Nuclear Theory·nucl-th

Wednesday·March 16, 2016

8 papers—2 primary·6 cross-listed

01
Searching for $Ξ_{cc}^{+}$ in Relativistic Heavy Ion Collisions
Jiaxin Zhao🇨🇳 · Hang He🇨🇳 · Pengfei Zhuang🇨🇳
We study the doubly charmed baryon $Ξ_{cc}^{+}$ in high energy nuclear collisions. We solve the three-body Schroedinger equation with relativistic correction and calculate the $Ξ_{cc}^{+}$ yield and transverse momentum distribution via coalescence mechanism. For $Ξ_{cc}^{+}$ production in central Pb+Pb collisions at LHC energy, the yield is extremely enhanced, and the production cross section per binary collision is one order of magnitude larger than that in p+p collisions. This indicates that, it is most probable to discover $Ξ_{cc}^{+}$ in heavy ion collisions and its discovery can be considered as a probe of the quark-luon plasma formation.
nucl-thhep-phPLB(2017)·30 citations
02
Optimum orientation versus orientation averaging description of cluster radioactivity
W. M. Seif · M. Ismail · A. I. Refaie · L. H. Amer
Background: The deformation of the nuclei involved in the cluster decay of heavy nuclei affect seriously their half-lives against the decay. Purpose: We investigate the description of the different decay stages in both the optimum orientation and the orientation-averaged pictures of the cluster decay process. Method: We consider the decays of 232,233,234U and 236,238Pu isotopes. The quantum mechanical knocking frequency and penetration probability based on the Wentzel-Kramers-Brillouin approximation are used to find the decay width. Results: We found that the orientation-averaged decay width is one or two orders of magnitude less than its value along the non-compact optimum orientation. The difference between the two values increases with decreasing the mass number of the emitted cluster. Correspondingly, the extracted preformation probability based on the averaged decay width increases with the same orders of magnitude compared to its value obtained considering the optimum orientation. The cluster preformation probabilities (Sc) obtained in the two considered schemes give more or less comparable agreement with the Blendowske-Walliser (BW) formula based on the preformation probability of Sa(ave.) obtained from the orientation-averaging scheme. All the obtained results, including those obtained in the optimum-orientation scheme, deviate substantially from the BW law based on Sa(opt.) obtained using the optimum-orientation scheme. Conclusion: In order to account for deformations of the participating nuclei, it is more relevant to calculate the decay width by averaging over the different possible orientations of the participating deformed nucleus, rather than considering the corresponding non-compact optimum orientation.
nucl-thJ.Phys.G(2016)·24 citations
03
Shape coexistence and the role of axial asymmetry in $^{72}$ Ge
A.D. Ayangeakaa🇺🇸 · R.V.F. Janssens🇺🇸 · C.Y. Wu🇺🇸 · J.M. Allmond🇺🇸 · J.L. Wood🇺🇸 · S. Zhu🇺🇸 · M. Albers🇺🇸 · S. Almaras-Calderon🇺🇸 · B. Bucher🇺🇸 · M.P. Carpenter🇺🇸 · C.J. Chiara🇺🇸 · D. Cline🇺🇸 and 13 other authors
The quadrupole collectivity of low-lying states and the anomalous behavior of the $0_{2}^{+}$ and $2_{3}^{+}$ levels in $^{72}$ Ge are investigated via projectile multi-step Coulomb excitation with GRETINA and CHICO-2. A total of forty six $E 2$ and $M 1$ matrix elements connecting fourteen low-lying levels were determined using the least-squares search code, gosia. Evidence for triaxiality and shape coexistence, based on the model-independent shape invariants deduced from the Kumar-Cline sum rule, is presented. These are interpreted using a simple two-state mixing model as well as multistate mixing calculations carried out within the framework of the triaxial rotor model. The results represent a significant milestone towards the understanding of the unusual structure of this nucleus.
↳ nucl-exnucl-thPLB(2016)·73 citations
04
Entropy production from chaoticity in Yang-Mills field theory with use of the Husimi function
Hidekazu Tsukiji🇯🇵 · Hideaki Iida🇯🇵 · Teiji Kunihiro🇯🇵 · Akira Ohnishi🇯🇵 · Toru T. Takahashi🇯🇵
We investigate possible entropy production in Yang-Mills (YM) field theory by using a quantum distribution function called Husimi function $f_{H} (A, E, t)$ for YM field, which is given by a coarse graining of Wigner function and non-negative. We calculate the Husimi-Wehrl (HW) entropy $S_{HW} (t) = - Tr f_{H} lo g f_{H}$ defined as an integral over the phase-space, for which two adaptations of the test-particle method are used combined with Monte-Carlo method. We utilize the semiclassical approximation to obtain the time evolution of the distribution functions of the YM field, which is known to show a chaotic behavior in the classical limit. We also make a simplification of the multi-dimensional phase-space integrals by making a product ansatz for the Husimi function, which is found to give a 10-20 per cent over estimate of the HW entropy for a quantum system with a few degrees of freedom. We show that the quantum YM theory does exhibit the entropy production, and that the entropy production rate agrees with the sum of positive Lyapunov exponents or the Kolmogorov-Sinai entropy, suggesting that the chaoticity of the classical YM field causes the entropy production in the quantum YM theory.
↳ hep-phcond-mat.stat-mechnucl-thPRD(2016)·22 citations
05
Heavy quark-antiquark free energy and thermodynamics of string-hadron avoided crossings
E. Megias🇩🇪 · E. Ruiz Arriola🇪🇸 · L. L. Salcedo🇪🇸
The correlation function between two Polyakov loops encodes the free-energy shift due to a pair of separated colour conjugated sources in the hot QCD medium. This is analyzed in terms of a novel Källén-Lehmann spectral representation for the separating distance, implying an increasing and concave free-energy at all temperatures. We express the heavy $Q ˉ Q$ free-energy shift below the phase transition in QCD in terms of colour neutral purely hadronic states with no explicit reference to quarks and gluons. Good agreement with lattice data is achieved when considering the avoided crossing mechanism underlying string breaking and with standard quenched values of the string tension known from charmonium and bottomonium phenomenology. We also address the role of the corresponding entropy shift and its renormalization group properties.
↳ hep-phhep-lathep-thnucl-thPRD(2016)·9 citations
06
Angular momentum content of the $ρ (1450)$ from chiral lattice fermions
C. Rohrhofer🇦🇹 · M. Pak🇦🇹 · L. Ya. Glozman🇦🇹
We identify the chiral and angular momentum content of the leading quark-antiquark Fock component for the $ρ (770)$ and $ρ (1450)$ mesons using a two-flavor lattice simulation with dynamical Overlap Dirac fermions. We extract this information from the overlap factors of two interpolating fields with different chiral structure and from the unitary transformation between chiral and angular momentum basis. For the chiral content of the mesons we find that the $ρ (770)$ slightly favors the $(1, 0) \oplus (0, 1)$ chiral representation and the $ρ (1450)$ slightly favors the $(1/2, 1/2)_{b}$ chiral representation. In the angular momentum basis the $ρ (770)$ is then a $^{3} S_{1}$ state, in accordance with the quark model. The $ρ (1450)$ is a $^{3} D_{1}$ state, showing that the quark model wrongly assumes the $ρ (1450)$ to be a radial excitation of the $ρ (770)$ .
↳ hep-lathep-phnucl-thBled Workshops Phys.(2016)·7 citations
07
Photon bremsstrahlung from quark jet via transverse and longitudinal scatterings: single versus multiple scatterings
Le Zhang🇨🇳 · De-Fu Hou🇨🇳 · Guang-You Qin🇨🇳
We study the production of jet-bremsstrahlung photons through the scattering with the constituents of a dense nuclear matter within the framework of deep-inelastic scattering off a large nucleus. Applying a gradient expansion up to the second order for the exchanged three-dimensional momentum between jet and medium, we derive the single photon bremsstrahlung spectrum with the inclusion of the contributions from the transverse broadening as well as the longitudinal drag and diffusion of the hard parton's momentum. We also compare the medium-induced photon radiation spectra for single scattering and from the resummation of multiple scatterings. It is found that the coupling between different scatterings can give additional contribution to medium-induced photon radiation, while for small momentum exchange, the leading contribution from the drag and diffusions to the photon emission spectra remain the same for single and multiple scatterings.
↳ hep-phnucl-exnucl-thPRC(2016)·5 citations
08
Empirical Parameterization of Nucleon-Nucleon Elastic Scattering Amplitude at High Beam Momenta for Glauber Calculations and Monte Carlo Simulations
V. Uzhinsky🇷🇺 · A. Galoyan🇷🇺 · Q. Hu🇨🇳 · J. Ritman🇩🇪 · H. Xu🇩🇪
A parameterization of the nucleon-nucleon elastic scattering amplitude is needed for future experiments with nucleon and nuclear beams in the beam momentum range of 2 -- 50 GeV/c/nucleon. There are many parameterizations of the amplitude at $P_{l ab} >$ 25--50 GeV/c, and at $P_{l ab} \leq$ 5 GeV/c. Our paper is aimed to cover the range between 5 -- 50 GeV/c. The amplitude is used in Glauber calculations of various cross sections and Monte Carlo simulations of nucleon-nucleon scatterings. Usually, the differential nucleon-nucleon elastic scattering cross sections are described by an exponential expression. Corresponding experimental data on $pp$ interactions at $∣ t ∣ >$ 0.005 (GeV/c) $^{2}$ and $∣ t ∣ \leq$ 0.125 (GeV/c) $^{2}$ have been fit. We propose formulae to approximate the beam momentum dependence of these parameters in the momentum range considered. The same was done for $n p$ interactions at $∣ t ∣ \leq$ 0.5 (GeV/c) $^{2}$ . Expressions for the momentum dependence of the total and elastic cross sections, and the ratio of real to imaginary parts of the amplitude at zero momentum transfer are also given for $pp$ and $n p$ collisions. These results are sufficient for a first approximation of the Glauber calculations. For more exact calculations we fit the data at $∣ t ∣ >$ 0.005 (GeV/c) $^{2}$ without restrictions on the maximum value of $∣ t ∣$ using an expression based on two coherent exponential. The parameters of the fits are found for the beam momentum range 2 -- 50 GeV/c.
↳ hep-phhep-exnucl-exnucl-thPRC(2016)·1 citation

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first authorsco-authorsvia INSPIRE