Tue·Feb 20, 2018Tuesday·February 20, 2018

1. 01*

   Rho-meson properties in medium

   J. P. B. C. de Melo🇧🇷 · K. Tsushima (Laboratório de Física Teórica e Computacional, LFTC, UCS)🇧🇷

   Properties of $\rho$-meson in symmetric nuclear matter are investigated in a light-front constituent quark model (LFCQM), using the in-medium inputs calculated by the quark-meson coupling (QMC) model. The LFCQM used in this study was already applied for the studies of the electromagnetic properties of $\rho$-meson in vacuum, namely, the charge~$G_0$, magnetic~$G_1$, and quadrupole~$G_2$ form factors, electromagnetic charge radius, and electromagnetic decay constant. We predict that the electromagnetic decay constant, charge radius, and quadrupole moment are enhanced as increasing the nuclear matter density, while the magnetic moment is slightly quenched. Furthermore, we predict that the value $Q_{\mathrm{zero}}^2$, which crosses zero of the charge form factor, $G_0(Q_{\mathrm{zero}}^2)=0$ ($Q^2=-q^2>0$ with $q$ being the four-momentum transfer), decreases as increasing the nuclear matter density.

   hep-phnucl-thPLB(2019)·10 citations
2. 02*

   The small-x gluon distribution in centrality biased pA and pp collisions

   Adrian Dumitru🇺🇸 · Gary Kapilevich🇺🇸 · Vladimir Skokov🇺🇸

   The nuclear modification factor $R_{pA}(p_T)$ provides information on the small-$x$ gluon distribution of a nucleus at hadron colliders. Several experiments have recently measured the nuclear modification factor not only in minimum bias but also for central $pA$ collisions. In this paper we analyze the bias on the configurations of soft gluon fields introduced by a centrality selection via the number of hard particles. Such bias can be viewed as reweighting of configurations of small-$x$ gluons. We find that the biased nuclear modification factor ${\mathcal{Q}}_{pA}(p_T)$ for central collisions is above $R_{pA}(p_T)$ for minimum bias events, and that it may redevelop a "Cronin peak" even at small $x$. The magnitude of the peak is predicted to increase approximately like $1/{A_{\perp }}^{\nu }$, $\nu \sim 0.6\pm 0.1$, if one is able to select more compact configurations of the projectile proton where its gluons occupy a smaller transverse area $A_{\perp }$. We predict an enhanced ${\mathcal{Q}}_{pp}(p_T)-1\sim 1/(p_T^2{)}^{\nu }$ and a Cronin peak even for central $pp$ collisions.

   hep-phnucl-thNPA(2018)·11 citations
3. 03*

   Light inflaton completing Higgs inflation

   Hyun Min Lee🇰🇷

   We consider the extension of the Standard Model (SM) with a light inflaton where both unitarity problem in Higgs inflation and vacuum instability problem are resolved. The linear non-minimal coupling of the inflaton to gravity leads to a significant kinetic mixing between the inflaton and the graviton such that perturbative unitarity is restored up to Planck scale. We show the correlation between unitarity scale and inflationary observables in this model and discuss how the effective Higgs inflation appears.

   hep-phastro-ph.COPRD(2018)·48 citations
4. 04*

   Gluons, Heavy and Light Quarks in the QCD Vacuum

   Mirzayusuf Musakhanov🇺🇿

   We are discussing the properties of the QCD vacuum which might be important especially for the understanding of hadrons with small quark core size $\sim 0.3fm.$ We assume that at these distances the QCD vacuum can be described by the Instanton Liquid Model (ILM). At larger distances, where confinement is important, ILM should be extended to Dyons Liquid Model (DLM). The ILM has only two free parameters, average instanton size $\rho \approx 0.3fm$ and average inter-instanton distance $R\approx 1fm$, and can successfully describe the key features of light hadron physics. One of the important conceptual results was prediction of the momentum dependent dynamical quark mass $M\sim (packingfraction{)}^{1/2}{\rho }^{-1}\approx 360MeV$, later confirmed numerically by evaluations in the lattice. The estimates show that gluon-instanton interaction strength is also big and is controlled by the value of dynamical gluon mass $M_g\approx M$. Heavy quarks interact with instantons much weaker. The heavy quark-instanton interaction strength is given by $\Delta m_Q\sim packingfraction{\rho }^{-1}\approx 70MeV.$ Nevertheless, the direct instanton contribution to the colorless heavy-heavy quarks potential is sizable and must be taken into account. At small distances, where one-gluon exchange contribution to this potential is dominated, we have to take into account dynamical gluon mass $M_g$. Also, instantons are generating light-heavy quarks interactions and allow to describe the nonperturbative effects in heavy-light quarks systems.

   hep-phEPJ Web Conf.(2018)·5 citations
5. 05*

   Disentangling covariant Wigner functions for chiral fermions

   Jian-Hua Gao🇨🇳 · Zuo-Tang Liang🇨🇳 · Qun Wang🇨🇳 · Xin-Nian Wang🇨🇳

   We develop a general formalism for the quantum kinetics of chiral fermions in a background electromagnetic field based on a semiclassical expansion of covariant Wigner functions in the Planck constant $\hslash$. We demonstrate to any order of $\hslash$ that only the time-component of the Wigner function is independent while other components are explicit derivative. We further demonstrate to any order of $\hslash$ that a system of quantum kinetic equations for multiple-components of Wigner functions can be reduced to one chiral kinetic equation involving only the single-component distribution function. These are remarkable properties of the quantum kinetics of chiral fermions and will significantly simplify the description and simulation of chiral effects in heavy ion collisions and Dirac/Weyl semimetals. We present the unintegrated chiral kinetic equations in four-momenta up to $O({\hslash }^2)$ and the integrated ones in three-momenta up to $O(\hslash )$. We find that some singular terms emerge in the integration over the time component of the four-momentum, which result in a new source term contributing to the chiral anomaly, in contrast to the well-known scenario of the Berry phase term. Finally we rewrite our results in any Lorentz frame with a reference four-velocity and show how the non-trivial transformation of the distribution function in different frames emerges in a natural way.

   hep-phnucl-thPRD(2018)·85 citations
6. 06*

   The hadronic vacuum polarisation contributions to the muon $g-2$

   Alexander Keshavarzi🇬🇧 · Daisuke Nomura🇯🇵 · Thomas Teubner🇬🇧

   The hadronic vacuum polarisation contributions to the anomalous magnetic moment of the muon, $a_{\mu }^{\mathrm{had},\mathrm{VP}}$ have been re-evaluated from the combination of $e^{+}{e}^{-}\to \mathrm{hadrons}$ cross section data. Focus has been placed on the development of a new data combination method, which fully incorporates all correlated statistical and systematic uncertainties in a bias free approach. Using these combined data have resulted in estimates of the hadronic vacuum polarisation contributions to $g-2$ of the muon of $a_{\mu }^{\mathrm{had},\mathrm{LO}\mathrm{VP}}=(693.27\pm 2.46)\times 10^{-10}$ and $a_{\mu }^{\mathrm{had},\mathrm{NLO}\mathrm{VP}}=(-9.82\pm 0.04)\times 10^{-10}$. The new estimate for the Standard Model prediction is found to be $a_{\mu }^{\mathrm{SM}}=(11659182.05\pm 3.56)\times 10^{-10}$, which is $3.7\sigma$ below the current experimental measurement. In addition, the prediction for the hadronic contribution to the QED coupling at the $Z$ boson mass has been calculated to be $\Delta {\alpha }_{\mathrm{had}}^{(5)}(M_Z^2)=(276.11\pm 1.11)\times 10^{-4}$, resulting in ${\alpha }^{-1}(M_Z^2)=128.946\pm 0.015$.

   hep-phFrascati Phys.Ser.(2017)·1 citation
7. 07*

   Twist-3 GPDs in Deeply-Virtual Compton Scattering

   Fatma Aslan🇺🇸 · Matthias Burkardt🇺🇸 · Cédric Lorcé🇫🇷 · Andreas Metz🇺🇸 · Barbara Pasquini🇮🇹

   The sub-leading power of the scattering amplitude for deeply-virtual Compton scattering (DVCS) off the nucleon contains leading-twist and twist-3 generalized parton distributions (GPDs). We point out that in DVCS, at twist-3 accuracy, one cannot address any individual twist-3 GPD. This complication appears on top of the deconvolution issues familiar from the twist-2 DVCS amplitude. Accessible are exclusively linear combinations involving both vector and axial-vector twist-3 GPDs. This implies, in particular, that the (kinetic) orbital angular momentum of quarks can hardly be constrained by twist-3 DVCS observables. Moreover, using the quark-target model, we find that twist-3 GPDs can be discontinuous. The discontinuities however cancel in the DVCS amplitude, which further supports the hypothesis of factorization at twist-3 accuracy.

   hep-phhep-exnucl-exPRD(2018)·35 citations
8. 08*

   Mass problem in the Standard Model

   R. Martinez🇨🇴 · S. F. Mantilla🇨🇴

   We propose a new $\mathrm{SU}(3{)}_C\otimes \mathrm{SU}(2{)}_L\otimes \mathrm{U}(1{)}_Y\otimes \mathrm{U}(1{)}_X$ gauge model which is non universal respect to the three fermion families of the Standard Model. We introduce additional one top-like quark, two bottom-like quarks and three right handed neutrinos in order to have an anomaly free theory. We also consider additional three right handed neutrinos which are singlets respect to the gauge symmetry of the model to implement see saw mechanism and give masses to the light neutrinos according to the neutrino oscillation phenomenology. In the context of this horizontal gauge symmetry we find mass ansatz for leptons and quarks. In particular, from the analysis of solar, atmospheric, reactor and accelerator neutrino oscillation experiments, we get the allow region for the Yukawa couplings for the charge and neutral lepton sectors according with the mass squared differences and mixing angles for the two neutrino hierarchy schemes, normal and inverted.

   hep-phEPJ Web Conf.(2018)·1 citation
9. 09*

   CGC/saturation approach: an impact-parameter dependent model for diffraction production in DIS

   Carlos Contreras (UTFSM)🇨🇱 · Eugene Levin (Tel Aviv U,/UTFSM)🇮🇱 · Rodrigo Meneses (U.de Valparaiso)🇨🇱 · Irina Potashnikova (UTFSM)🇨🇱

   In the paper we discussed the evolution equations for diffractive production in the framework of CGC/saturation approach, and found the analytical solutions for several kinematic regions. The most impressive features of these solutions are, that diffractive production does not exibit geometric scaling behaviour i.e. being a function of one variable. Based on these solutions, we suggest an impact parameter dependent saturation model, which is suitable for describing diffraction production both deep in the saturation region, and in the vicinity of the saturation scale. Using the model we attempted to fit the combined data on diffraction production from H1 and ZEUS collaborations. We found that we are able describe both $x_{\text{pom}}$ and $\beta$ dependence, as well as $Q$ behavior of the measured cross sections. In spite of the sufficiently large ${\chi }^2/d.o.f.$ we believe that our description provides an initial impetus to find a fit of the experimental data, based on the solution of the CGC/saturation equation, rather than on describing the diffraction system in simplistic manner, assuming that only quark-antiquark pair and one extra gluons, are produced.

   hep-phEPJC(2018)·3 citations
10. 10*

    Mixing angle and decay constants of $J^P=1^{+}$ heavy-light mesons

    Qiang Li🇨🇳 · Tianhong Wang🇨🇳 · Yue Jiang🇨🇳 · Guo-Li Wang🇨🇳 · Chao-Hsi Chang🇨🇳

    The mass spectra, mixing angle and decay constants of the $J^P=1^{+}$ heavy-light mesons are systematically studied within the framework of the Bethe-Salpeter equation (BSE). The full $1^{+}$ Salpeter wave function is given for the first time. The mixing between the $1^{+-}$ and $1^{++}$ in the $1^{+}$ heavy-light systems are automatically determined by the dynamics in the equation without any man-made mixing. The results indicate that in a rigorous study there exists the phenomenon of mixing angle inversion or mass inversion within $1^{+}$ heavy-light doublet, which is sensitive to the $s$-quark mass for the charmed mesons and $u$- or $d$-quark masses for the bottomed mesons. This inversion phenomenon can answer the question of why we have confused mixing angles in the literature and partly explain the lower mass of $D_{s1}(2460)$ compared to that of $D_{s1}(2536)$. The decay constants are also presented and can behave as a good quantity to distinguish the $1^{+}$ doublet in heavy-light mesons. This study indicates that the light-quark mass may play an important role in deciding the mass order, mixing angle, and decay constant relation between the $|j_l=\frac{3}{2}⟩$ and $|j_l=\frac{1}{2}⟩$ heavy-light mesons.

    hep-phhep-exPRD(2019)·14 citations
11. 11*

    Connection between diphoton and triboson channels in new physics searches

    Anastasia Sokolenko🇳🇴 · Kyrylo Bondarenko🇳🇱 · Alexey Boyarsky🇳🇱 · Lesya Shchutska🇨🇭

    Diphoton channel provides a clean signature in searches for new physics. In this paper, we discuss a connection between the diphoton channel ($\gamma \gamma$) and triboson channels ($Z\gamma \gamma$, $ZZ\gamma$, $WW\gamma$) imposed by the $SU(2{)}_L\times U(1{)}_Y$ symmetry of the Standard Model (SM) in certain classes of models. To illustrate this idea we choose a simple model that has all these channels. In this model, the same physics can give rise to $\gamma +$MET instead of $\gamma \gamma$ and 2 bosons plus missing energy instead of 3-boson channels. We analyze existing constraints and previous searches and show that channels $WW\gamma$ and especially $Z\gamma +$MET have a potential to discover new physics at the LHC.

    hep-phhep-exPLB(2018)·3 citations
12. 12*

    Alternative renormalizable minimal SO(10) GUT and the Seesaw Scale

    Takeshi Fukuyama🇯🇵 · Nobuchika Okada🇺🇸

    Alternative renormalizable minimal non-SUSY SO(10) GUT model is proposed. Instead of a $126$-dimensional Higgs field, a $120$-dimensional Higgs filed is ntroducedin addition to a $10$-dimensional Higgs field and plays a crucial role to reproduce the realistic charged fermion mass matrices. With contributions of $120$ Higgs field, the original Witten's scenario of inducing the right-handed Majorana neutrino mass through 2-loop diagrams becomes phenomenologically viable. This model inherits the nice features of the conventional renormalizable minimal SO(10) GUT model with $10+\overline{126}$ Higgs fields, while supplemented with a low scale seesaw mechanism due to the 2-loop induced right-handed Majorana neutrino mass. %

    hep-phMod.Phys.Lett.A(2018)·5 citations
13. 13*

    Twist-3 contributions to wide-angle photoproduction of pions

    P. Kroll🇩🇪 · K. Passek-Kumericki🇭🇷

    We investigate wide-angle pi^0 photoproduction within the handbag approach to twist-3 accuracy. In contrast to earlier work both the 2-particle as well as the 3-particle twist-3 contributions are taken into account. It is shown that both are needed for consistent results that respect gauge invariance and crossing properties. The numerical studies reveal the dominance of the twist-3 contribution. With it fair agreement with the recent CLAS measurement of the pi^0 cross section is obtained. We briefly comment also on wide-angle photoproduction of other pseudoscalar mesons.

    hep-phnucl-thPRD(2018)·21 citations
14. 14*

    The Cosmic-Ray Spectra: News on their Knees

    A. De Rújula🇪🇸

    In a comprehensive model of Cosmic Rays (CRs) proposed a decade ago, the energies of the spectral "knees" of the various CR species were predicted to be proportional to mass, rather than charge. The model also predicts the knees to occur at an energy of two to four million times the particle's rest mass. Recent data allow one to verify this prediction, particularly for Fe and lighter-nuclei CRs. But the most stringent test involves the putative knee in the CR electron spectrum, since the mass ratio of electrons to protons (and nuclei) is so very different from their charge ratio(s). Very recent results on the spectra of positrons and electrons at the highest measured energies corroborate the existence of an electron knee, with the expected shape and at the predicted energy.

    hep-phastro-ph.HEPLB(2019)·10 citations
15. 15*

    Seesaw mechanism in magnetic compactifications

    Makoto Ishida🇯🇵 · Kenji Nishiwaki🇰🇷 · Yoshiyuki Tatsuta🇩🇪

    In this paper, we explore a new avenue to a natural explanation of the observed tiny neutrino masses with a dynamical realization of the three-generation structure in the neutrino sector. Under the magnetized background based on $T^2/Z_2$, matter consists of multiply-degenerated zero modes and the whole intergenerational structure is dynamically determined. In this sense, we can conclude that our scenario is favored by minimality, where no degree of freedom remains to deform the intergenerational structure by hand freely. Under the consideration of brane-localized Majorana-type mass terms for an $SU(2{)}_L$ singlet neutrino, it is sufficient to introduce one Higgs doublet for reproducing the observed neutrino data. In all reasonable flux configurations with three right-handed neutrinos, phenomenologically acceptable parameter configurations are found.

    hep-phJHEP(2018)·7 citations
16. 16*

    Localization of the Standard Model via Higgs mechanism and a finite electroweak monopole from non-compact five dimensions

    Masato Arai🇯🇵 · Filip Blaschke🇨🇿 · Minoru Eto🇯🇵 · Norisuke Sakai🇯🇵

    We propose a minimal and self-contained model in non-compact flat five dimensions which localizes the Standard Model (SM) on a domain wall. Localization of gauge fields is achieved by the condensation of Higgs field via a Higgs dependent gauge kinetic term in five-dimensional Lagrangian. The domain wall connecting vacua with unbroken gauge symmetry drives the Higgs condensation which provides both electroweak symmetry breaking and gauge field localization at the same time. Our model predicts higher-dimensional interactions $|H{|}^{2n}(F_{\mu \nu }{)}^2$ in the low-energy effective theory. This leads to two expectations: The one is a new tree-level contribution to $H\to \gamma \gamma$ ($H\to gg$) decay whose signature is testable in future LHC experiment. The other is a finite electroweak monopole which may be accessible to the MoEDAL experiment. Interactions of translational Nambu-Goldstone boson is shown to satisfy a low-energy theorem.

    hep-phhep-thPTEP(2018)·17 citations
17. 17*

    New class of compact stars: Pion stars

    Bastian B. Brandt🇩🇪 · Gergely Endrodi🇩🇪 · Eduardo S. Fraga🇧🇷 · Mauricio Hippert🇧🇷 · Jurgen Schaffner-Bielich🇩🇪 · Sebastian Schmalzbauer🇩🇪

    We investigate the viability of a new type of compact star whose main constituent is a Bose-Einstein condensate of charged pions. Several different setups are considered, where a gas of charged leptons and neutrinos is also present. The pionic equation of state is obtained from lattice QCD simulations in the presence of an isospin chemical potential, and requires no modeling of the nuclear force. The gravitationally bound configurations of these systems are found by solving the Tolman-Oppenheimer-Volkov equations. We discuss weak decays within the pion condensed phase and elaborate on the generation mechanism of such objects.

    hep-phastro-ph.HEhep-latnucl-thPRD(2018)·104 citations
18. 18*

    Searching for new physics with three-particle correlations in $pp$ collisions at the LHC

    Miguel-Angel Sanchis-Lozano🇪🇸 · Edward K. Sarkisyan-Grinbaum🇨🇭

    New phenomena involving pseudorapidity and azimuthal correlations among final state particles in $pp$ collisions at the LHC can hint at the existence of hidden sectors beyond the Standard Model. In this paper we rely on a correlated-cluster picture of multiparticle production, which was shown to account for the ridge effect, to assess the effect of a hidden sector on three-particle correlations concluding that there is a potential signature of new physics that can be directly tested by experiments using well-known techniques.

    hep-phhep-exPLB(2018)·12 citations
19. 19*

    Helicity amplitudes for QCD with massive quarks

    Alexander Ochirov🇨🇭

    The novel massive spinor-helicity formalism of Arkani-Hamed, Huang and Huang provides an elegant way to calculate scattering amplitudes in quantum chromodynamics for arbitrary quark spin projections. In this note we compute two families of tree-level QCD amplitudes with one massive quark pair and n-2 gluons. The two cases include all gluons with identical helicity and one opposite-helicity gluon being color-adjacent to one of the quarks. Our results naturally incorporate the previously known amplitudes for both quark spins quantized along one of the gluonic momenta. In the all-multiplicity formulae presented here the spin quantization axes can be tuned at will, which includes the case of the definite-helicity quark states.

    hep-phhep-thJHEP(2018)·75 citations
20. 20*

    The Color Glass Condensate formalism, Balitsky-JIMWLK evolution and Lipatov's high energy effective action

    Martin Hentschinski🇲🇽

    We investigate the question whether Lipatov's high energy effective action is capable to reproduce quark and gluon propagators which resum interaction with a strong background field within high energy factorization. Such propagators are frequently employed in calculations within the Color Glass Condensate formalism, in particular when considering scattering of a dilute projectile on a dense target nucleus or nucleon. We find that such propagators can be obtained from the high energy effective action, if a special parametrization of the gluonic field is used, first proposed by Lipatov in the original publication on the high energy effective action. The obtained propagators are used to rederive from the high energy effective action the leading order Balitsky-JIMWLK evolution equation in covariant gauge. As an aside, our result confirms the definition of the reggeized gluon as the logarithm of an adjoint Wilson lines, proposed in the literature.

    hep-phPRD(2018)·34 citations
21. 21*

    Efficient integrand reduction for particles with spin

    Rutger H. Boels🇩🇪 · Qingjun Jin🇨🇳 · Hui Luo🇩🇪

    Scattering amplitudes with spinning particles are shown to decompose into multiple copies of simple building blocks to all loop orders, which can be used to efficiently reduce these amplitudes to sums over scalar integrals. Absence of unphysical kinematic singularities cleanly exposed by the method uncover novel consistency relations among master integrals and their coefficients. Analytic results are obtained for the five gluon, two loop, and four gluon, three loop planar scattering amplitudes in pure Yang-Mills theory as well as for leading singularities to even higher orders.

    hep-phhep-th42 citations
22. 22*

    Matter Density Profile Shape Effects at DUNE

    Kevin J. Kelly🇺🇸 · Stephen J. Parke🇺🇸

    Quantum mechanical interactions between neutrinos and matter along the path of propagation, the Wolfenstein matter effect, are of particular importance for the upcoming long-baseline neutrino oscillation experiments, specifically the Deep Underground Neutrino Experiment (DUNE). Here, we explore specifically what about the matter density profile can be measured by DUNE, considering both the shape and normalization of the profile between the neutrinos' origin and detection. Additionally, we explore the capability of a perturbative method for calculating neutrino oscillation probabilities and whether this method is suitable for DUNE. We also briefly quantitatively explore the ability of DUNE to measure the Earth's matter density, and the impact of performing this measurement on measuring standard neutrino oscillation parameters.

    hep-phhep-exPRD(2018)·41 citations
23. 23*

    Lepton flavour violation in the MSSM: exact diagonalization vs mass expansion

    Andreas Crivellin🇨🇭 · Zofia Fabisiewicz🇵🇱 · Weronika Materkowska🇵🇱 · Ulrich Nierste🇩🇪 · Stefan Pokorski🇵🇱 · Janusz Rosiek🇵🇱

    The forthcoming precision data on lepton flavour violating decays require precise and efficient calculations in New Physics models. In this article lepton flavour violating processes within the Minimal Supersymmetric Standard Model (MSSM) are calculated using the method based on the Flavour Expansion Theorem, a recently developed technique performing a purely algebraic mass-insertion expansion of the amplitudes. The expansion in both flavour-violating and flavour-conserving off-diagonal terms of sfermion and supersymmetric fermion mass matrices is considered. In this way the relevant processes are expressed directly in terms of the parameters of the MSSM Lagrangian. We also study the decoupling properties of the amplitudes. The results are compared to the corresponding calculations in the mass eigenbasis (i.e. using the exact diagonalization of the mass matrices). Using these methods, we consider the following processes: $\ell \to {\ell }^{\prime }\gamma$, $\ell \to 3{\ell }^{\prime }$, $\ell \to 2{\ell }^{\prime }\ell "$, $h\to \ell {\ell }^{\prime }$ as well as $\mu \to e$ conversion in nuclei. In the numerical analysis we update the bounds on the flavour changing parameters of the MSSM and examine the sensitivity to the forthcoming experimental results. We find that flavour violating muon decays provide the most stringent bounds on supersymmetric effects and will continue to do so in the future. Radiative $\ell \to {\ell }^{\prime }\gamma$ decays and leptonic three-body decays $\ell \to 3{\ell }^{\prime }$ show an interesting complementarity in eliminating "blind spots" in the parameter space. In our analysis we also include the effects of non-holomorphic $A$-terms which are important for the study of LFV Higgs decays.

    hep-phJHEP(2018)·19 citations
24. 24*

    Primordial black holes and uncertainties in the choice of the window function

    Kenta Ando🇯🇵 · Keisuke Inomata🇯🇵 · Masahiro Kawasaki🇯🇵

    Primordial black holes (PBHs) can be produced by the perturbations that exit the horizon during inflationary phase. While inflation models predict the power spectrum of the perturbations in Fourier space, the PBH abundance depends on the probability distribution function (PDF) of density perturbations in real space. In order to estimate the PBH abundance in a given inflation model, we must relate the power spectrum in Fourier space to the PDF in real space by coarse-graining the perturbations with a window function. However, there are uncertainties on what window function should be used, which could change the relation between the PBH abundance and the power spectrum. This is particularly important in considering PBHs with mass $30M_{\odot }$ that account for the LIGO events because the required power spectrum is severely constrained by the observations. In this paper, we investigate how large influence the uncertainties on the choice of a window function have over the power spectrum required for LIGO PBHs. As a result, it is found that the uncertainties significantly affect the prediction for the stochastic gravitational waves (GWs) induced by the second order effect of the perturbations. In particular, the pulsar timing array constraints on the produced GWs could disappear for the real-space top-hat window function.

    ↳ astro-ph.COhep-phPRD(2018)·170 citations
25. 25*

    Local field theory construction of Very Special Conformal Symmetry

    Yu Nakayama🇯🇵

    Cohen and Glashow argued that very special conformal field theories of a particular kind (i.e. with HOM(2) or SIM(2) invariance) cannot be constructed within the framework of local field theories. We, however, show examples of local construction by using non-linear realization. We further construct linear realization from the topological twist at the cost of unitarity. To demonstrate the ubiquity of our idea, we also present corresponding holographic models.

    ↳ hep-thhep-phPRD(2018)·5 citations
26. 26*

    Nonlinear Breit-Wheeler pair creation with bremsstrahlung $\gamma$ rays

    T. G. Blackburn🇸🇪 · M. Marklund🇸🇪

    Electron-positron pairs are produced through the Breit-Wheeler process when energetic photons traverse electromagnetic fields of sufficient strength. Here we consider a possible experimental geometry for observation of pair creation in the highly nonlinear regime, in which bremsstrahlung of an ultrarelativistic electron beam in a high-$Z$ target is used to produce $\gamma$ rays that collide with a counterpropagating laser pulse. We show how the target thickness may be chosen to optimize the yield of Breit-Wheeler positrons, and verify our analytical predictions with simulations of the cascade in the material and in the laser pulse. The electron beam energy and laser intensity required are well within the capability of today's high-intensity laser facilities.

    ↳ physics.plasm-phhep-phPlasma Phys.Control.Fusion(2018)·51 citations
27. 27*

    Quantum simulation of lattice gauge theories using Wilson fermions

    T. V. Zache🇩🇪 · F. Hebenstreit🇨🇭 · F. Jendrzejewski🇩🇪 · M. K. Oberthaler🇩🇪 · J. Berges🇩🇪 · P. Hauke🇩🇪

    Quantum simulators have the exciting prospect of giving access to real-time dynamics of lattice gauge theories, in particular in regimes that are difficult to compute on classical computers. Future progress towards scalable quantum simulation of lattice gauge theories, however, hinges crucially on the efficient use of experimental resources. As we argue in this work, due to the fundamental non-uniqueness of discretizing the relativistic Dirac Hamiltonian, the lattice representation of gauge theories allows for an optimization that up to now has been left unexplored. We exemplify our discussion with lattice quantum electrodynamics in two-dimensional space-time, where we show that the formulation through Wilson fermions provides several advantages over the previously considered staggered fermions. Notably, it enables a strongly simplified optical lattice setup and it reduces the number of degrees of freedom required to simulate dynamical gauge fields. Exploiting the optimal representation, we propose an experiment based on a mixture of ultracold atoms trapped in a tilted optical lattice. Using numerical benchmark simulations, we demonstrate that a state-of-the-art quantum simulator may access the Schwinger mechanism and map out its non-perturbative onset.

    ↳ cond-mat.quant-gashep-lathep-phquant-phQuantum Sci.Technol.(2018)·130 citations
28. 28*

    Gravitational Wave Emission from Collisions of Compact Scalar Solitons

    Thomas Helfer🇬🇧 · Eugene A. Lim🇬🇧 · Marcos A. G. Garcia🇺🇸 · Mustafa A. Amin🇺🇸

    We numerically investigate the gravitational waves generated by the head-on collision of equal-mass, self-gravitating, real scalar field solitons (oscillatons) as a function of their compactness $\mathcal{C}$. We show that there exist three different possible outcomes for such collisions: (1) an excited stable oscillaton for low $\mathcal{C}$, (2) a merger and formation of a black-hole for intermediate $\mathcal{C}$, and (3) a pre-merger collapse of both oscillatons into individual black-holes for large $\mathcal{C}$. For (1), the excited, aspherical oscillaton continues to emit gravitational waves. For (2), the total energy in gravitational waves emitted increases with compactness, and possesses a maximum which is greater than that from the merger of a pair of equivalent mass black-holes. The initial amplitudes of the quasi-normal modes in the post-merger ring-down in this case are larger than that of corresponding mass black-holes -- potentially a key observable to distinguish black-hole mergers with their scalar mimics. For (3), the gravitational wave output is indistinguishable from a similar mass, black-hole--black-hole merger.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2019)·109 citations
29. 29*

    Theoretical analysis on the $K^{-}{}^3\text{He}\to \Lambda pn$ reaction for the $\bar{K}NN$ bound-state search in the J-PARC E15 experiment

    Takayasu Sekihara (1)🇯🇵 · Eulogio Oset (2)🇪🇸 · Angels Ramos (3) ((1) JAEA, Ibaraki, (2) Valencia U. & Valencia U., IFIC, (3) Barcelona U. & ICC, Barcelona U.)🇪🇸

    We theoretically analyze the $K^{-}{}^3\text{He}\to \Lambda pn$ reaction for the $\bar{K}NN$ bound-state search in the J-PARC E15 experiment. We find that, by detecting a fast and forward neutron in the final state, an almost on-shell $\bar{K}$ is guaranteed, which is essential to make a bound state with two nucleons from ${}^3\text{He}$. Then, this almost on-shell $\bar{K}$ can bring a signal of the $\bar{K}NN$ bound state in the $\Lambda p$ invariant-mass spectrum, although it inevitably brings a kinematic peak above the $\bar{K}NN$ threshold as well. As a consequence, we predict two peaks across the $\bar{K}NN$ threshold in the spectrum: the lower peak coming from the $\bar{K}NN$ bound state, and the higher one originating from the kinematics.

    ↳ nucl-thhep-phnucl-exPoS(2018)·4 citations
30. 30*

    Primordial Black Hole Dark Matter and LIGO/Virgo Merger Rate from Inflation with Running Spectral Indices: Formation in the Matter- and/or Radiation-Dominated Universe

    Kazunori Kohri🇯🇵 · Takahiro Terada🇯🇵

    We study possibilities to explain the whole dark matter abundance by primordial black holes (PBHs) or to explain the merger rate of binary black holes estimated from the gravitational wave detections by LIGO/Virgo. We assume that the PBHs are originated in a radiation- or matter-dominated era from large primordial curvature perturbation generated by inflation. We take a simple model-independent approach considering inflation with large running spectral indices which are parametrized by $n_{\text{s}},{\alpha }_{\text{s}}$, and ${\beta }_{\text{s}}$ consistent with the observational bounds. The merger rate is fitted by PBHs with masses of $\mathcal{O}(10)$ $M_{\odot }$ produced in the radiation-dominated era. Then the running of running should be ${\beta }_{\text{s}}\sim 0.025$, which can be tested by future observation. On the other hand, the whole abundance of dark matter is consistent with PBHs with masses of asteroids ($\mathcal{O}(10^{-17})M_{\odot }$) produced in an early matter-dominated era if a set of running parameters are properly realized.

    ↳ astro-ph.COgr-qchep-phhep-thClass.Quant.Grav.(2018)·67 citations
31. 31*

    Probing sub-GeV Dark Matter-Baryon Scattering with Cosmological Observables

    Weishuang Linda Xu🇺🇸 · Cora Dvorkin🇺🇸 · Andrew Chael🇺🇸

    We derive new limits on the elastic scattering cross-section between baryons and dark matter using Cosmic Microwave Background data from the Planck satellite and measurements of the Lyman-alpha forest flux power spectrum from the Sloan Digital Sky Survey. Our analysis addresses generic cross sections of the form $\sigma \propto v^n$, where v is the dark matter-baryon relative velocity, allowing for constraints on the cross section independent of specific particle physics models. We include high-$\ell$ polarization data from Planck in our analysis, improving over previous constraints. We apply a more careful treatment of dark matter thermal evolution than previously done, allowing us to extend our constraints down to dark matter masses of $\sim$MeV. We show in this work that cosmological probes are complementary to current direct detection and astrophysical searches.

    ↳ astro-ph.COhep-phPRD(2018)·242 citations
32. 32*

    Azimuthal Anisotropies at High Momentum from Purely Non-Hydrodynamic Transport

    Paul Romatschke🇺🇸

    In the limit of short mean free path, relativistic kinetic theory gives rise to hydrodynamics through a systematically improvable gradient expansion. In the present work, a systematically improvable expansion in the opposite limit of large mean free path is considered, describing the dynamics of particles which are almost, but not quite, non-interacting. This non-hydrodynamic "eremitic" expansion does not break down for large gradients, and may be useful in situations where a hydrodynamic treatment is not applicable. As applications, azimuthal anisotropies at high transverse momentum in Pb+Pb and p+Pb collisions at $\sqrt{s}=5.02$ TeV are calculated from the first order eremitic expansion of kinetic theory in the relaxation time approximation.

    ↳ nucl-thastro-ph.HEhep-phEPJC(2018)·42 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.