Nuclear Theory·nucl-th

Friday·April 1, 2016

4 papers—2 primary·2 cross-listed

01
[Submitted on 30 Mar 2016]
Fragmentation of Neutron Star Matter
P. N. Alcain · C. O. Dorso
Background: Neutron stars are astronomical systems with nucleons submitted to extreme conditions. Due to the long range coulomb repulsion between protons, the system has structural inhomogeneities. These structural inhomogeneities arise also in expanding systems, where the fragment distribution is highly dependent on the thermodynamic conditions (temperature, proton fraction, ...) and the expansion velocity. Purpose: We aim to find the different regimes of fragment distribution, and the existence of infinite clusters. Method: We study the dynamics of the nucleons with a semiclassical molecular dynamics model. Starting with an equilibrium configuration, we expand the system homogeneously until we arrive to an asymptotic configuration (i. e. very low final densities). We study the fragment distribution throughout this expansion. Results: We found the typical regimes of the asymptotic fragment distribution of an expansion: u-shaped, power law and exponential. Another key feature in our calculations is that, since the interaction between protons is long range repulsive, we do not have always an infinite fragment. We found that, as expected, the faster the expansion velocity is, the quicker the infinite fragment disappears. Conclusions: We have developed a novel graph-based tool for the identification of infinite fragments, and found a transition from U-shaped to exponential fragment mass distribution with increasing expansion rate.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1603.09362 [pdf]
0 citations
02
[Submitted on 31 Mar 2016]
Mesonic Decay of Charm Hypernuclei $Λ_{c}^{+}$
Sabyasachi Ghosh🇧🇷 · Carlos E. Fontoura🇧🇷 · Gastão Krein🇧🇷
$Λ_{c}^{+}$ hypernuclei are expected to have binding energies and other properties similar to those of strange hypernuclei in view of the similarity between the quark structures of the strange and charmed hyperons, namely $Λ (u d s)$ and $Λ_{c}^{+} (u d c)$ . One striking difference however occurs in their mesonic decays, as there is almost no Pauli blocking in the nucleonic decay of a charm hypernucleus because the final-state nucleons leave the nucleus at high energies. The nuclear medium nevertheless affects the mesonic decays of charm hypernucleus because the nuclear mean fields modify the masses of the charm hyperon. In the present communication we present results of a first investigation of the effects of finite baryon density on different weak mesonic decay channels of the $Λ_{c}^{+}$ baryon. We found a non-negligible reduction of the decay widths as compared to their vacuum values.
Comments:
Conference name : 21st International Conference on Few-Body Problems in Physics (Chicago, Illinois, USA, from May 18th to 22nd, 2015), Conference Link : http://www.phy.ohiou.edu/~fewbody/FB21Files/generalinfo.html ; Proceeding Link : http://www.epj-conferences.org/articles/epjconf/abs/2016/08/epjconf_fb2016_05016/epjconf_fb2016_05016.html
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1603.09640 [pdf]
EPJ Web Conf.(2016)·2 citations
03
[Submitted on 31 Mar 2016] (cross-list from hep-ph)
Thermal Model Description of Collisions of Small Nuclei
H. Oeschler🇿🇦 · J. Cleymans🇫🇷 · B. Hippolyte🇩🇪 · K. Redlich🇺🇸 · N. Sharma🇮🇳
The dependence of particle production on the size of the colliding nuclei is analysed in terms of the thermal model using the canonical ensemble. The concept of strangeness correlation in clusters of sub-volume $V_{c}$ is used to account for the suppression of strangeness. A systematic analysis is presented of the predictions of the thermal model for particle production in collisions of small nuclei. The pattern of the maxima of strange-particles-to-pion ratios as a function of beam energy is quite special, as they do not occur at the same beam energy and are sensitive to system size. In particular, the $Λ/ π^{+}$ ratio shows a clear maximum even for small systems while the maximum in the K $^{+} / π^{+}$ ratio is less pronounced
Comments:
8 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1603.09553 [pdf]
14 citations
04
[Submitted on 31 Mar 2016] (cross-list from hep-ph)
Influence of jets and decays of resonances on the triangular flow in ultrarelativistic heavy-ion collisions
J. Crkovska🇫🇷 · J. Bielcik🇨🇿 · L. Bravina🇳🇴 · B.H. Brusheim Johansson🇳🇴 · E. Zabrodin🇷🇺 · G. Eyyubova🇷🇺 · V.L. Korotkikh🇷🇺 · I.P. Lokhtin🇷🇺 · L.V. Malinina🇷🇺 · S.V. Petrushanko🇷🇺 · A.M. Snigirev🇷🇺
Triangular flow $v_{3}$ of identified and inclusive particles in Pb+Pb collisions at $s_{N N} = 2.76$ TeV is studied as a function of centrality and transverse momentum within the \textsc{hydjet++} model. The model enables one to investigate the influence of both hard processes and final-state interactions on the harmonics of particle anisotropic flow. Decays of resonances are found to increase the magnitude of the $v_{3} (p_{T})$ distributions at $p_{T} \geq 2$ GeV/ $c$ and shift their maxima to higher transverse momenta. The $p_{T}$ -integrated triangular flow, however, becomes slightly weakened for all centralities studied. The resonance decays also modify the spectra towards the number-of-constituent-quark scaling fulfillment for the triangular flow, whereas jets are the main source of the scaling violation at the energies available at the CERN Large Hadron Collider (LHC). Comparison with the corresponding spectra of elliptic flow reveals that resonance decays and jets act in a similar manner on both $v_{3} (p_{T})$ and $v_{2} (p_{T})$ behavior. Obtained results are also confronted with the experimental data on differential triangular flow of identified hadrons, ratio $v_{3}^{1/3} (p_{T}) / v_{2}^{1/2} (p_{T})$ and $p_{T}$ -integrated triangular flow of charged hadrons.
Comments:
revised version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1603.09621 [pdf]
PRC(2017)·23 citations

Affiliations

first authorsco-authorsvia INSPIRE

Fragmentation of Neutron Star Matter

Mesonic Decay of Charm Hypernuclei Λc+​

Thermal Model Description of Collisions of Small Nuclei

Influence of jets and decays of resonances on the triangular flow in ultrarelativistic heavy-ion collisions

Affiliations

Mesonic Decay of Charm Hypernuclei $Λ_{c}^{+}$