Mon·Mar 18, 2019Monday·March 18, 2019

1. 01*

   Clockwork Neutrinos

   Sungwoo Hong🇺🇸 · Gowri Kurup🇺🇸 · Maxim Perelstein🇺🇸

   Clockwork (CW) mechanism can explain the smallness of neutrino masses without introducing unnaturally small input parameters. In this paper we study the simplest CW neutrino model, the "uniform" clockwork, as well as a broader class of "generalized" clockwork models. We derive constraints on such models from lepton-flavor violating processes, as well as precision electroweak fits. These constraints allow excited CW neutrino states with masses of order 100 GeV -- 1 TeV, within reach of the LHC and proposed lepton colliders, as long as the input neutrino Yukawa coupling is of order $10^{-1}-10^{-2}$. We study collider phenomenology of these models. At the LHC, models with light ($\sim 100$~GeV) CW neutrinos can be discovered using the $3\ell +$ MET signature. Lepton colliders will be able to discover the CW neutrinos as long as they are within their kinematic range.

   hep-phJHEP(2019)·21 citations
2. 02*

   Baryogenesis From Flavon Decays

   Mu-Chun Chen🇺🇸 · Seyda Ipek🇺🇸 · Michael Ratz🇺🇸

   Many popular attempts to explain the observed patterns of fermion masses involve a flavon field. Such weakly coupled scalar fields tend to dominate the energy density of the universe before they decay. If the flavon decay happens close to the electroweak transition, the right-handed electrons stay out of equilibrium until the sphalerons shut off. We show that an asymmetry in the right-handed charged leptons produced in the decay of a flavon can explain the baryon asymmetry of the universe.

   hep-phPRD(2019)·14 citations
3. 03*

   Search for dark photon, axion-like particles, dark scalar, or light dark matter in Compton-like processes

   Sankha S. Chakrabarty🇺🇸 · Igal Jaeglé🇺🇸

   We propose a novel way to search for the dark photon ($A^{\prime }$), the axion-like pseudo-scalar ($a$), the dark scalar ($\varphi$), and the light dark matter ($\chi$) in the Compton-like processes, $\gamma +e^{-}\to A^{\prime }/a/\varphi +e^{-}$ with $A^{\prime }/a/\varphi$ decaying into leptons, photons, or $\chi$'s (when permitted) for the mass ranges of $m_{A^{\prime }/a/\varphi }\le$ 100 MeV/$c^2$ and $m_{\chi }\le$ 50 MeV/$c^2$. We examine how the past, current, and future fixed target experiments can use this under-explored production mechanism of dark particles. We show that the existing and planned tagged photon beam fixed-target experiments (GlueX, LEPS2, LEPS, and FOREST) are competitive with the electron beam fixed target experiments, particularly for searching an invisible particle. We also show that the photon flux produced in the beam dump experiments increases the dark particle flux significantly and therefore the sensitivities of these experiments. By only considering the Compton-like processes, we determine the new limits and expected sensitivities for several beam dump and active beam dump experiments (E774, E141, KEK, Orsay, E137, NA64, BDX and LDMX) on the kinetic mixing parameter ($ϵ$) between the dark photon and the Standard Model photon, the axion-like pseudo-scalar coupling to electrons ($g_{ae}$), the dark scalar coupling to electrons ($y_e$) and the dimensionless interaction strength ($y$) to light dark matter.

   hep-phhep-exnucl-ex14 citations
4. 04*

   Hadronic Spectra from Deformed AdS Backgrounds

   Eduardo Folco Capossoli🇧🇷 · Miguel Angel Martín Contreras🇨🇱 · Danning Li🇨🇳 · Alfredo Vega🇨🇱 · Henrique Boschi-Filho🇧🇷

   Because of the presence of modified warp factors in metric tensors, we use deformed AdS${}_5$ spaces to apply the AdS/CFT correspondence to calculate the spectra for even and odd glueballs, scalar and vector mesons, and baryons with different spins. For the glueball cases, we derive their Regge trajectories and compare them with those related to the pomeron and the odderon. For the scalar and vector mesons as well as baryons the determined masses are compatible with the PDG. In particular for these hadrons we found Regge trajectories compatible with another holographic approach as well as with the hadronic spectroscopy, which present an universal Regge slope of approximately 1.1 GeV${}^2$.

   hep-phhep-thCPC(2020)·60 citations
5. 05*

   Vector and Scalar Mesons' Mixing from QCD Sum Rules

   Ze-Sheng Chen🇨🇳 · Zhu-Feng Zhang🇨🇳 · Zhuo-Ran Huang🇨🇳 · T. G. Steele🇨🇦 · Hong-Ying Jin🇨🇳

   We study $\bar{q}q$-hybrid mixing for the light vector mesons and $\bar{q}q$-glueball mixing for the light scalar mesons in Monte-Carlo based QCD Laplace sum rules. By calculating the two-point correlation function of a vector $\bar{q}{\gamma }_{\mu }q$ (scalar $\bar{q}q$) current and a hybrid (glueball) current we are able to estimate the mass and the decay constants of the corresponding mixed "physical state" that couples to both currents. Our results do not support strong quark/gluonic mixing for either the $1^{--}$ or the $0^{++}$ states.

   hep-phJHEP(2019)·3 citations
6. 06*

   Threshold Resummation for Dark-Matter Production at the LHC

   Michael Krämer🇩🇪 · Anna Kulesza🇩🇪 · Alexander Mück🇩🇪 · Robin Schürmann🇩🇪

   We derive precision predictions for the production of dark-matter particles recoiling against a jet with large transverse momentum at the LHC. The dark-matter fermions are described within a simplified model and couple to the Standard Model via a vector mediator. Our predictions for the mono-jet signature include the resummation of the leading and next-to-leading threshold logarithms. The corresponding matching coefficient is evaluated at NLO. The resummed result is matched to the fixed-order NLO cross section obtained from the MadGraph framework. We discuss numerical results for several benchmark scenarios at the LHC.

   hep-phJHEP(2019)·2 citations
7. 07*

   Probing nonstandard lepton number violating interactions in neutrino oscillations

   Patrick D. Bolton🇬🇧 · Frank F. Deppisch🇬🇧

   We discuss lepton number violating processes in the context of long-baseline neutrino oscillations. We summarise and compare neutrino flavour oscillations in quantum mechanics and quantum field theory, both for standard oscillations and for those that violate lepton number. When the active neutrinos are Majorana in nature, the required helicity reversal gives a strong suppression by the neutrino mass over the energy, $(m_{\nu }/E_{\nu }{)}^2$. Instead, the presence of non-standard lepton number violating interactions incorporating right-handed lepton currents at production or detection alleviate the mass suppression while also factorising the oscillation probability from the total rate. Such interactions arise from dimension-six operators in the low energy effective field theory of the Standard Model. We derive general and simplified expressions for the lepton number violating oscillation probabilities and use limits from MINOS and KamLAND to place bounds on the interaction strength in interplay with the unknown Majorana phases in neutrino mixing. We compare the bounds with those from neutrinoless double beta decay and other microscopic lepton number violating processes and outline the requirements for future short- and long-baseline neutrino oscillation experiments to improve on the existing bounds.

   hep-phPRD(2019)·18 citations
8. 08*

   The top-quark mass: challenges in definition and determination

   Gennaro Corcella🇮🇹

   The top-quark mass is a parameter of paramount importance in particle physics, playing a crucial role in the electroweak precision tests and in the stability of the Standard Model vacuum. I will discuss the main strategies to extract the top-quark mass at the LHC and the interpretation of the measurements in terms of well-posed top-mass definitions, taking particular care about renormalon ambiguities, progress in Monte Carlo event generators for top physics and theoretical uncertainties.

   hep-phFront.in Phys.(2019)·34 citations
9. 09*

   On some implications of the BaBar data on the ${\gamma }^{\ast }{\eta }^{\prime }$ transition form factor

   Peter Kroll🇩🇪 · Kornelija Passek-Kumerički🇭🇷

   At leading-twist accuracy the form factors for the transitions from a virtual photon to the $\eta$ or ${\eta }^{\prime }$ can be expanded into a power series of the variable $\omega$, being related to the difference of two photon virtualities. The series possess the remarkable feature that only the Gegenbauer coefficients of the meson distribution amplitudes of order $l\le m$ contribute to the term $\sim {\omega }^m$. Thus, for $\omega \to 0$ only the asymptotic meson distribution amplitude contributes, allowing for a test of the mixing of the $\eta$ and ${\eta }^{\prime }$ decay constants. Employing the Gegenbauer coefficients determined in analysis of the form factors in the real photon limit, we present predictions for the ${\gamma }^{\ast }\eta$ and ${\gamma }^{\ast }{\eta }^{\prime }$ form factors and compare them to the BaBar data.

   hep-phPLB(2019)·6 citations
10. 10*

    Isocurvature bounds on axion-like particle dark matter in the post-inflationary scenario

    Martin Feix🇩🇪 · Johann Frank🇩🇪 · Andreas Pargner🇩🇪 · Robert Reischke🇮🇱 · Bjoern Malte Schaefer🇩🇪 · Thomas Schwetz🇩🇪

    We assume that dark matter is comprised of axion-like particles (ALPs) generated by the realignment mechanism in the post-inflationary scenario. This leads to isocurvature fluctuations with an amplitude of order one for scales comparable to the horizon at the time when the ALP field starts oscillating. The power spectrum of these fluctuations is flat for small wave numbers, extending to scales relevant for cosmological observables. Denoting the relative isocurvature amplitude at $k_{\ast }$ = 0.05 Mpc${}^{-1}$ by $f_{\mathrm{iso}}$, Planck observations of the cosmic microwave background (CMB) yield $f_{\mathrm{iso}}$ < 0.31 at the 2$\sigma$-level. This excludes the hypothesis of post-inflationary ALP dark matter with masses $m_a$ < 10${}^{-20}-$10${}^{-16}$ eV, where the range is due to details of the ALP mass-temperature dependence. Future CMB stage IV and 21-cm intensity mapping experiments may improve these limits by 1$-$2 orders of magnitude in $m_a$.

    ↳ astro-ph.COhep-phJCAP(2019)·39 citations
11. 11*

    Late universe decaying dark matter can relieve the H_0 tension

    Kyriakos Vattis🇺🇸 · Savvas M. Koushiappas (Brown)🇺🇸 · Abraham Loeb (Harvard)🇺🇸

    We study the cosmological effects of two-body dark matter decays where the products of the decay include a massless and a massive particle. We show that if the massive daughter particle is slightly warm it is possible to relieve the tension between distance ladder measurements of the present day Hubble parameter with measurements from the cosmic microwave background.

    ↳ astro-ph.COhep-phPRD(2019)·217 citations
12. 12*

    High-energy emissions from neutron star mergers

    Shigeo S. Kimura🇺🇸

    In 2017, LIGO-Virgo collaborations reported detection of the first neutron star merger event, GW170817, which is accompanied by electromagnetic counterparts from radio to gamma rays. Although high-energy neutrinos were not detected from this event, mergers of neutron stars are expected to produce such high-energy particles. Relativistic jets are launched when neutron stars merge. If the jets contain protons, they can emit high-energy neutrinos through photomeson production. In addition, neutron star mergers produce massive and fast ejecta, which can be a source of Galactic high-energy cosmic rays above the knee. We briefly review what we learned from the multi-messenger event, GW170817, and discuss prospects for multi-messenger detections and hadronic cosmic-ray production related to the neutron star mergers.

    ↳ astro-ph.HEhep-phEPJ Web Conf.(2019)·4 citations
13. 13*

    The Sun at GeV--TeV Energies: A New Laboratory for Astroparticle Physics

    M.U. Nisa🇺🇸 · J.F. Beacom🇺🇸 · S.Y. BenZvi🇺🇸 · R.K. Leane🇺🇸 · T. Linden🇺🇸 · K.C.Y. Ng🇮🇱 · A.H.G. Peter🇺🇸 · B. Zhou🇺🇸

    The Sun is an excellent laboratory for astroparticle physics but remains poorly understood at GeV--TeV energies. Despite the immense relevance for both cosmic-ray propagation and dark matter searches, only in recent years has the Sun become a target for precision gamma-ray astronomy with the Fermi-LAT instrument. Among the most surprising results from the observations is a hard excess of GeV gamma-ray flux that strongly anti-correlates with solar activity, especially at the highest energies accessible to Fermi-LAT. Most of the observed properties of the gamma-ray emission cannot be explained by existing models of cosmic-ray interactions with the solar atmosphere. GeV--TeV gamma-ray observations of the Sun spanning an entire solar cycle would provide key insights into the origin of these gamma rays, and consequently improve our understanding of the Sun's environment as well as the foregrounds for new physics searches, such as dark matter. These can be complemented with new observations with neutrinos and cosmic rays. Together these observations make the Sun a new testing ground for particle physics in dynamic environments.

    ↳ astro-ph.HEastro-ph.SRhep-ph43 citations
14. 14*

    Relating eccentricity fluctuations to density fluctuations in heavy-ion collisions

    Rajeev S. Bhalerao🇮🇳 · Giuliano Giacalone🇫🇷 · Pablo Guerrero-Rodríguez🇪🇸 · Matthew Luzum🇧🇷 · Cyrille Marquet🇫🇷 · Jean-Yves Ollitrault🇫🇷

    The magnitude of anisotropic flow in a nucleus-nucleus collision is determined by the energy density field, $\rho (x,y,z)$, created right after the collision occurs. Specifically, elliptic flow, $v_2$, and triangular flow, $v_3$, are proportional to the anisotropy coefficients ${\epsilon }_2$ and ${\epsilon }_3$, which are functionals of $\rho$. We express the mean and the variance of ${\epsilon }_2$ and ${\epsilon }_3$ as a function of the 1- and 2-point functions of $\rho$. These results generalize results obtained previously, that were valid only for central collisions, or only for identical point-like sources. We apply them to the color glass condensate effective theory, using the recently derived expression of the 2-point function.

    ↳ nucl-thhep-phnucl-exActa Phys.Polon.B(2019)·12 citations
15. 15*

    Possible origin of the slow-diffusion region around Geminga

    Kun Fang🇨🇳 · Xiao-Jun Bi🇨🇳 · Peng-Fei Yin🇨🇳

    Geminga pulsar is surrounded by a multi-TeV $\gamma$-ray halo radiated by the high energy electrons and positrons accelerated by the central pulsar wind nebula (PWN). The angular profile of the $\gamma$-ray emission reported by HAWC indicates an anomalously slow diffusion for the cosmic-ray electrons and positrons in the halo region around Geminga. In the paper we study the possible mechanism for the origin of the slow diffusion. At first, we consider the self-generated Alfvén waves due to the streaming instability of the electrons and positrons released by Geminga. However, even considering a very optimistic scenario for the wave growth, we find this mechanism DOES NOT work to account for the extremely slow diffusion at the present day if taking the proper motion of Geminga pulsar into account. The reason is straightforward as the PWN is too weak to generate enough high energy electrons and positrons to stimulate strong turbulence at the late time. We then propose an assumption that the strong turbulence is generated by the shock wave of the parent supernova remnant (SNR) of Geminga. Geminga may still be inside the SNR, and we find that the SNR can provide enough energy to generate the slow-diffusion circumstance. The TeV halos around PSR B0656+14, Vela X, and PSR J1826-1334 may also be explained under this assumption.

    ↳ astro-ph.HEhep-phMNRAS(2019)·83 citations
16. 16*

    Nucleon axial, scalar, and tensor charges using lattice QCD at the physical pion mass

    Nesreen Hasan🇩🇪 · Jeremy Green🇩🇪 · Stefan Meinel🇺🇸 · Michael Engelhardt🇺🇸 · Stefan Krieg🇩🇪 · John Negele🇺🇸 · Andrew Pochinsky🇺🇸 · Sergey Syritsyn🇺🇸

    We report on lattice QCD calculations of the nucleon isovector axial, scalar, and tensor charges. Our calculations are performed on two 2+1-flavor ensembles generated using a 2-HEX-smeared Wilson-clover action at the physical pion mass and lattice spacings $a\approx$ 0.116 and 0.093 fm. We use a wide range of source-sink separations - eight values ranging from roughly 0.4 to 1.4 fm on the coarse ensemble and three values from 0.9 to 1.5 fm on the fine ensemble - which allows us to perform an extensive study of excited-state effects using different analysis and fit strategies. To determine the renormalization factors, we use the nonperturbative Rome-Southampton approach and compare RI'-MOM and RI-SMOM intermediate schemes to estimate the systematic uncertainties. Our final results are computed in the MS-bar scheme at scale 2 GeV. The tensor and axial charges have uncertainties of roughly 4%, $g_T=0.972(41)$ and $g_A=1.265(49)$. The resulting scalar charge, $g_S=0.927(303)$, has a much larger uncertainty due to a stronger dependence on the choice of intermediate renormalization scheme and on the lattice spacing.

    ↳ hep-lathep-phnucl-thPRD(2019)·73 citations
17. 17*

    Reconstructing a Model for Gravity at Large Distances from Dark Matter Density Profiles

    L. Perivolaropoulos🇬🇷 · F. Skara🇬🇷

    Using the Navarro-Frenk-White (NFW) dark matter density profile we reconstruct an effective field theory model for gravity at large distances from a central object by demanding that the vacuum solution has the same gravitational properties as the NFW density profile has in the context of General Relativity (GR). The dimensionally reduced reconstructed action for gravity leads to a vacuum metric that includes a modified Rindler acceleration term in addition to the Schwarzschild and cosmological constant terms. The new term is free from infrared curvature singularities and leads to a much better fit of observed galaxy velocity rotation curves than the corresponding simple Rindler term of the Grumiller metric, at the expense of one additional parameter. When the new parameter is set to zero the new metric term reduces to a Rindler constant acceleration term. We use galactic velocity rotation data to find the best fit values of the parameters of the reconstructed geometric potential and discuss possible cosmological implications.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2019)·8 citations
18. 18*

    Cosmic string loop production functions

    Pierre Auclair🇫🇷 · Christophe Ringeval🇧🇪 · Mairi Sakellariadou🇬🇧 · Daniele Steer🇫🇷

    Numerical simulations of Nambu-Goto cosmic strings in an expanding universe show that the loop distribution relaxes to an universal configuration, the so-called scaling regime, which is of power law shape on large scales. Precise estimations of the power law exponent are, however, still matter of debate while numerical simulations do not incorporate all the radiation and backreaction effects expected to affect the network dynamics at small scales. By using a Boltzmann approach, we show that the steepness of the loop production function with respect to loops size is associated with drastic changes in the cosmological loop distribution. For a scale factor varying as a(t)~t^nu, we find that sub-critical loop production functions, having a Polchinski-Rocha exponent chi < (3nu-1)/2, yield scaling loop distributions which are mostly insensitive to infra-red (IR) and ultra-violet (UV) assumptions about the cosmic string network. For those, cosmological predictions are expected to be relatively robust, in accordance with previous results. On the contrary, critical and super-critical loop production functions, having chi >= (3nu-1)/2, are shown to be IR-physics dependent and this generically prevents the loop distribution to relax towards scaling. In the latter situation, we discuss the additional regularisations needed for convergence and show that, although a scaling regime can still be reached, the shape of the cosmological loop distribution is modified compared to the naive expectation. Finally, we discuss the implications of our findings.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2019)·46 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.