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Nuclear Theory·nucl-th

Tuesday·March 1, 2016

14 papers—7 primary·7 cross-listed

All14Primary7Cross-lists7
  1. 08

    [Submitted on 28 Feb 2016] (cross-list from cond-mat.str-el)

    Effective field theory and the scattering process for magnons in the ferromagnet, antiferromagnet, and ferrimagnet

    Shinya Gongyo🇯🇵 · Yuta Kikuchi🇯🇵 · Tetsuo Hyodo🇯🇵 · Teiji Kunihiro🇯🇵

    We discuss that a low-energy effective Lagrangian relying on SO(3) SO(2) is applicable for a ferrimagnet as well as a ferromagnet and an antiferromagnet. The analysis of the particle states shows that there exist not only massless modes with the dispersion relations , i.e., the so-called type-I and type-II Nambu-Goldstone modes, respectively, but also gapped modes with . We clarify how the coefficients of the terms with one time derivative and those with two time derivatives in the effective Lagrangian determine the order parameters specifying whether the system is in a ferromagnetic, antiferromagnetic or ferrimagnetic state; we stress that the gapped mode related to the spontaneous symmetry breaking appears only in the ferrimagnetic system and not in the ferromagnetic and antiferromagnetic systems. We also establish the power counting scheme and calculate the scattering amplitudes and thereby the scattering lengths between the two Nambu-Goldstone bosons. We show that the scattering length of the gapped mode is finite and proportional to the gap. This characteristic property of the gapped NG mode can be used to discriminate it from gapped excitations which originate in other mechanisms. Finally, we study the effects of the explicit symmetry breaking that are given by an external magnetic field and a single-ion anisotropy, and show that the external magnetic fields do not have any effects on the scattering amplitudes in all the spin systems as was known for the ferromagnet system. In contrast, the anisotropy does affect the scattering amplitudes, the phase shift, and the scattering length except for spin 1/2 systems. This result supports the possibility of the Efimov effect in spin systems discussed in previous studies.

    Comments:
    26pages, 0 figures; published in Progress of Theoretical and Experimental Physics (PTEP)
    Subjects:
    Strongly Correlated Electrons (cond-mat.str-el); cond-mat.other (cond-mat.other); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1602.08692 [pdf]
    PTEP(2016)·8 citations
  2. 09

    [Submitted on 28 Feb 2016] (cross-list from hep-lat)

    Parton distribution functions from Lattice QCD

    Constantia Alexandrou (Univ. of Cyprus & The Cyprus Inst.)🇨🇾

    We present recent results on the first moments of parton distributions using gauge configurations generated with two degenerate flavors of light twisted mass quarks with pion mass fixed approximately to its physical value. We also present a first study of the vector parton distribution function using a twisted mass ensemble at pion mass of 373 MeV.

    Comments:
    Invited talk at the Light Cone 2015 conference, INFN National Laboratories, Frascati, Italy, 21-25 Sept. 2015. 6 pages, 5 Figures
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1602.08726 [pdf]
    Few Body Syst.(2016)·11 citations
  3. 10

    [Submitted on 29 Feb 2016] (cross-list from hep-ph)

    Can be a tetraquark state?

    Wei Wang🇨🇳 · Ruilin Zhu🇨🇳

    Very recently, the D0 collaboration has reported the observation of a narrow structure, , in the decay process using the 10.4 data of collision at TeV. This structure is of great interest since it is the first hadronic state with four different valence quark flavors, . In this work, we investigate tetraquarks with four different quark flavors. Based on the diquark-antidiquark scheme, we study the spectroscopy of the tetraquarks with one heavy bottom/charm quark and three light quarks. We find that the lowest-lying S-wave state, a tetraquark with the flavor and the spin-parity , is about 150 MeV higher than the . Further detailed experimental and theoretical studies of the spectrum, production and decays of tetraquark states with four different flavors in the future are severely needed towards a better understanding its nature and the classification of hadron exotic states.

    Comments:
    5 pages,1 figure and 1 table;To be published on Chin.Phys.C
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1602.08806 [pdf]
    CPC(2016)·66 citations
  4. 11

    [Submitted on 29 Feb 2016] (cross-list from hep-ph)

    Antikaon-nucleon interaction and Lambda(1405) in chiral SU(3) dynamics

    Yuki Kamiya🇯🇵 · Kenta Miyahara🇯🇵 · Shota Ohnishi🇯🇵 · Yoichi Ikeda🇯🇵 · Tetsuo Hyodo🇯🇵 · Eulogio Oset🇪🇸 · Wolfram Weise🇩🇪

    The properties of the Lambda(1405) resonance are key ingredients for determining the antikaon-nucleon interaction in strangeness nuclear physics, and the novel internal structure of the Lambda(1405) is of great interest in hadron physics, as a prototype case of a baryon that does not fit into the simple three-quark picture. We show that a quantitative description of the antikaon-nucleon interaction with the Lambda(1405) is achieved in the framework of chiral SU(3) dynamics, with the help of recent experimental progress. Further constraints on the Kbar N subthreshold interaction are provided by analyzing pi Sigma spectra in various processes, such as the K-d -> pi Sigma n reaction and the Lambda_c -> pi pi Sigma decay. The structure of the Lambda(1405) is found to be dominated by an antikaon-nucleon molecular configuration, based on its wavefunction derived from a realistic Kbar N potential and the compositeness criteria from a model-independent weak-binding relation.

    Comments:
    27 pages, 9 figures. Prepared for Nuclear Physics A Special Issue on recent progress in Strangeness and Charm Nuclear Physics
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1602.08852 [pdf]
    NPA(2016)·78 citations
  5. 12

    [Submitted on 29 Feb 2016] (cross-list from hep-ph)

    Quark Matter in a Parallel Electric and Magnetic Field Background: Chiral Phase Transition and Equilibration of Chiral Density

    M. Ruggieri🇨🇳 · G. X. Peng🇨🇳

    In this article we study spontaneous chiral symmetry breaking for quark matter in the background of static and homogeneous parallel electric field and magnetic field . We use a Nambu-Jona-Lasinio model with a local kernel interaction to compute the relevant quantities to describe chiral symmetry breaking at finite temperature for a wide range of and . We study the effect of this background on inverse catalysis of chiral symmetry breaking for and of the same order of magnitude. We then focus on the effect of equilibration of chiral density, , produced dynamically by axial anomaly on the critical temperature. The equilibration of , a consequence of chirality flipping processes in the thermal bath, allows for the introduction of the chiral chemical potential, , which is computed self-consistently as a function of temperature and field strength by coupling the number equation to the gap equation, and solving the two within an expansion in , and . We find that even if chirality is produced and equilibrates within a relaxation time , it does not change drastically the thermodynamics, with particular reference to the inverse catalysis induced by the external fields, as long as the average at equilibrium is not too large.

    Comments:
    12 pages, 10 figures. Matches the published version
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    1602.08994 [pdf]
    PRD(2016)·56 citations
  6. 13

    [Submitted on 29 Feb 2016] (cross-list from hep-ph)

    Phi meson spectral moments and QCD condensates in nuclear matter

    Philipp Gubler🇮🇹 · Wolfram Weise🇩🇪

    A detailed analysis of the lowest two moments of the meson spectral function in vacuum and nuclear matter is performed. The consistency is examined between the constraints derived from finite energy QCD sum rules and the spectra computed within an improved vector dominance model, incorporating the coupling of kanonic degrees of freedom with the bare meson. In the vacuum, recent accurate measurements of the cross section allow us to determine the spectral function with high precision. In nuclear matter, the modification of the spectral function can be described by the interactions of the kaons from with the surrounding nuclear medium. This leads primarily to a strong broadening and an asymmetric deformation of the meson peak structure. We confirm that, both in vacuum and nuclear matter, the zeroth and first moments of the corresponding spectral functions satisfy the requirements of the finite energy sum rules to a remarkable degree of accuracy. Limits on the strangeness sigma term of the nucleon are examined in this context. Applying our results to the second moment of the spectrum, we furthermore discuss constraints on four-quark condensates and the validity of the commonly used ground state saturation approximation.

    Comments:
    20 pages, 11 figures; published version. arXiv admin note: text overlap with arXiv:1507.03769
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1602.09126 [pdf]
    NPA(2016)·38 citations
  7. 14

    [Submitted on 29 Feb 2016] (cross-list from nucl-ex)

    Experimental overview on small collision systems at the LHC

    Constantin Loizides🇺🇸

    These conferences proceedings summarize the experimental findings obtained in small collision systems at the LHC, as presented in the special session on "QGP in small systems?" at the Quark Matter 2015 conference. (The arXiv version is significantly longer than the printed proceedings, with more details and a short discussion.)

    Comments:
    17 pages, 3 captioned figures, 1 table, extended version of Quark Matter 2015 proceedings
    Subjects:
    Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1602.09138 [pdf]
    NPA(2016)·145 citations

Affiliations

first authorsco-authorsvia INSPIRE