Thu·Sep 26, 2019Thursday·September 26, 2019

1. 01*

   The New Physics Reach of Null Tests with $D\to \pi \ell \ell$ and $D_s\to K\ell \ell$ Decays

   Rigo Bause🇩🇪 · Marcel Golz🇩🇪 · Gudrun Hiller🇩🇪 · Andrey Tayduganov🇩🇪

   $|\Delta c|=|\Delta u|=1$ processes are unique probes of flavor physics in the up-sector within and beyond the Standard Model (SM). SM tests with rare semileptonic charm meson decays are based on an approximate CP--symmetry, a superior GIM--mechanism, angular distributions, lepton-universality and lepton flavor conservation. We analyze the complete set of null test observables in $D\to \pi \ell {\ell }^{(\prime )}$ and $D_s\to K\ell {\ell }^{(\prime )}$ decays, ${\ell }^{(\prime )}=e,\mu$, and find large room for new physics safely above the SM contribution. We identify signatures of supersymmetry, leptoquarks and anomaly-free $U(1{)}^{\prime }$-models with generation-dependent charges, for which we provide explicit examples. $Z^{\prime }$-effects in $c\to u\ell {\ell }^{(\prime )}$ transitions can be sizable if both left-handed and right-handed couplings to quarks are present.

   hep-phhep-exEPJC(2020)·66 citations
2. 02*

   New physics implications of recent search for $K_L\to {\pi }^0\nu \bar{\nu }$ at KOTO

   Teppei Kitahara🇮🇱 · Takemichi Okui🇺🇸 · Gilad Perez🇮🇱 · Yotam Soreq🇮🇱 · Kohsaku Tobioka🇺🇸

   The KOTO experiment recently reported four candidate events in the signal region of $K_L\to {\pi }^0\nu \bar{\nu }$ search, where the standard model only expects $0.10\pm 0.02$ events. If confirmed, this requires physics beyond the standard model to enhance the signal. We examine various new physics interpretations of the result including these: (1) heavy new physics boosting the standard model signal, (2) reinterpretation of "$\nu \bar{\nu }$" as a new light long-lived particle, or (3) reinterpretation of the whole signal as the production of a new light long-lived particle at the fixed target. We study the above explanations in the context of a generalized new physics Grossman-Nir bound coming from the $K^{+}\to {\pi }^{+}\nu \bar{\nu }$ decay, bounded by data from the E949 and the NA62 experiments.

   hep-phhep-exPRL(2020)·84 citations
3. 03*

   Neutral Mesons and Nonminimal CPT Violation

   Benjamin R. Edwards🇺🇸

   Minimal CPT violation has been constrained using observations of neutral-meson oscillations. Violation of CPT symmetry arising from nonminimal operators in the Lagrange density can also occur. A general approach using scalar effective field theory is presented and used to infer the effects of nonminimal CPT violation on neutral-meson oscillations.

   hep-ph0 citations
4. 04*

   Constraints on Sterile Neutrinos in the MeV to GeV Mass Range

   D. A. Bryman🇨🇦 · R. Shrock🇺🇸

   A detailed discussion is given of the analysis of recent data to obtain improved upper bounds on the couplings $|U_{e4}{|}^2$ and $|U_{\mu 4}{|}^2$ for a mainly sterile neutrino mass eigenstate ${\nu }_4$. Using the excellent agreement among $\mathcal{F}t$ values for superallowed nuclear beta decay, an improved upper limit is derived for emission of a ${\nu }_4$. The agreement of the ratios of branching ratios $R_{e/\mu }^{(\pi )}=BR({\pi }^{+}\to e^{+}{\nu }_e)/BR({\pi }^{+}\to {\mu }^{+}{\nu }_{\mu })$, $R_{e/\mu }^{(K)}$, $R_{e/\tau }^{(D_s)}$, $R_{\mu /\tau }^{(D_s)}$, and $R_{e/\tau }^{(D)}$, and the branching ratios $BR(B^{+}\to e^{+}{\nu }_e)$ and $BR(B^{+}\to {\mu }^{+}{\nu }_{\mu })$ decays with predictions of the Standard Model, is utilized to derive new constraints on ${\nu }_4$ emission covering the ${\nu }_4$ mass range from MeV to GeV. We also discuss constraints from peak search experiments probing for emission of a ${\nu }_4$ via lepton mixing, as well as constraints from pion beta decay, CKM unitarity, $\mu$ decay, leptonic $\tau$ decay, and other experimental inputs.

   hep-phhep-exPRD(2019)·147 citations
5. 05*

   Implications of the LHCb discovery of CP violation in charm decays

   Avital Dery🇺🇸 · Yosef Nir🇮🇱

   The recent measurement of $\Delta A_{CP}$ by the LHCb collaboration requires an $\mathcal{O}(10)$ enhancement coming from hadronic physics in order to be explained within the SM. We examine to what extent can NP models explain $\Delta A_{CP}$ without such enhancements. We discuss the implications in terms of a low energy effective theory as well as in the context of several explicit NP models.

   hep-phJHEP(2019)·78 citations
6. 06*

   Neutrino decoherence in a fermion and scalar background

   Jose F. Nieves🇺🇸 · Sarira Sahu🇲🇽

   We consider the decoherence effects in the propagation of neutrinos in a background composed of a scalar particle and a fermion due to the non-forward neutrino scattering processes. Using a simple model for the coupling of the form ${\bar{f}}_R{\nu }_L\varphi$ we calculate the contribution to the imaginary part of the neutrino self-energy arising from the non-forward neutrino scattering processes in such backgrounds, from which the damping terms are determined. In the case we are considering, in which the initial neutrino state is depleted but does not actually disappear (the initial neutrino transitions into a neutrino of a different flavor but does not decay into a $f\varphi$ pair, for example), we associate the damping terms with decoherence effects. For this purpose we give a precise prescription to identify the decoherence terms, as used in the context of the master or Linblad equation, in terms of the damping terms we have obtained from the calculation of the imaginary part of the neutrino self-energy from the non-forward neutrino scattering processes. The results can be directly useful in the context of Dark Matter-neutrino interaction models in which the scalar and/or fermion constitute the dark-matter, and can also serve to guide the generalizations to other models and/or situations in which the decoherence effects in the propagation of neutrinos originate from the non-forward scattering processes may be important. As a guide to estimating such decoherence effects, the contributions to the absorptive part of the self-energy and the corresponding damping terms are computed explicitly in the context of the model we consider, for several limiting cases of the momentum distribution functions of the background particles.

   hep-phastro-ph.HEPRD(2019)·12 citations
7. 07*

   Energy, angular momentum and pressure force distributions inside nucleons

   Cédric Lorcé (Ecole Polytechnique and CNRS)🇫🇷

   We review some of the recent developments regarding mass, angular momentum and pressure forces inside hadrons. These properties are all encoded in the energy-momentum tensor of the system, which is described at the non-perturbative level in terms of gravitational form factors. Similarly to electromagnetic form factors, Fourier transforms of gravitational form factors allow one to map out the distribution of the above mechanical properties in position space, providing a whole new way of studying in detail the internal structure of hadrons.

   hep-phnucl-thJ.Phys.Conf.Ser.(2020)·1 citation
8. 08*

   Kinetic freeze-out temperature and transverse flow velocity in Au-Au collisions at RHIC-BES energies

   Muhammad Waqas🇺🇸 · Bao-Chun Li🇨🇳

   Based on the data-driven analysis, the mid-rapidity transverse momentum spectra of charged hadrons produced in central and peripheral gold-gold (Au-Au) collisions from the Beam Energy Scan (BES) program at the relativistic Heavy Ion Collider (RHIC) are fitted by the blast-wave model with Boltzmann-Gibbs statistics. The model result are in agreement with the experimental data measured by the STAR Collaboration at the RHIC-BES energies. We observe that the kinetic freeze-out temperature, transverse flow velocity, mean transverse momentum, and initial temperature increase with the collision energy and with the event centrality.

   hep-phnucl-thAdv.High Energy Phys.(2020)·40 citations
9. 09*

   A fresh look at the gravitational-wave signal from cosmological phase transitions

   Tommi Alanne🇩🇪 · Thomas Hugle🇩🇪 · Moritz Platscher🇩🇪 · Kai Schmitz🇨🇭

   Many models of physics beyond the Standard Model predict a strong first-order phase transition (SFOPT) in the early Universe that leads to observable gravitational waves (GWs). In this paper, we propose a novel method for presenting and comparing the GW signals that are predicted by different models. Our approach is based on the observation that the GW signal has an approximately model-independent spectral shape. This allows us to represent it solely in terms of a finite number of observables, that is, a set of peak amplitudes and peak frequencies. As an example, we consider the GW signal in the real-scalar-singlet extension of the Standard Model (xSM). We construct the signal region of the xSM in the space of observables and show how it will be probed by future space-borne interferometers. Our analysis results in sensitivity plots that are reminiscent of similar plots that are typically shown for dark-matter direct-detection experiments, but which are novel in the context of GWs from a SFOPT. These plots set the stage for a systematic model comparison, the exploration of underlying model-parameter dependencies, and the construction of distribution functions in the space of observables. In our plots, the experimental sensitivities of future searches for a stochastic GW signal are indicated by peak-integrated sensitivity curves. A detailed discussion of these curves, including fit functions, is contained in a companion paper [2002.04615]. The data and code that we used in our analysis can be downloaded from Zenodo [https://doi.org/10.5281/zenodo.3699415].

   hep-phastro-ph.COgr-qchep-exJHEP(2020)·97 citations
10. 10*

    Probing the Higgs Portal at the Fermilab Short-Baseline Neutrino Experiments

    Brian Batell🇺🇸 · Joshua Berger🇺🇸 · Ahmed Ismail🇺🇸

    The Fermilab Short-Baseline Neutrino (SBN) experiments, MicroBooNE, ICARUS, and SBND, are expected to have significant sensitivity to light weakly coupled hidden sector particles. Here we study the capability of the SBN experiments to probe dark scalars interacting through the Higgs portal. We investigate production of dark scalars using both the Fermilab Booster 8 GeV and NuMI 120 GeV proton beams, simulating kaons decaying to dark scalars and taking into account the beamline geometry. We also investigate strategies to mitigate backgrounds from beam-related neutrino scattering events. We find that SBND, with its comparatively short $\mathcal{O}(100\mathrm{m})$ baseline, will have the best sensitivity to scalars produced with Booster, while ICARUS, with its large detector volume, will provide the best limits on off-axis dark scalar production from NuMI. The SBN experiments can provide leading tests of dark scalars with masses in the 50 - 350 MeV range in the near term. Our results motivate dedicated experimental searches for dark scalars and other long-lived hidden sector states at these experiments.

    hep-phhep-exPRD(2019)·67 citations
11. 11*

    Precision Small Scattering Angle Measurements of Elastic Proton-Proton Single and Double Spin Analyzing Powers at the RHIC Hydrogen Jet Polarimeter

    A.A. Poblaguev🇺🇸 · A. Zelenski🇺🇸 · E. Aschenauer🇺🇸 · G. Atoian🇺🇸 · K.O. Eyser🇺🇸 · H. Huang🇺🇸 · Y. Makdisi🇺🇸 · W.B. Schmidke🇺🇸 · I. Alekseev🇷🇺 · D. Svirida🇷🇺 · N.H. Buttimore🇮🇪

    The Polarized Atomic Hydrogen Gas Jet Target polarimeter is employed by the Relativistic Heavy Ion Collider (RHIC) to measure the absolute polarization of each colliding proton beam. Polarimeter detectors and data acquisition were upgraded in 2015 to increase solid angle, energy range and energy resolution. These upgrades and advanced systematic error analysis along with improved beam intensity and polarization in RHIC runs 2015 ($E_{\text{beam}}=100\text{GeV}$) and 2017 ($255\text{GeV}$) allowed us to greatly reduce the statistical and systematic uncertainties for elastic spin asymmetries, $A_N(t)$ and $A_{N}N(t)$, in the Coulomb-nuclear interference momentum transfer range $0.0013<-t<0.018{\text{GeV}}^2$. For the first time hadronic single spin-flip $r_5$ and double spin-flip $r_2$ amplitude parameters were reliably isolated at these energies and momentum transfers. Measurements at two beam energies enable a separation of Pomeron and Regge pole contributions to $r_5(s)$ and $r_2(s)$, indicating that the spin component may persist at high energies.

    ↳ hep-exhep-phPRL(2019)·25 citations
12. 12*

    Revealing the Structure of the Inflationary Landscape through Primordial non-Gaussianity

    Bruno Scheihing Hitschfeld🇨🇱

    In this thesis, we show how the structure of the landscape potential of the primordial Universe may be probed through the primordial density perturbations responsible for the origin of the cosmic microwave background anisotropies and the large-scale structure of our Universe. Isocurvature fields may have fluctuated across the barriers separating local minima of the landscape potential during inflation. We analyze how this process could have impacted the evolution of the primordial curvature perturbations. If the typical distance separating consecutive minima of the landscape potential and the height of the potential barriers are smaller than the Hubble expansion rate parametrizing inflation, the probability distribution function of isocurvature fields becomes non-Gaussian due to the appearance of bumps and dips associated with the structure of the potential. We show that this non-Gaussianity can be transferred to the statistics of primordial curvature perturbations. The type of non-Gaussian structure that emerges in the distribution of curvature perturbations cannot be fully probed with the standard methods of polyspectra; instead, the probability distribution function is needed. To substantiate our claims, we offer a concrete model consisting of an isocurvature perturbation with a sinusoidal potential and a linear derivative coupling between the isocurvature and curvature field. This result is generalized to arbitrary potentials and briefly studied beyond first-order perturbation theory. Finally, we undertake a study of primordial non-Gaussianity of the local type, where we use our results to reconstruct and constrain the shape of the landscape potential with the help of Cosmic Microwave Background observations by the Planck telescope and explore prospects for observable quantities in the Large-Scale Structure of our universe towards constraining its primordial statistics.

    ↳ astro-ph.COhep-phhep-th3 citations
13. 13*

    Search for ultralight bosons in Cygnus X-1 with Advanced LIGO

    Ling Sun🇺🇸 · Richard Brito🇮🇹 · Maximiliano Isi🇺🇸

    Ultralight scalars, if they exist as theorized, could form clouds around rapidly rotating black holes. Such clouds are expected to emit continuous, quasimonochromatic gravitational waves that could be detected by LIGO and Virgo. Here we present results of a directed search for such signals from the Cygnus X-1 binary, using data from Advanced LIGO's second observing run. We find no evidence of gravitational waves in the 250-750 Hz band. Without incorporating existing measurements of the Cygnus X-1 black hole spin, our results disfavor boson masses in $6.4\le \mu /(10^{-13}\mathrm{eV})\le 8.0$, assuming that the black hole was born $5\times 10^6$ years ago with a nearly-extremal spin. We then focus on a string axiverse scenario, in which self-interactions enable a cloud for high black-hole spins consistent with measurements for Cygnus X-1. In that model, we constrain the boson masses in $9.6\le \mu /(10^{-13}\mathrm{eV})\le 15.5$ for a decay constant $f_a\sim 10^{15}$ GeV. Future application of our methods to other sources will yield improved constraints.

    ↳ gr-qcastro-ph.HEhep-phPRD(2020)·101 citations
14. 14*

    Recent progress on hypernuclei

    Avraham Gal🇮🇱

    Some of last year's progress made in hypernuclear physics is reviewed as follows: (i) resolving the ${}_{\Lambda }^5$He overbinding problem in single-$\Lambda$ hypernuclei [1]; (ii) arguing that the onset of binding double-$\Lambda$ hypernuclei is most likely at $A$=5, with the neutral systems ${}_{\Lambda \Lambda }^3$n and ${}_{\Lambda \Lambda }^4$n unbound by a large margin [2]; and (iii) revising the calculated value of the loosely bound ${}_{\Lambda }^3$H lifetime to a level of $\sim$20% shorter than the free $\Lambda$ lifetime [3], given recent claims from relativistic heavy ion experiments that $\tau {(}_{\Lambda }^3$H) is shorter than ${\tau }_{\Lambda }$ by as much as $\approx$(30$\pm$8)%. Also discussed briefly in this context is the lifetime expected for the questionable ${}_{\Lambda }^3$n hypernucleus.

    ↳ nucl-thhep-phnucl-exJ.Phys.Conf.Ser.(2020)·3 citations
15. 15*

    Lattice investigation of the phase diagram of the 1+1 dimensional Gross-Neveu model at finite number of fermion flavors

    Laurin Pannullo🇩🇪 · Julian Lenz🇩🇪 · Marc Wagner🇩🇪 · Björn Wellegehausen🇩🇪 · Andreas Wipf🇩🇪

    We explore the phase structure of the 1+1 dimensional Gross-Neveu model at finite number of fermion flavors using lattice field theory. Besides a chirally symmetric phase and a homogeneously broken phase we find evidence for the existence of an inhomogeneous phase, where the condensate is a spatially oscillating function. Our numerical results include a crude $\mu$-$T$ phase diagram.

    ↳ hep-lathep-phPoS(2019)·11 citations
16. 16*

    Chiral kinetic theory from Landau level basis

    Shu Lin🇨🇳 · Lixin Yang🇨🇳

    We derive a chiral kinetic theory with Landau level basis, which is valid for slow-varying magnetic field with arbitrary magnitude. We apply the new chiral kinetic theory to calculate the electric conductivity transverse to the magnetic field in a magnetized QED and QCD plasma. Under the lowest Landau level approximation and relaxation time approximation, we find the transverse conductivity approaches a constant in the large magnetic field limit and is inversely proportional to the relaxation time. We also obtain a frequency-dependent transverse conductivity in response to a time-dependent electric field. We find a high frequency enhancement in this conductivity.

    ↳ nucl-thcond-mat.mes-hallhep-phPRD(2020)·39 citations
17. 17*

    Dark Fermions and Spontaneous $CP$ violation in $SU(2)$-axion Inflation

    Azadeh Maleknejad🇩🇪

    Remarkably, if $CP$ was spontaneously broken in the physics of inflation, fermions would notice and remember it. Based on that, we present a new (non-thermal) mechanism for generating self-interacting dark Dirac fermions prior to the Hot Big Bang. The non-Abelian gauge fields and axions are well-motivated matter contents for the particle physics of inflation. In this background, we analytical study Dirac fermion doublets charged under the $SU(2)$ gauge field and use point-splitting technique to regularize the currents. We show that the non-trivial $CP$-violating vacuum structure of $SU(2)$-axion models naturally leads to an efficient mechanism for generating massive fermions during inflation. The size of the fermionic backreaction and the density fraction of dark fermions put upper bounds on the fermion's mass. For a GUT scale inflation, the generated dark fermions, only gravitationally coupled to the visible sector, can be as heavy as $m\lesssim 10TeV$.

    ↳ hep-thastro-ph.COgr-qchep-phJHEP(2020)·27 citations
18. 18*

    The mean transverse momentum of ultracentral heavy-ion collisions: A new probe of hydrodynamics

    Fernando G. Gardim🇧🇷 · Giuliano Giacalone🇫🇷 · Jean-Yves Ollitrault🇫🇷

    We predict that the mean transverse momentum of charged hadrons $⟨p_t⟩$ rises as a function of the charged-particle multiplicity in ultracentral nucleus-nucleus collisions. We explain that this phenomenon has a simple physical origin and represents an unambiguous prediction of the hydrodynamic framework of heavy-ion collisions. We argue that the relative increase of $⟨p_t⟩$ is proportional to the speed of sound squared $c_s^2$ of the quark-gluon plasma. Based on the value of $c_s^2$ from lattice QCD, we expect $⟨p_t⟩$ to increase by approximately $18$ MeV between 1\% and 0.001\% centrality in Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV.

    ↳ nucl-thhep-phnucl-exPLB(2020)·64 citations
19. 19*

    The Large-Misalignment Mechanism for the Formation of Compact Axion Structures: Signatures from the QCD Axion to Fuzzy Dark Matter

    Asimina Arvanitaki🇨🇦 · Savas Dimopoulos🇺🇸 · Marios Galanis🇺🇸 · Luis Lehner🇨🇦 · Jedidiah O. Thompson🇺🇸 · Ken Van Tilburg🇺🇸

    Axions are some of the best motivated particles beyond the Standard Model. We show how the attractive self-interactions of dark matter (DM) axions over a broad range of masses, from $10^{-22}$ eV to $10^7$ GeV, can lead to nongravitational growth of density fluctuations and the formation of bound objects. This structure formation enhancement is driven by parametric resonance when the initial field misalignment is large, and it affects axion density perturbations on length scales of order the Hubble horizon when the axion field starts oscillating, deep inside the radiation-dominated era. This effect can turn an otherwise nearly scale-invariant spectrum of adiabatic perturbations into one that has a spike at the aforementioned scales, producing objects ranging from dense DM halos to scalar-field configurations such as solitons and oscillons. We call this class of cosmological scenarios for axion DM production "the large-misalignment mechanism." We explore observational consequences of this mechanism for axions with masses up to $10$ eV. For axions heavier than $10^{-5}$ eV, the compact axion halos are numerous enough to significantly impact Earth-bound direct detection experiments, yielding intermittent but coherent signals with repetition rates exceeding one per decade and crossing times less than a day. These episodic increases in the axion density and kinematic coherence suggest new approaches for axion DM searches, including for the QCD axion. Dense structures made up of axions from $10^{-22}$ eV to $10^{-5}$ eV are detectable through gravitational lensing searches, and their gravitational interactions can also perturb baryonic structures and alter star formation. At very high misalignment amplitudes, the axion field can undergo self-interaction-induced implosions long before matter-radiation equality, producing potentially-detectable low-frequency stochastic gravitational waves.

    ↳ astro-ph.COhep-phhep-thPRD(2020)·254 citations
20. 20*

    Lighting the Dark: The Evolution of the Post-Inflationary Universe

    Nathan Musoke🇳🇿 · Shaun Hotchkiss🇳🇿 · Richard Easther🇳🇿

    In simple inflationary cosmological scenarios the near-exponential growth can be followed by a long period in which the Universe is dominated by the oscillating inflaton condensate. The condensate is initially almost homogeneous, but perturbations grow gravitationally, eventually fragmenting the condensate if it is not disrupted more quickly by resonance or prompt reheating. We show that the gravitational fragmentation of the condensate is well-described by the Schrödinger-Poisson equations and use numerical solutions to show that large overdensities form quickly after the onset of nonlinearity. This is the first exploration of this phase of nonlinear dynamics in the very early universe, which can affect the detailed form of the inflationary power spectrum and the dark matter fraction when the dark sector is directly coupled to the inflaton.

    ↳ astro-ph.COhep-phhep-thPRL(2020)·69 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.