Fri·Jan 7, 2022Friday·January 7, 2022

1. 01*

   A Robust Description of Hadronic Decays in Light Vector Mediator Models

   Ana Luisa Foguel🇧🇷 · Peter Reimitz🇧🇷 · Renata Zukanovich Funchal🇧🇷

   Abelian U(1) gauge group extensions of the Standard Model represent one of the most minimal approaches to solve some of the most urgent particle physics questions and provide a rich phenomenology in various experimental searches. In this work, we focus on baryophilic vector mediator models in the MeV-to-GeV mass range and, in particular, present, for the first time, gauge vector field decays into almost arbitrary hadronic final states. Using only very little theoretical approximations, we rigorously follow the vector meson dominance theory in our calculations. We study the effect on the total and partial decay widths, the branching ratios, and not least on the present (future) experimental limits (reach) on (for) the mass and couplings of light vector particles in different models. We compare our results to current results in the literature. Our calculations are publicly available in a python package to compute various vector particle decay quantities in order to describe leptonic as well as hadronic decay signatures for experimental searches.

   hep-phhep-exJHEP(2022)·26 citations
2. 02*

   Hyperons and ${\Theta }_s^{+}$ in Holographic QCD

   Yizhuang Liu🇵🇱 · Maciej A. Nowak🇵🇱 · Ismail Zahed🇺🇸

   We revisit the holographic description of strange baryons in the context of the Sakai-Sugimoto construction, by considering the strange quark mass as heavy. Hyperons are described by a massive $(K,K^{\ast })$ multiplet, bound to a light-flavor instanton in bulk, much in the spirit of the Callan-Klebanov construction. The modular Hamiltonian maps onto the Landau problem, a charged particle in a 2-dimensional external magnetic field, induced by the bulk Chern-Simons interaction, plus spin-orbit coupling. The ensuing holographic hyperon spectrum compares fairly with the empirical one. The holographic strange pentaquark baryon ${\Theta }_s^{+}$ is shown to be unbound.

   hep-phnucl-exnucl-thPRD(2022)·5 citations
3. 03*

   The $\overline{\mathrm{MS}}$ renormalization constant of the singlet axial current operator at $\mathcal{O}({\alpha }_s^5)$ in QCD

   Long Chen🇩🇪 · Michał Czakon🇩🇪

   We provide the $\overline{\mathrm{MS}}$ factor of the renormalization constant of the singlet axial-current operator in dimensional regularization at $\mathcal{O}({\alpha }_s^5)$ in perturbative Quantum Chromodynamics (QCD). The result is obtained from a formula derived using the Adler-Bell-Jackiw equation in terms of renormalized operators. The required input consists of the complete four-loop results for operator renormalization constants obtained by explicit diagrammatic computation in a previous publication.

   hep-phhep-thPLB(2022)·7 citations
4. 04*

   Parton distribution effects in the direct photon production at hadron collisions

   David F. Rentería-Estrada🇲🇽 · Roger J. Hernández-Pinto🇲🇽 · German F. R. Sborlini🇩🇪

   Parton distribution functions are crucial to understand the internal kinematics of hadrons. There are currently a large number of distribution functions on the market, and thanks to today's technology, performing computational analysis of the differential cross-sections has become more accessible. Despite technological advances, accurately accessing to the internal structure of hadrons remains a difficult task from a theoretical point of view. In this work, we analyze the impact on the differential cross-sections when updating the sets of parton distribution and fragmentation functions, for the production of one hadron plus a direct photon at the energy scale of RHIC and LHC experiments.

   hep-phRev.Mex.Fis.Suppl.(2022)·0 citations
5. 05*

   Radially excited (n=3)charm mesons in heavy quark effective theory

   Ritu Garg🇮🇳 · Kundan Kumar🇺🇸 · Alka Upadhyay🇮🇳

   By exploring heavy quark effective theory (HQET), we use theoretical available data for bottom mesons to analysis the masses and decays for n = 3 charm mesons. From the predicted masses, we studied ground state strong decay modes in terms of couplings. Comparing the decays with available total decay widths, we provide upper bounds on the associated couplings. We also plot Regge trajectories for our predicted data in planes (J, $M^2$ ) and ($n_r$, $M^2$ ) and estimated higher masses (n = 4) by fixing Regge slopes and intercepts. These Regge trajectories are used to clarify $D_2^{\ast }(3000)$ state's $J^P$ as 1F ($2^{+}$) state. The presented results may further get confirmation through upcoming experimental information.

   hep-phPTEP(2022)·2 citations
6. 06*

   Zee model with quasidegenerate neutrino masses and where to find it

   R. Primulando🇮🇩 · J. Julio🇮🇩 · P. Uttayarat🇹🇭

   We present a Zee model with a family dependent $Z_2$ symmetry for radiative neutrino masses. Our motivation is to get a model that correctly describes neutrino oscillation phenomena, while at the same time offers definite predictions. The imposed $Z_2$ symmetry greatly reduces the number of free parameters in the model. These parameters are then determined from the neutrino data, from which one can study its outcomes. Our setup only admits quasidegenerate neutrino masses with the sum of neutrino masses between 100 and 130 meV, the effective Majorana mass between 20 and 40 meV, and the effective electron neutrino mass between 48 and 53 meV. The ratio of the vacuum expectation values of the Higgs doublets, $\text{tbeta}$, is found to be $\text{tbeta}\lesssim 0.5$ and $\text{tbeta}\gtrsim 10$. The former is ruled out by lepton flavor violation (LFV) processes, such as $\mu \to e\gamma$ and $\mu \to e$ conversion, which are determined up to two loops. For the latter, these LFV processes are within reach of the next generation of experiments. Moreover, for $\text{tbeta}\gtrsim 10$, the couplings of heavy neutral scalars to dimuon are significant. If they are sufficiently light, i.e., $\lesssim 200$ GeV, collider search for their decays into muon pair provides a stronger constraint on most parts of the model parameter space than the LFV ones.

   hep-phhep-exEPJC(2022)·4 citations
7. 07*

   Anomalous enhancement of dilepton production as a precursor of color superconductivity

   Toru Nishimura🇯🇵 · Masakiyo Kitazawa🇯🇵 · Teiji Kunihiro🇯🇵

   We compute the modification of the photon self-energy due to dynamical diquark fluctuations developed near the critical temperature of the color superconductivity through the Aslamasov-Larkin, Maki-Thompson and density of states terms, which are responsible for the paraconductivity in metals at vanishing energy and momentum. It is shown that the rate has a significant enhancement at low invariant-mass region over a rather wide range of temperature in the normal phase. This enhancement is worth exploration in the relativistic heavy-ion collisions, which may thereby reveal the significance of the diquark fluctuations in dense quark matter.

   hep-phnucl-exnucl-thPTEP(2022)·18 citations
8. 08*

   Modular Flavour Symmetries and Modulus Stabilisation

   P. P. Novichkov🇫🇷 · J. T. Penedo🇵🇹 · S. T. Petcov🇮🇹

   We study the problem of modulus stabilisation in the framework of the modular symmetry approach to the flavour problem. By analysing simple UV-motivated CP-invariant potentials for the modulus $\tau$ we find that a class of these potentials has (non-fine-tuned) CP-breaking minima in the vicinity of the point of ${\mathbb{Z}}_3^{ST}$ residual symmetry, $\tau \simeq e^{2\pi i/3}$. Stabilising the modulus at these novel minima breaks spontaneously the CP symmetry and can naturally explain the mass hierarchies of charged leptons and possibly of quarks.

   hep-phhep-thJHEP(2022)·87 citations
9. 09*

   Improved bounds on ultralight scalar dark matter in the radio-frequency range

   Oleg Tretiak (1,2)🇩🇪 · Xue Zhang (1,2)🇩🇪 · Nataniel L. Figueroa (1,2)🇩🇪 · Dionysios Antypas (1,2)🇩🇪 · Andrea Brogna (1)🇩🇪 · Abhishek Banerjee (3)🇮🇱 · Gilad Perez (3)🇮🇱 · Dmitry Budker (1,2,4)((1) Johannes Gutenberg-Universität Mainz, Germany, (2) Helmholtz-Institut, GSI Helmholtzzentrum für Schwerionenforschung, Mainz, Germany, (3) Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot, Israel, (4) Department of Physics, University of California, Berkeley, California, USA)🇩🇪

   We present a search for fundamental constant oscillations in the range $20$~kHz-$100$ MHz, that may arise within models for ultralight dark matter (UDM). Using two independent, significantly upgraded optical-spectroscopy apparatus, we achieve up to $\times$1000 greater sensitivity in the search relative to previous work. We report no observation of UDM and thus constrain respective couplings to electrons and photons within the investigated UDM particle mass range $8\cdot 10^{-11}-4\cdot 10^{-7}$ eV. The constraints significantly exceed previously set bounds, and as we show, may surpass in future experiments those provided by equivalence-principle experiments in a specific case regarding the combination of UDM couplings probed by the latter.

   hep-phastro-ph.COphysics.atom-phquant-phPRL(2022)·58 citations
10. 10*

    Analyzing transverse momentum spectra by a new method in high-energy collisions

    Li-Li Li🇨🇳 · Fu-Hu Liu🇨🇳 · Muhammad Waqas🇨🇳 · Muhammad Ajaz🇵🇰

    We analyzed the transverse momentum spectra of positively and negatively charged pions (${\pi }^{+}$ and ${\pi }^{-}$), positively and negatively charged kaons ($K^{+}$ and $K^{-}$), protons and antiprotons ($p$ and $\bar{p}$), as well as $\varphi$ produced in mid-(pseudo)rapidity region in central nucleus--nucleus (AA) collisions over a center-of-mass energy range from 2.16 to 2760 GeV per nucleon pair. The transverse momentum of the considered particle is regarded as the joint contribution of two participant partons which obey the modified Tsallis-like transverse momentum distribution and have random azimuths in superposition. The calculation of transverse momentum distribution of particles is performed by the Monte Carlo method and compared with the experimental data measured by international collaborations. The excitation functions of effective temperature and other parameters are obtained in the considered energy range. With the increase of collision energy, the effective temperature parameter increases quickly and then slowly. The boundary appears at around 5 GeV, which means the change of reaction mechanism and/or generated matter.

    hep-phhep-exnucl-exnucl-thUniverse(2022)·17 citations
11. 11*

    How well do we know the gluon polarization in the proton?

    Y. Zhou🇨🇳 · N. Sato🇺🇸 · W. Melnitchouk🇺🇸

    We perform the first simultaneous global QCD analysis of spin-averaged and spin-dependent parton distribution functions (PDFs), including single jet production data from unpolarized and polarized hadron collisions. We critically assess the impact of SU(3) flavor symmetry and PDF positivity assumptions on the quark and gluon helicity PDFs, and find strong bias from these, particularly on the gluon polarization. The simultaneous analysis allows for the first time extraction of individual helicity-aligned and antialigned PDFs with a consistent treatment of uncertainties.

    hep-phhep-exnucl-thPRD(2022)·62 citations
12. 12*

    A Flavor Change Study based on Dyson-Schwinger Equation

    Xue-ao Chao🇨🇳 · Yu-xin Liu🇨🇳

    We study the flavor change effects using the Dyson-Schwinger (DS) equation in a multi-flavor system. By taking the Electroweak interaction as perturbation into conditions, the ${\text{SU(4)}}_{\text{L}}\to {\text{SU(2)}}_{\text{L}}\otimes {\text{SU(2)}}_{\text{L}}\to {\text{SO(2)}}_{\text{L}}\otimes {\text{SO(2)}}_{\text{L}}$ symmetry breaking chain is studied. Under this symmetry breaking pattern fermion masses are split, and we can identify the fermions with different masses as different generations. Quark mass spectrum is then given. Meanwhile, there are a total of fifteen Goldstones but only four of them are independent. The Goldstones have electric charges $0$, $0$, $+1$, $-1$, respectively. One of them becomes pseudo-Nambu-Goldstone boson (pNGB) and gains a mass due to the Electroweak interaction perturbation. It can be identified as the Higgs boson. The other three Goldstones maintain massless and will be eaten by gauge bosons to give $W^{\pm }$ and $Z^0$ masses via Schwinger mechanism. Thus, the Goldstones can take the role of the Higgs boson.

    hep-ph0 citations
13. 13*

    Parton distribution function for topological charge at one loop

    Anatoly Radyushkin🇺🇸 · Shuai Zhao🇺🇸

    We present results for the $gg$-part of the one-loop corrections to the recently introduced "topological charge" GPD $\tilde{F}(x,q^2)$. In particular, we give expression for its evolution kernel. To enforce strict compliance with the gauge invariance requirements, we have used on-shell states for external gluons, and have obtained identical results both in Feynman and light-cone gauges. No "zero mode" $\delta (x)$ terms were found for the twist-4 gluon GPD $\tilde{F}(x,q^2)$.

    hep-phhep-latJHEP(2022)·8 citations
14. 14*

    Solving Combinatorial Problems at Particle Colliders Using Machine Learning

    Anthony Badea🇺🇸 · William James Fawcett🇬🇧 · John Huth🇺🇸 · Teng Jian Khoo🇩🇪 · Riccardo Poggi🇨🇭 · Lawrence Lee🇺🇸

    High-multiplicity signatures at particle colliders can arise in Standard Model processes and beyond. With such signatures, difficulties often arise from the large dimensionality of the kinematic space. For final states containing a single type of particle signature, this results in a combinatorial problem that hides underlying kinematic information. We explore using a neural network that includes a Lorentz Layer to extract high-dimensional correlations. We use the case of squark decays in $R$-Parity-violating Supersymmetry as a benchmark, comparing the performance to that of classical methods. With this approach, we demonstrate significant improvement over traditional methods.

    hep-phhep-exPRD(2022)·23 citations
15. 15*

    Status of Lattice QCD Determination of Nucleon Form Factors and their Relevance for the Few-GeV Neutrino Program

    Aaron S. Meyer🇺🇸 · André Walker-Loud🇺🇸 · Callum Wilkinson🇺🇸

    Calculations of neutrino-nucleus cross sections begin with the neutrino-nucleon interaction, making the latter critically important to flagship neutrino oscillation experiments, despite limited measurements with poor statistics. Alternatively, lattice QCD (LQCD) can be used to determine these interactions from the Standard Model with quantifiable theoretical uncertainties. Recent LQCD results of $g_{\mathrm{A}}$ are in excellent agreement with data, and results for the (quasi-)elastic nucleon form factors with full uncertainty budgets are expected within a few years. We review the status of the field and LQCD results for the nucleon axial form factor, $F_{\mathrm{A}}(Q^2)$, a major source of uncertainty in modeling sub-GeV neutrino-nucleon interactions. Results from different LQCD calculations are consistent, but collectively disagree with existing models, with potential implications for current and future neutrino oscillation experiments. We describe a road map to solidify confidence in the LQCD results and discuss future calculations of more complicated processes, important to few-GeV neutrino oscillation experiments.

    ↳ hep-lathep-exhep-phnucl-ex+1Ann.Rev.Nucl.Part.Sci.(2022)·81 citations
16. 16*

    Nondivergent deflection of light around a photon sphere of a compact object

    Ryuya Kudo🇯🇵 · Hideki Asada🇯🇵

    We demonstrate that the location of a stable photon sphere (PS) in a compact object is not always an edge such as the inner boundary of a black hole shadow, whereas the location of an unstable PS is known to be the shadow edge notably in the Schwarzschild black hole. If a static spherically symmetric (SSS) spacetime has the stable outermost PS, the spacetime cannot be asymptotically flat. A nondivergent deflection is caused for a photon traveling around a stable PS, though a logarithmic divergent behavior is known to appear in most of SSS compact objects with an unstable photon sphere. The reason for the nondivergence is that the closest approach of a photon is prohibited in the immediate vicinity of the stable PS when the photon is emitted from a source (or reaches a receiver) distant from a lens object. The finite gap size depends on the receiver and source distances from the lens as well as the lens parameters. The mild deflection angle of light can be approximated by an arcsine function. A class of SSS solutions in Weyl gravity exemplify the nondivergent deflection near the stable outer PS.

    ↳ gr-qcastro-ph.HEhep-phhep-thPRD(2022)·10 citations
17. 17*

    Probing QCD critical point and induced gravitational wave by black hole physics

    Rong-Gen Cai🇨🇳 · Song He🇨🇳 · Li Li🇨🇳 · Yuan-Xu Wang🇨🇳

    Locating the critical endpoint of QCD and the region of a first-order phase transition at finite baryon chemical potential is an active research area for QCD matter. We provide a gravitational dual description of QCD matter at finite baryon chemical potential and finite temperature using the non-perturbative approach from gauge/gravity duality. After fixing all model parameters using state-of-the-art lattice QCD data at zero chemical potential, the predicted equations of state and QCD trace anomaly relation are in quantitative agreement with the latest lattice results. We then give the exact location of the critical endpoint as well as the first-order transition line, which is within the coverage of many upcoming experimental measurements. Moreover, using the data from our model at finite baryon chemical potential, we calculate the spectrum of the stochastic gravitational wave background associated with the first-order QCD transition in the early universe, which could be observable via pulsar timing in the future.

    ↳ hep-thgr-qchep-phPRD(2022)·90 citations
18. 18*

    Cosmological constant problem on the horizon

    Hassan Firouzjahi🇮🇷

    We revisit the quantum cosmological constant problem and highlight the important roles played by the dS horizon of zero point energy. We argue that fields which are light enough to have dS horizon of zero point energy comparable to the FLRW Hubble radius are the main contributors to dark energy. On the other hand, the zero point energy of heavy fields develop nonlinearities on sub-Hubble scales and can not contribute to dark energy. We speculate that our proposal may provide a resolution for both the old and new cosmological constant problems by noting that there exists a field, the (lightest) neutrino, which happens to have a mass comparable to the present background photon temperature. The proposal predicts multiple transient periods of dark energy in early and late expansion history of the universe yielding to a higher value of the current Hubble expansion rate which can resolve the $H_0$ tension problem.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2022)·15 citations
19. 19*

    Collective expansion in pp collisions using the Tsallis statistics

    J.B. Gu🇨🇳 · C.Y. Li🇨🇳 · Q. Wang🇨🇳 · W.C. Zhang🇨🇳 · H. Zheng🇨🇳

    We investigate the transverse momentum ($p_{\mathrm{T}}$) spectra of identified hadrons in minimum-bias proton-proton (pp) collisions at a centre-of-mass energy ($\sqrt{s}$) of 0.9, 2.76, 5.02, 7 and 13 TeV in the framework of Tsallis-blast wave (TBW) model. It is found that the model describes well the particle spectra up to 10 GeV/c. The radial flow ($⟨\beta ⟩$) increases with the collision energy. The degrees of non-equilibrium ($q$) and the Tsallis temperature parameter ($T$) show a similar behaviour, but with a much weaker trend. With this dependence of the freeze-out parameters on the collision energy, we evaluate $⟨\beta ⟩$, $T$ and $q$ in pp collisions at $\sqrt{s}=$ 8 and 14 TeV and predict the particle spectra at these two energies. Moreover, in order to investigate the multiplicity dependence of the freeze-out parameters, the TBW model is extended to the spectra at different charged-particle multiplicity classes in pp collisions at $\sqrt{s}=$ 7 and 13 TeV. It is observed that at both energies the radial flow increases with the multiplicity while the degree of non-equilibrium shows an opposite behaviour, which is similar to that observed in proton-nucleus (pA) and nucleus-nucleus (AA) collisions at the Large Hadron Collider (LHC) energies. However, the Tsallis temperature parameter increases with the multiplicity, which is opposite to the trend in pA and AA collisions. At similar multiplicities, the radial flow in pp collisions is stronger than those in pA and AA collisions, indicating that the size of the colliding system has significant effects on the final state particle dynamics. Finally, we apply an additional flow correction to the Tsallis temperature parameter and find that the doppler-corrected temperature parameter almost scales with the multiplicity in a uniform way, despite the difference in the colliding system and collision energy.

    ↳ nucl-thhep-phJ.Phys.G(2022)·22 citations
20. 20*

    Unexciting classical backgrounds

    Tanmay Vachaspati🇺🇸

    Quantum fields in time-dependent backgrounds generally lead to particle production. Here we consider "unexciting" backgrounds for which the net particle production vanishes. We start by considering the simple harmonic oscillator and explicitly construct all unexciting time-dependent frequencies. This allows us to construct homogeneous backgrounds in field theory for which there is no particle production in any given mode, though we are able to show that there are no homogeneous backgrounds for which the particle production vanishes in every mode. We then construct general inhomogeneous unexciting field theory backgrounds. The set of all unexciting field theory backgrounds will be further restricted by the choice of physical interactions and this leads to an interesting open problem.

    ↳ hep-thgr-qchep-phPRD(2022)·3 citations
21. 21*

    Finding Evidence for Inflation and the Origin of Galactic Magnetic Fields with CMB Surveys

    Sayan Mandal🇺🇸 · Neelima Sehgal🇺🇸 · Toshiya Namikawa🇯🇵

    The origin of the $\mu$G magnetic fields observed in galaxies is unknown. One promising scenario is that magnetic fields generated during inflation, larger than 0.1 nG on Mpc scales, were adiabatically compressed to $\mu$G strengths in galaxies during structure formation. Thus, detecting a scale-invariant primordial magnetic field (PMF) above 0.1 nG on Mpc scales just after recombination would indicate an inflationary origin of galactic magnetic fields. This would also provide compelling evidence that inflation occurred since only an inflationary mechanism could generate such a strong, scale-invariant magnetic field on Mpc scales. In contrast, constraining the scale-invariant PMF strength to be below 0.1 nG would imply an inflationary scenario is not the primary origin, since such weak PMFs cannot be amplified enough via adiabatic compression to produce the strength of the galactic fields we observe today. We find that measurements of anisotropic birefringence by future CMB surveys will be able to improve the sensitivity to Mpc-scale inflationary PMFs by an order of magnitude, and, in particular, that CMB-HD would lower the upper bound to 0.072 nG at the 95% C.L., which is below the critical 0.1 nG threshold for ruling out a purely inflationary origin. If inflationary PMFs exist, we find that a CMB-HD survey would be able to detect them with about $3\sigma$ significance or higher, providing evidence for inflation itself.

    ↳ astro-ph.COastro-ph.GAhep-phPRD(2022)·14 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.