Wed·Sep 2, 2015Wednesday·September 2, 2015

1. 01*

   Regularization of the Light-Cone Gauge Gluon Propagator Singularities Using Sub-Gauge Conditions

   Giovanni A. Chirilli🇺🇸 · Yuri V. Kovchegov🇺🇸 · Douglas E. Wertepny🇺🇸

   Perturbative QCD calculations in the light-cone gauge have long suffered from the ambiguity associated with the regularization of the poles in the gluon propagator. In this work we study sub-gauge conditions within the light-cone gauge corresponding to several known ways of regulating the gluon propagator. Using the functional integral calculation of the gluon propagator, we rederive the known sub-gauge conditions for the theta-function gauges and identify the sub-gauge condition for the principal value (PV) regularization of the gluon propagator's light-cone poles. The obtained sub-gauge condition for the PV case is further verified by a sample calculation of the classical Yang-Mills field of two collinear ultrarelativistic point color charges. Our method does not allow one to construct a sub-gauge condition corresponding to the well-known Mandelstam-Leibbrandt prescription for regulating the gluon propagator poles.

   hep-phhep-thJHEP(2015)·17 citations
2. 02*

   Initial state and thermalization in the Color Glass Condensate framework

   F. Gelis🇫🇷

   In this review, I present the description of the early stages of heavy ion collisions at high energy in the Color Glass Condensate framework, from the pre-collision high energy nuclear wavefunction to the point where hydrodynamics may start becoming applicable.

   hep-phnucl-thIJMPE(2015)·40 citations
3. 03*

   Sensitivity to Z-prime and non-standard neutrino interactions from ultra-low threshold neutrino-nucleus coherent scattering

   Bhaskar Dutta🇺🇸 · Rupak Mahapatra🇺🇸 · Louis E. Strigari🇺🇸 · Joel W. Walker🇺🇸

   We discuss prospects for probing Z-prime and non-standard neutrino interactions using neutrino-nucleus coherent scattering with ultra-low energy (~ 10 eV) threshold Si and Ge detectors. The analysis is performed in the context of a specific and contemporary reactor-based experimental proposal, developed in cooperation with the Nuclear Science Center at Texas A&M University, and referencing available technology based upon economical and scalable detector arrays. For expected exposures, we show that sensitivity to the Z-prime mass is on the order of several TeV, and is complementary to the LHC search with low mass detectors in the near term. This technology is also shown to provide sensitivity to the neutrino magnetic moment, at a level that surpasses terrestrial limits, and is competitive with more stringent astrophysical bounds. We demonstrate the benefits of combining silicon and germanium detectors for distinguishing between classes of models of new physics, and for suppressing correlated systematic uncertainties.

   hep-phastro-ph.HEhep-exnucl-ex+1PRD(2016)·76 citations
4. 04*

   Axion dark matter: strings and their cores

   Leesa Fleury🇨🇦 · Guy D. Moore🇩🇪

   Axions constitute a well-motivated dark matter candidate, and if PQ symmetry breaking occurred after inflation, it should be possible to make a clean prediction for the relation between the axion mass and the axion dark matter density. We show that axion (or other global) string networks in 3D have a network density that depends logarithmically on the string separation-to-core ratio. This logarithm would be about 10 times larger in axion cosmology than what we can achieve in numerical simulations. We simulate axion production in the early Universe, finding that, for the separation-to-core ratios we can achieve, the changing density of the network has little impact on the axion production efficiency.

   hep-phastro-ph.COJCAP(2016)·153 citations
5. 05*

   Heating up the Galaxy with Hidden Photons

   Sergei Dubovsky🇺🇸 · Guzmán Hernández-Chifflet🇺🇸

   We elaborate on the dynamics of ionized interstellar medium in the presence of hidden photon dark matter. Our main focus is the ultra-light regime, where the hidden photon mass is smaller than the plasma frequency in the Milky Way. We point out that as a result of the Galactic plasma shielding direct detection of ultra-light photons in this mass range is especially challenging. However, we demonstrate that ultra-light hidden photon dark matter provides a powerful heating source for the ionized interstellar medium. This results in a strong bound on the kinetic mixing between hidden and regular photons all the way down to the hidden photon masses of order $10^{-20}$ eV.

   hep-phastro-ph.COastro-ph.GAJCAP(2015)·82 citations
6. 06*

   Is the Relaxion an Axion?

   Rick S. Gupta🇮🇱 · Zohar Komargodski🇮🇱 · Gilad Perez🇮🇱 · Lorenzo Ubaldi🇮🇱

   We consider the recently proposed cosmological relaxation mechanism where the hierarchy problem is ameliorated, and the electroweak scale is dynamically selected by a slowly rolling axion field. We argue that, in its simplest form, the construction breaks a gauge symmetry that always exists for pseudo-Nambu-Goldstone bosons (in particular the axion). The small parameter in the relaxion model is therefore not technically natural as it breaks a gauge symmetry rather than global symmetries only. The consistency of the theory generically implies that the cutoff must lie around the electroweak scale, but not qualitatively higher. We discuss several ways to evade the above conclusion. Some of them may be sufficient to increase the cutoff to the few-TeV range (and therefore may be relevant for the little-hierarchy problem). To demonstrate the ideas in a concrete setting we consider a model with a familon, the Nambu-Goldstone boson of a spontaneously broken chiral flavor symmetry. The model has some interesting collider-physics aspects and contains a viable weakly interacting dark matter candidate.

   hep-phhep-thJHEP(2016)·109 citations
7. 07*

   New Prospects in Fixed Target Searches for Dark Forces with the SeaQuest Experiment at Fermilab

   S. Gardner🇺🇸 · R. J. Holt🇺🇸 · A. S. Tadepalli🇺🇸

   An intense, 120 GeV proton beam incident on an extremely long, iron target generates enormous numbers of light-mass particles that also decay within that target. If one of these particles decays to a final state with a hidden gauge boson, or if such a particle is produced as a result of the initial collision, then that weakly interacting, hidden-sector particle may traverse the remainder of the target and be detected downstream through its possible decay to an $e^{+}{e}^{-}$, ${\mu }^{+}{\mu }^{-}$, or ${\pi }^{+}{\pi }^{-}$ final state. These conditions can be realized through an extension of the SeaQuest experiment at Fermilab, and in this initial investigation we consider how it can serve as an ultrasensitive probe of hidden vector gauge forces, both Abelian and non-Abelian. A light, weakly coupled hidden sector may well explain the dark matter established through astrophysical observations, and the proposed search can provide tangible evidence for its existence --- or, alternatively, constrain a "sea" of possibilities.

   hep-phPRD(2016)·95 citations
8. 08*

   Implications of a Running Dark Photon Coupling

   Hooman Davoudiasl🇺🇸

   For an "invisible" dark photon $Z_d$ that dominantly decays into dark states, the running of its fine structure constant ${\alpha }_d$ with momentum transfer $q>m_{Z_d}$ could be significant. A similar running in the kinetic mixing parameter ${\epsilon }^2$ can be induced through its dependence on ${\alpha }_d(q)$. The running of couplings could potentially be detected in "dark matter beam" experiments, for which theoretical considerations imply ${\alpha }_d(m_{Z_d})\lesssim 0.5$.

   hep-phhep-ex0 citations
9. 09*

   Application of AdS/QCD to B physics

   Mohammad Ahmady🇨🇦 · Sébastien Lord🇨🇦 · Ruben Sandapen🇨🇦

   We build on the success of AdS/QCD in predicting diffractive $\rho$ meson production to obtain the transition form factors for B decays to light mesons. Consequently, we predict several observables associated with $B\to \rho \ell \nu$ semileptonic and $B\to K^{\ast }{\mu }^{+}{\mu }^{-}$ dileptonic decays. Our predictions are compared to the available experimental data.

   hep-phhep-thNucl.Part.Phys.Proc.(2016)·3 citations
10. 10*

    Structure of near-threshold quasi-bound states

    Yuki Kamiya🇯🇵 · Tetsuo Hyodo🇯🇵

    We study the compositeness of near-threshold quasi-bound states in the framework of effective field theory. From the viewpoint of the low-energy universality, we revisit the model-independent relations between the structure of the bound state and the observables in the weak binding limit. The effective field theory is utilized to generalize the weak-binding relation of the stable bound states to unstable quasi-bound states with decay modes. We present the interpretation of the complex values of the compositeness for the unstable states. Combining the model-independent relation and the threshold observables extracted from the experimental data, we show that Lambda(1405) is dominated by the Kbar N molecular structure and that a_0(980) is dominated by the non-Kbar K component.

    hep-phhep-exnucl-thPRC(2016)·74 citations
11. 11*

    Glueballs amass at RHIC and LHC Colliders! - The early quarkless 1st order phase transition at $T=270$ MeV - from pure Yang-Mills glue plasma to GlueBall-Hagedorn states

    Horst Stoecker🇩🇪 · Kai Zhou🇩🇪 · Stefan Schramm🇩🇪 · Florian Senzel🇩🇪 · Carsten Greiner🇩🇪 · Maxim Beitel🇩🇪 · Kai Gallmeister🇩🇪 · Mark Gorenstein🇺🇦 · Igor Mishustin🇩🇪 · David Vasak🇩🇪 · Jan Steinheimer🇩🇪 · Juergen Struckmeier🇩🇪 and 9 other authors

    The early stage of high multiplicity pp, pA and AA collider is represented by a nearly quarkless, hot, deconfined pure gluon plasma. According to pure Yang-Mills Lattice Gauge Theory, this hot pure glue matter undergoes, at a high temperature, $T_c=270$ MeV, a first order phase transition into a confined Hagedorn-GlueBall fluid. These new scenario should be characterized by a suppression of high $p_T$ photons and dileptons, baryon suppression and enhanced strange meson production. We propose to observe this newly predicted class of events at LHC and RHIC.

    hep-phnucl-exnucl-thJ.Phys.G(2016)·33 citations
12. 12*

    Higgs Boson Production via Gluon Fusion: Soft-Gluon Resummation including Mass Effects

    Timo Schmidt🇨🇭 · Michael Spira🇨🇭

    We analyze soft and collinear gluon resummation effects at the N${}^3$LL level for Standard Model Higgs boson production via gluon fusion $gg\to H$ and the neutral scalar and pseudoscalar Higgs bosons of the minimal supersymmetric extension at the N${}^3$LL and NNLL level, respectively. We introduce refinements in the treatment of quark mass effects and subleading collinear gluon effects within the resummation. Soft and collinear gluon resummation effects amount to up to about 5% beyond the fixed-order results for scalar and pseudoscalar Higgs boson production.

    hep-phhep-exPRD(2016)·53 citations
13. 13*

    Hadronic contributions to electroweak observables within DPT

    A.V.Nesterenko🇷🇺

    Dispersive approach to quantum chromodynamics is applied to the assessment of hadronic contributions to electroweak observables. The employed approach merges the corresponding perturbative input with intrinsically nonperturbative constraints, which originate in the respective kinematic restrictions. The evaluated hadronic contributions to the muon anomalous magnetic moment and to the shift of the electromagnetic fine structure constant at the scale of Z boson mass conform with recent assessments of these quantities.

    hep-phhep-latNucl.Part.Phys.Proc.(2016)·7 citations
14. 14*

    Parton distribution functions with QED corrections

    Stefano Carrazza🇮🇹

    We present the first unbiased determination of parton distribution functions (PDFs) with electroweak corrections. The aim of this thesis is to provide an exhaustive description of the theoretical framework and the technical implementation which leads to the determination of a set of PDFs which includes the photon PDF and quantum electrodynamics (QED) contributions to parton evolution. First, we introduce and motivate the need of including electroweak corrections to PDFs, providing phenomenological examples and presenting an overview of the current state of the art in PDF fits. The theoretical implications of such corrections are then described through the implementation of the combined QCD+QED evolution in APFEL, a public code for the solution of the PDF evolution developed particularly for this thesis. We proceed by presenting the new structure of the Neural-Network PDF (NNPDF) methodology used for the extraction of this set of PDFs with QED corrections. We then provide a first determination of the full set of PDFs based on deep-inelastic scattering data and LHC data for $W$ and $Z/{\gamma }^{\ast }$ Drell-Yan production, using leading-order QED and NLO or NNLO QCD: the so-called NNPDF2.3QED set of PDFs. We perform a preliminary investigation of the phenomenological implications of NNPDF2.3QED set, in particular, focusing on the photon-induced corrections to direct photon production at HERA, high-mass dilepton and $W$ pair production at the LHC and finally, providing a first determination of lepton PDFs through the APFEL evolution. We conclude with a summary of the technological upgrades required for the improvement of future PDF determinations with electroweak corrections.

    hep-phhep-ex24 citations
15. 15*

    A Dynamic Modification to Sneutrino Chaotic Inflation

    Abhijit Kumar Saha🇮🇳 · Arunansu Sil🇮🇳

    We consider a right-handed scalar neutrino as the inflaton which carries a gravitational coupling with a supersymmetric QCD sector responsible for breaking supersymmetry dynamically. The framework suggests an inflaton potential which is a deformed version of the quadratic chaotic inflation leading to a flatter potential. We find that this deformation results a sizable tensor to scalar ratio which falls within the allowed region by PLANCK 2015. At the same time supersymmetry breaking at the end of inflation can naturally be induced in this set-up. The symmetries required to construct the framework allows the neutrino masses and mixing to be of right order.

    hep-phJHEP(2015)·7 citations
16. 16*

    Mass reconstruction with $M_2$ under constraint in semi-invisible production at a hadron collider

    Partha Konar🇮🇳 · Abhaya Kumar Swain🇮🇳

    The mass-constraining variable $M_2$, a $(1+3)$-dimensional natural successor of extremely popular $M_{T2}$, possesses an array of rich features having the ability to use on-shell mass constraints in semi-invisible production at a hadron collider. In this work, we investigate the consequence of applying a heavy resonance mass-shell constraint in the context of a semi-invisible antler decay topology produced at the LHC. Our proposed variable, under additional constraint, develops a new kink solution at the true masses. This enables one to determine the invisible particle mass simultaneously with the parent particle mass from these events. We analyze in a way to measure this kink optimally, exploring the origin and the properties of such interesting characteristics. We also study the event reconstruction capability inferred from this new variable and find that the resulting momenta are unique and well correlated with true invisible particle momenta.

    hep-phhep-exPRD(2016)·24 citations
17. 17*

    Mass Spectra of $0^{+-}$, $1^{-+}$, and $2^{+-}$ Exotic Glueballs

    Liang Tang🇨🇳 · Cong-Feng Qiao🇨🇳

    With appropriate interpolating currents the mass spectra of $0^{+-}$, $1^{-+}$, and $2^{+-}$ oddballs are studied in the framework of QCD sum rules (QCDSR). We find there exits one stable $0^{+-}$ oddball with mass of $4.57\pm 0.13\text{GeV}$, and one stable $2^{+-}$ oddball with mass of $6.06\pm 0.13\text{GeV}$, whereas, no stable $1^{-+}$ oddball shows up. The possible production and decay modes of these glueballs with unconventional quantum numbers are analyzed, which are hopefully measurable in either BELLEII, PANDA, Super-B or LHCb experiments.

    hep-phhep-exNPB(2016)·39 citations
18. 18*

    Theoretical uncertainties on QCD computations and the divergence of the perturbative expansion

    Andrea Isgrò🇮🇹

    We analyze the divergent behaviour of the perturbative expansion in QCD, focusing on some well-known sources of divergence such as renormalons, instantons and the Landau pole divergence. We determine at which perturbative order each of these sources of divergence becomes dominant. In particular, we consider the cross section of Higgs and top production in gluon fusion at the LHC and we construct a model for the theoretical uncertainty on the missing higher orders in the perturbative expansion. We compare our model with some other existing models for theoretical uncertainty.

    hep-ph1 citation
19. 19*

    Accidentally safe extensions of the Standard Model

    Luca Di Luzio🇮🇹 · Ramona Grober🇮🇹 · Jernej F. Kamenik🇸🇮 · Marco Nardecchia🇬🇧

    We discuss a class of weak-scale extensions of the Standard Model which is completely invisible to low-energy indirect probes. The typical signature of this scenario is the existence of new charged and/or colored states which are stable on the scale of high-energy particle detectors.

    hep-ph1 citation
20. 20*

    Directional Resolution of Dish Antenna Experiments to Search for WISPy Dark Matter

    Joerg Jaeckel🇩🇪 · Stefan Knirck🇩🇪

    Dark matter consisting of very light and very weakly interacting particles such as axions, axion-like particles and hidden photons could be detected using reflective surfaces. On such reflectors some of the dark matter particles are converted into photons and, given a suitable geometry, concentrated on the detector. This technique offers sensitivity to the direction of the velocity of the dark matter particles. In this note we investigate how far spherical mirrors can concentrate the generated photons and what this implies for the resolution in directional detection as well as the sensitivity of discovery experiments not aiming for directional resolution. Finally we discuss an improved setup using a combination of a reflecting plane with focussing optics.

    hep-phhep-exJCAP(2016)·42 citations
21. 21*

    Evaluation of the forward Compton scattering off protons: I. Spin-independent amplitude

    Oleksii Gryniuk🇩🇪 · Franziska Hagelstein🇩🇪 · Vladimir Pascalutsa (JGU Mainz)🇩🇪

    We evaluate the forward Compton scattering off the proton, based on Kramers-Kronig kind of relations which express the Compton amplitudes in terms of integrals of total photoabsorption cross sections. We obtain two distinct fits to the world data on the unpolarized total photoabsorption cross section, and evaluate the various spin-independent sum rules using these fits. For the sum of proton electric and magnetic dipole polarizabilities, governed by the Baldin sum rule, we obtain the following average (between the two fits): ${\alpha }_{E1}+{\beta }_{M1}=14.0(2)\times 10^{-4}{\mathrm{fm}}^3$. An analogous sum rule involving the quadrupole polarizabilities of the proton is evaluated too. The spin-independent forward amplitude of proton Compton scattering is evaluated in a broad energy range. The results are compared with previous evaluations and the only experimental data point for this amplitude (at 2.2 GeV). We remark on sum rules for the elastic component of polarizabilities.

    ↳ nucl-thhep-phnucl-exPRD(2015)·39 citations
22. 22*

    Higgs-Yukawa model with higher dimension operators via extended mean field theory

    Oscar Akerlund🇨🇭 · Philippe de Forcrand🇨🇭

    Using extended mean field theory (EMFT) on the lattice, we study properties of the Higgs-Yukawa model as an approximation of the standard model Higgs sector, and the effect of higher dimension operators. We note that the discussion of vacuum stability is completely modified in the presence of a ${\varphi }^6$ term, and that the Higgs mass no longer appears fine tuned. We also study the finite temperature transition. Without higher dimension operators the transition is found to be second order (crossover with gauge fields) for the experimental value of the Higgs mass $M_h=125$ GeV. By taking a ${\varphi }^6$ interaction in the Higgs potential as a proxy for a UV completion of the standard model, the transition becomes stronger and turns first order if the scale of new physics, i.e. the mass of the lightest mediator particle, is around $1.5$ TeV. This implies that electroweak baryogenesis may be viable in models which introduce new particles around that scale.

    ↳ hep-lathep-phPRD(2016)·17 citations
23. 23*

    The Excess Radio Background and Fast Radio Transients

    John Kehayias🇯🇵 · Thomas W. Kephart🇺🇸 · Thomas J. Weiler🇺🇸

    In the last few years ARCADE 2, combined with older experiments, has detected an additional radio background, measured as a temperature and ranging in frequency from 22 MHz to 10 GHz, not accounted for by known radio sources and the cosmic microwave background. One type of source which has not been considered in the radio background is that of fast transients (those with event times much less than the observing time). We present a simple estimate, and a more detailed calculation, for the contribution of radio transients to the diffuse background. As a timely example, we estimate the contribution from the recently-discovered fast radio bursts (FRBs). Although their contribution is likely 6 or 7 orders of magnitude too small (though there are large uncertainties in FRB parameters) to account for the ARCADE~2 excess, our development is general and so can be applied to any fast transient sources, discovered or yet to be discovered. We estimate parameter values necessary for transient sources to noticeably contribute to the radio background.

    ↳ astro-ph.COastro-ph.HEhep-phJCAP(2015)·4 citations
24. 24*

    D6-Brane Model Building on Z(2)xZ(6): MSSM-like and Left-Right Symmetric Models

    Jill Ecker🇩🇪 · Gabriele Honecker🇩🇪 · Wieland Staessens🇪🇸

    We perform a systematic search for globally defined MSSM-like and left-right symmetric models on D6-branes on the T6/Z(2)xZ(6)xOR orientifold with discrete torsion. Our search is exhaustive for models that are independent of the value of the one free complex structure modulus. Preliminary investigations suggest that there exists one prototype of visible sector for MSSM-like and another for left-right symmetric models with differences arising from various hidden sector completions to global models. For each prototype, we provide the full matter spectrum, as well as the Yukawa and other three-point couplings needed to render vector-like matter states massive. This provides us with tentative explanations for the mass hierarchies within the quark and lepton sectors. We also observe that the MSSM-like models correspond to explicit realisations of the supersymmetric DFSZ axion model, and that the left-right symmetric models allow for global completions with either completely decoupled hidden sectors or with some messenger states charged under both visible and hidden gauge groups.

    ↳ hep-thhep-phNPB(2015)·16 citations
25. 25*

    A conservative assessment of the current constraints on dark matter annihilation from Cosmic Rays and CMB observations

    Nicolò Masi🇮🇹 · Mario Ballardini🇮🇹

    In view of the current interest in combining different observations to constraint annihilating WIMP dark matter, we examine the relation between the Sommerfeld effect at the recombination epoch and in the galactic halo. By considering an up-to-date collection of interpolations of cosmic rays lepton data (AMS-02 2014, Fermi and PAMELA), as dark matter annihilation signals, we show that current cosmic rays measurements and recent Planck 2015 constraints from CMB anisotropies almost overlap for dark matter masses of the order of few $TeV$, although great theoretical uncertainties afflict cosmic rays and dark matter descriptions. Combining cosmic rays fits we obtain proper minimal regions allowed by CMB observations, especially for $\mu$ and $\tau$ annihilation channels, once assumed viable values of the efficiency factor for energy absorption at recombination: the results are consistent with those obtained by the Planck collaboration but allow a slightly larger overlap between Cosmic Rays constraints from the lepton sector and CMB. Incoming AMS-02 measurements of cosmic rays antiprotons will help to clarify the conundrum.

    ↳ astro-ph.COhep-phInt.J.Mod.Phys.D(2016)·5 citations
26. 26*

    Recent Results on Light Hadrons from the BESIII Experiment

    Peilian Liu (On behalf of the BESIII Collaboration)🇨🇳

    The BESIII experiment has collected world's largest direct $e^{+}{e}^{-}$ colliding beam data at the $J/\psi$, ${\psi }^{\prime }$, $\psi$(3770) and at and around the $Y$(4260). These data have enabled the study of hadrons at unprecedented precisions. We present results on the light hadron spectroscopy, production of hadrons in radiative decays of charmonia, observation of new excited $N^{\ast }$ baryons and of anomalous decays of the $\eta /{\eta }^{\prime }$ states.

    ↳ hep-exhep-ph0 citations
27. 27*

    Cosmic Transients Test Einstein's Equivalence Principle out to GeV Energies

    He Gao🇨🇳 · Xue-Feng Wu🇨🇳 · Peter Mészáros🇺🇸

    The Einstein Equivalence Principle (EEP) can be probed with astrophysical sources emitting simultaneously different types of neutral particles, or particles with varying energies, by testing their time of flight through the same gravitational field. Here we use the time delays between correlated photons from cosmological transients to constrain the accuracy of the EEP. We take data from two gamma-ray bursts as an example, and use, as a lower limit to the theoretical time delays between different energies, delays arising from only the gravitational field of our own galaxy. We then show that the parameterized post-Newtonian parameter $\gamma$ is the same for photons over energy ranges between eV and MeV and between MeV and GeV to a part in $10^{-7}$, which is at least one order of magnitude better than previous limits. Combining this bound on the wavelength dependence of $\gamma$ with the absolute bound $|\gamma -1|<0.3\%$ from light-deflection measurements at optical (eV) wavelengths, we thus extend this absolute bound on $\gamma$ to GeV energies.

    ↳ astro-ph.HEgr-qchep-phhep-thApJ(2015)·68 citations
28. 28*

    Thermodynamical aspects of running vacuum models

    J. A. S. Lima🇧🇷 · Spyros Basilakos🇬🇷 · Joan Solà🇪🇸

    The thermal history of a large class of running vacuum models in which the effective cosmological term is described by a truncated power series of the Hubble rate, whose dominant term is $\Lambda (H)\propto H^{n+2}$, is discussed in detail. Specifically, by assuming that the ultra-relativistic particles produced by the vacuum decay emerge into space-time in such a way that its energy density ${\rho }_r\propto T^4$, the temperature evolution law and the increasing entropy function are analytically calculated. For the whole class of vacuum models explored here we findthat the primeval value of the comoving radiation entropy density (associated to effectively massless particles) starts from zero and evolves extremely fast until reaching a maximum near the end of the vacuum decay phase, where it saturates. The late time conservation of the radiation entropy during the adiabatic FRW phase also guarantees that the whole class of running vacuum models predicts thesame correct value of the present day entropy, $S_0\sim 10^{87-88}$ (in natural units), independently of the initial conditions. In addition, by assuming Gibbons-Hawking temperature as an initial condition, we find that the ratio between the late time and primordial vacuum energy densities is in agreement with naive estimates from quantum field theory, namely, ${\rho }_{\Lambda 0}/{\rho }_{\Lambda I}\sim 10^{-123}$. Such results are independent on the power $n$ and suggests that the observed Universe may evolve smoothly between two extreme, unstable, nonsingular de Sitter phases.

    ↳ gr-qcastro-ph.COhep-phhep-thEPJC(2016)·65 citations
29. 29*

    Heavy Hadrons in Dense Matter

    Laura Tolos🇪🇸 · Carmen Garcia-Recio🇪🇸 · Carlos Hidalgo-Duque🇪🇸 · Juan Nieves🇪🇸 · Olena Romanets🇳🇱 · Lorenzo Luis Salcedo🇪🇸 · Juan M. Torres-Rincon🇫🇷

    We study the behavior of dynamically-generated baryon resonances with heavy-quark content within a unitarized coupled-channel theory in matter that fulfills heavy-quark spin symmetry constraints. We analyze the implications for the formation of charmed mesic nuclei and the propagation of heavy mesons in heavy-ion collisions from RHIC to FAIR.

    ↳ nucl-thhep-exhep-phJ.Phys.Conf.Ser.(2016)·1 citation
30. 30*

    Strong-coupling phases of 3D Dirac and Weyl semimetals. A renormalization group approach

    J. Gonzalez🇪🇸

    We investigate the strong-coupling phases that may arise in 3D Dirac and Weyl semimetals under the effect of the long-range Coulomb interaction, considering the many-body theory of these electron systems as a variant of the conventional fully relativistic Quantum Electrodynamics (QED). For this purpose, we apply two different nonperturbative approaches, consisting in the sum of ladder diagrams and taking the limit of a large number N of fermion flavors. We benefit from the renormalizability that the theory shows in both cases to compute the anomalous scaling dimensions of different operators exclusively in terms of the renormalized coupling constant, allowing us to determine the precise location of the singularities signaling the onset of the strong-coupling phases. We show then that the QED of 3D Dirac semimetals has two competing effects at strong coupling. One of them is the tendency to chiral symmetry breaking and dynamical mass generation, which are analogous to the same phenomena arising in the conventional QED at strong coupling. This trend is however outweighed by the strong suppression of electron quasiparticles that takes place at large N, leading to a different type of critical point at sufficiently large interaction strength, shared also by the 3D Weyl semimetals. Overall, the phase diagram of the 3D Dirac semimetals turns out to be richer than that of their 2D counterparts, displaying a transition to a phase with non-Fermi liquid behavior which may be observed in materials hosting a sufficiently large number of Dirac or Weyl points.

    ↳ cond-mat.mes-hallcond-mat.str-elhep-phhep-thJHEP(2015)·11 citations
31. 31*

    Wilson loops at strong coupling for curved contours with cusps

    Harald Dorn🇩🇪

    We construct the minimal surface in AdS, relevant for the strong coupling behaviour of local supersymmetric Wilson loops in N=4 SYM for a closed contour formed out of segments of two intersecting circles. Its regularised area is calculated including all divergent parts and the finite renormalised term. Furthermore we prove, that for generic planar curved contours with cusps the cusp anomalous dimensions are functions of the respective cusp angles alone. They do not depend on other local data of the cusps.

    ↳ hep-thhep-phJ.Phys.A(2016)·13 citations
32. 32*

    VHEeP: A very high energy electron-proton collider based on proton-driven plasma wakefield acceleration

    Allen Caldwell🇩🇪 · Matthew Wing🇬🇧

    Based on current CERN infrastructure, an electron-proton collider is proposed at a centre-of-mass energy of about 9 TeV. A 7 TeV LHC bunch is used as the proton driver to create a plasma wakefield which then accelerates electrons to 3 TeV, these then colliding with the other 7 TeV LHC proton beam. The basic parameters of the collider are presented, which although of very high energy, has integrated luminosities of the order of 1 pb${}^{-1}$/year. For such a collider, with a centre-of-mass energy 30 times greater than HERA, parton momentum fractions, $x$, down to about $10^{-8}$ are accessible for $Q^2$ of 1 GeV${}^2$ and could lead to effects of saturation or some other breakdown of DGLAP being observed. The total photon-proton cross section can be measured up to very high energies and also at different energies as the possibility of varying the electron beam energy is assumed; this could have synergy with cosmic-ray physics. Other physics which can be pursued at such a collider are contact interaction searches, such as quark and electron substructure, and measurements of the proton structure as well as other more conventional measurements of QCD at high energies and in a new kinematic regime. The events at very low $x$ will lead to electrons and the hadronic final state produced at very low angles and so a novel spectrometer device will be needed to measure these. First ideas of the physics programme of such a collider are given.

    ↳ physics.acc-phhep-exhep-phPoS(2015)·5 citations
33. 33*

    Inhomogeneous Thermal Quenches

    Kiyoumars A. Sohrabi🇨🇭

    We describe holographic thermal quenches that are inhomogeneous in space. The main characteristic of the quench is to take the system far from its equilibrium configuration. Except special extreme cases, the problem has no analytic solution. Using the numerical holography methods, we study different observables that measure thermalization such as the time evolution of the apparent horizon, two-point Wightman function and entanglement entropy (EE). Having an extra nontrivial spacial direction, allows us to study this peculiar generalization since we categorize the problem based on whether we do the measurements along this special direction or perpendicular to it. Exciting new features appear that are absent in the common computations in the literature; the appearance of negative EE valleys surrounding the positive EE hills and abrupt quenches that occupy the whole space at their universal limit are some of the results of this paper. Physical explanation is given and connections to the Cardy's idea of thermalization are discussed.

    ↳ hep-thgr-qchep-lathep-ph+1PRD(2017)·6 citations
34. 34*

    The Quarkyonic Star

    Kenji Fukushima🇯🇵 · Toru Kojo🇺🇸

    We discuss theoretical scenarios on crossover between nuclear matter (NM) and quark matter (QM). We classify various possibilities into three major scenarios according to the onset of diquark degrees of freedom that characterizes color-superconducting (CSC) states. In the conventional scenario NM occurs at the liquid-gas (or liquid-vacuum at zero temperature) phase transition and QM occurs next, after which CSC eventually appears. With the effect of strong correlation, the BEC-BCS scenario implies that CSC occurs next to NM and QM comes last in the BCS regime. We adopt the quarkyonic scenario in which NM, QM, and CSC are theoretically indistinguishable and thus these names refer to not distinct states but relevant descriptions of the same physical system. Based on this idea we propose a natural scheme to interpolate NM near normal nuclear density and CSC with vector coupling at high baryon density. We finally discuss the mass-radius relation of the neutron star and constraints on parameters in the proposed scheme.

    ↳ nucl-thastro-ph.HEhep-phApJ(2016)·102 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.