-qchep-thJHEP(2023)·7 citations
7. 07*

   Is right-handed current contribution to $\bar{B}\to X_{u}l\nu$ decays corrected by non-trivial vacuum in QCD?

   Hiroyuki Umeeda🇹🇼

   We study violation of quark-hadron duality for $\bar{B}\to X_{u}l\nu$ and $D\to X_{d}l\nu$ decays in the presence of the right-handed current operator. For this case, we show that duality violation has some aspects different from the standard model due to the existence of an instanton. In particular, the fermionic zero mode of an intermediate light quark can give a nonvanishing contribution owing to its chirality structure. A duality-violating component that arises from a single instanton is then analytically extracted as a finite-distance singularity, leading to an oscillatory correction to the observable in Minkowski space. Finally, we show that the size of duality violation for the lepton energy distribution in $\bar{B}$ decays can be comparable to the chirally suppressed perturbative contribution although the absolute size depends on the detail of the QCD vacuum.

   hep-phPRD(2022)·3 citations
8. 08*

   Kaon production in high multiplicity events at the LHC

   Yuri N. Lima🇧🇷 · André V. Giannini🇧🇷 · Victor P. Goncalves🇧🇷

   The production of the $K_S^0$ meson in high multiplicity $pp$ collisions at $\sqrt{s}=$ 13 TeV is investigated considering the hybrid formalism and the solution of the running coupling Balitsky - Kovchegov equation. The associated cross section is estimated and compared with the experimental data for the transverse momentum spectrum. Moreover, we analyze the self-normalized yields of $K_S^0$ mesons as a function of the multiplicity of coproduced charged hadrons and demonstrate that a steep increasing is theoretically predicted. A comparison with the ALICE data is presented considering two distinct solutions of the BK equation.

   hep-phhep-exPRC(2022)·4 citations
9. 09*

   Possible charmed-strange molecular dibaryons

   Shu-Yi Kong🇨🇳 · Jun-Tao Zhu🇨🇳 · Jun He🇨🇳

   In this work, we systematically investigate the dibaryons with charm number $C$=1 and strangeness number $S$=$\pm$ 1 from the interactions of a charmed baryon and a strange baryon ${\Lambda }_c\Lambda$, ${\Lambda }_c{\Sigma }^{(\ast )}$, ${\Sigma }_c^{(\ast )}\Lambda$, and ${\Sigma }_c^{(\ast )}{\Sigma }^{(\ast )}$, and corresponding interactions of a charmed baryon and an antistrange baryon ${\Lambda }_c\bar{\Lambda }$, ${\Lambda }_c{\bar{\Sigma }}^{(\ast )}$, ${\Sigma }_c^{(\ast )}\bar{\Lambda }$, and ${\Sigma }_c^{(\ast )}{\bar{\Sigma }}^{(\ast )}$. With the help of the effective Lagrangians with $SU(3)$, heavy quark, and chiral symmetries, the potentials of the interactions considered are constructed by light meson exchanges. To search for the possible molecules, the quasipotential Bethe-Salpeter equation with the interaction potential kernel is solved to find poles from scattering amplitude. The results suggest that attractions widely exist in charmed-strange system with $C$=1 and $S$=$-1$. The $S$-wave bound states can be produced from most of the channels. Few bound states are also produced from the charmed-antistrange interactions. Couple-channel effect are considered in the current work to discuss the couplings of the molecular states to the channels considered. More experimental research for these charmed-strange dibaryons are suggested.

   hep-phEPJC(2022)·9 citations
10. 10*

    Pole determination of $P_{\psi s}^{\Lambda }(4338)$ and possible $P_{\psi s}^{\Lambda }(4255)$ in $B^{-}\to J/\psi \Lambda \bar{p}$

    S.X. Nakamura (Univ. of Science and Technology of China)🇨🇳 · J.-J. Wu (Univ. of Chinese Academy of Sciences)🇨🇳

    First hidden-charm pentaquark candidate with strangeness, $P_{\psi s}^{\Lambda }(4338)$, was recently discovered in $B^{-}\to J/\psi \Lambda \bar{p}$ by the LHCb Collaboration. $P_{\psi s}^{\Lambda }(4338)$ shows up as a bump at the ${\Xi }_c\bar{D}$ threshold in the $J/\psi \Lambda$ invariant mass ($M_{J/\psi \Lambda }$) distribution. The $M_{J/\psi \Lambda }$ distribution also shows a large fluctuation at the ${\Lambda }_c{\bar{D}}_s$ threshold, hinting the existence of a possible $P_{\psi s}^{\Lambda }(4255)$. In this work, we determine the $P_{\psi s}^{\Lambda }(4338)$ and $P_{\psi s}^{\Lambda }(4255)$ pole positions for the first time. For this purpose, we fit a $B^{-}\to J/\psi \Lambda \bar{p}$ model to the $M_{J/\psi \Lambda }$, $M_{J/\psi \bar{p}}$, $M_{\Lambda \bar{p}}$, and $\cos {\theta }_{K^{\ast }}$ distributions from the LHCb simultaneously; ${\chi }^2/\mathrm{ndf}\sim 1.21$. Then we extract $P_{\psi s}^{\Lambda }$ poles from a unitary ${\Xi }_c\bar{D}$-${\Lambda }_c{\bar{D}}_s$ coupled-channel scattering amplitude built in the model. In our default fit, the $P_{\psi s}^{\Lambda }(4338)$ pole is found at $(4338.2\pm 1.4)-(1.9\pm 0.5)i$ MeV while the $P_{\psi s}^{\Lambda }(4255)$ pole at $4254.7\pm 0.4$ MeV. The $P_{\psi s}^{\Lambda }(4338)$ and $P_{\psi s}^{\Lambda }(4255)$ are mostly ${\Xi }_c\bar{D}$ bound and ${\Lambda }_c{\bar{D}}_s$ virtual states, respectively. Through our analysis, the data disfavors a hypothesis of $P_{\psi s}^{\Lambda }(4338)$ as merely a kinematical effect. This pole determination, which is important in its own right, sets a primary basis to study the nature of the $P_{\psi s}^{\Lambda }$ states.

    hep-phhep-exnucl-thPRD(2023)·48 citations
11. 11*

    Lowering the scale of fermion triplet leptogenesis with two Higgs doublets

    Drona Vatsyayan🇪🇸 · Srubabati Goswami🇮🇳

    In this paper, we consider the possibility of generating the observed baryon asymmetry of the Universe via leptogenesis in the context of triplet fermion mediated type-III seesaw model of neutrino mass. With a hierarchical spectrum of the additional fermions, the lower bound on the lightest triplet mass is $\sim 10^{10}\mathrm{GeV}$ for successful leptogenesis, a couple of orders higher than that of the type-I case. We investigate the possibility of lowering this bound in the framework of two-Higgs-doublet models. We find that the bounds can be lowered down to $10^7$ GeV for a hierarchical spectrum. If we include the flavor effects, then a further lowering by one order of magnitude is possible. We also discuss if such lowering can be compatible with the naturalness bounds on the triplet mass.

    hep-phPRD(2023)·17 citations
12. 12*

    Neutrino Decoherence from Generalised Uncertainty

    Indra Kumar Banerjee🇮🇳 · Ujjal Kumar Dey🇮🇳

    Quantum gravity models predict a minimal measurable length which gives rise to a modification in the uncertainty principle. One of the simplest manifestations of these generalised uncertainty principles is the linear quadratic generalised uncertainty principle which leads to a modified Heisenberg algebra. This can alter the usual von-Neumann evolution of density matrix to a Lindblad-type equation. We show how this can give rise to a decoherence in neutrino propagation in vacuum. The decoherence effects due to the linear quadratic generalised uncertainty principle are extremely minimal and is unlikely to be detectable in the existing or upcoming experimental facilities for any of the natural sources of neutrinos. We also show that, in principle, there can be other variants of generalised uncertainty principle which predicts verifiable decoherence effects for the cosmic neutrino background.

    hep-phgr-qcEPJC(2023)·10 citations
13. 13*

    W-boson angular coefficients at LHC at high precision

    Timea Vitos🇸🇪

    We present state-of-the-art high-precision theory predictions for the dominant angular coefficients parametrizing the spin-correlations in the production and decay of a W-boson produced at transverse momentum larger than 30 GeV. The computation at NNLO QCD and NLO EW accuracy are combined to obtain differential distributions in the W-boson transverse momentum and rapidity. The found results show up to 10 % corrections in certain regions of phase space, while the scale bands are significantly reduced as compared to NLO QCD.

    hep-phhep-exPoS(2023)·0 citations
14. 14*

    On the prompt contribution to the atmospheric neutrino flux

    Sergey Ostapchenko🇩🇪 · Maria Vittoria Garzelli🇩🇪 · Günter Sigl🇩🇪

    The prompt contribution to the atmospheric neutrino flux is analyzed. It is demonstrated that the corresponding theoretical uncertainties related to perturbative treatment of charm production, notably, the ones stemming from the low and high $x$ behavior of parton distribution functions, can be conveniently studied at the level of charm quark production. Additionally, we discuss the non-perturbative contribution to the prompt neutrino flux, related to the intrinsic charm content of the proton, and analyze its main features.

    hep-phPRD(2023)·12 citations
15. 15*

    Precise predictions and new insights for atomic ionisation from the Migdal effect

    Peter Cox🇦🇺 · Matthew J. Dolan🇦🇺 · Christopher McCabe🇬🇧 · Harry M. Quiney🇦🇺

    The scattering of neutral particles by an atomic nucleus can lead to electronic ionisation and excitation through a process known as the Migdal effect. We revisit and improve upon previous calculations of the Migdal effect, using the Dirac-Hartree-Fock method to calculate the atomic wavefunctions. Our methods do not rely on the use of the dipole approximation, allowing us to present robust results for higher nuclear recoil velocities than was previously possible. Our calculations provide the theoretical foundations for future measurements of the Migdal effect using neutron sources, and searches for dark matter in direct detection experiments. We show that multiple ionisation must be taken into account in experiments with fast neutrons, and derive the semi-inclusive probability for processes that yield a hard electron above a defined energy threshold. We present results for the noble elements up to and including xenon, as well as carbon, fluorine, silicon and germanium. The transition probabilities from our calculations are publicly available.

    hep-phhep-exphysics.atom-phPRD(2023)·43 citations
16. 16*

    Asymmetric Dark Matter Abundance Including Non-thermal production

    Maqingshan🇨🇳 · Hoernisa Iminniyaz🇨🇳

    We investigate the relic abundance of asymmetric Dark Matter where the asymmetric Dark Matter is non--thermally produced from the decay of heavier particles in addition to the usual thermal production. We discuss the relic density of asymmetric Dark Matter including the decay of heavy particles in low temperature scenario. Here we still assume the universe is radiation dominated and there is asymmetry before the decay of heavy particles. We obtained increased abundances of asymmetric Dark Matter when there is additional contribution from the decay of heavier particles. Finally we find the constraints on the asymmetry factor and annihilation cross section using the Planck data.

    hep-phCommun.Theor.Phys.(2023)·0 citations
17. 17*

    Asymmetric particle-antiparticle Dirac equation: second quantization

    Gustavo Rigolin🇧🇷

    We build the fully relativistic quantum field theory related to the asymmetric Dirac fields. These fields are solutions of the asymmetric Dirac equation, a Lorentz covariant Dirac-like equation whose positive and "negative" frequency plane wave solutions' dispersion relations are no longer degenerate. At the second quantization level, we show that this implies that particles and antiparticles sharing the same wave number have different energies and momenta. In spite of that, we prove that by properly fixing the values of the relativistic invariants that define the asymmetric Dirac free field Lagrangian density, we can build a consistent, fully relativistic, and renormalizable quantum electrodynamics (QED) that is empirically equivalent to the standard QED. We discuss the reasons and implications of this non-trivial equivalence, exploring qualitatively other scenarios in which the asymmetric Dirac fields may lead to beyond the standard model predictions. We conjecture that this non-degeneracy in the energies for particles and antiparticles may lead to a fully relativistic understanding of the asymmetry between matter and antimatter in the present day universe as well as to an alternative way of modeling the gravitational interaction between a particle and an antiparticle. We give a complete account of how the asymmetric Dirac fields and the corresponding annihilation and creation operators transform under improper Lorentz transformations (parity and time reversal operations) and under the charge conjugation operation. We also prove that the present theory respects the CPT theorem.

    hep-phhep-thquant-phJ.Phys.G(2023)·2 citations
18. 18*

    Consistency and Interpretation of the LHC (Di-)Di-Jet Excesses

    Andreas Crivellin🇨🇭 · Claudio Andrea Manzari🇨🇭 · Bruce Mellado🇿🇦 · Salah-Eddine Dahbi🇿🇦

    ATLAS observed a limit for {the cross section of di-jets resonances, which is weaker than expected for a} mass slightly below $\approx$1\TeV. In addition, CMS reported hints for the (non-resonant) pair production of di-jet resonances $X$ via a particle $Y$ at a very similar mass range with a local (global) significance of 3.6\,$\sigma$ (2.5\,$\sigma$) at $m_X\approx 950$GeV. In this article we show that using the preferred range for $m_X$ from the ATLAS analysis, one can reinterpret the CMS analysis of di-di-jets in terms of a resonant search with $Y\to XX$, with a significantly reduced look-elsewhere effect, finding an excess for $m_Y\approx 3.6$\TeV with a significance of $4.0\sigma$ ($3.2\sigma$) locally (globally). We present two possible UV completions capable of explaining the (di-)di-jet excesses, one containing two scalar di-quarks, the other one involving heavy gluons based on an $SU(3{)}_1\times SU(3{)}_2\times SU(3{)}_3$ gauge symmetry, spontaneously broken to $SU(3)$ color. In the latter case, non-perturbative couplings are required, pointing towards a composite or extra-dimensional framework. In fact, using 5D-AdS space-time, one obtains the correct mass ratio for $m_X/m_Y$, assuming the $X$ is the lowest lying resonance, and predicts a third (di-)di-jet resonance with a mass around $\approx 2.2$\TeV.

    hep-phhep-exPRD(2023)·17 citations
19. 19*

    On Continuum Effective Field Theories, Gravity and Holography

    Sylvain Fichet🇧🇷 · Eugenio Megias🇪🇸 · Mariano Quiros🇪🇸

    We examine effective field theories (EFTs) with a continuum sector in the presence of gravity. We first explain, via arguments based on central charge and species scale, that an EFT with a free continuum cannot consistently couple to standard (i.e. 4D Einstein) gravity. It follows that EFTs with a free or nearly-free continuum must either have a finite number of degrees of freedom or nonstandard gravity. The latter claim is realized for holographically-defined continuum models. We demonstrate this by computing the deviations from standard gravity in a specific 5D scalar-gravity system that gives rise to a gapped continuum (i.e the linear dilaton background). We find an $R^{-2}$ deviation from the Newtonian potential. At finite temperature we find an energy density with matter-like behavior in the brane Friedmann equation, holographically induced from the bulk geometry. Thus, remarkably, a brane-world living in the linear dilaton background automatically contains dark matter. We also present a slightly more evolved asymptotically-AdS linear dilaton model, for which the deviations exhibit a transition between AdS and linear dilaton behaviors.

    hep-phastro-ph.COhep-thPRD(2023)·29 citations
20. 20*

    Current and future gamma-ray searches for dark-matter annihilation beyond the unitarity limit

    Donggeun Tak🇩🇪 · Matthew Baumgart🇺🇸 · Nicholas L. Rodd🇨🇭 · Elisa Pueschel🇩🇪

    For decades, searches for electroweak-scale dark matter (DM) have been performed without a definitive detection. This lack of success may hint that DM searches have focused on the wrong mass range. A proposed candidate beyond the canonical parameter space is ultra-heavy DM (UHDM). In this work, we consider indirect UHDM annihilation searches for masses between 30 TeV and 30 PeV, extending well beyond the unitarity limit at $\sim$100 TeV, and discuss the basic requirements for DM models in this regime. We explore the feasibility of detecting the annihilation signature, and the expected reach for UHDM with current and future Very-High-Energy (VHE; $>$ 100 GeV) $\gamma$-ray observatories. Specifically, we focus on three reference instruments: two Imaging Atmospheric Cherenkov Telescope arrays, modeled on VERITAS and CTA-North, and one Extended Air Shower array, motivated by HAWC. With reasonable assumptions on the instrument response functions and background rate, we find a set of UHDM parameters (mass and cross section) for which a $\gamma$-ray signature can be detected by the aforementioned observatories. We further compute the expected upper limits for each experiment. With realistic exposure times, the three instruments can probe DM across a wide mass range. At the lower end, it can still have a point-like cross section, while at higher masses the DM could have a geometric cross section, indicative of compositeness.

    ↳ astro-ph.HEastro-ph.COhep-exhep-phApJL(2022)·20 citations
21. 21*

    Midrapidity cluster formation in heavy-ion collisions

    Elena Bratkovskaya🇩🇪 · Susanne Glässel🇩🇪 · Viktar Kireyeu🇷🇺 · Jörg Aichelin🇫🇷 · Marcus Bleicher🇩🇪 · Christoph Blume🇩🇪 · Gabriele Coci🇩🇪 · Vadim Kolesnikov🇷🇺 · Jan Steinheimer🇩🇪 · Vadim Voronyuk🇷🇺

    We study the production of clusters and hypernuclei at midrapidity employing the Parton-Hadron-Quantum-Molecular-Dynamics (PHQMD) approach, a microscopic n-body transport model based on the QMD propagation of the baryonic degrees of freedom with density dependent 2-body potential interactions. In PHQMD the cluster formation occurs dynamically, caused by the interactions. The clusters are recognized by the Minimum Spanning Tree (MST) algorithm. We present the PHQMD results for cluster and hypernuclei formation in comparison with the available experimental data at relativistic energies. PHQMD allows to study the time evolution of formed clusters and the origin of their production, which helps to understand how such weakly bound objects are formed and survive in the rather dense and hot environment created in heavy-ion collisions. It offers therefore an explanation of the 'ice in the fire' puzzle. To investigate whether this explanation of the 'ice in the fire' puzzle applies only to the MST results we study also the deuterons production by coalescence. We embed MST and coalescence in the PHQMD and UrQMD transport approaches in order to obtain model independent results. We find that both clustering procedures give very similar results for the deuteron observables in the UrQMD as well as in the PHQMD environment. This confirms that our solution for the 'ice in the fire' puzzle is common to MST and coalescence and independent of the transport approach.

    ↳ nucl-thhep-exhep-phEPJ Web Conf.(2023)·12 citations
22. 22*

    Sensitivity of Au+Au collisions to the symmetric nuclear matter equation of state at 2 -- 5 nuclear saturation densities

    Dmytro Oliinychenko🇺🇸 · Agnieszka Sorensen🇺🇸 · Volker Koch🇺🇸 · Larry McLerran🇺🇸

    We demonstrate that proton and pion flow measurements in heavy-ion collisions at incident energies ranging from 1 to 20 GeV per nucleon in the fixed target frame can be used for an accurate determination of the symmetric nuclear matter equation of state at baryon densities equal 2--4 times nuclear saturation density $n_0$. We simulate Au+Au collisions at these energies using a hadronic transport model with an adjustable vector mean-field potential dependent on baryon density $n_B$. We show that the mean field can be parametrized to reproduce a given density-dependence of the speed of sound at zero temperature $c_s^2(n_B,T=0)$, which we vary independently in multiple density intervals to probe the differential sensitivity of heavy-ion observables to the equation of state at these specific densities. Recent flow data from the STAR experiment at the center-of-mass energies $\sqrt{s_{NN}}=\{3.0,4.5\}$ GeV can be described by our model, and a Bayesian analysis of these data indicates a hard equation of state at $n_B\in (2,3)n_0$ and a possible phase transition at $n_B\in (3,4)n_0$. More data at $\sqrt{s_{NN}}=2-5$ GeV, as well as a more thorough analysis of the model systematic uncertainties will be necessary for a more precise conclusion.

    ↳ nucl-thhep-phPRC(2023)·81 citations
23. 23*

    The high-density equation of state in heavy-ion collisions: Constraints from proton flow

    Jan Steinheimer🇩🇪 · Anton Motornenko🇩🇪 · Agnieszka Sorensen🇺🇸 · Yasushi Nara🇯🇵 · Volker Koch🇺🇸 · Marcus Bleicher🇩🇪

    A set of different equations of state is implemented in the molecular dynamics part of a non-equilibrium transport simulation (UrQMD) of heavy-ion collisions. It is shown how different flow observables are affected by the density dependence of the equation of state. In particular, the effects of a phase transition at high density are explored, including an expected reduction in mean $m_T$. We also show that an increase in $v_2$ is characteristic for a strong softening of the equation of state. The phase transitions with a low coexistence density, $n_{\mathrm{CE}}<4n_0$, show a distinct minimum in the slope of the directed flow as a function of the beam energy, which would be a clear experimental signal. By comparing our results with experimental data, we can exclude any strong phase transition at densities below $4n_0$.

    ↳ nucl-thhep-phEPJC(2022)·56 citations
24. 24*

    Gradient corrections to the quantum effective action

    Sofia Canevarolo🇳🇱 · Tomislav Prokopec🇳🇱

    We derive the quantum effective action up to second order in gradients and up to two-loop order for an interacting scalar field theory. This expansion of the effective action is useful to study problems in cosmological settings where spatial or time gradients are important, such as bubble nucleation in first-order phase transitions. Assuming spacetime dependent background fields, we work in Wigner space and perform a midpoint gradient expansion, which is consistent with the equations of motion satisfied by the propagator. In particular, we consider the fact that the propagator is non-trivially constrained by an additional equation of motion, obtained from symmetry requirements. At one-loop order, we show the calculations for the case of a single scalar field and then generalise the result to the multi-field case. While we find a vanishing result in the single field case, the one-loop second-order gradient corrections can be significant when considering multiple fields. As an example, we apply our result to a simple toy model of two scalar fields with canonical kinetic terms and mass mixing at tree-level. Finally, we calculate the two-loop one-particle irreducible (1PI) effective action in the single scalar field case, and obtain a nonrenormalisable result. The theory is rendered renormalisable by adding two-particle irreducible (2PI) counterterms, making the 2PI formalism the right framework for renormalization when resummed 1PI two-point functions are used in perturbation theory.

    ↳ hep-thastro-ph.COhep-phJHEP(2024)·2 citations
25. 25*

    Multiplicity fluctuations and correlations in 5.02 TeV p+Pb collisions at zero impact parameter

    Mathis Pepin🇫🇷 · Peter Christiansen🇸🇪 · Stéphane Munier🇫🇷 · Jean-Yves Ollitrault🇫🇷

    We present a Bayesian method to reconstruct event-by-event multiplicity fluctuations and rapidity correlations in p+Pb collisions at zero impact parameter from minimum-bias data, without assuming any model of the collision dynamics. We test it on Monte Carlo simulations with the Angantyr model, then apply it to ATLAS data on the distribution of charged multiplicity and transverse energy in p+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV. Fluctuations in $b=0$ collisions are quantum fluctuations which originate mostly from the proton wave function, and therefore have the potential to constrain the subnucleonic structure of the proton. The Angantyr model is found to overestimate fluctuations. In addition, we find that as the rapidity increases (towards the Pb-going side), not only the multiplicity density increases, but also its relative event-by-event fluctuation. This counter-intuitive phenomenon is also observed in simulations with Angantyr, and with the QCD dipole model, where its origin can be traced back to the branching process through which gluons are produced.

    ↳ nucl-thhep-exhep-phnucl-exPRC(2023)·7 citations
26. 26*

    Why do elementary particles have such strange mass ratios? -- The role of quantum gravity at low energies

    Tejinder P. Singh🇮🇳

    When gravity is quantum, the point structure of space-time should be replaced by a non-commutative geometry. This is true even for quantum gravity in the infrared. Using the octonions as space-time coordinates, we construct a pre-spacetime, pre-quantum Lagrangian dynamics. We show that the symmetries of this non-commutative space unify the standard model of particle physics with $SU(2{)}_R$ chiral gravity. The algebra of the octonionic space yields spinor states which can be identified with three generations of quarks and leptons. The geometry of the space implies quantisation of electric charge, and leads to a theoretical derivation of the mysterious mass ratios of quarks and the charged leptons. Quantum gravity is quantisation not only of the gravitational field, but also of the point structure of space-time.

    ↳ physics.gen-phgr-qchep-phhep-thMDPI Physics(2022)·7 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.