Nuclear Theory·nucl-th

Friday·October 27, 2017

11 papers—7 primary·4 cross-listed

01
Decoding the phase structure of QCD via particle production at high energy
A. Andronic🇩🇪 · P. Braun-Munzinger🇨🇳 · K. Redlich🇩🇪 · J. Stachel🇩🇪
Recent studies based on non-perturbative lattice Monte-Carlo solutions of Quantum Chromodynamics, the theory of strong interactions, demonstrated that at high temperature there is a phase change from confined hadronic matter to a deconfined quark-gluon plasma where quarks and gluons can travel distances largely exceeding the size of hadrons. The phase structure of such strongly interacting matter can be decoded via analysis of particle abundances in high energy nuclear collisions within the framework of the statistical hadronization approach. The results imply quark-hadron duality at and experimental delineation of the location of the phase boundary of strongly interacting matter.
nucl-thNature(2018)·1002 citations
02
12C within the Semimicroscopic Algebraic Cluster Model
P. O. Hess
The Semimicroscopic Algebraic Cluster Model (SACM) is applied to 12C as a system of three alpha- clusters. The microscopic model space, which observes the Pauli-Exclusion-Principle (PEP), is constructed. It is shown that the 12C nucleus can effectively be treated as a two-cluster system 8Be+alpha. The experimental spectrum is well reproduced. The geometrical mapping is discussed and it is shown that the ground state must correspond to a triangular structure, which is in agreement with other microscopic calculations. The non-zero B(E2; 0_2+ --> 2_1+) transition requires a mixing of SU(3) irreducible representations (irreps) whose consequences are discussed. The Hoyle state turns out to contain large shell excitations. The results are compared to another phenomenological model, which assumes a triangular structure and, using simple symmetry arguments, can reproduce the states observed at low energy. This model does not observe the PEP and one objective of our contribution is to verify the extend of importance of the PEP.
nucl-thEPJA(2018)·14 citations
03
Influence of final-state radiation on heavy-flavour observables in pp collisions
L. Vermunt🇳🇱 · J. Aichelin🇫🇷 · P.B. Gossiaux🇫🇷 · K. Werner🇫🇷 · A. Mischke🇳🇱 · B. Guiot🇨🇱 · M. Nahrgang🇫🇷 · T. Pierog🇩🇪
The influence of final-state radiation (FSR) of heavy quarks on observables in high-energy proton-proton collisions is studied. The transverse momentum correlation of D and Dbar mesons, which have been emitted with an azimuthal difference angle close to 180 degrees, is identified as an observable which is sensitive to the FSR process. We demonstrate this by performing calculations with the EPOS3+HQ model and with the event generator Pythia 6. The initial symmetric pT = pT' correlation for back-to-back pairs does not completely vanish in EPOS3+HQ, neither for the final DDbar pairs nor for the ccbar pairs before hadronisation. Also a significant difference in the shape of the correlation distribution for EPOS3+HQ and Pythia 6 is observed. Therefore, particle correlations in pp data offer the possibility to study several aspects of energy loss in heavy-ion collisions.
nucl-thhep-ph3 citations
04
Comparing standard distribution and its Tsallis form of transverse momenta in high energy collisions
Rui-Fang Si🇨🇳 · Hui-Ling Li🇨🇳 · Fu-Hu Liu🇨🇳
In this paper, the experimental (simulated) transverse momentum spectra of negatively charged pions produced at mid-rapidity in central nucleus-nucleus collisions at the Heavy Ion Synchrotron (SIS), Relativistic Heavy Ion Collider (RHIC), and Large Hadron Collider (LHC) energies obtained by different collaborations are selected by us to investigate, where a few simulated data are taken from the results of FOPI Collaboration who uses the IQMD transport code based on Quantum Molecular Dynamics. A two-component standard distribution and the Tsallis form of standard distribution are used to fit these data in the framework of a multisource thermal model. The excitation functions of main parameters in the two distributions are analyzed. In particular, the effective temperatures extracted from the two-component standard distribution and the Tsallis form of standard distribution are obtained, and the relation between the two types of effective temperatures is studied.
nucl-thhep-exhep-phnucl-exAdv.High Energy Phys.(2018)·13 citations
05
Inelastic shadowing of secondary pi+-, K+-, p, and bar(p) produced in p+Pb collisions at LHC energy
G.H. Arakelyan🇦🇲 · C. Merino🇪🇸 · Yu.M. Shabelski🇷🇺 · A.G. Shuvaev🇷🇺
The inclusive spectra of secondaries produced in soft (minimum-bias) p+Pb collisions at LHC energy are calculated in the frame of the Quark-Gluon String Model, by including the inelastic screening corrections (percolation effects). These effects are expected to be quite large at the very high energies, and they should drive down the spectra in the midrapidity region more than 2 times, at sqrt(sNN)=5 TeV.
nucl-thhep-ph0 citations
06
Study of Lambda polarization at RHIC BES and LHC energies
Iurii Karpenko🇮🇹 · Francesco Becattini🇮🇹
In hydrodynamic approach to relativistic heavy ion collisions, hadrons with nonzero spin, produced out of the hydrodynamic medium, can acquire polarization via spin-vorticity thermodynamic coupling mechanism. The hydrodynamical quantity steering the polarization is the thermal vorticity, that is minus the antisymmetric part of the gradient of four-temperature field. Based on this mechanism there have been several calculations in hydrodynamic and non-hydrodynamic models for non-central heavy ion collisions in the RHIC Beam Energy Scan energy range, showing that the amount of polarization of produced $Λ$ hyperons ranges from few percents to few permille, and decreases with collision energy. We report on an extension of our existing calculation of global $Λ$ polarization in UrQMD+vHLLE model to full RHIC and LHC energies, and discuss the component of polarization along the beam direction, which is the dominant one at high energies.
nucl-thhep-phnucl-exEPJ Web Conf.(2018)·5 citations
07
Electromagnetic reactions from coupled-cluster theory
Sonia Bacca · Mirko Miorelli · Gaute Hagen
We review recent results for electromagnetic reactions and related sum rules in light and medium-mass nuclei obtained from coupled-cluster theory. In particular, we highlight our recent computations of the photodisintegration cross section of 40Ca and of the electric dipole polarizability for oxygen and calcium isotopes. We also provide new results for the Coulomb sum rule for 4He and 16O. For 4He we perform a thorough comparison of coupled-cluster theory with exact hyperspherical harmonics.
nucl-thJ.Phys.Conf.Ser.(2018)·5 citations
08
Dawning of the N=32 shell closure seen through precision mass measurements of neutron-rich titanium isotopes
E. Leistenschneider🇨🇦 · M.P. Reiter🇨🇦 · S. Ayet San Andrés🇩🇪 · B. Kootte🇨🇦 · J.D. Holt🇨🇦 · P. Navrátil🇨🇦 · C. Babcock🇨🇦 · C. Barbieri🇬🇧 · B.R. Barquest🇨🇦 · J. Bergmann🇩🇪 · J. Bollig🇨🇦 · T. Brunner🇨🇦 and 33 other authors
A precision mass investigation of the neutron-rich titanium isotopes $^{51 - 55}$ Ti was performed at TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN). The range of the measurements covers the $N = 32$ shell closure and the overall uncertainties of the $^{52 - 55}$ Ti mass values were significantly reduced. Our results confirm the existence of a weak shell effect at $N = 32$ , establishing the abrupt onset of this shell closure. Our data were compared with state-of-the-art \textit{ab-initio} shell model calculations which, despite very successfully describing where the $N = 32$ shell gap is strong, overpredict its strength and extent in titanium and heavier isotones. These measurements also represent the first scientific results of TITAN using the newly commissioned Multiple-Reflection Time-of-Flight Mass Spectrometer (MR-TOF-MS), substantiated by independent measurements from TITAN's Penning trap mass spectrometer.
↳ nucl-exnucl-thPRL(2018)·117 citations
09
Phenomenology of neutron-antineutron conversion
Susan Gardner🇺🇸 · Xinshuai Yan🇺🇸
We consider the possibility of neutron-antineutron ( $n - n ˉ$ ) conversion, in which the change of a neutron into an antineutron is mediated by an external source, as can occur in a scattering process. We develop the connections between $n - n ˉ$ conversion and $n - n ˉ$ oscillation, in which a neutron spontaneously tranforms into an antineutron, noting that if $n - n ˉ$ oscillation occurs in a theory with B-L violation, then $n - n ˉ$ conversion can occur also. We show how an experimental limit on $n - n ˉ$ conversion could connect concretely to a limit on $n - n ˉ$ oscillation, and vice versa, using effective field theory techniques and baryon matrix elements computed in the M.I.T. bag model.
↳ hep-phhep-exnucl-exnucl-thPRD(2018)·15 citations
10
Melting and freeze-out conditions of hadrons in a thermal medium
Juan M. Torres-Rincon🇩🇪 · Joerg Aichelin🇩🇪 · Hannah Petersen🇩🇪 · Jean-Bernard Rose🇩🇪 · Joseph Tindall🇬🇧
We describe two independent frameworks which provide unambiguous determinations of the deconfinement and the decoupling conditions of a relativistic gas at finite temperature. First, we use the Polyakov-Nambu-Jona-Lasinio model to compute meson and baryon masses at finite temperature and determine their melting temperature as a function of their strangeness content. Second, we analyze a simple expanding gas within a Friedmann-Robertson-Walker metric, which admits a well-defined decoupling mechanism. We examine the decoupling time as a function of the particle mass and cross section. We find evidences of an inherent dependence of the hadronization and freeze-out conditions on flavor, and on mass and cross section, respectively.
↳ hep-phnucl-thEPJ Web Conf.(2018)·0 citations
11
Collectivity without plasma in hadronic collisions
Christian Bierlich🇸🇪 · Gösta Gustafson🇸🇪 · Leif Lönnblad🇸🇪
We present a microscopic model for collective effects in high multiplicity proton--proton collisions, where multiple partonic subcollisions give rise to a dense system of strings. From lattice calculations we know that QCD strings are transversely extended, and we argue that this should result in a transverse pressure and expansion, similar to the flow in a deconfined plasma. The model is implemented in the PYTHIA8 Monte Carlo event generator, and we find that it can qualitatively reproduce the long range azimuthal correlations forming a near-side ridge in high multiplicity proton--proton events at LHC energies.
↳ hep-phnucl-thPLB(2018)·132 citations

Affiliations

first authorsco-authorsvia INSPIRE