Nuclear Theory·nucl-th

Monday·June 17, 2019

5 papers—2 primary·3 cross-listed

03
[Submitted on 14 Jun 2019] (cross-list from hep-lat)
Deuteron-like heavy dibaryons from Lattice QCD
Parikshit Junnarkar🇮🇳 · Nilmani Mathur🇮🇳
We report the first lattice quantum chromodynamics (QCD) study of deuteron( $n p$ )-like dibaryons with heavy quark flavours. These include particles with following dibaryon structures and valence quark contents: $Σ_{c} Ξ_{cc} (uu c u cc)$ , $Ω_{c} Ω_{cc} (sscscc)$ , $Σ_{b} Ξ_{bb} (uu b u bb)$ , $Ω_{b} Ω_{bb} (ss b s bb)$ and $Ω_{cc b} Ω_{c bb} (cc b c bb)$ , and with spin ( $J$ )-parity ( $P$ ), $J^{P} \equiv 1^{+}$ . Using a state-of-the art lattice QCD calculation, after controlling relevant systematic errors, we unambiguously find that the ground state masses of dibaryons $Ω_{c} Ω_{cc} (sscscc)$ , $Ω_{b} Ω_{bb} (ss b s bb)$ and $Ω_{cc b} Ω_{c bb} (cc b c bb)$ are below their respective two-baryon thresholds, suggesting the presence of bound states which are stable under strong and electromagnetic interactions. We also predict their masses precisely. For dibaryons $Σ_{c} Ξ_{cc} (uu c u cc)$ , and $Σ_{b} Ξ_{bb} (uu b u bb)$ , we could not reach to a definitive conclusion about the presence of any bound state due to large systematics associated with these states. We also find that the binding of these dibaryons becomes stronger as they become heavier in mass. This study also opens up the possibility of the existence of many other exotic nuclei, which can be formed through the fusion of heavy baryons, similar to the formation of nuclei of elements in the Periodic Table.
Comments:
version accepted for publication in Phys. Rev. Lett
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1906.06054 [pdf]
PRL(2019)·73 citations
04
[Submitted on 14 Jun 2019] (cross-list from nucl-ex)
Constraining the Neutron Star Compactness: Extraction of the $^{23}$ Al( $p, γ$ ) Reaction Rate for the $r p$ -Process
C. Wolf · C. Langer · F. Montes · J. Pereira · W.-J. Ong · T. Poxon-Pearson · S. Ahn · S. Ayoub · T. Baumann · D. Bazin · P.C. Bender · B.A. Brown and 24 other authors
The $^{23}$ Al( $p, γ$ ) $^{24}$ Si reaction is among the most important reactions driving the energy generation in Type-I X-ray bursts. However, the present reaction-rate uncertainty limits constraints on neutron star properties that can be achieved with burst model-observation comparisons. Here, we present a novel technique for constraining this important reaction by combining the GRETINA array with the neutron detector LENDA coupled to the S800 spectrograph at the National Superconducting Cyclotron Laboratory. The $^{23}$ Al( $d, n$ ) reaction was used to populate the astrophysically important states in $^{24}$ Si. This enables a measurement in complete kinematics for extracting all relevant inputs necessary to calculate the reaction rate. For the first time, a predicted close-lying doublet of a 2 $_{2}^{+}$ and (4 $_{1}^{+}$ ,0 $_{2}^{+}$ ) state in $^{24}$ Si was disentangled, finally resolving conflicting results from two previous measurements. Moreover, it was possible to extract spectroscopic factors using GRETINA and LENDA simultaneously. This new technique may be used to constrain other important reaction rates for various astrophysical scenarios.
Subjects:
Nuclear Experiment (nucl-ex); Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
1906.06091 [pdf]
PRL(2019)·21 citations
05
[Submitted on 14 Jun 2019] (cross-list from nucl-ex)
Calculation of resonance energies from Q-values
Christian Iliadis
Resonance energies are frequently derived from precisely measured excitation energies and reaction Q-values. The latter quantities are usually calculated from atomic instead of nuclear mass differences. This procedure disregards the energy shift caused by the difference in the total electron binding energies before and after the interaction. Assuming that the interacting nuclei in a stellar plasma are fully ionized, this energy shift can have a significant effect, considering that the resonance energy enters exponentially into the expression for the narrow-resonance thermonuclear reaction rates. As an example, the rate of the $^{36}$ Ar(p, $γ$ ) $^{37}$ K reaction is discussed, which, at temperatures below 1 GK, depends only on the contributions of a single resonance and direct capture. In this case, disregarding the energy shift caused by the total electron binding energy difference erroneously enhances the rate by $\approx$ 40\% near temperatures of 70 MK.
Comments:
3 pages, 2 figures
Subjects:
Nuclear Experiment (nucl-ex); Astrophysics of Galaxies (astro-ph.GA); Nuclear Theory (nucl-th)
arXiv:
1906.06282 [pdf]
PRC(2019)·10 citations

Affiliations

first authorsco-authorsvia INSPIRE

Deuteron-like heavy dibaryons from Lattice QCD

Constraining the Neutron Star Compactness: Extraction of the 23Al(p,γ) Reaction Rate for the rp-Process

Calculation of resonance energies from Q-values

Affiliations

Constraining the Neutron Star Compactness: Extraction of the $^{23}$ Al( $p, γ$ ) Reaction Rate for the $r p$ -Process