Nuclear Theory·nucl-th

Thursday·May 30, 2019

8 papers—5 primary·3 cross-listed

01
[Submitted on 28 May 2019]
Sensitivity of D meson azimuthal anisotropies to system size and nuclear structure
Roland Katz🇫🇷 · Caio A. G. Prado🇨🇳 · Jacquelyn Noronha-Hostler🇺🇸 · Jorge Noronha🇧🇷 · Alexandre A. P. Suaide🇧🇷 · Marcelo G. Munhoz🇧🇷
Recent experimental data at the Large Hadron Collider (LHC) confirmed that the soft sector azimuthal anisotropies in central XeXe collisions are sensitive to deformations in the wave function of the Xenon nucleus. Additionally, the CMS experiment found that D meson flow is slightly suppressed compared to other particle species when considering quark number scaling in small systems of pPb compared to PbPb. In this talk we used the D and B Mesons Modular (DAB-MOD) code coupled to Trento+v-USPhydro to calculate the $R_{AA}$ and $v_{n}$ 's of D mesons using different energy loss models and Langevin techniques. Comparing D mesons $R_{AA}$ and $v_{n}$ in PbPb to XeXe collisions it is found that in central collisions D meson azimuthal anisotropies are sensitive to details in the nuclear structure wave function of Xenon. Additionally, we find that in mid-central collisions the smaller system size of XeXe suppresses D meson flow.
Comments:
9 pages, 3 figures, proceedings for the 13th annual International Workshop on High pT Physics
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1905.12038 [pdf]
PoS(2020)·0 citations
02
[Submitted on 28 May 2019]
Linear response theory in asymmetric nuclear matter for Skyrme functionals including spin-orbit and tensor terms II: Charge Exchange
D. Davesne🇫🇷 · A. Pastore🇬🇧 · J. Navarro🇪🇸
We present the formalism of linear response theory both at zero and finite temperature in the case of asymmetric nuclear matter excited by an isospin flip probe. The particle-hole interaction is derived from a general Skyrme functional that includes spin-orbit and tensor terms. Response functions are obtained by solving a closed algebraic system of equations. Spin strength functions are analyzed for typical values of density, momentum transfer, asymmetry and temperature.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1905.12049 [pdf]
PRC(2019)·10 citations
03
[Submitted on 29 May 2019]
The effect of internal magnetic field on collective flow in heavy ion collisions at intermediate energies
Yuliang Sun🇨🇳 · Yongjia Wang🇨🇳 · Qingfeng Li🇨🇳 · Fuqiang Wang🇨🇳
The properties of nuclear matter under extreme conditions of high temperature, density and isospin-asymmetry have attracted wide attentions in recent years. At present, heavy ion reactions in combination with corresponding model simulations are one of the most important ways to investigate this subject. It is known that a strong magnetic field can be created in heavy ion collisions. However, its effect on the motion of charged particles is usually neglected in previous transport model simulations. In this work, within the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model, the temporal evolution and spatial distribution of the internal magnetic field are calculated. The magnetic field strength is found to reach about $e B \approx 470$ MeV $^{2}$ ( $B \approx 8 \times 1 0^{16}$ G) for Au+Au collisions at $E_{lab}$ =1 GeV/nucleon with impact parameter of 7 fm. The magnetic field in Cu+Au collisions exhibits somewhat different spatial distribution from that in Au+Au collisions. The magnetic field is found to affect the directed flow of pions at forward and backward rapidities to some extent, dependent of the impact parameter and beam energy while the effect on the elliptic flow is small. This suggests that, because $π$ mesons produced in heavy ion collisions at intermediate energies are considered as a sensitive probe for the nuclear symmetry energy, it is necessary to consider the effect of the internal magnetic field.
Comments:
26 pages, 19 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1905.12492 [pdf]
PRC(2019)·13 citations
04
[Submitted on 29 May 2019]
Do we know how to count powers in pionless and pionful effective field theory?
C.-J. Yang🇸🇪
In this article I summarize recent progress in the effective field theory approach to low energy nuclear systems, with a focus on the power counting issue. In the pionless sector, where the power counting is quite well understood at the nucleon-nucleon (NN) level, I discuss some recent developments toward few- and many-body calculations. In the pionful sector, I focus on the actively debated issue of power counting in the NN sector and some recent developments toward a model-independent NN interaction. Finally, the scenario that the power counting might depend on the number of particles is discussed.
Comments:
19 pages, 1 figure. Contributions to the EPJA topical issue: The tower of effective (field) theories and the emergence of nuclear phenomena. Published version
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1905.12510 [pdf]
EPJA(2020)·29 citations
05
[Submitted on 29 May 2019]
Magnetic Field Induced Polarization Difference between Hyperons and Anti-hyperons
Yu Guo🇨🇳 · Shuzhe Shi🇨🇦 · Shengqin Feng🇨🇳 · Jinfeng Liao🇺🇸
Recent STAR measurements suggest a difference in the global spin polarization between hyperons and anti-hyperons, especially at relatively low collision beam energy. One possible cause of this difference is the potential presence of in-medium magnetic field. In this study, we investigate the phenomenological viability of this interpretation. Using the AMPT model framework, we quantify the influence of different magnetic field evolution scenarios on the size of the polarization difference in a wide span of collision beam energies. We find that such difference is very sensitive to the lifetime of the magnetic field. For the same lifetime, the computed polarization difference only mildly depends on the detailed form of its evolution. Assuming magnetic polarization as the mechanism to enhance anti-hyperon signal while suppress hyperon signal, we phenomenologically extract an upper limit on the needed magnetic field lifetime in order to account for the experimental data. The so-obtained lifetime values are in a quite plausible ballpark and follow approximately the scaling relation of being inversely proportional to the beam energy. Possible implications on other magnetic field related effects are also discussed.
Comments:
7 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1905.12613 [pdf]
PLB(2019)·105 citations
06
[Submitted on 28 May 2019] (cross-list from hep-ph)
On the Equivalence of Three-Particle Scattering Formalisms
A. W. Jackura🇺🇸 · S. M. Dawid🇺🇸 · C. Fernández-Ramírez🇲🇽 · V. Mathieu🇪🇸 · M. Mikhasenko🇨🇭 · A. Pilloni🇮🇹 · S. R. Sharpe🇺🇸 · A. P. Szczepaniak🇺🇸
In recent years, different on-shell $3 \to 3$ scattering formalisms have been proposed to be applied to both lattice QCD and infinite volume scattering processes. We prove that the formulation in the infinite volume presented by Hansen and Sharpe in Phys.~Rev.~D92, 114509 (2015) and subsequently Briceño, Hansen, and Sharpe in Phys.~Rev.~D95, 074510 (2017) can be recovered from the $B$ -matrix representation, derived on the basis of $S$ -matrix unitarity, presented by Mai {\em et al.} in Eur.~Phys.~J.~A53, 177 (2017) and Jackura {\em et al.} in Eur.~Phys.~J.~C79, 56 (2019). Therefore, both formalisms in the infinite volume are equivalent and the physical content is identical. Additionally, the Faddeev equations are recovered in the non-relativistic limit of both representations.
Comments:
13 pages, 5 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1905.12007 [pdf]
PRD(2019)·93 citations
07
[Submitted on 28 May 2019] (cross-list from hep-ph)
New physics via pion capture and simple nuclear reactions
Chien-Yi Chen🇨🇦 · David McKeen🇨🇦 · Maxim Pospelov🇨🇦
Light, beyond-the-standard-model particles $X$ in the 1-100 MeV mass range can be produced in nuclear and hadronic reactions but would have to decay electromagnetically. We show that simple and well-understood low-energy hadronic processes can be used as a tool to study $X$ production and decay. In particular, the pion capture process $π^{-} p \to X n \to e^{+} e^{-} n$ can be used in a new experimental setup to search for anomalies in the angular distribution of the electron-positron pair, which could signal the appearance of dark photons, axion-like particles and other exotic states. This process can be used to decisively test the hypothesis of a new particle produced in the $^{7} Li + p$ reaction. We also discuss a variety of other theoretically clean hadronic processes, such as $p + D (T)$ fusion, as a promising source of $X$ particles.
Comments:
9 pages, 5 figures, typo in acknowledgments corrected
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1905.12017 [pdf]
PRD(2019)·8 citations
08
[Submitted on 29 May 2019] (cross-list from hep-th)
Dynamics of Phase Separation from Holography
Maximilian Attems🇪🇸 · Yago Bea🇪🇸 · Jorge Casalderrey-Solana🇪🇸 · David Mateos🇪🇸 · Miguel Zilhao🇪🇸
We use holography to develop a physical picture of the real-time evolution of the spinodal instability of a four-dimensional, strongly-coupled gauge theory with a first-order, thermal phase transition. We numerically solve Einstein's equations to follow the evolution, in which we identify four generic stages: A first, linear stage in which the instability grows exponentially; a second, non-linear stage in which peaks and/or phase domains are formed; a third stage in which these structures merge; and a fourth stage in which the system finally relaxes to a static, phase-separated configuration. On the gravity side the latter is described by a static, stable, inhomogeneous horizon. We conjecture and provide evidence that all static, non-phase separated configurations in large enough boxes are dynamically unstable. We show that all four stages are well described by the constitutive relations of second-order hydrodynamics that include all second-order gradients that are purely spatial in the local rest frame. In contrast, a Müller-Israel-Stewart-type formulation of hydrodynamics fails to provide a good description for two reasons. First, it misses some large, purely-spatial gradient corrections. Second, several second-order transport coefficients in this formulation, including the relaxation times $τ_{π}$ and $τ_{Π}$ , diverge at the points where the speed of sound vanishes.
Comments:
45 pages, 35 figures; published version
Subjects:
High Energy Physics — Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1905.12544 [pdf]
JHEP(2020)·48 citations

Affiliations

first authorsco-authorsvia INSPIRE