Wed·Jul 19, 2017Wednesday·July 19, 2017

1. 01*

   Thermal excitation spectrum from entanglement in an expanding quantum string

   Jürgen Berges🇩🇪 · Stefan Floerchinger🇩🇪 · Raju Venugopalan🇺🇸

   A surprising result in $e^{+}{e}^{-}$ collisions is that the particle spectra from the string formed between the expanding quark-antiquark pair have thermal properties even though scatterings appear not to be frequent enough to explain this. We address this problem by considering the finite observable interval of a relativistic quantum string in terms of its reduced density operator by tracing over the complement region. We show how quantum entanglement in the presence of a horizon in spacetime for the causal transfer of information leads locally to a reduced mixed-state density operator. For very early proper time $\tau$, we show that the entanglement entropy becomes extensive and scales with the rapidity. At these early times, the reduced density operator is of thermal form, with an entanglement temperature $T_{\tau }=\hslash /(2\pi k_B\tau )$, even in the absence of any scatterings.

   hep-phhep-thnucl-thPLB(2018)·75 citations
2. 02*

   Impact of the heavy quark matching scales in PDF fits

   The xFitter Developers Team: V. Bertone🇳🇱 · D. Britzger🇩🇪 · S. Camarda🇨🇭 · A. Cooper-Sarkar🇬🇧 · A. Geiser🇩🇪 · F. Giuli🇬🇧 · A. Glazov🇩🇪 · E. Godat🇺🇸 · A. Kusina🇫🇷 · A. Luszczak🇵🇱 · F. Lyonnet🇺🇸 · F. Olness🇺🇸 and 4 other authors

   We investigate the impact of displaced heavy quark matching scales in a global fit. The heavy quark matching scale ${\mu }_m$ determines at which energy scale $\mu$ the QCD theory transitions from $N_F$ to $N_F+1$ in the Variable Flavor Number Scheme (VFNS) for the evolution of the Parton Distribution Functions (PDFs) and strong coupling ${\alpha }_S(\mu )$. We study the variation of the matching scales, and their impact on a global PDF fit of the combined HERA data. As the choice of the matching scale ${\mu }_m$ effectively is a choice of scheme, this represents a theoretical uncertainty; ideally, we would like to see minimal dependence on this parameter. For the transition across the charm quark (from $N_F=3$ to $4$), we find a large ${\mu }_m={\mu }_c$ dependence of the global fit ${\chi }^2$ at NLO, but this is significantly reduced at NNLO. For the transition across the bottom quark (from $N_F=4$ to $5$), we have a reduced ${\mu }_m={\mu }_b$ dependence of the ${\chi }^2$ at both NLO and NNLO as compared to the charm. This feature is now implemented in xFitter 2.0.0, an open source QCD fit framework.

   hep-phEPJC(2017)·20 citations
3. 03*

   DUNE sensitivities to the mixing between sterile and tau neutrinos

   Pilar Coloma🇺🇸 · David V. Forero🇧🇷 · Stephen J. Parke🇺🇸

   Light sterile neutrinos can be probed in a number of ways, including electroweak decays, cosmology and neutrino oscillation experiments. At long-baseline experiments, the neutral-current data is directly sensitive to the presence of light sterile neutrinos: once the active neutrinos have oscillated into a sterile state, a depletion in the neutral-current data sample is expected since they do not interact with the $Z$ boson. This channel offers a direct avenue to probe the mixing between a sterile neutrino and the tau neutrino, which remains largely unconstrained by current data. In this work, we study the potential of the DUNE experiment to constrain the mixing angle which parametrizes this mixing, ${\theta }_{34}$, through the observation of neutral-current events at the far detector. We find that DUNE will be able to improve significantly over current constraints thanks to its large statistics and excellent discrimination between neutral- and charged-current events.

   hep-phhep-exJHEP(2018)·53 citations
4. 04*

   Dark Matter as a weakly coupled Dark Baryon

   Andrea Mitridate🇮🇹 · Michele Redi🇮🇹 · Juri Smirnov🇮🇹 · Alessandro Strumia🇨🇭

   Dark Matter might be an accidentally stable baryon of a new confining gauge interaction. We extend previous studies exploring the possibility that the DM is made of dark quarks heavier than the dark confinement scale. The resulting phenomenology contains new unusual elements: a two-stage DM cosmology (freeze-out followed by dark condensation), a large DM annihilation cross section through recombination of dark quarks (allowing to fit the positron excess). Light dark glue-balls are relatively long lived and give extra cosmological effects; DM itself can remain radioactive.

   hep-phastro-ph.COJHEP(2017)·114 citations
5. 05*

   Tachyonic instability of the scalar mode prior to QCD critical point based on Functional renormalization-group method

   Takeru Yokota🇯🇵 · Teiji Kunihiro🇯🇵 · Kenji Morita🇯🇵

   We establish and elucidate the physical meaning of the appearance of an acausal mode in the sigma mesonic channel, found in the previous work by the present authors, when the system approaches the ${\mathrm{Z}}_2$ critical point. The functional renormalization group method is applied to the two--flavor quark--meson model with varying current quark mass $m_q$ even away from the physical value at which the pion mass is reproduced. We first determine the whole phase structure in the three-dimensional space $(T,\mu ,m_q)$ consisting of temperature $T$, quark chemical potential $\mu$ and $m_q$, with the tricritical point, $\mathrm{O}(4)$ and ${\mathrm{Z}}_2$ critical lines being located; they altogether make a wing-like shape quite reminiscent of those known in the condensed matters with a tricritical point. We then calculate the spectral functions ${\rho }_{\sigma ,\pi }(\omega ,p)$ in the scalar and pseudoscalar channel around the critical points. We find that the sigma mesonic mode becomes tachyonic with a superluminal velocity at finite momenta before the system reaches the ${\mathrm{Z}}_2$ point from the lower density, even for $m_q$ smaller than the physical value. One of the possible implications of the appearance of such a tachyonic mode at finite momenta is that the assumed equilibrium state with a uniform chiral condensate is unstable toward a state with an inhomogeneous $\sigma$ condensate. No such an anomalous behavior is found in the pseudoscalar channel. We find that the $\sigma$-to-$2\sigma$ coupling due to finite $m_q$ play an essential role for the drastic modification of the spectral function.

   hep-phnucl-thPRD(2017)·26 citations
6. 06*

   Discrimination of anisotropy in dark matter velocity distribution with directional detectors

   Keiko I. Nagao🇯🇵 · Tomonori Ikeda🇯🇵 · Ryota Yakabe🇯🇵 · Tatsuhiro Naka🇯🇵 · Kentaro Miuchi🇯🇵

   Directional detection of dark matter has sensitivity for both recoil energy and direction of nuclear recoil. It opens the way to measure local velocity distribution of dark matter. In this paper, we study possibility to discriminate isotropic distribution and anisotropic one suggested by a N-body simulation with directional detector. Numerical simulation is performed for two cases according to the detectors, one corresponds to angular histogram and the other is energy-angular distribution of the signals. We reveal that the anisotropy of velocity distribution can be discriminated at 90% C.L. with chi-squared test if O($10^4$) signals are obtained.

   hep-phastro-ph.COhep-exPhys.Dark Univ.(2020)·10 citations
7. 07*

   Neutrino mu-tau reflection symmetry and its breaking in the minimal seesaw

   Zhi-Cheng Liu🇨🇳 · Chong-Xing Yue🇨🇳 · Zhen-hua Zhao🇨🇳

   In this paper, we attempt to implement the neutrino $\mu$-$\tau$ reflection symmetry (which predicts ${\theta }_{23}^{}=\pi /4$ and $\delta =\pm \pi /2$ as well as trivial Majorana phases) in the minimal seesaw (which enables us to fix the neutrino masses). For some direct (the preliminary experimental hints towards ${\theta }_{23}^{}\ne \pi /4$ and $\delta \ne -\pi /2$) and indirect (inclusion of the renormalization group equation effect and implementation of the leptogenesis mechanism) reasons, we particularly study the breakings of this symmetry and their phenomenological consequences.

   hep-phJHEP(2017)·41 citations
8. 08*

   How to simulate global cosmic strings with large string tension

   Vincent B. Klaer🇩🇪 · Guy D. Moore🇩🇪

   Global string networks may be relevant in axion production in the early Universe, as well as other cosmological scenarios. Such networks contain a large hierarchy of scales between the string core scale and the Hubble scale, log(f/H) around 70, which influences the network dynamics by giving the strings large tensions T = pi f^2 log(f/H). We present a new numerical approach to simulate such global string networks, capturing the tension without an exponentially large lattice.

   hep-phastro-ph.COhep-latJCAP(2017)·105 citations
9. 09*

   Symmetric cumulants as a probe of the proton substructure at LHC energies

   Javier L. Albacete🇪🇸 · Hannah Petersen🇩🇪 · Alba Soto-Ontoso🇪🇸

   We present a systematic study of the normalized symmetric cumulants, NSC(n,m), at the eccentricity level in proton-proton interactions at $\sqrt{s}=13$ TeV within a wounded hot spot approach. We focus our attention on the influence of spatial correlations between the proton constituents, in our case gluonic hot spots, on this observable. We notice that the presence of short-range repulsive correlations between the hot spots systematically decreases the values of NSC(2,3) and NSC(2,4) in mid-to-ultra central collisions while increases them in peripheral interactions. In the case of NSC(2,3) we find that, as suggested by data, an anti-correlation of ${\epsilon }_2$ and ${\epsilon }_3$ in ultra-central collisions, i.e. NSC(2,3)$<0$, is possible within the correlated scenario while it never occurs without correlations. We attribute this fact to the decisive role of correlations on enlarging the probability of interaction topologies that reduce the value of NSC(2,3) and, eventually, make it negative. Further, we explore the dependence of our conclusions on the values of the hot spot radius and the repulsive core distance. Our results add evidence to the idea that considering spatial correlations between the subnucleonic degrees of freedom of the proton may have a strong impact on the initial state properties of proton-proton interactions [1].

   hep-phhep-exnucl-thPLB(2018)·35 citations
10. 10*

    The paradox of the Standard Model

    Riccardo Barbieri🇮🇹

    As a way to recall and honour Guido Altarelli I contribute to the discussion on the prospect for the future of Particle Physics. I do this because I am sure that Guido would have liked the discussion, even though I am not equally sure that he would have agreed on all the opinions I express here.

    hep-ph3 citations
11. 11*

    Ultra slow-roll inflation demystified

    Konstantinos Dimopoulos🇬🇧

    Ultra-slow-roll (USR) inflation is a new mode of inflation which corresponds to the occasions when the inflaton field must traverse an extremely flat part of the scalar potential, when the usual slow-roll (SR) fails. We investigate USR and obtain an estimate for how long it lasts, given the initial kinetic density of the inflaton. We also find that, if the initial kinetic density is small enough, USR can be avoided and the usual SR treatment is valid. This has important implications for inflection-point inflation.

    hep-phastro-ph.COhep-thPLB(2017)·183 citations
12. 12*

    Regge trajectories of Excited Baryons, quark-diquark models and quark-hadron duality

    Pere Masjuan🇪🇸 · Enrique Ruiz Arriola🇪🇸

    The parton model relations in conjunction with quark-hadron duality in deep inelastic scattering suggests an asymptotic dominance of quark-diquark type of baryonic excited states with a radial Regge uniformly distributed mass squared spectrum $M_n^2={\mu }^{2}n+M_0^2$. We argue that this points to a lineary quark-diquark confining potential. We analyze the radial ($n$) and angular-momentum ($J$) Regge trajectories for all light-quark states with baryon number one listed in the 2016 edition of the Particle Data Tables. The parameters of the mass squared trajectories are obtained by linear regression assuming $\Delta M_n^2\sim M_n{\Gamma }_n$ weighted with the width ${\Gamma }_n$ of the resonance and the error analysis is carried out accordingly.

    hep-phPRD(2017)·12 citations
13. 13*

    Properties of open and hidden charm mesons in light quark matter

    Martin Cleven🇪🇸 · Volodymyr K. Magas🇪🇸 · Angels Ramos🇪🇸

    In this work we study the implications of light-quark pionic matter at finite temperatures on the properties of open and hidden charm mesons. The meson-meson interactions are described by means of a chiral unitary approach accounting for coupled channels effects. The in-medium Lippmann-Schwinger Equations, which consider the change in self-energy that the mesons acquire from interacting with the surrounding pionic matter, are solved self-consistently, and the spectral functions of the mesons in the hot pion bath are obtained. It is observed that the charmed mesons develop a quite substantial pion-induced width, being of several tens at a temperature of 150 MeV. The $J/\Psi$ meson stays narrow, but its pionic width at 150 MeV, found to be around 0.1 MeV, is already larger that its vacuum width.

    hep-phPRC(2017)·24 citations
14. 14*

    Next-to-next-to-leading-order QCD corrections to hadronic width of pseudoscalar quarkonium

    Feng Feng🇨🇳 · Yu Jia🇨🇳 · Wen-Long Sang🇨🇳

    We compute the next-to-next-to-leading order (NNLO) QCD corrections to the hadronic decay rates of the pseudoscalar quarkonia, at the lowest order in velocity expansion. The validity of NRQCD factorization for inclusive quarkonium decay process, for the first time, is verified to relative order ${\alpha }_s^2$. As a byproduct, the renormalization group equation (RGE) of the leading NRQCD 4-fermion operator ${\mathcal{O}}_1({}^1{S}_0)$ is also deduced to this perturbative order. By incorporating this new piece of correction together with available relativistic corrections, we find that there exists severe tension between the state-of-the-art NRQCD predictions and the measured ${\eta }_c$ hadronic width, and in particular the branching fraction of ${\eta }_c\to \gamma \gamma$. NRQCD appears to be capable of accounting for ${\eta }_b$ hadronic decay to a satisfactory degree, and our most refined prediction is $\mathrm{Br}({\eta }_b\to \gamma \gamma )=(4.8\pm 0.7)\times 10^{-5}$.

    hep-phhep-exPRL(2017)·47 citations
15. 15*

    Digging Deeper for New Physics in the LHC Data

    Pouya Asadi🇺🇸 · Matthew R. Buckley🇺🇸 · Anthony DiFranzo🇺🇸 · Angelo Monteux🇺🇸 · David Shih🇺🇸

    In this paper we describe a novel, model-independent technique of "rectangular aggregations" for mining the LHC data for hints of new physics. A typical (CMS) search now has hundreds of signal regions, which can obscure potentially interesting anomalies. Applying our technique to the two CMS jets+MET SUSY searches, we identify a set of previously overlooked $\sim 3\sigma$ excesses. Among these, four excesses survive tests of inter- and intra-search compatibility, and two are especially interesting: they are largely overlapping between the jets+MET searches and are characterized by low jet multiplicity, zero $b$-jets, and low MET and $H_T$. We find that resonant color-triplet production decaying to a quark plus an invisible particle provides an excellent fit to these two excesses and all other data -- including the ATLAS jets+MET search, which actually sees a correlated excess. We discuss the additional constraints coming from dijet resonance searches, monojet searches and pair production. Based on these results, we believe the wide-spread view that the LHC data contains no interesting excesses is greatly exaggerated.

    hep-phhep-exJHEP(2017)·26 citations
16. 16*

    Very Special Conformal Field Theories (VSCFT) and their holographic duals

    Yu Nakayama🇯🇵

    Cohen and Glashow introduced the notion of very special relativity as viable space-time symmetry of elementary particle physics. As a natural generalization of their idea, we study the subgroup of the conformal group, dubbed very special conformal symmetry, which is an extension of the very special relativity. We classify all of them and construct field theory examples as well as holographic realization of the very special conformal field theories.

    ↳ hep-thhep-phPRD(2018)·7 citations
17. 17*

    Effects of non-equilibrated topological charge distributions on pseudoscalar meson masses and decay constants

    C. Bernard🇺🇸 · D. Toussaint (the MILC Collaboration)🇺🇸

    We study the effects of failure to equilibrate the squared topological charge $Q^2$ on lattice calculations of pseudoscalar masses and decay constants. The analysis is based on chiral perturbation theory calculations of the dependence of these quantities on the QCD vacuum angle $\theta$. For the light-light partially quenched case, we rederive the known chiral perturbation theory results of Aoki and Fukaya, but using the nonperturbatively-valid chiral theory worked out by Golterman, Sharpe and Singleton, and by Sharpe and Shoresh. We then extend these calculations to heavy-light mesons. Results when staggered taste-violations are important are also presented. The derived $Q^2$ dependence is compared to that of simulations using the MILC collaboration's ensembles of lattices with four flavors of HISQ dynamical quarks. We find agreement, albeit with large statistical errors. These results can be used to correct for the leading effects of unequilibrated $Q^2$, or to make estimates of the systematic error coming from the failure to equilibrate $Q^2$. In an appendix, we show that the partially quenched chiral theory may be extended beyond a lower bound on valence masses discovered by Sharpe and Shoresh. Subtleties occurring when a sea-quark mass vanishes are discussed in another appendix.

    ↳ hep-lathep-phPRD(2018)·31 citations
18. 18*

    Estimating the Charm Quark Diffusion Coefficient and thermalization time from D meson spectra at RHIC and LHC

    Francesco Scardina🇮🇹 · Santosh K. Das🇮🇹 · Vincenzo Minissale🇮🇹 · Salvatore Plumari🇮🇹 · Vincenzo Greco🇮🇹

    We describe the propagation of charm quarks in the quark-gluon plasma (QGP) by means of a Boltzmann transport approach. Non-perturbative interaction between heavy quarks and light quarks have been taken into account through a quasi-particle approach in which light partons are dressed with thermal masses tuned to lQCD thermodynamics. Such a model is able to describe the main feature of the non-perturbative dynamics: the enhancement of the interaction strength near $T_c$. We show that the resulting charm in-medium evolution is able to correctly predict simultaneously the nuclear suppression factor, $R_{AA}$, and the elliptic flow, $v_2$, at both RHIC and LHC energies and at different centralities. The hadronization of charm quarks is described by mean of an hybrid model of fragmentation plus coalescence and plays a key role toward the agreeement with experimental data. We also performed calculations within the Langevin approach which can lead to very similar $R_{AA}(p_T)$ as Boltzmann, but the charm drag coefficient as to be reduced by about a $30\%$ and also generates an elliptic flow $v_2(p_T)$ is about a $15\%$ smaller. We finally compare the space diffusion coefficient $2\pi T{D}_s$ extracted by our phenomenological approach to lattice QCD results, finding a satisfying agreement within the present systematic uncertainties. Our analysis implies a charm thermalization time, in the $p\to 0$ limit, of about $4-6fm/c$ which is smaller than the QGP lifetime at LHC energy.

    ↳ nucl-thhep-phnucl-exPRC(2017)·200 citations
19. 19*

    Pion transverse-momentum spectrum and elliptic anisotropy of partially coherent source

    Peng Ru🇨🇳 · Ghulam Bary🇨🇳 · Wei-Ning Zhang🇨🇳

    In this letter, we study the pion momentum distribution of a coherent source and investigate the influences of coherent emission on the pion transverse-momentum ($p_T$) spectrum and elliptic anisotropy. With a partially coherent source, constructed by a conventional viscous hydrodynamics model (chaotic part) and a parameterized expanding coherent source model, we reproduce the pion $p_T$ spectrum and elliptic anisotropy coefficient $v_2(p_T)$ in the peripheral Pb-Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV. It is found that the influences of coherent emission on the pion $p_T$ spectrum and $v_2(p_T)$ are related to the initial size and shape of the coherent source, largely due to the interference effect. However, the effect of source dynamical evolution on coherent emission is relatively small. The results of the partially coherent source with 33% coherent emission and 67% chaotic emission are consistent with the experimental measurements of the pion $p_T$ spectrum, $v_2(p_T)$, and especially four-pion Bose-Einstein correlations.

    ↳ nucl-thhep-phnucl-exPLB(2018)·6 citations
20. 20*

    Nucleon Form Factors in Nuclear Medium

    Chanyong Park🇰🇷 · Jung Hun Lee🇰🇷

    By using the AdS/CFT correspondence, we investigate various form factors between nucleons and mesons in a nuclear medium. In order to describe a nuclear medium holographically, we take into account the thermal charged AdS geometry with an appropriate IR cutoff. After introducing an anomalous dimension as a free parameter, we investigate how the nucleon's mass is affected by the change of the anomalous dimension. Moreover, we study how the form factors of nucleons rely on the properties of the nuclear medium. We show that in a nuclear medium with different numbers of proton and neutron, the degenerated nucleon form factor in the vacuum is split to four different values depending on the isospin charges of nucleon and meson.

    ↳ hep-thhep-phInt.J.Mod.Phys.A(2018)·2 citations
21. 21*

    Probing signatures of bounce inflation with current observations

    Shulei Ni🇨🇳 · Hong Li🇨🇳 · Taotao Qiu🇨🇳 · Wei Zheng🇨🇳 · Xin Zhang🇨🇳

    The aim of this paper is to probe the features of the bouncing cosmology with the current observational data. Basing on bounce inflation model, with high derivative term, we propose a general parametrization of primordial power spectrum which includes the typical bouncing parameters, such as bouncing time-scale, and energy scale. By applying Markov Chain Monto Carlo analysis with current data combination of Planck 2015, BAO and JLA, we report the posterior probability distributions of the parameters. We find that, bouncing models can well explain CMB observations, especially the deficit and oscillation on large scale in TT power spectrum.

    ↳ astro-ph.COgr-qchep-phhep-thEPJC(2018)·15 citations
22. 22*

    Meson masses in electromagnetic fields with Wilson fermions

    Gunnar S. Bali🇩🇪 · Bastian B. Brandt🇩🇪 · Gergely Endrodi🇩🇪 · Benjamin Glaessle🇩🇪

    We determine the light meson spectrum in QCD in the presence of background magnetic fields using quenched Wilson fermions. Our continuum extrapolated results indicate a monotonous reduction of the connected neutral pion mass as the magnetic field grows. The vector meson mass is found to remain nonzero, a finding relevant for the conjectured $\rho$-meson condensation at strong magnetic fields. The continuum extrapolation was facilitated by adding a novel magnetic field-dependent improvement term to the additive quark mass renormalization. Without this term, sizable lattice artifacts that would deceptively indicate an unphysical rise of the connected neutral pion mass for strong magnetic fields are present. We also investigate the impact of these lattice artifacts on further observables like magnetic polarizabilities and discuss the magnetic field-induced mixing between $\rho$-mesons and pions. We also derive Ward-Takashi identities for QCD+QED both in the continuum formulation and for (order $a$-improved) Wilson fermions.

    ↳ hep-lathep-phnucl-thPRD(2018)·151 citations
23. 23*

    Goldstino in supersymmetric Bose-Fermi mixtures in the presence of Bose Einstein condensate

    Jean-Paul Blaizot🇫🇷 · Yoshimasa Hidaka🇯🇵 · Daisuke Satow🇩🇪

    We analyze the spectral properties of the Goldstino excitation in a Bose-Fermi mixture of cold atoms, whose masses and interaction strengths are tuned so that the hamiltonian is supersymmetric. We consider systems at zero temperature and assume that, in the weak coupling regime, the fermions form a Fermi sea, while the bosons form a Bose-Einstein condensate. We study the excitation spectrum within a simple extension of the random phase approximation, taking into account the mixing between the supercharge and the fermion caused by the condensate. This mixing affects the fermion spectrum strongly. We argue that the corresponding modification of the fermion spectrum, and the associated fermion distribution in momentum space, could be accessible experimentally, and potentially allow for a determination of the Goldstino properties.

    ↳ cond-mat.quant-gashep-phPRA(2017)·16 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.