Nuclear Theory·nucl-th

Friday·October 16, 2015

14 papers—11 primary·3 cross-listed

01
Complete Strangeness Measurements in Heavy-Ion Collisions
Boris Tomasik🇸🇰 · E.E. Kolomeitsev🇸🇰
We discuss strangeness production in heavy-ion collisions within and around the energy range of the planned NICA facility. We describe the minimal statistical model, in which the total strangeness yield is fixed by the observed or calculated $K^{+}$ multiplicity. We show how the exact strangeness conservation can be taken into account on the event-by-event basis in such a model. We argue that from strange particle yields one can reveal information about the collision dynamics and about possible modifications of particle properties in medium. This can be best achieved if the complete strangeness measurement is performed, i.e. kaons, anti-kaons, hyperons and multistrange hyperons are registered in the same experimental setup. In particular the production of hadrons containing two and more strange quarks, like $Ξ$ and $Ω$ baryons could be of interest.
nucl-thEPJA(2016)·6 citations
02
From strangelets to strange stars: A unified description
Cheng-Jun Xia🇨🇳 · Guang-Xiong Peng🇨🇳 · En-Guang Zhao🇨🇳 · Shan-Gui Zhou🇨🇳
The conventionally separated treatments for strangelets and strange stars are now unified with a more comprehensive theoretical description for objects ranging from strangelets to strange stars. After constraining the model parameter according to the Witten-Bodmer hypothesis and observational mass-radius probability distribution of pulsars, we investigate the properties of this kind of objects. It is found that the energy per baryon decreases monotonously for increasing baryon number and reaches its minimum at the maximum baryon number, corresponding to the most massive strange star. Due to the quark depletion, an electric potential well for negatively charged particles is formed on the surface of the quark part, which may provide some unique observables. For a rotational bare strange star, a magnetic field with the typical strength of pulsars is generated.
nucl-thSci.Bull.(2016)·20 citations
03
Influence of finite volume and magnetic field effects on the QCD phase diagram
Niseem Magdy🇺🇸 · M. Csanád🇺🇸 · Roy A. Lacey🇺🇸
The Polyakov linear sigma model (PLSM) is used to investigate the respective influence of a finite volume and a magnetic field on the quark-hadron phase boundary in the plane of baryon chemical potential ( $μ_{B}$ ) vs. temperature ( $T$ ) of the QCD phase diagram. The calculated results indicate sizable shifts of the quark-hadron phase boundary to lower values of $(μ_{B} and T)$ for increasing magnetic field strength, and an opposite shift to higher values of $(μ_{B} and T)$ for decreasing system volume. Such shifts could have important implications for extraction of the thermodynamic properties of the QCD phase diagram from heavy ion data.
nucl-thhep-phJ.Phys.G(2017)·33 citations
04
Pairing reentrance in warm rotating $^{104}$ Pd nucleus
N. Quang Hung · N. Dinh Dang · B.K. Agrawal · V.M. Datar · A. Mitra · D. R. Chakrabarty
Pairing reentrance phenomenon in the warm rotating $^{104}$ Pd nucleus is studied within the Bardeen-Cooper-Schrieffer (BCS)-based approach (the FTBCS1). The theory takes into account the effect of quasiparticle number fluctuations on the pairing field at finite temperature and angular momentum within the pairing model plus noncollective rotation along the symmetry axis. The numerical calculations for the pairing gaps and nuclear level densities (NLD), of which an anomalous enhancement has been experimentally observed at low excitation energy $E^{*}$ and high angular momentum $J$ , show that the pairing reentrance is seen in the behavior of pairing gap obtained within the FTBCS1 at low $E$ and high $J$ . This leads to the enhancement of the FTBCS1 level densities, in good agreement with the experimental observation. This agreement indicates that the observed enhancement of the NLD might be the first experimental detection of the pairing reentrance in a finite nucleus.
nucl-thnucl-ex0 citations
05
Introduction to low-momentum effective interactions with Brown-Rho scaling and three-nucleon forces
T. T. S. Kuo🇺🇸 · J. W. Holt🇺🇸 · E. Osnes🇳🇴
Model-space effective interactions $V_{e f f}$ derived from free-space nucleon-nucleon interactions $V_{N N}$ are reviewed. We employ a double decimation approach: first we extract a low-momentum interaction $V_{l o w - k}$ from $V_{N N}$ using a $T$ -matrix equivalence decimation method. Then $V_{e f f}$ is obtained from $V_{l o w - k}$ by way of a folded-diagram effective interaction method. For decimation momentum $Λ ≃ 2 f m^{- 1}$ , the $V_{l o w - k}$ interactions derived from different realistic $V_{N N}$ models are nearly model independent, and so are the resulting shell-model effective interactions. For nucleons in a low-density nuclear medium like valence nucleons near the nuclear surface, such effective interactions derived from free-space $V_{N N}$ are satisfactory in reproducing experimental nuclear properties. But it is not so for nucleons in a nuclear medium with density near or beyond nuclear matter saturation density. In this case it may be necessary to include the effects from Brown-Rho (BR) scaling of hadrons and/or three-nucleon forces $V_{3 N}$ , effectively changing the free-space $V_{N N}$ into a density-dependent one. The density-dependent effects from BR scaling and $V_{3 N}$ are compared with those from empirical Skyrme effective interactions.
nucl-thPhys.Scripta(2016)·13 citations
06
Modification of magicity towards the dripline and its impact on electron-capture rates for stellar core-collapse
Ad. R. Raduta🇷🇴 · F. Gulminelli🇫🇷 · M. Oertel🇫🇷
The importance of microphysical inputs from laboratory nuclear experiments and theoretical nuclear structure calculations in the understanding of the core collapse dynamics, and the subsequent supernova explosion, is largely recognized in the recent literature. In this work, we analyze the impact of the masses of very neutron rich nuclei on the matter composition during collapse, and the corresponding electron capture rate. To this aim, we introduce an empirical modification of the popular Duflo-Zuker mass model to account for possible shell quenching far from stability, and study the effect of the quenching on the average electron capture rate. We show that the preeminence of the $N = 50$ and $N = 82$ closed shells in the collapse dynamics is considerably decreased if the shell gaps are reduced in the region of $^{78}$ Ni and beyond. As a consequence, local modifications of the overall electron capture rate up to 30\% can be expected, with integrated values strongly dependent on the stiffness of magicity quenching and progenitor mass and potential important consequences on the entropy generation, the neutrino emissivity, and the mass of the core at bounce. Our work underlines the importance of new experimental measurements in this region of the nuclear chart, the most crucial information being the nuclear mass and the Gamow-Teller strength. Reliable microscopic calculations of the associated elementary rate, in a wide range of temperatures and electron densities, optimized on these new empirical information, will be additionally needed to get quantitative predictions of the collapse dynamics.
nucl-thPRC(2016)·23 citations
07
Bohr Hamiltonian with Hulth?en plus Ring shaped potential for triaxial nuclei
M. Chabab · A. Lahbas · M. Oulne
In this paper, we solve the eigenvalues and eigenvectors problem with Bohr collective Hamil- tonian for triaxial nuclei. The ? beta part of the collective potential is taken to be equal to Hulth?en potential while the gamma part is defined by a new generalized potential obtained from a ring shaped one. Analytical expressions for spectra and wave functions are derived by means of a recent version of the asymptotic iteration method and the usual approximations. The calculated energies and B(E2) transition rates are compared with experimental data and the available theoretical results in the literature.
nucl-thEPJA(2015)·47 citations
08
Closed analytical solutions of Bohr Hamiltonian with Manning-Rosen potential model
M. Chabab · A. Lahbas · M. Oulne
In the present work, we have obtained closed analytical expressions for eigenvalues and eigenfunctions of the Bohr Hamiltonian with the Manning-Rosen potential for {\gamma}-unstable nuclei as well as exactly separable rotational ones with {\gamma}=0. Some heavy nuclei with known \b{eta} and {\gamma} bandheads have been fitted by using two parameters in the {\nu}-unstable case and three parameters in the axially symmetric prolate deformed one. A good agreement with experimental data has been achieved.
nucl-thIJMPE(2015)·32 citations
09
New integral formula and its applications to light nucleus reactions
Xiaojun Sun🇨🇳 · Jingshang Zhang🇨🇳
A new integral formula, which has not been compiled in any integral tables or mathematical softwares, is proposed to obtain the analytical energy-angular spectra of the particles that are sequentially emitted from the discrete energy levels of the residual nuclei in the statistical theory of light nucleus reaction (STLN). In the cases of the neutron induced light nucleus reactions, the demonstration of the kinetic energy conservation in the sequential emission processes becomes straightforward thanks to this new integral formula and it is also helpful to largely reduce the volume of file-6 in nuclear reaction databases. Furthermore, taking p+ $^{9}$ Be reaction at 18 MeV as an example, this integral formula is extended to calculate the energy-angular spectra of the sequentially emitted neutrons for proton induced light nucleus reactions in the frame of STLN.
nucl-thPRC(2015)·5 citations
10
Pion Photo- and Electroproduction and the Chiral MAID Interface
M. Hilt🇩🇪 · B. C. Lehnhart🇩🇪 · S. Scherer🇩🇪 · L. Tiator🇩🇪
We discuss the extended on-mass-shell scheme for manifestly Lorentz-invariant baryon chiral perturbation theory. We present a calculation of pion photo- and electroproduction up to and including order $q^{4}$ . The low-energy constants have been fixed by fitting experimental data in all available reaction channels. Our results can be accessed via a web interface, the so-called chiral MAID (http://www.kph.uni-mainz.de/MAID/chiralmaid/).
nucl-thhep-phnucl-exJPS Conf.Proc.(2016)·1 citation
11
Theoretical studies of possible toroidal high-spin isomers in the light-mass region
Andrzej Staszczak · Cheuk-Yin Wong
We review our theoretical knowledge of possible toroidal high-spin isomers in the light mass region in 28 $\leq$ $A$ $\leq$ 52 obtained previously in cranked Skyrme-Hartree-Fock calculations. We report additional toroidal high-spin isomers in $^{56}$ Ni with $I$ =114 $ℏ$ and 140 $ℏ$ , which follow the same (multi-particle)--(multi-hole) systematics as other toroidal high-spin isomers. We examine the production of these exotic nuclei by fusion of various projectiles on $^{20}$ Ne or $^{28}$ Si as an active target in time-projection-chamber (TCP) experiments.
nucl-thEPJ Web Conf.(2016)·6 citations
12
Thermalization of a boost-invariant non-Abelian plasma: Holographic approach with boundary sourcing
Loredana Bellantuono🇮🇹 · Pietro Colangelo🇮🇹 · Fulvia De Fazio🇮🇹 · Floriana Giannuzzi🇮🇹
In a holographic approach, the evolution of a 4D strongly coupled non-Abelian plasma towards equilibrium can be studied investigating a 5D gravitational dual. The process driving the plasma out-of-equilibrium can be described by boundary sourcing, a deformation of the boundary metric; the analysis of the late-time dynamics allows to understand how the hydrodynamic regime settles in. We apply the method to a boost-invariant case, considering the effects of different quenches, solving the Einstein equations in the bulk and studying the time-dependence of observables such as the effective temperature, the energy density and the pressures. The main outcome is that, if the effective temperature of the system when the quench is switched off is $T_{e f f} (τ^{*}) = 500$ MeV, thermalization is reached within a time of $O$ (1 fm/c), an important information if the case of the QCD plasma produced in relativistic heavy ion collisions is considered.
↳ hep-phhep-thnucl-thPoS(2015)·1 citation
13
On effective Chern-Simons Term induced by a Local CPT-Violating Coupling using $γ_{5}$ in Dimensional Regularization
Ruggero Ferrari🇺🇸 · Mario Raciti🇮🇹
We resume a long-standing, yet not forgotten, debate on whether a Chern-Simons birefringence can be generated by a local term $b_{μ} ψ ˉ γ^{μ} γ_{5} ψ$ in the Lagrangian (where $b_{μ}$ are constants). In the present paper we implement a new way of managing $γ_{5}$ in dimensional regularization. Gauge invariance in the underlying theory (QED) is enforced by this choice of defining divergent amplitudes. We investigate the singular behavior of the vector meson two-point-function around the $m^{2} = 0$ and $p^{2} = 0$ point. We find that the coefficient of the effective Chern-Simons can be finite or zero. It depends on how one takes the limits: they cannot be interchanged due to the associate change of symmetry. For $m^{2} = 0$ we evaluate also the self-mass of the photon at the second orderin $b_{μ}$ . We find zero.
↳ hep-thastro-ph.COhep-phnucl-th2 citations
14
Magnetic response of baryon properties in a skyrmion model
Bing-Ran He🇯🇵
An axially symmetric ansatz is proposed to investigate the properties of baryon in a uniform magnetic field. The baryon number is shown to be conserved, while the baryon shape is stretched along the magnetic field. It is found that with increasing magnetic field strength, the static mass of the baryon first decreases and then increases, while the size of the baryon first increases and then decreases. Finally, in the core part of the magnetar, the equation of state strongly depends on the magnetic field, which modifies the mass limit of the magnetar.
↳ hep-phhep-latnucl-thPRD(2015)·16 citations

Affiliations

first authorsco-authorsvia INSPIRE