Mon·Dec 25, 2023Monday·December 25, 2023

1. 01*

   Heavy flavor transport and observables in heavy-ion collisions within the MARTINI+MUSIC framework

   Manu Kurian🇺🇸 · Mayank Singh🇺🇸 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦

   We study the transport dynamics of charm quarks within an expanding quark-gluon plasma for Pb+Pb collisions at 2.76 TeV. The analysis incorporates the hydrodynamical approach-MUSIC with fluctuating IP-Glasma initial state and Bayesian-quantified viscous coefficients. We study the interaction strength of charm quarks in the medium, including elastic collisional processes with medium constituents, gluon emission processes, and the impact of non-perturbative interactions on heavy quark transport. Further, we analyze the dynamics of heavy flavors using a hybrid framework that incorporates the MARTINI event generator, with PYTHIA8.1 for the initial production of heavy quarks, and Langevin dynamics to describe the evolution of heavy quarks.

   hep-phnucl-th0 citations
2. 02*

   Dynamically generated axial-vector meson resonance in the chiral symmetry restored vacuum

   Jisu Kim🇰🇷 · Su Houng Lee🇰🇷

   We study the modification of the properties of the axial-vector meson, dynamically generated through the unitarization procedure, in the vacuum where the chiral symmetry is restored. This is accomplished by scaling the pion decay constant as the chiral order parameter while keeping the other input parameters fixed. We find that the mass and width of the axial-vector meson reduce to those of the vector meson, as anticipated by the Weinberg sum rules. The findings are consistent with the results of a recent QCD sum rule calculation, wherein the chiral order parameter is expressed through chiral symmetry-breaking four-quark operators, leading to the mass-squared difference scaling in proportion to variations in the chiral order parameter. We calculate the scaling behavior for the mass differences obtained from the unitarization method using both the physical and massless pion masses.

   hep-phnucl-th0 citations
3. 03*

   Phenomenology of light mesons with $J=2,3$

   Shahriyar Jafarzade🇵🇱

   In this thesis, I present the results for light mesons with $J=2,3$ within an effective hadronic model, the so-called extended Linear Sigma Model (eLSM). This model is based on the approximate chiral symmetry of QCD. Qualitative agreement between model results and PDG as well as LQCD data is obtained. Various predictions for the radiative decays can be tested in e.g., GlueX and CLAS12 experiments at Jefferson Lab. After applying the chiral model for well-established spin-2 mesons (with $J^{PC}=2^{++}$), I move on to their chiral partners (the axial-tensor mesons with $J^{PC}=2^{++}$), where the resonances are still missing. Large decay widths are predicted in the chiral model as well as in LQCD simulations.Furthermore, I describe the decays of the spin-2 tensor glueball $G_2(???)$ within the eLSM, which can be helpful in future experimental searches e.g., BESIII and LHCb experiments. Some isoscalar tensor resonances of PDG with a mass of around 2 GeV are studied, and at present, the best tensor glueball candidate turns out to be the broad resonance $f_2(1950)$. In the case of the ground-state spin-3 mesons ($J^{PC}=3^{--}$), our chiral model is limited to the $SU(3)$ flavor symmetry because of the yet unknown chiral partners ($J^{PC}=3^{++}$). The effective model results are in good agreement with the PDG data and LQCD results, and the predictions for the radiative decays can be interesting for photoproduction experiments such as GlueX and CLAS12. Additional estimates for the decay ratios of the $G_3(???)$ tensor glueball with $J^{PC}=3^{--}$ are also presented. The role of the glueball spectrum at non-zero temperature is explored within the Glueball Resonance Gas model below the critical temperature of the pure Yang-Mills sector of the QCD phase diagram. It turns out that the latest glueball spectrum from LQCD can well describe the pressure up to almost the critical temperature.

   hep-ph0 citations
4. 04*

   Les Houches guide to reusable ML models in LHC analyses

   Jack Y. Araz🇺🇸 · Andy Buckley🇬🇧 · Gregor Kasieczka🇩🇪 · Jan Kieseler🇩🇪 · Sabine Kraml🇫🇷 · Anders Kvellestad🇳🇴 · Andre Lessa🇧🇷 · Tomasz Procter🇬🇧 · Are Raklev🇳🇴 · Humberto Reyes-Gonzalez🇮🇹 · Krzysztof Rolbiecki🇵🇱 · Sezen Sekmen🇰🇷 · Gokhan Unel🇺🇸

   With the increasing usage of machine-learning in high-energy physics analyses, the publication of the trained models in a reusable form has become a crucial question for analysis preservation and reuse. The complexity of these models creates practical issues for both reporting them accurately and for ensuring the stability of their behaviours in different environments and over extended timescales. In this note we discuss the current state of affairs, highlighting specific practical issues and focusing on the most promising technical and strategic approaches to ensure trustworthy analysis-preservation. This material originated from discussions in the LHC Reinterpretation Forum and the 2023 PhysTeV workshop at Les Houches.

   hep-phhep-exSciPost Phys.Comm.Rep.(2024)·21 citations
5. 05*

   Hot spots in a proton

   S. Demirci🇫🇮 · T. Lappi🇫🇮 · S. Schlichting🇩🇪

   We explore the consequences of gluonic hot spots inside the proton for the initial eccentricities in a proton-nucleus collision, and the constraints on the parameters describing these hot spots from coherent and incoherent exclusive vector meson production cross sections in deep inelastic scattering. We show that geometric fluctuations of hot spots inside the proton are the dominant source of eccentricity whereas color charge fluctuations only give a negligible correction. We find that the coherent cross section is sensitive to both the size of the target and the structure of the probe. The incoherent cross section is dominated by color fluctuations at small transverse momentum transfer (t), by proton and hot spot sizes as well as the structure of the probe at medium -t and again by color fluctuations at large -t.

   hep-phnucl-thEPJ Web Conf.(2024)·1 citation
6. 06*

   Thermalization and quark production in spatially homogeneous systems of gluons

   Sergio Barrera Cabodevila🇪🇸 · Carlos A. Salgado🇪🇸 · Bin Wu🇪🇸

   We first assemble a full set of the Boltzmann Equation in Diffusion Approximation (BEDA) for studying thermalization/hydrodynamization and quark production in out of equilibrium systems. We then discuss thermalization and the production of three flavors of massless quarks in spatially homogeneous systems initially filled only with gluons. A complete parametric understanding for thermalization and quark production is obtained for both initially very dense or dilute systems, which are complemented by detailed numerical simulations. For initial distributions more relevant for heavy-ion collisions, the complete thermal equilibration is found to be significantly delayed by considering quark production.

   hep-phnucl-thEPJ Web Conf.(2024)·2 citations
7. 07*

   Decay of the Higgs boson to longitudinally polarized leptons and quarks

   R.T. Ovsiannikov🇺🇦 · A.Yu. Korchin🇺🇦

   An important problem in the particle physics is interaction of the Higgs boson with the fermions. It is in the processes, which involve $hff$ interaction, the manifestations of $CP$ violation are possible. This in turn can be helpful in solving the problem of the dominance of matter over antimatter in the Universe. In this connection, in the present paper, the effect of longitudinal polarization of leptons and quarks produced in the decay of the Higgs boson is investigated and calculated. We consider the case in which the Higgs boson interacts with fermions via a mixture of scalar and pseudoscalar couplings. Under this assumption, the longitudinal polarization can acquire non-zero values due to imaginary part of loop corrections to tree-level amplitudes. This polarization is a direct signature of the $CP$ violation in the Higgs sector. Effects of the longitudinal polarization of $\tau$ leptons on the energy distribution of the pions in the two-step Higgs-boson decay $h\to {\tau }^{-}{\tau }^{+}\to {\pi }^{-}{\nu }_{\tau }{\pi }^{+}{\bar{\nu }}_{\tau }$ are also studied, and the energy asymmetry with corresponding moments are calculated.

   hep-phInt.J.Mod.Phys.A(2024)·0 citations
8. 08*

   Prospects to scrutinise or smash SM*A*S*H

   Andreas Ringwald🇩🇪

   SM*A*S*H is an extension of the Standard Model of particle physics which has just the minimal number of fields in order to solve six puzzles of particle physics and cosmology in one smash: vacuum stability, inflation, baryon asymmetry, neutrino masses, strong CP, and dark matter. The parameters of SM*A*S*H are constrained by symmetries and requirements to solve these puzzles. This provides various firm predictions for observables which can be confronted with experiments. We discuss the prospects and timeline to scrutinise or smash SM*A*S*H by cosmic microwave background polarisation experiments, axion haloscopes, and future space-borne gravitational wave detectors.

   hep-phastro-ph.COhep-exPoS(2024)·3 citations
9. 09*

   String fragmentation of a quark pair with entangled spin states: application to $e^{+}{e}^{-}$ annihilation

   A. Kerbizi🇮🇹 · X. Artru🇫🇷

   We present a recursive quantum mechanical model for the fragmentation of a string stretched between a quark and an antiquark with entangled spin states. The quarks are assumed to be produced in the $e^{+}{e}^{-}$ annihilation process via the exchange of a virtual photon and the correlations between their spin states are described by a joint spin density matrix. The string fragmentation process is formulated at the amplitude level by using the splitting matrices of the recent string+${}^3{P}_0$ model of polarized quark fragmentation with pseudoscalar and vector meson emissions, and accounts for the systematic propagation of the spin correlations in the fragmentation chain. The model is formulated as a recursive recipe suitable for a Monte Carlo implementation. It reproduces the expected angular correlation, due to the Collins effect, between back-to-back pseudoscalar and/or vector mesons. For the latter, this correlation also involves the momenta of the decay products. We use the model for studying the sign of the Collins asymmetry for back-to-back vector and pseudoscalar mesons.

   hep-phPRD(2024)·5 citations
10. 10*

    SANC Monte Carlo programs for small-angle Bhabha scattering

    A.B. Arbuzov🇷🇺 · S.G. Bondarenko🇷🇺 · I.R. Boyko🇷🇺 · L.V. Kalinovskaya🇷🇺 · A.A. Kampf🇷🇺 · R.R. Sadykov🇷🇺 · V.L. Yermolchyk🇷🇺

    Luminosity monitoring at $e^{+}{e}^{-}$ colliders is investigated using SANC Monte Carlo event generator ReneSANCe and integrator MCSANC for simulation of Bhabha scattering at low angles. Results are presented for center-of-mass energies of the Z boson resonance and 240 GeV for the conditions of typical luminosity detectors. It is shown that taking into account bremsstrahlung events with extremely low electron scattering angles is relevant to match the precision tags of the future electron-positron colliders.

    hep-phCPC(2024)·0 citations
11. 11*

    Scattering of scalar and tensor glueballs

    Enrico Trotti🇵🇱

    The scalar glueball, the lightest state in the gluonic Yang-Mills (YM) sector of QCD, is stable in that framework. The scattering of two scalar glueballs is therefore a well defined process in YM, which can be studied with the tools of quantum field theory and partial wave analysis. By using a dilaton Lagrangian, which contains a single dimensionful parameter ${\Lambda }_G$, in the context of proper unitarization procedures, we find that a bound state is expected to form in the $S$-wave if ${\Lambda }_G$ is below a certain critical value. Additionally, we also evaluate the impact of a cutoff function on the obtained results and we discuss possible future comparison of our model with Lattice QCD and, eventually, with experimental searches. We show that the expansion into partial wave can also be useful (together with the covariant helicity formalism) in the study of decays of mesons. This method allows us to describe the ratio between two different waves in the same decays. We use this information to describe decay widths and other relevant quantities. Moreover, we show that the results obtained using the covariant helicity formalism do not change when rotating the reference frame centered in the decaying particle. In this way, an alternative calculation scheme is presented. Finally, we use the so-called Glueball Resonance Gas (GRG) model to describe the thermal properties of YM below the critical temperature for deconfinement. The quantities obtained from this model (such as the pressure) can be compared with those obtained from lattice works. The contribution of heavier glueballs and the interaction between scalar and tensor glueballs turns out to be rather small. Within this context, the scattering of two tensor glueballs, required to estimate its contribution in the GRG model, is investigated in detail.

    hep-ph0 citations
12. 12*

    Improving the potential of BDF@SPS to search for new physics with liquid argon time projection chambers

    Martina Ferrillo🇨🇭 · Maksym Ovchynnikov🇩🇪 · Filippo Resnati🇨🇭 · Albert De Roeck🇨🇭

    Beam dump experiments proposed at the SPS are perfectly suited to explore the parameter space of models with long-lived particles, thanks to the combination of a large intensity with a high proton beam energy. In this paper, we study how the exploration power may be augmented further by installing a detector based on liquid argon time projection chamber technology. In particular, we consider several signatures of new physics particles that may be uniquely searched for with such a detector, including double bang events with heavy neutral leptons, inelastic light dark matter, and millicharged particles.

    hep-phphysics.ins-detJHEP(2024)·5 citations
13. 13*

    Probing flavor constrained SMEFT operators through $tc$ production at the Muon collider

    Subhaditya Bhattacharya🇮🇳 · Sahabub Jahedi🇮🇳 · Soumitra Nandi🇮🇳 · Abhik Sarkar🇮🇳

    We investigate flavour violating four Fermi Standard Model Effective Field Theory (SMEFT) operators of dimension-six that can be probed via $tc(\bar{t}c+t\bar{c})$ production at the multi-TeV muon collider. We study different FCNC and FCCC processes related to $B$, $B_s$, $K$ and $D$ decays and mixings, sensitive to these operators and constrain the corresponding couplings. The tensor operator turns out to be most tightly bound. We perform event simulation of the final state signal from $tc$ production together with the SM background to show that operators after flavour constraint can reach the discovery limit at 10 TeV muon collider. We further adopt the optimal observable technique (OOT) to determine the optimal statistical sensitivity of the Wilson coefficients and compare them with the flavour constraints. We use the limits to predict the observational sensitivities of the rare processes like $K_L\to {\pi }_0\ell \ell$, $D_0\to \mu \mu$, $t\to c\ell \ell$.

    hep-phJHEP(2024)·30 citations
14. 14*

    micrOMEGAs 6.0: N-component dark matter

    G. Alguero🇫🇷 · G. Belanger🇫🇷 · F. Boudjema🇫🇷 · S. Chakraborti🇬🇧 · A. Goudelis🇫🇷 · S. Kraml🇫🇷 · A. Mjallal🇫🇷 · A. Pukhov🇷🇺

    micrOMEGAs is a numerical code to compute dark matter (DM) observables in generic extensions of the Standard Model of particle physics. We present a new version of micrOMEGAs that includes a generalization of the Boltzmann equations governing the DM cosmic abundance evolution which can be solved to compute the relic density of N-component DM. The direct and indirect detection rates in such scenarios take into account the relative contribution of each component such that constraints on the combined signal of all DM components can be imposed. The co-scattering mechanism for DM production is also included, whereas the routines used to compute the relic density of feebly interacting particles have been improved in order to take into account the effect of thermal masses of t-channel particles. Finally, the tables for the DM self-annihilation - induced photon spectra have been extended down to DM masses of 110 MeV, and they now include annihilation channels into light mesons.

    hep-phComput.Phys.Commun.(2024)·223 citations
15. 15*

    Zero-bin subtraction and the $q_{\mathrm{T}}$ spectrum beyond leading power

    Giancarlo Ferrera🇮🇹 · Wan-Li Ju🇮🇹 · Marek Schoenherr🇬🇧

    In this paper, we present an algorithm to construct the qT distribution at NLO accuracy to arbitrary power precision, including the assembly of suitable zero-bin subtrahends, in a mathematically well-defined way for a generic choice of rapidity-divergence regularisation prescription. In its derivation, we divide the phase space into two sectors, the interior of the integration domain as well as the integration boundary, which we include here for the first time. To demonstrate the applicability and usefulness of our algorithm, we calculate the NNLP corrections for Higgs hadroproduction for the first time. We observe that our approximate NNLP-accurate qT spectra replicate the asymptotic behaviour of the full QCD calculation to a much better degree than the previously available results, both within the $q_{\mathrm{T}}\to 0$ limit and in the large-qT domain for all the involved partonic processes. While playing a minor role at larger transverse momenta, we show that the newly incorporated boundary contribution plays a vital role in the $q_{\mathrm{T}}\to 0$ limit, where any subleading power accuracy would be lost without them. In particular, our NNLP-accurate qT expansion can approximate the exact qT distribution up to $q_{\mathrm{T}}\sim 30\text{GeV}$ at the percent level for rapidities $|Y_H|\lesssim 3$.

    hep-phJHEP(2024)·15 citations
16. 16*

    Spinning Pairs: Supporting ${}^3{P}_0$ Quark-Pair Creation from Landau Gauge Green's Functions

    Reinhard Alkofer (Graz U.)🇦🇹 · Felipe J. Llanes-Estrada (Univ. Complutense de Madrid and IPARCOS)🇪🇸 · Alexandre Salas-Bernardez (IFIC and Univ. Valencia, Univ. Complutense de Madrid and IPARCOS)🇪🇸

    Abundant phenomenology suggests that strong decays from relatively low-excitation hadrons into other hadrons proceed by the creation of a light quark-antiquark pair with zero total angular momentum, the so called ${}^3{P}_0$ mechanism originating from a scalar bilinear. Yet the Quantum Chromodynamics (QCD) interaction is perturbatively mediated by gluons of spin one, and QCD presents a chirally symmetric Lagrangian. Such scalar decay term must be spontaneously generated upon breaking chiral symmetry. We attempt to reproduce this with the help of the quark-gluon vertex in Landau gauge, whose nonperturbative structure has been reasonably elucidated in the last years, and insertions of a uniform, constant chromoelectric field. This is akin to Schwinger pair production in Quantum Electrodynamics (QED), and we provide a comparison with its two field-insertions diagram. We find that, the symmetry being cylindrical, the adequate quantum numbers to discuss the production are rather ${}^3{\Sigma }_0$, ${}^3{\Sigma }_1$ and ${}^3{\Pi }_0$ as in diatomic molecules, and we indeed find a sizeable contribution of the third decay mechanism, which may give a rationale for the ${}^3{P}_0$ phenomenology, as long as the momentum of the produced pair is at or below the scale of the bare or dynamically generated fermion mass. On the other hand, ultrarelativistic fermions are rather ejected with ${}^3{\Sigma }_1$ quantum numbers. In QED, our results suggest that ${}^3{\Sigma }_0$ dominates, whereas the constraint of producing a color singlet in QCD leads to ${}^3{\Pi }_0$ dominance at sub-GeV momenta.

    hep-phPRD(2024)·7 citations
17. 17*

    Nucleon resonance parameters from Roy-Steiner equations

    Martin Hoferichter🇨🇭 · Jacobo Ruiz de Elvira🇪🇸 · Bastian Kubis🇩🇪 · Ulf-G. Meißner🇩🇪

    A reliable determination of the pole parameters and residues of nucleon resonances is notoriously challenging, given the required analytic continuation into the complex plane. We provide a comprehensive analysis of such resonance parameters accessible with Roy-Steiner equations for pion-nucleon scattering - a set of partial-wave dispersion relations that combines the constraints from analyticity, unitarity, and crossing symmetry - most prominently of the $\Delta (1232)$ resonance. Further, we study the Roper, $N(1440)$, resonance, which lies beyond the strict domain of validity, in comparison to Padé approximants, comment on the role of subthreshold singularities in the $S$-wave, and determine the residues of the $f_0(500)$, $\rho (770)$, and $f_0(980)$ resonances in the $t$-channel process $\pi \pi \to \bar{N}N$. The latter allows us to test - for the first time fully model independently in terms of the respective residues - universality of the $\rho (770)$ couplings and the Goldberger-Treiman relation expected if the scalars behaved as dilatons, in both cases revealing large deviations from the narrow-resonance limit.

    hep-phhep-latnucl-thPLB(2024)·51 citations
18. 18*

    Neutrinoless Double Beta Decay without Vacuum Majorana Neutrino Mass

    Lukáš Gráf🇺🇸 · Sudip Jana🇩🇪 · Oliver Scholer🇩🇪 · Nele Volmer🇩🇪

    We present a proof-of-concept extension to the Standard Model that can generate a non-vanishing neutrinoless double beta decay ($0\nu \beta \beta$) signal without the existence of Majorana neutrinos or lepton number violation in the zero-density vacuum-ground-state Lagrangian. We propose that the $0\nu \beta \beta$ can be induced by the capture of an ultralight scalar field, a potential dark matter candidate, that carries two units of lepton number. This makes the observable $0\nu \beta \beta$ spectrum indistinguishable from the usual $0\nu \beta \beta$ mechanisms by any practical means. We find that a non-zero $0\nu \beta \beta$ rate does not require neutrinos to be fundamentally Majorana particles. However, for sizeable decay rates within the range of next-generation experiments, the neutrino will, generally, acquire an (effective) Majorana mass as the scalar field undergoes a transition to the Bose-Einstein condensate phase. We also discuss the distinction between the aforementioned scenario and the case in which the emission of a lepton-number-two scalar leads to $0\nu \beta \beta$, exhibiting discernible qualitative features that make it experimentally distinguishable from the conventional scenario.

    hep-phhep-exnucl-thPLB(2024)·15 citations
19. 19*

    Numerical evidence for fractional topological objects in SU(3) gauge theory

    Jackson A. Mickley🇦🇺 · Waseem Kamleh🇦🇺 · Derek B. Leinweber🇦🇺

    The continued development of models that propose the existence of fractional topological objects in the Yang-Mills vacuum has called for a quantitative method to study the topological structure of $\mathrm{SU}(N)$ gauge theory. We present an original numerical algorithm that can identify distinct topological objects in the nontrivial ground-state fields and approximate the net charge contained within them. This analysis is performed for $\mathrm{SU}(3)$ colour at a range of temperatures crossing the deconfinement phase transition, allowing for an assessment of how the topological structure evolves with temperature. We find a promising consistency with the instanton-dyon model for the structure of the QCD vacuum at finite temperature. Several other quantities, such as object density and radial size, are also analysed to elicit a further understanding of the fundamental structure of ground-state gluon fields.

    ↳ hep-lathep-phnucl-thPRD(2024)·8 citations
20. 20*

    Observing dark matter clumps and asteroid-mass primordial black holes in the solar system with gravimeters and GNSS networks

    Bruno Bertrand🇧🇪 · Michal Cuadrat-Grzybowski🇳🇱 · Pascale Defraigne🇧🇪 · Michel Van Camp🇧🇪 · Sébastien Clesse🇧🇪

    In this proceedings, we study the possible gravitational impact of primordial black holes (PBHs) or dark matter (DM) clumps on GNSS satellite orbits and gravimeter measurements. It provides a preliminary step to the future exhaustive statistical analysis over 28 years of gravimeter and GNSS data to get constraints over the density of asteroid-mass PBH and DM clumps inside the solar system. Such constraints would be the first to be obtained by direct observation on a terrestrial scale.

    ↳ astro-ph.COastro-ph.EPgr-qchep-ph17 citations
21. 21*

    Extrapolating semileptonic form factors using Bayesian-inference fits regulated by unitarity and analyticity

    J.M. Flynn🇬🇧 · A. Jüttner🇬🇧 · J.T. Tsang🇨🇭

    We discuss our recently proposed model-independent framework for fitting hadronic form-factor data, which are often only available at discrete kinematical points, using parameterisations based on unitarity and analyticity. The accompanying dispersive bound on the form factors (unitarity constraint) is used to regulate the ill-posed fitting problem and allow model-independent predictions over the entire physical range. Kinematical constraints, for example for the vector and scalar form factors in semileptonic meson decays, can be imposed exactly. The core formulae are straight-forward to implement with standard math libraries. We demonstrate the method for the exclusive semileptonic decay $B_s\to K\ell \nu$, an example requiring one to use a generalisation of the original Boyd Grinstein Lebed (BGL) unitarity constraint. We further present a first application of the method to $B\to D^{\ast }\ell \nu$ decays.

    ↳ hep-lathep-phPoS(2024)·3 citations
22. 22*

    Electromagnetic effects on topological observables in QCD

    Bastian B. Brandt🇩🇪 · Gergely Endrődi🇩🇪 · José Javier Hernández Hernández🇩🇪 · Gergely Markó🇩🇪 · Laurin Pannullo🇩🇪

    In this proceedings article we present a selected set of our lattice results regarding the effect that background electromagnetic fields have on the topology of QCD. In particular, we report on the lattice spacing-dependence of the axion-photon coupling as well as on the response of the topological susceptibility to strong magnetic fields at nonzero temperatures. We demonstrate that the ratio of topological susceptibilities at finite to zero magnetic field has a well behaved continuum limit at low temperatures using a reweighting technique. Moreover, we study the scaling of the axion-photon coupling towards the continuum limit and show that it is less severely affected by discretisation effects.

    ↳ hep-lathep-phhep-thPoS(2024)·4 citations
23. 23*

    Fermions at finite density in the path integral approach

    Alessandro Podo🇺🇸 · Luca Santoni🇫🇷

    We study relativistic fermionic systems in $3+1$ spacetime dimensions at finite chemical potential and zero temperature, from a path-integral point of view. We show how to properly account for the $i\epsilon$ term that projects on the finite density ground state, and compute the path integral analytically for free fermions in homogeneous external backgrounds, using complex analysis techniques. As an application, we show that the $\mathrm{U}(1)$ symmetry is always linearly realized for free fermions at finite charge density, differently from scalars. We study various aspects of finite density QED in a homogeneous magnetic background. We compute the free energy density, non-perturbatively in the electromagnetic coupling and the external magnetic field, obtaining the finite density generalization of classic results of Euler--Heisenberg and Schwinger. We also obtain analytically the magnetic susceptibility of a relativistic Fermi gas at finite density, reproducing the de Haas--van Alphen effect. Finally, we consider a (generalized) Gross--Neveu model for $N$ interacting fermions at finite density. We compute its non-perturbative effective potential in the large-$N$ limit, and discuss the fate of the $\mathrm{U}(1)$ vector and ${\mathbb{Z}}_2^A$ axial symmetries.

    ↳ hep-thhep-phmath-phmath.MPJHEP(2024)·8 citations
24. 24*

    New Light on Dark Extended Lenses with the Roman Space Telescope

    William DeRocco🇺🇸 · Nolan Smyth🇺🇸 · Volodymyr Takhistov🇯🇵

    The Roman Space Telescope's Galactic Bulge Time Domain Survey will constitute the most sensitive microlensing survey of the Galactic Bulge to date, opening up new opportunities to search for dark matter (DM). Many extensions of the Standard Model predict the formation of extended DM substructures, such as DM subhalos, boson/axion stars, and halo-dressed primordial black holes. We demonstrate that for such targets, Roman will be sensitive to a broad parameter space up to four orders of magnitude below existing constraints. Our analysis can be readily applied to other extended DM configurations as well.

    ↳ astro-ph.COhep-phApJL(2024)·14 citations
25. 25*

    Family Puzzle, Framing Topology, $c_{-}=24$ and 3(E8)${}_1$ Conformal Field Theories: 48/16 = 45/15 = 24/8 =3

    Juven Wang🇺🇸

    Family Puzzle or Generation Problem demands an explanation of why there are 3 families or generations of quarks and leptons in the Standard Model of particle physics. Here we propose a novel solution -- the multiple of 3 families of 16 Weyl fermions (namely $(N_f=3)\times 16$) in the 3+1d spacetime dimensions are topologically robust due to constraints rooted in profound mathematics (such as Hirzebruch signature and Rokhlin theorems, and cobordism) and derivable in physics (such as chiral edge states, quantized thermal Hall conductance, and gravitational Chern-Simons theory), which holds true even forgetting or getting rid of any global symmetry or gauge structure of the Standard Model. By the dimensional reduction through a sequence of sign-reversing mass domain wall of domain wall and so on, we reduce the Standard Model fermions to obtain the $(N_f=3)\times 16$ multiple of 1+1d Majorana-Weyl fermion with a total chiral central charge $c_{-}=24$. Effectively via the fermionization-bosonization, the 1+1d theory becomes 3 copies of $c_{-}=8$ of (E${}_8{)}_1$ conformal field theory, living on the boundary of 3 copies of 2+1d E${}_8$ quantum Hall states. Based on the framing anomaly-free $c_{-}=0\mathrm{mod}24$ modular invariance, the framed bordism and string bordism ${\mathbb{Z}}_{24}$ class, the 2-framing and $p_1$-structure, the $w_1$-$p_1$ bordism ${\mathbb{Z}}_3$ class constraints, we derive the family number constraint $N_f\in (\frac{48}{16}=\frac{24}{8}=3)\mathbb{Z}$. The dimensional reduction process, although not necessary, is sufficiently supported by the ${\mathbb{Z}}_{16}$ class Smith homomorphism. We also comment on the $\frac{45}{15}=3$ relation: the 3 families of 15 Weyl-fermion Standard Model vacuum where the absence of some sterile right-handed neutrinos is fulfilled by additional topological field theories or conformal field theories in Ultra Unification.

    ↳ hep-thcond-mat.str-elhep-lathep-ph+27 citations
26. 26*

    Toward Initial Conditions of Conserved Charges

    Patrick Carzon🇺🇸

    At top collider energies where baryon stopping is negligible, the initial state of heavy ion collisions is overall charge neutral and predominantly composed of gluons. Nevertheless, there can also be significant local fluctuations of the baryon number, strangeness, and electric charge densities about zero, perturbatively corresponding to the production of quark/antiquark pairs. These previously ignored local charge fluctuations can permit the study of charge diffusion in the quark-gluon plasma (QGP), even at top collider energies. In this paper we present a new model denoted \code{iccing} (Initial Conserved Charges in Nuclear Geometry) which can reconstruct the initial conditions of conserved charges in the QGP by sampling a ($g\to q\bar{q}$) splitting probability over the initial energy density. We find that the new charge distributions generally differ from the bulk energy density; in particular, the strangeness distribution is significantly more eccentric than standard bulk observables and appears to be associated with the geometry of hot spots in the initial state. The new information provided by these conserved charges opens the door to studying a wealth of new charge- and flavor-dependent correlations in the initial state and ultimately the charge transport parameters of the QGP.

    ↳ nucl-thhep-phnucl-ex0 citations
27. 27*

    Bootstrapping mesons at large $N$: Regge trajectory from spin-two maximization

    Jan Albert🇺🇸 · Johan Henriksson🇮🇹 · Leonardo Rastelli🇺🇸 · Alessandro Vichi🇮🇹

    We continue the investigation of large $N$ QCD from a modern bootstrap perspective, focusing on the mesons. We make the natural spectral assumption that the $2\to 2$ pion amplitude must contain, above the spin-one rho meson, a massive resonance of spin two. By maximizing its coupling we find a very interesting extremal solution of the dual bootstrap problem, which appears to contain at least a full Regge trajectory. Its low-lying states are in uncanny quantitative agreement with the meson masses in the real world.

    ↳ hep-thhep-lathep-phJHEP(2024)·50 citations

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