Nuclear Theory·nucl-th

Monday·July 15, 2019

12 papers—8 primary·4 cross-listed

09
[Submitted on 11 Jul 2019] (cross-list from nucl-ex)
Experimental investigation of $α$ -condensation in light nuclei
Jack Bishop🇬🇧 · Tzany Kokalova🇬🇧 · Martin Freer🇬🇧 · L Acosta🇮🇹 · M Assie🇫🇷 · S Bailey🇬🇧 · G Cardella🇮🇹 · N Curtis🇬🇧 · E De Filippo🇮🇹 · D Dell'Aquila🇮🇹 · S De Luca🇮🇹 · L Francalanza🇮🇹 and 20 other authors
Method: To examine signatures of this alpha-condensation, a compound nucleus reaction using 160, 280, and 400 MeV 16O beams impinging on a carbon target was used to investigate the 12C(16O,7a) reaction. This permits a search for near-threshold states in the alpha-conjugate nuclei up to 24Mg. Results: Events up to an alpha-particle multiplicity of 7 were measured and the results were compared to both an Extended Hauser-Feshbach calculation and the Fermi break-up model. The measured multiplicity distribution exceeded that predicted from a sequential decay mechanism and had a better agreement with the multi-particle Fermi break-up model. Examination of how these 7 alpha final states could be reconstructed to form 8Be and 12C(0_2+) showed a quantitative difference in which decay modes were dominant compared to the Fermi break-up model. No new states were observed in 16O, 20Ne, and 24Mg due to the effect of the N-alpha penetrability suppressing the total alpha-particle dissociation decay mode. Conclusion: The reaction mechanism for a high energy compound nucleus reaction can only be described by a hybrid of sequential decay and multi-particle breakup. Highly alpha-clustered states were seen which did not originate from simple binary reaction processes. Direct investigations of near-threshold states in N-alpha systems are inherently impeded by the Coulomb barrier prohibiting the observation of states in the N-alpha decay channel. No evidence of a highly clustered 15.1 MeV state in 16O was observed from (28Si*,12C(0_2+))16O(0_6+) when reconstructing the Hoyle state from 3 alpha-particles. Therefore, no experimental signatures for alpha-condensation were observed.
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1907.05471 [pdf]
PRC(2019)·31 citations
10
[Submitted on 12 Jul 2019] (cross-list from hep-ph)
Predictions of $Υ (4 S) \to h_{b} (1 P, 2 P) π^{+} π^{-}$ transitions
Yun-Hua Chen🇨🇳
In this work, we study the contributions of the intermediate bottomoniumlike $Z_{b}$ states and the bottom meson loops in the heavy quark spin flip transitions $Υ (4 S) \to h_{b} (1 P, 2 P) π^{+} π^{-}$ . Depending on the constructive or destructive interferences between the $Z_{b}$ -exchange and the bottom meson loops mechanisms, we predict two possible branching ratios for each process: BR $_{Υ (4 S) \to h_{b} (1 P) π^{+} π^{-}} ≃ (1. 2_{- 0.4}^{+ 0.8} \times 1 0^{- 6})$ or $(0. 5_{- 0.2}^{+ 0.5} \times 1 0^{- 6})$ , and BR $_{Υ (4 S) \to h_{b} (2 P) π^{+} π^{-}} ≃ (7. 1_{- 1.1}^{+ 1.7} \times 1 0^{- 10})$ or $(2. 4_{- 0.1}^{+ 0.2} \times 1 0^{- 10})$ . The bottom meson loops contribution is found to be much larger than the $Z_{b}$ -exchange contribution in the $Υ (4 S) \to h_{b} (1 P) π π$ transitions, while it can not produce decay rates comparable to the heavy quark spin conserved $Υ (4 S) \to Υ (1 S, 2 S) π π$ processes. We also predict the branch fractions of $ψ (3 S, 4 S) \to h_{c} (1 P) π^{+} π^{-}$ contributed from the charm meson loops.
Comments:
17 pages, 4 figures; the direct gluon hadronization mechanism contribution within QCD multipole expansion discussed, the distributions of the $π π$ and $h_{b} π$ invariant mass spectra, and the angular distribution presented, the branch fractions of $ψ (3 S, 4 S) \to h_{c} (1 P) π^{+} π^{-}$ estimated, more discussions added; version to appear in CPC
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1907.05547 [pdf]
CPC(2020)·7 citations
11
[Submitted on 11 Jul 2019] (cross-list from hep-ph)
Particle Ratios within EPOS, UrQMD and Thermal Models at AGS, SPS and RHIC Energies
Mahmoud Hanafy (Benha U. and WLCAPP, Cairo)🇪🇬 · Abdel Nasser Tawfik (Nile U., ECTP and Johann Wolfgang Goethe-Universitat)🇪🇬 · Muhammad Maher (Helwan U. and WLCAPP, Cairo)🇪🇬 · Werner Scheinast (LHEP JINR, Dubna)🇷🇺
The particle ratios $k^{+} / π^{+}$ , $π^{-} / K^{-}$ , $p ˉ / π^{-}$ , $Λ/ π^{-}$ , $Ω/ π^{-}$ , $p / π^{+}$ , $π^{-} / π^{+}$ , $K^{-} / K^{+}$ , $p ˉ / p$ , $Λ ˉ /Λ$ , $Σ ˉ /Σ$ , $Ω ˉ /Ω$ measured at AGS, SPS and RHIC energies are compared with large statistical ensembles of $100, 000$ events deduced from the CRMC EPOS $1.99$ and the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) hybrid model. In the UrQMD hybrid model two types of phase transitions are taken into account. All these are then confronted to the Hadron Resonance Gas Model. The two types of phase transitions are apparently indistinguishable. Apart from $k^{+} / π^{+}$ , $k^{-} / π^{-}$ , $Ω/ π^{-}$ , $p ˉ / π^{+}$ , and $Ω ˉ /Ω$ , the UrQMD hybrid model agrees well with the CRMC EPOS $1.99$ . Also, we conclude that the CRMC EPOS $1.99$ seems to largely underestimate $k^{+} / π^{+}$ , $k^{-} / π^{-}$ , $Ω/ π^{-}$ , and $p ˉ / π^{+}$ .
Comments:
8 pages, 2 figures, submitted to JETP
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1907.05729 [pdf]
IJMPE(2021)·1 citation
12
[Submitted on 12 Jul 2019] (cross-list from hep-ph)
Compact star properties from an extended linear sigma model
János Takátsy🇭🇺 · Péter Kovács🇭🇺 · Zsolt Szép🇭🇺 · György Wolf🇭🇺
The equation of state provided by effective models of strongly interacting matter should comply with the restrictions imposed by current astrophysical observations of compact stars. Using the equation of state given by the (axial-)vector meson extended linear sigma model, we determine the mass-radius relation and study whether these restrictions are satisfied under the assumption that most of the star is filled with quark matter. We also compare the mass-radius sequence with those given by the equations of state of somewhat simpler models.
Comments:
11 pages, 6 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1907.05841 [pdf]
Universe(2019)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE

Experimental investigation of α-condensation in light nuclei

Predictions of Υ(4S)→hb​(1P,2P)π+π− transitions

Particle Ratios within EPOS, UrQMD and Thermal Models at AGS, SPS and RHIC Energies

Compact star properties from an extended linear sigma model

Affiliations

Experimental investigation of $α$ -condensation in light nuclei

Predictions of $Υ (4 S) \to h_{b} (1 P, 2 P) π^{+} π^{-}$ transitions