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
08
[Submitted on 5 May 2018] (cross-list from nucl-ex)
The center of mass motion of short-range correlated nucleon pairs studied via the A(e,e'pp) reaction
E.O. Cohen · O. Hen · E. Piasetzky · L.B. Weinstein · M. Duer · A. Schmidt · I. Korover · H. Hakobyan · the CLAS Collaboration
Short-Range Correlated (SRC) nucleon pairs are a vital part of the nucleus, accounting for almost all nucleons with momentum greater than the Fermi momentum (kF). A fundamental characteristic of SRC pairs is having large relative momenta as compared to kF, and smaller center-of-mass (c.m.) which indicates a small separation distance between the nucleons in the pair. Determining the c.m. momentum distribution of SRC pairs is essential for understanding their formation process. We report here on the extraction of the c.m. motion of proton-proton (pp) SRC pairs in Carbon and, for the first time in heavier and ansymetric nuclei: aluminum, iron, and lead, from measurements of the A(e,e'pp) reaction. We find that the pair c.m. motion for these nuclei can be described by a three-dimensional Gaussian with a narrow width ranging from 140 to 170 MeV/c, approximately consistent with the sum of two mean-field nucleon momenta. Comparison with calculations appears to show that the SRC pairs are formed from mean-field nucleons in specific quantum states.
Comments:
Accepted to PRL. 7 pages, 3 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1805.01981 [pdf]
PRL(2018)·70 citations
09
[Submitted on 5 May 2018] (cross-list from hep-ph)
Diffusion-model analysis of pPb and PbPb collisions at LHC energies
P. Schulz🇩🇪 · G. Wolschin🇩🇪
We present an analysis of centrality-dependent pseudorapidity distributions of produced charged hadrons in pPb and PbPb collisions at the LHC energy of sqrt{s_NN}=5.02 TeV, and of minimum-bias pPb collisions at 8.16 TeV within the nonequilibrium-statistical relativistic diffusion model (RDM). In a three-source approach, the role of the fragmentation sources is emphasized. Together with the Jacobian transformation from rapidity to pseudorapidity and the limiting fragmentation conjecture, these are essential for modeling the centrality dependence. For central PbPb collisions, a prediction at the projected FCC energy of sqrt{s_NN}=39 TeV is made.
Comments:
17 pages, 5 figures, 4 tables
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1805.02067 [pdf]
Mod.Phys.Lett.A(2018)·2 citations
10
[Submitted on 5 May 2018] (cross-list from hep-ph)
What is the right formalism to search for resonances? II. The pentaquark chain
JPAC Collaboration: A. Pilloni🇺🇸 · J. Nys🇺🇸 · M. Mikhasenko🇩🇪 · M. Albaladejo🇪🇸 · C. Fernandez-Ramirez🇲🇽 · A. Jackura🇺🇸 · V. Mathieu🇺🇸 · N. Sherrill🇺🇸 · T. Skwarnicki🇺🇸 · A. P. Szczepaniak🇺🇸
We discuss the differences between several partial-wave analysis formalisms used in the construction of three-body decay amplitudes involving fermions. Specifically, we consider the decay Lambda_b -> psi p K- , where the hidden charm pentaquark signal has been reported. We analyze the analytical properties of the amplitudes and separate kinematical and dynamical singularities. The result is an amplitude with the minimal energy dependence compatible with the S-matrix principles.
Comments:
30 pages, 4 figures. Added one section about MacDowell symmetry. Few other references added
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1805.02113 [pdf]
EPJC(2018)·16 citations
11
[Submitted on 7 May 2018] (cross-list from hep-lat)
Systematics of the HAL QCD Potential at Low Energies in Lattice QCD
Takumi Iritani🇯🇵 · Sinya Aoki🇯🇵 · Takumi Doi🇯🇵 · Shinya Gongyo🇯🇵 · Tetsuo Hatsuda🇯🇵 · Yoichi Ikeda🇯🇵 · Takashi Inoue🇯🇵 · Noriyoshi Ishii🇯🇵 · Hidekatsu Nemura🇯🇵 · Kenji Sasaki🇯🇵
The $ΞΞ$ interaction in the $^{1}$ S $_{0}$ channel is studied to examine the convergence of the derivative expansion of the non-local HAL QCD potential at the next-to-next-to-leading order (N $^{2}$ LO). We find that (i) the leading order potential from the N $^{2}$ LO analysis gives the scattering phase shifts accurately at low energies, (ii) the full N $^{2}$ LO potential gives only small correction to the phase shifts even at higher energies below the inelastic threshold, and (iii) the potential determined from the wall quark source at the leading order analysis agrees with the one at the N $^{2}$ LO analysis except at short distances, and thus, it gives correct phase shifts at low energies. We also study the possible systematic uncertainties in the HAL QCD potential such as the inelastic state contaminations and the finite volume artifact for the potential and find that they are well under control for this particular system.
Comments:
23 pages, 13 figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1805.02365 [pdf]
PRD(2019)·70 citations

Affiliations

first authorsco-authorsvia INSPIRE