tag:blogger.com,1999:blog-3854856545589311912018-04-10T05:02:39.722-07:00Nuclear TheorySite for <a href="http://communitypeerreview.blogspot.com/">Community Peer Review</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.comBlogger3990125tag:blogger.com,1999:blog-385485654558931191.post-5631434433539072762013-08-06T00:03:00.025-07:002013-08-06T00:03:56.456-07:001308.0617 (Shanshan Cao et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0617">Heavy quark dynamics and hadronization in ultra-relativistic heavy-ion<br /> collisions: collisional vs. radiative energy loss</a> [<a href="http://arxiv.org/pdf/1308.0617">PDF</a>]</h2>Shanshan Cao, Guang-You Qin, Steffen A. Bass<a name='more'></a><blockquote class="abstract">We study the dynamics of energy loss and flow of heavy quarks produced in ultra-relativistic heavy-ion collisions within the framework of a Langevin equation coupled to a (2+1)-dimensional viscous hydrodynamic model that simulates the space-time evolution of the produced hot and dense QCD matter. The classical Langevin approach is improved such that, apart from quasi-elastic scatterings, radiative energy loss is incorporated by treating gluon radiation as an additional force term. The hadronization of emitted heavy quarks is simulated via a hybrid fragmentation plus recombination model. Our calculation shows significant contribution from gluon radiation to heavy quark energy loss at high energies, and we find the recombination mechanism is important for heavy flavor meson production at intermediate energies. We present numerical results for the nuclear modification and elliptic flow of D mesons, which are consistent with measurements at both LHC and RHIC; predictions for B mesons are also provided.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0617">http://arxiv.org/abs/1308.0617</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-385485654558931191.post-22260759254175175162013-08-06T00:03:00.023-07:002013-08-06T00:03:55.719-07:001308.0736 (V. Uzhinsky)<h2 class="title"><a href="http://arxiv.org/abs/1308.0736">Toward UrQMD Model Description of pp and pC Interactions at High<br /> Energies</a> [<a href="http://arxiv.org/pdf/1308.0736">PDF</a>]</h2>V. Uzhinsky<a name='more'></a><blockquote class="abstract">It is found that UrQMD model version 3.3 does not describe NA61/SHINE Collaboration data on \pi-meson production in pp interactions at energies 20 - 80 GeV. At the same time, it describes quite well the NA49 Collaboration data on the meson production in pp and pC interactions at 158 GeV. The Collaborations do not consider feedback of \eta-meson decays. All versions of the UrQMD model assume that \eta-mesons are "stable". An inclusion of the decays into calculations leads to 2--3 % increase of the meson production which is not enough for description of the data. Possible ways of the model improvements are considered. Conclusions of the paper are: accounting of \eta-meson decays is not essential for a description of experimental data; a new tuning of the UrQMD model parameters is needed for a successful description of pp and pC interactions at high energies; inclusion of the low mass diffraction dissociation in the UrQMD model would be desirable.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0736">http://arxiv.org/abs/1308.0736</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-385485654558931191.post-66047025929959851542013-08-06T00:03:00.021-07:002013-08-06T00:03:54.836-07:001308.0752 (M. I. Gorenstein et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0752">Energy and Transverse Momentum Fluctuations in the Equilibrium Quantum<br /> Systems</a> [<a href="http://arxiv.org/pdf/1308.0752">PDF</a>]</h2>M. I. Gorenstein, M. Rybczynski<a name='more'></a><blockquote class="abstract">The fluctuations in the ideal quantum gases are studied using the strongly intensive measures $\Delta[A,B]$ and $\Sigma[A,B]$ defined in terms of two extensive quantities $A$ and $B$. In the present paper, these extensive quantities are taken as the motional variable, $A=X$, the system energy $E$ or transverse momentum $P_T$, and number of particles, $B=N$. This choice is most often considered in studying the event-by-event fluctuations and correlations in high energy nucleus-nucleus collisions. The recently proposed special normalization ensures that $\Delta$ and $\Sigma$ are dimensionless and equal to unity for fluctuations given by the independent particle model. In statistical mechanics, the grand canonical ensemble formulation within the Boltzmann approximation gives an example of independent particle model. Our results demonstrate the effects due to the Bose and Fermi statistics. Estimates of the effects of quantum statistics in the hadron gas at temperatures and chemical potentials typical for thermal models of hadron production in high energy collisions are presented. In the case of massless particles and zero chemical potential the $\Delta$ and $\Sigma$ measures are calculated analytically.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0752">http://arxiv.org/abs/1308.0752</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-385485654558931191.post-69261055569768212282013-08-06T00:03:00.019-07:002013-08-06T00:03:53.767-07:001308.0785 (E. Molnár et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0785">On the relative importance of second-order terms in relativistic<br /> dissipative fluid dynamics</a> [<a href="http://arxiv.org/pdf/1308.0785">PDF</a>]</h2>E. Molnár, H. Niemi, G. S. Denicol, D. H. Rischke<a name='more'></a><blockquote class="abstract">In Denicol et al., Phys. Rev. D 85, 114047 (2012), the equations of motion of relativistic dissipative fluid dynamics were derived from the relativistic Boltzmann equation. These equations contain a multitude of terms of second order in Knudsen number, in inverse Reynolds number, or their product. Terms of second order in Knudsen number give rise to non-hyperbolic (and thus acausal) behavior and must be neglected in (numerical) solutions of relativistic dissipative fluid dynamics. The coefficients of the terms which are of the order of the product of Knudsen and inverse Reynolds numbers have been explicitly computed in the above reference, in the limit of a massless Boltzmann gas. Terms of second order in inverse Reynolds number arise from the collision term in the Boltzmann equation, upon expansion to second order in deviations from the single-particle distribution function in local thermodynamical equilibrium. In this work, we compute these second-order terms for a massless Boltzmann gas with constant scattering cross section. Consequently, we assess their relative importance in comparison to the terms which are of the order of the product of Knudsen and inverse Reynolds numbers.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0785">http://arxiv.org/abs/1308.0785</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-385485654558931191.post-82828756483966716432013-08-06T00:03:00.017-07:002013-08-06T00:03:52.998-07:001308.0809 (M. Abu-Shady)<h2 class="title"><a href="http://arxiv.org/abs/1308.0809">Improved Nucleon Properties in the Extended Quark Sigma Model</a> [<a href="http://arxiv.org/pdf/1308.0809">PDF</a>]</h2>M. Abu-Shady<a name='more'></a><blockquote class="abstract">The quark sigma model describes the quarks interacting via exchange the pions and sigma meson fields. A new version of mesonic potential is suggested in the frame of some aspects of the quantum chromodynamics (QCD). The field equations have been solved in the mean-field approximation for the hedgehog baryon state. The obtained results are compared with previous works and other models. We conclude that the suggested mesonic potential successfully calculates nucleon properties.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0809">http://arxiv.org/abs/1308.0809</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-385485654558931191.post-5025632270008847252013-08-06T00:03:00.015-07:002013-08-06T00:03:51.926-07:001308.0904 (K. Nomura et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0904">Microscopic analysis of the octupole phase transition in Th isotopes</a> [<a href="http://arxiv.org/pdf/1308.0904">PDF</a>]</h2>K. Nomura, D. Vretenar, B. -N. Lu<a name='more'></a><blockquote class="abstract">A shape phase transition between stable octupole deformation and octupole vibrations in Th nuclei is analyzed in a microscopic framework based on nuclear density functional theory. The relativistic functional DD-PC1 is used to calculate axially-symmetric quadrupole-octupole constrained energy surfaces. Observables related to order parameters are computed using an interacting-boson Hamiltonian, with parameters determined by mapping the microscopic energy surfaces to the expectation value of the Hamiltonian in the boson condensate. The systematics of constrained energy surfaces and low-energy excitation spectra point to the occurrence of a phase transition between octupole-deformed shapes and shapes characterized by octupole-soft potentials.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0904">http://arxiv.org/abs/1308.0904</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-385485654558931191.post-22034369572650010262013-08-06T00:03:00.013-07:002013-08-06T00:03:51.169-07:001308.0922 (Luca Salasnich)<h2 class="title"><a href="http://arxiv.org/abs/1308.0922">Fermionic condensation in ultracold atoms, nuclear matter and neutron<br /> stars</a> [<a href="http://arxiv.org/pdf/1308.0922">PDF</a>]</h2>Luca Salasnich<a name='more'></a><blockquote class="abstract">We investigate the Bose-Einstein condensation of fermionic pairs in three different superfluid systems: ultracold and dilute atomic gases, bulk neutron matter, and neutron stars. In the case of dilute gases made of fermionic atoms the average distance between atoms is much larger than the effective radius of the inter-atomic potential. Here the condensation of fermionic pairs is analyzed as a function of the s-wave scattering length, which can be tuned in experiments by using the technique of Feshbach resonances from a small and negative value (corresponding to the Bardeen-Cooper-Schrieffer (BCS) regime of Cooper Fermi pairs) to a small and positive value (corresponding to the regime of the Bose-Einstein condensate (BEC) of molecular dimers), crossing the unitarity regime where the scattering length diverges. In the case of bulk neutron matter the s-wave scattering length of neutron-neutron potential is negative but fixed, and the condensate fraction of neutron-neutron pairs is studied as a function of the total neutron density. Our results clearly show a BCS-quasiunitary-BCS crossover by increasing the neutron density. Finally, in the case of neutron stars, where again the neutron-neutron scattering length is negative and fixed, we determine the condensate fraction as a function of the distance from the center of the neutron star, finding that the maximum condensate fraction appears in the crust of the neutron star.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0922">http://arxiv.org/abs/1308.0922</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-385485654558931191.post-2126306656033587682013-08-06T00:03:00.011-07:002013-08-06T00:03:50.311-07:001308.0939 (S. Ramanan et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0939">BEC-BCS Crossover in Neutron Matter with Renormalization Group based<br /> Effective Interactions</a> [<a href="http://arxiv.org/pdf/1308.0939">PDF</a>]</h2>S. Ramanan, M. Urban<a name='more'></a><blockquote class="abstract">We study pure neutron matter in the BEC-BCS crossover regime using renormalization group based low-momentum interactions within the Nozi\`eres-Schmitt-Rink framework. This is an attempt to go beyond the mean field description for low-density matter. We work in the basis of so-called Weinberg eigenvectors where the operator $G_0V$ is diagonal, which proves to be an excellent choice that allows one to use non-local interactions in a very convenient way. We study the importance of correlations as a function of density. We notice that there is a significant reduction of the BCS critical temperature at low-densities as the neutron matter approaches the unitary limit.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0939">http://arxiv.org/abs/1308.0939</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-385485654558931191.post-34850502108615233852013-08-06T00:03:00.009-07:002013-08-06T00:03:49.442-07:001308.0947 (Dmitri Diakonov et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0947">A theory of baryon resonances at large N_c</a> [<a href="http://arxiv.org/pdf/1308.0947">PDF</a>]</h2>Dmitri Diakonov, Victor Petrov, Alexey A. Vladimirov<a name='more'></a><blockquote class="abstract">At large number of colors, N_c quarks in baryons are in a mean field of definite space and flavor symmetry. We write down the general Lorentz and flavor structure of the mean field, and derive the Dirac equation for quarks in that field. The resulting baryon resonances exhibit an hierarchy of scales: The crude mass is O(N_c), the intrinsic quark excitations are O(1), and each intrinsic quark state entails a finite band of collective excitations that are split as O(1/N_c). We build a (new) theory of those collective excitations, where full dynamics is represented by only a few constants. In a limiting (but unrealistic) case when the mean field is spherically-and flavor-symmetric, our classification of resonances reduces to the SU(6) classification of the old non-relativistic quark model. Although in the real world N_c is only three, we obtain a good accordance with the observed resonance spectrum up to 2 GeV.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0947">http://arxiv.org/abs/1308.0947</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-385485654558931191.post-20967141691947530742013-08-06T00:03:00.007-07:002013-08-06T00:03:48.617-07:001308.0966 (Zeki C. Kuruoglu)<h2 class="title"><a href="http://arxiv.org/abs/1308.0966">Bateman method for two-body scattering without partial-wave<br /> decomposition</a> [<a href="http://arxiv.org/pdf/1308.0966">PDF</a>]</h2>Zeki C. Kuruoglu<a name='more'></a><blockquote class="abstract">The use of Bateman method for solving the two-variable version of the Lippmann-Schwinger equation without recourse to partial-wave decomposition is investigated. Bateman method is based on a special kind of interpolation of the momentum representation of the potential on a multi-variate grid. A suitable scheme for the generation of a multi-variate Cartesian grid is described. The method is tested in the nucleon-nucleon scattering employing a model two-nucleon potential. Our results show that the Bateman method is capable of producing quite accurate solutions with relatively small number of grid points.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0966">http://arxiv.org/abs/1308.0966</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-385485654558931191.post-73755011843599638972013-08-06T00:03:00.005-07:002013-08-06T00:03:47.565-07:001308.1008 (X. Viñas et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.1008">Density dependence of the symmetry energy from neutron skin thickness in<br /> finite nuclei</a> [<a href="http://arxiv.org/pdf/1308.1008">PDF</a>]</h2>X. Viñas, M. Centelles, X. Roca-Maza, M. Warda<a name='more'></a><blockquote class="abstract">The density dependence of the symmetry energy around saturation density, characterized by the slope parameter L, is studied using information provided by the neutron skin thickness in finite nuclei. An estimate for L is obtained from experimental data on neutron skins extracted from antiprotonic atoms. We also discuss the ability of parity-violating elastic electron scattering to obtain information on the neutron skin thickness in 208Pb and to constrain the density dependence of the nuclear symmetry energy. The size and shape of the neutron density distribution of 208Pb predicted by mean-field models is briefly addressed. We conclude with a comparative overview of the L values predicted by several existing determinations.</blockquote>View original: <a href="http://arxiv.org/abs/1308.1008">http://arxiv.org/abs/1308.1008</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-385485654558931191.post-88989479252759074232013-08-06T00:03:00.003-07:002013-08-06T00:03:46.574-07:001308.1025 (Dennis Bonatsos et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.1025">Bohr Hamiltonian with deformation-dependent mass term for the Kratzer<br /> potential</a> [<a href="http://arxiv.org/pdf/1308.1025">PDF</a>]</h2>Dennis Bonatsos, P. E. Georgoudis, N. Minkov, D. Petrellis, C. Quesne<a name='more'></a><blockquote class="abstract">The Deformation Dependent Mass (DDM) Kratzer model is constructed by considering the Kratzer potential in a Bohr Hamiltonian, in which the mass is allowed to depend on the nuclear deformation, and solving it by using techniques of supersymmetric quantum mechanics (SUSYQM), involving a deformed shape invariance condition. Analytical expressions for spectra and wave functions are derived for separable potentials in the cases of gamma-unstable nuclei, axially symmetric prolate deformed nuclei, and triaxial nuclei, implementing the usual approximations in each case. Spectra and B(E2) transition rates are compared to experimental data. The dependence of the mass on the deformation, dictated by SUSYQM for the potential used, moderates the increase of the moment of inertia with deformation, removing a main drawback of the model.</blockquote>View original: <a href="http://arxiv.org/abs/1308.1025">http://arxiv.org/abs/1308.1025</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-385485654558931191.post-89738343057668638732013-08-06T00:03:00.001-07:002013-08-06T00:03:45.862-07:001308.1047 (Andrei Neacsu et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.1047">Study of Nuclear Effects in the Computation of the 0νββ<br /> Decay Matrix Elements</a> [<a href="http://arxiv.org/pdf/1308.1047">PDF</a>]</h2>Andrei Neacsu, Sabin Stoica<a name='more'></a><blockquote class="abstract">We analyse the effects that different nuclear structure approximations associated with the short range correlations (SRC), finite nucleon size (FNS), higher order terms in the nucleon currents (HOC) and with some nuclear input parameters, have on the values of the nuclear matrix elements (NMEs) for the neutrinoless double beta (0{\nu}{\beta}{\beta}) decay. The calculations are performed with a new Shell Model(ShM) code which allows a fast computation of the two-body matrix elements of the transition operators. The treatment of SRC, FNS and HOC and include the use of quenched or unquenched values for the axial vector coupling constant produce the most important effects on the NMEs values. Equivalent effects of some of these approximations are also possible, which may lead (accidentally) to close final results. We found that the cummulative effect of all these nuclear ingredients on the calculated nuclear matrix elements NMEs is significant. Since the NMEs values are often obtained with different approximations and/or with different input parameters, a convergent view point on their inclusion/neglection and an uniformization of the calculations are needed, in order to enter in an era of precision concerning the computation of the NMEs for double beta deacay.</blockquote>View original: <a href="http://arxiv.org/abs/1308.1047">http://arxiv.org/abs/1308.1047</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-385485654558931191.post-27183520623270459282013-08-05T00:02:00.017-07:002013-08-05T00:02:53.714-07:001308.0164 (Ralf-Arno Tripolt et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0164">The Effect of Fluctuations on the QCD Critical Point in a Finite Volume</a> [<a href="http://arxiv.org/pdf/1308.0164">PDF</a>]</h2>Ralf-Arno Tripolt, Jens Braun, Bertram Klein, Bernd-Jochen Schaefer<a name='more'></a><blockquote class="abstract">We investigate the effect of a finite volume on the critical behavior of the theory of the strong interaction (QCD) by means of a quark-meson model for two quark flavors. In particular, we analyze the effect of a finite volume on the location of the critical point in the phase diagram existing in our model. In our analysis, we take into account the effect of long-range fluctuations with the aid of renormalization group techniques. We find that these quantum and thermal fluctuations, absent in mean-field studies, play an import role for the dynamics in a finite volume. We show that the critical point is shifted towards smaller temperatures and larger values of the quark chemical potential if the volume size is decreased. This behavior persists for antiperiodic as well as periodic boundary conditions for the quark fields as used in many lattice QCD simulations.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0164">http://arxiv.org/abs/1308.0164</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-385485654558931191.post-71619778491187371222013-08-05T00:02:00.015-07:002013-08-05T00:02:49.296-07:001308.0347 (Lowell S. Brown et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0347">Field Theory of the d+t -> n+alpha Reaction Dominated by a 5He* Unstable<br /> Particle</a> [<a href="http://arxiv.org/pdf/1308.0347">PDF</a>]</h2>Lowell S. Brown, Gerald M. Hale<a name='more'></a><blockquote class="abstract">An effective, non-relativistic field theory for low-energy d+t -> n+alpha reaction is presented. The theory assumes that the reaction is dominated by an intermediate 5He* unstable spin 3/2+ resonance. It involves two parameters in the coupling of the d+t and n+alpha particles to the unstable resonant state, and the resonance energy level -- only three real parameters in all. All Coulomb corrections to this process are computed. The resultant field theory is exactly solvable and provides an excellent description of the d+t fusion process.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0347">http://arxiv.org/abs/1308.0347</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-385485654558931191.post-33605910704706242502013-08-05T00:02:00.013-07:002013-08-05T00:02:45.056-07:001308.0348 (Gerald M. Hale et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0348">Effective field theory as a limit of R-matrix theory for light nuclear<br /> reactions</a> [<a href="http://arxiv.org/pdf/1308.0348">PDF</a>]</h2>Gerald M. Hale, Lowell S. Brown, Mark W. Paris<a name='more'></a><blockquote class="abstract">We study the zero channel radius limit of Wigner's R-matrix theory for two cases, and show that it corresponds to non-relativistic effective quantum field theory. We begin with the simple problem of single-channel n-p elastic scattering in the 1S0 channel. The dependence of the R matrix width and level energy on the channel radius, "a" for fixed scattering length a0 and effective range r0 is determined. It is shown that these quantities have a simple pole for a critical value of the channel radius. The 3H(d,n)4He reaction cross section, analyzed with a two-channel effective field theory in the previous paper, is then examined using a two-channel, single-level R-matrix parametrization. The resulting S matrix is shown to be identical in these two representations in the limit that R-matrix channel radii are taken to zero. This equivalence is established by giving the relationship between the low-energy constants of the effective field theory (couplings and mass) and the R-matrix parameters (reduced width amplitudes and level energy). An excellent three-parameter fit to the observed astrophysical factor S is found for "unphysical" values of the reduced widths.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0348">http://arxiv.org/abs/1308.0348</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-385485654558931191.post-1352798082547270462013-08-05T00:02:00.011-07:002013-08-05T00:02:44.030-07:001308.0364 (Xinle Shang et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0364">The FFLO state with angle dependent Gap in Asymmetric Nuclear Matter</a> [<a href="http://arxiv.org/pdf/1308.0364">PDF</a>]</h2>Xinle Shang, Wei Zuo<a name='more'></a><blockquote class="abstract">We consider the FFLO and ADG state together within the same model for the asymmetric nuclear matter. The arbitrary angles between the Cooper pair momentum and the symmetry axis are studied. We find the favored angle is either 0 or pi/2 which correspond to FFLO-ADG-Orthogonal and FFLO-ADG-Parallel state respectively. Furthermore, the FFLO-ADG-Orthogonal settles at weakly asymmetric case, while the FFLO-ADG-Orthogonal are favored for large asymmetry. The critical isospin-asymmetry alpha_{c}, where superfluid vanishes, increases largely by considering the Cooper pair momentum.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0364">http://arxiv.org/abs/1308.0364</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-385485654558931191.post-8243066963280247812013-08-05T00:02:00.009-07:002013-08-05T00:02:43.412-07:001308.0392 (Yoshiko Kanada-En'yo)<h2 class="title"><a href="http://arxiv.org/abs/1308.0392">Cluster states and monopole transitions in $^{16}$O</a> [<a href="http://arxiv.org/pdf/1308.0392">PDF</a>]</h2>Yoshiko Kanada-En'yo<a name='more'></a><blockquote class="abstract">Cluster structures and monopole transitions in positive parity states of $^{16}$O were investigated based on the generator coordinate method calculation of an extended $^{12}$C+$\alpha$ cluster model. The ground and excited states of a $^{12}$C cluster are taken into account by using $^{12}$C wave functions obtained with the method of antisymmetrized molecular dynamics. The $0^+_2$ state of $^{16}$O and its rotational members, the $2^+_1$ and $4^+_1$ states are described well by the cluster states dominated by the $^{12}$C($0^+_1$)+$\alpha$ structure. Above the $^{12}$C($0^+_2$)+$\alpha$ threshold energy, we obtained a $0^+$ state having the $^{12}$C($0^+_2$)+$\alpha$ cluster structure, which is considered to be a candidate for the $4\alpha$ cluster gas state. The band structures were discussed based on the calculated $E2$ transition strength. Isoscalar Monopole excitations from the ground state were also discussed.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0392">http://arxiv.org/abs/1308.0392</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-385485654558931191.post-11540118935807413082013-08-05T00:02:00.007-07:002013-08-05T00:02:42.449-07:001308.0418 (Hirotaka Shimoyama et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0418">Di-neutron correlation in monopole two-neutron transfer modes in Sn<br /> isotope chain</a> [<a href="http://arxiv.org/pdf/1308.0418">PDF</a>]</h2>Hirotaka Shimoyama, Masayuki Matsuo<a name='more'></a><blockquote class="abstract">We study microscopic structures of monopole pair vibrational modes and associated two-neutron transfer amplitudes in neutron-rich Sn isotopes by means of the linear response formalism of the quasiparticle random phase approximation(QRPA). For this purpose we introduce a method to decompose the transfer amplitudes with respect to two-quasiparticle components of the QRPA eigen mode. It is found that pair-addition ibrational modes in neutron-rich $^{132-140}$Sn and the pair rotational modes in $^{142-150}$Sn are commonly characterized by coherent contributions of quasaiparticle states having high orbital angular momenta $l \gesim 5$, which suggests transfer of a spatially correlated neutron pair. The calculation also predicts a high-lying pair vibration, the giant pair vibration, emerging near the one-neutron separation energy in $^{110-130}$Sn, and we find that they have the same di-neutron characters as that of the low-lying pair vibration in $^{132-140}$Sn.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0418">http://arxiv.org/abs/1308.0418</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-385485654558931191.post-69969623927727427442013-08-05T00:02:00.005-07:002013-08-05T00:02:41.655-07:001308.0424 (Kenichi Yoshida)<h2 class="title"><a href="http://arxiv.org/abs/1308.0424">Spin-isospin response of deformed neutron-rich nuclei in a<br /> self-consistent Skyrme energy-density-functional approach</a> [<a href="http://arxiv.org/pdf/1308.0424">PDF</a>]</h2>Kenichi Yoshida<a name='more'></a><blockquote class="abstract">We develop a new framework of the self-consistent deformed proton-neutron quasiparticle-random-phase approximation (pnQRPA), formulated in the Hartree-Fock-Bogoliubov (HFB) single-quasiparticle basis. The same Skyrme force is used in both the HFB and pnQRPA calculations except in the proton-neutron particle-particle channel, where an S=1 contact force is employed. Numerical application is performed for Gamow-Teller (GT) strength distributions and $\beta$-decay rates in the deformed neutron-rich Zr isotopes located around the path of the rapid-neutron-capture process nucleosynthesis. It is found that the GT strength distributions are fragmented due to deformation. Furthermore we find that the momentum-dependent terms in the particle-hole residual interaction leads to a stronger collectivity of the GT giant resonance. The T=0 pairing enhances the low-lying strengths cooperatively with the T=1 pairing correlation, which shortens the $\beta$-decay half lives by at most an order of magnitude. The new calculation scheme reproduces well the observed isotopic dependence of the $\beta$-decay half lives of deformed $^{100-110}$Zr isotopes.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0424">http://arxiv.org/abs/1308.0424</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-385485654558931191.post-21142597461680472572013-08-05T00:02:00.003-07:002013-08-05T00:02:40.566-07:001308.0460 (P. K. Rath et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0460">Uncertainties in neutrinoless $ββ$ decay transition matrix<br /> elements within mechanisms involving light Majorana neutrinos, classical<br /> Majorons and sterile neutrinos</a> [<a href="http://arxiv.org/pdf/1308.0460">PDF</a>]</h2>P. K. Rath, R. Chandra, K. Chaturvedi, P. Lohani, P. K. Raina, J. G. Hirsch<a name='more'></a><blockquote class="abstract">In the PHFB model, uncertainties in the nuclear transition matrix elements for the neutrinoless double-$\beta $ decay of $\ ^{94,96}$Zr, $^{98,100}$Mo, $^{104}$Ru, $^{110}$Pd, $^{128,130}$Te and $^{150}$Nd isotopes within mechanisms involving light Majorana neutrinos, classical Majorons and sterile neutrinos are statistically estimated by considering sets of sixteen (twenty-four) matrix elements calculated with four different parametrization of the pairing plus multipolar type of effective two-body interaction, two sets of form factors and two (three) different parameterizations of Jastrow type of short range correlations. In the mechanisms involving the light Majorana neutrinos and classical Majorons, the maximum uncertainty is about 15% and in the scenario of sterile neutrinos, it varies in between approximately 4 (9)%--20 (36)% without(with) Jastrow short range correlations with Miller-Spencer parametrization, depending on the considered mass of the sterile neutrinos.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0460">http://arxiv.org/abs/1308.0460</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-385485654558931191.post-54943987570450258742013-08-05T00:02:00.001-07:002013-08-05T00:02:39.461-07:001308.0513 (Xiao-Tao He et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0513">Rotation and alignment of high-$j$ orbitals in transfermium nuclei</a> [<a href="http://arxiv.org/pdf/1308.0513">PDF</a>]</h2>Xiao-Tao He, Zhen-Hua Zhang, Jin-Yan Zeng, En-Guang Zhao, Zhong-Zhou Ren, Werner Scheid, Shan-Gui Zhou<a name='more'></a><blockquote class="abstract">The structure of nuclei with $Z\sim100$ is investigated systematically by the Cranked Shell Model (CSM) with pairing correlations treated by a Particle-Number Conserving (PNC) method. In the PNC method, the particle number is conserved and the Pauli blocking effects are taken into account exactly. By fitting the experimental single-particle spectra in these nuclei, a new set of Nilsson parameters ($\kappa$ and $\mu$) is proposed. The experimental kinematic moments of inertia and the band-head energies are reproduced quite well by the PNC-CSM calculations. The band crossing, the effects of high-$j$ intruder orbitals and deformation are discussed in detail.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0513">http://arxiv.org/abs/1308.0513</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-385485654558931191.post-9420453548206406522013-08-04T00:04:00.021-07:002013-08-04T00:04:17.349-07:001308.0005 (Sameer M. Ikhdair et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0005">Dirac bound state solutions of spherically ring-shaped q-deformed<br /> Woods-Saxon potential for any L-state</a> [<a href="http://arxiv.org/pdf/1308.0005">PDF</a>]</h2>Sameer M. Ikhdair, Majid Hamzavi<a name='more'></a><blockquote class="abstract">Approximate bound state solutions of the Dirac equation with -deformed Woods-Saxon plus a new generalized ring-shaped potential are obtained for any arbitrary L-state. The energy eigenvalue equation and corresponding two-component wave function are calculated by solving the radial and angular wave equations within a shortcut of the Nikiforov-Uvarov method. The solutions of the radial and polar angular parts of the wave function are expressed in terms of the Jacobi polynomials. A new approximation being expressed in terms of the potential parameters is carried out to deal with the strong singular centrifugal potential term L(L+1)/r^2. Under some limitations, we can obtain solution for the ring-shaped Hulth\'en potential and the standard usual spherical Woods-Saxon potential (q=1).</blockquote>View original: <a href="http://arxiv.org/abs/1308.0005">http://arxiv.org/abs/1308.0005</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-385485654558931191.post-7161890915467942972013-08-04T00:04:00.019-07:002013-08-04T00:04:16.520-07:001308.0020 (Ariel R. Zhitnitsky)<h2 class="title"><a href="http://arxiv.org/abs/1308.0020">Conformal window in QCD for large numbers of colours and flavours</a> [<a href="http://arxiv.org/pdf/1308.0020">PDF</a>]</h2>Ariel R. Zhitnitsky<a name='more'></a><blockquote class="abstract">We conjecture that the phase transitions in QCD at large number of colours $N\gg 1$ is triggered by the drastic change in $\theta$ behaviour. The conjecture is motivated by the holographic model of QCD where confinement -deconfinement phase transition indeed happens precisely at temperature $T=T_c$ where $\theta$ dependence experiences a sudden change in behaviour: from $N^2\cos(\theta/N)$ at $T<T_c$ to $\cos\theta\exp(-N)$ at $T>T_c$. This conjecture is also supported by recent lattice studies. We employ this conjecture to study a possible phase transition as a function of $\kappa\equiv N_f/N$ from confinement to conformal phase in the Veneziano limit $N_f\sim N$ when number of flavours and colours are large, but the ratio $\kappa$ is finite. Technically, we consider an operator which gets its expectation value solely from nonperturbative instaton effects. When $\kappa$ exceeds some critical value $\kappa> \kappa_c$ the integral over instanton size is dominated by small-size instatons, making the instanton computations reliable with expected $\exp(-N)$ behaviour. However, when $\kappa<\kappa_c$, the integral over instaton size is dominated by large-size instantons, and the instanton expansion breaks down. This regime with $\kappa<\kappa_c$ corresponds to the confinement phase. We also compute the variation of the critical $\kappa_c(T, \mu)$ when the temperature and chemical potential $T, \mu \ll \Lambda_{QCD}$ slightly vary. We also discuss the scaling $(x_i-x_j)^{-\gamma_{\rm det}}$ in the conformal phase.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0020">http://arxiv.org/abs/1308.0020</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-385485654558931191.post-63100156090460006692013-08-04T00:04:00.017-07:002013-08-04T00:04:15.001-07:001308.0031 (J. Hooker et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0031">Efficacy of crustal superfluid neutrons in pulsar glitch models</a> [<a href="http://arxiv.org/pdf/1308.0031">PDF</a>]</h2>J. Hooker, W. G. Newton, Bao-An Li<a name='more'></a><blockquote class="abstract">Within the framework of recent hydrodynamic models of pulsar glitches, we explore systematically the dependence on the stiffness of the nuclear symmetry energy at saturation density $L$, of the fractional moment of inertia of the pinned neutron superfluid in the crust $G$ and the initial post-glitch relative acceleration of the crust $K$, both of which are confronted with observational constraints from the Vela pulsar. We allow for a variable fraction of core superfluid neutrons coupled to the crust on glitch rise timescales, $Y_{\rm g}$. We assess whether the crustal superfluid neutrons are still a tenable angular momentum source to explain the Vela glitches when crustal entrainment is included. The observed values $G$ and $K$ are found to provide nearly orthogonal constraints on the slope of the symmetry energy, and thus taken together offer potentially tight constraints on the equation of state. However, when entrainment is included at the level suggested by recent microscopic calculations, the model is unable to reproduce the observational constraints on $G$ and $K$ simultaneously, and is limited to $L>100$ MeV and $Y_{\rm g} \approx 0$ when $G$ is considered alone. One solution is to allow the pinned superfluid vortices to penetrate the outer crust, which leads to a constraint of $L\lesssim 45$ MeV and $Y_{\rm g} \lesssim 0.04$ when $G$ and $K$ are required to match observations simultaneously. When one allows the pinned vortices to penetrate into the crust by densities of up to 0.082 fm$^{-3}$ above crust-core transition density (a total density of 0.176 fm$^{-3}$) for L=30 MeV, and 0.048 fm$^{-3}$ above crust-core transition density (a total density of 0.126 fm$^{-3}$) for L=60 MeV, the constraint on $G$ is satisfied for \emph{any} value of $Y_{\rm g}$. We discuss the implications of these results for crust-initiated glitch models.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0031">http://arxiv.org/abs/1308.0031</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0