Nuclear Theory·nucl-th

Friday·March 6, 2020

13 papers—7 primary·6 cross-listed

01
[Submitted on 4 Mar 2020]
Generalized Contact Formalism Analysis of the $^{4}$ He $(e, e^{'} pN)$ Reaction
J.R. Pybus · I. Korover · R. Weiss · A. Schmidt · N. Barnea · D.W. Higinbotham · E. Piasetzky · M. Strikman · L.B. Weinstein · O. Hen
Measurements of short-range correlations in exclusive $^{4}$ He $(e, e^{'} pN)$ reactions are analyzed using the Generalized Contact Formalism (GCF). We consider both instant-form and light-cone formulations with both the AV18 and local N2LO(1.0) nucleon-nucleon ( $N N$ ) potentials. We find that kinematic distributions, such as the reconstructed pair opening angle, recoil neutron momentum distribution, and pair center of mass motion, as well as the measured missing energy, missing mass distributions, are all well reproduced by GCF calculations. The missing momentum dependence of the measured $^{4}$ He $(e, e^{'} pN)$ / $^{4}$ He $(e, e^{'} p)$ cross-section ratios, sensitive to nature of the $N N$ interaction at short-distacnes, are also well reproduced by GCF calculations using either interaction and formulation. This gives credence to the GCF scale-separated factorized description of the short-distance many-body nuclear wave-function.
Comments:
Accepted for publication in Physics Letters B. 8 pages, 4 figures and online supplementary materials
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2003.02318 [pdf]
PLB(2020)·35 citations
02
[Submitted on 4 Mar 2020]
Excluded-volume model for quarkyonic Matter: Three-flavor baryon-quark Mixture
Dyana C. Duarte🇺🇸 · Saul Hernandez-Ortiz🇺🇸 · Kie Sang Jeong🇺🇸
The single-flavor excluded-volume model based on the effective size of baryons reproduces the hard-soft density evolution of the equation of state (EoS) required by the recent studies of GW170817. This phenomenological model basically realizes the concept of quarkyonic matter which is introduced from large- $N_{c}$ gauge theory for dense matter. Enhanced nucleon interactions and dynamically generated quark degrees of freedom can reproduce the hard-soft evolution of the EoS. In this paper, we extend the excluded-volume model to a three-flavor system by considering electromagnetic charge and possible weak equilibrium in order to obtain a proper description for the hard-soft behavior of the EoS inferred from the gravitational waves observations.
Comments:
11 pages, 6 figures, tex command fixed
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2003.02362 [pdf]
PRC(2020)·56 citations
03
[Submitted on 5 Mar 2020]
Neutron-neutron scattering length from $π^{+}$ photoproduction on the deuteron
Satoshi X. Nakamura (Univ. Science and Technology of China)🇨🇳 · Takatsugu Ishikawa (ELPH, Tohoku Univ.)🇯🇵 · Toru Sato (RCNP, Osaka Univ.)🇯🇵
We discuss the possibility of extracting the neutron-neutron scattering length $a_{nn}$ and effective range $r_{nn}$ from cross section data ( $d^{2} σ / d M_{nn} / d Ω_{π}$ ), as a function of the $nn$ invariant mass $M_{nn}$ , for $π^{+}$ photoproduction on the deuteron ( $γ d \to π^{+} nn$ ). The analysis is based on a $γ d \to π^{+} nn$ reaction model in which realistic elementary amplitudes for $γ p \to π^{+} n$ , $N N \to N N$ , and $π N \to π N$ are built in. We show that $M_{nn}$ dependence (lineshape) of a ratio $R_{th}$ , $d^{2} σ / d M_{nn} / d Ω_{π}$ normalized by $d σ / d Ω_{π}$ for $γ p \to π^{+} n$ and the nucleon momentum distribution inside the deuteron, at the kinematics with $θ_{π} = 0^{\circ}$ and $E_{γ} \sim 250$ MeV is particularly useful for extracting $a_{nn}$ and $r_{nn}$ from the corresponding data $R_{exp}$ . It is found that $R_{exp}$ with 2% error, resolved into the $M_{nn}$ bin width of 0.04 MeV (corresponding to the $p_{π}$ bin width of 0.05 MeV $/ c$ ), can determine $a_{nn}$ and $r_{nn}$ with uncertainties of $\pm 0.21$ fm and $\pm 0.06$ fm, respectively, for the case of $a_{nn} = - 18.9$ fm and $r_{nn} = 2.75$ fm. The requirement of such narrow bin widths indicates that the momenta of the incident photon and the emitted $π^{+}$ have to be measured with high resolutions. This can be achieved by utilizing virtual photons of very small $Q^{2}$ from electron scattering at Mainz MAMI facility. The proposed method for determining $a_{nn}$ and $r_{nn}$ from $γ d \to π^{+} nn$ has a great experimental advantage over the previous one utilizing $π^{-} d \to γ nn$ for being free from the formidable task of controlling the neutron detection efficiency and its uncertainty.
Comments:
22 pages, 15 figures, several refinements (not major change)
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2003.02497 [pdf]
5 citations
04
[Submitted on 5 Mar 2020]
Collision dynamics at medium and relativistic energies
Maria Colonna🇮🇹
Recent results connected to nuclear collision dynamics, from low up to relativistic energies, are reviewed. Heavy ion reactions offer the unique opportunity to probe the complex nuclear many-body dynamics and to explore, in laboratory experiments, transient states of nuclear matter under several conditions of density, temperature and charge asymmetry. From the theoretical point of view, transport models are an essential tool to undertake these investigations and make a connection between the nuclear effective interaction and sensitive observables of experimental interest. In this article, we mainly focus on the description of results of transport models for a selection of reaction mechanisms, also considering comparisons of predictions of different approaches. This analysis can help understanding the impact of the interplay between mean-field and correlation effects, as well as of in-medium effects, on reaction observables, which is an essential point also for extracting information on the nuclear Equation of State. A special emphasis will be given to the review of recent studies aimed at constraining the density behavior of the nuclear symmetry energy. For reactions at medium (Fermi) energies, we will describe light particle and fragment emission mechanisms, together with isospin transport effects. Collective effects characterizing nuclear collision dynamics, such as transverse and elliptic flows, will be discussed for relativistic heavy ion reactions, together with meson production and isotopic ratios.
Comments:
accepted for publication on Progress in Particle and Nuclear Physics
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2003.02500 [pdf]
PPNP·53 citations
05
[Submitted on 5 Mar 2020]
On microscopic theory of pygmy- and giant resonances
S. Kamerdzhiev · M. Shitov
The Green function formalism with a consistent account for phonon coupling (PC), based on the self-consistent theory of finite Fermi-systems, is applied for pygmy- and giant multipole resonances in magic nuclei with the aim to consider particle-hole (ph) and complex 1p1h phonon configurations. A new equation for the effective field, which describes nuclear polarizability, is obtained. It contains new PC contributions which are of interest in the energy region under consideration. They are due to: i)the tadpole effect in the standard ph-propagator, ii)two new induced interactions (caused by the exchange of ph-phonon) in the second ph-channel and in the particle-particle channels, and iii) the first and second variations of the effective interaction in the phonon field. The general expressions for energies and probabilities of transitions between the ground and excited states are obtained. The qualitative analysis and discussion of the new terms are performed.
Comments:
10 pages, 7 figures, submitted
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2003.02553 [pdf]
EPJA(2020)·5 citations
06
[Submitted on 4 Mar 2020]
Comment on "Enhanced deuterium-tritium fusion cross sections in the presence of strong electromagnetic fields"
Friedemann Queisser · Ralf Schützhold
In their article [Phys.\ Rev.\ C {\bf 100}, 064610 (2019)], Lv, Duan, and Liu study the enhancement of deuterium-tritium fusion reactions by the electromagnetic field of an x-ray free-electron laser (XFEL). While we support the general idea (which was put forward earlier in our rapid communication [Phys.\ Rev.\ C {\bf 100}, 041601(R) (2019)]), we find that the time-averaged potential approximation used by Lv, Duan, and Liu is not justified in this regime and does not take into account important effects. Due to those effects, the enhancement mechanism may actually be more efficient than predicted by Lv, Duan, and Liu.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2003.02661 [pdf]
3 citations
07
[Submitted on 5 Mar 2020]
Understanding fission fragment mass distributions in a modified shape of random neck rupture model
Yogesh Sawant · S. V. Suryanarayana · B. K. Nayak · A. Saxena · R. K. Choudhury
The variances of the fission fragment mass distributions for symmetric fission over a wide range of the fissility of the compound nucleus have been investigated within the frame work of Random Neck Rupture Model (RNRM) proposed by Brosa et. al.,. The shape of the fissioning nucleus is generated using crel=1 in the RNRM model, which results in a smooth and continuous shape of fissioning nucleus. This modified shape of RNRM model has been used to analyse experimental data of mass variances for symmetric mass distributions of 27 systems leading to understanding of scission shape dynamics in a wide region of fissility 0.7-0.95. The neck radius is an important parameter of the RNRM model and this has been varied to fit the experimental mass variances data. The systematics of resulting neck radii are studied of as a function fissility and nuclear potential through {\gamma}o, the surface energy coefficient. Further average total kinetic energies of fission fragments <TKE> are studied of as a function of fissility and {\gamma}o parameter. It is observed that the neck radii that fit the experimentally observed variances of the mass distributions fall into two groups and these groups are related to two groups of experimentally observed <TKE>s. Empirical formulae have been obtained for the neck radii for these two groups of fissioning systems. Use of the empirical formulae for neck radii predict the mass variances reasonably well for these systems and it is shown that these empirical neck radii are better estimates than starting with the Rayleigh criterion.16pages,7 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2003.02809 [pdf]
Pramana(2022)·0 citations
08
[Submitted on 4 Mar 2020] (cross-list from hep-ph)
How long does the hydrogen atom live?
David McKeen🇨🇦 · Maxim Pospelov🇺🇸
It is possible that the proton is stable while atomic hydrogen is not. This is the case in models with new particles carrying baryon number which are light enough to be stable themselves but heavy enough so that proton decay is kinematically blocked. Models of new physics that explain the neutron lifetime anomaly generically have this feature, allowing for atomic hydrogen to decay through electron capture on a proton. We calculate the radiative hydrogen decay rate involving the emission of a few hundred keV photon, which makes this process detectable in experiment. In particular, we show that the low energy part of the Borexino spectrum is sensitive to radiative hydrogen decay, and turn this into a limit on the hydrogen lifetime of order $1 0^{30} s$ or stronger. For models where the neutron mixes with a dark baryon, $χ$ , this limits the mixing angle to roughly $1 0^{- 11}$ , restricting the $n \to χ γ$ branching to $1 0^{- 4}$ , over a wide range of parameter space.
Comments:
6 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2003.02270 [pdf]
Universe(2023)·31 citations
09
[Submitted on 4 Mar 2020] (cross-list from hep-ph)
Soft Fragmentation on the Celestial Sphere
Duff Neill🇺🇸 · Felix Ringer🇺🇸
We develop two approaches to the problem of soft fragmentation of hadrons in a gauge theory for high energy processes. The first approach directly adapts the standard resummation of the parton distribution function's anomalous dimension (that of twist-two local operators) in the forward scattering regime, using $k_{T}$ -factorization and BFKL theory, to the case of the fragmentation function by exploiting the mapping between the dynamics of eikonal lines on transverse-plane to the celestial-sphere. Critically, to correctly resum the anomalous dimension of the fragmentation function under this mapping, one must pay careful attention to the role of regularization, despite the manifest collinear or infra-red finiteness of the BFKL equation. The anomalous dependence on energy in the celestial case, arising due to the mismatch of dimensionality between positions and angles, drives the differences between the space-like and time-like anomalous dimension of parton densities, even in a conformal theory. The second approach adapts an angular-ordered evolution equation, but working in 4-2 $ϵ$ dimensions at all angles. The two approaches are united by demanding that the anomalous dimension in 4-2 $ϵ$ dimensions for the parton distribution function determines the kernel for the angular-ordered evolution to all orders.
Comments:
41 pgs, 1 fig, fixed typos, journal version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2003.02275 [pdf]
JHEP(2020)·27 citations
10
[Submitted on 4 Mar 2020] (cross-list from nucl-ex)
Testing Parameterizations of the Deuteron Quasi-Elastic Peak
Iu. A. Skorodumina · G. V. Fedotov · R. W. Gothe
This study introduces common parameterizations of the quasi-elastic peak in the electron scattering spectrum off deuterium and provides the comparison of the parameterized cross sections with published experimental data. The comparison is performed in the wide $Q^{2}$ range from $\sim$ 0.3 GeV $^{2}$ to $\sim$ 4 GeV $^{2}$ . In this way the performance of the parameterizations and their ability to describe experimental measurements are impartially tested and the conclusion on the description reliability is made.
Comments:
19 pages, 2 figures, available at CLAS12 notes archive as CLAS12 Note 2019-003
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2003.02337 [pdf]
1 citation
11
[Submitted on 5 Mar 2020] (cross-list from nucl-ex)
An extended $R_{Ψ_{m}}^{(2)} (Δ S_{2})$ correlator for detecting and characterizing the Chiral Magnetic Wave
Niseem Magdy (1)🇺🇸 · Mao-Wu Nie (2,3)🇨🇳 · Ling Huang (4,5,6)🇨🇳 · Guo-Liang Ma (4,6)🇨🇳 · Roy. A. Lacey (7) ((1) Department of Physics, University of Illinois at Chicago, IL, USA, (2) Institute of Frontier and Interdisciplinary Science, Shandong University, China, (3) Key Laboratory of Particle Physics and Particle Irradiation, Ministry of Education, Shandong University, China, (4) Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, China, (5) University of Chinese Academy of Sciences, Beijing, China, (6) Key Laboratory of Nuclear Physics and Ion-beam Application (MOE), Institute of Modern Physics, Fudan University, Shanghai, China, (7) Depts. of Chemistry & Physics, Stony Brook University, Stony Brook, NY)🇺🇸
The extended $R_{Ψ_{m}}^{(2)} (Δ S_{2})$ correlator is presented and examined for its efficacy to detect and characterize the quadrupole charge separation ( $Δ S_{2}$ ) associated with the purported Chiral Magnetic Wave (CMW) produced in heavy-ion collisions. Sensitivity tests involving varying degrees of proxy CMW signals injected into events simulated with the Multi-Phase Transport Model (AMPT), show that the $R_{Ψ_{m}}^{(2)} (Δ S_{2})$ correlator provides discernible responses for the background- and CMW-driven charge separation. This distinction could aid identification of the CMW via measurements of the $R_{Ψ_{2}}^{(2)} (Δ S_{2})$ and $R_{Ψ_{3}}^{(2)} (Δ S_{2})$ correlators, relative to the second- ( $Ψ_{2}$ ) and third-order ( $Ψ_{3}$ ) event planes. The tests also indicate a level of sensitivity that would allow for robust experimental characterization of the CMW signal.
Comments:
7 pages 5 figures - submitted for publication
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2003.02396 [pdf]
PLB(2020)·6 citations
12
[Submitted on 5 Mar 2020] (cross-list from hep-ph)
$γ$ -hadron spectra in p + Pb collisions at $s_{NN} = 5.02$ TeV
Man Xie🇨🇳 · Xin-Nian Wang🇨🇳 · Han-Zhong Zhang🇨🇳
Under the assumption that a quark-gluon plasma droplet is produced and its evolution can be described by hydrodynamics in p + A collisions, $γ$ -triggered hadron spectra are studied within a next-to-leading-order perturbative QCD parton model with the medium-modified parton fragmentation functions. The initial conditions and space-time evolution of the small QGP droplet are provided by the superSONIC hydrodynamic model simulations and parton energy loss in such a medium is described by the high-twist (HT) approach. The scaled jet transport coefficient $q^/ T^{3}$ in this HT approach is extracted from single hadron suppression in central A + A collisions at the same colliding energy. Numerical results for this scenario show that $γ$ -hadron spectra at $p_{T}^{γ} = 12 - 40$ GeV/ $c$ are suppressed by 5\% $\sim$ 10\% in the most central 0 - 10\% p + Pb collisions at $s_{NN} = 5.02$ TeV. The suppression becomes weaker at higher transverse momentum of the $γ$ trigger. As a comparison, $γ$ -hadron suppression in Pb + Pb collisions at $s_{NN} = 2.76$ and 5.02 TeV is also predicted.
Comments:
15 pages, 15 figures. v2: published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2003.02441 [pdf]
PRC(2021)·28 citations
13
[Submitted on 5 Mar 2020] (cross-list from hep-th)
Relativistic Dynamics of Fluctuations and QCD Critical Point
Xin An🇺🇸
We review the recent development on a systematic deterministic formalism describing dynamics of both bulk and fluctuations in an arbitrary relativistic hydrodynamic flow carrying conserved charges. In particular, we discuss the implementation of such general formalism near the QCD critical point.
Comments:
4 pages, 1 figure added; revised version accepted for publication in NPA
Subjects:
High Energy Physics — Theory (hep-th); Statistical Mechanics (cond-mat.stat-mech); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2003.02828 [pdf]
NPA(2021)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE