Nuclear Theory·nucl-th
17 papers—9 primary·8 cross-listed
[Submitted on 13 Jul 2016] (cross-list from physics.hist-ph)
Dmitri Ivanenko, professor of Moscow State University, was one of the great theoreticians of XX century, an author of the proton-neutron model of atomic nucleus. In honor of the 110th Year Anniversary.
[Submitted on 13 Jul 2016] (cross-list from astro-ph.CO)
Ryan Cooke (1) · Max Pettini (2,3) · Kenneth M. Nollett (4) · Regina Jorgenson (5,6) · ((1) University of California, Santa Cruz, (2) Institute of Astronomy, University of Cambridge, (3) Kavli Institute for Cosmology, University of Cambridge, (4) San Diego State University, (5) Willamette University, (6) Maria Mitchell Observatory)
We report the discovery and analysis of the most metal-poor damped Lyman-alpha (DLA) system currently known, which also displays the Lyman series absorption lines of neutral deuterium. The average [O/H] abundance of this system is [O/H] = -2.804 +/- 0.015, which includes an absorption component with [O/H] = -3.07 +/- 0.03. Despite the unfortunate blending of many weak D I absorption lines, we report a precise measurement of the deuterium abundance of this system. Using the six highest quality and self-consistently analyzed measures of D/H in DLAs, we report tentative evidence for a subtle decrease of D/H with increasing metallicity. This trend must be confirmed with future high precision D/H measurements spanning a range of metallicity. A weighted mean of these six independent measures provides our best estimate of the primordial abundance of deuterium, 10^5 (D/H)_P = 2.547 +/- 0.033 (log_10 (D/H)_P = -4.5940 +/- 0.0056). We perform a series of detailed Monte Carlo calculations of Big Bang nucleosynthesis (BBN) that incorporate the latest determinations of several key nuclear cross sections, and propagate their associated uncertainty. Combining our measurement of (D/H)_P with these BBN calculations yields an estimate of the cosmic baryon density, 100 Omega_B,0 h^2(BBN) = 2.156 +/- 0.020, if we adopt the most recent theoretical determination of the d(p,gamma)3He reaction rate. This measure of Omega_B,0 h^2 differs by ~2.3 sigma from the Standard Model value estimated from the Planck observations of the cosmic microwave background. Using instead a d(p,gamma)3He reaction rate that is based on the best available experimental cross section data, we estimate 100 Omega_B,0 h^2(BBN) = 2.260 +/- 0.034, which is in somewhat better agreement with the Planck value. Forthcoming measurements of the crucial d(p,gamma)3He cross section may shed further light on this discrepancy.
[Submitted on 14 Jul 2016] (cross-list from hep-ph)
A general consensus now is that there are two physically inequivalent complete decompositions of the nucleon spin, i.e. the decomposition of the canonical type and that of mechanical type. The well-known Jaffe-Manohar decomposition is of the former type. Unfortunately, there is a wide-spread misbelief that this decomposition matches the partonic picture, which states that motion of quarks in the nucleon is approximately free. In the present monograph, we reveal that this understanding is not necessarily correct and that the Jaffe-Manohar decomposition is not such a decomposition, which natively reflects the intrinsic (or static) orbital angular momentum structure of the nucleon.
[Submitted on 14 Jul 2016] (cross-list from hep-ph)
E.R. Cazaroto🇧🇷 · V.P. Goncalves🇸🇪 · F.S. Navarra🇧🇷
In this paper we estimate the double parton scattering (DPS) contribution for the heavy quark production in collisions at the LHC. The cross sections for the charm and bottom production are estimated using the dipole approach and taking into account the saturation effects, which are important for high energies and for the scattering with a large nucleus. We compare the DPS contribution with the single parton scattering one and demonstrate that in the case of charm production both are similar in the kinematical range probed by the LHC. Predictions for the rapidity range analysed by the LHCb Collaboration are also presented. Our results indicate that the study of the DPS contribution for the heavy quark production in collisions at the LHC is feasible and can be useful to probe the main assumptions of the approach.
[Submitted on 14 Jul 2016] (cross-list from hep-lat)
Yannis Burnier🇨🇭 · Alexander Rothkopf🇩🇪
We improve and extend our study of the complex in-medium heavy quark potential and its Debye mass in a gluonic medium with a finer scan around the deconfinement transition and newly generated ensembles closer to the thermodynamic limit. On the lattices with larger physical volume, Re[V] shows signs of screening, i.e. a finite , only in the deconfined phase, reminiscent of a genuine phase transition. Consistently Im[V] exhibits nonzero values also only above . We compare the behavior of Re[V] with the color singlet free-energies that have been used historically to extract the Debye mass. An effective coupling constant is computed to assess the residual influence of the confining part of the potential at . Our previous finding of a gradual screening of Re[V] around on finer lattices is critically reassessed and interpreted to originate from finite volume artifacts that affect the deployed , parameter set at .
[Submitted on 14 Jul 2016] (cross-list from hep-ph)
Yasuhiro Yamaguchi🇯🇵 · Tetsuo Hyodo🇯🇵
We study the quark mass dependence of the H-dibaryon in the strangeness baryon-baryon scattering. A low-energy effective field theory is used to describe the coupled-channel scattering, in which the quark mass dependence is incorporated so as to reproduce the lattice QCD data by the HAL QCD collaboration in the SU(3) limit. We point out the existence of the Castillejo-Dalitz-Dyson (CDD) pole in the scattering amplitude below the threshold in the SU(3) limit, which may cause the Ramsauer-Townsend effect near the threshold at the physical point. The H-dibaryon is unbound at the physical point, and a resonance appears just below the threshold. As a consequence of the coupled-channel dynamics, the pole associated with the resonance is not continuously connected to the bound state in the SU(3) limit. Through the extrapolation in quark masses, we show that the unitary limit of the scattering is achieved between the physical point and the SU(3) limit. We discuss the possible realization of the "H-matter" in the unphysical quark mass region.
[Submitted on 14 Jul 2016] (cross-list from hep-th)
Fabrizio Canfora🇨🇱 · Gianni Tallarita🇨🇱
We analyze the mechanism of condensation of orientational moduli (as introduced in [25]) on multi-Skyrmionic configurations of the four-dimensional Skyrme model. The present analysis reveals interesting novel features. First of all, the orientational moduli tend to decrease the repulsive interactions between Skyrmions, the effect decreasing with the increase of the Baryon number. Moreover, in the case of a single Skyrmion, the appearance of moduli is energetically favorable if finite volume effects are present. Otherwise, in the usual flat topologically trivial case, it is not. In the low energy theory these solutions can be interpreted as Skyrmions with additional isospin degrees of freedom.
[Submitted on 14 Jul 2016] (cross-list from hep-ph)
Saturation and geometrical scaling (GS) of gluon distributions are a consequence of the non-linear evolution equations of QCD. We argue that in pp GS holds for the inelastic cross-section rather than for the multiplicity distributions. We also discuss possible fluctuations of the proton saturation scale in pA collisions at the LHC.
first authorsco-authorsvia INSPIRE