Nuclear Theory·nucl-th

Friday·December 25, 2015

8 papers—7 primary·1 cross-listed

01
[Submitted on 23 Dec 2015]
Observable consequences of event-by-event fluctuations of HBT radii
Christopher Plumberg🇺🇸 · Ulrich Heinz🇺🇸
We explore the effects of event-by-event fluctuations of Hanbury Brown-Twiss (HBT) radii and show how they can be observed experimentally. The relation of measured HBT radii extracted from ensemble-averaged correlation functions to the mean of their event-by-event probability distribution is clarified. We propose a method to experimentally determine the mean and variance of this distribution and test it on an ensemble of fluctuating events generated with the viscous hydrodynamic code VISH2+1. Using the same code, the sensitivity of the mean and variance of the HBT radii to the specific QGP shear viscosity $η / s$ is studied. We report sensitivity of the mean pion HBT radii and their variances to the temperature dependence of $η / s$ near the quark-hadron transition at a level similar (10-20%) to that which was previously observed for elliptic and quadrangular flow of charged hadrons [1].
Comments:
Proceedings for Quark Matter 2015 in Kobe, Japan
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1512.07631 [pdf]
NPA(2016)·5 citations
02
[Submitted on 24 Dec 2015]
Hypernuclei in Halo/Cluster Effective Field Theory
Shung-Ichi Ando (Sunmoon U.)🇰🇷
The light double $Λ$ hypernuclei, $_{ΛΛ}^{4}$ H and $_{ΛΛ}^{6}$ He, are studied as three-body $ΛΛ d$ and $ΛΛ α$ cluster systems in halo/cluster effective field theory at leading order. We find that the $ΛΛ d$ system in spin-0 channel does not exhibit a limit cycle whereas the $ΛΛ d$ system in spin-1 channel and the $ΛΛ α$ system in spin-0 channel do. The limit cycle is associated with the formation of bound states, known as Efimov states, in the unitary limit. For the $ΛΛ d$ system in the spin-0 channel we estimate the scattering length $a_{0}$ for $S$ -wave $Λ$ hyperon-hypertriton scattering as $a_{0} = 16.0 \pm 3.0$ fm. We also discuss that studying the cutoff dependences in the $ΛΛ d$ and $ΛΛ α$ systems, the bound state of $_{ΛΛ}^{4}$ H is not an Efimov state but formed due to a high energy mechanism whereas that of $_{ΛΛ}^{6}$ He may be regarded as an Efimov state.
Comments:
review article for special issue on "Effective Field Theory in Nuclear Physics" in Int. J. Mod. Phys. E; 16 pages and 8 eps figures, version accepted for publication
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1512.07674 [pdf]
IJMPE(2016)·8 citations
03
[Submitted on 24 Dec 2015]
Two decay paths for calculation of nuclear matrix element of neutrinoless double-beta decay using quasiparticle random-phase approximation
Jun Terasaki🇯🇵
It is possible to employ virtual decay paths, including two-particle transfer, to calculate the nuclear matrix element of neutrinoless double-beta decay under the closure approximation, in addition to the true double-beta path. In the quasiparticle random-phase approximation (QRPA) approach, it is necessary to introduce the product wave functions of the like-particle and proton-neutron QRPA ground states, for achieving consistency between the calculations of the true and virtual paths. Using these different paths, the problem of whether or not these two methods give equivalent nuclear matrix elements (NME) is investigated. It is found that the two results are inequivalent, resulting from the different many-body correlations included in the two QRPA methods, i.e., the use of the product wave functions alone is not sufficient. The author proposes introduction of the proton-neutron pairing interaction with an adequate strength in the double-beta-path method, which carries less many-body correlations without this supplemental interaction, for obtaining the NME equivalent to that of the two-particle-transfer-path method. The validity of the proposed modified approach is examined.
Comments:
16 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1512.07708 [pdf]
PRC(2016)·14 citations
04
[Submitted on 24 Dec 2015]
Investigation of 10Be and its cluster dynamics from nonlocalized clustering concept
Mengjiao Lyu🇨🇳 · Zhongzhou Ren🇨🇳 · Bo Zhou🇯🇵 · Yasuro Funaki🇯🇵 · Hisashi Horiuchi🇯🇵 · Gerd Röpke🇩🇪 · Peter Schuck🇫🇷 · Akihiro Tohsaki🇯🇵 · Chang Xu🇨🇳 · Taiichi Yamada🇯🇵
We extend the new concept of nonlocalized clustering to the nucleus 10Be with proton number Z=4 and neutron number N=6 (N=Z+2). The Tohsaki-Horiuchi-Schuck-Röpke (THSR) wave function is formulated for the description of different structures of 10Be. Physical properties such as energy spectrum and root-mean-square radii are calculated for the first two 0+ states and corresponding rotational bands. With only one single THSR wave function, the calculated results show good agreement with other models and experimental values. We apply, for the first time, the THSR wave function on the chain orbit ({\sigma}-orbit) structure in the 0^+_2 state of 10Be. The ring orbit ({\pi}-orbit) and {\sigma}-orbit structures are further illustrated by calculating the density distribution of the valence neutrons. We also investigate the dynamics of ff-clusters and the correlations of two valence neutrons in 10Be.
Comments:
18 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1512.07727 [pdf]
PRC(2016)·48 citations
05
[Submitted on 24 Dec 2015]
Unified description of rotational-, $γ$ -, and quasiparticle-band structures in neutron-rich mass $\sim$ 110 region
G. H. Bhat · J. A. Sheikh · Y. Sun · R. Palit
Band structures of the neutron-rich Mo- and Ru-isotopes around A $\sim$ 110 are investigated using the triaxial projected shell model (TPSM) approach employing multi-quasiparticle configuration space. The mass region under investigation depicts a rich variety of band structures with well developed $γ$ - and $γ γ$ -bands, and quasiparticle excitations based on them. It is demonstrated that TPSM provides a reasonable description of most of the observed properties, in particular, detailed structure variations observed in Mo-isotopes are well reproduced in the present work.
Comments:
19 pages, 7 figures, to appear in Nucl. Phys. A
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1512.07816 [pdf]
NPA(2016)·19 citations
06
[Submitted on 24 Dec 2015]
Use of the Meta-analysis and Kolmogorov Criteria in the Finding of Singularities of a Nuclear Matter Created in Ultra Relativistic Nuclear Collisions
V.A. Kizka🇺🇦
Published theoretical data from several models: PHSD and HSD both with and without chiral symmetry restoration (CSR), applied to experimental data on nuclear collisions from BEVALAC and SIS to LHC energies were analyzed using meta-analysis and Kolmogorov criteria. This made it possible to localize possible features of nuclear matter created in central nucleus-nucleus collisions. Ignition of a drop of quark-gluon plasma (QGP) begins already at an energy of about $s_{N N}$ = 2 GeV. We estimate that this QGP droplet occupies a small fraction, 15 $%$ (average radius of about 5.3 fermi if the fireball radius is 10 fermi) of the total volume of the fireball created at $s_{N N}$ = 2.7 GeV. A drop of exotic matter undergoes a split phase transition: separated boundaries of sharp (1st order) crossover and CSR in chiral limit, between QGP and Quarkyonic matter at an energy about $s_{N N}$ = 3.5 GeV. The critical endpoint of 2nd order probably cannot be reached in nuclear collisions. The triple phase area occupies interval from $s_{N N}$ = 12 GeV to 15 GeV, the critical endpoint of 1st order at around $s_{N N}$ = 20 GeV. The boundary of smooth (2nd order) crossover transition with CSR in chiral limit between Quarkyonic matter and QGP was localized between $s_{N N}$ = 9.3 GeV and 12 GeV, and between Hadronic and QGP in the interval from $s_{N N}$ = 15 GeV to 20 GeV, the boundary of sharp (1st order) crossover transition with CSR in chiral limit between Hadronic matter and QGP was localized after $s_{N N}$ = 20 GeV. The phase trajectory of the hadronic corona, enveloping the exotic droplet, always remains in the hadronic phase.
Comments:
13 pages, 6 figures, improved explanation and argumentation, published in the journal
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1512.07829 [pdf]
Science(2024)·1 citation
07
[Submitted on 24 Dec 2015]
Final-state interactions in two-nucleon knockout reactions
Camille Colle · Wim Cosyn · Jan Ryckebusch
Background: Exclusive two-nucleon knockout after electroexcitation of nuclei ( $A (e, e^{'} N N)$ in brief) is considered to be a primary source of information about short-range correlations (SRC) in nuclei. For a proper interpretation of the data, final-state interactions (FSI) need to be theoretically controlled. Purpose: Our goal is to quantify the role of FSI effects in exclusive $A (e, e^{'} pN)$ reactions for four target nuclei representative for the whole mass region. Our focus is on processes that are SRC driven. We investigate the role of FSI for two characteristic detector setups corresponding with a "small" and "large" coverage of the available phase space. Results: The transparency $T_{A}^{pN}$ , defined as the ratio of exclusive $(e, e^{'} pN)$ cross sections on nuclei to those on "free" nucleon pairs, drops from $0.2 - 0.3$ for $^{12}$ C to $0.04 - 0.07$ for $^{208}$ Pb. For all considered kinematics, the mass dependence of the $T_{A}^{pN}$ can be captured by the power law $T_{A}^{pN} \propto A^{- λ}$ with $0.4 ≲ λ ≲ 0.5$ . Apart from an overall reduction factor, we find that FSI only modestly affects the distinct features of SRC-driven $A (e, e^{'} pN)$ which are dictated by the c.m. distribution of close-proximity pairs. Conclusion: The SCX mechanisms represent a relatively small (order of a few percent) contribution of SRC-driven $A (e, e^{'} pN)$ processes. The mass dependence of FSI effects in exclusive $A (e, e^{'} pN)$ can be captured in a robust power law and is in agreement with the predictions obtained in a toy model.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1512.07841 [pdf]
PRC(2016)·27 citations
08
[Submitted on 24 Dec 2015] (cross-list from astro-ph.SR)
The Equation of State of Hot, Dense Matter and Neutron Stars
James M. Lattimer🇺🇸 · M. Prakash🇺🇸
Recent developments in the theory of pure neutron matter and experiments concerning the symmetry energy of nuclear matter, coupled with recent measurements of high-mass neutron stars, now allow for relatively tight constraints on the equation of state of dense matter. We review how these constraints are formulated and describe the implications they have for neutron stars and core-collapse supernovae. We also examine thermal properties of dense matter, which are important for supernovae and neutron star mergers, but which cannot be nearly as well constrained at this time by experiment. In addition, we consider the role of the equation of state in medium-energy heavy-ion collisions.
Comments:
87 pages, 20 figures, Accepted for Phys. Rep (Gerald E. Brown's Memorial Volume)
Subjects:
Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
1512.07820 [pdf]
Phys.Rept.(2016)·622 citations

Affiliations

first authorsco-authorsvia INSPIRE