Wed·Apr 15, 2020Wednesday·April 15, 2020

1. 01*

   Signal-background interference for digluon resonances at the Large Hadron Collider

   Prudhvi N. Bhattiprolu🇺🇸 · Stephen P. Martin🇺🇸

   We study the interference between the amplitudes for $gg\to X\to gg$, where $X$ is a new heavy digluon resonance, and the QCD background $gg\to gg$, at the Large Hadron Collider. The interference produces a large low-mass tail and a deficit of events above the resonance mass, compared to the naive pure resonance peak. For a variety of different resonance quantum numbers and masses, we evaluate the signal-background interference contribution at leading order, including showering, hadronization, and detector effects. The resulting new physics dijet mass distribution may have a shape that appears, after QCD background fitting and subtraction, to resemble an enhanced peak, a shelf, a peak/dip, or even a pure dip. We argue that the true limits on new digluon resonances are likely to differ significantly from the limits obtained when interference is neglected, especially if the branching ratio to $gg$ is less than 1.

   hep-phhep-exPRD(2020)·5 citations
2. 02*

   Particle productions and anisotropic flows from the AMPT model for Cu+Au collisions at $\sqrt{s_{NN}}=200$ GeV

   Yuncun He🇨🇳 · Zi-Wei Lin🇺🇸

   We use the string melting version of a multi-phase transport (AMPT) model to study Cu+Au collisions at $\sqrt{s_{NN}}=200$ GeV. The rapidity distributions of identified hadrons show asymmetric dependences on rapidity. In addition, elliptic and triangular flows at mid-rapidity from the AMPT model for pions, kaons, and protons agree reasonably with the experimental data up to $p_T\sim 1$ GeV$/c$. We then investigate the forward/backward asymmetry of $v_2$ and $v_3$. We find that these anisotropic flows are larger on the Au-going side than the Cu-going side, while the asymmetry tends to go away in very peripheral collisions. We also make predictions on transverse momentum spectra of identified hadrons and longitudinal decorrelations of charged particles, where the average decorrelation of elliptic flow in asymmetric Cu+Au collisions is found to be stronger than that in Au+Au collisions.

   hep-phnucl-thEPJA(2020)·10 citations
3. 03*

   Anomalous magnetohydrodynamics with constant anisotropic electric conductivities

   Ren-jie Wang🇨🇳 · Patrick Copinger🇯🇵 · Shi Pu🇨🇳

   We study anomalous magnetohydrodynamics in a longitudinal boost invariant Bjorken flow with constant anisotropic electric conductivities as outlined in Ref. [1]. For simplicity, we consider a neutral fluid and a force-free magnetic field in the transverse direction. We derived analytic solutions of the electromagnetic fields in the laboratory frame, the chiral density, and the energy density as functions of proper time.

   hep-phnucl-thNPA(2021)·16 citations
4. 04*

   Vacuum polarization contribution to muon $g-2$ as an inverse problem

   Hsiang-nan Li🇹🇼 · Hiroyuki Umeeda🇹🇼

   We analyze the electromagnetic current correlator at an arbitrary photon invariant mass $q^2$ by exploiting its associated dispersion relation. The dispersion relation is turned into an inverse problem, via which the involved vacuum polarization function $\Pi (q^2)$ at low $q^2$ is solved with the perturbative input of $\Pi (q^2)$ at large $q^2$. It is found that the result for $\Pi (q^2)$, including its first derivative ${\Pi }^{\prime }(q^2=0)$, agrees with those from lattice QCD, and its imaginary part accommodates the $e^{+}{e}^{-}$ annihilation data. The corresponding hadronic vacuum polarization contribution $a_{\mu }^{\mathrm{HVP}}=(641_{-63}^{+65})\times 10^{-10}$ to the muon anomalous magnetic moment $g-2$, where the uncertainty arises from the variation of the perturbative input, also agrees with those obtained in other phenomenological and theoretical approaches. We point out that our formalism is equivalent to imposing the analyticity constraint to the phenomenological approach solely relying on experimental data, and can improve the precision of the $a_{\mu }^{\mathrm{HVP}}$ determination in the Standard Model.

   hep-phPRD(2020)·13 citations
5. 05*

   About calculation of massless and massive Feynman integrals

   A. V. Kotikov🇷🇺

   We report some results of calculations of massless and massive Feynman integrals particularly focusing on difference equations for coefficients of for their series expansions

   hep-phhep-thParticles(2020)·7 citations
6. 06*

   The role of right-handed neutrinos in $b\to c\tau \bar{\nu }$ anomalies

   Rusa Mandal🇩🇪 · Clara Murgui🇪🇸 · Ana Peñuelas🇪🇸 · Antonio Pich🇪🇸

   Motivated by the persistent anomalies reported in the $b\to c\tau \bar{\nu }$ data, we perform a general model-independent analysis of these transitions, in the presence of light right-handed neutrinos. We adopt an effective field theory approach and write a low-energy effective Hamiltonian, including all possible dimension-six operators. The corresponding Wilson coefficients are determined through a numerical fit to all available experimental data. In order to work with a manageable set of free parameters, we define eleven well-motivated scenarios, characterized by the different types of new physics that could mediate these transitions, and analyse which options seem to be preferred by the current measurements. The data exhibit a clear preference for new-physics contributions, and good fits to the data are obtained in several cases. However, the current measurement of the longitudinal $D^{\ast }$ polarization in $B\to D^{\ast }\tau \bar{\nu }$ cannot be easily accommodated within its experimental $1\sigma$ range. A general analysis of the three-body $B\to D\tau \bar{\nu }$ and four-body $B\to D^{\ast }(\to D\pi )\tau \bar{\nu }$ angular distributions is also presented. The accessible angular observables are studied in order to assess their sensitivity to the different new physics scenarios. Experimental information on these distributions would help to disentangle the dynamical origin of the current anomalies.

   hep-phJHEP(2020)·82 citations
7. 07*

   Dark Matter Freeze Out during an Early Cosmological Period of QCD Confinement

   Dillon Berger🇺🇸 · Seyda Ipek🇺🇸 · Tim M.P. Tait🇺🇸 · Michael Waterbury🇺🇸

   Standard lore states that there is tension between the need to accommodate the relic density of a weakly interacting massive particle and direct searches for dark matter. However, the estimation of the relic density rests on an extrapolation of the cosmology of the early Universe to the time of freeze out, untethered by observations. We explore a nonstandard cosmology in which the strong coupling constant evolves in the early Universe, triggering an early period of QCD confinement at the time of freeze out. We find that depending on the nature of the interactions between the dark matter and the Standard Model, freeze out during an early period of confinement can lead to drastically different expectations for the relic density, allowing for regions of parameter space which realize the correct abundance but would otherwise be excluded by direct searches.

   hep-phJHEP(2020)·24 citations
8. 08*

   Probing the predictions of an orbifold theory of flavor

   Francisco J. de Anda🇲🇽 · Newton Nath🇲🇽 · José W. F. Valle🇪🇸 · Carlos A. Vaquera-Araujo🇲🇽

   We examine the implications of a recently proposed theory of fermion masses and mixings in which an $A_4$ family symmetry emerges from orbifold compactification. We analyse two variant schemes concerning their predictions for neutrino oscillations, neutrinoless double-beta decay and the golden quark-lepton unification mass relation. We find that upcoming experiments DUNE as well as LEGEND and nEXO offer good chances of exploring a substantial region of neutrino parameters.

   hep-phPRD(2020)·10 citations
9. 09*

   Spherically symmetric static black holes in Einstein-aether theory

   Chao Zhang🇺🇸 · Xiang Zhao🇺🇸 · Kai Lin🇨🇳 · Shaojun Zhang🇨🇳 · Wen Zhao🇨🇳 · Anzhong Wang🇺🇸

   In this paper, we systematically study spherically symmetric static spacetimes in the framework of Einstein-aether theory, and pay particular attention to the existence of black holes (BHs). In the present studies we first clarify several subtle issues. In particular, we find that, out of the five non-trivial field equations, only three are independent, so the problem is well-posed, as now generically there are only three unknown functions, {$F(r),B(r),A(r)$, where $F$ and $B$ are metric coefficients, and $A$ describes the aether field.} In addition, the two second-order differential equations for $A$ and $F$ are independent of $B$, and once they are found, $B$ is given simply by an algebraic expression of $F,A$ and their derivatives. To simplify the problem further, we explore the symmetry of field redefinitions, and work first with the redefined metric and aether field, and then obtain the physical ones by the inverse transformations. These clarifications significantly simplify the computational labor, which is important, as the problem is highly involved mathematically. In fact, it is exactly because of these, we find various numerical BH solutions with an accuracy that is at least two orders higher than previous ones. More important, these BH solutions are the only ones that satisfy the self-consistent conditions and meantime are consistent with all the observational constraints obtained so far. The locations of universal horizons are also identified, together with several other observationally interesting quantities, such as the innermost stable circular orbits (ISCO), the ISCO frequency, and the maximum redshift $z_{max}$ of a photon emitted by a source orbiting the ISCO. All of these quantities are found to be quite close to their relativistic limits.

   ↳ gr-qcastro-ph.GAhep-phhep-thPRD(2020)·37 citations
10. 10*

    Technical Comment on "The dark matter interpretation of the 3.5-keV line is inconsistent with blank-sky observations"

    Kevork N. Abazajian🇺🇸

    I show that model dependencies in the analysis by Dessert, Rodd & Safdi (2020) relax their claimed constraint by a factor of ~20. After including conservative model choices, the derived limits are comparable to or slightly better than limits from previous searches. Further model tests and expansion of the data energy may enhance or relax sensitivity of the methodology.

    ↳ astro-ph.HEhep-ph30 citations
11. 11*

    Hadron resonance gas with van der Waals interactions

    Volodymyr Vovchenko🇩🇪

    An overview of a hadron resonance gas (HRG) model that includes van der Waals interactions between hadrons is presented. Applications of the excluded volume HRG model to heavy-ion collision data and lattice QCD equation of state are discussed. A recently developed quantum van der Waals hadron resonance gas model is covered as well. Applications of this model in the context of the QCD critical point are elaborated.

    ↳ nucl-thhep-phIJMPE(2020)·32 citations
12. 12*

    Ekpyrotic Cosmology with a Zero-Shear S-Brane

    Robert Brandenberger🇨🇦 · Ziwei Wang (McGill University)🇨🇦

    In a recent paper we proposed a mechanism for a continuous transition between a contracting Ekpyrotic phase and the Standard Big Bang phase of expansion: the bounce is generated by an S-brane which represents the effects of higher mass string states in the low energy effective field theory. We showed that gravitational waves on cosmological scales obtain a nearly scale-invariant spectrum. Here, we study the cosmological fluctuations in this setup, assuming that the S-brane has zero shear. We find a nearly scale-invariant spectrum of cosmological perturbations with a slight red tilt. The scenario yields two consistency relations for cosmological observations, the first one relating the tensor to scalar ratio with the scalar spectral tilt, the second relating the tensor tilt to the scalar tilt. The predicted tensor to scalar ratio is within the reach of upcoming CMB observations. The tensor tilt is blue.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2020)·37 citations
13. 13*

    Fast radio bursts from axion stars moving through pulsar magnetospheres

    James H. Buckley🇺🇸 · P. S. Bhupal Dev🇺🇸 · Francesc Ferrer🇺🇸 · Fa Peng Huang🇺🇸

    We study the radio signals generated when an axion star enters the magnetosphere of a neutron star. As the axion star moves through the resonant region where the plasma-induced photon mass becomes equal to the axion mass, the axions can efficiently convert into photons, giving rise to an intense, transient radio signal. We show that a dense axion star with a mass $\sim 10^{-13}{M}_{\odot }$ composed of $\sim 10\mu$eV axions can account for most of the mysterious fast radio bursts.

    ↳ astro-ph.HEhep-phPRD(2021)·76 citations
14. 14*

    Neutrino Long-Baseline Experiments and Nuclear Physics

    Ulrich Mosel🇩🇪

    The extraction of neutrino properties from long-baseline experiments such as T2K, NOvA and DUNE requires a good description of the initial neutrino-nucleon interaction. Since the targets in all running or planned experiments are nuclei (C12, O16, Ar40) the extraction also requires a reliable description of nuclear structure and nuclear reactions that become essential during the final state interactions of the neutrino-nucleus reactions. This article presents a short introduction into these problems for a non-expert readership. It also stresses that a generator that implements state-of-the-art methods of nuclear structure and reactions is still needed for these state-of-the-art experiments.

    ↳ nucl-thhep-exhep-phnucl-exNucl.Phys.News(2019)·0 citations
15. 15*

    Technical comment on the paper of Dessert et al. "The dark matter interpretation of the 3.5 keV line is inconsistent with blank-sky observations"

    Alexey Boyarsky🇳🇱 · Denys Malyshev🇩🇪 · Oleg Ruchayskiy🇩🇰 · Denys Savchenko🇺🇦

    An unidentified line at energy around 3.5 keV was detected in the spectra of dark matter-dominated objects. Recent work of Dessert et al. [1812.06976] used 30 Msec of XMM-Newton blank-sky observations to constrain the admissible line flux, challenging its dark matter decay origin. We demonstrate that these bounds are overestimated by more than an order of magnitude due to improper background modeling. Therefore the dark matter interpretation of the 3.5 keV signal remains viable.

    ↳ astro-ph.COastro-ph.HEhep-ph36 citations
16. 16*

    Dynamics from symmetries in chiral $SU(N)$ gauge theories

    Stefano Bolognesi🇮🇹 · Kenichi Konishi🇮🇹 · Andrea Luzio🇮🇹

    The symmetries and dynamics of simple chiral $SU(N)$ gauge theories, with matter Weyl fermions in a two-index symmetric tensor and $N+4$ anti-fundamental representations, are examined, by taking advantage of the recent developments involving the ideas of generalized symmetries, gauging of discrete center 1-form symmetries and mixed 't Hooft anomalies. This class of models are particularly interesting because the conventional 't Hooft anomaly matching constraints allow a chirally symmetric confining vacuum, with no condensates breaking the $U(1)\times SU(N+4)$ flavor symmetry, and with certain set of massless baryonlike composite fermions saturating all the associated anomaly triangles. Our calculations show that in such a vacuum the UV-IR matching of some $0$-form$-$$1$-form mixed 't Hooft anomalies fails. This implies, for the theories with even $N$ at least, that a chirally symmetric confining vacuum contemplated earlier in the literature actually cannot be realized dynamically. In contrast, a Higgs phase characterized by some gauge-noninvariant bifermion condensates passes our improved scrutiny.

    ↳ hep-thhep-lathep-phJHEP(2020)·51 citations
17. 17*

    Searching for General Binary Inspirals with Gravitational Waves

    Horng Sheng Chia🇳🇱 · Thomas D. P. Edwards🇳🇱

    We study whether binary black hole template banks can be used to search for the gravitational waves emitted by general binary coalescences. To recover binary signals from noisy data, matched-filtering techniques are typically required. This is especially true for low-mass systems, with total mass $M\lesssim 10M_{\odot }$, which can inspiral in the LIGO and Virgo frequency bands for thousands of cycles. In this paper, we focus on the detectability of low-mass binary systems whose individual components can have large spin-induced quadrupole moments and small compactness. The quadrupole contributes to the phase evolution of the waveform whereas the compactness affects the merger frequency of the binary. We find that binary black hole templates (with dimensionless quadrupole $\kappa =1$) cannot be reliably used to search for objects with large quadrupoles ($\kappa \gtrsim 20$) over a wide range of parameter space. This is especially true if the general object is highly spinning and has a larger mass than its binary companion. A binary that consists of objects with small compactness could merge in the LIGO and Virgo frequency bands, thereby reducing its accumulated signal-to-noise ratio during the inspiraling regime. Template banks which include these more general waveforms must therefore be constructed. These extended banks would allow us to realistically search for the existence of new astrophysical and beyond the Standard Model compact objects.

    ↳ astro-ph.HEastro-ph.IMgr-qchep-ph+1JCAP(2020)·32 citations
18. 18*

    Modeling Dark Photon Oscillations in Our Inhomogeneous Universe

    Andrea Caputo🇪🇸 · Hongwan Liu🇺🇸 · Siddharth Mishra-Sharma🇺🇸 · Joshua T. Ruderman🇺🇸

    A dark photon may kinetically mix with the Standard Model photon, leading to observable cosmological signatures. The mixing is resonantly enhanced when the dark photon mass matches the primordial plasma frequency, which depends sensitively on the underlying spatial distribution of electrons. Crucially, inhomogeneities in this distribution can have a significant impact on the nature of resonant conversions. We develop and describe, for the first time, a general analytic formalism to treat resonant oscillations in the presence of inhomogeneities. Our formalism follows from the theory of level crossings of random fields and only requires knowledge of the one-point probability distribution function (PDF) of the underlying electron number density fluctuations. We validate our formalism using simulations and illustrate the photon-to-dark photon conversion probability for several different choices of PDFs that are used to characterize the low-redshift Universe.

    ↳ astro-ph.COhep-phPRD(2020)·66 citations
19. 19*

    Influence of centrality definition and detector efficiency on the net-proton kurtosis

    Sukanya Sombun🇹🇭 · Jan Steinheimer🇩🇪 · Christoph Herold🇹🇭 · Ayut Limphirat🇹🇭 · Yupeng Yan🇹🇭 · Marcus Bleicher🇩🇪

    We study the influence of the centrality definition and detector efficiency on the net-proton kurtosis for minimum bias Au+Au collisions at a beam energy of $\sqrt{s_{\mathrm{NN}}}=7.7$ GeV by using the UrQMD model. We find that different ways of defining the centrality lead to different cumulant ratios. Moreover, we demonstrate that the kurtosis is suppressed for central collisions when a wider transverse momentum acceptance is used. Finally, the influence of a detector efficiency on the measured cumulant ratios is estimated.

    ↳ nucl-thhep-phSpringer Proc.Phys.(2020)·0 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.