Nuclear Theory·nucl-th

Thursday·August 30, 2018

14 papers—7 primary·7 cross-listed

01
[Submitted on 28 Aug 2018]
Mass-dependence of pseudoscalar meson elastic form factors
Muyang Chen🇨🇳 · Minghui Ding🇨🇳 · Lei Chang🇨🇳 · Craig D. Roberts🇺🇸
A continuum approach to quark-antiquark bound-states is used to determine the electromagnetic form factors of pion-like mesons with masses $m_{0^{-}} / GeV = 0.14$ , $0.47$ , $0.69$ , $0.83$ on a spacelike domain that extends to $Q^{2} ≲ 10$ GeV $^{2}$ . The results enable direct comparisons with contemporary lattice-QCD calculations of heavy-pion form factors at large values of momentum transfer and aid in understanding them. They also reveal, inter alia, that the form factor of the physical pion provides the best opportunity for verification of the factorised hard-scattering formula relevant to this class of exclusive processes and that this capacity diminishes steadily as the meson mass increases.
Comments:
6 pages, 2 figures, 1 table
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1808.09461 [pdf]
PRD(2018)·56 citations
02
[Submitted on 29 Aug 2018]
Two-neutron correlations in a Borromean $^{20} C + n + n$ system: Sensitivity of unbound subsystems
Jagjit Singh🇯🇵 · W. Horiuchi🇯🇵 · L. Fortunato🇮🇹 · A. Vitturi🇮🇹
The structure of $^{22}$ C plays a vital role in the new physics at subshell closure of $N = 16$ in the neutron-rich region. We study the two-neutron correlations in the ground state of the weakly-bound Borromean nucleus $^{22}$ C sitting at the edge of the neutron-drip line and its sensitivity to $core$ - $n$ potential. For the present study, we employ a three-body ( $core + n + n$ ) structure model designed for describing the Borromean system by explicit coupling of unbound continuum states of the subsystem ( $core + n$ ). We use a density-independent contact-delta interaction to describe the neutron-neutron interaction and its strength is varied to fix the binding energy. Along with the ground-state properties of $^{22}$ C, we investigate its electric-dipole and monopole responses, discussing the contribution of various configurations. Our results indicate more configuration mixing as compared to the previous studies in the ground state of $^{22}$ C. However, they strongly depend upon the choice of the $^{20} C$ - $n$ potential as well as the binding energy of $^{22}$ C, which call for new precise measurements for the low-lying continuum structure of the binary system ( $^{20} C + n$ ) and the mass of $^{22}$ C. These measurements will be essential to understand the Borromean three-body system $^{22}$ C with more accuracy.
Comments:
13 pages, 6 figures, To appear in Few-Body Systems (2019)
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1808.09635 [pdf]
Few Body Syst.(2019)·13 citations
03
[Submitted on 29 Aug 2018]
Bound and continuum state $β^{-}$ decay of bare atoms: enhancement of decay rate and changes in $β^{-}$ decay branching
Arkabrata Gupta🇮🇳 · Chirashree Lahiri🇮🇳 · S. Sarkar🇮🇳
We have calculated rates of $β^{-}$ decay to both continuum and bound states separately for some fully ionized (bare) atoms in the mass range A $\approx$ 60-240. One of the motivations of this work is that the previous theoretical calculations were very old and/or informatically incomplete. Probably no theoretical study on this subject has been done in the last three decades. For the calculation, we have derived a framework from the usual $β^{-}$ decay theory used by previous authors. Dependence of the calculated rates on the nuclear radius and neutral atom Q-value have been examined. We have used the latest experimental data for nuclear and atomic observables, such as $β^{-}$ decay Q-value, ionization energy, neutral atom $β^{-}$ decay branchings, neutral atom half-lives etc. Results of $β^{-}$ decay rates for decay to continuum and bound states and the enhancement factor due to the bound state decay for a number of nuclei have been tabulated and compared with the previously calculated values, if available. The effective rate or half-life calculated for bare atom might be helpful to set a limit for the maximum enhancement due to bound state decay. Finally, $β^{-}$ decay branching for bare atom has been calculated. The changes in branching in bare atom compared to that in the neutral atom and for the first time branching flip for a few cases have been obtained. Reason for this branching change has been understood in terms of Q-values of the transitions in the neutral and bare atoms. Verification of this branching change / flip phenomenon in bare atom decay might be of interest for future experiments.
Comments:
To appear in PRC, 25 pages, 20 figures, 2 tables, 1 supplemental matertial
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1808.09717 [pdf]
PRC(2019)·10 citations
04
[Submitted on 29 Aug 2018]
Weak sensitivity of three-body ( $d, p$ ) reactions to $n p$ force models
A. Deltuva
Adiabatic distorted-wave approximation (ADWA) study of three-body $(d, p)$ transfer reactions [G.W. Bailey, N.K. Timofeyuk, and J.A. Tostevin, Phys. Rev. Lett. 117, 162502 (2016)] reported strong sensitivity of cross sections to the neutron-proton $(n p)$ interaction model when the nucleon-nucleus optical potential is nonlocal. The verification of this unusual finding using more reliable methods is aimed for in the present work. A rigorous Faddeev-type three-body scattering theory is applied to the study of $(d, p)$ transfer reactions. The equations for transition operators are solved in the momentum-space partial-wave framework. Differential cross sections for $^{26}$ Al $(d, p)^{27}$ Al reactions are calculated using nonlocal nuclear optical potentials and a number of realistic $n p$ potentials. Only a weak dependence on the $n p$ force model is observed, typically one order of magnitude lower than in the previous ADWA study. The shape of the angular distribution of the experimental data is well reproduced. Cross sections of $(d, p)$ transfer reactions calculated using a rigorous three-body method show little sensitivity to the $n p$ interaction model. This indicates a failure of the ADWA in the context of nonlocal potentials. Some evident shortcomings of the ADWA are pointed out.
Comments:
3.5 pages, 2 figures, to be published in Phys. Rev. C (Rapid Communication)
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1808.09742 [pdf]
PRC(2018)·9 citations
05
[Submitted on 29 Aug 2018]
Elliptic flow in ultra-relativistic collisions with polarized deuterons
Piotr Bozek🇵🇱 · Wojciech Broniowski🇵🇱
Predictions are made for elliptic flow in collisions of polarized deuterons with a heavy nucleus. It is shown that the eccentricity of the initial fireball, evaluated with respect to the deuteron polarization axis perpendicular to the beam direction, has a substantial magnitude for collisions of highest multiplicity. Within the Glauber approach we obtain $\sim 7%$ for the deuteron states with spin projection 0, and $\sim - 3%$ for spin projection $\pm 1$ . We propose to measure the elliptic flow coefficient as the second order harmonic coefficient in the azimuthal distribution of produced charged hadrons with respect to the fixed polarization axis. Collective expansion yields a value of the order of $1%$ for this quantity, as compared to zero in the absence of polarization and/or collectivity. Such a vivid rotational symmetry breaking could be measured with the current experimental accuracy of the relativistic heavy-ion experiments. The effect has a fundamental significance for understanding the nature of dynamics in small systems, as its experimental confirmation would prove the presence of the shape-flow transmutation mechanism, typical of hydrodynamic expansion or rescattering in the later stages of the fireball evolution.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1808.09840 [pdf]
PRL(2018)·17 citations
06
[Submitted on 29 Aug 2018]
The isospin and neutron-to-proton excess dependence of short-range correlations
Jan Ryckebusch🇧🇪 · Wim Cosyn🇧🇪 · Sam Stevens🇧🇪 · Corneel Casert🇧🇪 · Jannes Nys🇧🇪
We provide a systematic study of the isospin composition and neutron-to-proton $(\frac{N}{Z})$ ratio dependence of nuclear short-range correlations (SRC) across the nuclear mass table. We use the low-order correlation operator approximation (LCA) to compute the SRC contribution to the single-nucleon momentum distributions for 14 different nuclei from $A = 4$ to $A = 208$ . Ten asymmetric nuclei are included for which the neutrons outnumber the protons by a factor of up to 1.54. The computed momentum distributions are used to extract the pair composition of the SRC. We find that there is a comprehensive picture for the isospin composition of SRC and their evolution with nucleon momentum. We also compute the non-relativistic kinetic energy of neutrons and protons and its evolution with nuclear mass $A$ and $\frac{N}{Z}$ . Confirming the conclusions from alternate studies it is shown that the minority species (protons) become increasingly more short-range correlated as the neutron-to-proton ratio increases. We forge connections between measured nucleon-knockout quantities sensitive to SRC and single-nucleon momentum distributions. It is shown that the LCA can account for the observed trends in the data, like the fact that in neutron-rich nuclei the protons are responsible for an unexpectedly large fraction of the high-momentum components.
Comments:
8 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1808.09859 [pdf]
PLB(2019)·27 citations
07
[Submitted on 29 Aug 2018]
The influence of the neutron skin and the asymmetry energy on the $π^{-} / π^{+}$ ratio
C. Hartnack🇫🇷 · A. Le Fevre🇩🇪 · Y. Leifels🇩🇪 · J. Aichelin🇫🇷
We use the Isospin Quantum Molecular Dynamics model (IQMD) to analyze the centrality dependence of the isospin ratio of pions, $π^{-} / π^{+}$ . We find that the density dependence of the asymmetry potential, the Pauli blocking of the $Δ$ -decay and the thickness of the neutron skin influence in different ways this observable. Using the centrality dependence of this ratio at different beam energies we can disentangle the different contributions and open the way for their experimental determination.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1808.09868 [pdf]
8 citations
08
[Submitted on 28 Aug 2018] (cross-list from hep-ph)
Novel physics opportunities at the HESR-Collider with PANDA at FAIR
Leonid Frankfurt🇮🇱 · Mark Strikman🇺🇸 · Alexei Larionov🇩🇪 · Andreas Lehrach🇩🇪 · Rudolf Maier🇩🇪 · Hendrik van Hees🇩🇪 · Christian Spieles🇩🇪 · Volodymyr Vovchenko🇩🇪 · Horst Stoecker🇩🇪
Exciting new scientific opportunities are presented for the PANDA detector at the High Energy Storage Ring in the redefined $p ˉ p (A)$ collider mode, HESR-C, at the Facility for Antiproton and Ion Research (FAIR) in Europe. The high luminosity, $L \sim 1 0^{31}$ cm $^{- 2}$ s $^{- 1}$ , and a wide range of intermediate and high energies, $s_{NN}$ up to 30 GeV for $p ˉ p (A)$ collisions will allow to explore a wide range of exciting topics in QCD, including the study of the production of excited open charm and bottom states, nuclear bound states containing heavy (anti)quarks, the interplay of hard and soft physics in the dilepton production, and the exploration of the regime where gluons -- but not quarks -- experience strong interaction.
Comments:
29 pages, 5 figures. To appear in the memorial volume for Walter Greiner of the Springer-Nature FIAS Interdisciplinary Science series
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1808.09550 [pdf]
4 citations
09
[Submitted on 29 Aug 2018] (cross-list from nucl-ex)
Antinuclei in Heavy-Ion Collisions
Jinhui Chen🇨🇳 · Declan Keane🇺🇸 · Yugang Ma🇨🇳 · Aihong Tang🇺🇸 · Zhangbu Xu🇺🇸
We review progress in the study of antinuclei, starting from Dirac's equation and the discovery of the positron in cosmic-ray events. The development of proton accelerators led to the discovery of antiprotons, followed by the first antideuterons, demonstrating that antinucleons bind into antinuclei. With the development of heavy-ion programs at the Brookhaven AGS and CERN SPS, it was demonstrated that central collisions of heavy nuclei offer a fertile ground for research and discoveries in the area of antinuclei. In this review, we emphasize recent observations at Brookhaven's Relativistic Heavy Ion Collider and at CERN's Large Hadron Collider, namely, the antihypertriton and the antihelium-4, as well as measurements of the mass difference between light nuclei and antinuclei, and the interaction between antiprotons. Physics implications of the new observations and different production mechanisms are discussed. We also consider implications for related fields, such as hypernuclear physics and space-based cosmic-ray experiments.
Comments:
101 pages, 34 figures, Physics Reports (in press)
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1808.09619 [pdf]
Phys.Rept.(2018)·160 citations
10
[Submitted on 29 Aug 2018] (cross-list from hep-ph)
Interactions between vector mesons and dynamically generated resonances
Meng-Lin Du🇩🇪 · Dilege Gülmez🇩🇪 · Feng-Kun Guo🇨🇳 · Ulf-G. Meißner🇩🇪 · Qian Wang🇩🇪
The $ρρ$ interaction and the corresponding dynamically generated bound states are revisited. We demonstrate that an improved unitarization method is necessary to study the pole structures of amplitudes outside the near-threshold region. In this work, we extend the study of the covariant $ρρ$ scattering in a unitarized chiral theory to the $S$ -wave interactions for the whole vector-meson nonet. We demonstrate that there are unphysical left-hand cuts in the on-shell factorization approach of the Bethe-Salpeter equation. This is in conflict with the correct analytic behavior and makes the so-obtained poles, corresponding to possible bound states or resonances, unreliable. To avoid this difficulty, we employ the first iterated solution of the $N / D$ method and investigate the possible dynamically generated resonances from vector-vector interactions. A comparison with the results from the nonrelativistic calculation is provided as well.
Comments:
24 pages, 12 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1808.09664 [pdf]
EPJC(2018)·48 citations
11
[Submitted on 29 Aug 2018] (cross-list from hep-ph)
Strongly intensive observable between multiplicities in two acceptance windows in a string model
Evgeny Andronov🇷🇺 · Vladimir Vechernin🇷🇺
The strongly intensive observable between multiplicities in two acceptance windows separated in rapidity and azimuth is calculated in the model with quark-gluon strings acting as sources. The dependence of this observable on the two-particle correlation function of a string, the width of observation windows and the rapidity gap between them is analyzed. In the case with independent identical strings the model calculation confirms the strongly intensive character of this observable: it is independent of both the mean number of string and its fluctuation. For this case the peculiarities of its behaviour for particles with different electric charges are also analyzed. In the case when the string fusion processes are taken into account and a formation of strings of a few different types takes place in a collision, this observable is proved to be equal to a weighted average of its values for different string types. Unfortunately, in this case through the weight factors this observable becomes dependent on collision conditions and, strictly speaking, can not be considered any more as strongly intensive variable. For a comparison the results of the calculation of considered observable with the PYTHIA event generator are also presented.
Comments:
20 pages, 9 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1808.09770 [pdf]
EPJA(2019)·26 citations
12
[Submitted on 29 Aug 2018] (cross-list from hep-ph)
Two particle azimuthal harmonics in pA collisions
Manyika Kabuswa Davy🇨🇳 · Cyrille Marquet🇫🇷 · Yu Shi🇨🇳 · Bo-Wen Xiao🇨🇳 · Cheng Zhang🇨🇳
We compute two-particle production in p+A collisions and extract azimuthal harmonics, using the dilute-dense formalism in the Color Glass Condensate framework. The multiple scatterings of the partons inside the projectile proton on the dense gluons inside the target nucleus are expressed in terms of Wilson lines. They generate interesting correlations, which can be partly responsible for the signals of collectivity measured at RHIC and at the LHC. Most notably, while gluon Wilson loops yield vanishing odd harmonics, quark Wilson loops can generate sizable odd harmonics for two particle correlations. By taking both quark and gluon channels into account, we find that the overall second and third harmonics lie rather close to the recent PHENIX data at RHIC.
Comments:
12 pages, 3 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1808.09851 [pdf]
NPA(2019)·18 citations
13
[Submitted on 29 Aug 2018] (cross-list from hep-ph)
Probing the gluon TMDs with quarkonia
Jean-Philippe Lansberg🇫🇷 · Cristian Pisano🇮🇹 · Florent Scarpa🇫🇷 · Marc Schlegel🇺🇸
We briefly review how quarkonium hadroproduction can be used to access the polarised and unpolarised gluon TMDs.
Comments:
6 pages, 4 figures. LaTeX, uses PoS.cls. Contribution to the proceedings of the XXVI International Workshop on Deep-Inelastic Scattering and Related Subjects (DIS2018), 16-20 April 2018, Kobe, Japan
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1808.09866 [pdf]
PoS(2018)·2 citations
14
[Submitted on 29 Aug 2018] (cross-list from hep-ph)
Theoretical analysis of double parton scatterings in quarkonium production in proton-proton collisions at the LHC
Nodoka Yamanaka🇫🇷 · Jean-Philippe Lansberg🇫🇷 · Hua-Sheng Shao🇫🇷 · Yu-Jie Zhang🇨🇳
The production process of quarkonia in proton-proton (pp) collision is a very good probe of the parton structure of the proton. Recent experimental data of the production of J/psi+vector boson or quarkonium pairs at the LHC and Tevatron suggest the relevance of double parton scatterings (DPS). We discuss here the single parton scattering (SPS) contribution to the J/psi +Z, J/psi +W, and J/psi +J/psi productions in hadron collisions. By revisiting the computations of the SPS contributions to the J/psi+Z and J/psi +W productions, we demonstrate that the ATLAS data in fact show evidence for DPS.
Comments:
6 pages, 7 figures, Proceedings of the XXVI International Workshop on Deep Inelastic Scattering and Related Subjects (DIS2018), 16- 20 April 2018, Kobe, Japan
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1808.09884 [pdf]
PoS(2018)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE