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Nuclear Theory·nucl-th

Friday·May 5, 2017

8 papers—4 primary·4 cross-listed

All8Primary4Cross-lists4
  1. 05

    Validity of the Weizsäcker-Williams Approximation and the Analysis of Beam Dump Experiments: Production of an axion, a dark photon, or a new axial-vector boson

    Yu-Sheng Liu🇺🇸 · Gerald A. Miller🇺🇸

    Beam dump experiments have been used to search for new particles, , with null results interpreted in terms of limits on masses and coupling constants . However these limits have been obtained by using approximations [including the Weizsäcker-Williams (WW) approximation] or Monte-Carlo simulations. We display methods to obtain the cross section and the resulting particle production rates without using approximations on the phase space integral or Monte-Carlo simulations. In our previous work we examined the case of the new scalar boson production; in this paper we explore all possible new spin-0 and spin-1 particles. We show that the approximations cannot be used to obtain accurate values of cross sections. The corresponding exclusion plots differ by substantial amounts when seen on a linear scale. Furthermore, a new region () of parameter space can be explored without using one of the common approximations, . We derive new expressions for the three photon decays of dark photon and four photon decays of new axial-vector bosons. As a result, the production cross section and exclusion region of different low mass () bosons are very different. Moreover, our method can be used as a consistency check for Monte-Carlo simulations.

    ↳ hep-phhep-exnucl-exnucl-thPRD(2017)·111 citations
  2. 06

    Chiral vortical effect in pionic superfluid vs spin alignment of baryons

    Oleg V. Teryaev🇷🇺 · Valentin I. Zakharov🇷🇺

    We consider chiral fluids, with (nearly) massless fermionic constituents, in the confining phase. Chiral vortical effect (CVE) is the flow of axial current along the axis of rotation of the fluid while the spin alignment is a non-vanishing correlation of polarizations of baryons with the axis of rotation. As the theoretical framework we use the model of pionic superfluidity induced by a non-vanishing isotopic chemical potential. We note that the average value of spin of virtual baryons reproduces the CVE. The role of defects, or vortices is crucial. The model does not apply directly to the quark-gluon plasma but might indicate existence of a mechanism to produce baryons with relatively large polarization in heavy-ion collisions.

    ↳ hep-thhep-phnucl-th7 citations
  3. 07

    Exact self-duality in a modified Skyrme model

    L. A. Ferreira🇧🇷

    We propose a modification of the Skyrme model that supports a self-dual sector possessing exact non-trivial finite energy solutions. The action of such a theory possesses the usual quadratic and quartic terms in field derivatives, but the couplings of the components of the Maurer-Cartan form of the Skyrme model is made by a non-constant symmetric matrix, instead of the usual Killing form of the SU(2) Lie algebra. The introduction of such a matrix make the self-duality equations conformally invariant in three space dimensions, even though it may break the global internal symmetries of the original Skyrme model. For the case where that matrix is proportional to the identity we show that the theory possesses exact self-dual Skyrmions of unity topological charges.

    ↳ hep-thmath-phmath.MPnlin.SI+1JHEP(2017)·26 citations
  4. 08

    A novel multiquark approach to hadron resonances

    S. S. Afonin🇷🇺

    A new approach to description of hadron spectroscopy is proposed. By assumption, the form of spectrum is dictated by the trace of energy momentum tensor in QCD. This provides the relativistic and renormalization invariance of hadron masses. The constructed scheme is applied to the light mesons for which two complementary interpretations are worked out. The first one represents an "atomic" structure of resonances above 1 GeV in which the quanta of non-perturbative gluon contributions are quantified via an effective formation of quasiparticles representing likely gluon analogues of positronium. This picture allows to build a "periodic table of the hadronic elements", i.e. to classify hadrons, in some sense, in analogy with Mendeleev table in chemistry. The classification does not require introduction of the orbital angular momentum associated with hadron constituents. The Regge and radial trajectories emerge in a natural way. The second interpretation is based on a "collisional" nature of some (or many) hadrons, specifically of scalar resonances below 1 GeV. Here the role of quasiparticles is played by another hadron. This picture in particular leads to a simple explanation of the puzzling scalar sector below 1 GeV with correct predictions for masses and dominant decay modes.

    ↳ hep-phhep-latnucl-th1 citation

Affiliations

first authorsco-authorsvia INSPIRE