Nuclear Theory·nucl-th

Tuesday·May 8, 2018

11 papers—7 primary·4 cross-listed

01
[Submitted on 4 May 2018]
Statistical hadron-gas treatment of systems created in proton-proton interactions at CERN SPS
V. V. Begun🇵🇱 · V. Vovchenko🇩🇪 · M. I. Gorenstein🇩🇪 · H. Stoecker🇩🇪
We analyze the newest data from the NA61/SHINE collaboration which, in addition to previous results on pions and kaons, include mean multiplicities of $p$ , $Λ$ , and $ϕ$ -mesons produced in inelastic proton-proton (p+p) interactions at $s_{N N} = 6.3 - 17.3$ ~GeV. The canonical ensemble formulation of the ideal hadron resonance gas (HRG) model is used with exact conservation of net baryon number $B = 2$ , electric charge $Q = 2$ , and strangeness $S = 0$ . The chemical freeze-out parameters in p+p interactions are obtained and compared to those in central nucleus-nucleus collisions. Several features of p+p interactions at the CERN SPS within a statistical model are studied: 1) the inclusion of the $ϕ$ -meson yields in thermal fits worsens significantly the fit quality; 2) the data show large event-by-event multiplicity fluctuations in inelastic p+p interactions which can not be explained by a single fireball described by a statistical model; 3) the fits within the canonical ensemble formulation of HRG do not give any improvement over the fits within the grand canonical ensemble formulation, i.e., there are no indications for existence of a single statistical system in p+p inelastic interactions in the considered energy range.
Comments:
5 figures, 4 tables
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1805.01901 [pdf]
PRC(2018)·17 citations
02
[Submitted on 5 May 2018]
Signatures of few-body resonances in finite volume
P. Klos🇩🇪 · S. König🇩🇪 · H.-W. Hammer🇩🇪 · J. E. Lynn🇩🇪 · A. Schwenk🇩🇪
We study systems of bosons and fermions in finite periodic boxes and show how the existence and properties of few-body resonances can be extracted from studying the volume dependence of the calculated energy spectra. Using a plane-wave-based discrete variable representation to conveniently implement periodic boundary conditions, we establish that avoided level crossings occur in the spectra of up to four particles and can be linked to the existence of multi-body resonances. To benchmark our method we use two-body calculations, where resonance properties can be determined with other methods, as well as a three-boson model interaction known to generate a three-boson resonance state. Finding good agreement for these cases, we then predict three-body and four-body resonances for models using a shifted Gaussian potential. Our results establish few-body finite-volume calculations as a new tool to study few-body resonances. In particular, the approach can be used to study few-neutron systems, where such states have been conjectured to exist.
Comments:
13 pages, 10 figures, 2 tables, published version
Subjects:
Nuclear Theory (nucl-th); Quantum Gases (cond-mat.quant-gas); High Energy Physics — Lattice (hep-lat)
arXiv:
1805.02029 [pdf]
PRC(2018)·54 citations
03
[Submitted on 7 May 2018]
Universal scaling of the pion, kaon and proton $p_{T}$ spectra in Pb-Pb collisions at 2.76 TeV
Y.Y. Wang🇨🇳 · L.W. Yang🇨🇳 · X.L. Du🇨🇳 · N. Liu🇨🇳 · L.Y. Qiao🇨🇳 · W.C. Zhang🇨🇳
With the experimental data collected by the ALICE collaboration in Pb-Pb collisions at a center-of-mass energy per nucleon pair 2.76 TeV for six different centralities (0-5 $%$ , 5-10 $%$ , 10-20 $%$ , 20-40 $%$ , 40-60 $%$ and 60-80 $%$ ), we investigate the scaling property of the pion, kaon and proton transverse momentum ( $p_{T}$ ) spectra at these centralities. We show that in the low $p_{T}$ region with $p_{T} \leq$ 2.75 (3.10 and 2.35) GeV/c the pion (kaon and proton) spectra exhibit a scaling behaviour independent of the centrality of the collisions. This scaling behaviour arises when these spectra are presented in terms of a suitable variable, $z = p_{T} / K$ . The scaling parameter $K$ is determined by the quality factor method and is parameterized by $a ⟨ N_{part} ⟩^{b}$ , where $⟨ N_{part} ⟩$ is the average value of the number of participating nucleons, $a$ and $b$ are free parameters, $b$ characterizes the rate at which $ln K$ changes with $ln ⟨ N_{part} ⟩$ . The values of $b$ for pions and kaons are consistent within uncertainties, while they are smaller than that for protons. In the high $p_{T}$ region, due to the suppression of the spectra, a violation of the proposed scaling is observed going from central to peripheral collisions. The more peripheral the collisions are, the more clearly violated the proposed scaling becomes. In the framework of the colour string percolation model, we argue that the pions, kaons and protons originate from the fragmentation of clusters which are formed by strings overlapping and the cluster's fragmentation functions are different for different hadrons. The scaling behaviour of the pion, kaon and proton spectra in the low $p_{T}$ region can be simultaneously explained by the colour string percolation model in a qualitative way.
Comments:
15 pages, 6 figures, accepted by Nucl. Phys. A
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1805.02300 [pdf]
NPA(2018)·3 citations
04
[Submitted on 7 May 2018]
Charged Particle Emissions in High-Frequency Alternative Electric Fields
Dong Bai🇨🇳 · Daming Deng🇨🇳 · Zhongzhou Ren🇨🇳
Proton emission, $α$ decay, and cluster radioactivity play an important role in nuclear physics. We show that high-frequency alternative electric fields could deform Coulomb barriers that trap the charged particle, and raise the possibility of speeding up charged particle emissions. They could also cause anisotropic effects in charged particle emissions, and introduce additional terms in the Geiger-Nuttall laws. Our study may further suggest that, for proton emitters like $^{166}$ Ir, when the electric field is strong, the dominant decay mode could be changed from $α$ decay to proton emission. As high-frequency alternative electric fields correspond to high-frequency laser fields in the dipole approximation, our study could be viewed as a benchmark for future theoretical studies of charged particle emissions in realistic laser fields.
Comments:
14 pages, 3 figures, accepted version
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1805.02379 [pdf]
NPA(2018)·21 citations
05
[Submitted on 7 May 2018]
Can pion spectra in Pb+Pb collisions at CERN SPS energies be described by those in p+p reactions and energy-momentum conservation ? Rapidity distributions of pions in p+p and Pb+Pb collisions at CERN SPS energies
Andrzej Rybicki🇵🇱 · Antoni Szczurek🇵🇱 · Miroslaw Kielbowicz🇵🇱 · Antoni Marcinek🇵🇱 · Vitalii Ozvenchuk🇵🇱 · Łukasz Rozpłochowski🇵🇱
The centrality dependence of rapidity distributions of pions in Pb+Pb reactions can be understood by imposing local energy-momentum conservation in the longitudinal "fire-streaks" of excited matter. With no tuning nor adjustment to the experimental data, the rapidity distribution of pions produced by the fire-streak which we obtained from Pb+Pb collisions reproduces the shape of the experimental pion rapidity distribution in p+p interactions, measured by the NA49 Collaboration at the same energy. The observed difference in the absolute normalization of this distribution can be explained by the difference in the overall energy balance, induced by baryon stopping and strangeness enhancement phenomena occurring in heavy ion collisions. We estimate the latter effects using a collection of SPS experimental data on $π^{\pm}$ , $K^{\pm}$ , net $p$ , and $n$ production in p+p and Pb+Pb reactions. Implications of the above findings are discussed.
Comments:
25 pages, 7 figures, 3 tables
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1805.02552 [pdf]
PRC(2019)·6 citations
06
[Submitted on 7 May 2018]
Alpha and cluster decay half lives in Tungsten isotopes: A microscopic analysis
Nithu Ashok · Antony Joseph
Alpha and cluster decay half lives for W isotopes in the range between 2p drip line and beta stability line are studied. The sensitivity of different Skyrme parametrizations in predicting the alpha decay and probable cluster decay modes from W isotopes have been analysed. The half lives are calculated using UDL. Predicted half lives are compared with ELDM and also with available experimental values. The study also revealed the role of neutron shell closure in cluster decay process.
Comments:
15 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1805.02600 [pdf]
NPA(2018)·9 citations
07
[Submitted on 7 May 2018]
Heavy physics contributions to neutrinoless double beta decay from QCD
A. Nicholson🇺🇸 · E. Berkowitz🇩🇪 · H. Monge-Camacho🇺🇸 · D. Brantley🇺🇸 · N. Garron🇬🇧 · C.C. Chang🇺🇸 · E. Rinaldi🇺🇸 · M.A. Clark🇺🇸 · B. Joo🇺🇸 · T. Kurth🇺🇸 · B. Tiburzi🇺🇸 · P. Vranas🇺🇸 · A. Walker-Loud🇺🇸
Observation of neutrinoless double beta decay, a lepton number violating process that has been proposed to clarify the nature of neutrino masses, has spawned an enormous world-wide experimental effort. Relating nuclear decay rates to high-energy, beyond the Standard Model (BSM) physics requires detailed knowledge of non-perturbative QCD effects. Using lattice QCD, we compute the necessary matrix elements of short-range operators, which arise due to heavy BSM mediators, that contribute to this decay via the leading order $π^{-} \to π^{+}$ exchange diagrams. Utilizing our result and taking advantage of effective field theory methods will allow for model-independent calculations of the relevant two-nucleon decay, which may then be used as input for nuclear many-body calculations of the relevant experimental decays. Contributions from short-range operators may prove to be equally important to, or even more important than, those from long-range Majorana neutrino exchange.
Comments:
Published version. Corrected missing term in chiral expansion, added supplemental material, updated references. The Jupyter notebook (DOI:10.5281/zenodo.1243313) accompanying this work can be found on github https://github.com/callat-qcd/project_0vbb
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1805.02634 [pdf]
PRL(2018)·102 citations

Affiliations

first authorsco-authorsvia INSPIRE

Statistical hadron-gas treatment of systems created in proton-proton interactions at CERN SPS

Signatures of few-body resonances in finite volume

Universal scaling of the pion, kaon and proton pT​ spectra in Pb-Pb collisions at 2.76 TeV

Charged Particle Emissions in High-Frequency Alternative Electric Fields

Can pion spectra in Pb+Pb collisions at CERN SPS energies be described by those in p+p reactions and energy-momentum conservation ? Rapidity distributions of pions in p+p and Pb+Pb collisions at CERN SPS energies

Alpha and cluster decay half lives in Tungsten isotopes: A microscopic analysis

Heavy physics contributions to neutrinoless double beta decay from QCD

Affiliations

Universal scaling of the pion, kaon and proton $p_{T}$ spectra in Pb-Pb collisions at 2.76 TeV