Mon·Dec 27, 2021Monday·December 27, 2021

1. 01*

   Neutrino magnetic and electric dipole moments: From measurements to parameter space

   D. Aristizabal Sierra🇨🇱 · O. G. Miranda🇲🇽 · D. K. Papoulias🇬🇷 · G. Sanchez Garcia🇲🇽

   Searches for neutrino magnetic moments/transitions in low energy neutrino scattering experiments are sensitive to effective couplings which are an intricate function of the Hamiltonian parameters. We study the parameter space dependence of these couplings in the Majorana (transitions) and Dirac (moments) cases, as well as the impact of the current most stringent experimental upper limits on the fundamental parameters. In the Majorana case we find that for reactor, short-baseline and solar neutrinos, CP violation can be understood as a measurement of parameter space vectors misalignments. The presence of nonvanishing CP phases opens a blind spot region where -- regardless of how large the parameters are -- no signal can be observed in either reactor or short-baseline experiments. Identification of these regions requires a combination of different data sets and allows for the determination of those CP phases. We point out that stringent bounds not necessarily imply suppressed Hamiltonian couplings, thus allowing for regions where disparate upper limits can be simultaneously satisfied. In contrast, in the Dirac case stringent experimental upper limits necessarily translate into tight bounds on the fundamental couplings. In terms of parameter space vectors, we provide a straightforward mapping of experimental information into parameter space.

   hep-phhep-exPRD(2022)·38 citations
2. 02*

   Sensitivity studies on the CKM angle $\gamma$ in ${\Lambda }_b^0\to D\Lambda$ decays

   Shunan Zhang🇨🇳 · Yi Jiang🇨🇳 · Zewen Chen🇨🇳 · Wenbin Qian🇨🇳

   The sensitivity of the CKM angle $\gamma$ in ${\Lambda }_b^0\to D\Lambda$ decays has been studied using the decay parameter $\alpha$ as an observable in addition to the decay rate asymmetry. Feasibility studies show that adding this observable improves the sensitivity on $\gamma$ by up to 60\% and makes the decays one of the most promising places to measure angle $\gamma$ and to search for $CP$ violation in $b$-baryon decays.

   hep-phhep-ex9 citations
3. 03*

   Some features of the direct and inverse double Compton effect as applied to astrophysics

   V. Dubrovich🇷🇺 · T. Zalialiutdinov🇷🇺

   In the present paper, we consider the process of inverse double Compton (IDC) scattering in the context of astrophysical applications. It is assumed that the two hard X-ray photons emitted from an astrophysical source are scattered on a free electron and converted into a single soft photon of optical range. Using QED S-matrix formalism for the derivation of a cross-section of direct double Compton (DDC) and assuming detailed balance conditions we give an analytical expression for the cross-section of the IDC process. It is shown that at fixed energies of incident photons the inverse cross-section has no infra-red divergences and its behavior is completely defined by the spectral characteristics of the photon source itself, in particular, by the finite interaction time of radiation with an electron. Thus, even for the direct process, the problem of resolving infrared divergence actually refers to a real physical source of radiation in which photons are never actually plane waves. As a result the physical frequency profile of the scattered radiation for direct as well as inverse double Compton processes is a function of both the intensity and line shape of the incident photon field.

   hep-phastro-ph.COphysics.atom-phMDPI Physics(2021)·1 citation
4. 04*

   Octant of ${\theta }_{23}$, MH, $0\nu \beta \beta$ decay and vacuum alignment of $A_4$ flavour symmetry in an inverse seesaw model

   Maibam Ricky Devi🇮🇳 · Kalpana Bora🇮🇳

   Measurements of disappearance channel of long baseline accelerator based experiments (like NO$\nu$A) are inflicted with the problem of octant degeneracy. In these experiments, the mass hierarchy (MH) sensitivity depends upon the value of CP-violating phase ${\delta }_{CP}$. Moreover, MH of light neutrino masses is still not fixed. Also, the flavour structure of fermions is yet not fully understood. We discuss all these issues, in a highly predictive, low-scale inverse seesaw (ISS) model within the framework of $A_4$ flavour symmetry. Recent global analysis has shown a preference for normal hierarchy and higher octant of ${\theta }_{23}$, and hence we discuss our results with reference to these, and find that the vacuum alignment of $A_4$ triplet flavon (1,-1,-1) favours these results. Finally, we check if our very precise prediction on $m_{ee}$ and the lightest neutrino mass falls within the range of sensitivities of the neutrinoless double beta decay ($0\nu \beta \beta$) experiments. We note that when octant of ${\theta }_{23}$ and MH is fixed by more precise measurements of future experiments, then through our results, it would be possible to precisely identify the favourable vacuum alignment corresponding to the $A_4$ triplet field as predicted in our model.

   hep-phMod.Phys.Lett.A(2022)·6 citations
5. 05*

   A machine learning pipeline for autonomous numerical analytic continuation of Dyson-Schwinger equations

   Andreas Windisch🇺🇸 · Thomas Gallien🇦🇹 · Christopher Schwarzlmueller🇦🇹

   Dyson-Schwinger equations (DSEs) are a non-perturbative way to express n-point functions in quantum field theory. Working in Euclidean space and in Landau gauge, for example, one can study the quark propagator Dyson-Schwinger equation in the real and complex domain, given that a suitable and tractable truncation has been found. When aiming for solving these equations in the complex domain, that is, for complex external momenta, one has to deform the integration contour of the radial component in the complex plane of the loop momentum expressed in hyper-spherical coordinates. This has to be done in order to avoid poles and branch cuts in the integrand of the self-energy loop. Since the nature of Dyson-Schwinger equations is such, that they have to be solved in a self-consistent way, one cannot analyze the analytic properties of the integrand after every iteration step, as this would not be feasible. In these proceedings, we suggest a machine learning pipeline based on deep learning (DL) approaches to computer vision (CV), as well as deep reinforcement learning (DRL), that could solve this problem autonomously by detecting poles and branch cuts in the numerical integrand after every iteration step and by suggesting suitable integration contour deformations that avoid these obstructions. We sketch out a proof of principle for both of these tasks, that is, the pole and branch cut detection, as well as the contour deformation.

   hep-phcs.LGhep-thEPJ Web Conf.(2022)·3 citations
6. 06*

   Studying chiral imbalance using Chiral Perturbation Theory

   Andrea Vioque-Rodríguez🇪🇸 · Angel Gómez Nicola🇪🇸 · Domènec Espriu🇪🇸

   We analize the most general low-energy effective lagrangian including local parity violating terms parametrized by an axial chemical potential ${\mu }_5$. This result is obtained following the external source method, up to $\mathcal{O}(p^4)$ order in the chiral expansion for two light flavours. We show that the $\mathcal{O}(p^4)$ lagrangian includes new terms proportional to ${\mu }_5^2$ and new low-energy constants. Finally, the ${\mu }_5$ and temperature dependences of several observables related to the vacuum energy density are studied.

   hep-phPoS(2022)·0 citations
7. 07*

   Search for invisible dark photon in $\gamma e$ scattering at future lepton colliders

   S.C. İnan🇹🇷 · A.V. Kisselev🇷🇺

   For the first time, the production of a massive dark photon (DP) in the $\gamma e^{-}$ scattering at the future lepton colliders ILC, CLIC, and CEPC is examined. The invisible decay mode of the DP is addressed. We have studied both the unpolarized scattering and the collision of the Compton backscattered photons with the polarized electron. The missing energy distributions are shown. We have considered the wide range 10 GeV -- 1000 GeV of the DP mass $m_{A^{\prime }}$. The excluded regions at the 95\% C.L. in the plane $(\epsilon ,m_{A^{\prime }})$, where $\epsilon$ is the kinetic mixing parameter, are obtained.

   hep-phhep-exEPJC(2022)·7 citations
8. 08*

   Boson stars and black holes with wavy scalar hair

   Yves Brihaye (Université de Mons, Belgium)🇧🇪 · Betti Hartmann (University College London, UK)🇧🇷

   In this paper, we follow up on the discovery of a new type of solution in the Einstein-Maxwell system coupled minimally to a self-interacting complex scalar field. For sufficiently large gravitational coupling and sufficiently small electromagnetic coupling we demonstrate that boson stars as well as black holes can carry scalar hair that shows a distinct new feature~: a number of spatial oscillations in the scalar field away from the core or horizon, respectively. These spatial oscillations appear also in the curvature invariants and hence should be a detectable feature of the space-time. As a first hint that this is true, we show that the effective potential for null geodesics in this space-time possesses a local minimum indicating that in the spatial region where oscillations occur a new stable photon sphere should be possible. We also study the interior of the black holes with scalar hair and show that the curvature singularity appears at a finite value of the radius and that black holes with wavy scalar hair have this singularity very close to the center.

   ↳ gr-qchep-phhep-thPRD(2022)·15 citations
9. 09*

   Chirality dependence in charge and heat transport in thermal QCD

   Pushpa · Binoy Krishna Patra🇮🇳

   In the presence of weak magnetic field ($B$), novel phenomena, similar to Hall effect in condensed matter physics, emerge both in charge and heat transport in a thermal QCD medium. Here, we have employed the kinetic theory approach within a quasiparticle framework, wherein the effective masses for left (L) and right-handed (R) chiral modes of quarks are seen different, lifting the prevalent degeneracy. Another implication of weak $B$ is that the coefficients assume a tensorial structure: The diagonal elements represent the usual conductivities: ${\sigma }_{\text{Ohmic}}$ and ${\kappa }_0$ as the coefficients of charge and heat transport, respectively and the off-diagonal elements denote their Hall counterparts: ${\sigma }_{\text{Hall}}$ and ${\kappa }_1$, respectively. Finally, we have derived some coefficients, namely, the Knudsen number and Lorenz number in Wiedemann-Franz law. Lorenz number and Hall-Lorenz number for L-mode increases and for R-mode decreases with a magnetic field. it does not remain constant with $T$ hence violating the Wiedemann-Franz law.

   ↳ nucl-thhep-phPRD(2022)·12 citations
10. 10*

    Spontaneous non-Hermiticity in the (2+1)-dimensional Gross-Neveu model

    T. G. Khunjua🇬🇪 · K. G. Klimenko🇷🇺 · R. N. Zhokhov🇷🇺

    Using a nonperturbative approach based on the Cornwall-Jackiw-Tomboulis effective action $\Gamma (S)$ for composite operators ($S$ is the full fermion propagator), the phase structure of the simplest massless (2 + 1)-dimensional Gross-Neveu model is investigated. We have calculated $\Gamma (S)$ and its stationary (or Dyson-Schwinger) equation in the first order of the bare coupling constant $G$ and have shown that there exist a well-defined dependence of $G\equiv G(\Lambda )$ on the cutoff parameter $\Lambda$, such that the Dyson-Schwinger equation is renormalized. It has three different solutions for fermion propagator $S$ corresponding to possible dynamical appearance of three different mass terms in the model. One is a Hermitian, but two others are non-Hermitian and $\text{cP}\text{cT}$ even or odd. It means that two phases with spontaneous non-Hermiticity can be emerged in the system. Moreover, mass spectrum of quasiparticles is real in these non-Hermitian and $\text{cP}\text{cT}$ even/odd phases.

    ↳ hep-thhep-phPRD(2022)·7 citations
11. 11*

    Conserved charges in Chern-Simons modified theory and memory effects

    Shaoqi Hou🇨🇳 · Tao Zhu🇨🇳 · Zong-Hong Zhu🇨🇳

    In this work, conserved charges and fluxes at the future null infinity are determined in the asymptotically flat spacetime for Chern-Simons modified gravity. The flux-balance laws are used to constrain the memory effects. For tensor memories, the Penrose's conformal completion method is used to analyze the asymptotic structures and asymptotic symmetries, and then, conserved charges for the Bondi-Metzner-Sachs algebra are constructed with the Wald-Zoupas formalism. These charges take very similar forms to those in Brans-Dicke theory. For the scalar memory, Chern-Simons modified gravity is rewritten in the first-order formalism, and the scalar field is replaced by a 2-form field dual to it. With this dual formalism, the scalar memory is described by the vacuum transition induced by the large gauge transformation of the 2-form field.

    ↳ gr-qchep-phhep-thJCAP(2022)·23 citations
12. 12*

    The background field method applied to cosmological phase transition

    Phan Hong Lien🇻🇳 · Nguyen Nhu Xuan🇻🇳

    In this paper, the cosmic phase transition is investigated by background gauge field method. As a continuation of previous our work, some numerical results and graphic solutions at $T\ne 0$ are presented. Hence the mechanism of cosmic phase transition in the early Universe is considered. It is shown that the breaking of symmetry significantly depend on the nonzero temperature and chemical potential. Furthermore, it is the first order of phase transition. Non - restoration of symmetry in hot gauge theories for Cosmology.

    ↳ physics.gen-phhep-phhep-th0 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.