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Nuclear Theory·nucl-th

Wednesday·May 13, 2015

6 papers—1 primary·5 cross-listed

All6Primary1Cross-lists5
  1. 01

    Scattering cluster wave functions on the lattice using the adiabatic projection method

    Alexander Rokash🇩🇪 · Michelle Pine🇺🇸 · Serdar Elhatisari🇩🇪 · Dean Lee🇺🇸 · Evgeny Epelbaum🇩🇪 · Hermann Krebs🇩🇪

    The adiabatic projection method is a general framework for studying scattering and reactions on the lattice. It provides a low-energy effective theory for clusters which becomes exact in the limit of large Euclidean projection time. Previous studies have used the adiabatic projection method to extract scattering phase shifts from finite periodic-box energy levels using Lüschers method. In this paper we demonstrate that scattering observables can be computed directly from asymptotic cluster wave functions. For a variety of examples in one and three spatial dimensions, we extract elastic phase shifts from asymptotic cluster standing waves corresponding to spherical wall boundary conditions. We find that this approach of extracting scattering wave functions from the adiabatic Hamiltonian to be less sensitive to small stochastic and systematic errors as compared with using periodic-box energy levels.

    nucl-thhep-latPRC(2015)·26 citations
  2. 02

    Viscosity and dissipative hydrodynamics from effective field theory

    Sašo Grozdanov🇬🇧 · Janos Polonyi🇫🇷

    With the goal of deriving dissipative hydrodynamics from an action, we study classical actions for open systems, which follow from the generic structure of effective actions in the Schwinger-Keldysh Closed-Time-Path formalism with two time axes and a doubling of degrees of freedom. The central structural feature of such effective actions is the coupling between degrees of freedom on the two time axes. This reflects the fact that from an effective field theory point of view, dissipation is the loss of energy of the low-energy hydrodynamical degrees of freedom to the integrated-out, UV degrees of freedom of the environment. The dynamics of only the hydrodynamical modes may therefore not posses a conserved stress-energy tensor. After a general discussion of the CTP effective actions, we use the variational principle to derive the energy-momentum balance equation for a dissipative fluid from an effective Goldstone action of the long-range hydrodynamical modes. Despite the absence of conserved energy and momentum, we show that we can construct the first-order dissipative stress-energy tensor and derive the Navier-Stokes equations near hydrodynamical equilibrium. The shear viscosity is shown to vanish in the classical theory under consideration, while the bulk viscosity is determined by the form of the effective action. We also discuss the thermodynamics of the system and analyse the entropy production.

    ↳ hep-thastro-ph.COhep-phnucl-th+1PRD(2015)·162 citations
  3. 03

    Directional detection of dark matter in universal bound states

    Ranjan Laha🇺🇸

    It has been suggested that several small-scale structure anomalies in CDM cosmology can be solved by strong self-interaction between dark matter particles. It was shown by Braaten and Hammer that the presence of a near threshold S-wave resonance can make the scattering cross section at nonrelativistic speeds come close to saturating the unitarity bound. This can result in the formation of a stable bound state of two asymmetric dark matter particles (we call the bound state as darkonium). Laha and Braaten studied the nuclear recoil energy spectrum in dark matter direct detection experiments due to this incident bound state. Here we study the angular recoil spectrum, and show that it is uniquely determined up to normalization by the S-wave scattering length. Observing this angular recoil spectrum in a dark matter directional detection experiment will uniquely determine many of the low-energy properties of dark matter independent of the underlying dark matter microphysics.

    ↳ hep-phastro-ph.COhep-exnucl-ex+1PRD(2015)·48 citations
  4. 04

    as a molecular state

    Takayasu Sekihara (RCNP, Osaka U.)🇯🇵

    We show that a pole can be dynamically generated near the threshold as an -wave molecular state in a coupled-channels unitary approach with the leading-order chiral interaction. This state can be identified with the resonance with . We find that the experimental and mass spectra are qualitatively reproduced with the state. Moreover we theoretically investigate properties of the dynamically generated state.

    ↳ hep-phhep-exhep-latnucl-ex+1PTEP(2015)·29 citations
  5. 05

    Quark properties from the Hadron Resonance Gas

    E. Ruiz Arriola🇪🇸 · L.L. Salcedo🇪🇸 · E. Megias🇩🇪

    We show how the quark free energy can be determined from a string and the Hadron Resonance Gas model with one heavy quark below the de-confinement phase transition. We discuss the interesting problem of identification of degrees of freedom at increasing temperatures, as well as the relevance of string breaking and avoided crossings.

    ↳ hep-phhep-latnucl-thActa Phys.Polon.Supp.(2015)·10 citations
  6. 06

    A General Analysis of Direct Dark Matter Detection: From Microphysics to Observational Signatures

    James B. Dent (1)🇺🇸 · Lawrence M. Krauss (2,3)🇺🇸 · Jayden L. Newstead (2)🇺🇸 · Subir Sabharwal (2) ((1) University of Louisiana at Lafayette, (2) Arizona State University, (3) Australian National University)🇺🇸

    Beginning with a set of simplified models for spin-0, spin-, and spin-1 dark matter candidates using completely general Lorentz invariant and renormalizable Lagrangians, we derive the full set of non-relativistic operators and nuclear matrix elements relevant for direct detection of dark matter, and use these to calculate rates and recoil spectra for scattering on various target nuclei. This allows us to explore what high energy physics constraints might be obtainable from direct detection experiments, what degeneracies exist, which operators are ubiquitous and which are unlikely or sub-dominant. We find that there are operators which are common to all spins as well operators which are unique to spin- and spin-1 and elucidate two new operators which have not been previously considered. In addition we demonstrate how recoil energy spectra can distinguish fundamental microphysics if multiple target nuclei are used. Our work provides a complete roadmap for taking generic fundamental dark matter theories and calculating rates in direct detection experiments. This provides a useful guide for experimentalists designing experiments and theorists developing new dark matter models.

    ↳ hep-phastro-ph.COhep-exnucl-ex+1PRD(2015)·106 citations

Affiliations

first authorsco-authorsvia INSPIRE