Nuclear Theory·nucl-th

Monday·January 16, 2017

10 papers—6 primary·4 cross-listed

01
[Submitted on 12 Jan 2017]
Pseudomagnetic effects for resonance neutrons in the search for time reversal invariance violation
Vladimir Gudkov🇺🇸 · Hirohiko M. Shimizu🇯🇵
A general theory of pseudomagnetic effects for the propagation of polarized neutrons through polarized target in multi resonance approach is presented. Some applications related to the proposed search for time reversal invariance violation in neutron scattering are considered.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1701.03521 [pdf]
PRC(2017)·8 citations
02
[Submitted on 13 Jan 2017]
Tensor-optimized antisymmetrized molecular dynamics as a successive variational method in nuclear many-body system
Takayuki Myo · Hiroshi Toki · Kiyomi Ikeda · Hisashi Horiuchi · Tadahiro Suhara
We study the tensor-optimized antisymmetrized molecular dynamics (TOAMD) as a successive variational method in many-body systems with strong interaction for nuclei. In TOAMD, the correlation functions for the tensor force and the short-range repulsion and their multiples are operated to the AMD state as the variational wave function. The total wave function is expressed as the sum of all the components and the variational space can be increased successively with the multiple correlation functions to achieve convergence. All the necessary matrix elements of many-body operators, consisting of the multiple correlation functions and the Hamiltonian, are expressed analytically using the Gaussian integral formula. In this paper we show the results of TOAMD with up to the double products of the correlation functions for the s-shell nuclei, 3H and 4He, using the nucleon-nucleon interaction AV8'. It is found that the energies and Hamiltonian components of two nuclei converge rapidly with respect to the multiple of correlation functions. This result indicates the efficiency of TOAMD for the power series expansion in terms of the tensor and short-range correlation functions.
Comments:
7 pages, 5 figures, added references, corrected typos
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1701.03547 [pdf]
PLB(2017)·33 citations
03
[Submitted on 13 Jan 2017]
Nuclear Symmetry Energy Extracted from Laboratory Experiments
Bao-An Li🇺🇸
Some recent progress and open questions in extracting and understanding the new physics underlying the density dependence of nuclear symmetry energy from laboratory experiments are discussed.
Comments:
A feature article to appear in Nuclear Physics News
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1701.03564 [pdf]
Nucl.Phys.News(2017)·76 citations
04
[Submitted on 13 Jan 2017]
Polarization-transfer observables with polarized beams
Anatoli Plavko
A review is given of our present knowledge of different parametrization of experimental results in inelastic scattering process with polarized proton beams. Spin observables in inelastic proton scattering for a set of lightweight nuclei are studied at intermediate energies in the region of 100-500 MeV. Two important types of DWIA calculations are used in the analysis of experiments. Important spin observables representing the difference functions (P-Ay) and (P-Ay)sigma are examined along with the polarization-transfer (spin-transfer) coefficients D(ij), i.e. D with indices NN, SS, LL, LS and SL, in inelastic scattering of polarized protons. The above indicated value of sigma is the differential cross section. These spin observables are treated in the context of the exchange features of the effective interaction. The linear combinations D(K), D(i) of the complete polarization-transfer observables D(ij) in inelastic proton scattering at intermediate energies are extensively demonstrated. A comparison between systematized, measured and calculated quantities of the combinations D(K) and, partially, sigma D(K) for the 1+ (T=0 and T=1) levels in 12-C, for the 4- (T=0 and T=1) states in 16-O, and for the 6- (T=0 and T=1) levels in 28-Si are reported. Particularities in angular distributions of transverse- and longitudinal-spin-transfer probabilities D(K) for T=0 and T=1 unnatural-parity states in some nuclei are discussed. The spin-observable combinations D(Ls) allowed to differentiate reliably the strength of isoscalar and isovector spin-orbit. interactions. The comparison of the experimental and calculated D(K) for the 1+, T = 0 state in 12- C with the use of zero-range treatment (LEA code) and exact finite-range calculations (DWBA-91 program) made it possible to identify the role of exchange contributions. Other observables are also considered for the same purposes.
Comments:
The review is based on the contributions from A.V. Plavko, M.S. Onegin and V.I. Kudriashov at: 62nd Int. Conf. Nucleus 2012, Voronezh, 2012; 63rd Int. Conf. Nucleus 2013, Moscow, 2013; 64th Int. Conf. Nucleus 2014, Minsk, 2014, and 65th Int. Conf. Nucleus 2015, St. Petersburg, 2015 (see also a report by A.V. Plavko, M.S. Onegin, and V.I. Kudriashov of Jul 03 2015 nucl-th arxiv: 1507, 00468V1)
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1701.03582 [pdf]
0 citations
05
[Submitted on 13 Jan 2017]
In medium dispersion relation effects in nuclear inclusive reactions at intermediate and low energies
Juan Nieves🇪🇸 · Joanna Ewa Sobczyk🇵🇱
In a well-established many-body framework, successful in modeling a great variety of nuclear processes, we analyze the role of the spectral functions (SFs) accounting for the modifications of the dispersion relation of nucleons embedded in a nuclear medium. We concentrate in processes mostly governed by one-body mechanisms, and study possible approximations to evaluate the particle-hole propagator using SFs. We also investigate how to include together SFs and long-range RPA-correlation corrections in the evaluation of nuclear response functions, discussing the existing interplay between both type of nuclear effects. At low energy transfers (\le 50 MeV), we compare our predictions for inclusive muon and radiative pion captures in nuclei, and charge-current (CC) neutrino-nucleus cross sections with experimental results. We also present an analysis of intermediate energy quasi-elastic neutrino scattering for various targets and both neutrino and antineutrino CC driven processes. In all cases, we pay special attention to estimate the uncertainties affecting the theoretical predictions. In particular, we show that errors on the \sigma_{\mu}/\sigma_e ratio are much smaller than 5%, and also much smaller than the size of the SF+RPA nuclear corrections, which produce significant effects, not only in the individual cross sections, but also in their ratio for neutrino energies below 400 MeV. These latter nuclear corrections, beyond Pauli blocking, turn out to be thus essential to achieve a correct theoretical understanding of this ratio of cross sections of interest for appearance neutrino oscillation experiments. We also briefly compare our SF and RPA results to predictions obtained within other representative approaches.
Comments:
40 pages, 65 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1701.03628 [pdf]
Annals Phys.(2017)·60 citations
06
[Submitted on 13 Jan 2017]
Triaxial shape fluctuations and quasiparticle excitations in heavy nuclei
Fang-Qi Chen · J. Luis Egido
The deformation parameters beta and gamma together with the two-quasiparticle excitations are taken into account, for the first time, as coordinates within a symmetry conserving (angular momentum and particle number) generator coordinate method. The simultaneous consideration of collective as well as single particle degrees of freedom allows us to describe soft and rigid nuclei as well as the transition region in between. We apply the new theory to the study of the spectra and transition probabilities of the 156-172Er isotopes with a Pairing plus Quadrupole residual interaction. Good agreement with the experimental results is obtained for most of the observables studied and with the same quality for the very soft and the strongly deformed nuclei.
Comments:
14 pages, 11 figures, accepted for publication in Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1701.03650 [pdf]
PRC(2017)·29 citations
07
[Submitted on 12 Jan 2017] (cross-list from astro-ph.HE)
Millisecond radio pulsars with known masses: parameter values and equation of state models
Sudip Bhattacharyya (TIFR, India) · Ignazio Bombaci (Universita di Pisa / INFN, Italy) · Debades Bandyopadhyay (SINP, India) · Arun V. Thampan (St. Joseph's College / IUCAA, India) · Domenico Logoteta (INFN, Italy)
The recent fast growth of a population of millisecond pulsars with precisely measured mass provides an excellent opportunity to characterize these compact stars at an unprecedented level. This is because the stellar parameter values can be accurately computed for known mass and spin rate and an assumed equation of state (EoS) model. For each of the 16 such pulsars and for a set of EoS models from nucleonic, hyperonic, strange quark matter and hybrid classes, we numerically compute fast spinning stable stellar parameter values considering the full effect of general relativity. This first detailed catalogue of the computed parameter values of observed millisecond pulsars provides a testbed to probe the physics of compact stars, including their formation, evolution and EoS. We estimate uncertainties on these computed values from the uncertainty of the measured mass, which could be useful to quantitatively constrain EoS models. We note that the largest value of the central density $ρ_{c}$ in our catalogue is $\sim 5.8$ times the nuclear saturation density $ρ_{sat}$ , which is much less than the expected maximum value $13 ρ_{sat}$ . We argue that the $ρ_{c}$ -values of at most a small fraction of compact stars could be much larger than $5.8 ρ_{sat}$ . Besides, we find that the constraints on EoS models from accurate radius measurements could be significantly biased for some of our pulsars, if stellar $s p innin g$ configurations are not used to compute the theoretical radius values.
Comments:
16 pages, 2 figures, 4 tables, accepted for publication in New Astronomy
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
1701.03489 [pdf]
New Astron.(2017)·22 citations
08
[Submitted on 13 Jan 2017] (cross-list from hep-lat)
Chiral phase structure of three flavor QCD at vanishing baryon number density
A. Bazavov🇺🇸 · H.-T. Ding🇨🇳 · P. Hegde🇮🇳 · F. Karsch🇺🇸 · E. Laermann🇩🇪 · Swagato Mukherjee🇺🇸 · P. Petreczky🇺🇸 · C. Schmidt🇩🇪
We investigate the phase structure of QCD with 3 degenerate quark flavors as function of the degenerate quark masses at vanishing baryon number density. We use the Highly Improved Staggered Quarks on lattices with temporal extent $N_{t} = 6$ and perform calculations for six values of quark masses, which in the continuum limit correspond to pion masses in the range $80 MeV ≲ m_{π} ≲ 230$ MeV. By analyzing the volume and temperature dependence of the chiral condensate and chiral susceptibility we find no direct evidence for a first order phase transition in this range of pion mass values. Relying on the universal scaling behaviors of the chiral observables near an anticipated chiral critical point, we estimate an upper bound for the critical pion mass, $m_{π}^{c} ≲$ 50 MeV, below which a region of first order chiral phase transition is favored.
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1701.03548 [pdf]
PRD(2017)·91 citations
09
[Submitted on 13 Jan 2017] (cross-list from hep-ph)
Mesonic and nucleon fluctuation effects at finite baryon density
G. Fejos🇯🇵 · A. Hosaka🇯🇵
Mesonic and nucleon fluctuation effects are investigated in medium. We couple the nucleon field to the $2 + 1$ flavor meson model and investigate the finite temperature and density behavior of the system, in particular, the axial anomaly function. Somewhat contrary to earlier expectations we find that it tends to strengthen at finite density. At lower temperatures nucleon density fluctuations can cause a relative difference in the $U_{A} (1)$ axial anomaly of about $20%$ . This has important consequences on the mesonic spectra, especially on the $η - η^{'}$ system, as we observe no drop in the $η^{'}$ mass as a function of the baryochemical potential, irrespective of the temperature. Based on the details of chiral symmetry restoration, it is argued that there has to be a competition between underlying QCD effects of the anomaly and fluctuations of the low energy hadronic degrees of freedom, and the fate of the $U_{A} (1)$ coefficient should be decided by taking into account both effects simultaneously.
Comments:
9 pages, 4 figures, matches published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1701.03717 [pdf]
PRD(2017)·15 citations
10
[Submitted on 13 Jan 2017] (cross-list from hep-ph)
Nucleon resonances $N (1875)$ and $N (2100)$ as strange partners of LHCb pentaquarks
Jun He🇨🇳
In this work, we investigate the possibility of interpreting two nucleon resonances, the $N (1875)$ and the $N (2100)$ , as hadronic molecular states from the $Σ^{*} K$ and $Σ K^{*}$ interactions, respectively. With the help of effective Lagrangians in which coupling constants are determined by the SU(3) symmetry, the $Σ^{*} K$ and $Σ K^{*}$ interactions are described by the vector-meson and pseudoscalar-meson exchanges. With the one-boson-exchange potential obtained, bound states from the $Σ^{*} K$ and $Σ K^{*}$ interactions are searched for in a quasipotential Bethe-Saltpeter equation approach. A bound state with quantum number $I (J^{P}) = 1/2 (3/ 2^{-})$ is produced from the $Σ^{*} K$ interaction, which can be identified as the $N (1875)$ listed in PDG. It can be seen as a strange partner of the LHCb pentaquark $P_{c} (4380)$ with the same quantum numbers in the molecular state picture. The $Σ K^{*}$ interaction also produces a bound state with quantum number $I (J^{P}) = 1/2 (3/ 2^{-})$ , which is related to experimentally observed $N (2100)$ in the $ϕ$ photoproduction. Our results suggest that the $N (2120)$ observed in the $K Λ (1520)$ photoproduction and the $N (2100)$ observed in the $ϕ$ photoproduction have different origins. The former is a conventional three-quark state while the latter is a $Σ K^{*}$ molecular state, which can be seen as a strange partner of the $P_{c} (4450)$ with different spin parity.
Comments:
8 pages, 1 figures. Published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1701.03738 [pdf]
PRD(2017)·69 citations

Affiliations

first authorsco-authorsvia INSPIRE