Wed·Jun 28, 2017Wednesday·June 28, 2017

1. 01*

   Dark matter indirect signals with long-lived mediators

   Xiaoyong Chu🇦🇹 · Suchita Kulkarni🇦🇹 · Pierre Salati🇫🇷

   Dark matter particles could annihilate into light and metastable mediators subsequently decaying far away from where they are produced. In this scenario, the indirect signatures of dark matter are altered with respect to the conventional situation where standard model particles are directly injected where annihilation happens. We explore here this new phenomenology for which we devise the tools. We calculate the effective dark matter distribution resulting from the smearing by mediator propagation. We derive the fluxes of mediators and their decay particles. We study how the $J$-factor, which naturally appears in the calculation of the dark matter induced gamma ray signal, is modified in the presence of mediators. We also derive the anisotropy which the cosmic ray positron flux exhibits in this scenario. We finally comment upon a recent proposal based on long-lived mediators where the effective dark matter density at the Earth is increased such as to explain the cosmic ray positron anomaly. We conclude that this scenario is barely tenable as regards the very dense dark matter spike which it requires at the Galactic center. The associated positron anisotropy is very small and undetectable, except at high energies where it reaches a level of order $10^{-4}$ to $10^{-3}$.

   hep-phastro-ph.HEJCAP(2017)·15 citations
2. 02*

   Top Down Electroweak Dipole Operators

   Kaori Fuyuto🇺🇸 · Michael Ramsey-Musolf🇺🇸

   We derive present constraints on, and prospective sensitivity to, the electric dipole moment (EDM) of the top quark ($d_t$) implied by searches for the EDMs of the electron and nucleons. Above the electroweak scale $v$, the $d_t$ arises from two gauge invariant operators generated at a scale $\Lambda \gg v$ that also mix with the light fermion EDMs under renormalization group evolution at two-loop order. Bounds on the EDMs of first generation fermion systems thus imply bounds on $|d_t|$. Working in the leading log-squared approximation, we find that the present upper bound on $|d_t|$ is roughly $10^{-19}$ $e$ cm for $\Lambda =1$ TeV, except in regions of finely tuned cancellations that allow for $|d_t|$ to be up to fifty times larger. Future $d_e$ and $d_n$ probes may yield an order of magnitude increase in $d_t$ sensitivity, while inclusion of a prospective proton EDM search may lead to an additional increase in reach.

   hep-phPLB(2018)·25 citations
3. 03*

   Rapidity distribution of particle multiplicity in DIS at small x

   B. Blok (1) · Yu. Dokshitzer (2) · M. Strikman (3) ((1) Technion · (2) LPTHE · (3) Penn State)

   Analytical study of the rapidity distribution of the final state particles in deep inelastic scattering at small x is presented. We separate and analyse three sources of particle production: fragmentation of the quark-antiquark pair, accompanying coherent soft gluon radiation due to octet color exchange in the t-channel, and fragmentation of gluons that form parton distribution functions. Connection to Catani-Ciafaloni-Fiorani-Marchesini (CCFM) equations and the role of gluon reggezation are also discussed.

   hep-phnucl-thPLB(2017)·2 citations
4. 04*

   Neutrino self-energy with new physics effects in an external magnetic field

   Carlos G. Tarazona🇨🇴 · Andrés Castillo🇨🇴 · Rodolfo A. Diaz🇨🇴 · John Morales🇨🇴

   We compute the magnetic dipole moment (MDM) for massive flavor neutrinos using the neutrino self-energy in a magnetized media. The framework to incorporate neutrino masses is one minimal extension of the Standard Model in which neutrinos are Dirac particles and their masses coming from tiny Yukawa couplings from a second Higgs doublet with a small vacuum expectation value. The computations are carried out by using proper time formalism in the weak field approximation $eB<<m_e^2$ and assuming normal hierarchy for neutrino masses and sweeping the charged Higgs mass. For ${\nu }_{\tau }$, analyses in the neutrino specific scenario indicate magnetic dipole moments greater than the values obtained to the MDM in the SM (with and without magnetic fields) and other flavor conserving models. This fact leading a higher proximity with experimental bounds and so on it is possible to get stronger exclusion limits over new physics parameter space.

   hep-ph2 citations
5. 05*

   Oscillating Affleck-Dine condensate and its cosmological implications

   Fuminori Hasegawa🇯🇵 · Masahiro Kawasaki🇯🇵

   We study the dynamics of the Affleck-Dine field after inflation in more detail. After inflation, the Affleck-Dine field inevitably oscillates around the potential minimum. This oscillation is hard to decay and can cause accidental suppression of the consequential baryon asymmetry. This suppression is most effective for the model with non-renormalizable superpotential $W_{AD}\sim {\Phi }^4$ ($\Phi$: Affleck-Dine field). It is found that the Affleck-Dine leptogenesis in high-scale inflation, which suffers from serious gravitino overproduction, becomes workable owing to this effect.

   hep-phastro-ph.COPRD(2017)·1 citation
6. 06*

   Scattering from a quantum anapole at low energies

   Kyle M. Whitcomb🇺🇸 · David C. Latimer🇺🇸

   In quantum field theory, the photon-fermion vertex can be described in terms of four form factors which encode the static electromagnetic properties of the particle, namely its charge, magnetic dipole moment, electric dipole moment, and anapole moment. For Majorana fermions, only the anapole moment can be nonzero, a consequence of the fact that these particles are their own antiparticles. Using the framework of quantum field theory, we perform a scattering calculation which probes the anapole moment with a spinless charged particle. In the limit of low-momentum transfer, we confirm that the anapole can be classically likened to a point-like toroidal solenoid whose magnetic field is confined to the origin. Such a toroidal current distribution can be used to demonstrate the Aharonov-Bohm effect. We find that, in the non-relativistic limit, our scattering cross section agrees with a quantum mechanical computation of the cross section for a spinless current scattered by an infinitesimally thin toroidal solenoid. Our presentation is geared toward advanced undergraduate or beginning graduate students. This work serves as an introduction to the anapole moment and also provides an example of how one can develop an understanding of a particle's electromagnetic properties in quantum field theory.

   hep-phhep-thquant-phAm.J.Phys.(2017)·6 citations
7. 07*

   Color Screening and Regeneration of Bottomonia in High-Energy Heavy-Ion Collisions

   Xiaojian Du🇺🇸 · Min He🇨🇳 · Ralf Rapp🇺🇸

   The production of ground-state and excited bottomonia in ultrarelativistic heavy-ion collisions is investigated within a kinetic-rate equation approach including regeneration. We augment our previous calculations by an improved treatment of medium effects, with temperature-dependent binding energies and pertinent reaction rates, $B$-meson resonance states in the equilibrium limit near the hadronization temperature, and a lattice-QCD based equation of state for the bulk medium. In addition to the centrality dependence of the bottomonium yields we compute their transverse-momentum ($p_T$) spectra and elliptic flow with momentum-dependent reaction rates and a regeneration component based on $b$-quark spectra from a nonperturbative transport model of heavy-quark diffusion. The latter has noticeable consequences for the shape of the bottomonium $p_T$ spectra. We quantify how uncertainties in the various modeling components affect the predictions for observables. Based on this we argue that the ${\rm Y}(1S)$ suppression is a promising observable for mapping out the in-medium properties of the QCD force, while ${\rm Y}(2S)$ production can help to quantify the role of regeneration from partially thermalized $b$ quarks.

   hep-phnucl-exnucl-thPRC(2017)·200 citations
8. 08*

   Thermalization in small system of hadron gas and high-multiplicity pp events

   Nachiketa Sarkar🇮🇳 · Premomoy Ghosh🇮🇳

   We study the system-size dependence of Knudsen number, a measure of degree of thermalization, for hadron resonance gas that follows the Lattice-QCD equation of state at zero chemical potential. A comparison between Knudsen numbers for the AuAu collisions at RHIC and the hadron gas of size similar to the size of high-multiplicity pp events at LHC, reassures the applicability of hydrodynamics in interpreting the features of particle production in high-multiplicity pp events.

   hep-phhep-exnucl-thPRC(2017)·19 citations
9. 09*

   Precision Theoretical Analysis of Neutron Radiative Beta Decay to Order "O(\alpha^2/\pi^2)"

   A. N. Ivanov🇦🇹 · R. Höllwieser🇦🇹 · N. I. Troitskaya🇦🇹 · M. Wellenzohn🇦🇹 · Ya. A. Berdnikov🇷🇺

   In the Standard Model (SM) we calculate the decay rate of the neutron radiative beta decay to order "O(\alpha^2/\pi^2 ~ 10^{-5})", where "\alpha$"is the fine--structure constant, and radiative corrections to order "O(\alpha/\pi ~ 10^{-3})". The obtained results together with the recent analysis of the neutron radiative beta decay to next-to-leading order in the large proton-mass expansion, performed by Ivanov et al. Phys. Rev. D95, 033007 (2017), describe recent experimental data by the RDK II Collaboration (Bales et al., Phys. Rev. Lett. 116, 242501 (2016)) within 1.5 standard deviations. We argue a substantial influence of strong low-energy interactions of hadrons coupled to photons on the properties of the amplitude of the neutron radiative beta decay under gauge transformations of real and virtual photons.

   hep-phastro-ph.COhep-exnucl-ex+1PRD(2017)·13 citations
10. 10*

    Triangle singularities in $B^{-}\to D^{\ast 0}{\pi }^{-}{\pi }^0\eta$ and $B^{-}\to D^{\ast 0}{\pi }^{-}{\pi }^{+}{\pi }^{-}$

    R. Pavao🇪🇸 · S. Sakai🇪🇸 · E. Oset🇪🇸

    The possible role of the triangle mechanism in the $B^{-}$ decay into $D^{\ast 0}{\pi }^{-}{\pi }^0\eta$ and $D^{\ast 0}{\pi }^{-}{\pi }^{+}{\pi }^{-}$ is investigated. In this process, the triangle singularity appears from the decay of $B^{-}$ into $D^{\ast 0}{K}^{-}{K}^{\ast 0}$ followed by the decay of $K^{\ast 0}$ into ${\pi }^{-}{K}^{+}$ and the fusion of the $K^{+}{K}^{-}$ which forms the $a_0(980)$ or $f_0(980)$ which finally decay into ${\pi }^0\eta$ or ${\pi }^{+}{\pi }^{-}$ respectively. The triangle mechanism from the ${\bar{K}}^{\ast }K\bar{K}$ loop generates a peak around 1420 MeV in the invariant mass of ${\pi }^{-}{a}_0$ or ${\pi }^{-}{f}_0$, and gives sizable branching fractions $Br(B^{-}\to D^{\ast 0}{\pi }^{-}{a}_0;a_0\to {\pi }^0\eta )=1.66\times 10^{-6}$ and $Br(B^{-}\to D^{\ast 0}{\pi }^{-}{f}_0;f_0\to {\pi }^{+}{\pi }^{-})=2.82\times 10^{-6}$.

    hep-phEPJC(2017)·33 citations
11. 11*

    Padé approximants and analytic continuation of Euclidean Phi-derivable approximations

    Gergely Markó🇭🇺 · Urko Reinosa🇫🇷 · Zsolt Szép🇭🇺

    We investigate the Padé approximation method for the analytic continuation of numerical data and its ability to access, from the Euclidean propagator, both the spectral function and part of the physical information hidden in the second Riemann sheet. We test this method using various benchmarks at zero temperature: a simple perturbative approximation as well as the two-loop Phi-derivable approximation. The analytic continuation method is then applied to Euclidean data previously obtained in the O(4) symmetric model (within a given renormalization scheme) to assess the difference between zero-momentum and pole masses, which is in general a difficult question to answer within nonperturbative approaches such as the Phi-derivable expansion scheme.

    hep-phhep-thPRD(2017)·11 citations
12. 12*

    Are neutrino masses modular forms?

    Ferruccio Feruglio🇮🇹

    We explore a new class of supersymmetric models for lepton masses and mixing angles where the role of flavour symmetry is played by modular invariance. The building blocks are modular forms of level N and matter supermultiplets, both transforming in representations of a finite discrete group Gamma_N. In the simplest version of these models, Yukawa couplings are just modular forms and the only source of flavour symmetry breaking is the vacuum expectation value of a single complex field, the modulus. In the special case where modular forms are constant functions the whole construction collapses to a supersymmetric flavour model invariant under Gamma_N, the case treated so far in the literature. The framework has a number of appealing features. Flavon fields other than the modulus might not be needed. Neutrino masses and mixing angles are simultaneously constrained by the modular symmetry. As long as supersymmetry is exact, modular invariance determines all higher-dimensional operators in the superpotential. We discuss the general framework and we provide complete examples of the new construction. The most economical model predicts neutrino mass ratios, lepton mixing angles, Dirac and Majorana phases uniquely in terms of the modulus vacuum expectation value, with all the parameters except one within the experimentally allowed range. As a byproduct of the general formalism we extend the notion of non-linearly realised symmetries to the discrete case.

    hep-phhep-th411 citations
13. 13*

    Photon-induced contributions to di-lepton production at the LHC Run II

    Juri Fiaschi🇬🇧 · Elena Accomando🇬🇧 · Francesco Hautmann🇬🇧 · Stefano Moretti🇬🇧 · Claire H. Shepherd-Themistocleous🇬🇧

    We report on recent studies of photon-induced (PI) contributions to di-lepton production and their implications for Beyond Standard Model (BSM) $Z^{\prime }$-bosons searches at the LHC.

    hep-phPoS(2018)·0 citations
14. 14*

    Electroweak vacuum stability in presence of singlet scalar dark matter in TeV scale seesaw models

    Ila Garg🇮🇳 · Srubabati Goswami🇮🇳 · Vishnudath K. N.🇮🇳 · Najimuddin Khan🇮🇳

    We consider singlet extensions of the standard model, both in the fermion and the scalar sector, to account for the generation of neutrino mass at the TeV scale and the existence of dark matter respectively. For the neutrino sector we consider models with extra singlet fermions which can generate neutrino mass via the so called inverse or linear seesaw mechanism whereas a singlet scalar is introduced as the candidate for dark matter. We show that although these two sectors are disconnected at low energy, the coupling constants of both the sectors get correlated at high energy scale by the constraints coming from the perturbativity and stability/metastability of the electroweak vacuum. The singlet fermions try to destabilize the electroweak vacuum while the singlet scalar aids the stability. As an upshot, the electroweak vacuum may attain absolute stability even upto the Planck scale for suitable values of the parameters. We delineate the parameter space for the singlet fermion and the scalar couplings for which the electroweak vacuum remains stable/metastable and at the same time giving the correct relic density and neutrino masses and mixing angles as observed.

    hep-phPRD(2017)·41 citations
15. 15*

    ${\rho }^0-\omega$ mixing in the presence of a weak magnetic field

    Mahatsab Mandal🇮🇳 · Arghya Mukherjee🇮🇳 · Snigdha Ghosh🇮🇳 · Pradip Roy🇮🇳 · Sourav Sarkar🇮🇳

    We calculate the momentum dependence of the ${\rho }^0-\omega$ mixing amplitude in vacuum with vector nucleon-nucleon interaction in presence of a constant homogeneous weak magnetic field background. The mixing amplitude is generated by the nucleon-nucleon ($NN$) interaction and thus driven by the neutron-proton mass difference along with a constant magnetic field. We find a significant effect of magnetic field on the mixing amplitude. We also calculate the Charge symmetry violating (CSV) $NN$ potential induced by the magnetic field dependent mixing amplitude. The presence of the magnetic field influences the $NN$ potential substantially which can have important consequences in highly magnetized astrophysical compact objects, such as magnetars. The most important observation of this work is that the mixing amplitude is non-zero, leading to positive contribute to the CSV potential if the proton and neutron masses are taken to be equal.

    hep-phEPJA(2018)·1 citation
16. 16*

    Electroweak Vacuum Metastability and Low-scale Inflation

    Yohei Ema🇯🇵 · Kyohei Mukaida🇯🇵 · Kazunori Nakayama🇯🇵

    We study the stability of the electroweak vacuum in low-scale inflation models whose Hubble parameter is much smaller than the instability scale of the Higgs potential. In general, couplings between the inflaton and Higgs are present, and hence we study effects of these couplings during and after inflation. We derive constraints on the couplings between the inflaton and Higgs by requiring that they do not lead to catastrophic electroweak vacuum decay, in particular, via resonant production of the Higgs particles.

    hep-phastro-ph.COJCAP(2017)·24 citations
17. 17*

    The Standard Model as an Effective Field Theory

    Ilaria Brivio🇩🇰 · Michael Trott🇩🇰

    Projecting measurements of the interactions of the known Standard Model (SM) states into an effective field theory (EFT) framework is an important goal of the LHC physics program. The interpretation of measurements of the properties of the Higgs-like boson in an EFT allows one to consistently study the properties of this state, while the SM is allowed to eventually break down at higher energies. In this review, basic concepts relevant to the construction of such EFTs are reviewed pedagogically. Electroweak precision data is discussed as a historical example of some importance to illustrate critical consistency issues in interpreting experimental data in EFTs. A future precision Higgs phenomenology program can benefit from the projection of raw experimental results into consistent field theories such as the SM, the SM supplemented with higher dimensional operators (the SMEFT) or an Electroweak chiral Lagrangian with a dominantly $J^P=0^{+}$ scalar (the HEFT). We discuss the developing SMEFT and HEFT approaches, that are consistent versions of such EFTs, systematically improvable with higher order corrections, and comment on the pseudo-observable approach. We review the challenges that have been overcome in developing EFT methods for LHC studies, and the challenges that remain.

    hep-phPhys.Rept.(2019)·960 citations
18. 18*

    Renormalization in Large Momentum Effective Theory of Parton Physics

    Xiangdong Ji🇨🇳 · Jian-Hui Zhang🇩🇪 · Yong Zhao🇺🇸

    In the large-momentum effective field theory approach to parton physics, the matrix elements of non-local operators of quark and gluon fields, linked by straight Wilson lines in a spatial direction, are calculated in lattice quantum chromodynamics as a function of hadron momentum. Using the heavy-quark effective theory formalism, we show a multiplicative renormalization of these operators at all orders in perturbation theory, both in dimensional and lattice regularizations. The result provides a theoretical basis for extracting parton properties through properly renormalized observables in Monte Carlo simulations.

    hep-phhep-latPRL(2018)·203 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.