HEP Phenomenology·hep-ph

Tue·Feb 28, 2017Tuesday·February 28, 2017

30 papers—18 primary·12 cross-listed·reconstructed*

01*
Terrestrial Effects on Dark Matter-Electron Scattering Experiments
Timon Emken🇩🇰 · Chris Kouvaris🇩🇰 · Ian M. Shoemaker🇺🇸
A well-studied possibility is that dark matter may reside in a sector secluded from the Standard Model, except for the so-called photon portal: kinetic mixing between the ordinary and dark photons. Such interactions can be probed at dark matter direct detection experiments, and new experimental techniques involving detection of dark matter-electron scattering offer new sensitivity to sub-GeV dark matter. Typically however it is implicitly assumed that the dark matter is not altered as it traverses the Earth to arrive at the detector. In this paper we study in detail the effects of terrestrial stopping on dark photon models of dark matter, and find that they significantly reduce the sensitivity of XENON10 and DAMIC. In particular we find that XENON10 only excludes masses in the range (5-3000) MeV while DAMIC only probes (20-50) MeV. Their corresponding cross section sensitivity is reduced to a window of cross sections between $(5 \times 1 0^{- 38} - 1 0^{- 30}) cm^{2}$ for XENON10 and a small window around $\sim 1 0^{- 31} cm^{2}$ for DAMIC. We also examine implications for a future DAMIC run.
hep-phastro-ph.COhep-exPRD(2017)·68 citations
02*
Polarized Heavy Quarkonium Production in the Color Evaporation Model
Vincent Cheung🇺🇸 · Ramona Vogt🇺🇸
We explore polarized heavy quarkonium production using the color evaporation model at leading order. We present the polarized to total yield ratio as a function of center of mass energy and rapidity in $p + p$ collisions. At energies far above the $Q Q$ production threshold, we find charmonium and bottomonium production to be longitudinally polarized ( $J_{z} = 0$ ). The quarkonium states are also longitudinally polarized at central rapidity, becoming transversely polarized ( $J_{z} = \pm 1$ ) at the most forward rapidities.
hep-phPRD(2017)·25 citations
03*
Fluctuations In The Inhomogeneous Chiral Transition
T. Tatsumi🇯🇵 · R. Yoshiike🇯🇵 · T.-G. Lee🇯🇵
Chiral pair fluctuation are considered near the phase boundary of the inhomogeneous chiral phase (iCP). The fluctuations are then bosonized and an effective action for the chiral pair fluctuation is basically constructed by considering the ring diagram of the polarization function. We can evaluate the self-energy and effective four point interaction among fluctuations in a consistent way. The peculiar dispersion of the fluctuation, reflecting the spatially inhomogeneous transition, gives rise to interesting and qualitative results. Thermal fluctuations prohibit the second-order transition, while the effect of the quantum fluctuations is rather modest. Quantum and thermal fluctuations changes the second-order transition to the first one by changing the sign of the effective four-point interaction between effective mesons. These features may be observed by relativistic heavy-ion collisions through the analysis of the thermodynamic observables. Distinct from the second-order phase transition, the first moment such as entropy production exhibits an anomalous behavior due to fluctuations, which is one of the signals of the phase transition to iCP. Some similar aspects are also remarked between iCP and the FFLO state in superconductivity.
hep-phnucl-thPoS(2017)·0 citations
04*
Cosmic abundances of SIMP dark matter
Soo-Min Choi🇰🇷 · Hyun Min Lee🇰🇷 · Min-Seok Seo🇰🇷
Thermal production of light dark matter with sub-GeV scale mass can be attributed to $3 \to 2$ self-annihilation processes. We consider the thermal average for annihilation cross sections of dark matter at $3 \to 2$ and general higher-order interactions. A correct thermal average for initial dark matter particles is important, in particular, for annihilation cross sections with overall velocity dependence and/or resonance poles. We apply our general results to benchmark models for SIMP dark matter and discuss the effects of the resonance pole in determining the relic density.
hep-phastro-ph.COJHEP(2017)·74 citations
05*
Why T2K should run in dominant neutrino mode to discover CP violation ?
Monojit Ghosh🇯🇵
The first hint of the leptonic CP phase $δ_{C P} = - 9 0^{\circ}$ has already came from the long-baseline neutrino oscillation experiment T2K. This hint is derived from the neutrino data of T2K and currently it is running in the antineutrino mode. In this work we ask the question what should be the proportion of neutrino and antineutrino running of the T2K experiment to discover CP violation in the leptonic sector.
hep-phSpringer Proc.Phys.(2018)·1 citation
06*
Chiral Magnetic Effect in a Lattice Model
Bo Feng🇨🇳 · De-fu Hou🇨🇳 · Hui Liu🇨🇳 · Hai-cang Ren🇨🇳 · Ping-ping Wu🇨🇳 · Yan Wu🇨🇳
We study analytically the one-loop contribution to the Chiral Magnetic Effect(CME) using lattice regularization with a Wilson fermion field. In the continuum limit, we find that the chiral magnetic current vanishes at nonzero temperature but emerges at zero temperature consistent with that found by Pauli-Villas regularization. For finite lattice size, however, the chiral magnetic current is nonvanishing at nonzero temperature. But the numerical vaule of the coefficient of CME current is very small compared with that extracted from the full QCD simulation for the same lattice parameters. The possibility of higher order corrections from QCD dynamics is also assessed.
hep-phhep-latPRD(2017)·11 citations
07*
Spontaneous Breaking of Gauge Groups to Discrete Symmetries
Bradley L. Rachlin🇺🇸 · Thomas W. Kephart🇺🇸
Many models of beyond Standard Model physics connect flavor symmetry with a discrete group. Having this symmetry arise spontaneously from a gauge theory maintains compatibility with quantum gravity and can be used to systematically prevent anomalies. We minimize a number of Higgs potentials that break gauge groups to discrete symmetries of interest, and examine their scalar mass spectra.
hep-phhep-thmath-phmath.MPJHEP(2017)·18 citations
08*
New dimensions from gauge-Higgs unification
Yutaka Hosotani🇯🇵
The Higgs boson is unified with gauge fields in the gauge-Higgs unification. The $S O (5) \times U (1)$ gauge-Higgs electroweak unification in the Randall-Sundrum warped space yields almost the same phenomenology at low energies as the standard model, and gives many predictions for the Higgs couplings and new $W^{'}, Z^{'}$ bosons around $6 \sim 8$ TeV, which can be tested at 14 TeV LHC. The gauge-Higgs grand unification is achieved in $S O (11)$ gauge theory. It suggests the existence of the sixth dimension (GUT dimension) in addition to the fifth dimension (electroweak dimension). The proton decay is naturally suppressed in the gauge-Higgs grand unification.
hep-phPoS(2017)·7 citations
09*
A theorem about two-body decay and its application for a doubly-charged boson $H^{\pm\pm}$ going to $τ^{\pm} τ^{\pm}$
Li-Gang Xia🇨🇳
In a general decay chain $A \to B_{1} B_{2} \to C_{1} C_{2} \dots$ , we prove that the angular correlation function $I (θ_{1}, θ_{2}, ϕ_{+})$ in the decay of $B_{1, 2}$ is irrelevant to the polarization of the mother particle $A$ at production. This guarantees that we can use these angular distributions to determine the spin-parity nature of $A$ without knowing its production details. As an example, we investigate the decay of a potential doubly-charged boson $H^{\pm\pm}$ going to same-sign $τ$ lepton pair.
hep-phhep-ex0 citations
10*
Suppression of maximal linear gluon polarization in angular asymmetries
Daniel Boer🇳🇱 · Piet J. Mulders🇳🇱 · Jian Zhou🇨🇳 · Ya-jin Zhou🇨🇳
We perform a phenomenological analysis of the $cos 2 ϕ$ azimuthal asymmetry in virtual photon plus jet production induced by the linear polarization of gluons in unpolarized $p A$ collisions. Although the linearly polarized gluon distribution becomes maximal at small $x$ , TMD evolutionleads to a Sudakov suppression of the asymmetry with increasing invariant mass of the $γ^{*}$ -jet pair. Employing a small- $x$ model input distribution, the asymmetry is found to be strongly suppressed under TMD evolution, but still remains sufficiently large to be measurable in the typical kinematical region accessible at RHIC or LHC at moderate photon virtuality, whereas it is expected to be negligible in $Z / W$ -jet pair production at LHC. We point out the optimal kinematics for RHIC and LHC studies, in order to expedite the first experimental studies of the linearly polarized gluon distribution through this process. We further argue that this is a particularly clean process to test the $k_{t}$ -resummation formalism in the small- $x$ regime.
hep-phhep-exnucl-exJHEP(2017)·52 citations
11*
Open charm-bottom axial-vector tetraquarks and their properties
S. S. Agaev🇦🇿 · K. Azizi🇹🇷 · H. Sundu🇹🇷
The charged axial-vector $J^{P} = 1^{+}$ tetraquarks $Z_{q} = [c q] [b ˉ q ˉ]$ and $Z_{s} = [cs] [b ˉ s ˉ]$ with the open charm-bottom contents are studied in the diquark-antidiquark model. The masses and meson-current couplings of these states are calculated by employing QCD two-point sum rule approach, where the quark, gluon and mixed condensates up to eight dimensions are taken into account. These parameters of the tetraquark states $Z_{q}$ and $Z_{s}$ are used to analyze the vertices $Z_{q} B_{c} ρ$ and $Z_{s} B_{c} ϕ$ to determine the strong $g_{Z_{q} B_{c} ρ}$ and $g_{Z_{s} B_{c} ϕ}$ couplings. For these purposes, QCD light-cone sum rule method and its soft-meson approximation are utilized. The couplings $g_{Z_{q} B_{c} ρ}$ and $g_{Z_{s} B_{c} ϕ}$ , extracted from this analysis, are applied for evaluating of the strong $Z_{q} \to B_{c} ρ$ and $Z_{s} \to B_{c} ϕ$ decays' widths, which are essential results of the present investigation. Our predictions for the masses of the $Z_{q}$ and $Z_{s}$ states are confronted with similar results available in the literature.
hep-phEPJC(2017)·22 citations
12*
CORE 3.2 (COmpendium of RElations, Version 3.2)
V.I. Borodulin (1)🇷🇺 · R.N. Rogalyov (2)🇷🇺 · S.R. Slabospitskii (2) ((1) Private educational institution of higer education, Aylamazyan University of Pereslavl, Russia, (2) Institute for High Energy Physics, NRC "Kurchatov Institute, Russia)🇷🇺
The present CORE 3.2 (COmpendium of RElations, Version 3.2) contains various formulas and relations used in the practical calculations in the Standard Model. The properties of the Pauli, Dirac, Gell--Mann matrices, wave functions of free fermions and gauge bosons are considered. We present the full Lagrangian of the Standard Model and the corresponding Feynman rules. The method of the evaluation of the Feynman (loop) integrals and calculations in non-covariant gauges is considered. We discuss in brief the relativistic kinematic and present a large number of the matrix elements of the various processes in the Standard Model.
hep-ph34 citations
13*
High-scale validity of a two Higgs doublet scenario: predicting collider signals
Nabarun Chakrabarty🇮🇳 · Biswarup Mukhopadhyaya🇮🇳
It is possible to ameliorate the Higgs vacuum stability problem by switching over to two Higgs doublet models (2HDM), ensuring a stable electroweak vacuum up to the Planck scale, even though the top quark mass may be on the high side. However, the simultaneous requirements of perturbative unitarity, and also compatibility with collider and flavour data, constrain the parameter space severely. We investigate the collider signals answering to the regions allowed by such constraints. In particular, the near degeneracy of the neutral heavy scalar and the pseudoscalar is a feature that is probed. The LHC allows distinguishability of these two states, together with signal significance of at least 3 $σ$ , in its high-luminosity run. While $e^{+} e^{-}$ colliders may have rather low event rates, muon colliders, cashing on the principle of radiative return, can probe 2HDM scenarios with (pseudo)scalar masses up to a TeV or so, though with the price of losing distinction between the CP-even and odd states.
hep-phPRD(2017)·21 citations
14*
Collective neutrino oscillations and neutrino wave packets
Evgeny Akhmedov🇩🇪 · Joachim Kopp🇩🇪 · Manfred Lindner🇩🇪
Effects of decoherence by wave packet separation on collective neutrino oscillations in dense neutrino gases are considered. We estimate the length of the wave packets of neutrinos produced in core collapse supernovae and the expected neutrino coherence length, and then proceed to consider the decoherence effects within the density matrix formalism of neutrino flavour transitions. First, we demonstrate that for neutrino oscillations in vacuum the decoherence effects are described by a damping term in the equation of motion of the density matrix of a neutrino as a whole (as contrasted to that of the fixed-momentum components of the neutrino density matrix). Next, we consider neutrino oscillations in ordinary matter and dense neutrino backgrounds, both in the adiabatic and non-adiabatic regimes. In the latter case we study two specific models of adiabaticity violation -- one with short-term and another with extended non-adiabaticity. It is demonstrated that, while in the adiabatic case a damping term is present in the equation of motion of the neutrino density matrix (just like in the vacuum oscillation case), no such term in general appears in the non-adiabatic regime.
hep-phastro-ph.SRhep-exJCAP(2017)·59 citations
15*
Strong couplings and form factors of charmed mesons in holographic QCD
Alfonso Ballon-Bayona🇧🇷 · Gastao Krein🇧🇷 · Carlisson Miller🇧🇷
We extend the two-flavor hard-wall holographic model of Erlich, Katz, Son and Stephanov [Phys.\ Rev.\ Lett.\ {\bf 95}, 261602 (2005)] to four flavors to incorporate strange and charm quarks. The model incorporates chiral and flavor symmetry breaking and provides a reasonable description of masses and weak decay constants of a variety of scalar, pseudoscalar, vector and axial-vector strange and charmed mesons. In particular, we examine flavor symmetry breaking in the strong couplings of the $ρ$ meson to the charmed $D$ and $D^{*}$ mesons. We also compute electromagnetic form factors of the $π$ , $ρ$ , $K$ , $K^{*}$ , $D$ and $D^{*}$ mesons. We compare our results for the $D$ and $D^{*}$ mesons with lattice QCD data and other nonperturbative approaches.
hep-phhep-lathep-thPRD(2017)·42 citations
16*
keV sterile neutrino Dark Matter
Alexander Merle🇩🇪
We give an overview of the current status of keV sterile neutrino Dark Matter. After a short introduction, we start by a general discussion of non-thermal production of Dark Matter, which applies to the three most commonly discussed mechanisms to produce sterile neutrino Dark Matter in the Universe: non-resonant, resonant, and decay production. The main goal in each case is to compute the momentum distribution function $f (p, t)$ , which incorporates the full information about the Dark Matter setting under consideration, at least in what concerns its cosmological aspects. While some difficulties lie in the actual computation of this quantity, it is decisive to obtain bounds from cosmic structure formation, which turn out to be the most crucial ones to distinguish different types of production. We will introduce these bounds and we put the resulting limits into a proper context, thereby illustrating that a significant amount of relevant parameter space is available, part of which is testable in particular by Lyman- $α$ data.
hep-phastro-ph.COPoS(2017)·35 citations
17*
Top-Flavoured Dark Matter in Dark Minimal Flavour Violation
Monika Blanke🇩🇪 · Simon Kast🇩🇪
We study a simplified model of top-flavoured dark matter in the framework of Dark Minimal Flavour Violation. In this setup the coupling of the dark matter flavour triplet to right-handed up-type quarks constitutes the only new source of flavour and CP violation. The parameter space of the model is restricted by LHC searches with missing energy final states, by neutral $D$ meson mixing data, by the observed dark matter relic abundance, and by the absence of signal in direct detection experiments. We consider all of these constraints in turn, studying their implications for the allowed parameter space. Imposing the mass limits and coupling benchmarks from collider searches, we then conduct a combined analysis of all the other constraints, revealing their non-trivial interplay. Especially interesting is the combination of direct detection and relic abundance constraints, having a severe impact on the structure of the dark matter coupling matrix. We point out that future bounds from upcoming direct detection experiments, such as XENON1T, XENONnT, LUX-ZEPLIN, and DARWIN, will exclude a large part of the parameter space and push the DM mass to higher values.
hep-phhep-exJHEP(2017)·42 citations
18*
Solar Neutrinos as a Probe of Dark Matter-Neutrino Interactions
Francesco Capozzi🇮🇹 · Ian M. Shoemaker🇺🇸 · Luca Vecchi🇮🇹
Sterile neutrinos at the eV scale have long been studied in the context of anomalies in short baseline neutrino experiments. Their cosmology can be made compatible with our understanding of the early Universe provided the sterile neutrino sector enjoys a nontrivial dynamics with exotic interactions, possibly providing a link to the Dark Matter (DM) puzzle. Interactions between DM and neutrinos have also been proposed to address the long-standing "missing satellites" problem in the field of large scale structure formation. Motivated by these considerations, in this paper we discuss realistic scenarios with light steriles coupled to DM. We point out that within this framework active neutrinos acquire an effective coupling to DM that manifests itself as a new matter potential in the propagation within a medium of asymmetric DM. Assuming that at least a small fraction of asymmetric DM has been captured by the Sun, we show that a sizable region of the parameter space of these scenarios can be probed by solar neutrino experiments, especially in the regime of small couplings and light mediators where all other probes become inefficient. In the latter regime these scenarios behave as familiar $3 + 1$ models in all channels except for solar data, where a Solar Dark MSW effect takes place. Solar Dark MSW is characterized by modifications of the most energetic $^{8}$ B and CNO neutrinos, whereas the other fluxes remain largely unaffected.
hep-phastro-ph.COastro-ph.SRhep-exJCAP(2017)·45 citations
19*
Wilsonian renormalisation of CFT correlation functions: Field theory
J. M. Lizana🇪🇸 · M. Perez-Victoria🇪🇸
We examine the precise connection between the exact renormalisation group with local couplings and the renormalisation of correlation functions of composite operators in scale-invariant theories. A geometric description of theory space allows us to select convenient non-linear parametrisations that serve different purposes. First, we identify normal parameters in which the renormalisation group flows take their simplest form; normal correlators are defined by functional differentiation with respect to these parameters. The renormalised correlation functions are given by the continuum limit of correlators associated to a cutoff-dependent parametrisation, which can be related to the renormalisation group flows. The necessary linear and non-linear counterterms in any arbitrary parametrisation arise in a natural way from a change of coordinates. We show that, in a class of minimal subtraction schemes, the renormalised correlators are exactly equal to normal correlators evaluated at a finite cutoff. To illustrate the formalism and the main results, we compare standard diagrammatic calculations in a scalar free-field theory with the structure of the perturbative solutions to the Polchinski equation close to the Gaussian fixed point.
↳ hep-thhep-phJHEP(2017)·9 citations
20*
Lattice QCD static potentials of the meson-meson and tetraquark systems computed with both quenched and full QCD
P. Bicudo🇵🇹 · M. Cardoso🇵🇹 · O. Oliveira🇵🇹 · P. J. Silva🇵🇹
We revisit the static potential for the $QQ Q ˉ Q ˉ$ system using SU(3) lattice simulations, studying both the colour singlets groundstate and first excited state. We consider geometries where the two static quarks and the two anti-quarks are at the corners of rectangles of different sizes. We analyse the transition between a tetraquark system and a two meson system with a two by two correlator matrix. We compare the potentials computed with quenched QCD and with dynamical quarks. We also compare our simulations with the results of previous studies and analyze quantitatively fits of our results with anzatse inspired in the string flip-flop model and in its possible colour excitations.
↳ hep-lathep-phPRD(2017)·19 citations
21*
Second-order dissipative hydrodynamics for plasma with chiral asymmetry and vorticity
E. V. Gorbar🇺🇦 · D. O. Rybalka🇺🇸 · I. A. Shovkovy🇺🇸
By making use of the chiral kinetic theory in the relaxation-time approximation, we derive an Israel-Stewart type formulation of the hydrodynamic equations for a chiral relativistic plasma made of neutral particles (e.g., neutrinos). The effects of chiral asymmetry are captured by including an additional continuity equation for the axial charge, as well as the leading-order quantum corrections due to the spin of particles. In a formulation of the chiral kinetic theory used, we introduce a symmetric form of the energy-momentum tensor that is suitable for the description of a weakly nonuniform chiral plasma. By construction, the energy and momentum are conserved to the same leading order in the Planck constant as the kinetic equation itself. By making use of such a chiral kinetic theory and the Chapman-Enskog approach, we obtain a set of second-order dissipative hydrodynamic equations. The effects of the fluid vorticity and velocity fluctuations on the dispersion relations of chiral vortical waves are analyzed.
↳ hep-thcond-mat.mes-hallhep-phnucl-thPRD(2017)·31 citations
22*
Compact stars in the braneworld: a new branch of stellar configurations with arbitrarily large mass
Germán Lugones🇧🇷 · José D. V. Arbañil🇵🇪
We study the properties of compact stars in the Randall-Sundrum II type braneworld model. To this end, we solve the braneworld generalization of the stellar structure equations for a static fluid distribution with spherical symmetry considering that the spacetime outside the star is described by a Schwarzschild metric. First, the stellar structure equations are integrated employing the so called causal limit equation of state (EOS), which is constructed using a well established EOS at densities below a fiducial density, and the causal EOS $P = ρ$ above it. It is a standard procedure in general relativistic stellar structure calculations to use such EOS for obtaining a limit in the mass radius diagram, known as causal limit, above which no stellar configurations are possible if the EOS fulfills that the sound velocity is smaller than the speed of light. We find that the equilibrium solutions in the braneworld model can violate the general relativistic causal limit and, for sufficiently large mass they approach asymptotically to the Schwarzschild limit $M = 2 R$ . Then, we investigate the properties of hadronic and strange quark stars using two typical EOSs. For masses below $\sim 1.5 - 2 M_{⊙}$ , the mass versus radius curves show the typical behavior found within the frame of General Relativity. However, we also find a new branch of stellar configurations that can violate the general relativistic causal limit and that in principle may have an arbitrarily large mass. The stars belonging to this new branch are supported against collapse by the nonlocal effects of the bulk on the brane. We also show that these stars are always stable under small radial perturbations. These results support the idea that traces of extra-dimensions might be found in astrophysics, specifically through the analysis of masses and radii of compact objects.
↳ gr-qcastro-ph.HEhep-phPRD(2017)·55 citations
23*
Hybrid Quark Stars With Strong Magnetic Field
T. Tatsumi🇯🇵 · H. Sotani🇯🇵
Discovery of huge magnetic field in magnetars has stimulated a renewed interest about the magnetic field and physics of compact stars, where microphysics such as QED or QCD may play active parts. Here we discuss the equation of state (EOS) of quark matter in the core of compact stars by taking into account the strong magnetic field. We show that quark EOS becomes very stiff in the presence of the strong magnetic field, and becomes stiffest under the causality condition beyond the threshold strength of $B_{c} \sim O (1 0^{19})$ G. This is because quarks make the Landau levels in the presence of the magnetic field and thereby only the lowest Landau level is occupied in the extreme case beyond $B_{c}$ . Thus quarks can freely move along the magnetic field with localization in the perpendicular plane, which resembles the quasi-one dimensional systems and gives rise to a stiff EOS. Consequently, we may easily produce high-mass stars beyond two solar mass. As another interesting possibility, we discuss the appearance of the third family of compact stars, succeeding white dwarfs and neutron stars, before collapsing into black holes. We demonstrate an example, which is specified by a discontinuous increase of the adiabatic index at the hadron-quark phase transition. Such new family may affect the supernova explosions or the gravitational wave emitted from the neutron star mergers.
↳ astro-ph.HEhep-phnucl-thPoS(2017)·0 citations
24*
Glueball spectrum from $N_{f} = 2$ lattice QCD study on anisotropic lattices
Wei Sun🇨🇳 · Long-Cheng Gui🇨🇳 · Ying Chen🇨🇳 · Ming Gong🇨🇳 · Chuan Liu🇨🇳 · Yu-Bin Liu🇨🇳 · Zhaofeng Liu🇨🇳 · Jian-Ping Ma🇨🇳 · Jian-Bo Zhang🇨🇳
The lowest-lying glueballs are investigated in lattice QCD using $N_{f} = 2$ clover Wilson fermion on anisotropic lattices. We simulate at two different and relatively heavy quark masses, corresponding to physical pion mass of $m_{π} \sim 938$ MeV and $650$ MeV. The quark mass dependence of the glueball masses have not been investigated in the present study. Only the gluonic operators built from Wilson loops are utilized in calculating the corresponding correlation functions. In the tensor channel, we obtain the ground state mass to be 2.363(39) GeV and 2.384(67) GeV at $m_{π} \sim 938$ MeV and $650$ MeV, respectively. In the pseudoscalar channel, when using the gluonic operator whose continuum limit has the form of $ϵ_{ij k} T r B_{i} D_{j} B_{k}$ , we obtain the ground state mass to be 2.573(55) GeV and 2.585(65) GeV at the two pion masses. These results are compatible with the corresponding results in the quenched approximation. In contrast, if we use the topological charge density as field operators for the pseudoscalar, the masses of the lowest state are much lighter (around 1GeV) and compatible with the expected masses of the flavor singlet $q q ˉ$ meson. This indicates that the operator $ϵ_{ij k} T r B_{i} D_{j} B_{k}$ and the topological charge density couple rather differently to the glueball states and $q q ˉ$ mesons. The observation of the light flavor singlet pseudoscalar meson can be viewed as the manifestation of effects of dynamical quarks. In the scalar channel, the ground state masses extracted from the correlation functions of gluonic operators are determined to be around 1.4-1.5 GeV, which is close to the ground state masses from the correlation functions of the quark bilinear operators. In all cases, the mixing between glueballs and conventional mesons remains to be further clarified in the future.
↳ hep-lathep-phCPC(2018)·63 citations
25*
Effects of rotation and boundaries on chiral symmetry breaking of relativistic fermions
M. N. Chernodub🇫🇷 · Shinya Gongyo🇯🇵
In order to avoid unphysical causality-violating effects any rigidly rotating system must be bounded in directions transverse to the axis of rotation. We demonstrate that this requirement implies substantial dependence of properties of relativistically rotating system on the boundary conditions. We consider a system of interacting fermions described by the Nambu-Jona-Lasinio model in a space bounded by cylindrical surface of finite radius. In order to confine the fermions inside the cylinder we impose "chiral" MIT boundary conditions on its surface. These boundary conditions are parameterized by a continuous chiral angle \Theta. We find that at any value of \Theta the chiral restoration temperature T_c decreases as a quadratic function of the angular frequency \Omega. However, the position and the slope of the critical curve T_c = T_c(\Omega) in the phase diagram depends noticeably on the value of the chiral angle.
↳ hep-thcond-mat.otherhep-phPRD(2017)·117 citations
26*
Massive Primordial Black Holes as Dark Matter and their detection with Gravitational Waves
Juan García-Bellido🇪🇸
Massive Primordial Black Holes (MPBH) can be formed after inflation due to broad peaks in the primordial curvature power spectrum that collapse gravitationally during the radiation era, to form clusters of black holes that merge and increase in mass after recombination, generating today a broad mass-spectrum of black holes with masses ranging from 0.01 to $1 0^{5} M_{⊙}$ . These MPBH could act as seeds for galaxies and quick-start structure formation, initiating reionization, forming galaxies at redshift $z > 10$ and clusters at $z > 1$ . They may also be the seeds on which SMBH and IMBH form, by accreting gas onto them and forming the centers of galaxies and quasars at high redshift. They form at rest with zero spin and have negligible cross-section with ordinary matter. If there are enough of these MPBH, they could constitute the bulk of the Dark Matter today. Such PBH could be responsible for the observed fluctuations in the CIB and X-ray backgrounds. MPBH could be directly detected by the gravitational waves emitted when they merge to form more massive black holes, as recently reported by LIGO. Their continuous merging since recombination could have generated a stochastic background of gravitational waves that could eventually be detected by LISA and PTA. MPBH may actually be responsible for the unidentified point sources seen by Fermi, Magic and Chandra. Furthermore, the ejection of stars from shallow potential wells like those of Dwarf Spheroidals (DSph), via the gravitational slingshot effect, could be due to MPBH, thus alleviating the substructure and too-big-to-fail problems of standard collisionless CDM. Their mass distribution peaks at a few tens of $M_{⊙}$ today, and could be detected also with long-duration microlensing events, as well as by the anomalous motion of stars in GAIA. Their presence as CDM in the Universe could be seen in the time-dilation of lensed images of quasars.
↳ astro-ph.COgr-qchep-phJ.Phys.Conf.Ser.(2017)·223 citations
27*
$R + α R^{n}$ Inflation in higher-dimensional Space-times
Santiago Pajón Otero🇪🇸 · Francisco G. Pedro🇪🇸 · Clemens Wieck🇪🇸
We generalise Starobinsky's model of inflation to space-times with $D > 4$ dimensions, where $D - 4$ dimensions are compactified on a suitable manifold. The $D$ -dimensional action features Einstein-Hilbert gravity, a higher-order curvature term, a cosmological constant, and potential contributions from fluxes in the compact dimensions. The existence of a stable flat direction in the four-dimensional EFT implies that the power of space-time curvature, $n$ , and the rank of the compact space fluxes, $p$ , are constrained via $n = p = D /2$ . Whenever these constraints are satisfied, a consistent single-field inflation model can be built into this setup, where the inflaton field is the same as in the four-dimensional Starobinsky model. The resulting predictions for the CMB observables are nearly indistinguishable from those of the latter.
↳ hep-thastro-ph.COhep-phJHEP(2017)·14 citations
28*
Deformations, Moduli Stabilisation and Gauge Couplings at One-Loop
Gabriele Honecker🇩🇪 · Isabel Koltermann🇩🇪 · Wieland Staessens🇪🇸
We investigate deformations of $Z_{2}$ orbifold singularities on the toroidal orbifold $T^{6} / (Z_{2} \times Z_{6})$ with discrete torsion in the framework of Type IIA orientifold model building with intersecting D6-branes wrapping special Lagrangian cycles. To this aim, we employ the hypersurface formalism developed previously for the orbifold $T^{6} / (Z_{2} \times Z_{2})$ with discrete torsion and adapt it to the $Z_{2} \times Z_{6} \times Ω R$ point group by modding out the remaining $Z_{3}$ subsymmetry and the orientifold projection $Ω R$ . We first study the local behaviour of the $Z_{3} \times Ω R$ invariant deformation orbits under non-zero deformation and then develop methods to assess the deformation effects on the fractional three-cycle volumes globally. We confirm that D6-branes supporting USp(2N) or SO(2N) gauge groups do not constrain any deformation, while deformation parameters associated to cycles wrapped by D6-branes with U(N) gauge groups are constrained by D-term supersymmetry breaking. These features are exposed in global prototype MSSM, Left-Right symmetric and Pati-Salam models first constructed in arXiv:1509.00048 and arXiv:1409.1236, for which we here count the number of stabilised moduli and study flat directions changing the values of some gauge couplings. Finally, we confront the behaviour of tree-level gauge couplings under non-vanishing deformations along flat directions with the one-loop gauge threshold corrections at the orbifold point and discuss phenomenological implications, in particular on possible LARGE volume scenarios and the corresponding value of the string scale $M_{string}$ , for the same global D6-brane models.
↳ hep-thhep-phJHEP(2017)·6 citations
29*
HAWC Observations Strongly Favor Pulsar Interpretations of the Cosmic-Ray Positron Excess
Dan Hooper🇺🇸 · Ilias Cholis🇺🇸 · Tim Linden🇺🇸 · Ke Fang🇺🇸
Recent measurements of the Geminga and B0656+14 pulsars by the gamma-ray telescope HAWC (along with earlier measurements by Milagro) indicate that these objects generate significant fluxes of very high-energy electrons. In this paper, we use the very high-energy gamma-ray intensity and spectrum of these pulsars to calculate and constrain their expected contributions to the local cosmic-ray positron spectrum. Among models that are capable of reproducing the observed characteristics of the gamma-ray emission, we find that pulsars invariably produce a flux of high-energy positrons that is similar in spectrum and magnitude to the positron fraction measured by PAMELA and AMS-02. In light of this result, we conclude that it is very likely that pulsars provide the dominant contribution to the long perplexing cosmic-ray positron excess.
↳ astro-ph.HEastro-ph.GAhep-phPRD(2017)·192 citations
30*
Cosmic strings and other topological defects in nonscaling regimes
R. P. L. Azevedo🇵🇹 · C. J. A. P. Martins🇵🇹
Cosmic strings are topological defects possibly formed in the early Universe, which may be observable due to their gravitational effects on the cosmic microwave background radiation or gravitational wave experiments. To this effect it is important to quantitatively ascertain the network properties, including their density, velocity or the number of strings present, at the various epochs in the observable Universe. Attempts to estimate these numbers often rely on simplistic approximations for the string parameters, such as assuming that the network is scaling. However, in cosmological models containing realistic amounts of radiation, matter and dark energy a string network is never exactly scaling. Here we use the velocity-dependent one-scale model for the evolution of a string network to better quantify how these networks evolve. In particular we obtain new approximate analytic solutions for the behavior of the network during the radiation-to-matter and matter-to-acceleration transitions (assuming, in the latter case, the canonical $Λ$ cold dark matter model), and numerically calculate the relevant quantities for a range of possible dark energy models.
↳ astro-ph.COgr-qchep-phhep-thPRD(2017)·19 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.