Fri·Oct 18, 2019Friday·October 18, 2019

1. 01*

   Two-loop thermal spectral functions with general kinematics

   Greg Jackson🇨🇭

   Spectral functions at finite temperature and two-loop order are investigated, for a medium consisting of massless particles. We consider them in the timelike and spacelike domains, allowing the propagating particles to be any valid combination of bosons and fermions. Divergences (if present) are analytically derived and set aside for the remaining finite part to be calculated numerically. To illustrate the utility of these 'master' functions, we consider transverse and longitudinal parts of the QCD vector channel spectral function.

   hep-phPRD(2019)·27 citations
2. 02*

   Pseudosmooth Tribrid Inflation in $SU(5)$

   Muhammad Atif Masoud🇵🇰 · Mansoor Ur Rehman🇵🇰 · Qaisar Shafi🇺🇸

   A realistic tribrid model of sneutrino inflation is constructed in an $R$-symmetric $SU(5)$ grand unified theory (GUT). To avoid the monopole problem, a pseudosmooth inflationary trajectory is generated with the help of an additional $Z_5$ symmetry which is broken during and after inflation. The predictions of inflationary parameters are made at the central value of the scalar spectral index, $n_s=0.968$. The largest possible value of the tensor to scalar ratio, $r\lesssim 0.0027$, is obtained with sub-Planckian field values ($\lesssim m_P$). A successful realization of reheating and leptogenesis is achieved by avoiding the gravitino problem with a reheat temperature as low as $10^6$ GeV. The predicted range of the gauge symmetry breaking scale, $5\times 10^{16}\lesssim M/\text{GeV}\lesssim 5\times 10^{17}$, turns out to be somewhat larger than the typical GUT scale. With additional vector-like families, a successful gauge coupling unification is achieved by avoiding the no-go theorem related to $R$-symmetric $SU(5)$ GUT.

   hep-phastro-ph.COJCAP(2020)·17 citations
3. 03*

   Inclusive Nucleon Decay Searches as a Frontier of Baryon Number Violation

   Julian Heeck🇺🇸 · Volodymyr Takhistov🇺🇸

   Proton decay, and the decay of nucleons in general, constitutes one of the most sensitive probes of high-scale physics beyond the Standard Model. Most of the existing nucleon decay searches have focused primarily on two-body decay channels, motivated by Grand Unified Theories and supersymmetry. However, many higher-dimensional operators violating baryon number by one unit, $\Delta B=1$, induce multi-body nucleon decay channels, which have been only weakly constrained thus far. While direct searches for all such possible channels are desirable, they are highly impractical. In light of this, we argue that inclusive nucleon decay searches, $N\to X+$anything (where $X$ is a light Standard Model particle with an unknown energy distribution), are particularly valuable, as are model-independent and invisible nucleon decay searches such as $n\to$ invisible. We comment on complementarity and opportunities for such searches in the current as well as upcoming large-scale experiments Super-Kamiokande, Hyper-Kamiokande, JUNO, and DUNE. Similar arguments apply to $\Delta B>1$ processes, which kinematically allow for even more involved final states and are essentially unexplored experimentally.

   hep-phhep-exPRD(2020)·86 citations
4. 04*

   Rephasing invariance and permutation symmetry in flavor physics

   T. K. Kuo🇺🇸 · S. H. Chiu🇹🇼

   With some modifications, the arguments for rephasing invariance can be used to establish permutation symmetry for the standard model. The laws of evolution of physical variables, which transform as tensors under permutation, are found to obey the symmetry, explicitly. We also propose to use a set of four mixing parameters, with unique properties, which may serve to characterize flavor mixing.

   hep-phEPJC(2020)·8 citations
5. 05*

   Interpretation of $Y_b(10750)$ as a tetraquark and its production mechanism

   Ahmed Ali🇩🇪 · Luciano Maiani🇮🇹 · Alexander Ya. Parkhomenko🇷🇺 · Wei Wang🇨🇳

   Recently, the Belle Collaboration has updated the analysis of the cross sections for the processes $e^{+}{e}^{-}\to {\rm Y}(nS){\pi }^{+}{\pi }^{-}$ ($n=1,2,3$) in the $e^{+}{e}^{-}$ center-of-mass energy range from 10.52 to 11.02 GeV. A new structure, called here $Y_b(10750)$, with the mass $M(Y_b)=(10752.7\pm 5.9_{-1.1}^{+0.7})$ MeV and the Breit-Wigner width $\Gamma (Y_b)=(35.5_{-11.3-3.3}^{+17.6+3.9})$ MeV was observed \cite{Abdesselam:2019gth}. We interpret $Y_b(10750)$ as a compact $J^{PC}=1^{--}$ state with a dominant tetraquark component. The mass eigenstate $Y_b(10750)$ is treated as a linear combination of the diquark-antidiquark and $b\bar{b}$ components due to the mixing via gluonic exchanges shown recently to arise in the limit of large number of quark colors. The mixing angle between $Y_b$ and ${\rm Y}(5S)$ can be estimated from the electronic width, recently determined to be ${\Gamma }_{ee}(Y_b)=(13.7\pm 1.8)$ eV. The mixing provides a plausible mechanism for $Y_b(10750)$ production in high energy collisions from its $b\bar{b}$ component and we work out the Drell-Yan and prompt production cross sections for $pp\to Y_b(10750)\to {\rm Y}(nS){\pi }^{+}{\pi }^{-}$ at the LHC. The resonant part of the dipion invariant mass spectrum in $Y_b(10750)\to {\rm Y}(1S){\pi }^{+}{\pi }^{-}$ and the corresponding angular distribution of ${\pi }^{+}$-meson in the dipion rest frame are presented as an example.

   hep-phhep-exPLB(2020)·34 citations
6. 06*

   Spontaneous SUSY breaking in natural SO(10) grand unified theory

   Nobuhiro Maekawa🇯🇵 · Yuji Omura🇯🇵 · Yoshihiro Shigekami🇨🇳 · Manabu Yoshida🇯🇵

   We propose a simple grand unified theory (GUT) scenario in which supersymmetry (SUSY) is spontaneously broken in visible sector. Our model is based on the GUT model that has been proposed to solve almost all problems in conventional GUT scenarios. In the previous work, the problems can be solved by a natural assumption in a supersymmetric vacuum. In this paper, we consider an extension of the model (i.e. omitting one singlet field) and break SUSY spontaneously without new sector. Our model does not have hidden sector and predicts high-scale SUSY where sfermion masses are of order 100-1000 TeV and flavor violating processes are suppressed. In this scenario, we can see an explicit signature of GUT in sfermion mass spectrum since the sfermion mass spectrum respects SU(5) matter unification. In addition, we find a superheavy long lived charged lepton as a proof of our scenario, and it may be seen in the LHC.

   hep-phPRD(2019)·2 citations
7. 07*

   Atomic and molecular transitions induced by axions via oscillating nuclear moments

   V. V. Flambaum🇦🇺 · H. B. Tran Tan🇦🇺 · D. Budker🇩🇪 · A. Wickenbrock🇩🇪

   The interaction of standard model's particles with the axionic Dark Matter field may generate oscillating nuclear electric dipole moments (EDMs), oscillating nuclear Schiff moments and oscillating nuclear magnetic quadrupole moments (MQMs) with a frequency corresponding to the axion's Compton frequency. Within an atom or a molecule an oscillating EDM, Schiff moment or MQM can drive transitions between atomic or molecular states. The excitation events can be detected, for example, via subsequent fluorescence or photoionization. Here we calculate the rates of such transitions. If the nucleus has octupole deformation or quadrupole deformation then the transition rate due to Schiff moment and MQM can be up to $10^{-16}$ transition per molecule per year. In addition, an MQM-induced transition may be of M2-type, which is useful for the elimination of background noise since M2-type transitions are suppressed for photons.

   hep-phphysics.atom-phPRD(2020)·10 citations
8. 08*

   The LbL contribution to the muon g-2 from the axial-vector mesons exchanges within the nonlocal quark model

   A. E. Dorokhov🇷🇺 · A. P. Martynenko🇷🇺 · F. A. Martynenko🇷🇺 · A. E. Radzhabov🇷🇺 · A. S. Zhevlakov🇷🇺

   The light-by-light contribution from the axial-vector (AV) mesons exchanges to the muon anomalous magnetic moment is estimated in the framework of the nonlocal chiral quark model. The preliminary answer for contributions from a1 and f1 mesons to (g-2)_mu is 0.34 x 10^(-11) and does not support the Melnikov-Vainshtein estimate 2.2 x 10^(-11).

   hep-phEPJ Web Conf.(2019)·8 citations
9. 09*

   Dirac and Majorana neutrino signatures of primordial black holes

   Cecilia Lunardini🇺🇸 · Yuber F. Perez-Gonzalez🇺🇸

   We study Primordial Black Holes (PBHs) as sources of massive neutrinos via Hawking radiation. Under the hypothesis that black holes emit neutrino mass eigenstates, we describe quantitatively how the PBH evolution and lifetime is affected by the mass and fermionic -- Dirac or Majorana -- nature of neutrinos. In the case of Dirac neutrinos, PBHs radiate right-handed and left-handed neutrinos in equal amounts, thus possibly increasing the effective number of neutrino species, $N_{\mathrm{eff}}$. Assuming an initially monochromatic PBH mass spectrum, with the initial mass $M_i$ related to the particle horizon mass, and considering the current constraint on $N_{\mathrm{eff}}$, we derive a bound on the initial PBH fraction ${\beta }^{\prime }$ in the interval $4.3\times 10^7\mathrm{g}\lesssim M_i\lesssim 10^9$ g. Future measurements of $N_{\mathrm{eff}}$ may be able to constraint the initial fraction for black hole masses as low as 1 g. If an excess in $N_{\mathrm{eff}}$ is found, PBHs with Dirac neutrinos could provide a minimal explanation of it. For example, for $10^7\mathrm{g}\lesssim M_i\lesssim 10^9$ g and ${\beta }^{\prime }\gtrsim 10^{-13}$, an excess radiation at the level of $0.2\lesssim \Delta N_{\mathrm{eff}}\lesssim 0.37$ is produced, which can alleviate the tension of the Hubble parameter measurements. Finally, we obtain the diffuse flux of right-helical neutrinos from PBHs at the Earth, and show that their detection in a PTOLEMY-like detector (using neutrino capture on tritium) would be difficult.

   hep-phastro-ph.COJCAP(2020)·99 citations
10. 10*

    A modular $A_4$ symmetry realization of two-zero textures of the Majorana neutrino mass matrix

    Di Zhang🇨🇳

    We show how to realize two-zero textures of the Majorana neutrino mass matrix $M_{\nu }$ based on modular $A_4$ invariant models without flavons. In these models, all matter fields are assigned to three inequivalent singlets, $1$, $1^{\prime }$ and $1^{\prime \prime }$, of the finite modular group ${\Gamma }_3\simeq A_4$. Considering tensor products of the $A_4$ group, it is easy to make the charged lepton mass matrix $M_{\ell }$ diagonal. Since not all modular forms of a specific weight and level 3 can be arranged into three inequivalent singlets of $A_4$ simultaneously, we can always make some entries in $M_{\nu }$ vanish by properly assigning the representations and modular weights for the matter fields. We consider two cases where neutrino masses originate from the Weinberg operator and the type-I seesaw mechanism, respectively. For the former case, all seven viable two-zero textures of $M_{\nu }$ (${\mathbf{A}}_{1,2}$, ${\mathbf{B}}_{1,2,3,4}$ and $\mathbf{C}$) can be realized successfully. For the latter case, only five of them (namely ${\mathbf{A}}_{1,2}$, ${\mathbf{B}}_{3,4}$ and $\mathbf{C}$) can be achieved due to the intrinsic structure of the right-handed neutrino mass matrix $M_{\mathrm{R}}$ in our assumption for simplicity.

    hep-phNPB(2020)·130 citations
11. 11*

    LHC bounds on coloured scalars

    Víctor Miralles🇪🇸 · Antonio Pich🇪🇸

    We analyze the constraints on coloured scalar bosons imposed by the current LHC data at $\sqrt{s}=13$ TeV. Specifically, we consider an additional electroweak doublet of colour-octet scalars, satisfying the principle of Minimal Flavour Violation in order to fulfill the stringent experimental limits on flavour-changing neutral currents. We demonstrate that coloured scalars with masses below 800 GeV are already excluded, provided they are not fermiophobic.

    hep-phPRD(2019)·30 citations
12. 12*

    Hyperfine structure of P states in muonic ions of lithium, beryllium and boron

    A.E. Dorokhov🇷🇺 · A.P. Martynenko🇷🇺 · F.A. Martynenko🇷🇺 · O.S. Sukhorukova🇷🇺

    We calculate hyperfine structure intervals $\Delta E^{hfs}(2P_{1/2})$ and $\Delta E^{hfs}(2P_{3/2})$ for P-states in muonic ions of lithium, beryllium and boron. To construct the particle interaction operator in momentum space we use the tensor method of projection operators on states with definite quantum numbers of total atomic momentum F and total muon momentum j. We take into account vacuum polarization, relativistic, quadruple and structure corrections of orders ${\alpha }^4$, ${\alpha }^5$ and ${\alpha }^6$. The obtained numerical values of hyperfine splittings can be used for a comparison with future experimental data of the CREMA collaboration.

    hep-phphysics.atom-phPRA(2019)·5 citations
13. 13*

    Top-Higgs Associated Production involving {\boldmath $A^0,H^0$} with Mass at 300 GeV

    George W.-S. Hou🇹🇼

    We advocate two Higgs doublet model without $Z_2$ symmetry, and focus on the extra top Yukawa couplings ${\rho }_{tt}$ and ${\rho }_{tc}$. We show that $A^0$ and $H^0$ bosons are still allowed at 300 GeV mass, where $cg\to t{A}^0$, $t{H}^0$ can lead to $tt\bar{c}$ same-sign top, or top-assisted di-Higgs $t{h}^0{h}^0$ signatures, resp. As bonus material, we explore the constraint provided by current 4-top search, but advocate direct search for triple-top generated by $cg\to t{H}^0/A^0\to tt\bar{t}$ for $H^0,A^0$ above $t\bar{t}$ threshold, and offer some insight on the mild but intriguing "excess" found by CMS in $gg\to A^0\to t\bar{t}$ at 400 GeV.

    hep-phhep-exPoS(2020)·2 citations
14. 14*

    Impact of Higgs physics on the parameter space of the $\mu \nu$SSM

    Essodjolo Kpatcha🇪🇸 · Daniel E. López-Fogliani🇦🇷 · Carlos Muñoz🇪🇸 · Roberto Ruiz de Austri🇪🇸

    Given the increasing number of experimental data, together with the precise measurement of the properties of the Higgs boson at the LHC, the parameter space of supersymmetric models starts to be constrained. We carry out a detailed analysis of this issue in the framework of the $\mu \nu$SSM. In this model, three families of right-handed neutrino superfields are present in order to solve the $\mu$ problem and simultaneously reproduce neutrino physics. The new couplings and sneutrino vacuum expectation values in the $\mu \nu$SSM induce new mixing of states, and, in particular, the three right sneutrinos can be substantially mixed with the neutral Higgses. After diagonalization, the masses of the corresponding three singlet-like eigenstates can be smaller or larger than the mass of the Higgs, or even degenerated with it. We analyze whether these situations are still compatible with the experimental results. To address it we scan the parameter space of the Higgs sector of the model. In particular, we sample the $\mu \nu$SSM using a powerful likelihood data-driven method, paying special attention to satisfy the constraints coming from Higgs sector measurements/limits (using HiggsBounds and HiggsSignals), as well as a class of flavor observables such as $B$ and $\mu$ decays, while muon $g-2$ is briefly discussed. We find that large regions of the parameter space of the $\mu \nu$SSM are viable, containing an interesting phenomenology that could be probed at the LHC.

    hep-phhep-exEPJC(2020)·20 citations
15. 15*

    Cornering Higgsino: Use of Soft Displaced Track

    Hajime Fukuda🇺🇸 · Natsumi Nagata🇯🇵 · Hideyuki Oide🇯🇵 · Hidetoshi Otono🇯🇵 · Satoshi Shirai🇯🇵

    Higgsino has been intensively searched for in the LHC experiments in recent years. Currently, there is an uncharted region beyond the LEP Higgsino mass limit where the mass splitting between the neutral and charged Higgsinos is around $0.3$-$1$ GEV, which is unexplored by either the soft di-lepton or disappearing track searches. This region is, however, of great importance from a phenomenological point of view, as many supersymmetric models predict such a mass spectrum. In this letter, we propose a possibility of filling this gap by using a soft micro-displaced track on top of the mono-jet event selection, which allows us to discriminate a signature of the charged Higgsino decay from the Standard Model background. It is found that this new strategy is potentially sensitive to a Higgsino mass of $\lesssim 180$ $(250)$ GeV at the LHC Run 2 (HL-LHC) for a charged-neutral mass splitting of $\simeq 0.5$ GeV.

    hep-phhep-exPRL(2020)·45 citations
16. 16*

    Baryogenesis from a dark first-order phase transition

    Eleanor Hall🇺🇸 · Thomas Konstandin🇩🇪 · Robert McGehee🇺🇸 · Hitoshi Murayama🇺🇸 · Géraldine Servant🇩🇪

    We present a very minimal model for baryogenesis by a dark first-order phase transition. It employs a new dark $SU(2{)}_D$ gauge group with two doublet Higgs bosons, two lepton doublets, and two singlets. The singlets act as a neutrino portal that transfer the generated asymmetry to the Standard Model. The model predicts $\Delta N_{\text{eff}}=0.09-0.13$ detectable by future experiments as well as possible signals from exotic decays of the Higgs and $Z$ bosons and stochastic gravitational waves.

    hep-phastro-ph.COJHEP(2020)·103 citations
17. 17*

    Neutrino-nucleus cross sections for W-boson and trident production

    Bei Zhou🇺🇸 · John F. Beacom🇺🇸

    The physics of neutrino-nucleus cross sections is a critical probe of the Standard Model and beyond. A precise understanding is also needed to accurately deduce astrophysical neutrino spectra. At energies above $\sim 5$ GeV, the cross section is dominated by deep inelastic scattering, mediated by weak bosons. In addition, there are subdominant processes where the hadronic coupling is through virtual photons, ${\gamma }^{\ast }$: (on-shell) $W$-boson production (e.g., where the underlying interaction is ${\nu }_{\ell }+{\gamma }^{\ast }\to {\ell }^{-}+W^{+}$) and trident production (e.g., where it is $\nu +{\gamma }^{\ast }\to \nu +{\ell }_1^{-}+{\ell }_2^{+}$). These processes become increasingly relevant at TeV--PeV energies. We undertake the first systematic approach to these processes (and those with hadronic couplings through virtual $W$ and $Z$ bosons), treating them together, avoiding common approximations, considering all neutrino flavors and final states, and covering the energy range $10$--$10^8$ GeV. In particular, we present the first complete calculation of $W$-boson production and the first calculation of trident production at TeV--PeV energies. When we use the same assumptions as in prior work, we recover all of their major results. In a companion paper, we show that these processes should be taken into account for IceCube-Gen2.

    hep-phastro-ph.HEnucl-thPRD(2020)·71 citations
18. 18*

    Multi-Channel Direct Detection of Light Dark Matter: Theoretical Framework

    Tanner Trickle🇺🇸 · Zhengkang Zhang🇺🇸 · Kathryn M. Zurek🇺🇸 · Katherine Inzani🇺🇸 · Sinéad M. Griffin🇺🇸

    We present a unified theoretical framework for computing spin-independent direct detection rates via various channels relevant for sub-GeV dark matter -- nuclear recoils, electron transitions and single phonon excitations. Despite the very different physics involved, in each case the rate factorizes into the particle-level matrix element squared, and an integral over a target material- and channel-specific dynamic structure factor. We show how the dynamic structure factor can be derived in all three cases following the same procedure, and extend previous results in the literature in several aspects. For electron transitions, we incorporate directional dependence and point out potential daily modulation signals in anisotropic target materials. For single phonon excitations, we present a new derivation of the rate formula from first principles for generic spin-independent couplings, and include the first calculation of phonon excitation through electron couplings. We also discuss the interplay between single phonon excitations and nuclear recoils, and clarify the role of Umklapp processes, which can dominate the single phonon production rate for dark matter heavier than an MeV. Our results highlight the complementarity between various search channels in probing different kinematic regimes of dark matter scattering, and provide a common reference to connect dark matter theories with ongoing and future direct detection experiments.

    hep-phJHEP(2020)·157 citations
19. 19*

    Searching for scalar dark matter with compact mechanical resonators

    Jack Manley🇺🇸 · Russell Stump🇺🇸 · Dalziel Wilson🇺🇸 · Daniel Grin🇺🇸 · Swati Singh🇺🇸

    We explore the viability of laboratory-scale mechanical resonators as detectors for ultralight scalar dark matter. The signal we investigate is an atomic strain due to modulation of the fine structure constant and the lepton mass at the Compton frequency of dark matter particles. The resulting stress can drive an elastic body with acoustic breathing modes, producing displacements that are accessible with opto- or electromechanical readout techniques. To address the unknown mass of dark matter particles (which determines their Compton frequency), we consider various resonator designs operating at kHz to MHz frequencies, corresponding to $10^{-12}-10^{-5}$ eV particle mass. Current resonant-mass gravitational wave detectors that have been repurposed as dark matter detectors weigh $\sim 10^3$ kg. We find that a large unexplored parameter space can be accessed with ultra-high-$Q$, cryogenically-cooled, cm-scale mechanical resonators possessing $\sim 10^7$ times smaller mass.

    ↳ astro-ph.IMhep-phquant-phPRL(2020)·65 citations
20. 20*

    Anisotropic flow of charged and identified hadrons at FAIR energies and its dependence on the nuclear equation of state

    Sudhir Pandurang Rode🇮🇳 · Partha Pratim Bhaduri🇮🇳 · Ankhi Roy🇮🇳

    In this article, we examine the equation of state (EoS) dependence of the anisotropic flow parameters ($v_1$, $v_2$ and $v_4$) of charged and identified hadrons, as a function of transverse momentum ($p_{\mathrm{T}}$), rapidity ($y_{c.m.}$) and the incident beam energy (${\mathrm{E}}_{\mathrm{Lab}}$) in mid-central Au + Au collisions in the energy range ${\mathrm{E}}_{\mathrm{Lab}}=6-25$ A GeV. Simulations are carried out by employing different variants of the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model, namely the pure transport (cascade) mode and the hybrid mode. In the hybrid mode, transport calculations are coupled with the ideal hydrodynamical evolution. Within the hydrodynamic scenario, two different equations of state (EoS) viz. Hadron gas and Chiral + deconfinement EoS have been employed separately to possibly mimic the hadronic and partonic scenarios, respectively. It is observed that the flow parameters are sensitive to the onset of hydrodynamic expansion of the fireball in comparison to the pure transport approach. The results would be useful as predictions for the upcoming low energy experiments at Facility for Antiproton and Ion Research (FAIR) and Nuclotron-based Ion Collider fAcility (NICA).

    ↳ nucl-thhep-phEPJA(2019)·5 citations
21. 21*

    Glueball scattering cross section in lattice SU(2) Yang-Mills theory

    Nodoka Yamanaka🇯🇵 · Hideaki Iida🇯🇵 · Atsushi Nakamura🇷🇺 · Masayuki Wakayama🇰🇷

    We calculate the scattering cross section between two $0^{++}$ glueballs in $SU(2)$ Yang-Mills theory on lattice at $\beta =2.1,2.2,2.3,2.4$, and 2.5 using the indirect (HAL QCD) method. We employ the cluster-decomposition error reduction technique and use all space-time symmetries to improve the signal. In the use of the HAL QCD method, the centrifugal force was subtracted to remove the systematic effect due to nonzero angular momenta of lattice discretization. From the extracted interglueball potential we determine the low energy glueball effective theory by matching with the one-glueball exchange process. We then calculate the scattering phase shift, and derive the relation between the interglueball cross section and the scale parameter $\Lambda$ as ${\sigma }_{\varphi \varphi }=(2-51){\Lambda }^{-2}$ (stat.+sys.). From the observational constraints of galactic collisions, we obtain the lower bound of the scale parameter, as $\Lambda >60$ MeV. We also discuss the naturalness of the Yang-Mills theory as the theory explaining dark matter.

    ↳ hep-latastro-ph.COhep-phhep-thPRD(2020)·55 citations
22. 22*

    IR dynamics and entanglement entropy

    Theodore N Tomaras🇬🇷 · Nicolaos Toumbas🇨🇾

    We consider scattering of Faddeev-Kulish electrons in QED and study the entanglement between the hard and soft particles in the final state at the perturbative level. The soft photon spectrum naturally splits into two parts: i) soft photons with energies less than a characteristic infrared scale $E_d$ present in the clouds accompanying the asymptotic charged particles, and ii) sufficiently low energy photons with energies greater than $E_d$, comprising the soft part of the emitted radiation. We construct the density matrix associated with tracing over the radiative soft photons and calculate the entanglement entropy perturbatively. We find that the entanglement entropy is free of any infrared divergences order by order in perturbation theory. On the other hand infrared divergences in the perturbative expansion for the entanglement entropy appear upon tracing over the entire spectrum of soft photons, including those in the clouds. To leading order the entanglement entropy is set by the square of the Fock basis amplitude for real single soft photon emission, which leads to a logarithmic infrared divergence when integrated over the photon momentum. We argue that the infrared divergences in the entanglement entropy (per particle flux per unit time) in this latter case persist to all orders in perturbation theory in the infinite volume limit.

    ↳ hep-thgr-qchep-phPRD(2020)·28 citations
23. 23*

    Two-colour QCD phases and the topology at low temperature and high density

    Kei Iida🇯🇵 · Etsuko Itou🇯🇵 · Tong-Gyu Lee🇯🇵

    We delineate equilibrium phase structure and topological charge distribution of dense two-colour QCD at low temperature by using a lattice simulation with two-flavour Wilson fermions that has a chemical potential $\mu$ and a diquark source $j$ incorporated. We systematically measure the diquark condensate, the Polyakov loop, the quark number density and the chiral condensate with improved accuracy and $j\to 0$ extrapolation over earlier publications; the known qualitative features of the low temperature phase diagram, which is composed of the hadronic, Bose-Einstein condensed (BEC) and BCS phases, are reproduced. In addition, we newly find that around the boundary between the hadronic and BEC phases, nonzero quark number density occurs even in the hadronic phase in contrast to the prediction of the chiral perturbation theory (ChPT), while the diquark condensate approaches zero in a manner that is consistent with the ChPT prediction. At the highest $\mu$, which is of order the inverse of the lattice spacing, all the above observables change drastically, which implies a lattice artifact. Finally, at temperature of order $0.45T_c$, where $T_c$ is the chiral transition temperature at zero chemical potential, the topological susceptibility is calculated from a gradient-flow method and found to be almost constant for all the values of $\mu$ ranging from the hadronic to BCS phase. This is a contrast to the case of $0.89T_c$ in which the topological susceptibility becomes small as the hadronic phase changes into the quark-gluon plasma phase.

    ↳ hep-lathep-phnucl-thJHEP(2020)·58 citations
24. 24*

    Material matter effects in gravitational UV/IR mixing

    Joseph Bramante🇨🇦 · Elizabeth Gould🇨🇦

    We propose a matter effect for the gravitational ultraviolet/infrared (UV/IR) mixing solution to the cosmological constant problem. Previously, the gravitational UV/IR mixing model implied a non-standard equation of state for dark energy, contradicting observation. In contrast, matter effect gravitational UV/IR mixing accommodates a standard $\Lambda$CDM cosmology with constant dark energy. Notably, there are new density-dependent predictions for futuristically precise measurements of fundamental parameters, like the magnetic moments of the muon and electron.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2020)·14 citations
25. 25*

    Towards grounding nuclear physics in QCD

    Christian Drischler🇺🇸 · Wick Haxton🇺🇸 · Kenneth McElvain🇺🇸 · Emanuele Mereghetti🇺🇸 · Amy Nicholson🇺🇸 · Pavlos Vranas🇺🇸 · André Walker-Loud🇺🇸

    Exascale computing could soon enable a predictive theory of nuclear structure and reactions rooted in the Standard Model, with quantifiable and systematically improvable uncertainties. Such a predictive theory will help exploit experiments that use nucleons and nuclei as laboratories for testing the Standard Model and its limitations. Examples include direct dark matter detection, neutrinoless double beta decay, and searches for permanent electric dipole moments of the neutron and atoms. It will also help connect QCD to the properties of cold neutron stars and hot supernova cores. We discuss how a quantitative bridge between QCD and the properties of nuclei and nuclear matter will require a synthesis of lattice QCD (especially as applied to two- and three-nucleon interactions), effective field theory, and ab initio methods for solving the nuclear many-body problem. While there are significant challenges that must be addressed in developing this triad of theoretical tools, the rapid advance of computing is accelerating progress. In particular, we focus this review on the anticipated advances from lattice QCD and how these advances will impact few-body effective theories of nuclear physics by providing critical input, such as constraints on unknown low-energy constants of the effective (field) theories. We also review particular challenges that must be overcome for the successful application of lattice QCD for low-energy nuclear physics. We describe progress in developing few-body effective (field) theories of nuclear physics, with an emphasis on HOBET, a non-relativistic effective theory of nuclear physics, which is less common in the literature. We use the examples of neutrinoless double beta decay and the nuclear-matter equation of state to illustrate how the coupling of lattice QCD to effective theory might impact our understanding of symmetries and exotic astrophysical environments.

    ↳ nucl-thhep-exhep-lathep-ph+1PPNP(2021)·121 citations
26. 26*

    Coherent deeply virtual Compton scattering off He nuclei

    Sara Fucini🇮🇹 · Matteo Rinaldi🇮🇹 · Sergio Scopetta🇮🇹

    The status of realistic calculations of nuclear generalized parton distributions, entering the theoretical description of coherent deeply virtual Compton scattering off nuclei, is reviewed for trinucleons and for ${}^4$He, also in view of forthcoming measurements at the Jefferson Laboratory and at the future Electron Ion Collider.

    ↳ nucl-thhep-ph1 citation
27. 27*

    Centrality selection effect on higher-order cumulants of net-proton multiplicity distributions in relativistic heavy-ion collisions

    Arghya Chatterjee🇨🇳 · Yu Zhang🇨🇳 · Jingdong Zeng🇨🇳 · Nihar Ranjan Sahoo🇨🇳 · Xiaofeng Luo🇨🇳

    We studied the centrality selection effect on cumulants (up to fourth order) and the cumulants ratios of net-proton multiplicity distributions in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 7.7, 19.6 and 200 GeV from UrQMD model. The net-proton cumulants are calculated with collision centralities by using charged particle multiplicity from different pesudorapidity ($\eta$) region. By comparing the results from various collision centralities, we found that the autocorrelation effects are not significant in the results with collision centralities "refmult-3" and "refmult-2", which are using mid-rapidity charged particles but excluding (anti-)protons and analysis region, respectively. Furthermore, due to the contributions of spectator protons, we observed poor centrality resolution when using charged particles at forward $\eta$ region at low energies. This work can serve as a baseline for centrality selection of future fluctuations analysis in relativistic heavy-ion collisions.

    ↳ nucl-exhep-phnucl-thPRC(2020)·28 citations
28. 28*

    Novel pre-burst stage of gamma-ray bursts from machine learning

    Yingtian Chen🇹🇼 · Bo-Qiang Ma🇨🇳

    Gamma-ray bursts (GRBs), as extremely energetic explosions in the universe, are widely believed to consist of two stages: the prompt phase and the subsequent afterglow. Recent studies indicate that some high-energy photons are emitted earlier at source than the prompt phase. Due to the light speed variation, these high-energy photons travel slowly than the low-energy photons, so that they are observed after the prompt low-energy photons at the detector. Based on the data from the Fermi Gamma-ray Space Telescope (FGST), we analyse the photon distribution before the prompt emission in detail and propose the existence of a hitherto unknown pre-burst stage of GRBs by adopting a classification method of machine learning. Analysis on the photons automatically selected by machine learning also produce a light speed variation at $E_{\mathrm{LV}}=3.55\times 10^{17}\mathrm{GeV}$.

    ↳ astro-ph.HEgr-qchep-phJHEAp(2021)·19 citations
29. 29*

    Measuring the net circular polarization of the stochastic gravitational wave background with interferometers

    Valerie Domcke🇩🇪 · Juan Garcia-Bellido🇪🇸 · Marco Peloso🇮🇹 · Mauro Pieroni🇪🇸 · Angelo Ricciardone🇮🇹 · Lorenzo Sorbo🇺🇸 · Gianmassimo Tasinato🇬🇧

    Parity violating interactions in the early Universe can source a stochastic gravitational wave background (SGWB) with a net circular polarization. In this paper, we study possible ways to search for circular polarization of the SGWB with interferometers. Planar detectors are unable to measure the net circular polarization of an isotropic SGWB. We discuss the possibility of using the dipolar anisotropy kinematically induced by the motion of the solar system with respect to the cosmic reference frame to measure the net circular polarization of the SGWB with planar detectors. We apply this approach to LISA, re-assessing previous analyses by means of a more detailed computation and using the most recent instrument specifications, and to the Einstein Telescope (ET), estimating for the first time its sensitivity to circular polarization. We find that both LISA and ET, despite operating at different frequencies, could detect net circular polarization with a signal-to-noise ratio of order one in a SGWB with amplitude $h^2{\Omega }_{\text{GW}}\simeq 10^{-11}$. We also investigate the case of a network of ground based detectors. We present fully analytical, covariant formulas for the detector overlap functions in the presence of circular polarization. Our formulas do not rely on particular choices of reference frame, and can be applied to interferometers with arbitrary angles among their arms.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2020)·87 citations
30. 30*

    Entropy Counting from Schwarzschild/CFT and Soft Hair

    Artem Averin🇩🇪

    We revisit Carlip's approach to entropy counting. This analysis reemerged in a recently obtained Schwarzschild/CFT-correspondence as Sugawara-construction of a 2D stress-tensor. Here, for the example of a Schwarzschild black hole, we show how to single out diffeomorphisms forming in contrast to Carlip's analysis the full 2D local conformal algebra. We provide arguments, why their Hamiltonian generators are expected to be the symmetry generators of a possible conformal field theory describing the part of phase space responsible for black hole microstates. Then, we can infer central charges and temperatures of this CFT by inspecting the algebra of these Hamiltonian generators. Using this data in the Cardy-formula, precise agreement with the Bekenstein-Hawking entropy is found. Alternatively, we obtain the same CFT temperatures by thermodynamic considerations. Altogether, this suggests that the Hamiltonian generators need no corrections through possible non-canonical counterterms. We comment on the related recent work by Haco, Hawking, Perry, Strominger.

    ↳ hep-thgr-qchep-phPRD(2020)·15 citations
31. 31*

    Three generations, two unbroken gauge symmetries, and one eight-dimensional algebra

    N. Furey🇬🇧

    A considerable amount of the standard model's three-generation structure can be realised from just the $8\mathbb{C}$-dimensional algebra of the complex octonions. Indeed, it is a little-known fact that the complex octonions can generate on their own a $64\mathbb{C}$-dimensional space. Here we identify an $su(3)\oplus u(1)$ action which splits this $64\mathbb{C}$-dimensional space into complexified generators of $SU(3)$, together with 48 states. These 48 states exhibit the behaviour of exactly three generations of quarks and leptons under the standard model's two unbroken gauge symmetries. This article builds on a previous one, [1], by incorporating electric charge. Finally, we close this discussion by outlining a proposal for how the standard model's full set of states might be identified within the left action maps of $\mathbb{R}\otimes \mathbb{C}\otimes \mathbb{H}\otimes \mathbb{O}$ (the Clifford algebra $\mathbb{C}l(8)$). Our aim is to include not only the standard model's three generations of quarks and leptons, but also its gauge bosons.

    ↳ hep-thhep-phmath-phmath.MPPLB(2018)·82 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.