Nuclear Theory·nucl-th

Monday·December 25, 2017

9 papers—1 primary·8 cross-listed

02
[Submitted on 21 Dec 2017] (cross-list from hep-lat)
QCD phase diagram for nonzero isospin-asymmetry
B. B. Brandt🇩🇪 · G. Endrodi🇩🇪 · S. Schmalzbauer🇩🇪
The QCD phase diagram is studied in the presence of an isospin asymmetry using continuum extrapolated staggered quarks with physical masses. In particular, we investigate the phase boundary between the normal and the pion condensation phases and the chiral/deconfinement transition. The simulations are performed with a small explicit breaking parameter in order to avoid the accumulation of zero modes and thereby stabilize the algorithm. The limit of vanishing explicit breaking is obtained by means of an extrapolation, which is facilitated by a novel improvement program employing the singular value representation of the Dirac operator. Our findings indicate that no pion condensation takes place above $T \approx 160$ MeV and also suggest that the deconfinement crossover continuously connects to the BEC-BCS crossover at high isospin asymmetries. The results may be directly compared to effective theories and model approaches to QCD.
Comments:
17 pages, 14 figures; v2: to match published version, corrected typos and updated references
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1712.08190 [pdf]
PRD(2018)·210 citations
03
[Submitted on 21 Dec 2017] (cross-list from astro-ph.HE)
Core-Collapse Supernova Simulations including Neutrino Interactions from the Virial EOS
Evan O'Connor🇸🇪 · C.J. Horowitz🇺🇸 · Zidu Lin🇺🇸 · Sean Couch🇺🇸
Core-collapse supernova explosions are driven by a central engine that converts a small fraction of the gravitational binding energy released during core collapse to outgoing kinetic energy. The suspected mode for this energy conversion is the neutrino mechanism, where a fraction of the neutrinos emitted from the newly formed protoneutron star are absorbed by and heat the matter behind the supernova shock. Accurate neutrino-matter interaction terms are crucial for simulating these explosions. In this proceedings for IAUS 331, SN 1987A, 30 years later, we explore several corrections to the neutrino-nucleon scattering opacity and demonstrate the effect on the dynamics of the core-collapse supernova central engine via two dimensional neutrino-radiation-hydrodynamics simulations. Our results reveal that the explosion properties are sensitive to corrections to the neutral-current scattering cross section at the 10-20% level, but only for densities at or above $\sim 1 0^{12}$ g cm $^{- 3}$
Comments:
6 pages, 3 figures, appears in Proc. IAU Symposium 331, SN 1987A, 30 years later - Cosmic Rays and Nuclei from Supernovae and Their Aftermaths
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1712.08253 [pdf]
IAU Symp.(2017)·10 citations
04
[Submitted on 22 Dec 2017] (cross-list from hep-ph)
Nucleon shadowing effects in $C u + C u$ and $A u + A u$ collisions at RHIC within the HIJING code
Khaled Abdel-Waged🇸🇦 · Nuha Felemban🇸🇦
The centrality dependence of pseudorapidity density of charged particles ( $d N_{c h} / d η$ ) in $C u + C u$ ( $A u + A u$ ) collisions at RHIC energy of $s_{_{NN}} = 22.4$ , $62.4$ and $200$ ( $19.6$ , $62.4$ and $200$ ) GeV, is investigated within an improved HIJING code. The standard HIJING model is enhanced by a prescription for collective nucleon-nucleon ( $N N$ ) interactions and more modern parton distribution functions. The collective $N N$ -interactions are used to induce both cascade and nucleon shadowing effects. We find collective cascade broadens the pseudorapidity distributions in the tails (at $∣ η ∣ > y_{beam}$ ) above $25 - 30%$ collision centrality to be consistent with the $d N_{c h} / d η$ data at $s_{_{NN}} = 19.6$ , $22.4$ , $62.4$ GeV. The overall contribution of nucleon shadowing is shown to depress the whole shape of $d N_{c h} / d η$ in the primary interaction region (at $∣ η ∣ < y_{beam}$ ) for semiperipheral ( $20 - 25$ \%) and peripheral ( $\geq 35 - 40$ \%) $C u + C u$ ( $A u + A u$ ) interactions at $s_{_{NN}} = 200$ GeV, in accordance with the PHOBOS data.
Comments:
18 pages, 10 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1712.08298 [pdf]
J.Phys.G(2018)·3 citations
05
[Submitted on 22 Dec 2017] (cross-list from hep-lat)
Heavy light tetraquarks from Lattice QCD
Parikshit Junnarkar🇮🇳 · M Padmanath🇩🇪 · Nilmani Mathur🇮🇳
We present preliminary results from a lattice calculation of tetraquark states in the charm and bottom sector of the type $u d b ˉ b ˉ$ , $u s b ˉ b ˉ$ , $u d c ˉ c ˉ$ and $sc b ˉ b ˉ$ . These calculations are performed on $N_{f} = 2 + 1 + 1$ MILC ensembles with lattice spacing of $a = 0.12 fm$ and $a = 0.06 fm$ . A relativistic action with overlap fermions is employed for the light and charm quarks while a non-relativistic action with non-perturbatively improved coefficients is used in the bottom sector. Preliminary results provide a clear indication of presence of energy levels below the relevant thresholds of different tetraquark states. While in double charm sector we find shallow bound levels, our results suggest deeply bound levels with double bottom tetraquarks.
Comments:
Corrected threshold for the $u d c ˉ c ˉ$ tetraquark state. Proceedings of the 35th International Symposium on Lattice Field Theory, 18-24 June 2017, Granada, Spain. TIFR preprint no : TIFR/TH/17-39
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1712.08400 [pdf]
EPJ Web Conf.(2018)·13 citations
06
[Submitted on 22 Dec 2017] (cross-list from hep-ph)
Fluctuation and Dissipation of Axial Charge from Massive Quarks
De-fu Hou🇨🇳 · Shu Lin🇨🇳
In quantum chromodynamics (QCD), axial charge is known to be non-conserved due to chiral anomaly and non-vanishing quark mass. In this paper, we explore the role of quark mass in axial charge fluctuation and dissipation. We present two separate calculations of axial charge correlator, which describe dynamics of axial charge. The first is free quarks at finite temperature. We find that axial charge can be generated through effective quantum fluctuations in free theory. However the fluctuation does not follow a random walk behavior. Due to the presence of axial symmetry breaking mass term, the axial charge also does not settle asymptotically to the thermodynamic limit given by susceptibility. The second calculation is in weakly coupled quark gluon plasma (QGP). We find in the hard thermal loop (HTL) approximation, the quark-gluon interaction leads to random walk growth of axial charge, but dissipation is not visible. We estimate relaxation time scale for axial charge, finding it lies beyond the HTL regime.
Comments:
17 pages, 3 figures. Susceptibility contribution added in free theory case. Computation of weakly coupled case simplified by Ward identity. To appear in PRD
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1712.08429 [pdf]
PRD(2018)·23 citations
07
[Submitted on 22 Dec 2017] (cross-list from hep-lat)
Spectroscopy of Charmed and Bottom Hadrons using Lattice QCD
Sourav Mondal🇮🇳 · M. Padmanath🇩🇪 · Nilmani Mathur🇮🇳
We present preliminary results on the light, charmed and bottom baryon spectra using overlap valence quarks on the background of 2+1+1 flavours HISQ gauge configurations of the MILC collaboration. These calculations are performed on three different gauge ensembles at three lattice spacings (a ~ 0.12 fm, 0.09 fm and 0.06 fm) and for physical strange, charm and bottom quark masses. The SU(2) heavy baryon chiral perturbation theory is used to extrapolate baryon masses to the physical pion mass and the continuum limit extrapolations are also performed. Our results are consistent with the well measured charmed baryons. We predict the masses of many other states which are yet to be discovered.
Comments:
8 pages, Proceedings of the 35th International Symposium on Lattice Field Theory (Lattice 2017)
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1712.08446 [pdf]
EPJ Web Conf.(2018)·4 citations
08
[Submitted on 22 Dec 2017] (cross-list from hep-ph)
Fine-tuning in scalar meson decay with bound-state corrections
M. L. L. da Silva🇧🇷 · D. T. da Silva🇧🇷 · C. A. Z. Vasconcellos🇧🇷 · D. Hadjimichef🇧🇷
The glueball-quarkonia mixture decay amplitude has been evaluated, in the literature, by diagrammatic techniques for drawing quark lines and the quark-gluon vertex. In this paper we use an alternative approach which consists in a mapping technique, the Fock-Tani formalism, in order to obtain an effective Hamiltonian starting from microscopic interactions. An extra effect is present in this formalism associated to the extended nature of mesons: bound-state corrections, which introduces an additional decay amplitude and sets a fine-tuning procedure for general meson decay calculations. The $f_{0} (1500) \to π π$ channel shall be considered as numerical example of the procedure.
Comments:
6 pages, 2 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1712.08503 [pdf]
0 citations
09
[Submitted on 22 Dec 2017] (cross-list from hep-ph)
New color-magnetic defects in dense quark matter
Alexander Haber🇦🇹 · Andreas Schmitt🇬🇧
Color-flavor locked (CFL) quark matter expels color-magnetic fields due to the Meissner effect. One of these fields carries an admixture of the ordinary abelian magnetic field and therefore flux tubes may form if CFL matter is exposed to a magnetic field, possibly in the interior of neutron stars or in quark stars. We employ a Ginzburg-Landau approach for three massless quark flavors, which takes into account the multi-component nature of color superconductivity. Based on the weak-coupling expressions for the Ginzburg-Landau parameters, we identify the regime where CFL is a type-II color superconductor and compute the radial profiles of different color-magnetic flux tubes. Among the configurations without baryon circulation we find a new solution that is energetically preferred over the flux tubes previously discussed in the literature in the parameter regime relevant for compact stars. Within the same setup, we also find a new defect in the 2SC phase, namely magnetic domain walls, which emerge naturally from the previously studied flux tubes if a more general ansatz for the order parameter is used. Color-magnetic defects in the interior of compact stars allow for sustained deformations of the star, potentially strong enough to produce detectable gravitational waves.
Comments:
29 pages, 5 figures, v2: small modifications in the text, version accepted for publication in Journal of Physics G, v3: sign error in Sec. V in front of the charge $q ~_{83}$ corrected (all results unaffected since error was exactly compensated by negative winding number $n_{3}$ , which is positive in the new version)
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1712.08587 [pdf]
J.Phys.G(2018)·20 citations

Affiliations

first authorsco-authorsvia INSPIRE