Thu·Jul 7, 2016Thursday·July 7, 2016

1. 01*

   Feebly Interacting Dark Matter Particle as the Inflaton

   Tommi Tenkanen🇫🇮

   We present a scenario where a $Z_2$-symmetric scalar field $\varphi$ first drives cosmic inflation, then reheats the Universe but remains out-of-equilibrium itself, and finally comprises the observed dark matter abundance, produced by particle decays à la freeze-in mechanism. We work model-independently without specifying the interactions of the scalar field besides its self-interaction coupling, $\lambda {\varphi }^4$, non-minimal coupling to gravity, $\xi {\varphi }^{2}R$, and coupling to another scalar field, $g{\varphi }^2{\sigma }^2$. We find the scalar field $\varphi$ serves both as the inflaton and a dark matter candidate if $10^{-9}\lesssim \lambda \lesssim g\lesssim 10^{-7}$ and $3\mathrm{keV}\lesssim {\mathrm{m}}_{\varphi }\lesssim 85\mathrm{MeV}$ for $\xi =\mathcal{O}(1)$. Such a small value of the non-minimal coupling is also found to be of the right magnitude to produce the observed curvature perturbation amplitude within the scenario. We also discuss how the model may be distinguished from other inflationary models of the same type by the next generation CMB satellites.

   hep-phastro-ph.COJHEP(2016)·55 citations
2. 02*

   How to understand the underlying structures of $X(4140)$, $X(4274)$, $X(4500)$ and $X(4700)$

   Xiao-Hai Liu🇯🇵

   We investigate the possible rescattering effects which may contribute to the process $B^{+}\to J/\psi \varphi K^{+}$. It is shown that the $D_s^{\ast +}{D}_s^{-}$ rescattering via the open-charmed meson loops, and ${\psi }^{\prime }\varphi$ rescattering via the ${\psi }^{\prime }{K}_1$ loops may simulate the structures of $X(4140)$ and $X(4700)$, respectively. However, if the quantum numbers of $X(4274)$ ($X(4500)$) are $1^{++}$ ($0^{++}$), it is hard to to ascribe the observation of $X(4274)$ and $X(4500)$ to the $P$-wave threshold rescattering effects, which implies that $X(4274)$ and $X(4500)$ could be genuine resonances. We also suggest that $X(4274)$ may be the conventional orbitally excited state ${\chi }_{c1}(3P)$.

   hep-phPLB(2017)·43 citations
3. 03*

   Electron contribution to $(g-2{)}_{\mu }$ at four loops

   Alexander Kurz🇩🇪 · Tao Liu🇨🇦 · Peter Marquard🇩🇪 · Alexander V. Smirnov🇷🇺 · Vladimir A. Smirnov🇷🇺 · Matthias Steinhauser🇩🇪

   In this contribution we summarize the recent calculation of the complete electron contribution to the anomalous magnetic moment of the muon at four-loop order.

   hep-phPoS(2016)·4 citations
4. 04*

   Lorentz invariant CPT breaking in the Dirac equation

   Kazuo Fujikawa🇯🇵 · Anca Tureanu🇫🇮

   If one modifies the Dirac equation in momentum space to $[{\gamma }^{\mu }{p}_{\mu }-m-\Delta m(\theta (p_0)-\theta (-p_0))\theta (p_{\mu }^2)]\psi (p)=0$, the symmetry of positive and negative energy eigenvalues is lifted by $m\pm \Delta m$ for a small $\Delta m$. The mass degeneracy of the particle and antiparticle is thus lifted in a Lorentz invariant manner since the combinations $\theta (\pm p_0)\theta (p_{\mu }^2)$ with step functions are manifestly Lorentz invariant. We explain an explicit construction of this CPT breaking term in coordinate space, which is Lorentz invariant but non-local at a distance scale of the Planck length. The application of this Lorentz invariant CPT breaking mechanism to the possible mass splitting of the neutrino and antineutrino in the Standard Model is briefly discussed.

   hep-phInt.J.Mod.Phys.A(2017)·6 citations
5. 05*

   Testing a dynamical origin of Standard Model fermion masses

   Tommi Alanne🇩🇰 · Diogo Buarque Franzosi🇩🇪 · Mads T. Frandsen🇩🇰

   We discuss a test of the Standard Model fermion mass origin in models of dynamical electroweak symmetry breaking. The couplings of composite pseudoscalar resonances to top quarks allow to distinguish high-scale Extended-Technicolor-type fermion mass generation from fermion partial compositeness and low-scale mass generation via an induced vacuum expectation value of a doublet coupled to the composite sector. These different possible origins of fermion masses are thus accessible via weak-scale physics searched for at the LHC.

   hep-phPRD(2016)·17 citations
6. 06*

   Phenomenology of Bulk Scalar Singlets in the Randall Sundrum Model

   Fayez Abu-Ajamieh🇺🇸 · Rachel Houtz🇺🇸 · Rui Zheng🇺🇸

   We present a Randall-Sundrum toy model with an added scalar singlet that couples only to KK fermions in the bulk. Such a scalar would nontrivially affect radion phenomenology. In addition, we examine the radion phenomenology in light of the new scalar and show how this scalar could present another probe to search for the radion.

   hep-phhep-thInt.J.Mod.Phys.A(2017)·5 citations
7. 07*

   Dark matter, light mediators, and the neutrino floor

   James B. Dent🇺🇸 · Bhaskar Dutta🇺🇸 · Jayden L. Newstead🇺🇸 · Louis E. Strigari🇺🇸

   We analyze future direct data matter detection experiments using Effective Field Theory (EFT) operators with light, $\lesssim 100$ MeV mass mediators. We compare the nuclear recoil energy spectra from these operators to the predicted high energy solar neutrino spectrum. A set of operators that generate spectra similar to the neutrino background is identified, however this set is distinct from those that mimic the neutrino background for heavy, $\gtrsim 100$ MeV mass mediators. We outline a general classification scheme based on momentum dependence of the dark matter-nucleus interaction to determine how strong the discovery limit for a given operator saturates in the presence of the neutrino background. Our results highlight the benefit of considering a general theoretical framework regarding dark matter, and motivate continued experimental progress towards lower nuclear recoil energy thresholds.

   hep-phastro-ph.HEPRD(2017)·40 citations
8. 08*

   Freeze-in Production of Sterile Neutrino Dark Matter in U(1)${}_{\mathrm{B}-\mathrm{L}}$ Model

   Anirban Biswas🇮🇳 · Aritra Gupta🇮🇳

   With the advent of new and more sensitive direct detection experiments, scope for a thermal WIMP explanation of dark matter (DM) has become extremely constricted. The non-observation of thermal WIMP in these experiments has put a strong upper bound on WIMP-nucleon scattering cross section and within a few years it is likely to touch the neutrino floor. Hence in all probability, DM may have some non-thermal origin. In this work we explore in detail this possibility of a non-thermal sterile neutrino DM within the framework of U(1)${}_{\mathrm{B}-\mathrm{L}}$ model. The U(1)${}_{\mathrm{B}-\mathrm{L}}$ model on the other hand is a well-motivated and minimal way of extending the standard model so that it can explain the neutrino masses via Type-I see-saw mechanism. We have shown, besides explaining the neutrino mass, it can also accommodate a non-thermal sterile neutrino DM with correct relic density. In contrast with the existing literature, we have found that $W^{\pm }$ decay can also be a dominant production mode of the sterile neutrino DM. To obtain the comoving number density of dark matter, we have solved here a coupled set of Boltzmann equations considering all possible decay as well as annihilation production modes of the sterile neutrino dark matter. The framework developed here though has been done for a U(1)${}_{\mathrm{B}-\mathrm{L}}$ model, can be applied quite generally for any models with an extra neutral gauge boson and a fermionic non-thermal dark matter.

   hep-phJCAP(2016)·81 citations
9. 09*

   Axial form factor of the nucleon at large momentum transfers

   I.V. Anikin🇷🇺 · V.M. Braun🇩🇪 · N. Offen🇩🇪

   Motivated by the emerging possibilities to study threshold pion electroproduction at large momentum transfers at Jefferson Laboratory following the 12 GeV upgrade, we provide a short theory summary and an estimate of the nucleon axial form factor for large virtualities in the $Q^2=1-10{\text{GeV}}^2$ range using next-to-leading order light-cone sum rules.

   hep-phnucl-exnucl-thPRD(2016)·27 citations
10. 10*

    Transverse momentum dependent splitting functions at work: quark-to-gluon splitting

    M. Hentschinski🇲🇽 · A. Kusina🇫🇷 · K. Kutak🇵🇱

    Using the recently obtained Pgq splitting function we extend the low x evolution equation for gluons to account for contributions originating from quark-to-gluon splitting. In order to write down a consistent equation we resum virtual corrections coming from the gluon channel and demonstrate that this implies a suitable regularization of the Pgq singularity, corresponding to a soft emitted quark. We also note that the obtained equation is in a straightforward manner generalized to a nonlinear evolution equation which takes into account effects due to the presence of high gluon densities.

    hep-phPRD(2016)·31 citations
11. 11*

    Holographically emulating sequential versus instantaneous disappearance of vector mesons in a hot environment

    Rico Zöllner🇩🇪 · Burkhard Kampfer🇩🇪

    Descent extensions of the soft-wall model are used to accommodate two variants of Regge trajectories of vector meson excitations. At non-zero temperatures, various options for either sequential or instantaneous disappearance of vector mesons as normalisable modes are found, thus emulating deconfinement at a certain temperature in the order of the (pseudo-) critical temperature of QCD. The crucial role of the blackness function, which steers the thermodynamic properties of the considered system, is highlighted.

    hep-phhep-thPRC(2016)·10 citations
12. 12*

    NLO QCD corrections to off-shell ttj production at the LHC

    Malgorzata Worek🇩🇪

    A short summary of results for top-quark pair production in association with a jet with NLO QCD off-shell effects at the LHC is given. The calculation is based on the matrix element for the $pp\to e^{+}{\nu }_e{\mu }^{-}{\bar{\nu }}_{\mu }b\bar{b}j$ process. All quantum effects are properly accounted for, which amounts to including all Feynman diagrams that result in this final state with interference effects as well as non-zero top-quark width effects. Results for total cross sections and a few differential distributions at the LHC Run1 energy of $\sqrt{s}=8$ TeV are presented. In addition, the size of top-quark off-shell effects is quantified for the total cross section in presence of rather inclusive cuts on all final states. Numerical results shown in this proceedings have been obtained with the HELAC-NLO Monte Carlo program.

    hep-phPoS(2016)·1 citation
13. 13*

    Photon propagation in slowly varying electromagnetic fields

    Felix Karbstein🇩🇪

    We study the effective theory of soft photons in slowly varying electromagnetic background fields at one-loop order in QED. This is of relevance for the study of all-optical signatures of quantum vacuum nonlinearity in realistic electromagnetic background fields as provided by high-intensity lasers. The central result derived in this article is a new analytical expression for the photon polarization tensor in two linearly polarized counter-propagating pulsed Gaussian laser beams. As we treat the peak field strengths of both laser beams as free parameters this field configuration can be considered as interpolating between the limiting cases of a purely right- or left-moving laser beam (if one of the peak field strengths is set to zero) and the standing-wave type scenario with two counter-propagating beams of equal strength.

    hep-phRuss.Phys.J.(2017)·2 citations
14. 14*

    The kite integral to all orders in terms of elliptic polylogarithms

    Luise Adams🇩🇪 · Christian Bogner🇩🇪 · Armin Schweitzer🇩🇪 · Stefan Weinzierl🇩🇪

    We show that the Laurent series of the two-loop kite integral in $D=4-2\epsilon$ space-time dimensions can be expressed in each order of the series expansion in terms of elliptic generalisations of (multiple) polylogarithms. Using differential equations we present an iterative method to compute any desired order. As an example, we give the first three orders explicitly.

    hep-phhep-thmath-phmath.MPJ.Math.Phys.(2016)·161 citations
15. 15*

    A covariant nonlocal Lagrangian for the description of the scalar kaonic sector

    Milena Soltysiak🇵🇱 · Francesco Giacosa🇩🇪

    Mesons are extended objects, hence their interaction can be described by utilizing form factors. At the Lagrangian level, one can use nonlocal interaction terms. Here we describe two possible nonlocal Lagrangians leading to a 3D form factor: the first one is simple but does not fulfill covariance (if one insists on a 3D cutoff), the second extension is more involved but guarantees covariance. Such form factors are useful when calculating mesonic loops. As an important example, we discuss the scalar kaonic sector, $I(J^P)=\frac{1}{2}(0^{+})$. The Lagrangian contains a single scalar kaon (the well-establish state $K_0^{\ast }(1430)$), but through loops $K_0^{\ast }(800)$ emerges as a dynamically generated companion pole (which disappears in the large-$N_c$ limit).

    hep-phActa Phys.Polon.Supp.(2016)·11 citations
16. 16*

    Twist-3 T-odd fragmentation functions $G^{\perp }$ and ${\tilde{G}}^{\perp }$ in a spectator model

    Yongliang Yang🇨🇳 · Zhun Lu🇨🇳 · Ivan Schmidt🇨🇱

    We present a calculation of the twist-3 T-odd chiral-even fragmentation functions $G^{\perp }$ and ${\tilde{G}}^{\perp }$ using a spectator model. We consider the effect gluon exchange to calculate all necessary one-loop diagrams for the quark-quark and quark-gluon-quark correlation functions. We find that the gluon loops corrections generate non-zero contribution to these two fragmentation function. We numerically calculate their half-$k_T$ moments by integrating over the transverse momentum and also verify the equation of motion relation among $G^{\perp }$, ${\tilde{G}}^{\perp }$ and the Collins function.

    hep-phPLB(2016)·22 citations
17. 17*

    Dynamical scheme for hadronization with first-order phase transition

    Bohao Feng🇨🇳 · Zhe Xu🇨🇳 · Carsten Greiner🇩🇪

    We present a dynamical scheme for hadronization with first-order confinement phase transition. The thermodynamical conditions of phase equilibrium, the fluid velocity profile, and the dissipative effect determine the macroscopic changes of the parton volume and the corresponding hadron volume during the phase transition. The macroscopic volume changes are the basis for building up a dynamical scheme by considering microscopic transition processes from partons to hadrons and backwards. The established scheme is proved by comparing the numerical results with the analytical solutions in the case of a one-dimensional expansion of a dissipative fluid with Bjorken boost invariance. The comparisons show almost perfect agreements, which demonstrate the applicability of the introduced scheme.

    hep-phnucl-thPRC(2017)·6 citations
18. 18*

    Gluon and Wilson loop TMDs for hadrons of spin $\le$ 1

    Daniël Boer🇳🇱 · Sabrina Cotogno🇳🇱 · Tom van Daal🇳🇱 · Piet J. Mulders🇳🇱 · Andrea Signori🇳🇱 · Ya-Jin Zhou🇨🇳

    In this paper we consider the parametrizations of gluon transverse momentum dependent (TMD) correlators in terms of TMD parton distribution functions (PDFs). These functions, referred to as TMDs, are defined as the Fourier transforms of hadronic matrix elements of nonlocal combinations of gluon fields. The nonlocality is bridged by gauge links, which have characteristic paths (future or past pointing), giving rise to a process dependence that breaks universality. For gluons, the specific correlator with one future and one past pointing gauge link is, in the limit of small $x$, related to a correlator of a single Wilson loop. We present the parametrization of Wilson loop correlators in terms of Wilson loop TMDs and discuss the relation between these functions and the small-$x$ `dipole' gluon TMDs. This analysis shows which gluon TMDs are leading or suppressed in the small-$x$ limit. We discuss hadronic targets that are unpolarized, vector polarized (relevant for spin-$1/2$ and spin-$1$ hadrons), and tensor polarized (relevant for spin-$1$ hadrons). The latter are of interest for studies with a future Electron-Ion Collider with polarized deuterons.

    hep-phJHEP(2016)·117 citations
19. 19*

    Fundamental partial compositeness

    Francesco Sannino🇩🇰 · Alessandro Strumia🇨🇭 · Andrea Tesi🇺🇸 · Elena Vigiani🇮🇹

    We construct renormalizable Standard Model extensions, valid up to the Planck scale, that give a composite Higgs from a new fundamental strong force acting on fermions and scalars. Yukawa interactions of these particles with Standard Model fermions realize the partial compositeness scenario. Under certain assumptions on the dynamics of the scalars, successful models exist because gauge quantum numbers of Standard Model fermions admit a minimal enough 'square root'. Furthermore, right-handed SM fermions have an SU(2)${}_R$-like structure, yielding a custodially-protected composite Higgs. Baryon and lepton numbers arise accidentally. Standard Model fermions acquire mass at tree level, while the Higgs potential and flavor violations are generated by quantum corrections. We further discuss accidental symmetries and other dynamical features stemming from the new strongly interacting scalars. If the same phenomenology can be obtained from models without our elementary scalars, they would reappear as composite states.

    hep-phhep-latJHEP(2016)·77 citations
20. 20*

    The Banks-Zaks expansion in perturbative QCD: an update

    P. M. Stevenson🇺🇸

    The recent QCD calculations of the five-loop beta function and of R(e+e-) to O(alpha_s^4) provide one more term in the Banks-Zaks expansion in (16.5-nf). There is no longer any hope that the expansion could extend, even crudely, to low nf. Above nf=9, however, the results appear to be reasonably consistent from order to order.

    hep-phMod.Phys.Lett.A(2016)·8 citations
21. 21*

    QCD phase transitions via a refined truncation of Dyson-Schwinger equations

    Fei Gao🇨🇳 · Yu-xin Liu🇨🇳

    We investigate both the chiral and deconfinement phase transitions of QCD matter in a refined scheme of Dyson-Schwinger equations, which have been shown to be successful in giving the meson mass spectrum and matching the interaction with the results from ab initio computation. We verify the equivalence of the chiral susceptibility criterion with different definitions for the susceptibility and confirm that the chiral susceptibility criterion is efficient to fix not only the chiral phase boundary but also the critical end point (CEP), especially when one could not have the effective thermodynamical potential. We propose a generalized Schwinger function criterion for the confinement. We give the phase diagram of both phase transitions and show that in the refined scheme the position of the CEP shifts to lower chemical potential and higher temperature. Based on our calculation and previous results of the chemical freeze out conditions, we propose that the CEP locates in the states of the matter generated by the Au--Au collisions with $\sqrt{s_{NN}^{}}=9\sim 15$ GeV.

    hep-phPRD(2016)·95 citations
22. 22*

    Quark-hadron duality: pinched kernel approch

    C. A. Dominguez🇿🇦 · L. A. Hernandez🇿🇦 · K. Schilcher🇿🇦 · H. Spiesberger🇩🇪

    Hadronic spectral functions measured by the ALEPH collaboration in the vector and axial-vector channels are used to study potential quark-hadron duality violations (DV). This is done entirely in the framework of pinched kernel finite energy sum rules (FESR), i.e. in a model independent fashion. The kinematical range of the ALEPH data is effectively extended up to $s=10\text{mbox}{GeV}^2$ by using an appropriate kernel, and assuming that in this region the spectral functions are given by perturbative QCD. Support for this assumption is obtained by using $e^{+}{e}^{-}$ annihilation data in the vector channel. Results in both channels show a good saturation of the pinched FESR, without further need of explicit models of DV.

    hep-phhep-exhep-lathep-thMod.Phys.Lett.A(2016)·1 citation
23. 23*

    Revealing proton shape fluctuations with incoherent diffraction at high energy

    Heikki Mäntysaari🇺🇸 · Björn Schenke🇺🇸

    The differential cross section of exclusive diffractive vector meson production in electron proton collisions carries important information on the geometric structure of the proton. More specifically, the coherent cross section as a function of the transferred transverse momentum is sensitive to the size of the proton, while the incoherent, or proton dissociative cross section is sensitive to fluctuations of the gluon distribution in coordinate space. We show that at high energies the experimentally measured coherent and incoherent cross sections for the production of $J/\Psi$ mesons are very well reproduced within the color glass condensate framework when strong geometric fluctuations of the gluon distribution in the proton are included. For $\rho$ meson production we also find reasonable agreement. We study in detail the dependence of our results on various model parameters, including the average proton shape, analyze the effect of saturation scale and color charge fluctuations and constrain the degree of geometric fluctuations.

    hep-phnucl-thPRD(2016)·161 citations
24. 24*

    Momentum correlations of scattered particles in quantum field theory: one-loop entanglement generation

    Ricardo Faleiro🇵🇹 · Rafael Pavão🇪🇸 · Helder Alexander · Brigitte Hiller🇵🇹 · Alex Blin🇵🇹 · Marcos Sampaio🇧🇷

    We compute the entanglement entropy variation between initial (separable or entangled in the momenta) and final states $\Delta S_E$ in an elastic scattering of a bipartite system composed by two interacting scalar particles. We perform a quantum field theoretical calculation to one loop order and verify that $\Delta S_E$ changes as we vary the energy of incoming particles and the coupling strength in a non-trivial way.

    hep-phquant-phJ.Phys.A(2020)·19 citations
25. 25*

    Non-local probes for a relaxing non-Abelian plasma

    Loredana Bellantuono🇮🇹

    The thermalization of a strongly coupled plasma is examined in the holographic framework through non-local observables: the equal-time two-point correlation function of a large dimension boundary operator, and Wilson loops of different shapes. The evolution of the probes from an initial far-from-equilibrium state to a hydrodynamic regime is found to depend on their size. A hierarchy among the thermalization times of the energy density, the pressures and the large size probes, is identified: the relaxation process is faster at short distances.

    hep-phNuovo Cim.C(2017)·0 citations
26. 26*

    Angular dependence of primordial trispectra and CMB spectral distortions

    Maresuke Shiraishi🇯🇵 · Nicola Bartolo🇮🇹 · Michele Liguori🇮🇹

    Under the presence of anisotropic sources in the inflationary era, the trispectrum of the primordial curvature perturbation has a very specific angular dependence between each wavevector that is distinguishable from the one encountered when only scalar fields are present, characterized by an angular dependence described by Legendre polynomials. We examine the imprints left by curvature trispectra on the $TT\mu$ bispectrum, generated by the correlation between temperature anisotropies (T) and chemical potential spectral distortions ($\mu$) of the Cosmic Microwave Background (CMB). Due to the angular dependence of the primordial signal, the corresponding $TT\mu$ bispectrum strongly differs in shape from $TT\mu$ sourced by the usual $g_{\mathrm{NL}}$ or ${\tau }_{\mathrm{NL}}$ local trispectra, enabling us to obtain an unbiased estimation. From a Fisher matrix analysis, we find that, in a cosmic-variance-limited (CVL) survey of $TT\mu$, a minimum detectable value of the quadrupolar Legendre coefficient is $d_2\sim 0.01$, which is 4 orders of magnitude better than the best value attainable from the $TTTT$ CMB trispectrum. In the case of an anisotropic inflationary model with a $f(\varphi )F^2$ interaction (coupling the inflaton field $\varphi$ with a vector kinetic term $F^2$), the size of the curvature trispectrum is related to that of quadrupolar power spectrum asymmetry, $g_{\ast }$. In this case, a CVL measurement of $TT\mu$ makes it possible to measure $g_{\ast }$ down to $10^{-3}$.

    ↳ astro-ph.COgr-qchep-phJCAP(2016)·23 citations
27. 27*

    ${\alpha }^{\prime }$ Inflation: Moduli Stabilisation and Observable Tensors from Higher Derivatives

    Michele Cicoli🇮🇹 · David Ciupke🇩🇪 · Senarath de Alwis🇺🇸 · Francesco Muia🇮🇹

    The leading order dynamics of the type IIB Large Volume Scenario is characterised by the interplay between ${\alpha }^{\prime }$ and non-perturbative effects which fix the overall volume and all local blow-up modes leaving (in general) several flat directions. In this paper we show that, in an arbitrary Calabi-Yau with at least one blow-up mode resolving a point-like singularity, any remaining flat directions can be lifted at subleading order by the inclusions of higher derivative ${\alpha }^{\prime }$ corrections. We then focus on simple fibred cases with one remaining flat direction which can behave as an inflaton if its potential is generated by both higher derivative ${\alpha }^{\prime }$ and winding loop corrections. Natural values of the underlying parameters give a spectral index in agreement with observational data and a tensor-to-scalar ratio of order $r=0.01$ which could be observed by forthcoming CMB experiments. Dangerous corrections from higher dimensional operators are suppressed due to the presence of an approximate non-compact shift symmetry.

    ↳ hep-thastro-ph.COhep-phJHEP(2016)·79 citations
28. 28*

    Direct virtual photon production in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV

    STAR Collaboration

    We report the direct virtual photon invariant yields in the transverse momentum ranges $1<p_T<3$ GeV/$c$ and $5<p_T<10$ GeV/$c$ at mid-rapidity derived from the dielectron invariant mass continuum region $0.10<M_{ee}<0.28$ GeV/$c^2$ for 0-80\% minimum-bias Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV. A clear excess in the invariant yield compared to the number-of-binary-collisions ($N_{bin}$) scaled $p+p$ reference is observed in the $p_T$ range $1<p_T<3$ GeV/$c$. For $p_T>6$ GeV/$c$ the production follows $N_{bin}$ scaling. Model calculations with contributions from thermal radiation and initial hard parton scattering are consistent within uncertainties with the direct virtual photon invariant yield.

    ↳ nucl-exhep-exhep-phnucl-thPLB(2017)·96 citations
29. 29*

    Charge redistribution from anomalous magnetovorticity coupling

    Koichi Hattori🇨🇳 · Yi Yin🇺🇸

    We investigate novel transport phenomena in a chiral fluid originated from an interplay between a vorticity and strong magnetic field, which induces a redistribution of vector charges in the system and an axial current along the magnetic field. The corresponding transport coefficients are obtained from an energy-shift argument for the chiral fermions in the lowest Landau level (LLL) due to a spin-vorticity coupling and also from diagrammatic computations on the basis of the linear response theory. Based on consistent results from the both methods, we observe that the transport coefficients are proportional to the anomaly coefficient and are independent of temperature and chemical potential. We therefore speculate that these transport phenomena are connected to quantum anomaly.

    ↳ hep-thcond-mat.mes-hallhep-phnucl-thPRL(2016)·49 citations
30. 30*

    Constraining High-Energy Cosmic Neutrino Sources: Implications and Prospects

    Kohta Murase🇺🇸 · Eli Waxman🇮🇱

    We consider limits on the local ($z=0$) density ($n_0$) of extragalactic neutrino sources set by the nondetection of steady high-energy neutrino sources producing $\gtrsim 50$ TeV muon multiplets in the present IceCube data, taking into account the redshift evolution, luminosity function and neutrino spectrum of the sources. We show that the lower limit depends moderately on source spectra and strongly on redshift evolution. We find $n_0\gtrsim {10}^{-8}-{10}^{-7}{\mathrm{Mpc}}^{-3}$ for standard candle sources evolving rapidly, $n_s\propto {(1+z)}^3$, and $n_0\gtrsim {10}^{-6}-{10}^{-5}{\mathrm{Mpc}}^{-3}$ for nonevolving sources. The corresponding upper limits on their neutrino luminosity are $L_{{\nu }_{\mu }}^{\mathrm{eff}}\lesssim 10^{42}-10^{43}\mathrm{erg}{\mathrm{s}}^{-1}$ and $L_{{\nu }_{\mu }}^{\mathrm{eff}}\lesssim 10^{41}-10^{42}\mathrm{erg}{\mathrm{s}}^{-1}$, respectively. Applying these results to a wide range of classes of potential sources, we show that powerful blazar jets associated with active galactic nuclei are unlikely to be the dominant sources. For almost all other steady candidate source classes (including starbursts, radio galaxies, and galaxy clusters and groups), an order of magnitude increase in the detector sensitivity at $\sim 0.1-1$ PeV will enable a detection (as point sources) of the few brightest objects. Such an increase, which may be provided by next-generation detectors like IceCube-Gen2 and an upgraded KM3NET, can improve the limit on $n_0$ by more than two orders of magnitude. Future gamma-ray observations (by Fermi, HAWC and CTA) will play a key role in confirming the association of the neutrinos with their sources.

    ↳ astro-ph.HEastro-ph.COhep-phPRD(2016)·266 citations
31. 31*

    Current and future constraints on Bekenstein-type models for varying couplings

    A. C. O. Leite🇵🇹 · C. J. A. P. Martins🇵🇹

    Astrophysical tests of the stability of dimensionless fundamental couplings, such as the fine-structure constant $\alpha$ and the proton-to-electron mass ratio $\mu$, are an optimal probe of new physics. There is a growing interest in these tests, following indications of possible spacetime variations at the few parts per million level. Here we make use of the latest astrophysical measurements, combined with background cosmological observations, to obtain improved constraints on Bekenstein-type models for the evolution of both couplings. These are arguably the simplest models allowing for $\alpha$ and $\mu$ variations, and are characterized by a single free dimensionless parameter, $\zeta$, describing the coupling of the underlying dynamical degree of freedom to the electromagnetic sector. In the former case we find that this parameter is constrained to be $|{\zeta }_{\alpha }|<4.8\times 10^{-6}$ (improving previous constraints by a factor of 6), while in the latter (which we quantitatively compare to astrophysical measurements for the first time) we find ${\zeta }_{\mu }=(2.7\pm 3.1)\times 10^{-7}$; both of these are at the $99.7\%$ confidence level. For ${\zeta }_{\alpha }$ this constraint is about 20 times stronger than the one obtained from local Weak Equivalence Principle tests, while for ${\zeta }_{\mu }$ it is about 2 orders of magnitude weaker. We also discuss the improvements on these constraints to be expected from the forthcoming ESPRESSO and ELT-HIRES spectrographs, conservatively finding a factor around 5 for the former and around 50 for the latter.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2016)·14 citations
32. 32*

    Studying photon structure at an EIC

    Xiaoxuan Chu🇨🇳 · Elke-Caroline Aschenauer🇺🇸 · Jeong-Hun Lee🇺🇸

    A future Electron-Ion Collider (EIC) will deliver luminosities of $10^{33}-10^{34}$ cm${}^{-2}$s${}^{-1}$ for collisions of polarized electrons and protons and heavy ions over a wide range of center-of-mass energies (40 $\mathrm{GeV}$ to 145 $\mathrm{GeV}$). One of its promising physics programs is to study the partonic structure of quasi-real photons. Measuring di-jet in photoproduction events, one can effectively access the underlying parton dynamics of the photons through the selection of the resolved photon processes. In this paper, we discuss the feasibility of tagging resolved photon processes and measuring the di-jet cross section as a function of jet transverse momentum in ranges of $x_{\gamma }^{rec}$ at an EIC. These studies show that parton distributions in the photon can be extracted at an EIC.

    ↳ nucl-exhep-phPoS(2016)·1 citation

* 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.