Wed·Sep 20, 2017Wednesday·September 20, 2017

1. 01*

   Learning from Higgs Physics at Future Higgs Factories

   Jiayin Gu🇨🇳 · Honglei Li🇨🇳 · Zhen Liu🇺🇸 · Shufang Su🇺🇸 · Wei Su🇨🇳

   Future Higgs factories can reach impressive precision on Higgs property measurements. In this paper, instead of conventional focus of Higgs precision in certain interaction bases, we explored its sensitivity to new physics models at the electron-positron colliders. In particular, we studied two categories of new physics models, Standard Model (SM) with a real scalar singlet extension, and Two Higgs Double Model (2HDM) as examples of weakly-interacting models, Minimal Composite Higgs Model (MCHM) and three typical patterns of the more general operator counting for strong interacting models as examples of strong dynamics. We performed a global fit to various Higgs search channels to obtain the 95% C.L. constraints on the model parameter space. In the SM with a singlet extension, we obtained the limits on the singlet-doublet mixing angle sin(theta), as well as the more general Wilson coefficients of the induced higher dimensional operators. In the 2HDM, we analyzed tree level effects in tan(beta) vs. cos(beta-alpha) plane, as well as the one-loop contributions from the heavy Higgs bosons in the alignment limit to obtain the constraints on heavy Higgs masses for different types of 2HDM. In strong dynamics models, we obtained lower limits on the strong dynamics scale. In addition, once deviations of Higgs couplings are observed, they can be used to distinguish different models. We also compared the sensitivity of various future Higgs factories, namely Circular Electron Positron Collider (CEPC), Future Circular Collider (FCC)-ee and International Linear Collider (ILC).

   hep-phJHEP(2017)·72 citations
2. 02*

   An Unorthodox Introduction to QCD

   Andrew J. Larkoski🇺🇸

   These are lecture notes presented at the 2017 CTEQ Summer School at the University of Pittsburgh and the 2018 CTEQ Summer School at the University of Puerto Rico, Mayaguez. The title is a reference to hep-th/0309149 and introduces perturbative QCD and its application to jet substructure from a bottom-up perspective based on the approximation of QCD as a weakly-coupled, conformal field theory. Using this approach, a simple derivation of the Sudakov form factor with soft gluon emission modeled as a Poisson process is presented. Topics of the identification and discrimination of quark- versus gluon-initiated jets and jet grooming are also discussed.

   hep-phhep-ex10 citations
3. 03*

   Interactions and oscillations of coherent flavor eigenstates in beta decay

   Cheng-Yang Lee🇮🇳

   The theory pioneered by Blasone and Vitiello describes massive neutrinos as generalized coherent flavor eigenstates within the extended Standard Model. In this paper, we compute the neutron beta decay spectrum for the Blasone-Vitiello theory in a model with two neutrinos. For relativistic neutrinos, the obtained spectrum is in agreement with the Standard Model. However, there are discrepancies when the kinetic energy of the electron is close to the end point energy. The possibility of measuring the discrepancies in future experiments is discussed.

   hep-phMod.Phys.Lett.A(2020)·28 citations
4. 04*

   The dark matter effect on realistic equation of state in neutron stars

   Grigoris Panotopoulos🇵🇹 · Ilidio Lopes🇵🇹

   In this work we apply relativistic mean-field theory in neutron stars assuming that fermionic dark matter is trapped inside the star and interacts directly with neutrons by exchanging Standard Model Higgs bosons. For realistic values of the parameters of the model we compute numerically the equation of state, and we compare it to the standard one. Furthermore, the mass-to-radius relation for both equations of state (pure neutron matter as well as admixed DM-neutron star) is shown, and the highest star mass for both cases is reported.

   hep-phPRD(2017)·156 citations
5. 05*

   Dissipative Properties and Isothermal Compressibility of Hot and Dense Hadron Gas using Non-extensive Statistics

   Swatantra Kumar Tiwari🇮🇳 · Sushanta Tripathy🇮🇳 · Raghunath Sahoo🇮🇳 · Nilotpal Kakati🇮🇳

   We evaluate the transport properties such as shear viscosity ($\eta$), bulk viscosity ($\zeta$) and their ratios over entropy density ($s$) for hadronic matter using relativistic non-extensive Boltzmann transport equation (NBTE) in relaxation time approximation (RTA). In NBTE, we argue that the system far from equilibrium may not reach to an equilibrium described by extensive (Boltzmann-Gibbs (BG)) statistics but to a $q$-equilibrium defined by Tsallis non-extensive statistics after subsequent evolution, where $q$ denotes the degree of non-extensivity. We observe that $\eta /s$ and $\zeta /s$ decrease rapidly with temperature ($T$) for various $q$-values. As $q$ increases, the magnitudes of $\eta /s$ and $\zeta /s$ decrease with $T$. We also show the upper mass cutoff dependence of these ratios for a particular $q$ and find that they decrease with the increase in mass cutoff of hadrons. Further, we present the first estimation of isothermal compressibility (${\kappa }_T$) using non-extensive Tsallis statistics at finite baryon chemical potential (${\mu }_B$). It is observed that, ${\kappa }_T$ changes significantly with the degree of non-extensivity. We also study the squared speed of sound ($c_s^2$) as a function of temperature at finite baryon chemical potential for various $q$ and upper mass cutoffs. It is noticed that there is a strong impact of $q$ and mass cutoff on the behaviour of $c_s^2$.

   hep-phnucl-thEPJC(2018)·17 citations
6. 06*

   Elliptic Flow in Pb+Pb Collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV at the LHC Using Boltzmann Transport Equation with Non-extensive Statistics

   Sushanta Tripathy🇮🇳 · Swatantra Kumar Tiwari🇮🇳 · Mohammed Younus🇮🇳 · Raghunath Sahoo🇮🇳

   Elliptic flow in heavy-ion collisions is an important signature of a possible de-confinement transition from hadronic phase to partonic phase. In the present work, we use non-extensive statistics, which has been used for transverse momentum ($p_{\mathrm{T}}$) distribution in proton+proton ($p+p$) collisions, as the initial particle distribution function in Boltzmann Transport Equation (BTE). A Boltzmann-Gibbs Blast Wave (BGBW) function is taken as an equilibrium function to get the final distribution to describe the particle production in heavy-ion collisions. In this formalism, we try to estimate the elliptic flow in Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV at the LHC for different centralities. The elliptic flow ($v_2$) of identified particles seems to be described quite well in the available $p_{\mathrm{T}}$ range. An approach, which combines the non-extensive nature of particle production in $p+p$ collisions through an evolution in kinetic theory using BTE, with BGBW equilibrium distribution is successful in describing the spectra and elliptic flow in heavy-ion collisions.

   hep-phnucl-thEPJA(2018)·21 citations
7. 07*

   Role of Multi-Parton Interactions on $J/\psi$ production in $p+p$ collisions at LHC Energies

   Dhananjaya Thakur🇮🇳 · Sudipan De🇮🇳 · Raghunath Sahoo🇮🇳 · Soumya Dansana🇮🇳

   The production mechanism of quarkonia states in hadronic collisions is still to be understood by the scientific community. In high-multiplicity $p+p$ collisions, Underlying Event (UE) observables are of major interest. The Multi-Parton Interactions (MPI) is a UE observable, where several interactions occur at the partonic level in a single $p+p$ event. This leads to dependence of particle production on event multiplicity. If the MPI occurs in a harder scale, there will be a correlation between the yield of quarkonia and total charged particle multiplicity. The ALICE experiment at the Large Hadron Collider (LHC) in $p+p$ collisions at $\sqrt{s}$ = 7 and 13 TeV has observed an approximate linear increase of relative $J/\psi$ yield ($\frac{d{N}_{J/\psi }/dy}{<d{N}_{J/\psi }/dy>}$) with relative charged particle multiplicity density ($\frac{d{N}_{ch}/dy}{<d{N}_{ch}/dy>}$). In our present work we have performed a comprehensive study of the production of charmonia as a function of charged particle multiplicity in $p+p$ collisions at LHC energies using pQCD-inspired multiparton interaction model, PYTHIA8 tune 4C, with and without Color Reconnection (CR) scheme. A detail multiplicity and energy dependent study is performed to understand the effects of MPI on $J/\psi$ production. The ratio of $\psi (2S)$ to $J/\psi$ is also studied as a function of charged particle multiplicity at LHC energies.

   hep-phhep-exnucl-exnucl-thPRD(2018)·44 citations
8. 08*

   Status of Natural Supersymmetry from the GmSUGRA in Light of the current LHC Run-2 and LUX data

   Waqas Ahmed🇨🇳 · Xiao-Jun Bi🇨🇳 · Tianjun Li🇨🇳 · Jia Shu Niu🇨🇳 · Shabbar Raza🇵🇰 · Qian-Fei Xiang🇨🇳 · Peng-Fei Yin🇨🇳

   We study natural supersymmetry in the Generalized Minimal Supergravity (GmSUGRA). For the parameter space with low energy electroweak fine-tuning measures less than 50, we are left with only the $Z$-pole, Higgs-pole and Higgsino LSP scenarios for dark matter (DM). We perform the focused scans for such parameter space and find that it satisfies various phenomenological constraints and is compatible with the current direct detection bound on neutralino DM reported by the LUX experiment. Such parameter space also has solutions with correct DM relic density besides the solutions with DM relic density smaller or larger than 5$\sigma$ WMAP9 bounds. We present five benchmark points as examples. In these benchmark points, gluino and the first two generations of squarks are heavier than 2 TeV, stop ${\tilde{t}}_{1,2}$ are in the mass range $[1,2]$ TeV, while sleptons are lighter than 1 TeV. Some part of the parameter space can explain the muon anomalous magnetic moment within 3$\sigma$ as well. We also perform the collider study of such solutions by implementing and comparing with relevant studies done by the ATLAS and CMS Collaborations. We find that the points with Higgsino dominant ${\tilde{\chi }}_2^0/{\widetilde{{\chi }_1}}^{\pm }$ mass up to $300$ GeV are excluded in $Z$-pole scenario while for Higgs-pole scenario, the points with ${\tilde{\chi }}_2^0$ mass up to $460$ GeV are excluded. We also notice that the Higgsino LSP points in our present scans are beyond the reach of present LHC searches. Next, we show that for both the $Z$-pole and Higgs-pole scenarios, the points with electroweak fine-tuning measure around 20 do still survive.

   hep-phPRD(2018)·7 citations
9. 09*

   DIS structure functions in the NLO approximation of the Parton Reggeization Approach

   Maxim Nefedov🇷🇺 · Vladimir Saleev🇷🇺

   The main ideas of the NLO calculations in Parton Reggeization Approach are illustrated on the example of the simplest NLO subprocess, which contributes to DIS: ${\gamma }^{\star }+R\to q+\bar{q}$. The double counting with the LO contribution ${\gamma }^{\star }+Q\to q$ is resolved. The problem of matching of the NLO results for single-scale observables in the Parton Reggeization Approach on the corresponding NLO results in the Collinear Parton Model is considered. In the developed framework, the usual NLO PDFs in the $\overline{MS}$-scheme can be consistently used as the collinear input for the NLO calculation in the Parton Reggeization Approach.

   hep-phEPJ Web Conf.(2017)·4 citations
10. 10*

    Hidden $U(1)$ gauge symmetry realizing a neutrinophilic two-Higgs-doublet model with dark matter

    Takaaki Nomura🇰🇷 · Hiroshi Okada🇹🇼

    We propose a neutrinophilic two Higgs doublet model with hidden local $U(1)$ symmetry, where active neutrinos are Dirac type, and a fermionic DM candidate is naturally induced as a result of remnant symmetry even after the spontaneous symmetry breaking. In addition, a physical Goldstone boson is arisen as a consequence of two types of gauge singlet bosons and contributes to the DM phenomenologies as well as additional neutral gauge boson. Then we will analyze the relic density of DM within the safe range of direct detection searches, and show the allowed region of dark matter mass.

    hep-phPRD(2018)·24 citations
11. 11*

    The SMEFTsim package, theory and tools

    Ilaria Brivio🇩🇰 · Yun Jiang🇩🇰 · Michael Trott🇩🇰

    We report codes for the Standard Model Effective Field Theory (SMEFT) in FeynRules -- the SMEFTsim package. The codes enable theoretical predictions for dimension six operator corrections to the Standard Model using numerical tools, where predictions can be made based on either the electroweak input parameter set $\{{\hat{\alpha }}_{ew},{\hat{m}}_Z,{\hat{G}}_F\}$ or $\{{\hat{m}}_W,{\hat{m}}_Z,{\hat{G}}_F\}$. All of the baryon and lepton number conserving operators present in the SMEFT dimension six Lagrangian, defined in the Warsaw basis, are included. A flavour symmetric $\mathrm{U}(3{)}^5$ version with possible non-SM $\mathrm{CP}$ violating phases, a (linear) minimal flavour violating version neglecting such phases, and the fully general flavour case are each implemented. The SMEFTsim package allows global constraints to be determined on the full Wilson coefficient space of the SMEFT. As the number of parameters present is large, it is important to develop global analyses on reduced sets of parameters minimizing any UV assumptions and relying on IR kinematics of scattering events and symmetries. We simultaneously develop the theoretical framework of a "W-Higgs-Z pole parameter" physics program that can be pursued at the LHC using this approach and the SMEFTsim package. We illustrate this methodology with several numerical examples interfacing SMEFTsim with MadGraph5. The SMEFTsim package can be downloaded at https://feynrules.irmp.ucl.ac.be/wiki/SMEFT

    hep-phhep-exJHEP(2017)·315 citations
12. 12*

    Ground State Mass Predictions of Heavy-Light Hybrids from QCD Sum-Rule Analysis ($J^P=\left\{0^{\pm },1^{\pm }\right\}$)

    J. Ho🇨🇦 · D. Harnett🇨🇦 · T.G. Steele🇨🇦

    We present QCD Laplace sum-rule predictions of ground state masses of heavy-light open-flavour hybrid mesons. Having computed leading-order diagonal correlation functions, including up to dimension six gluon condensate contributions, we extract hybrid mass predictions for all $J^P\in \{0^{\pm },1^{\pm }\}$, and explore possible mixing effects with conventional meson states. Similarities are found in the mass hierarchy in both charm and bottom systems with some exceptions that are discussed.

    hep-phNucl.Part.Phys.Proc.(2018)·12 citations
13. 13*

    Hyperfine splitting in ordinary and muonic hydrogen

    Oleksandr Tomalak🇩🇪

    We provide an accurate evaluation of the two-photon exchange correction to the hyperfine splitting of S energy levels in muonic hydrogen exploiting the corresponding measurements in electronic hydrogen. The proton structure uncertainty in the calculation of ${\alpha }^5$ contribution is sizably reduced.

    hep-phnucl-exnucl-thphysics.atom-phEPJA(2018)·18 citations
14. 14*

    Same Sign versus Opposite Sign Dileptons as a Probe of Low Scale Seesaw Mechanisms

    Arindam Das🇰🇷 · P. S. Bhupal Dev🇺🇸 · Rabindra N. Mohapatra🇺🇸

    We calculate the ratio $R_{\ell \ell }$ of same sign (SS) to opposite sign (OS) dileptons in type I and generalized inverse seesaw models and show that it can be anywhere between 0 and 1 depending on the detailed texture of the right-handed neutrino mass matrix. Measurement of $R_{\ell \ell }$ in hadron colliders can therefore provide a way to probe the nature of seesaw mechanism and also to distinguish between the two types of seesaw mechanisms. We work within the framework of left-right symmetric model as an example. We emphasize that coherence of the final states in the $W_R$ decay is crucial for this discussion and it requires the right-handed neutrinos to be highly degenerate. We isolate the range of parameters in the model where this effect is observable at the LHC and future colliders.

    hep-phhep-exPRD(2018)·109 citations
15. 15*

    The Sun as a sub-GeV Dark Matter Accelerator

    Timon Emken🇩🇰 · Chris Kouvaris🇩🇰 · Niklas Grønlund Nielsen🇩🇰

    Sub-GeV halo dark matter that enters the Sun can potentially scatter off hot solar nuclei and be ejected much faster than its incoming velocity. We derive an expression for the rate and velocity distribution of these reflected particles taking into account the Sun's temperature and opacity. We further demonstrate that future direct detection experiments could use these energetic reflected particles to probe light dark matter in parameter space that cannot be accessed via ordinary halo dark matter.

    hep-phastro-ph.COhep-exPRD(2018)·80 citations
16. 16*

    New Dissipation Mechanisms from Multi-level Dark Matter Scattering

    Anirban Das🇮🇳 · Basudeb Dasgupta (Tata Inst., Mumbai)🇮🇳

    Multi-level dark matter with diagonal and off-diagonal interactions shows a rich phenomenology in its self-scattering. If the interactions are mediated by a particle that is less massive than the dark matter, Sommerfeld effect can lead to resonant enhancement of the scattering. For mediators lighter than the level separation, dark matter particles can upscatter to excited states and de-excite by emitting these mediators. We compute these cross-sections, both above and below the kinematic threshold, in a generic two-component dark matter model and identify the large inelastic cross-section as a result of maximal mixing between the two states. A new route for cooling of large dark matter halos and a new drag force between two colliding halos are identified and shown to arise purely from the inelastic scattering.

    hep-phastro-ph.COPRD(2018)·23 citations
17. 17*

    Helicity-dependent generalized parton distributions for nonzero skewness

    Chandan Mondal🇨🇳

    We investigate the helicity dependent generalized parton distributions (GPDs) in momentum as well as transverse position (impact) spaces for up and down quarks in a proton when the momentum transfer in both the transverse and longitudinal directions are nonzero. The GPDs are evaluated using the light-front wavefunctions of a quark-diquark model for nucleon where the wavefunctions are constructed by the soft-wall AdS/QCD correspondence. We also express the GPDs in the boost-invariant longitudinal position space.

    hep-phEPJC(2017)·33 citations
18. 18*

    Topology in the 2d Heisenberg Model under Gradient Flow

    Ilya O. Sandoval🇲🇽 · Wolfgang Bietenholz🇲🇽 · Philippe de Forcrand🇨🇭 · Urs Gerber🇲🇽 · Héctor Mejía-Díaz🇲🇽

    The 2d Heisenberg model --- or 2d O(3) model --- is popular in condensed matter physics, and in particle physics as a toy model for QCD. Along with other analogies, it shares with 4d Yang-Mills theories, and with QCD, the property that the configurations are divided in topological sectors. In the lattice regularisation the topological charge $Q$ can still be defined such that $Q\in \mathbb{Z}$. It has generally been observed, however, that the topological susceptibility ${\chi }_{\mathrm{t}}=⟨Q^2⟩/V$ does not scale properly in the continuum limit, i.e. that the quantity ${\chi }_{\mathrm{t}}{\xi }^2$ diverges for $\xi \to \infty$ (where $\xi$ is the correlation length in lattice units). Here we address the question whether or not this divergence persists after the application of the Gradient Flow.

    ↳ hep-latcond-mat.stat-mechhep-phJ.Phys.Conf.Ser.(2017)·2 citations
19. 19*

    Chiral Transition of SU(4) Gauge Theory with Fermions in Multiple Representations

    Venkitesh Ayyar🇺🇸 · Thomas DeGrand🇺🇸 · Daniel C. Hackett🇺🇸 · William I. Jay🇺🇸 · Ethan T. Neil🇺🇸 · Yigal Shamir🇮🇱 · Benjamin Svetitsky🇮🇱

    We report preliminary results on the finite temperature behavior of SU(4) gauge theory with dynamical quarks in both the fundamental and two-index antisymmetric representations. This system is a candidate to present scale separation behavior, where fermions in different representations condense at different temperature or coupling scales. Our simulations, however, reveal a single finite-temperature phase transition at which both representations deconfine and exhibit chiral restoration. It appears to be strongly first order. We compare our results to previous single-representation simulations. We also describe a Pisarski-Wilczek stability analysis, which suggests that the transition should be first order.

    ↳ hep-lathep-phEPJ Web Conf.(2018)·14 citations
20. 20*

    On the one-loop calculations with Reggeized quarks

    Maxim Nefedov🇷🇺 · Vladimir Saleev🇷🇺

    The technique of one-loop calculations for the processes involving Reggeized quarks is described in the framework of gauge invariant effective field theory for the Multi-Regge limit of QCD, which has been introduced by Lipatov and Vyazovsky. The rapidity divergences, associated with the terms enhanced by $\log (s)$, appear in the loop corrections in this formalism. The covariant procedure of regularization of rapidity divergences, preserving the gauge invariance of effective action is described. As an example application, the one-loop correction to the propagator of Reggeized quark and $\gamma Qq$-scattering vertex are computed. Obtained results are used to construct the Regge limit of one-loop $\gamma \gamma \to q\bar{q}$ amplitude. The cancellation of rapidity divergences and consistency of the effective field theory prediction with the full QCD result is demonstrated. The rapidity renormalization group within the effective field theory is discussed.

    ↳ hep-thhep-phMod.Phys.Lett.A(2017)·48 citations
21. 21*

    The gamma-ray spectral feature from Kaluza-Klein dark matter annihilation and its observability

    Satoshi Tsuchida🇯🇵 · Masaki Mori🇯🇵

    The theory of universal extra dimensions involves Kaluza-Klein (KK) particles. The lightest KK particle (LKP) is one of the good candidates for cold dark matter. Annihilation of LKP dark matter in the Galactic halo produces high-energy gamma-rays. The gamma-ray spectrum shows a characteristic peak structure around the LKP mass. This paper investigates the observability of this peak structure by near-future detectors taking account of their energy resolution, and calculates the expected energy spectrum of the gamma-ray signal. Then, by using the HESS data, we set some constraints on the boost factor, which is a product of the annihilation cross section relative to the thermal one and an uncertain factor dependent on the substructure of the LKP distribution in the Galactic halo, for each LKP mass. The resulting upper limit on the boost factor is in the range from 1 to 30. The constraints can be regarded as comparable with the results of previous work for gamma-ray and electron-positron observation. However, the observational data for the TeV or higher energy region are still limited, and the possible LKP signal is not conclusive. Thus, we expect near-future missions with better sensitivity will clarify whether the LKP dark matter should exist or not.

    ↳ astro-ph.HEhep-phInt.J.Mod.Phys.D(2017)·2 citations
22. 22*

    Cosmic-ray Antimatter

    Kfir Blum🇮🇱 · Ryosuke Sato🇮🇱 · Eli Waxman🇮🇱

    In recent years, space-born experiments have delivered new measurements of high energy cosmic-ray (CR) $\bar{p}$ and $e^{+}$. In addition, unprecedented sensitivity to CR composite anti-nuclei anti-d and anti-He is expected to be achieved in the near future. We report on the theoretical interpretation of these measurements. While CR antimatter is a promising discovery tool for new physics or exotic astrophysical phenomena, an irreducible background arises from secondary production by primary CR collisions with interstellar matter. Understanding this irreducible background or constraining it from first principles is an interesting challenge. We review the attempt to obtain such understanding and apply it to CR $\bar{p},e^{+},$ anti-d and anti-He. Based on state of the art Galactic cosmic ray measurements, dominated currently by the AMS-02 experiment, we show that: (i) CR $\bar{p}$ most likely come from CR-gas collisions; (ii) $e^{+}$ data is consistent with, and suggestive of the same secondary astrophysical production mechanism responsible for $\bar{p}$ and dominated by proton-proton collisions. In addition, based on recent accelerator analyses we show that the flux of secondary high energy anti-He may be observable with a few years exposure of AMS-02. We highlight key open questions, as well as the role played by recent and upcoming space and accelerator data in clarifying the origins of CR antimatter.

    ↳ astro-ph.HEhep-ph22 citations
23. 23*

    The merger rate of primordial-black-hole binaries

    Yacine Ali-Haïmoud (1)🇺🇸 · Ely D. Kovetz (2)🇺🇸 · Marc Kamionkowski (2) ((1) NYU, (2) JHU)🇺🇸

    Primordial black holes (PBHs) have long been a candidate for the elusive dark matter (DM), and remain poorly constrained in the ~20-100 Msun mass range. PBH binaries were recently suggested as the possible source of LIGO's first detections. In this paper, we thoroughly revisit existing estimates of the merger rate of PBH binaries. We compute the probability distribution of orbital parameters for PBH binaries formed in the early Universe, accounting for tidal torquing by all other PBHs, as well as standard large-scale adiabatic perturbations. We then check whether the orbital parameters of PBH binaries formed in the early Universe can be significantly affected between formation and merger. Our analytic estimates indicate that the tidal field of halos and interactions with other PBHs, as well as dynamical friction by unbound standard DM particles, do not do significant work on nor torque PBH binaries. We estimate the torque due to baryon accretion to be much weaker than previous calculations, albeit possibly large enough to significantly affect the eccentricity of typical PBH binaries. We also revisit the PBH-binary merger rate resulting from gravitational capture in present-day halos, accounting for Poisson fluctuations. If binaries formed in the early Universe survive to the present time, as suggested by our analytic estimates, they dominate the total PBH merger rate. Moreover, this merger rate would be orders of magnitude larger than LIGO's current upper limits if PBHs make a significant fraction of the dark matter. As a consequence, LIGO would constrain ~10-300 Msun PBHs to constitute no more than ~1% of the dark matter. To make this conclusion fully robust, though, numerical study of several complex astrophysical processes - such as the formation of the first PBH halos and how they may affect PBH binaries, as well as the accretion of gas onto an extremely eccentric binary - is needed.

    ↳ astro-ph.COgr-qchep-phPRD(2017)·510 citations
24. 24*

    Stimulated axion decay in superradiant clouds around primordial black holes

    Joao G. Rosa🇵🇹 · Thomas W. Kephart🇺🇸

    The superradiant instability can lead to the generation of extremely dense axion clouds around rotating black holes. We show that, despite the long lifetime of the QCD axion with respect to spontaneous decay into photon pairs, stimulated decay becomes significant above a minimum axion density and leads to extremely bright lasers. The lasing threshold can be attained for axion masses $\mu \gtrsim 10^{-8}\mathrm{eV}$, which implies superradiant instabilities around spinning primordial black holes with mass $\lesssim 0.01M_{\odot }$. Although the latter are expected to be non-rotating at formation, a population of spinning black holes may result from subsequent mergers. We further show that lasing can be quenched by Schwinger pair production, which produces a critical electron-positron plasma within the axion cloud. Lasing can nevertheless restart once annihilation lowers the plasma density sufficiently, resulting in multiple laser bursts that repeat until the black hole spins down sufficiently to quench the superradiant instability. In particular, axions with a mass $\sim 10^{-5}\mathrm{eV}$ and primordial black holes with mass $\sim 10^{24}$ kg, which may account for all the dark matter in the Universe, lead to millisecond-bursts in the GHz radio-frequency range, with peak luminosities $\sim 10^{42}$ erg/s, suggesting a possible link to the observed fast radio bursts.

    ↳ gr-qcastro-ph.HEhep-phhep-thPRL(2018)·146 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.