Wed·Aug 28, 2019Wednesday·August 28, 2019

1. 01*

   Dark matter from dark photons: a taxonomy of dark matter production

   Thomas Hambye🇧🇪 · Michel H.G. Tytgat🇧🇪 · Jérôme Vandecasteele🇧🇪 · Laurent Vanderheyden🇧🇪

   We analyse how dark matter (DM) can be produced in the early universe, working in the framework of a hidden sector charged under a U(1)' gauge symmetry and interacting with the Standard Model through kinetic mixing. Depending on the masses of the dark matter particle and of the dark photon, as well as on the hidden U(1)' gauge coupling and the kinetic mixing parameter, we classify all the distinct regimes along which the observed dark matter relic density can be accounted for. We find that 9 regimes are potentially operative to produce the DM particles and this along 5 distinct dynamical mechanisms. Among these, 4 regimes are new and correspond to regimes in which the DM particles are produced by on-shell dark photons. One of them proceeds along a new dynamical mechanism, which we dub sequential freeze-in. We argue that such regimes and the associated dynamical mechanisms are characteristic of DM models for which, on top of the Standard Model and the dark sector, there are other massive, but relatively light particles -- akin to the dark photon -- that interact both with the SM and the DM sectors.

   hep-phPRD(2019)·109 citations
2. 02*

   Kinetic Equilibration after Preheating

   Robert Brandenberger🇨🇦 · Ryo Namba🇨🇦 · Rudnei O. Ramos🇧🇷

   We study thermal equilibration after preheating in inflationary cosmology, which is an important step towards a comprehensive understanding of cosmic thermal history. By noticing that the problem is parallel to thermalization after a relativistic heavy ion collision, we make use of the methods developed in this context and that seek for an analytical approach to the Boltzmann equation. In particular, an exact solution for number-conserving scatterings is available for the distribution function in a Friedmann-Lemaître-Robertson-Walker metric and can be utilized for the spectral evolution of kinetic equilibration process after preheating. We find that thermal equilibration is almost instantaneous on the time scale of the Hubble time. We also make an explicit prediction for the duration (the number of e-folds of expansion) required for this process of thermal equilibration to complete following the end of inflation.

   hep-phastro-ph.COgr-qchep-th4 citations
3. 03*

   MeV neutrino dark matter: Relic density, lepton flavour violation and electron recoil

   J. Fiaschi🇩🇪 · M. Klasen🇩🇪 · M. Vargas🇩🇪 · C. Weinheimer🇩🇪 · S. Zeinstra🇩🇪

   Right-handed neutrinos with MeV to GeV mass are very promising candidates for dark matter (DM). Not only can they solve the missing satellite puzzle, the cusp-core problem of inner DM density profiles, and the too-big-to fail problem, {\it i.e.} that the unobserved satellites are too big to not have visible stars, but they can also account for the Standard Model (SM) neutrino masses at one loop. We perform a comprehensive study of the right-handed neutrino parameter space and impose the correct observed relic density and SM neutrino mass differences and mixings. We find that the DM masses are in agreement with bounds from big-bang nucleosynthesis, but that these constraints induce sizeable DM couplings to the charged SM leptons. We then point out that previously overlooked limits from current and future lepton flavour violation experiments such as MEG and SINDRUM heavily constrain the allowed parameter space. Since the DM is leptophilic, we also investigate electron recoil as a possible direct detection signal, in particular in the XENON1T experiment. We find that despite the large coupling and low backgrounds, the energy thresholds are still too high and the predicted cross sections too low due to the heavy charged mediator, whose mass is constrained by LEP limits.

   hep-phhep-exJHEP(2019)·7 citations
4. 04*

   TVID 2: Evaluation of planar-type three-loop self-energy integrals with arbitrary masses

   Stefan Bauberger🇩🇪 · Ayres Freitas🇺🇸 · Daniel Wiegand🇺🇸

   We present TVID 2, a program to numerically evaluate an important class of planar three-loop self-energy master integrals with arbitrary masses. As with the predecessor version (TVID 1) the integrals are separated into a known piece, containing the UV divergencies, and a finite piece that is integrated numerically, implemented in C. The set of master integrals under consideration was found with self-energy diagrams containing two closed fermion loops in mind. Two techniques are employed in deriving the expressions for the finite pieces that are then numerically integrated: (a) Sub-loop dispersion relations in the case of topologies containing sub-bubbles, and (b) a modification of the procedure suggested by Ghinculov for integrals with only sub-loop triangles.

   hep-phhep-thJHEP(2020)·23 citations
5. 05*

   Quadrupole moments of baryons

   A. J. Buchmann🇩🇪 · E. M. Henley🇺🇸

   Quadrupole moments of decuplet baryons and the octet-decuplet transition quadrupole moments are calculated using Morpurgo's general QCD parameterization method. Certain relations among the decuplet and the octet to decuplet transition quadrupole moments are derived. These can be used to predict the $\Delta$ quadrupole moments which are difficult to measure.

   hep-phnucl-thPRD(2002)·64 citations
6. 06*

   Higher-Order Corrections to Higgs Boson Amplitudes with Full Quark Mass Dependence in Quantum Chromodynamics

   Dominik Kara🇨🇭

   In this thesis, higher-order corrections to the perturbative expansions of scattering amplitudes involving the Higgs boson in the framework of Quantum Chromodynamics are evaluated, where we focus on processes that are mediated through heavy-quark loops. First, we derive the third-order corrections to the form factor describing the Yukawa coupling of a Higgs boson to a pair of bottom quarks. Furthermore, we compute the two-loop corrections to the $H\to Z\gamma$ decay width by retaining the full dependence on the internal quark mass. Finally, we describe the calculation of the planar Master Integrals relevant to the two-loop amplitude for Higgs-plus-jet production with full quark mass dependence. We accomplish this by establishing a method to derive series expansions from differential equations, since the set of Master Integrals involves elliptic structures.

   hep-ph1 citation
7. 07*

   $B$-meson light-cone distribution amplitude from the Euclidean quantity

   Wei Wang🇨🇳 · Yu-Ming Wang🇨🇳 · Ji Xu🇨🇳 · Shuai Zhao🇺🇸

   A new method for the model-independent determination of the light-cone distribution amplitude (LCDA) of the $B$-meson in heavy quark effective theory (HQET) is proposed by combining the large momentum effective theory (LaMET) and the numerical simulation technique on the Euclidean lattice. We demonstrate the autonomous scale dependence of the non-local quasi-HQET operator with the aid of the auxiliary field approach, and further determine the perturbative matching coefficient entering the hard-collinear factorization formula for the $B$-meson quasi-distribution amplitude at the one-loop accuracy. These results will be crucial to explore the partonic structure of heavy-quark hadrons in the static limit and to improve the theory description of exclusive $B$-meson decay amplitudes based upon perturbative QCD factorization theorems.

   hep-phhep-exhep-latPRD(2020)·84 citations
8. 08*

   Lorentz-violating matter-gravity couplings in small-eccentricity binary pulsars

   Lijing Shao🇨🇳

   Lorentz symmetry is an important concept in modern physics. Precision pulsar timing was used to put tight constraints on the coefficients for Lorentz violation in the pure-gravity sector of the Standard-Model Extension (SME). We extend the analysis to Lorentz-violating matter-gravity couplings, utilizing three small-eccentricity relativistic neutron star (NS) -- white dwarf (WD) binaries. We obtain compelling limits on various SME coefficients related to the neutron, the proton, and the electron. These results are complementary to limits obtained from lunar laser ranging and clock experiments.

   hep-phastro-ph.HEgr-qcSymmetry(2019)·11 citations
9. 09*

   Contribution of the chiral vortical effect to the evolution of the hypermagnetic field and the matter-antimatter asymmetry in the early Universe

   S. Abbaslu🇮🇷 · S. Rostam Zadeh🇮🇷 · S. S. Gousheh🇮🇷

   In this paper, we study the contribution of the chiral vortical effect, in addition to that of the chiral magnetic effect, to the evolution of the hypermagnetic field and the matter-antimatter asymmetry in the symmetric phase of the early Universe in the temperature range 100GeV < T < 10TeV. We choose a fully helical Chern-Simons wave configuration for the velocity and the hypermagnetic vector potential fields. The latter makes the plasma force-free in the absence of viscosity. We show that the most pronounced effect of the chiral vorticity is the production and initial growth of the hypermagnetic field. In particular, we show that in the presence of a non-zero matter asymmetry, the hypermagnetic field can grow from zero initial value only in the presence of a non-zero vorticity field. Moreover, we show that larger initial growths not only result in larger maximum values of the hypermagnetic field, but also cause the saturation of the hypermagnetic field and the conversion of the lepton-baryon asymmetry to occur more quickly, i.e., at a higher temperature. We show that the damping of the vorticity due to the presence of viscosity, which typically occurs extremely rapidly, does not significantly affect the evolution.

   hep-phPRD(2019)·14 citations
10. 10*

    On the Charge Dependence of the Pion-Nucleon Coupling Constant and Nucleon-Nucleon Low-Energy Scattering Parameters

    V. A. Babenko🇺🇦 · N. M. Petrov🇺🇦

    The simple model describing charge independence and charge symmetry breaking of the pion-nucleon coupling constant is proposed. The model, which has simple physical meaning and foundation, suggests directly proportional dependence of the pion-nucleon coupling constants on the masses of interacting nucleons and pions. Charge dependence of the pion-nucleon coupling constant and the ${}^1{S}_0$-state low-energy nucleon-nucleon ($NN$) scattering parameters are studied on the basis of the Yukawa meson theory. The values of the $np$ and $nn$ interaction characteristics calculated by the proposed model agree quite well with the experimental data.

    hep-phnucl-th0 citations
11. 11*

    Role of higher twist effects in diffractive DIS and determination of diffractive parton distribution functions

    Atefeh Maktoubian🇮🇷 · Hossein Mehraban🇮🇷 · Hamzeh Khanpour🇮🇷 · Muhammad Goharipour🇮🇷

    The current analysis aims to present the results of a QCD analysis of diffractive parton distribution functions (diffractive PDFs) at next-to-leading order (NLO) accuracy in perturbative QCD. In this new determination of diffractive PDFs, we use all available and up-to-date diffractive deep inelastic scattering (diffractive DIS) datasets from H1 and ZEUS Collaborations at HERA including the most recent H1/ZEUS combined measurements. In this analysis, we consider the heavy quark contributions to the diffractive DIS in the so-called framework of {\tt FONLL} general mass variable flavor number scheme (GM-VFNS). The uncertainties on the diffractive PDFs are calculated using the standard "Hessian error propagation" which served to provide a more realistic estimate of the uncertainties. This analysis are enriched, for the first time, by including the nonperturbative higher twist (HT) effects in the calculation of diffractive DIS cross sections which are particularly important at large-$x$ and low $Q^2$ regions. Then, the stability and reliability of the extracted diffractive PDFs are investigated upon inclusion of HT effects. We discuss the novel aspects of the approach used in this QCD fit, namely, optimized and flexible parameterizations of diffractive PDFs, the inclusion of HT effects, and considering the recent H1/ZEUS combined dataset. Finally, we present the extracted diffractive PDFs with and without the presence of HT effects, and discuss the fit quality and the stability upon variations of the kinematic cuts and the fitted datasets. We show that the inclusion of HT effects in diffractive DIS can improve the description of the data which leads, in general, to a very good agreement between data and theory predictions.

    hep-phhep-exPRD(2019)·12 citations
12. 12*

    Cluster reducibility of multiquark operators

    Wolfgang Lucha🇦🇹 · Dmitri Melikhov🇦🇹 · Hagop Sazdjian🇫🇷

    It is shown that the multiquark gauge-invariant operators can, in general, be decomposed into combinations of products of ordinary hadronic operators, exhibiting their cluster reducibility. The latter property inhibits the formation of completely compact multiquark bound states. Multiquark operators still play a crucial role in the description of exotic states in regions of configuration space where the hadronic clusters are close to each other. Our proof gives a foundation for a unified viewpoint, where the multiquark-type and the molecular-type approaches play complementary roles, at the gauge-invariant nonlocal operator level.

    hep-phPRD(2019)·14 citations
13. 13*

    One loop Volkov propagator in the Lorentz class of gauges

    Martin Lavelle🇬🇧 · David McMullan🇬🇧

    We calculate the ultraviolet divergences in a weak field expansion of the Volkov propagator. This is done for the full Lorentz class of gauges. The expected gauge invariance of the vacuum mass shift in each sideband is recovered. However, the renormalisation of the background induced mass shift is shown to be gauge dependent. In particular, we show that it vanishes in Landau gauge. We find that only in that gauge does the vacuum renormalisation remove all ultraviolet divergences.

    hep-phhep-thPLB(2019)·3 citations
14. 14*

    Light-front wave functions of mesons, baryons and pentaquarks, with topology-induced local 4-quark interaction

    Edward Shuryak🇺🇸

    We calculate light-front wave functions of mesons, baryons and pentaquarks in a model including constituent mass (representing chiral symmetry breaking), harmonic confining potential, and 4-quark local interaction of 't Hooft type. The model is a simplified version of that used by Jia and Vary. The method used is numerical diagonalization of the Hamiltonian matrix, with certain functional basis. We found that the nucleon wave function displays strong diquar correlations, unlike that for Delta (decuplet) baryon. We also calculate 3-quark-5-quark admixture to baryons, and the resulting antiquark sea PDF.

    hep-phnucl-thPRD(2019)·12 citations
15. 15*

    Heavy Black Hole Effective Theory

    Poul H. Damgaard🇩🇰 · Kays Haddad🇩🇰 · Andreas Helset🇩🇰

    We formulate an effective field theory describing large mass scalars and fermions minimally coupled to gravity. The operators of this effective field theory are organized in powers of the transfer momentum divided by the mass of the matter field, an expansion which lends itself to the efficient extraction of classical contributions from loop amplitudes in both the post-Newtonian and post-Minkowskian regimes. We use this effective field theory to calculate the classical and leading quantum gravitational scattering amplitude of two heavy spin-1/2 particles at the second post-Minkowskian order.

    hep-phgr-qchep-thJHEP(2019)·200 citations
16. 16*

    Renormalization-group evolution of the fermion mass matrices

    Zhi-cheng Liu🇨🇳

    The one-loop renormalization-group equations (RGEs) running behavior of quark and lepton mass matrices with general structures are studied simultaneously. Suppose the non-linear terms of RGEs are dominated by the Yukawa couplings of top quark and {\tau} lepton, the unitary matrices that diagonalize the mass matrices of up-type quark and charged lepton in Hermitian basis are found as invariant with energy scale. Based on this result, we can decouple the RGEs and obtain the RGE corrected mass matrices of fermion. As examples, we consider the renormalization-group evolution of fermion matrices with four or five texture zeros and of lepton mass matrices which realize the tribimaximal mixing.

    hep-ph1 citation
17. 17*

    Neutral pion mass in the linear sigma model coupled to quarks at arbitrary magnetic field

    Aritra Das🇮🇳 · Najmul Haque🇮🇳

    We calculate the neutral pion mass in the presence of an external magnetic field of arbitrary strength in the framework of the linear sigma model coupled to quarks at zero temperature. We find nonmonotonic behavior of the pion mass as a function of magnetic field. We are also able to reproduce existing results for the weak-field approximation.

    hep-phnucl-thPRD(2020)·37 citations
18. 18*

    Dark matter in the Randall-Sundrum model

    Mukesh Kumar🇿🇦 · Ashok Goyal🇿🇦 · Rashidul Islam🇿🇦

    In Ref. \cite{Goyal:2019vsw}, we had considered simplified dark matter models interacting gravitationally with the Standard Model particles in a Randall-Sundrum frame work where models are considered with non-universal couplings. In the top-philic graviton model the right-handed top quarks are taken to interact strongly with the gravitons and in the lepton-philic model, we assume that only the right-handed charged leptons interact strongly with the gravitons. We extend the study to include not only the scalar, vector and spin-1/2 fermions but also spin-3/2 fermionic dark matter. We find that there is a large parameter space in these benchmark models where it is possible to achieve the observed relic density consistent with the direct and indirect searches, which are also consistent with the data from Large Hadron Collider.

    hep-ph2 citations
19. 19*

    Exchange driven freeze out of dark matter

    Tarak Nath Maity🇮🇳 · Tirtha Sankar Ray🇮🇳

    We introduce a novel mechanism where processes that preserve the number density of the dark sector set the relic density of a thermal particulate dark matter. In a relatively degenerate multipartite dark sector if there is a considerable time lapse between the freeze out of various species then a process like exchange between dark sector constituents can play the pivotal role of driving freeze out and setting dark matter relic density. As a proof of principle, we present simple scalar models with viable dark matter in the GeV scale to demonstrate this phenomenon.

    hep-phPRD(2020)·29 citations
20. 20*

    Average Transverse Momenta of Hadrons at LHC Energy 7 TeV vs. Masses and Heavy Neutral Hadron States

    Olga I. Piskounova (P.N.Lebedev Physical Institute of Russian Academy of Sciences, Moscow, Russia)🇷🇺

    This paper examines the transverse momentum spectra of hadrons in the multiparticle production at LHC in the framework of the Quark-Gluon String Model (QGSM). It discusses the dependence of average pt on the masses of mesons and baryons at the LHC energy 7 TeV. The QGSM description of the experimental spectra of various hadrons led to the number of conclusions. I. The average transverse momenta of baryons and mesons are growing with the hadron mass, so for beauty hadrons, they are almost equal to the mass. II. By the product of research, a regularity has been detected in the mass gaps between hadron generations. This hypothesis suggests some hidden symmetrical (neither-meson-nor-baryon) neutral hadron states with the masses: 0.251,0.682,1.85,5.04,13.7,37.2,101.,275.,748.... GeV, which is produced by geometrical progression with the mass factor $\delta (M)$= 2.721828 III. The baryon-meson symmetry seems broken until the mass of beauty hadrons, then the hidden states should be more and more stable with the growth of the mass, so the suggested sequence of hadronic states is a proper candidate for the Dark Matter that, you know, contributes the valuable part to the mass of Universe. The growing average transverse momenta are extrapolated with a similar function, as for energy dependence of average baryon $p_t$, $<p_t>\propto M^{0.1}$.

    hep-ph6 citations
21. 21*

    Exact hydrodynamic attractor of an ultrarelativistic gas of hard spheres

    Gabriel S. Denicol🇧🇷 · Jorge Noronha🇧🇷

    We derive the general analytical solution of the viscous hydrodynamic equations for an ultrarelativistic gas of hard spheres undergoing Bjorken expansion, taking into account effects from particle number conservation, and use it to analytically determine its attractor at late times. Differently than all the cases considered before involving rapidly expanding fluids, in this example the gradient expansion converges. We exactly determine the hydrodynamic attractor of this system when its microscopic dynamics is modeled by the Boltzmann equation with a fully nonlinear collision kernel. The exact late time attractor of this system can be reasonably described by hydrodynamics even when the gradients are large.

    ↳ nucl-thhep-phPRL(2020)·72 citations
22. 22*

    High-energy neutrino event simulation at NLO in Genie for KM3NeT and other observatories

    Alfonso Garcia🇳🇱 · Aart Heijboer (for the KM3NeT Collaboration)🇳🇱

    High-energy neutrino astronomy is a key pillar of multi-messenger astronomy and has the potential to also advance fundamental neutrino physics. An accurate simulation of the neutrino interactions is key in any analysis of neutrino telescope data. The currently available generator codes of neutrino interactions use leading order expressions for the differential cross sections which govern rate and kinematics of the events. These calculations are affected by well-known large theoretical uncertainties, hence the need of beyond leading order formalism. Also, a consistent use of modern Parton Density Functions, which are derived using NLO (or NNLO) frameworks, is required. For this reason and others, the GENIE event generator of neutrino interactions, which is a standard tool in the few-GeV energy regime, has so far been stated to be valid up to only about 1 TeV. The work reported here consists of a high-energy (up to 10${}^{10}$ GeV) extension, which will be available in GENIEv4. It interfaces PYTHIA6 for the hadronization and employs a pragmatic method to assign the flavour of the struck and outgoing quarks, so that the heavy quark production, including bottom and top, is also correctly simulated.

    ↳ hep-exhep-phPoS(2020)·11 citations
23. 23*

    The Exposure-Background Duality in the Searches of Neutrinoless Double Beta Decay

    M.K. Singh🇹🇼 · H.T. Wong🇹🇼 · L. Singh🇹🇼 · V. Sharma🇹🇼 · V. Singh🇮🇳 · Q. Yue🇨🇳

    Tremendous efforts are required to scale the summit of observing neutrinoless double beta decay ($0\nu \beta \beta$). This article quantitatively explores the interplay between exposure (target mass X data taking time) and background levels in $0\nu \beta \beta$ experiments. In particular, background reduction can substantially alleviate the necessity of unrealistic large exposure as the normal mass hierarchy (NH) is probed. The non-degenerate (ND)-NH can be covered with an exposure of O(100) ton-year, which is only an order of magnitude larger than those planned for next generation projects - provided that the background could be reduced by 0($10^{-6}$) relative to the current best levels. It follows that background suppression will be playing increasingly important and investment-effective, if not determining, roles in future $0\nu \beta \beta$ experiments with sensitivity goals of approaching and covering ND-NH.

    ↳ hep-exhep-phnucl-exPRD(2020)·17 citations
24. 24*

    Real photon emissions in leptonic decays

    G.M. de Divitiis🇮🇹 · A. Desiderio🇮🇹 · M. Di Carlo🇮🇹 · R. Frezzotti🇮🇹 · M. Garofalo🇮🇹 · D. Giusti🇮🇹 · M. Hansen🇮🇹 · V. Lubicz🇮🇹 · F. Mazzetti🇮🇹 · G. Martinelli🇮🇹 · C.T. Sachrajda🇬🇧 · F. Sanfilippo🇮🇹 · S. Simula🇮🇹 · N. Tantalo🇮🇹

    We present a non-perturbative calculation of the form factors which contribute to the amplitudes for the radiative decays $P\to \ell {\bar{\nu }}_{\ell }\gamma$, where $P$ is a pseudoscalar meson and $\ell$ is a charged lepton. Together with the non-perturbative determination of the virtual photon corrections to the processes $P\to \ell {\bar{\nu }}_{\ell }$, this will allow accurate predictions to be made at $O({\alpha }_{em})$ for leptonic decay rates for pseudoscalar mesons ranging from the pion to the $B$ meson. We are able to separate unambiguously the point-like contribution, the square of which leads to the infrared divergence in the decay rate, from the structure dependent, infrared-safe, terms in the amplitude. The fully non-perturbative, $O(a)$ improved calculation of the inclusive leptonic decay rates will lead to significantly improved precision in the determination of the corresponding Cabibbo-Kobayashi-Maskawa (CKM) matrix elements. Precise predictions for the emission of a hard photon are also very interesting, especially for the decays of heavy $D$ and $B$ mesons for which currently only model-dependent predictions are available to compare with existing experimental data.

    ↳ hep-lathep-ph10 citations
25. 25*

    Influence of the neutron-skin effect on nuclear isobar collisions at RHIC

    Jan Hammelmann🇩🇪 · Alba Soto-Ontoso🇺🇸 · Massimiliano Alvioli🇮🇹 · Hannah Elfner🇩🇪 · Mark Strikman🇺🇸

    The unambiguous observation of a Chiral Magnetic Effect (CME)-driven charge separation is the core aim of the isobar program at RHIC consisting of ${}_{40}^{96}$Zr+${}_{40}^{96}$Zr and ${}_{44}^{96}$Ru+${}_{44}^{96}$Ru collisions at $\sqrt{s_{\mathrm{NN}}}=200$ GeV. We quantify the role of the spatial distributions of the nucleons in the isobars on both eccentricity and magnetic field strength within a relativistic hadronic transport approach (SMASH, Simulating Many Accelerated Strongly-interacting Hadrons). In particular, we introduce isospin-dependent nucleon-nucleon spatial correlations in the geometric description of both nuclei, deformation for ${}_{44}^{96}$Ru and the so-called neutron skin effect for the neutron-rich isobar i.e. ${}_{40}^{96}$Zr. The main result of this study is a reduction of the magnetic field strength difference between ${}_{44}^{96}$Ru+${}_{44}^{96}$Ru and ${}_{40}^{96}$Zr+${}_{40}^{96}$Zr by a factor of 2, from $10\%$ to $5\%$ in peripheral collisions when the neutron-skin effect is included. Further, we find an increase of eccentricity by up to 10$\%$ when deformation is taken into account while neither the neutron skin effect nor the nucleon-nucleon correlations result into a significant modification of this observable with respect to the traditional Woods-Saxon modeling. Our results suggest a significantly smaller CME signal to background ratio for the experimental charge separation measurement in peripheral collisions with the isobar systems than previously expected.

    ↳ nucl-thhep-phnucl-exPRC(2020)·44 citations
26. 26*

    Stringent constraints on neutron-star radii from multimessenger observations and nuclear theory

    Collin D. Capano🇩🇪 · Ingo Tews🇺🇸 · Stephanie M. Brown🇩🇪 · Ben Margalit🇺🇸 · Soumi De🇺🇸 · Sumit Kumar🇩🇪 · Duncan A. Brown🇺🇸 · Badri Krishnan🇩🇪 · Sanjay Reddy🇺🇸

    The properties of neutron stars are determined by the nature of the matter that they contain. These properties can be constrained by measurements of the star's size. We obtain stringent constraints on neutron-star radii by combining multimessenger observations of the binary neutron-star merger GW170817 with nuclear theory that best accounts for density-dependent uncertainties in the equation of state. We construct equations of state constrained by chiral effective field theory and marginalize over these using the gravitational-wave observations. Combining this with the electromagnetic observations of the merger remnant that imply the presence of a short-lived hyper-massive neutron star, we find that the radius of a $1.4{\mathrm{M}}_{\odot }$ neutron star is $R_{1.4{\mathrm{M}}_{\odot }}=11.0_{-0.6}^{+0.9}\mathrm{km}$ (90% credible interval). Using this constraint, we show that neutron stars are unlikely to be disrupted in neutron-star black-hole mergers; subsequently, such events will not produce observable electromagnetic emission.

    ↳ astro-ph.HEgr-qchep-phnucl-thNature Astron.(2020)·474 citations
27. 27*

    Probing up-down quark matter via gravitational waves

    Chen Zhang🇨🇦

    Recently, it was shown that quark matter with only $u$ and $d$ quarks ($ud$QM) can be the ground state of matter for baryon numbers $A>A_{\text{min}}$ with $A_{\min }\gtrsim 300$. In this paper, we explore $ud$ quark stars ($ud$QSs) that are composed of $ud$QM, in the context of the two-families scenario in which $ud$QSs and hadronic stars (HSs) can coexist. Distinct signatures are discussed compared to the conventional study regarding strange quark stars (SQSs). We show that the requirements of $A_{\min }\gtrsim 300$ and the most massive compact star observed being a $ud$QS together may put stringent constraints on the allowed parameter space of $ud$QSs. Then, we study the related gravitational-wave probe of the tidal deformability in binary star mergers, including the $ud$QS-$ud$QS and $ud$QS-HS cases. The obtained values of the tidal deformability at 1.4 solar masses and the average tidal deformability are all in good compatibility with the experimental constraints of GW170817. This study points to a new possible interpretation of the GW170817 binary merger event, where $ud$QS may be at least one component of the binary system detected.

    ↳ astro-ph.HEgr-qchep-phnucl-thPRD(2020)·49 citations
28. 28*

    The Spectra of Gravitational Atoms

    Daniel Baumann🇳🇱 · Horng Sheng Chia🇳🇱 · John Stout🇳🇱 · Lotte ter Haar🇳🇱

    We compute the quasi-bound state spectra of ultralight scalar and vector fields around rotating black holes. These spectra are determined by the gravitational fine structure constant $\alpha$, which is the ratio of the size of the black hole to the Compton wavelength of the field. When $\alpha$ is small, the energy eigenvalues and instability rates can be computed analytically. Since the solutions vary rapidly near the black hole horizon, ordinary perturbative approximations fail and we must use matched asymptotic expansions to determine the spectra. Our analytical treatment relies on the separability of the equations of motion, and is therefore only applicable to the scalar field and the electric modes of the vector field. However, for slowly-rotating black holes, the equations for the magnetic modes can be written in a separable form, which we exploit to derive their energy eigenvalues and conjecture an analytic form for their instability rates. To check our conjecture, and to extend all results to large values of $\alpha$, we solve for the spectra numerically. We explain how to accurately and efficiently compute these spectra, without relying on separability. This allows us to obtain reliable results for any $\alpha \gtrsim 0.001$ and black holes of arbitrary spin. Our results provide an essential input to the phenomenology of boson clouds around black holes, especially when these are part of binary systems.

    ↳ gr-qchep-phhep-thJCAP(2019)·248 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.