Thu·Mar 2, 2017Thursday·March 2, 2017

1. 01*

   Hadron Resonance Gas Model with Induced Surface Tension

   V. V. Sagun🇺🇦 · K. A. Bugaev🇺🇦 · A. I. Ivanytskyi🇺🇦 · I. P. Yakimenko🇸🇪 · E. G. Nikonov🇷🇺 · A.V. Taranenko🇷🇺 · C. Greiner🇩🇪 · D. B. Blaschke🇷🇺 · G. M. Zinovjev🇺🇦

   Here we present a physically transparent generalization of the multicomponent Van der Waals equation of state in the grand canonical ensemble. For the one-component case the third and fourth virial coefficients are calculated analytically. It is shown that an adjustment of a single model parameter allows us to reproduce the third and fourth virial coefficients of the gas of hard spheres with small deviations from their exact values. A thorough comparison of the compressibility factor and speed of sound of the developed model with the one and two component Carnahan-Starling equation of state is made. It is shown that the model with the induced surface tension is able to reproduce the results of the Carnahan-Starling equation of state up to the packing fractions 0.2-0.22 at which the usual Van der Waals equation of state is inapplicable. At higher packing fractions the developed equation of state is softer than the gas of hard spheres and, hence, it breaks causality in the domain where the hadronic description is expected to be inapplicable. Using this equation of state we develop an entirely new hadron resonance gas model and apply it to a description of the hadron yield ratios measured at AGS, SPS, RHIC and ALICE energies of nuclear collisions. The achieved quality of the fit per degree of freedom is about 1.08. We confirm that the strangeness enhancement factor has a peak at low AGS energies, while at and above the highest SPS energy of collisions the chemical equilibrium of strangeness is observed. We argue that the chemical equilibrium of strangeness, i.e. ${\gamma }_s\simeq 1$, observed above the center of mass collision energy 4.3 GeV may be related to the hadronization of quark gluon bags which have the Hagedorn mass spectrum, and, hence, it may be a new signal for the onset of deconfinement.

   hep-phEPJA(2018)·60 citations
2. 02*

   Probing light sterile neutrino signatures at reactor and Spallation Neutron Source neutrino experiments

   T.S. Kosmas🇬🇷 · D.K. Papoulias🇬🇷 · M. Tortola🇪🇸 · J.W.F. Valle🇪🇸

   We investigate the impact of a fourth sterile neutrino at reactor and Spallation Neutron Source neutrino detectors. Specifically, we explore the discovery potential of the TEXONO and COHERENT experiments to subleading sterile neutrino effects through the measurement of the coherent elastic neutrino-nucleus scattering event rate. Our dedicated ${\chi }^2$-sensitivity analysis employs realistic nuclear structure calculations adequate for high purity sub-keV threshold Germanium detectors.

   hep-phPRD(2017)·95 citations
3. 03*

   An Analytic Analysis of the Pion Decay Constant in Three-Flavoured Chiral Perturbation Theory

   B. Ananthanarayan🇮🇳 · Johan Bijnens🇸🇪 · Shayan Ghosh🇮🇳

   A representation of the two-loop contribution to the pion decay constant in $SU(3)$ chiral perturbation theory is presented. The result is analytic upto the contribution of the three (different) mass sunset integrals, for which an expansion in their external momentum has been taken. We also give an analytic expression for the two-loop contribution to the pion mass based on a renormalized representation and in terms of the physical eta mass. We find an expansion of $F_{\pi }$ and $M_{\pi }^2$ in the strange quark mass in the isospin limit, and perform the matching of the chiral SU(2) and SU(3) low energy constants. A numerical analysis demonstrates the high accuracy of our representation, and the strong dependence of the pion decay constant upon the values of the low energy constants, especially in the chiral limit. Finally, we present a simplified representation that is particularly suitable for fitting with available lattice data.

   hep-phhep-latEPJC(2017)·15 citations
4. 04*

   Single production of dark photon at the LHC

   Zhi-Cheng Liu🇨🇳 · Chong-Xing Yue🇨🇳 · Yu-Chen Guo🇨🇳

   Many extensions of the SM contain hidden sectors which are uncharged under the SM gauge group. The simplest model with an additional $U(1)$ group predicts the existence of the new gauge boson, dark photon $Z_D$. In this work we consider single production of dark photon $Z_D$ at the LHC and study its discovery potential via the process $pp\to Z_D\gamma \to ll\gamma$. After simulating the signal as well as the relevant backgrounds, the numerical results show that the signal of $Z_D$ might be detected at the 14TeV LHC.

   hep-ph4 citations
5. 05*

   Study of $B_c^{\ast }$ $\to$ $\psi (1S,2S)P$, ${\eta }_c(1S,2S)P$ weak decays

   Junfeng Sun🇨🇳 · Yueling Yang🇨🇳 · Na Wang🇨🇳 · Jinshu Huang🇨🇳 · Qin Chang🇨🇳

   Motivated by the potential prospects of the $B_c^{\ast }$ meson samples at hadron colliders, the bottom-changing $B_c^{\ast }$ $\to$ $\psi (1S,2S)P$, ${\eta }_c(1S,2S)P$ weak decays are first studied with the perturbative QCD approach, where $P$ $=$ $\pi$ and $K$. It is found that branching ratio of the CKM-favored $B_c^{\ast }$ $\to$ $J/\psi \pi$ decay is about $\sim$ $\mathcal{O}(10^{-8})$, which might be measurable at the future LHC experiments.

   hep-phhep-exPRD(2017)·10 citations
6. 06*

   Study on the ${\rm Y}(1S)$ $\to$ $B_c{D}_s$ decay

   Junfeng Sun🇨🇳 · Yueling Yang🇨🇳 · Qingxia Li🇨🇳 · Haiyan Li🇨🇳 · Na Wang🇨🇳 · Qin Chang🇨🇳 · Jinshu Huang🇨🇳

   The branching ratio and direct $CP$ asymmetry of the ${\rm Y}(1S)$ $\to$ $B_c{D}_s$ weak decay are estimated with the perturbative QCD approach. It is found that (1) The direct $CP$-violating asymmetry is close to zero. (2) the branching ratio $\mathcal{B}r({\rm Y}(1S)\to B_c{D}_s)$ $\gtrsim$ $10^{-10}$ might be measurable at the future experiments.

   hep-phNPB(2016)·2 citations
7. 07*

   Properties of 2+1-flavor QCD in the imaginary chemical potential region: model prediction

   Junpei Sugano🇯🇵 · Hiroaki Kouno🇯🇵 · Masanobu Yahiro🇯🇵

   We study properties of 2+1-flavor QCD in the imaginary chemical potential region by using two approaches. One is a theoretical approach based on QCD partition function, and the other is a qualitative one based on the Polyakov-loop extended Nambu--Jona-Lasinio (PNJL) model. In the theoretical approach, we clarify conditions imposed on the imaginary chemical potentials ${\mu }_f=i{\theta }_{f}T$ to realize the Roberge-Weiss (RW) periodicity. We also show that the RW periodicity is broken if anyone of ${\theta }_f$ is fixed to a constant value. In order to visualize the condition, we use the PNJL model as a model possessing the RW periodicity, and draw the phase diagram as a function of ${\theta }_u={\theta }_d\equiv {\theta }_l$ for two conditions of ${\theta }_s={\theta }_l$ and ${\theta }_s=0$. We also consider two cases, $({\mu }_u,{\mu }_d,{\mu }_s)=(i{\theta }_{u}T,i{C}_{1}T,0)$ and $({\mu }_u,{\mu }_d,{\mu }_s)=(i{C}_{2}T,i{C}_{2}T,i{\theta }_{s}T)$; here $C_1$ and $C_2$ are dimensionless constants, whereas ${\theta }_u$ and ${\theta }_s$ are treated as variables. For some choice of $C_1$ ($C_2$), the number density of up (strange) quark becomes smooth in the entire region of ${\theta }_u$ (${\theta }_s$) even in high $T$ region.

   hep-phPRD(2017)·3 citations
8. 08*

   Asymmetric Dark Matter and Baryogenesis from $SU(2{)}_{\ell }$

   Bartosz Fornal🇺🇸 · Yuri Shirman🇺🇸 · Tim M. P. Tait🇺🇸 · Jennifer Rittenhouse West🇺🇸

   We propose a theory in which the Standard Model gauge symmetry is extended by a new $SU(2{)}_{\ell }$ group acting nontrivially on the lepton sector which is spontaneously broken at the TeV scale. Under this $SU(2{)}_{\ell }$ the ordinary leptons form doublets along with new lepton partner fields. This construction naturally contains a dark matter candidate, the partner of the right-handed neutrino, stabilized by a residual global $U(1{)}_{\chi }$ symmetry. We show that one can explain baryogenesis through an asymmetric dark matter scenario, in which generation of related asymmetries in the dark matter and baryon sectors is driven by the $SU(2{)}_{\ell }$ instantons during a first order phase transition in the early universe.

   hep-phPRD(2017)·31 citations
9. 09*

   Data driven method for predicting the shape of the dijet mass in $Zh+{E_{\mathrm{T}}}^{\mathrm{miss}}$ analysis

   Skhathisomusa Mthembu🇿🇦 · Shell May Liao🇿🇦 · Tshidiso Molupe🇿🇦 · Bruce Mellado🇿🇦 · Deepak Kar🇿🇦

   We present an analysis of new physics searches in $Zh$ with missing energy final states at the Large Hadron Collider considering $Z\to l^{+}{l}^{-}$ (where $l^{\pm }=e^{\pm },{\mu }^{\pm }$) and $h\to b\bar{b}$ decay modes. For this analysis we consider production of a $CP$-odd scalar $A$ through gluon-fusion which decay into a heavy $CP$-even neutral scalar $H$ with $Z$-boson. Further $H$ decays into a lighter $CP$-even Higgs boson $h$ in association with dark matter candidate $\chi$ - a source of missing energy. The masses of these scalars are considered as $m_h=125$ GeV, $m_{\chi }=60$ GeV, $2m_h<m_H<2m_t$ and $m_A>2m_t$. A data-driven method have been applied to reduce the considerable backgrounds from electroweak processes $W$+ jets and $Z$+ jets, in addition with top-pair and single-top production. The di-jet mass distributions have been studied with same- and opposite-flavour lepton selections.

   hep-ph0 citations
10. 10*

    Muon g-2 in an Alternative Quasi-Yukawa Unification with Low Fine-Tuned Inverse SeeSaw Mechanism

    Zafer Altin🇹🇷 · Ozer Ozdal🇨🇦 · Cem Salih Un🇹🇷

    We explore the low scale implications of the Pati-Salam Model including the TeV scale right-handed neutrinos interacting and mixing with the MSSM fields through the inverse seesaw (IS) mechanism in the light of the muon anomalous magnetic moment (muon g-2) resolution, and highlight the solutions which are compatible with the Quasi-Yukawa Unification condition (QYU). We find that the presence of the right-handed neutrinos causes heavy smuons >~ 800 GeV in order to avoid tachyonic staus at the low scale. On the other hand, the sneutrinos can be as light as about 100 GeV along with the light charginos of mass <~ 400 GeV, they can yield so large contributions to muon g-2 that the discrepancy between the experiment and the theory can be resolved. In addition, the model predicts relatively light Higgsinos (<~ 700 GeV); and hence the second chargino mass is also light enough (<~ 700 GeV) to contribute to muon g-2. Light Higgsinos also yield less fine-tuning at the electroweak scale, and the regions compatible with muon g-2 restricts Delta_EW <~ 100 strictly, and this region also satisfies the QYU condition. In addition, the ratios among the Yukawa couplings should be 1.8 <~ y_t/y_b <~ 2.6, y_tau/y_b ~ 1.3 to yield correct fermion masses. Even though the right-handed neutrino Yukawa coupling can be varied freely, the solutions bound its range to 0.8 <~ y_nu/y_b <~ 1.7.

    hep-phPRD(2018)·19 citations
11. 11*

    An investigation on the leading and subleading high-energy behavior of hadron-hadron total cross sections using a best-fit analysis of hadronic scattering data

    M. Giordano🇭🇺 · E. Meggiolaro🇮🇹 · P.V.R.G. Silva🇧🇷

    In the present investigation we study the leading and subleading high-energy behavior of hadron-hadron total cross sections using a best-fit analysis of hadronic scattering data. The parametrization used for the hadron-hadron total cross sections at high energy is inspired by recent results obtained by Giordano and Meggiolaro (2014) using a nonperturbative approach in the framework of QCD and it reads ${\sigma }_{\text{tot}}\sim B{\ln }^{2}s+C\ln s\ln \ln s$. Both $B$ and $C$ are obtained by means of best-fits to data for proton-proton and antiproton-proton scattering, including recent data obtained at the LHC, and also to data for other meson-baryon and baryon-baryon scattering processes. The results are compared to the theoretical predictions existing in the literature. In particular, following the above-mentioned nonperturbative QCD approach, we also consider fits where the parameters $B$ and $C$ are set to $B=\kappa B_{\text{th}}$ and $C=\kappa C_{\text{th}}$, where $B_{\text{th}}$ and $C_{\text{th}}$ are universal quantities related to the QCD stable spectrum, while $\kappa$ (treated as an extra free parameter) is related to the asymptotic value of the ratio ${\sigma }_{\text{el}}/{\sigma }_{\text{tot}}$. Different possible scenarios are then considered and compared.

    hep-phhep-exPRD(2017)·3 citations
12. 12*

    Generalized degeneracies and their resolution in neutrino oscillation experiments

    Newton Nath🇮🇳 · Srubabati Goswami🇮🇳 · K.N. Deepthi🇮🇳

    We discuss a comprehensive way to study the parameter degeneracies in the form of a generalized degeneracy in the neutrino oscillation experiments. First we describe the various degeneracies by considering only neutrino run of the long baseline experiment (LBL), NO$\nu$A. Then we discuss the role of antineutrinos. Later, we present the combined role of T2K (LBL experiment) and ICAL@INO (atmospheric experiment) to resolve these degeneracies. We also discuss the affect of new physics like non-standards interactions (NSI) on the determination of neutrino mass hierarchy in DUNE.

    hep-phSpringer Proc.Phys.(2018)·1 citation
13. 13*

    Mass of the Stabilized Radion in the Limit of Finite Quartic Coupling

    Ali Tofighi🇮🇷 · Vahid Reza Shajiee🇮🇷

    We present an exact treatment of the modulus stabilization condition with the general boundary conditions of the bulk scalar field in the Randall-Sundrum model. We find analytical expressions for the value of the modulus and the mass of the radion.

    hep-phhep-thAdv.High Energy Phys.(2017)·1 citation
14. 14*

    Wilson coefficients of dimension 6 gluon operators with spin indices in the heavy quark current correlation functions

    HyungJoo Kim🇰🇷 · Su Houng Lee🇰🇷

    We calculate the Wilson coefficients of dimension 6 gluon operators with spin indices in the two point correlation function of the heavy scalar, pseudoscalar, and axialvector currents. Our result completes the list of all Wilson coefficients of gluon operators up to dimension 6 for the correlation functions between heavy quark currents without derivatives. We then use the result to investigate the stability of the QCD sum rule results for the ${\eta }_c$, $J/\Psi$, ${\chi }_{c0}$, and ${\chi }_{c1}$ mesons near $T_c$. While the inclusion of the dimension 6 operators increases the stability of the sum rules for all currents, all of them break down slightly above $T_c$ with that for the $J/\psi$ persisting to relatively highest temperature.

    hep-phNPA(2017)·2 citations
15. 15*

    Light Neutralino Dark Matter in the NMSSM

    Qiurong Mou · Hongyan Wu · Sibo Zheng

    The next-to-minimal supersymmetric standard model can host light neutralino dark matter with mass of order GeV scale. It is dominated by the singlino component as a result of approximate Peccei-Quinn symmetry. This paper is devoted to address the question how light such neutralino dark matter can be in the light of the LHC Run 1 data as well as the latest LUX and Xenon1T limits. In particular, we show the sensitivity of parameter space of dark matter mass with respect to $Z$ boson and SM Higgs invisible decay.

    hep-phhep-ex8 citations
16. 16*

    GPDs at non-zero skewness in ADS/QCD model

    Matteo Rinaldi🇪🇸

    We study Generalized Parton Distribution functions (GPDs) usually measured in hard exclusive processes and encoding information on the three dimensional partonic structure of hadrons and their spin decomposition, for non zero skewness within the AdS/QCD formalism. To this aim the canonical scheme to calculate GPDs at zero skewness has been properly generalized. Furthermore, we show that the latter quantities, in this non forward regime, are sensitive to non trivial details of the hadronic light front wave function, such as a kind of parton correlations usually not accessible in studies of form factors and GPDs at zero skewness.

    hep-phnucl-thPLB(2017)·25 citations
17. 17*

    Well-tempered n-plet dark matter

    A. Bharucha🇫🇷 · F. Brümmer🇫🇷 · R. Ruffault🇫🇷

    We study simple effective models of fermionic WIMP dark matter, where the dark matter candidate is a mixture of a Standard Model singlet and an n-plet of SU(2) with n >= 3, stabilized by a discrete symmetry. The dark matter mass is assumed to be around the electroweak scale, and the mixing is generated by higher-dimensional operators, with a cutoff scale > 1 TeV. For appropriate values of the mass parameters and the mixing we find that the observed dark matter relic density can be generated by coannihilation. Direct detection experiments have already excluded large parts of the parameter space, and the next-generation experiments will further constrain these models.

    hep-phJHEP(2017)·15 citations
18. 18*

    Electromagnetic properties of massive neutrinos in low-energy elastic neutrino-electron scattering

    Konstantin A. Kouzakov🇷🇺 · Alexander I. Studenikin🇷🇺

    A thorough account of electromagnetic interactions of massive neutrinos in the theoretical formulation of low-energy elastic neutrino-electron scattering is given. The formalism of neutrino charge, magnetic, electric, and anapole form factors defined as matrices in the mass basis is employed under the assumption of three-neutrino mixing. The flavor change of neutrinos traveling from the source to the detector is taken into account and the role of the source-detector distance is inspected. The effects of neutrino flavor-transition millicharges and charge radii in the scattering experiments are pointed out.

    hep-phhep-exPRD(2017)·73 citations
19. 19*

    Dark-photon searches via $ZH$ production at $e^{+}{e}^{-}$ colliders

    Sanjoy Biswas🇰🇷 · Emidio Gabrielli🇮🇹 · Matti Heikinheimo🇫🇮 · Barbara Mele🇮🇹

    We study the $ZH$ associated production followed by the Higgs $H\to \gamma \bar{\gamma }$ decay into a photon plus an invisible and massless dark photon, at future high-energy $e^{+}{e}^{-}$ facilities. Large $H\to \gamma \bar{\gamma }$ decay rates (with branching ratios up to a few percent) are allowed, thanks to possible non-decoupling properties of the Higgs boson under specific conditions, and unsuppressed dark-photon couplings in the dark sector. Such large decay rates can be obtained in the framework of recent flavor models that aim to naturally explain the observed spread in the fermion mass spectrum. We analyze the experimental prospects for observing the $e^{+}{e}^{-}\to ZH$ process followed by the semi invisible Higgs decay into a photon plus a massless invisible system. Search strategies for both the leptonic and the hadronic final states (arising from $Z\to {\mu }^{+}{\mu }^{-}$ and $Z\to q\bar{q}$, respectively) are outlined. We find that a $5\sigma$ sensitivity to a branching fraction $B{R}_{\gamma \bar{\gamma }}\sim 3\times 10^{-4}$ can be achieved by combining the two channels with an integrated luminosity of 10 ab${}^{-1}$ at a c.m. energy of 240 GeV. This is considerably better than the corresponding sensitivity in alternative channels previously studied at lepton colliders. The analysis is model independent, and its results can be straightforwardly applied to the search of any Higgs two-body decay into a photon plus an undetected light particle.

    hep-phhep-exPRD(2017)·24 citations
20. 20*

    Searches for new physics at the Hyper-Kamiokande experiment

    Kevin J. Kelly🇺🇸

    We investigate the ability of the upcoming Hyper-Kamiokande (Hyper-K) neutrino experiment to detect new physics phenomena beyond the standard, three-massive-neutrinos paradigm; namely the existence of a fourth, sterile neutrino or weaker-than-weak, non-standard neutrino interactions. With both beam-based neutrinos from the Japan Proton Accelerator Research Complex (J-PARC) and atmospheric neutrinos, Hyper-K is capable of exploring new ranges of parameter space in these new-physics scenarios. We find that Hyper-K has comparable capability to the upcoming Deep Underground Neutrino Experiment (DUNE), and that combining both beam- and atmospheric-based data can clear up degeneracies in the parameter spaces of interest. We also comment on the potential improvement in searches for new physics if a combined analysis were performed using Hyper-K and DUNE data.

    hep-phhep-exPRD(2017)·34 citations
21. 21*

    Imaging Galactic Dark Matter with High-Energy Cosmic Neutrinos

    Carlos A. Argüelles🇺🇸 · Ali Kheirandish🇺🇸 · Aaron C. Vincent🇬🇧

    We show that the high-energy cosmic neutrinos seen by the IceCube Neutrino Observatory can be used to probe interactions between neutrinos and the dark sector that cannot be reached by current cosmological methods. The origin of the observed neutrinos is still unknown, and their arrival directions are compatible with an isotropic distribution. This observation, together with dedicated studies of Galactic plane correlations, suggest a predominantly extragalactic origin. Interactions between this isotropic extragalactic flux and the dense dark matter (DM) bulge of the Milky Way would thus lead to an observable imprint on the distribution, which would be seen by IceCube as 1) slightly suppressed fluxes at energies below a PeV and 2) a deficit of events in the direction of the Galactic center. We perform an extended unbinned likelihood analysis using the four-year high-energy starting event dataset to constrain the strength of DM-neutrino interactions for two model classes. We find that, in spite of low statistics, IceCube can probe regions of the parameter space inaccessible to current cosmological methods.

    hep-phastro-ph.HEPRL(2017)·111 citations
22. 22*

    Simplified Phenomenology for Colored Dark Sectors

    Sonia El Hedri🇩🇪 · Anna Kaminska🇩🇪 · Maikel de Vries🇩🇪 · Jose Zurita🇩🇪

    We perform a general study of the relic density and LHC constraints on simplified models where the dark matter coannihilates with a strongly interacting particle X. In these models, the dark matter depletion is driven by the self-annihilation of X to pairs of quarks and gluons through the strong interaction. The phenomenology of these scenarios therefore only depends on the dark matter mass and the mass splitting between dark matter and X as well as the quantum numbers of X. In this paper, we consider simplified models where X can be either a scalar, a fermion or a vector, as well as a color triplet, sextet or octet. We compute the dark matter relic density constraints taking into account Sommerfeld corrections and bound state formation. Furthermore, we examine the restrictions from thermal equilibrium, the lifetime of X and the current and future LHC bounds on X pair production. All constraints are comprehensively presented in the mass splitting versus dark matter mass plane. While the relic density constraints can lead to upper bounds on the dark matter mass ranging from 2 TeV to more than 10 TeV across our models, the prospective LHC bounds range from 800 to 1500 GeV. A full coverage of the strongly coannihilating dark matter parameter space would therefore require hadron colliders with significantly higher center of mass energies.

    hep-phJHEP(2017)·45 citations
23. 23*

    Unitary null energy condition violation in $P(X)$ cosmologies

    Claudia de Rham🇺🇸 · Scott Melville🇬🇧

    A non-singular cosmological bounce in the Einstein frame can only take place if the Null Energy Condition (NEC) is violated. We explore situations where a single scalar field drives the NEC violation and derive the constraints imposed by demanding tree level unitarity on a cosmological background. We then focus on the explicit constraints that arise in P(X) theories and show that constraints from perturbative unitarity make it impossible for the NEC violation to occur within the region of validity of the effective field theory without also involving irrelevant operators that arise at a higher scale that would enter from integrating out more massive degrees of freedom. Within the context of P(X) theories we show that including such operators allows for a bounce that does not manifestly violate tree level unitarity, but at the price of either imposing a shift symmetry or involving technically unnatural small operator coefficients within the low-energy effective field theory.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2017)·66 citations
24. 24*

    Photons from the Early Stages of Relativistic Heavy Ion Collisions

    L. Oliva🇮🇹 · M. Ruggieri🇨🇳 · S. Plumari🇮🇹 · F. Scardina🇮🇹 · G. X. Peng🇨🇳 · V. Greco🇮🇹

    We present results about photons production in relativistic heavy ion collisions. The main novelty of our study is the calculation of the contribution of the early stage photons to the photon spectrum. The initial stage is modeled by an ensemble of classical gluon fields which decay to a quark-gluon plasma via the Schwinger mechanism, and the evolution of the system is studied by coupling classical field equations to relativistic kinetic theory; photons production is then computed by including the pertinent collision processes into the collision integral. We find that the contribution of the early stage photons to the direct photon spectrum is substantial for $p_T\approx 2$ GeV and higher, the exact value depending on the collision energy; therefore we identify this part of the photon spectrum as the sign of the early stage. Moreover, the amount of photons produced during the early stage is not negligible with respect to those produced by a thermalized quark-gluon plasma: we support the idea that there is no dark age in relativistic heavy ion collisions.

    ↳ nucl-thhep-exhep-phnucl-exPRC(2017)·27 citations
25. 25*

    The Gravitational-Wave Physics

    Rong-Gen Cai🇨🇳 · Zhoujian Cao🇨🇳 · Zong-Kuan Guo🇨🇳 · Shao-Jiang Wang🇨🇳 · Tao Yang🇨🇳

    The direct detection of gravitational wave by Laser Interferometer Gravitational-Wave Observatory indicates the coming of the era of gravitational-wave astronomy and gravitational-wave cosmology. It is expected that more and more gravitational-wave events will be detected by currently existing and planned gravitational-wave detectors. The gravitational waves open a new window to explore the Universe and various mysteries will be disclosed through the gravitational-wave detection, combined with other cosmological probes. The gravitational-wave physics is not only related to gravitation theory, but also is closely tied to fundamental physics, cosmology and astrophysics. In this review article, three kinds of sources of gravitational waves and relevant physics will be discussed, namely gravitational waves produced during the inflation and preheating phases of the Universe, the gravitational waves produced during the first-order phase transition as the Universe cools down and the gravitational waves from the three phases: inspiral, merger and ringdown of a compact binary system, respectively. We will also discuss the gravitational waves as a standard siren to explore the evolution of the Universe.

    ↳ gr-qcastro-ph.COhep-phhep-thNatl.Sci.Rev.(2017)·194 citations
26. 26*

    Grand Unified Brane World Scenario

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

    We present a field theoretical model unifying grand unified theory (GUT) and brane world scenario. As a concrete example, we consider $SU(5)$ GUT in 4+1 dimensions where our 3+1 dimensional spacetime spontaneously arises on five domain walls. A field-dependent gauge kinetic term is used to localize massless non-Abelian gauge fields on the domain walls and to assure the charge universality of matter fields. We find the domain walls with the symmetry breaking $SU(5)\to SU(3)\times SU(2)\times U(1)$ as a global minimum and all the undesirable moduli are stabilized with the mass scale of $M_{\mathrm{GUT}}$. Profiles of massless Standard Model particles are determined as a consequence of wall dynamics. The proton decay can be exponentially suppressed.

    ↳ hep-thhep-phPRD(2017)·20 citations
27. 27*

    Tiny Electromagnetic Explosions

    Christopher Thompson (CITA)🇨🇦

    This paper considers electromagnetic transients of a modest total energy ($\mathcal{E}\gtrsim 10^{40}$ erg) and small initial size ($\mathcal{R}\gtrsim 10^{-1}$ cm). They could be produced during collisions between relativistic field structures (e.g. macroscopic magnetic dipoles) that formed around, or before, cosmic electroweak symmetry breaking. The outflowing energy has a dominant electromagnetic component; a subdominant thermal component (temperature $>1$ GeV) supplies inertia in the form of residual $e^{\pm }$. A thin shell forms that expands subluminally, attaining a Lorentz factor $\sim 10^{6-7}$ before decelerating. Drag is supplied by the reflection of an ambient magnetic field, and by deflection of ambient free electrons. Emission of low-frequency (GHz-THz) superluminal waves takes place through three channels: i) reflection of the ambient magnetic field; ii) direct linear conversion of the embedded magnetic field into a superluminal mode; and iii) excitation outside the shell by corrugation of its surface. The escaping electromagnetic pulse is very narrow (a few wavelengths) and so the width of the detected transient is dominated by propagation effects. GHz radio transients are emitted from i) the dark matter halos of galaxies and ii) the near-horizon regions of supermassive black holes that formed by direct gas collapse and now accrete slowly. Brighter and much narrower 0.01-1 THz pulses are predicted at a rate at least comparable to fast radio bursts, experiencing weaker scattering and absorption. The same explosions also accelerate protons up to $\sim 10^{19}$ eV and heavier nuclei up to $10^{20-21}$ eV.

    ↳ astro-ph.HEhep-phApJ(2017)·22 citations
28. 28*

    Giant Primeval Magnetic Dipoles

    Christopher Thompson (CITA)🇨🇦

    Macroscopic magnetic dipoles are considered as cosmic dark matter. Permanent magnetism in relativistic field structures can involve some form of superconductivity, one example being current-carrying string loops (`springs') with vanishing net tension. We derive the cross section for free classical dipoles to collide, finding it depends weakly on orientation when mutual precession is rapid. The collision rate of `spring' loops with tension $\mathcal{T}\sim 10^{-8}{c}^4/G$ in galactic halos approaches the measured rate of fast radio bursts (FRBs) if the loops comprise most of the dark matter. A large superconducting dipole (LSD) with mass $\sim 10^{20}$ g and size $\sim 1$ mm will form a $\sim 100$ km magnetosphere moving through interstellar plasma. Although hydromagnetic drag is generally weak, it is strong enough to capture some LSDs into long-lived rings orbiting supermassive black holes (SMBHs) that form by the direct collapse of massive gas clouds. Repeated collisions near young SMBHs could dominate the global collision rate, thereby broadening the dipole mass spectrum. Colliding LSDs produce tiny, hot electromagnetic explosions. The accompanying paper shows that these explosions couple effectively to propagating low-frequency electromagnetic modes, with output peaking at 0.01-1 THz. We describe several constraints on, and predictions of, LSDs as cosmic dark matter. The shock formed by an infalling LSD triggers self-sustained thermonuclear burning in a C/O (ONeMg) white dwarf (WD) of mass $\gtrsim 1M_{\odot }$ ($1.3M_{\odot }$). The spark is generally located well off the center of the WD. The rate of LSD-induced explosions matches the observed rate of Type Ia supernovae.

    ↳ astro-ph.HEhep-phApJ(2017)·15 citations
29. 29*

    Stochastic inflation in phase space: Is slow roll a stochastic attractor?

    Julien Grain🇫🇷 · Vincent Vennin🇬🇧

    An appealing feature of inflationary cosmology is the presence of a phase-space attractor, "slow roll", which washes out the dependence on initial field velocities. We investigate the robustness of this property under backreaction from quantum fluctuations using the stochastic inflation formalism in the phase-space approach. A Hamiltonian formulation of stochastic inflation is presented, where it is shown that the coarse-graining procedure - where wavelengths smaller than the Hubble radius are integrated out - preserves the canonical structure of free fields. This means that different sets of canonical variables give rise to the same probability distribution which clarifies the literature with respect to this issue. The role played by the quantum-to-classical transition is also analysed and is shown to constrain the coarse-graining scale. In the case of free fields, we find that quantum diffusion is aligned in phase space with the slow-roll direction. This implies that the classical slow-roll attractor is immune to stochastic effects and thus generalises to a stochastic attractor regardless of initial conditions, with a relaxation time at least as short as in the classical system. For non-test fields or for test fields with non-linear self interactions however, quantum diffusion and the classical slow-roll flow are misaligned. We derive a condition on the coarse-graining scale so that observational corrections from this misalignment are negligible at leading order in slow roll.

    ↳ gr-qchep-phhep-thJCAP(2017)·120 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.