Mon·Sep 21, 2020Monday·September 21, 2020

1. 01*

   A Clockwork Solution to the Doublet-Triplet Splitting Problem

   Gero von Gersdorff🇧🇷

   Maybe the biggest puzzle in grand unified theories (GUTs) is the apparent large splitting of the doublet and triplet Higgs masses. We suggest a novel mechanism to solve this puzzle, which relies on the clockwork mechanism to generate large hierarchies from order-one numbers. The tension between gauge coupling unification and proton lifetime from minimal SU(5) GUTs is also removed in this scenario, and the theory remains perturbative until the Planck scale.

   hep-phPLB(2021)·3 citations
2. 02*

   On the influence of a Chern-Simons term in the dynamical fermion masses in Reduced or Pseudo QED

   Juan Angel Casimiro Olivares🇲🇽 · Luis Albino🇧🇷 · Ana Julia Mizher🇧🇷 · Alfredo Raya🇲🇽

   Mixed dimensional theories have been used to describe condensed matter systems where fermions are constrained to a plane while the gauge fields they interact with remain four-dimensional. Here we investigate dynamical breaking of chiral symmetry in the framework of a mixed-dimensional theory that has been successful in describing graphene and other planar Dirac materials and has been dubbed as Pseudo or Reduced Quantum Electrodynamics. We explore the interplay between the gauge and fermion sector when a Chern-Simons term is considered and, by exploring the tensor structure of the fermion self energy, we show that the radiative corrections may induce both, a Dirac and a Haldane mass term. Furthermore, by solving the corresponding Schwinger-Dyson equation in a suitable truncation, we explore non-perturbatively the dynamical generation of fermion masses for different values of the electromagnetic coupling and the Chern-Simons coefficient. We also show that for definite parameter values, the contributions from each chirality cancel out and the chiral symmetry may be restored. Possible implications of this result for physical systems, in particular on what concerns the chiral magnetic effect, are discussed.

   hep-phhep-thPRD(2020)·12 citations
3. 03*

   Physics potentials with a combined sensitivity of T2K-II, NO$\nu$A extension and JUNO

   S. Cao🇻🇳 · A. Nath🇮🇳 · T. V. Ngoc🇻🇳 · P. T. Quyen🇻🇳 · N. T. Hong Van🇻🇳 · Ng. K. Francis🇮🇳

   Leptonic \textit{CP} violation search, neutrino mass hierarchy determination, and the precision measurement of oscillation parameters for a unitary test of the leptonic mixing matrix are among the major targets of the ongoing and future neutrino oscillation experiments. The work explores the physics reach for these targets by around 2027, when the third generation of the neutrino experiments starts operation, with a combined sensitivity of three experiments: T2K-II, NO$\nu$A extension, and JUNO. It is shown that a joint analysis of these three experiments can conclusively determine the neutrino mass hierarchy. Also, at certain values of \emph{true} \dcp, it provides closely around a $5\sigma$ confidence level (C.L.) to exclude \textit{CP}-conserving values and more than a $50\%$ fractional region of \emph{true} ${\delta }_{\text{CP}}$ values can be explored with a statistic significance of at least a $3\sigma$ C.L. Besides, the joint analysis can provide unprecedented precision measurements of the atmospheric neutrino oscillation parameters and a great offer to solve the ${\theta }_{23}$ octant degeneracy in the case of nonmaximal mixing.

   hep-phhep-exPRD(2021)·22 citations
4. 04*

   Renormalization Scheme and Mass Scale Independence

   F. A. Chishtie🇨🇦 · D.G.C. McKeon🇨🇦

   We demonstrate that in the mass independent renormalization scheme. the renormalization group equations associated with the unphysical parameters that characterize the renormalization scheme and the mass scale leads to summation that results in a cancellation between the implicit and explicit dependence on these parameters. The resulting perturbative expansion is consequently independent of these arbitrary parameters. We illustrate this by considering R, the cross section for e+e- -> hadrons.

   hep-phCan.J.Phys.(2021)·1 citation
5. 05*

   The $a_0(980)$ in the single Cabibbo-suppressed process ${\Lambda }_c\to {\pi }^0\eta p$

   Xue-Chao Feng🇨🇳 · Le-Le Wei🇨🇳 · Man-Yu Duan🇨🇳 · En Wang🇨🇳 · De-Min Li🇨🇳

   In this work, we have investigated the Cabibbo-suppressed process ${\Lambda }_c\to {\pi }^0\eta p$, by taking into account the intermediate scalar state $a_0(980)$, which could be dynamically generated from the $S$-wave pseudoscalar-pseudoscalar interaction within the chiral unitary approach. We have calculated the ${\pi }^0\eta$ invariant mass distribution, and found that there is a significant structure associated to the $a_0(980)$. We have also roughly estimated the branching fraction $\mathcal{B}({\Lambda }_c\to {\pi }^0\eta p)\sim 10^{-4}$. We encourage our experimental colleagues to measure the process ${\Lambda }_c\to {\pi }^0\eta p$ for searching for the state $a_0(980)$ in this reaction.

   hep-phPLB(2023)·27 citations
6. 06*

   Electroweak phase transition confronted with dark matter detection constraints

   Cheng-Wei Chiang🇹🇼 · Da Huang🇨🇳 · Bo-Qiang Lu🇹🇼

   We study the type-II first-order electroweak phase transition and dark matter (DM) phenomenology in both real and complex singlet extensions of SM. In the real singlet extension with a ${\mathbb{Z}}_2$ symmetry, we show that the parameter regions favored by the phase transition suffer from strong constraints from DM direct detection so that only a negligible fraction ($f_X\sim 10^{-4}-10^{-5}$) of DM composed of the real singlet scalar can survive the LUX and XENON1T constraints. In the complex singlet $S$ case, we impose a $CP$ symmetry $S\to S^{\ast }$ to the scalar potential. The real component of $S$ can mix with SM Higgs boson while the imaginary component becomes a DM candidate due to the protection of the $CP$ symmetry. By taking into account the current experimental constraints of invisible Higgs decays, Higgs signal strength measurements, and dark matter detections, we find that there exists a large parameter space for the type-II electroweak phase transition to occur while explaining all of the dark matter relic density. We identify a subset of parameter space that is promising for future experiments, including the di-Higgs and Higgs signal strength measurements at the HL-LHC and the dark matter direct detection in the XENONnT project.

   hep-phhep-exJCAP(2021)·16 citations
7. 07*

   Completing $1/m_b^3$ corrections to non-leptonic bottom-to-up-quark decays

   Daniel Moreno Torres🇩🇪

   We compute the contributions of dimension six two-quark operators to the non-leptonic decay width of heavy hadrons due to the flavor changing bottom-to-up-quark transition in the heavy quark expansion. Analytical expressions for the Darwin term ${\rho }_D$ and the spin-orbit term ${\rho }_{\mathrm{LS}}$ are obtained with leading order accuracy.

   hep-phJHEP(2021)·25 citations
8. 08*

   Discovering supernova-produced dark matter with directional detectors

   Elisabetta Baracchini🇮🇹 · William DeRocco🇺🇸 · Giorgio Dho🇮🇹

   Supernovae can produce vast fluxes of new particles with masses on the MeV scale, a mass scale of interest for models of light dark matter. When these new particles become diffusively trapped within the supernova, the escaping flux will emerge semirelativistic with an order-one spread in velocities. As a result, overlapping emissions from Galactic supernovae will produce an overall flux of these particles at Earth that is approximately constant in time. However, this flux is highly anisotropic and is steeply peaked towards the Galactic center. This is in contrast with the cosmological abundance of a WIMP-like dark matter which, due to the rotation of the Galaxy, appears to come from the direction of the Cygnus constellation. In this paper, we demonstrate the need for a directional detector to efficiently discriminate between a signal from a cold cosmological abundance of GeV-scale WIMPs and a signal from a hot population of supernova-produced MeV-scale dark matter.

   hep-phhep-exPRD(2020)·13 citations
9. 09*

   Double soft current at one-loop in QCD

   Yu Jiao Zhu🇨🇳

   We investigate the soft behavior of QCD amplitudes involving multiple Wilson lines and derive compact analytic expressions for double soft gluon and double soft quark emissions at one loop. The color correlations of the soft current exhibit a predominantly dipole structure, coupling to two hard legs at a time, apart from an abelian contribution that factorizes into products of one-loop and tree-level single soft currents, which may involve up to three hard legs. The kinematic dependence of the one-loop soft currents is expressed in terms of polylogarithmic functions, with explicit results presented for time-like kinematics. We further discuss the analytic continuation to other kinematic configurations and identify non-trivial crossing effects when continuing into incoming states. The squared amplitude is found to be invariant under crossing, which implies that the fully differential soft function and in particular the TMD soft function, remains universal up to three loops.

   hep-phJHEP(2026)·42 citations
10. 10*

    Spheres To Jets: Tuning Event Shapes with 5d Simplified Models

    Cari Cesarotti🇺🇸 · Matthew Reece🇺🇸 · Matthew J. Strassler🇺🇸

    Hidden sectors could give rise to a wide variety of events at the LHC. Confining hidden sectors are known to engender events with a small number of jets when they are weakly-coupled at high energies, and quasi-spherical soft unclustered energy patterns (SUEPs) when they are very strongly-coupled (large 't Hooft coupling) at high energies. The intermediate regime is murky, and could give rise to signals hiding from existing search strategies. While the intermediate coupling regime is not calculable, it is possible to pursue a phenomenological approach in which one creates signals that are intermediate between spherical and jetty. We propose a strategy for generating events of this type using simplified models in extra dimensions. The degree to which the event looks spherical is related to the number of decays produced near kinematic threshold. We provide an analytic understanding of how this is determined by parameters of the model. To quantify the shape of events produced with this model, we use a recently proposed observable---event isotropy---which is a better probe of the spherical regime than earlier event shape observables.

    hep-phhep-exJHEP(2021)·29 citations
11. 11*

    Jiamusi pulsar observations: III. Nulling of 20 pulsars

    P. F. Wang🇨🇳 · J. L. Han🇨🇳 · L. Han🇨🇳 · B. Y. Cai🇨🇳 · C. Wang🇹🇼 · T. Wang🇨🇳 · X. Chen🇨🇳 · D. J. Zhou🇨🇳 · Y. Z. Yu🇨🇳 · J. Han🇨🇳 · J. Xu🇺🇸 · X. Y. Gao🇨🇳 and 3 other authors

    Most of pulsar nulling observations were conducted at frequencies lower than 1400~MHz. We aim to understand the nulling behaviors of pulsars at relatively high frequency, and to check if nulling is caused by a global change of pulsar magnetosphere. 20 bright pulsars are observed at 2250~MHz with unprecedented lengths of time by using Jiamusi 66m telescope. Nulling fractions of these pulsars are estimated, and the null and emission states of pulses are identified. Nulling degrees and scales of the emission-null pairs are calculated to describe the distributions of emission and null lengths. Three pulsars, PSRs J0248+6021, J0543+2329 and J1844+00, are found to null for the first time. The details of null-to-emission and emission-to-null transitions within pulse window are first observed for PSR J1509+5531, which is a small probability event. A complete cycle of long nulls for hours is observed for PSR J1709-1640. For most of these pulsars, the K-S tests of nulling degrees and nulling scales reject the hypothesis that null and emission are of random processes at high significance levels. Emission-null sequences of some pulsars exhibit quasi-periodic, low-frequency or featureless modulations, which might be related to different origins. During transitions between emission and null states, pulse intensities have diverse tendencies for variations. Significant correlations are found for nulling fraction, nulling cadence and nulling scales with the energy loss rate of the pulsars. Combined with the nulling fractions reported in literatures for 146 nulling pulsars, we found that statistically large nulling fractions are more tightly related to pulsar period than to characteristic age or energy loss rate.

    ↳ astro-ph.HEhep-phAstron.Astrophys.(2020)·21 citations
12. 12*

    Purely kinetic k-essence description of $c_s^2(w)$ barotropic fluid models

    Dalibor Perkovic🇭🇷 · Hrvoje Stefancic🇭🇷

    Purely kinetic k-essence models have been shown in the literature to be a field theory equivalent of barotropic fluid models of dark energy or dark matter-dark energy unification. In the modeling framework where the speed of sound squared of a barotropic fluid is modeled as a function of its Equation of State parameter, a systematic procedure of obtaining the Lagrangian density of an equivalent purely kinetic k-essence model is presented. As this modeling approach starts from the speed of sound, purely kinetic k-essence models can be constructed for which the speed of sound is in agreement with the observational constraints. Depending on the chosen functional form for the barotropic fluid speed of sound squared, analytically tractable examples of solutions for the purely kinetic k-essence Lagrangian density in parametric and closed form are obtained.

    ↳ astro-ph.COgr-qchep-phPhys.Dark Univ.(2021)·8 citations
13. 13*

    Stochastic inflation and primordial black holes

    Vincent Vennin🇫🇷

    During inflation, vacuum quantum fluctuations are amplified and stretched to astrophysical distances. They give rise to fluctuations in the cosmic microwave background (CMB) temperature and polarisation, and to large-scale structures in our universe. They can also trigger the formation of primordial black holes (PBHs). Such objects could provide the progenitors of the recently detected black-hole mergers, and constitute part or all of the dark matter. Their observation would give invaluable access to parts of the inflationary sector that are unconstrained by the CMB. Since PBHs require large inhomogeneities to form, they are produced in scenarios where quantum fluctuations substantially modify the dynamics of the universe. In this habilitation thesis, this "backreaction" effect is investigated using the stochastic inflation formalism, an effective theory for the long-wavelengths of quantum fields during inflation, which can be described in a classical but stochastic way once the small wavelengths have been integrated out. It describes an inflating background that gets randomly corrected by the vacuum quantum fluctuations as they get stretched to large distances. After a brief review of the stochastic inflation formalism, we explain how it can be combined with standard techniques of cosmological perturbation theory (the $\delta N$ formalism) to provide the full probability density function of curvature perturbations in the presence of non-perturbative quantum diffusion. These results are then applied to PBHs, where we show that quantum diffusion can change the expected abundance by several orders of magnitude. Finally, since inflationary models giving rise to cosmologically relevant PBHs often feature violations of slow roll, the stochastic-$\delta N$ formalism is generalised to non slow-roll dynamics. We conclude by highlighting several research directions that remain to be explored.

    ↳ astro-ph.COgr-qchep-phhep-th56 citations
14. 14*

    Effects of modified theories of gravity on neutrino pair annihilation energy deposition near neutron stars

    Gaetano Lambiase🇮🇹 · Leonardo Mastrototaro🇮🇹

    We study the neutrino pairs annihilation into electron-positron pairs ($\nu +\bar{\nu }\to e^{-}+e^{+}$) near the surface of a neutron star. The analysis is performed in the framework of extended theories of gravity. The latter induce a modification of the minimum photon-sphere radius ($R_{ph}$) and the maximum energy deposition rate near to $R_{ph}$, as compared to ones of General Relativity. These results might lead to an efficient mechanism for generating GRBs.

    ↳ astro-ph.HEgr-qchep-phApJ(2020)·34 citations
15. 15*

    Gravitational instantons and anomalous chiral symmetry breaking

    Yu Hamada🇯🇵 · Jan M. Pawlowski🇩🇪 · Masatoshi Yamada🇩🇪

    We study anomalous chiral symmetry breaking in two-flavour QCD induced by gravitational and QCD-instantons within asymptotically safe gravity within the functional renormalisation group approach. Similarly to QCD-instantons, gravitational ones, associated to a K3-surface connected by a wormhole-like throat in flat spacetime, generate contributions to the 't~Hooft coupling proportional to $\exp (-1/g_N)$ with the dimensionless Newton coupling $g_N$. Hence, in the asymptotically safe gravity scenario with a non-vanishing fixed point coupling $g_N^{\ast }$, the induced 't Hooft coupling is finite at the Planck scale, and its size depends on the chosen UV-completion. Within this scenario the gravitational effects on anomalous $U(1{)}_A$-breaking at the Planck scale may survive at low energy scales. In turn, fermion masses of the order of the Planck scale cannot be present. This constrains the allowed asymptotically safe UV-completion of the Gravity-QCD system. We map-out the parameter regime that is compatible with the existence of light fermions in the low-energy regime.

    ↳ hep-thgr-qchep-phPRD(2021)·24 citations
16. 16*

    $J/\psi$ near $T_c$

    Taesoo Song🇩🇪 · Philipp Gubler🇯🇵 · Juhee Hong🇰🇷 · Su Houng Lee🇰🇷 · Kenji Morita🇯🇵

    We calculate the mass shift and thermal decay width of the $J/\psi$ near the QCD transition temperature $T_c$ by imposing two independent constraints on these variables that can be obtained first by solving the Schrödinger equation and second from the QCD sum rule approach. While the real part of the potential is determined by comparing the QCD sum rule result for charmonium and the D meson to that from the potential model result, the imaginary potential is taken to be proportional to the perturbative form multiplied by a constant factor, which in turn can be determined by applying the two independent constraints. The result shows that the binding energy and the thermal width becomes similar in magnitude at around $T=1.09T_c$, above which the sum rule analysis also becomes unstable, strongly suggesting that the $J/\psi$ will melt slightly above $T_c$.

    ↳ nucl-thhep-lathep-phPLB(2021)·3 citations
17. 17*

    Benchmark of medium-induced radiative energy loss model for heavy-ion collisions

    Iurii Karpenko🇨🇿 · Joerg Aichelin🇫🇷 · Pol Bernard Gossiaux🇫🇷 · Martin Rohrmoser🇵🇱

    We report on a benchmark calculation of the in-medium radiative energy loss of low-virtuality jet partons within the EPOS3-Jet framework. The radiative energy loss is based on an extension of the Gunion-Bertsch matrix element for a massive projectile and a massive radiated gluon. On top of that, the coherence (LPM effect) is implemented by assigning a formation phase to the trial radiated gluons in a fashion similar to the approach in JHEP 07 (2011), 118, by Zapp, Stachel and Wiedemann. In a calculation with a simplified radiation kernel, we reproduce the radiation spectrum reported in the approach above. The radiation spectrum produces the LPM behaviour $dI/d\omega \propto {\omega }^{-1/2}$ up to an energy $\omega ={\omega }_c$, when the formation length of radiated gluons becomes comparable to the size of the medium. Beyond ${\omega }_c$, the radiation spectrum shows a characteristic suppression due to a smaller probability for a gluon to be formed in-medium. Next, we embed the radiative energy loss of low-virtuality jet partons into a more realistic "parton gun" calculation, where a stream of hard partons at high initial energy $E_{\text{ini}}=100$ GeV and initial virtuality $Q^2=E^2$ passes through a box of QGP medium with a constant temperature. At the end of the box evolution, the partons are hadronized using Pythia 8, and the jets are reconstructed with the FASTJET package. We find that the full jet energy loss in such scenario approaches a ballpark value reported by the ALICE collaboration. However, the calculation uses a somewhat larger value of the coupling constant ${\alpha }_s$ to compensate for the missing collisional energy loss of the low-virtuality jet partons.

    ↳ nucl-thhep-exhep-phPoS(2021)·0 citations
18. 18*

    Remarks on relativistic scalar models with chemical potential

    Tomas Brauner🇳🇴

    We discuss selected aspects of classical relativistic scalar field theories with nonzero chemical potential. First, we offer a review of classical field theory at nonzero density within the Lagrangian formalism. The aspects covered include the question of equivalence of descriptions of finite-density states using a chemical potential or time-dependent field configurations, the choice of Hamiltonian whose minimization yields the finite-density equilibrium state, and the issue of breaking of Lorentz invariance. Second, we demonstrate how the low-energy effective field theory for Nambu-Goldstone (NG) modes arising from the spontaneous breakdown of global internal symmetries can be worked out explicitly by integrating out the heavy (Higgs) fields. This makes it possible to analyze the spectrum of NG modes and their interactions without having to deal with mixing of NG and Higgs fields, ubiquitous in the linear-sigma-model description of spontaneous symmetry breaking.

    ↳ hep-thhep-ph2 citations
19. 19*

    High-accuracy calculation of the deuteron charge and quadrupole form factors in chiral effective field theory

    A. A. Filin🇩🇪 · D. Möller🇩🇪 · V. Baru🇩🇪 · E. Epelbaum🇩🇪 · H. Krebs🇩🇪 · P. Reinert🇩🇪

    We present a comprehensive analysis of the deuteron charge and quadrupole form factors based on the latest two-nucleon potentials and charge density operators derived in chiral effective field theory. The single- and two-nucleon contributions to the charge density are expressed in terms of the proton and neutron form factors, for which the most up-to-date empirical parametrizations are employed. By adjusting the fifth-order short-range terms in the two-nucleon charge density operator to reproduce the world data on the momentum-transfer dependence of the deuteron charge and quadrupole form factors, we predict the values of the structure radius and the quadrupole moment of the deuteron: $r_{\mathrm{str}}=1.9729\begin{array}{c}+0.0015\\ -0.0012\end{array}\text{fm},Q_d=0.2854\begin{array}{c}+0.0038\\ -0.0017\end{array}{\text{fm}}^2.$ A comprehensive and systematic analysis of various sources of uncertainty in our predictions is performed. Following the strategy advocated in our recent publication Phys. Rev. Lett. 124, 082501 (2020), we employ the extracted structure radius together with the accurate atomic data for the deuteron-proton mean-square charge radii difference to update the determination of the neutron charge radius, for which we find: $r_n^2=-0.105\begin{array}{c}+0.005\\ -0.006\end{array}{\text{fm}}^2$. Given the observed rapid convergence of the deuteron form factors in the momentum-transfer range of $Q\simeq 1-2.5$ fm${}^{-1}$, we argue that this intermediate-energy domain is particularly sensitive to the details of the nucleon form factors and can be used to test different parametrizations.

    ↳ nucl-thhep-phnucl-exPRC(2021)·62 citations
20. 20*

    Baryon stopping as a relativistic Markov process in phase space

    Johannes Hoelck🇩🇪 · Georg Wolschin🇩🇪

    We reconsider baryon stopping in relativistic heavy-ion collisions in a nonequilibrium-statistical framework. The approach combines earlier formulations based on quantum chromodynamics with a relativistic diffusion model through a suitably derived fluctuation-dissipation relation, thus allowing for a fully time-dependent theory that is consistent with QCD. We use an existing framework for relativistic stochastic processes in spacetime that are Markovian in phase space, and adapt it to derive a Fokker-Planck equation in rapidity space, which is solved numerically. The time evolution of the net-proton distribution function in rapidity space agrees with stopping data from the CERN Super Proton Synchrotron and the BNL Relativistic Heavy Ion Collider.

    ↳ nucl-thhep-phPRResearch(2020)·12 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.