Nuclear Theory·nucl-th

Wednesday·October 21, 2015

10 papers—6 primary·4 cross-listed

01
[Submitted on 19 Oct 2015]
$χ$ EFT studies of few-nucleon systems: a status report
R. Schiavilla🇺🇸
A status report on $χ$ EFT studies of few-nucleon electroweak structure and dynamics is provided, including electromagnetic form factors of few-nucleon systems, the $pp$ weak fusion and muon weak captures on deuteron and $^{3}$ He, and a number of parity-violating processes induced by hadronic weak interactions.
Comments:
12 pages, 8 figures, proceedings of 8th Workshop on Chiral Dynamics, Pisa, Italy
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1510.05689 [pdf]
PoS(2015)·0 citations
02
[Submitted on 20 Oct 2015]
Physics perspectives of heavy-ion collisions at very high energy
Ning-bo Chang (CCNU)🇨🇳 · Shanshan Cao (LBNL)🇺🇸 · Bao-yi Chen (Tsinghua U)🇨🇳 · Shi-yong Chen (CCNU)🇨🇳 · Zhen-yu Chen (Tsinghua U)🇨🇳 · Heng-Tong Ding (CCNU)🇨🇳 · Min He (NUSTC)🇨🇳 · Zhi-quan Liu (CCNU)🇨🇳 · Long-gang Pang (CCNU)🇨🇳 · Guang-you Qin (CCNU)🇨🇳 · Ralf Rapp (TAMU)🇺🇸 · Björn Schenke (BNL)🇺🇸 and 9 other authors
Heavy-ion collisions at very high colliding energies are expected to produce a quark-gluon plasma (QGP) at the highest temperature obtainable in a laboratory setting. Experimental studies of these reactions can provide an unprecedented range of information on properties of the QGP at high temperatures. We report theoretical investigations of the physics perspectives of heavy-ion collisions at a future high-energy collider. These include initial parton production, collective expansion of the dense medium, jet quenching, heavy-quark transport, dissociation and regeneration of quarkonia, photon and dilepton production. We illustrate the potential of future experimental studies of the initial particle production and formation of QGP at the highest temperature to provide constraints on properties of strongly interaction matter.
Comments:
35 pages in Latex, 29 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1510.05754 [pdf]
SCPMA(2016)·24 citations
03
[Submitted on 15 Oct 2015]
A parameterized model for Coulomb barrier height
Deepak Kumar Swami · Prashant Sharma · Tapan Nandi
Coulomb barrier height is a basic parameter to describing the nuclear reactions. Recently it is found that ions produce from nuclear reactions can be used to study electron loss and capture processes. Hence determining the Coulomb barrier becomes important in both nuclear and atomic physics. The different models depend on the nucleus-nucleus potential chosen or parameters used to calculate the barrier heights. In this work we plan to develop a parameterized formula from experimental results obtained from quasi elastic scattering. Since quasi elastic data spread over Z1Z2=64 to Z1Z2=2460, the formula is expected to work in the range of low Z1Z2 to high Z1Z2, where Z1, Z2 are the atomic number of the projectile and the target, respectively.
Comments:
2 Pages, 2 Figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1510.05919 [pdf]
0 citations
04
[Submitted on 20 Oct 2015]
Theoretical Optical Potential Derived From Nucleon-Nucleon Chiral Potentials
M. Vorabbi · P. Finelli · C. Giusti
Background: Elastic scattering is probably the main event in the interactions of nucleons with nuclei. Even if this process has been extensively studied in the last years, a consistent description, i.e. starting from microscopic two- and many-body forces connected by the same symmetries and principles, is still under development. Purpose: In this work we study the domain of applicability of microscopic two-body chiral potentials in the construction of an optical potential. Methods: We basically follow the KMT approach to build a microscopic complex optical potential and then we perform some test calculations on 16O at different energies. Results: Our conclusion is that a particular set of potentials with a Lippmann-Schwinger cutoff at relatively high energies (above 500 MeV) has the best performances reproducing the scattering observables. Conclusions: Our work shows that building an optical potential within Chiral Perturbation Theory is a promising approach to the description of elastic proton scattering, in particular, in view of the future inclusion of many-body forces that naturally arise in such framework.
Comments:
15 pages and 12 figures. Accepted version (Physical Review C) with major changes in Sect. III and IV and new figures (5,10,11,12)
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1510.05928 [pdf]
PRC(2016)·47 citations
05
[Submitted on 20 Oct 2015]
Spin-polarized neutron matter: Critical unpairing and BCS-BEC precursor
Martin Stein · Armen Sedrakian · Xu-Guang Huang · John W. Clark
We obtain the critical magnetic field required for complete destruction of $S$ -wave pairing in neutron matter, thereby setting limits on the pairing and superfluidity of neutrons in the crust and outer core of magnetars. We find that for fields $B \geq 1 0^{17}$ G the neutron fluid is non-superfluid -- if weaker spin-1 superfluidity does not intervene -- a result with profound consequences for the thermal, rotational, and oscillatory behavior of magnetars. Because the dineutron is not bound in vacuum, cold dilute neutron matter cannot exhibit a proper BCS-BEC crossover. Nevertheless, owing to the strongly resonant behavior of the $nn$ interaction at low densities, neutron matter shows a precursor of the BEC state, as manifested in Cooper-pair correlation lengths {being} comparable to the interparticle distance. We make a systematic quantitative study of this type of BCS-BEC crossover in the presence of neutron fluid spin-polarization induced by an ultra-strong magnetic field. We evaluate the Cooper pair wave-function, quasiparticle occupation numbers, and quasiparticle spectra for densities and temperatures spanning the BCS-BEC crossover region. The phase diagram of spin-polarized neutron matter is constructed and explored at different polarizations.
Comments:
13 RevTex pages, 18 figures, v2: minor changes, references added, matches published version
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
1510.06000 [pdf]
PRC(2016)·41 citations
06
[Submitted on 20 Oct 2015]
The black hole spin influence on accretion disk neutrino detection
O. L. Caballero🇨🇦 · T. Zielinski🇨🇦 · G. C. McLaughlin🇺🇸 · R. Surman🇺🇸
Neutrinos are copiously emitted from black hole accretion disks playing a fundamental role in their evolution, as well as in the production of gamma ray bursts and r-process nucleosynthesis. The black hole generates a strong gravitational field able to change the properties of the emerging neutrinos. We study the influence of the black hole spin on the structure of the neutrino surfaces, neutrino luminosities, average neutrino energies, and event counts at SuperK. We consider several disk models and provide estimates that cover different black hole efficiency scenarios. We discuss the influence of the detector's inclination with respect to the axis of the torus on neutrino properties. We find that tori around spinning black holes have larger luminosities, energies and rates compared to tori around static black holes, and that the inclination of the observer causes a reduction in the luminosities and detection rates but an increase in the average energies.
Comments:
10 pages, 5 figures, submitted to PRD
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)
arXiv:
1510.06011 [pdf]
PRD(2016)·23 citations
07
[Submitted on 19 Oct 2015] (cross-list from hep-ph)
Model-independent determination of the axial mass parameter in quasielastic antineutrino-nucleon scattering
Bhubanjyoti Bhattacharya🇨🇦 · Gil Paz🇺🇸 · Anthony J. Tropiano🇺🇸
Understanding the charged current quasielestic (CCQE) neutrino-nucleus interaction is important for precision studies of neutrino oscillations. The theoretical description of the interaction depends on the combination of a nuclear model with the knowledge of form factors. While the former has received considerable attention, the latter, in particular the axial form factor, is implemented using the historical dipole model. Instead, we use a model-independent approach, presented in a previous study, to analyze the muon antineutrino CCQE mineral oil data published by the MiniBooNE collaboration. We combine the cross section for scattering of antineutrinos off protons in carbon and hydrogen, using the same axial form factor for both. The extracted value of the axial mass parameter $m_{A} = 0.8 4_{- 0.04}^{+ 0.12} \pm 0.11 GeV$ is in very good agreement with the model-independent value extracted from MiniBooNE's neutrino data. Going beyond a one-parameter description of the axial form factor, we extract values of the axial form factor in the range of $Q^{2} = 0.1...1.0$ GeV $^{2}$ , finding a very good agreement with the analogous extraction from the neutrino data. We discuss the implications of these results.
Comments:
13 pages, 3 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1510.05652 [pdf]
PRD(2015)·39 citations
08
[Submitted on 20 Oct 2015] (cross-list from hep-ph)
Three-gluon correlator contribution to Sivers asymmetry in SIDIS
Ling-Yun Dai🇺🇸
We study the Sivers asymmetry in semi-inclusive deep inelastic scattering: the three-gluon correlation function contribution. At the cross section level, we establish the matching between the twist-3 collinear factorization approach and the transverse momentum dependent factorization formalism at the moderate transverse momentum region. The so-called coefficient functions when one expands the quark Sivers function in terms of three-gluon correlation functions are derived, which are essential components in the usual transverse momentum dependent evolution formalism. Finally we calculate the transverse-momentum-weighted spin-dependent differential cross section at the next-to-leading order, from which we identify the off-diagonal/three-gluon correlation contribution to the QCD collinear evolution of the twist-3 Qiu-Sterman function.
Comments:
7 pages
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1510.05748 [pdf]
PoS(2015)·0 citations
09
[Submitted on 20 Oct 2015] (cross-list from hep-lat)
Neutron electric dipole moment using $N_{f} = 2 + 1 + 1$ twisted mass fermions
C. Alexandrou (Univ. of Cyprus and Cyprus Inst.)🇨🇾 · A. Athenodorou (Univ. of Cyprus and Cyprus Inst.)🇨🇾 · M. Constantinou (Univ. of Cyprus and Cyprus Inst.)🇨🇾 · K. Hadjiyiannakou (Univ. of Cyprus and Cyprus Inst.)🇨🇾 · K. Jansen (NIC, DESY-Zeuthen)🇩🇪 · G. Koutsou (Cyprus Inst.)🇨🇾 · K. Ottnad (Univ. of Cyprus and Bonn Univ.)🇨🇾 · M. Petschlies (Cyprus Inst. and Bonn Univ.)🇨🇾
We evaluate the neutron electric dipole moment $∣ d_{N} ∣$ using lattice QCD techniques. The gauge configurations analyzed are produced by the European Twisted Mass Collaboration using $N_{f} = 2 + 1 + 1$ twisted mass fermions at one value of the lattice spacing of $a ≃ 0.082 fm$ and a light quark mass corresponding to $m_{π} ≃ 373 MeV$ . Our approach to extract the neutron electric dipole moment is based on the calculation of the $C P$ -odd electromagnetic form factor $F_{3} (Q^{2})$ for small values of the vacuum angle $θ$ in the limit of zero Euclidean momentum transfer $Q^{2}$ . The limit $Q^{2} \to 0$ is realized either by adopting a parameterization of the momentum dependence of $F_{3} (Q^{2})$ and performing a fit, or by employing new position space methods, which involve the elimination of the kinematical momentum factor in front of $F_{3} (Q^{2})$ . The computation in the presence of a $C P$ -violating term requires the evaluation of the topological charge $Q$ . This is computed by applying the cooling technique and the gradient flow with three different actions, namely the Wilson, the Symanzik tree-level improved and the Iwasaki action. We demonstrate that cooling and gradient flow give equivalent results for the neutron electric dipole moment. Our analysis yields a value of $∣ d_{N} ∣ = 0.045 (6) (1) θ ˉ e \cdot fm$ for the ensemble with $m_{π} = 373$ MeV considered.
Comments:
Version accepted for publication in Phys. Rev. D.: 33 pages, 13 Figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1510.05823 [pdf]
PRD(2016)·52 citations
10
[Submitted on 20 Oct 2015] (cross-list from hep-ph)
Long-range properties of $1 S$ bottomonium states
Nora Brambilla🇩🇪 · Gastão Krein🇧🇷 · Jaume Tarrús Castellà🇩🇪 · Antonio Vairo🇩🇪
In the framework of weakly-coupled pNRQCD, we derive, first, an analytical expression for the chromo-polarizability of $1 S$ -bottomonium states in agreement with previous determinations. Then we use the QCD trace anomaly to obtain the two-pion production amplitude for the chromo-polarizability operator and match the result to a chiral effective field theory with $1 S$ -bottomonium states and pions as degrees-of-freedom. In this chiral effective field theory we compute some long-range properties of the $1 S$ bottomonium generated by the pion coupling such as the leading chiral logarithm to the $1 S$ -bottomonium mass and the van der Waals potential between two $1 S$ -bottomonium states. Both results improve on previously known expressions.
Comments:
24 pages, 10 figures. Journal version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1510.05895 [pdf]
PRD(2016)·77 citations

Affiliations

first authorsco-authorsvia INSPIRE