Nuclear Theory·nucl-th

Thursday·May 28, 2020

7 papers—2 primary·5 cross-listed

01
[Submitted on 27 May 2020]
Quasiparticle properties of a single alpha particle in cold neutron matter
Eiji Nakano🇯🇵 · Kei Iida🇯🇵 · Wataru Horiuchi🇯🇵
Light clusters such as alpha particles and deuterons are predicted to occur in hot nuclear matter as encountered in intermediate-energy heavy-ion collisions and protoneutron stars. To examine the in-medium properties of such light clusters, we consider a much simplified system in which like an impurity, a single alpha particle is embedded in a zero-temperature, dilute gas of non-interacting neutrons. By adopting a non-selfconsistent ladder approximation for the effective interaction between the impurity and the gas, which is often used for analyses of Fermi polarons in a gas of ultracold atoms, we calculate the quasiparticle properties of the impurity, i.e., the energy shift, effective mass, quasiparticle residue, and damping rate.
Comments:
19 pages, 3 figures, version accepted for PRC: discussions on p-wave contributions and the validity range of the model were added
Subjects:
Nuclear Theory (nucl-th); Quantum Gases (cond-mat.quant-gas); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2005.13196 [pdf]
PRC(2020)·19 citations
02
[Submitted on 27 May 2020]
Neutron skin of $^{48}$ Ca consistent with experimental data on skins
Shingo Tagami · Jun Matsui · Maya Takechi · Masanobu Yahiro
[Background]: In our previous paper, we predicted $r_{skin}$ , $r_{p}$ , $r_{n}$ , $r_{m}$ for $^{40 - 60, 62, 64}$ Ca after determining the neutron dripline, using the Gogny-D1S HFB with and without the angular momentum projection (AMP). We found that effects of the AMP are small. Very lately, Tanaka {\it et al.} measured interaction cross sections $σ_{I}$ for $^{42 - 51}$ Ca, determined $r_{m}$ from the $σ_{I}$ , and deduced skin $r_{skin}$ and $r_{n}$ from the $r_{m}$ and the $r_{p} (exp)$ evaluated from the electron scattering. Comparing our results with the data, we find for $^{42 - 48}$ Ca that GHFB and GHFB+AMP reproduce the data on $r_{skin}$ , $r_{n}$ , $r_{m}$ , but not for $r_{p} (exp)$ . [Aim]: Our purpose is to determine a value of $r_{skin}^{48}$ by using GHFB+AMP and the constrained GHFB (cGHFB) in which the calculated value is fitted to $r_{p} (exp)$ . [Results]: For $^{42, 44, 46, 48}$ Ca, cGHFB hardly changes $r_{skin}$ , $r_{m}$ , $r_{n}$ calculated with GHFB+AMP, except for $r_{skin}^{48}$ . For $r_{skin}^{48}$ , the cGHFB result is $r_{skin}^{48} = 0.190$ fm, while $r_{skin}^{48} = 0.159$ fm for GHFB+AMP. We should take the upper and the lower bound of GHFB+AMP and cGHFB. The result $r_{skin}^{48} = 0.159 - 0.190$ fm consists with the $r_{skin}^{48} (σ_{I})$ and the data $r_{skin}^{48} ($ E1 $pE)$ obtained from high-resolution $E 1$ polarizability experiment ( $E 1$ pE). Using the $r_{skin}^{48}$ - $r_{skin}^{208}$ relation with strong correlation of Ref.[3], we transform the data $r_{skin}^{208}$ determined by PREX and $E 1$ pE to the corresponding values, $r_{skin}^{48} (tPREX)$ and $r_{skin}^{48} (t$ E1 $pE)$ . Our result is consistent also for $r_{skin}^{48} (tPREX)$ and $r_{skin}^{48} (t$ E1 $pE)$ .
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2005.13197 [pdf]
6 citations
03
[Submitted on 26 May 2020] (cross-list from hep-ph)
$J / ψ$ meson production in association with an open charm hadron at the LHC: A reappraisal
Hua-Sheng Shao🇫🇷
We critically (re)examine the associated production process of a $J / ψ$ meson plus an open charm hadron at the LHC in the proton-proton ( $pp$ ) and proton-lead ( $p Pb$ ) collisions. Such a process is very intriguing in the sense of tailoring to explore the double parton structure of nucleons and to determine the geometry of partons in nuclei. In order to interpret the existing $pp$ data with the LHCb detector at the center-of-mass energy $s = 7$ TeV, we introduce two overlooked mechanisms for the double parton scattering (DPS) and single parton scattering (SPS) processes. Besides the conventional DPS mode, where the two mesons are produced almost independently in the two separate scattering subprocesses, we propose a novel DPS mechanism that the two constituent (heavy) quarks stemming from two hard scatterings can form into a composite particle, like the $J / ψ$ meson, during the hadronization phase. However, it turns out the corresponding contribution is small in $J / ψ + c c ˉ$ hadroproduction. On the contrary, we point out that the resummation of the initial state logarithms due to gluon splitting into a charm quark pair is crucial to understand the LHCb measurement, which was overlooked in the literature. We perform a proper matching between the perturbative calculations in different initial-quark flavor number schemes, generically referring to the variable flavor number scheme. The new variable flavor number scheme calculation for the process strongly enhance the SPS cross sections, almost closing the discrepancies between theory and experiment. Finally, we present our predictions for the forthcoming LHCb measurement in $p Pb$ collisions at $s_{N N} = 8.16$ TeV. Some interesting observables are exploited to set up the control regions of the DPS signal and to probe the impact-parameter dependent parton densities in lead.
Comments:
32 pages, 20 figures, 7 tables; v2: match to journal version (add a new figure and a few references, fix a few typos)
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2005.12967 [pdf]
PRD(2020)·18 citations
04
[Submitted on 26 May 2020] (cross-list from hep-ph)
The Constituent Counting Rule and Omega Photoproduction
Trevor Reed🇺🇸 · Christopher Leon🇺🇸 · Frank Vera🇺🇸 · Lei Guo🇺🇸 · Brian Raue🇺🇸
The constituent counting ruling (CCR) has been found to hold for numerous hard, exclusive processes. It predicts the differential cross section at high energies and fixed $cos θ_{c . m .}$ should follow $\frac{d σ}{d t} \sim \frac{1}{s ^{n - 2}}$ , where $n$ is the minimal number of constituents involved in the reaction. Here we provide an in-depth analysis of the reaction $γ p \to ω p$ at $θ_{c . m .} \sim 9 0^{\circ}$ using CLAS data with an energy range of $s = 5 - 8$ GeV $^{2}$ , where the CCR has been shown to work in other reactions. We argue for a stringent method to select data to test the CCR and utilize a Taylor-series expansion to take advantage of data from nearby angle bins in our analysis. Naïvely, this reaction would have $n = 9$ (or $n = 10$ if the photon is in a $q q ˉ$ state) and we would expect a scaling of $\sim s^{- 7}$ ( $s^{- 8}$ ). Instead, a scaling of $s^{- (9.08 \pm 0.11)}$ was observed. Explanations for this apparent failure of the naïve CCR assumptions are examined.
Comments:
6 pages, 8 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2005.13067 [pdf]
PRC(2021)·3 citations
05
[Submitted on 27 May 2020] (cross-list from hep-ph)
Modified MIT bag Models -- part I: Thermodynamic consistency, stability windows and symmetry group
Luiz L. Lopes🇧🇷 · Carline Biesdorf🇧🇷 · Débora P. Menezes🇧🇷
In this work we study different variations of the MIT bag model. We start with the so called non-ideal bag model and discuss it in detail. Then we implement a vector interaction in the MIT bag model that simulates a meson exchange interaction and fix the quark-meson coupling constants via symmetry group theory. At the end we propose an original model, inspired by the Boguta-Bodmer models, which allows us to control the repulsion interaction at high densities. For each version of the model we obtain a stability window as predicted by the Bodmer-Witten conjecture and discuss its thermodynamic consistency.
Comments:
14 pages, 10 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2005.13136 [pdf]
Phys.Scripta(2021)·73 citations
06
[Submitted on 27 May 2020] (cross-list from gr-qc)
Conserved charges in general relativity
Sinya Aoki🇯🇵 · Tetsuya Onogi🇯🇵 · Shuichi Yokoyama🇯🇵
We present a precise definition of a conserved quantity from an arbitrary covariantly conserved current available in a general curved spacetime with Killing vectors. This definition enables us to define energy and momentum for matter by the volume integral. As a result we can compute charges of Schwarzschild and BTZ black holes by the volume integration of a delta function singularity. Employing the definition we also compute the total energy of a static compact star. It contains both the gravitational mass known as the Misner-Sharp mass in the Oppenheimer-Volkoff equation and the gravitational binding energy. We show that the gravitational binding energy has the negative contribution at maximum by 68% of the gravitational mass in the case of a constant density. We finally comment on a definition of generators associated with a vector field on a general curved manifold.
Comments:
16 pages (single column), v3 (major revision): more discussion on a compact star included, a comparison with previous results given in the appendix, more references added
Subjects:
General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2005.13233 [pdf]
Int.J.Mod.Phys.A(2021)·35 citations
07
[Submitted on 27 May 2020] (cross-list from nucl-ex)
Measurement of the $^{229}$ Th isomer energy with a magnetic micro-calorimeter
Tomas Sikorsky · Jeschua Geist · Daniel Hengstler · Sebastian Kempf · Loredana Gastaldo · Christian Enss · Christoph Mokry · Jörg Runke · Christoph E. Düllmann · Peter Wobrauschek · Kjeld Beeks · Veronika Rosecker and 4 other authors
We present a measurement of the low-energy (0--60keV) $γ$ ray spectrum produced in the $α$ -decay of $^{233}$ U using a dedicated cryogenic magnetic micro-calorimeter. The energy resolution of $\sim$ $10$ eV, together with exceptional gain linearity, allow us to measure the energy of the low-lying isomeric state in $^{229}$ Th using four complementary evaluation schemes. The most accurate scheme determines the $^{229}$ Th isomer energy to be $8.10 (17)$ eV, corresponding to 153.1(37)nm, superseding in precision previous values based on $γ$ spectroscopy, and agreeing with a recent measurement based on internal conversion electrons. We also measure branching ratios of the relevant excited states to be $b_{29} = 9.3 (6) %$ and $b_{42} = 0.3 (3) %$ .
Comments:
5 pages, 5 figures + supplementary
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th); Instrumentation and Detectors (physics.ins-det)
arXiv:
2005.13340 [pdf]
PRL(2020)·94 citations

Affiliations

first authorsco-authorsvia INSPIRE

Quasiparticle properties of a single alpha particle in cold neutron matter

Neutron skin of 48Ca consistent with experimental data on skins

J/ψ meson production in association with an open charm hadron at the LHC: A reappraisal

The Constituent Counting Rule and Omega Photoproduction

Modified MIT bag Models -- part I: Thermodynamic consistency, stability windows and symmetry group

Conserved charges in general relativity

Measurement of the 229Th isomer energy with a magnetic micro-calorimeter

Affiliations

Neutron skin of $^{48}$ Ca consistent with experimental data on skins

$J / ψ$ meson production in association with an open charm hadron at the LHC: A reappraisal

Measurement of the $^{229}$ Th isomer energy with a magnetic micro-calorimeter