Nuclear Theory·nucl-th

Wednesday·October 18, 2017

10 papers—4 primary·6 cross-listed

01
[Submitted on 17 Oct 2017]
Gamow-Teller response in the configuration space of DFT-rooted no-core configuration-interaction model
Maciej Konieczka · Markus Kortelainen · Wojciech Satuła
The atomic nucleus is a unique laboratory to study fundamental aspects of the electroweak interaction. This includes a question concerning in medium renormalization of the axial-vector current, which still lacks satisfactory explanation. Study of spin-isospin or Gamow-Teller (GT) response may provide valuable information on both the quenching of the axial-vector coupling constant as well as on nuclear structure and nuclear astrophysics. We have performed a seminal calculation of the GT response by using the no-core-configuration-interaction approach rooted on multi-reference density functional theory (DFT-NCCI). The model treats properly isospin and rotational symmetries and can be applied to calculate both the nuclear spectra and transition rates in atomic nuclei, irrespectively of their mass and particle-number parity. The method is applied to compute the GT strength distribution in selected $N \approx Z$ nuclei including the $p$ -shell $^{8}$ Li and $^{8}$ Be nuclei and the $s d$ -shell well-deformed nucleus $^{24}$ Mg. In order to demonstrate a flexibility of the approach we present also a calculation of the superallowed GT beta decay in doubly-magic spherical $^{100}$ Sn and the low-spin spectrum in $^{100}$ In. It is demonstrated that the DFT-NCCI model is capable to capture the GT response satisfactorily well by using relatively small configuration space exhausting simultaneously the GT sum rule. The model, due to its flexibility and broad range of applicability, may either serve as a complement or even as an alternative to other theoretical approaches including the conventional nuclear shell model.
Comments:
13 pages, 15 figures, submitted to Physical Review C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1710.06172 [pdf]
PRC(2018)·12 citations
02
[Submitted on 17 Oct 2017]
Study of the Q.Q Interaction- Single Particle Behavior to Elliott's Rotations
Arun Kingan · Xiaofei Yu · Larry Zamick
We perform shell model calculations using a quadrupole-quadrupole interaction (Q.Q).We show results in single j shell spaces and the full S-D shell . We show that one gets useful results with Q.Q in both spaces.. We emphasize the importance of the choice of single particle energies in order to obtain the results of Elliott using a Q.Q interaction without the momentum terms. We show a J(J+1) spectrum for a ground state band but with B(E2)'s different from the rotational model. We also show excited J(J-1), J((J-1) and J(J+3) spectra.We find spectra starting with J=0 which have both even J and odd J members.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex); Quantum Physics (quant-ph)
arXiv:
1710.06218 [pdf]
IJMPE(2018)·2 citations
03
[Submitted on 17 Oct 2017]
Thermal dileptons as QCD matter probes at SIS
Florian Seck🇩🇪 · Tetyana Galatyuk🇩🇪 · Ralf Rapp🇺🇸 · Joachim Stroth🇩🇪
Electromagnetic radiation is emitted during the whole course of a heavy-ion collision and can escape from the collision zone without further interactions. This makes it an ideal tool to study the properties of hot and dense QCD matter. To model the space-time evolution of the collision at SIS energies a coarse-graining approach is used to convert transport simulations into meaningful temperatures and densities. These parameters serve as input for the determination of the pertinent radiation of thermal dileptons based on an in-medium $ρ$ spectral function that describes available spectra at ultrarelativistic collision energies. The resulting excitation function of the thermal excess radiation provides a baseline for future measurements by the HADES and CBM experiments at GSI/FAIR, and experiments proposed at NICA and J-PARC.
Comments:
5 pages, 5 figures, contribution to FAIRness 2017 - FAIR next generation scientists - 5th Edition Workshop (May 28, 2017 to June 3, 2017 in Sitges, Spain)
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1710.06256 [pdf]
J.Phys.Conf.Ser.(2018)·4 citations
04
[Submitted on 17 Oct 2017]
Isospin-forbidden electric-dipole capture and the $α (d, γ)^{6}$ Li reaction
Daniel Baye · E.M. Tursunov
At the long-wavelength approximation, $E 1$ transitions are forbidden between isospin-zero states. Hence $E 1$ radiative capture is strongly hindered in reactions involving $N = Z$ nuclei but the $E 1$ astrophysical $S$ factor may remain comparable to, or larger than, the $E 2$ one. Theoretical expressions of the isoscalar and isovector contributions to $E 1$ capture are analyzed in microscopic and three-body approaches in the context of the $α (d, γ)^{6}$ Li reaction. The lowest non-vanishing terms of the operators are derived and the dominant contributions to matrix elements are discussed. The astrophysical $S$ factor computed with some of these contributions in a three-body $α + n + p$ model is in agreement with the recent low-energy experimental data of the LUNA collaboration. This confirms that a correct treatment of the isovector $E 1$ transitions involving small isospin-one admixtures in the wave functions should be able to provide an explanation of the data without adjustable parameter. The exact-masses prescription which is often used to avoid the disappearance of the $E 1$ matrix element in potential models is not founded at the microscopic level and should not be used for such reactions. The importance of capture components from an initial $S$ scattering wave is also discussed.
Comments:
24 pages, 1 table, 2 figures, Figures and text updated
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR)
arXiv:
1710.06352 [pdf]
J.Phys.G(2018)·29 citations
05
[Submitted on 16 Oct 2017] (cross-list from hep-ph)
Resonances in a sudden chemical freeze-out model
Viktor Begun🇵🇱
The prediction for $p_{T}$ spectra of various resonances produced in Pb+Pb collisions at 2.76 TeV at the LHC in equilibrium and non-equilibrium models is made. It includes the $η$ , $ρ$ (770), $Σ$ (1385), $Λ$ (1520), and $Ξ$ (1530). The apparent differences may allow to distinguish between the models.
Comments:
Minor changes on the request of a referee
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1710.05934 [pdf]
EPJ Web Conf.(2018)·2 citations
06
[Submitted on 16 Oct 2017] (cross-list from hep-ph)
Parton distributions with small-x resummation: evidence for BFKL dynamics in HERA data
Richard D. Ball🇬🇧 · Valerio Bertone🇳🇱 · Marco Bonvini🇮🇹 · Simone Marzani🇮🇹 · Juan Rojo🇳🇱 · Luca Rottoli🇬🇧
We present a determination of the parton distribution functions of the proton in which NLO and NNLO fixed-order calculations are supplemented by NLLx small-x resummation. Deep inelastic structure functions are computed consistently at NLO+NLLx or NNLO+NLLx, while for hadronic processes small-x resummation is included only in the PDF evolution, with kinematic cuts introduced to ensure the fitted data lie in a region where the fixed-order calculation of the hard cross-sections is reliable. In all other respects, the fits use the same methodology and are based on the same global dataset as the recent NNPDF3.1 analysis. We demonstrate that the inclusion of small-x resummation leads to a quantitative improvement in the perturbative description of the HERA inclusive and charm-production reduced cross-sections in the small x region. The impact of the resummation in our fits is greater at NNLO than at NLO, because fixed-order calculations have a perturbative instability at small x due to large logarithms that can be cured by resummation. We explore the phenomenological implications of PDF sets with small-x resummation for the longitudinal structure function $F_{L}$ at HERA, for parton luminosities and LHC benchmark cross-sections, for ultra-high energy neutrino-nucleus cross-sections, and for future high-energy lepton-proton colliders such as the LHeC.
Comments:
70 pages, many figures. Discussion on uncertainties due to subleading logarithmic contributions. Discussion on fits with pseudodata from future high-energy lepton-proton colliders. Updated references. Version to be published in EPJC
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1710.05935 [pdf]
EPJC(2018)·282 citations
07
[Submitted on 17 Oct 2017] (cross-list from hep-ph)
Non-perturbative study of spectral function and its application in Quark Gluon Plasma
Aritra Bandyopadhyay🇮🇳
The thesis contains studies of properties quark-gluon plasma, using some non-perturbative techniques. It contains a brief introduction of quark-gluon plasma (QGP) and discussion on various signatures along with a motivation for this thesis work. It presents the basic mathematical tools and ingredients required for the thesis, i.e. basics of QCD, Imaginary and Real Time Formalism, Hard Thermal Loop perturbation theory (HTLpt), Gribov-Zwanziger (GZ) action, the Correlation Function along with the Spectral Function and Operator Product Expansion (OPE) and QCD in magnetized medium. OPE is used to compute the dilepton rate in intermediate mass range by incorporating the non-perturbative dynamics of QCD through the inclusion of non-vanishing quark and gluon condensates in combination with the Green functions in momentum space. Also the magnetic scale (g^2T) in the HTL perturbation theory, related to the confining properties of the QCD is taken into account using the GZ action through a mass parameter, which reflects a new space-like quark mode in the collective excitation. The impact of this new exciting mode on the DPR has been studied and its important consequences has been discussed. A hot magnetized medium introduces another scale in the system in addition to temperature. Electromagnetic spectral properties and DPR are studied completely analytically in presence of both strong and weak background magnetic fields at finite temperature. The Debye screening in a hot and magnetized medium has been studied which reveals some of the intriguing properties of the medium in presence of both strong and weak magnetic field. Also an important quantity that characterizes the QGP, namely quark number susceptibility has been investigated. Most of the non-perturbative results discussed in this thesis are compared with those of perturbative ones and lattice QCD.
Comments:
233 Pages, PhD Thesis, Successfully defended, based on arXiv:1704.01364, arXiv:1702.02875, arXiv:1609.06969, arXiv:1602.06769 and arXiv:1508.06249
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1710.06226 [pdf]
1 citation
08
[Submitted on 17 Oct 2017] (cross-list from hep-lat)
Spectrum of QCD at Finite Isospin Density
Philipp Scior🇩🇪 · Lorenz von Smekal🇩🇪 · Dominik Smith🇩🇪
We study the phase diagram of QCD at finite isospin density using two flavors of staggered quarks. We investigate the low temperature region of the phase diagram where we find a pion condensation phase at high chemical potential. We started a basic analysis of the spectrum at finite isospin density. In particular, we measured pion, rho and nucleon masses inside and outside of the pion condensation phase. In agreement with previous studies in two-color QCD at finite baryon density we find that the Polyakov loop does not depend on the density in the staggered formulation.
Comments:
8 pages, 7 figures, proceedings of Lattice2017, Granada, Spain
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1710.06314 [pdf]
EPJ Web Conf.(2018)·10 citations
09
[Submitted on 17 Oct 2017] (cross-list from hep-ph)
Quark-antiquark antenna splitting in a medium
Fabio Dominguez🇪🇸 · Carlos A Salgado🇪🇸 · Victor Vila🇪🇸
We study a system in which a quark-antiquark antenna emits a hard gluon in a medium, and an extra very soft emission afterwards. Considering the coherence effects in terms of the survival probability, we can describe the interaction of the $q q ˉ g$ configuration with the medium. We extrapolate previous analyzes of the antenna radiation to the case of two hard splittings inside the medium, and prove that this generalization keeps back the picture of jet quenching with effective emitters in the parton QCD cascade.
Comments:
4 pages, proceedings of the EPS-HEP 2017 conference (Venice, Italy July 2017)
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1710.06320 [pdf]
PoS(2018)·0 citations
10
[Submitted on 17 Oct 2017] (cross-list from hep-ph)
Revised neutrino-gallium cross section and prospects of BEST in resolving the Gallium anomaly
Vladislav Barinov🇷🇺 · Bruce Cleveland🇨🇦 · Vladimir Gavrin🇷🇺 · Dmitry Gorbunov🇷🇺 · Tatiana Ibragimova🇷🇺
O(1) eV sterile neutrino can be responsible for a number of anomalous results of neutrino oscillation experiments. This hypothesis may be tested at short base-line neutrino oscillation experiments, several of which are either ongoing or under construction. Here we concentrate on the so-called Gallium anomaly, found by SAGE and GALLEX experiments, and its foreseeable future tests with BEST experiment at Baksan Neutrino Observatory. We start with a revision of the neutrino-gallium cross section, that is performed by utilizing the recent measurements of the nuclear final state spectra. We accordingly correct the parameters of Gallium anomaly and refine the BEST prospects in testing it and searching for sterile neutrinos. We further evolve the previously proposed idea to investigate the anomaly with Zn-65 artificial neutrino source as a next option available at BEST, and estimate its sensitivity to the sterile neutrino model parameters following the Bayesian approach. We show that after the two stages of operation BEST will make 5 $σ$ -discovery of the sterile neutrinos, if they are behind the Gallium anomaly.
Comments:
7 pages, 8 figures; v2: 8 pages, 9 figures, journal version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1710.06326 [pdf]
PRD(2018)·41 citations

Affiliations

first authorsco-authorsvia INSPIRE