Nuclear Theory·nucl-th

Monday·February 2, 2015

10 papers—2 primary·8 cross-listed

01
[Submitted on 30 Jan 2015]
Shape effects on double beta decay of $^{70}$ Zn and $^{150}$ Nd in deformed shell model
R. Sahu🇮🇳 · V.K.B. Kota🇮🇳
Using deformed shell model based on Hartree-Fock intrinsic states with $^{70}$ Zn as an example and employing two realistic effective interactions, namely jj44b that produces deformed shape and JUN45 that generates spherical shape, it is demonstrated that the $0 ν$ and $2 ν$ nuclear transition matrix elements for double beta decay will reduce considerably as we go from spherical shapes to deformed shapes. This result is further substantiated by using $^{150}$ Nd as another example.
Comments:
5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1501.07674 [pdf]
1 citation
02
[Submitted on 30 Jan 2015]
Constraining and applying a generic high-density equation of state
Mark G. Alford🇺🇸 · G. F. Burgio🇮🇹 · Sophia Han🇺🇸 · Gabriele Taranto🇮🇹 · Dario Zappalà🇮🇹
We discuss the "constant speed of sound" (CSS) parametrization of the equation of state of high-density matter and its application to the field correlator method (FCM) model of quark matter. We show how observational constraints on the maximum mass and typical radius of neutron stars are expressed as constraints on the CSS parameters. We find that the observation of a $2 M_{⊙}$ star already severely constrains the CSS parameters, and is particularly difficult to accommodate if the squared speed of sound in the high-density phase is assumed to be around $1/3$ or less. We show that the FCM equation of state can be accurately represented by the CSS parametrization, which assumes a sharp transition to a high-density phase with density-independent speed of sound. We display the mapping between the FCM and CSS parameters, and see that FCM only allows equations of state in a restricted subspace of the CSS parameters.
Comments:
14 pages, 9 figures. Published version
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1501.07902 [pdf]
PRD(2015)·117 citations
03
[Submitted on 29 Jan 2015] (cross-list from hep-ph)
Dynamical evolution of the chiral magnetic effect: Applications to the quark-gluon plasma
Cristina Manuel🇪🇸 · Juan M. Torres-Rincon🇫🇷
We study the dynamical evolution of the so-called chiral magnetic effect in an electromagnetic conductor. To this end, we consider the coupled set of corresponding Maxwell and chiral anomaly equations, and we prove that these can be derived from chiral kinetic theory. After integrating the chiral anomaly equation over space in a closed volume, it leads to a quantum conservation law of the total helicity of the system. A change in the magnetic helicity density comes together with a modification of the chiral fermion density. We study in Fourier space the coupled set of anomalous equations and we obtain the dynamical evolution of the magnetic fields, magnetic helicity density, and chiral fermion imbalance. Depending on the initial conditions we observe how the helicity might be transferred from the fermions to the magnetic fields, or vice versa, and find that the rate of this transfer also depends on the scale of wavelengths of the gauge fields in consideration. We then focus our attention on the quark-gluon plasma phase, and analyze the dynamical evolution of the chiral magnetic effect in a very simple toy model. We conclude that an existing chiral fermion imbalance in peripheral heavy ion collisions would affect the magnetic field dynamics, and consequently, the charge dependent correlations measured in these experiments.
Comments:
41 pages, 14 figures, 3 appendices. Version 2: new global structure (appendix added), more explanations and additional references. Version accepted for publication in Physical Review D journal
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1501.07608 [pdf]
PRD(2015)·93 citations
04
[Submitted on 30 Jan 2015] (cross-list from nucl-ex)
High Spin Spectroscopy and Shape Evolution in 105Cd
M. Kumar Raju · D. Negi · S. Muralithar · R. P. Singh · J. A. Sheikh · G. H. Bhat · R. Kumar · Indu Bala · T. Trivedi · A. Dhal · K. Rani · R. Gurjar and 7 other authors
High spin states in 105Cd were studied using 16O beam on 92Mo reaction at an incident beam energy of 75 MeV. The level scheme of 105Cd has been observed up to an excitation energy of 10.8 MeV with the addition of 30 new gamma transitions to the previous work. Spin and parity for most of the reported levels are assigned from the DCO ratios and linear polarization measurements. The microscopic origin of the investigated band structures is discussed in the context of triaxial projected shell model. The energies of observed positive and negative parity bands agree with the predictions of the TPSM by considering triaxial deformation for the observed excited band structures. The shape evolution with increasing angular momentum is explained in the framework of Cranked Shell Model and the Total Routhian Surface calculations.
Comments:
13 pages, 16 figures, Accepted in PRC on 29th January 2015
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1501.07655 [pdf]
PRC(2015)·6 citations
05
[Submitted on 30 Jan 2015] (cross-list from math-ph)
Random Matrix Theory with U(N) Racah Algebra for Transition Strengths
V.K.B. Kota🇮🇳
For finite quantum many-particle systems, a given system, induced by a transition operator, makes transitions from its states to the states of the same system or to those of another system. Examples are electromagnetic transitions (then the initial and final systems are same), nuclear beta and double beta decay (then the initial and final systems are different), particle addition to or removal from a given system and so on. Working towards developing a complete statistical theory for transition strength densities (transition strengths multiplied by the density of states at the initial and final energies), we have started a program to derive formulas for the lower order bivariate moments of the strength densities generated by a variety of transition operators. In this paper results are presented for a transition operator that removes $k_{0}$ number of particle by considering $m$ spinless fermions in $N$ single particle states. The Hamiltonian that is $k$ -body is represented by EGUE( $k$ ) [embedded Gaussian unitary ensemble of $k$ -body interactions] and similarly the transition operator by an appropriate independent EGUE. Employing the embedding $U (N)$ algebra, finite- $N$ formulas for moments up to order four are derived and they show that in general the smoothed (with respect to energy) bivariate transition strength densities take bivariate Gaussian form. Extension of these results to particle addition operator and beta decay type operators are discussed.
Comments:
submitted for publication in the proceedings of the XVI International Conference on Symmetry Methods in Physics (SYMPHYS-XVI) held at JINR, Dubna (Moscow region, Russia) during 13-18 October 2014
Subjects:
Mathematical Physics (math-ph); math.MP (math.MP); nlin.CD (nlin.CD); Nuclear Theory (nucl-th)
arXiv:
1501.07670 [pdf]
0 citations
06
[Submitted on 30 Jan 2015] (cross-list from hep-ph)
Radiative transition of negative to positive parity nucleon
K. Azizi🇹🇷 · H. Sundu🇹🇷
We investigate the $N^{*} (1535) \to N γ$ transition in the framework of light cone QCD sum rules. In particular, using the most general form of the interpolating current for the nucleon as well as the distribution amplitudes of the photon, we calculate two transition form factors responsible for this channel and use them to evaluate the decay width and branching ratio of the transition under consideration. The result obtained for the branching fraction is in a good consistency with the experimental data.
Comments:
A typo has been corrected
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1501.07691 [pdf]
PRD(2015)·11 citations
07
[Submitted on 30 Jan 2015] (cross-list from hep-ph)
Stability of magnetized strange quark matter in the MIT bag model with the density dependent bag pressure
A. A. Isayev🇺🇦
The stability of magnetized strange quark matter (MSQM) is studied in the MIT bag model with the density dependent bag pressure. In the consistent thermodynamic description of MSQM, the quark chemical potentials, the total thermodynamic potential and the anisotropic pressure acquire the corresponding additional term proportional to the density derivative of the bag pressure. The model parameter space is determined, for which MSQM is absolutely stable, i.e., its energy per baryon is less than that of the most stable $^{56}$ Fe nucleus under the zero external pressure and vanishing temperature. It is shown that there exists the magnetic field strength $H_{u ma x}$ at which the upper bound $B_{\infty}^{u}$ on the asymptotic bag pressure $B_{\infty} \equiv B (ϱ_{B} ≫ ϱ_{0}$ ) ( $ϱ_{0}$ being the nuclear saturation density) from the absolute stability window vanishes. The value of this field, \hbox{ $H_{u ma x} \sim$ $(1$ -- $3) \cdot 1 0^{18}$ }~G, represents the upper bound on the magnetic field strength, which can be reached in a strongly magnetized strange quark star. It is clarified how the absolute stability window and upper bound on the magnetic field strength are affected by varying the parameters in the Gaussian parametrization for the density dependence of the bag pressure.
Comments:
14 pages, 2 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1501.07772 [pdf]
PRC(2015)·49 citations
08
[Submitted on 30 Jan 2015] (cross-list from hep-ph)
States generated in the $K$ -multi- $ρ$ interactions
C. W. Xiao🇩🇪
In the present work we use three-body interaction formalism to investigate the $K$ -multi- $ρ$ interactions. First, we reproduced the resonances $f_{2} (1270)$ and $K_{1} (1270)$ in the $ρρ$ and $ρ K$ two-body interactions respectively, as the clusters of the fixed center approximation. Then, we study the three-body $K - ρρ (f_{2})$ and $ρ - ρ K (K_{1})$ interactions with the fixed center approximation of the Faddeev equations. Furthermore, we extrapolate the formalism to study the four-body, five-body and six-body systems, containing one $K$ meson and multi- $ρ$ mesons. In our research, without introducing any free parameters, we generate the $K_{2} (1770)$ state in the three-body interaction with the mass of 1707 MeV and a width about 113 MeV, which are consistent with the experiments. We also find a clear resonant structure in our results of the five-body interaction, with a mass 2505 MeV and a width about 32 MeV or more, which is associated to the $K_{4} (2500)$ state, where we obtain consistent results with the experimental findings. Furthermore, we predict some new states in the other many body interactions, $K_{3} (2080)$ , $K_{5} (2670)$ (isospin $I = 1/2$ ), and $K_{4} (2640)$ (isospin $I = 3/2$ ), with uncertainties.
Comments:
Updated version: comments and references added, accepted by PRD
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1501.07834 [pdf]
PRD(2015)·3 citations
09
[Submitted on 30 Jan 2015] (cross-list from hep-ph)
An in-Medium Heavy-Quark Potential from the $Q Q ˉ$ Free Energy
Shuai Y.F. Liu🇺🇸 · Ralf Rapp🇺🇸
We investigate the problem of extracting a static potential between a quark and its antiquark in a quark-gluon plasma (QGP) from lattice-QCD computations of the singlet free energy, $F_{Q Q ˉ} (r)$ . We utilize the thermodynamic $T$ -matrix formalism to calculate the free energy from an underlying potential ansatz resummed in ladder approximation. Imaginary parts of both $Q Q ˉ$ potential-type and single-quark selfenergies are included as estimated from earlier results of the $T$ -matrix approach. We find that the imaginary parts, and in particular their (low-) energy dependence, induce marked deviations of the (real part of the) potential from the calculated free energy. When fitting lattice results of the latter, the extracted potential is characterized by significant long-range contributions from remnants of the confining force. We briefly discuss consequences of this feature for the heavy-quark transport coefficient in the QGP.
Comments:
6 pages, 3 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1501.07892 [pdf]
NPA(2015)·29 citations
10
[Submitted on 30 Jan 2015] (cross-list from hep-ph)
Glueball Decay Rates in the Witten-Sakai-Sugimoto Model
Frederic Brünner🇦🇹 · Denis Parganlija🇦🇹 · Anton Rebhan🇦🇹
We revisit and extend previous calculations of glueball decay rates in the Sakai-Sugimoto model, a holographic top-down approach for QCD with chiral quarks based on D8 probe branes in Witten's holographic model of nonsupersymmetric Yang-Mills theory. The rates for decays into two pions, two vector mesons, four pions, and the strongly suppressed decay into four pi0 are worked out quantitatively, using a range of the 't Hooft coupling which closely reproduces the decay rate of rho and omega mesons and also leads to a gluon condensate consistent with QCD sum rule calculations. The lowest holographic glueball, which arises from a rather exotic polarization of gravitons in the supergravity background, turns out to have a significantly lower mass and larger width than the two widely discussed glueball candidates f0(1500) and f0(1710). The lowest nonexotic and predominantly dilatonic scalar mode, which has a mass of 1487 MeV in the Witten-Sakai-Sugimoto model, instead provides a narrow glueball state, and we conjecture that only this nonexotic mode should be identified with a scalar glueball component of f0(1500) or f0(1710). Moreover the decay pattern of the tensor glueball is determined, which is found to have a comparatively broad total width when its mass is adjusted to around or above 2 GeV.
Comments:
38 pages, 5 figures, 9 tables; v2: minor corrections (numerical data in tables 3, 5, and 7 on excited scalar glueballs), 2 footnotes and 2 references added; v3: corrections in table 9 (extrapolations of tensor glueball decay to masses above 2 GeV)
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1501.07906 [pdf]
PRD(2015)·113 citations

Affiliations

first authorsco-authorsvia INSPIRE