Nuclear Theory·nucl-th

Tuesday·November 3, 2015

12 papers—7 primary·5 cross-listed

01
Observables of non-equilibrium phase transition
Boris Tomasik🇸🇰 · Martin Schulc🇨🇿 · Ivan Melo🇸🇰 · Renata Kopecna🇨🇿
A rapidly expanding fireball which undergoes first-order phase transition will supercool and proceed via spinodal decomposition. Hadrons are produced from the individual fragments as well as the left-over matter filling the space between them. Emission from fragments should be visible in rapidity correlations, particularly of protons. In addition to that, even within narrow centrality classes, rapidity distributions will be fluctuating from one event to another in case of fragmentation. This can be identified with the help of Kolmogorov-Smirnov test. Finally, we present a method which allows to sort events with varying rapidity distributions in such a way, that events with similar rapidity histograms are grouped together.
nucl-thhep-exhep-phEPJA(2016)·1 citation
02
Nuclear Matrix Elements for Double-Beta Decay
Jonathan Engel🇺🇸
Recent progress in nuclear-structure theory has been dramatic. I describe recent and future applications of ab initio calculations and the generator coordinate method to double-beta decay. I also briefly discuss the old and vexing problem of the renormalization of the weak nuclear axial-vector coupling constant "in medium" and plans to resolve it.
nucl-th0 citations
03
Multi-Nucleon Exchange in Quasi-Fission Reactions
S. Ayik · B. Yilmaz · O. Yilmaz
Nucleon exchange mechanism is investigated in the central collisions of $^{40}$ Ca + $^{238}$ U and $^{48}$ Ca + $^{238}$ U systems near the quasi-fission regime in the framework of the Stochastic Mean-Field (SMF) approach. Sufficiently below the fusion barrier, di-nuclear structure in the collisions is maintained to a large extend. Consequently, it is possible to describe nucleon exchange as a diffusion process familiar from deep-inelastic collisions. Diffusion coefficients for proton and neutron exchange are determined from the microscopic basis of the SMF approach in the semi-classical framework. Calculations show that after a fast charge equilibration the system drifts toward symmetry over a very long interaction time. Large dispersions of proton and neutron distributions of the produced fragments indicate that diffusion mechanism may help to populate heavy trans-uranium elements near the quasi-fission regime in these collisions.
nucl-thPRC(2015)·27 citations
04
Light-quark baryon spectroscopy from ANL-Osaka dynamical coupled-channels analysis
Hiroyuki Kamano🇯🇵
We review our recent efforts for determining resonance parameters associated with light-quark baryons ( $N^{*}$ , $Δ^{*}$ , $Λ^{*}$ , $Σ^{*}$ ) through comprehensive analyses of various meson production reactions off the nucleon within the ANL-Osaka dynamical coupled-channels approach.
nucl-thhep-phnucl-exJPS Conf.Proc.(2016)·1 citation
05
The heat capacity of the neutron star inner crust within an extended NSE model
S. Burrello🇮🇹 · F. Gulminelli🇫🇷 · F. Aymard🇫🇷 · M.Colonna🇮🇹 · Ad.R.Raduta
Superfluidity in the crust is a key ingredient for the cooling properties of proto-neutron stars. Present theoretical calculations employ the quasi-particle mean-field Hartree-Fock-Bogoliubov theory with temperature dependent occupation numbers for the quasi-particle states. Finite temperature stellar matter is characterized by a whole distribution of different nuclear species. We want to assess the importance of this distribution on the calculation of heat capacity in the inner crust. Following a recent work, the Wigner-Seitz cell is mapped into a model with cluster degrees of freedom. The finite temperature distribution is then given by a statistical collection of Wigner-Seitz cells. We additionally introduce pairing correlations in the local density BCS approximation both in the homogeneous unbound neutron component, and in the interface region between clusters and neutrons. The heat capacity is calculated in the different baryonic density conditions corresponding to the inner crust, and in a temperature range varying from 100 KeV to 2 MeV. We show that accounting for the cluster distribution has a small effect at intermediate densities, but it considerably affects the heat capacity both close to the outer crust and close to the core. We additionally show that it is very important to consider the temperature evolution of the proton fraction for a quantitatively reliable estimation of the heat capacity.
nucl-thPRC(2015)·33 citations
06
Closed analytical solutions of the d-dimensional Schrödinger equation with deformed Woods-Saxon potential plus double ring-shaped potential
M.Chabab · A. El Batoul · M. Oulne
By employing the Pekeris approximation, the D-dimensional Schrödinger equation is solved for the nuclear deformed Woods-Saxon potential plus double ring-shaped potential within the framework of the Asymptotic Iteration Method (AIM). The energy eingenvalues are given in a closed form and the corresponding normalized eigenfunctions are obtained in terms of hypergeometric functions. Our general results reproduce many predictions obtained in the literature, using the Nikiforov-Uvarov method (NU) and the Improved Quantization Rule approach, particulary those derived by considering Woods-Saxon potential without deformation and/or without ring shape interaction.
nucl-thmath-phmath.MPquant-phZ.Naturforsch.A(2016)·6 citations
07
Assessing Theory Uncertainties in EFT Power Countings from Residual Cutoff Dependence
Harald W. Griesshammer (George Washington U.)🇺🇸
I summarise a method to quantitatively assess the consistency of power-counting proposals in Effective Field Theories which are non-perturbative at leading order. It uses the fact that the Renormalisation Group evolution of an observable predicts the functional form of its residual cutoff dependence on the EFT breakdown scale, low-momentum scales, and the order of the calculation. Passing this test is a necessary but not sufficient consistency criterion for a suggested power counting whose exact nature is disputed. For example, in ChiEFT with more than one nucleon, a lack of universally accepted analytic solutions obfuscates the relation between convergence pattern and numerical results, and led to proposals which predict different numbers of Low Energy Coefficients at the same chiral order. The method may provide an independent check whether an observable is renormalised at a given order, and of both the breakdown scale and the momentum-dependent order-by-order convergence pattern of an EFT. Conversely, it may help identify LECs which produce renormalised observables at a given order. I also discuss its underlying assumptions and relation to the RG Equation; useful choices for observables and cutoffs; the momentum window in which the test provides best signals; its dependence on the values and forms of cutoffs as well as on the EFT parameters; the impact of fitting Low Energy Coefficients to data in different or the same channel; caveats and limitations. Since the test is designed to minimise the use of data, it allows one to quantitatively falsify if the EFT has been renormalised consistently, rather than quantifying how an EFT compares to experiment. Its application in particular to the 3P0 and 3P2-3F2 partial waves of NN scattering in ChiEFT may elucidate persistent power-counting issues. Details and a better bibliography can be found in an upcoming publication.
nucl-thhep-phPoS(2016)·20 citations
08
Pion and kaon in the Beth-Uhlenbeck approach
A. Dubinin🇵🇱 · D. Blaschke🇵🇱 · A. Radzhabov🇷🇺
In the present work the Mott effect for pions and kaons is described within a Beth- Uhlenbeck approach on the basis of the PNJL model. The contribution of these degrees of freedom to the thermodynamics is encoded in the temperature dependence of their phase shifts. A comparison with results from $N_{f} = 2 + 1$ lattice QCD thermodynamics is performed.
↳ hep-phnucl-thJ.Phys.Conf.Ser.(2016)·3 citations
09
Solution of the proton radius puzzle? Low momentum transfer electron scattering data are not enough
Michael O. Distler🇩🇪 · Thomas Walcher🇩🇪 · Jan C. Bernauer🇺🇸
In two recent papers it is argued that the 'proton radius puzzle' can be explained by truncating the electron scattering data to low momentum transfer and fit the rms radius in the low momentum expansion of the form factor. It is shown that this procedure is inconsistent and violates the Fourier theorem. The puzzle cannot be explained in this way.
↳ nucl-exnucl-th13 citations
10
Gauge-Invariant Gluon TMD and Evolution in the Coordinate Space
I.O. Cherednikov🇧🇪
Maximally path-dependent gauge-invariant operator definition of the gluon transverse-momentum dependent pdf (gTMD) is discussed. It is argued that the evolution equations for the gTMD in the coordinate representation can be derived from the equations of motion in the generalised loop space, whose elements are the hadronic averages of the Wilson loops of entirely arbitrary shape.
↳ hep-phhep-latnucl-thPoS(2015)·2 citations
11
Chiral phase transition of $N_{f}$ =2+1 and 3 QCD at vanishing baryon chemical potential
Heng-Tong Ding🇨🇳 · Prasad Hegde (for the Bielefeld-BNL-CCNU collaboration)🇨🇳
We present updated results on chiral phase structure in (2+1)-flavor ( $N_{f}$ =2+1) and 3-flavor ( $N_{f} = 3$ ) QCD based on the simulations using Highly Improved Staggered Quarks on lattices with temporal extent $N_{τ}$ =6 at vanishing baryon chemical potential. In $N_{f}$ =2+1 QCD we have performed simulations with a strange quark fixed to its physical value and two degenerate light quarks whose values are adjusted to have 5 values of Goldstone pion masses in the region of 160 - 80 MeV in the continuum limit. The universal scaling behavior of chiral condensates as well as chiral susceptibilities is discussed and the tri-critical point is suggested to be located below the physical point, i.e. at smaller than physical strange quark mass. In $N_{f}$ =3 QCD simulations with 6 different masses of 3 degenerate quarks corresponding to the Goldstone pion masses in the region of 230 - 80 MeV have also been performed. Our results suggest that the QCD transition with these values of quark masses is of crossover type and an upper bound of the critical pion mass where the first order phase transition starts is estimated to be about 50 MeV.
↳ hep-latnucl-thPoS(2016)·6 citations
12
Analysis of mechanisms that could contribute to the neutrinoless double-beta decay
Mihai Horoi🇺🇸 · Andrei Neacsu🇺🇸
Neutrinoless double-beta decay, if observed, would signal physics beyond the Standard Model that could be discovered at energies significantly lower than those at which the relevant degrees of freedom could be excited. Therefore, it could be challenging to further use the neutrinoless double-beta decay observations to distinguish between many beyond Standard Model mechanisms contributing to this process. Accurate nuclear structure calculations of the nuclear matrix elements necessary to analyze the decay rates could be helpful to narrow down the list of contributing mechanisms, and to better identify the more exotic properties of the neutrinos. We investigate the information one can get from the angular and energy distribution of the emitted electron assuming that the right-handed currents exist. For the analysis of these distributions we calculate the necessary nuclear matrix elements using shell model techniques.
↳ hep-phnucl-thPRD(2016)·38 citations

Affiliations

first authorsco-authorsvia INSPIRE