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Nuclear Theory·nucl-th

Thursday·March 26, 2015

13 papers—6 primary·7 cross-listed

All13Primary6Cross-lists7
  1. 07

    Tetraquark Cusp Effects from Diquark Pair Production

    Samuel H. Blitz🇺🇸 · Richard F. Lebed🇺🇸

    We present the first study of the cusp effect (the movement of resonant poles due to the proximity of multiparticle thresholds) caused by the creation of diquark-antidiquark pairs. The cusp profile for such states is obtained from constituent counting rules. We compare the effectiveness of diquark cusps in moving resonant poles with that from a phenomenological form commonly used for meson-pair creation, and find that mesons tend to be more effective at lower energies , the threshold), while diquarks tend to be more effective at the charm [] scales and above.

    ↳ hep-phnucl-thPRD(2015)·29 citations
  2. 08

    Revisiting Scalar Glueballs

    Hai-Yang Cheng🇹🇼 · Chun-Khiang Chua🇹🇼 · Keh-Fei Liu🇺🇸

    It is commonly believed that the lowest-lying scalar glueball lies somewhere in the isosinglet scalar mesons and denoted generically by . In this work we consider lattice calculations and experimental data to infer the glue and components of . These include the calculations of the scalar glueball masses in quenched and unquenched lattice QCD, measurements of the radiative decays , the ratio of decays to and , the ratio of decays to and , the contributions to , and the near mass degeneracy of and . All analyses suggest the prominent glueball nature of and the flavor octet structure of .

    ↳ hep-phhep-exhep-latnucl-thPRD(2015)·56 citations
  3. 09

    Bosonic and fermionic Weinberg-Joos (j,0)+ (0,j) states of arbitrary spins as Lorentz-tensors or tensor-spinors and second order theory

    E. G. Delgado Acosta🇲🇽 · V.M. Banda Guzman🇲🇽 · M. Kirchbach🇲🇽

    We propose a general method for the description of arbitrary single spin-j states transforming according to (j,0)+(0,j) carrier spaces of the Lorentz algebra in terms of Lorentz-tensors for bosons, and tensor-spinors for fermions, and by means of second order Lagrangians. The method allows to avoid the cumbersome matrix calculus and higher \partial^{2j} order wave equations inherent to the Weinberg-Joos approach. We start with reducible Lorentz-tensor (tensor-spinor) representation spaces hosting one sole (j,0)+(0,j) irreducible sector and design there a representation reduction algorithm based on one of the Casimir invariants of the Lorentz algebra. This algorithm allows us to separate neatly the pure spin-j sector of interest from the rest, while preserving the separate Lorentz- and Dirac indexes. However, the Lorentz invariants are momentum independent and do not provide wave equations. Genuine wave equations are obtained by conditioning the Lorentz-tensors under consideration to satisfy the Klein-Gordon equation. In so doing, one always ends up with wave equations and associated Lagrangians that are second order in the momenta. Specifically, a spin-3/2 particle transforming as (3/2,0)+ (0,3/2) is comfortably described by a second order Lagrangian in the basis of the totally antisymmetric Lorentz tensor-spinor of second rank, \Psi_[ \mu\nu]. Moreover, the particle is shown to propagate causally within an electromagnetic background. In our study of (3/2,0)+(0,3/2) as part of \Psi_[\mu\nu] we reproduce the electromagnetic multipole moments known from the Weinberg-Joos theory. We also find a Compton differential cross section that satisfies unitarity in forward direction. The suggested tensor calculus presents itself very computer friendly with respect to the symbolic software FeynCalc.

    ↳ hep-phnucl-thEPJA(2015)·22 citations
  4. 10

    Gluon Transport Equation with Effective Mass and Dynamical Onset of Bose-Einstein Condensation

    Jean-Paul Blaizot🇫🇷 · Yin Jiang🇺🇸 · Jinfeng Liao🇺🇸

    We study the transport equation describing a dense system of gluons, in the small scattering angle approximation, taking into account medium-generated effective masses of the gluons. We focus on the case of overpopulated systems that are driven to Bose-Einstein condensation on their way to thermalization. The presence of a mass modifies the dispersion relation of the gluon, as compared to the massless case, but it is shown that this does not change qualitatively the scaling behavior in the vicinity of the onset.

    ↳ hep-phcond-mat.quant-gashep-thnucl-thNPA(2016)·11 citations
  6. 12

    Optimising the neutron environment of Radiation Portal Monitors: a computational optimisation study

    Mark R. Gilbert · Zamir Ghani · Lee W. Packer

    Efficient and reliable detection of radiological or nuclear threats is a crucial part of national and international efforts to prevent terrorist activities. Radiation Portal Monitors (RPMs), which are deployed worldwide, are intended to interdict smuggled fissile material by detecting emissions of neutrons and gamma rays. However, considering the range and variety of threat sources, vehicular and shielding scenarios, and that only a small signature is present, it is important that the design of the RPMs allows these signatures to be accurately differentiated from the environmental background. Using Monte-Carlo neutron-transport simulations of a model helium-3 detector system we have conducted a parameter study to identify the optimum combination of detector shielding and collimation that maximises the sensitivity of RPMs. These structures, which could be simply and cost-effectively added to existing RPMs, can improve the detector response by more than a factor of two relative to an unmodified, bare design. Furthermore, optimisation of the air gap surrounding the helium tubes also improves detector efficiency.

    ↳ physics.ins-detnucl-thNucl.Instrum.Meth.A(2015)·2 citations
  7. 13

    Hydrodynamics Beyond the Gradient Expansion: Resurgence and Resummation

    Michal P. Heller🇨🇦 · Michal Spalinski🇵🇱

    Consistent formulations of relativistic viscous hydrodynamics involve short lived modes, leading to asymptotic rather than convergent gradient expansions. In this Letter we consider the Mueller-Israel-Stewart theory applied to a longitudinally expanding quark-gluon plasma system and identify hydrodynamics as a universal attractor without invoking the gradient expansion. We give strong evidence for the existence of this attractor and then show that it can be recovered from the divergent gradient expansion by Borel summation. This requires careful accounting for the short-lived modes which leads to an intricate mathematical structure known from the theory of resurgence.

    ↳ hep-thhep-phnucl-thphysics.flu-dynPRL(2015)·374 citations

Affiliations

first authorsco-authorsvia INSPIRE