Nuclear Theory·nucl-th

Tuesday·March 8, 2016

18 papers—9 primary·9 cross-listed

10
Neutron Star Mass-Radius Constraints of the Quiescent Low-mass X-ray Binaries X7 and X5 in the Globular Cluster 47 Tuc
Slavko Bogdanov · Craig O. Heinke · Feryal Özel · Tolga Güver
We present Chandra ACIS-S sub-array observations of the quiescent neutron star low-mass X-ray binaries X7 and X5 in the globular cluster 47 Tuc. The large reduction in photon pile-up compared to previous deep exposures enables a substantial improvement in the spectroscopic determination of the neutron star radius and mass of these neutron stars. Modeling the thermal emission from the neutron star surface with a non-magnetized hydrogen atmosphere and accounting for numerous sources of uncertainties, we obtain for the neutron star in X7 a radius of $R = 11. 1_{- 0.7}^{+ 0.8}$ km for an assumed stellar mass of $M = 1.4$ M $_{⊙}$ (68% C.L.). We argue, based on astrophysical grounds, that the presence of a He atmosphere is unlikely for this source. Due to eclipses and variable absorption, the quiescent low-mass X-ray binary X5 provides less stringent constraints, leading to a radius of $R = 9. 6_{- 1.1}^{+ 0.9}$ km, assuming a hydrogen atmosphere and a mass of $M = 1.4$ M $_{⊙}$ . When combined with all other existing spectroscopic radius measurements, these measurements strongly favor radii in the 9.9-11.2 km range for a ~1.5 M $_{⊙}$ neutron star and point to a dense matter equation of state that is somewhat softer than the nucleonic ones that are consistent with laboratory experiments at low densities.
↳ astro-ph.HEnucl-thApJ(2016)·113 citations
11
Nuclear fusion induced by X-rays in a crystal
V. B. Belyaev · M. B. Miller · J. Otto · S. A. Rakityansky
The nuclei that constitute a crystalline lattice, oscillate relative to each other with a very low energy that is not sufficient to penetrate through the Coulomb barriers separating them. An additional energy, which is needed to tunnel through the barrier and fuse, can be supplied by external electromagnetic waves (X-rays or the synchrotron radiation). Exposing to the X-rays the solid compound LiD (lithium-deuteride) for the duration of 111 hours, we have detected 88 events of the nuclear fusion d+Li6 ---> Be8*. Our theoretical estimate agrees with what we observed. One of possible applications of the phenomenon we found, could be the measurements of the rates of various nuclear reactions (not necessarily fusion) at extremely low energies inaccessible in accelerator experiments.
↳ nucl-exnucl-thPRC(2016)·2 citations
12
A new insight into neutrino energy loss by electron capture of iron group nuclei in magnetars surface
Jing-Jing Liu🇨🇳 · Wei-Min Gu🇨🇳
Based on the relativistic mean-field effective interactions theory, and Lai dong model \citep{b37, b38, b39}, we discuss the influences of superstrong magnetic fields (SMFs) on electron Fermi energy, nuclear blinding energy, and single-particle level structure in magnetars surface. By using the method of Shell-Model Monte Carlo (SMMC), and the Random Phase Approximation (RPA) theory, we detailed analyze the neutrino energy loss rates(NELRs) by electron capture (EC) for iron group nuclei in SMFs.
↳ astro-ph.HEastro-ph.SRnucl-thAstrophys.J.Suppl.(2016)·17 citations
13
Parton distribution functions probed in ultraperipheral collisions at the CERN Large Hadron Collider
J. Thomas🇺🇸 · C.A. Bertulani🇺🇸 · N. Brady🇺🇸 · D. B. Clark🇺🇸 · E. Godat🇺🇸 · F. Olness🇺🇸
Vector meson production in ultra-peripheral pA and AA collisions at the CERN Large Hadron Collider (LHC) are very sensitive to Parton Distribution Functions (PDF) as well as to their leading-order, next-to-leading-order, and medium corrections. This process is a complimentary tool to explore the effects of different PDFs in particle production in proton-nucleus and nucleus-nucleus central collisions. Existing and forthcoming data available, e.g., from ALICE and CMS, may be used in conjunction with our theoretical predictions to constrain the PDFs. We make predictions for rapidity distributions and for cross sections of J/ $ψ$ , $ψ (2 S)$ and $Υ$ production at $s_{N N} = 2.76$ TeV and $s_{N N} = 5$ TeV. We use the second energy as representative for the Run 2 of PbPb collisions at the LHC.
↳ hep-phnucl-th4 citations
14
Full jet evolution in quark-gluon plasma and nuclear modification of jet production and jet shape in Pb+Pb collisions at 2.76 ATeV at the LHC
Ning-Bo Chang🇨🇳 · Guang-You Qin🇨🇳
We study the evolution of full jet shower in quark-gluon plasma via solving a set of coupled differential transport equations for the three-dimensional momentum distributions of quarks and gluons contained in the full jets. In our jet evolution equations, we include all partonic splitting processes as well as the collisional energy loss and transverse momentum broadening for both the leading and radiated partons of the full jets. Combining with a realistic (2+1)-dimensional viscous hydrodynamic simulation for the space-time profiles of the hot and dense nuclear medium produced in heavy-ion collisions, we apply our formalism to calculate the nuclear modification of single inclusive full jet spectra, the momentum imbalance of photon-jet and dijet pairs, and jet shape function (at partonic level) in Pb+Pb collisions at 2.76 ATeV. The roles of various jet-medium interaction mechanisms on the full jet modification are studied. We find that the nuclear modification of jet shape is sensitive to the interplay of different interaction mechanisms as well as the energies of the full jets.
↳ hep-phnucl-exnucl-thPRC(2016)·77 citations
15
Model discrimination in pseudoscalar-meson photoproduction
J. Nys🇧🇪 · J. Ryckebusch🇧🇪 · D. G. Ireland🇬🇧 · D. I. Glazier🇬🇧
To learn about a physical system of interest, experimental results must be able to discriminate among models. We introduce a geometrical measure to quantify the distance between models for pseudoscalar-meson photoproduction in amplitude space. Experimental observables, with finite accuracy, map to probability distributions in amplitude space, and the characteristic width scale of such distributions needs to be smaller than the distance between models if the observable data are going to be useful. We therefore also introduce a method for evaluating probability distributions in amplitude space that arise as a result of one or more measurements, and show how one can use this to determine what further measurements are going to be necessary to be able to discriminate among models.
↳ hep-phnucl-thPLB(2016)·15 citations
16
Fluctuations in Charged Particle Multiplicities in Relativistic Heavy-Ion Collisions
Maitreyee Mukherjee🇮🇳 · Sumit Basu🇮🇳 · Subikash Choudhury🇮🇳 · Tapan K. Nayak🇮🇳
Multiplicity distributions of charged particles and their event-by-event fluctuations have been compiled for relativistic heavy-ion collisions from the available experimental data at Brookhaven National Laboratory and CERN and also by the use of an event generator. Multiplicity fluctuations are sensitive to QCD phase transition and to the presence of critical point in the QCD phase diagram. In addition, multiplicity fluctuations provide baselines for other event-by-event measurements. Multiplicity fluctuation expressed in terms of the scaled variance of the multiplicity distribution is an intensive quantity, but is sensitive to the volume fluctuation of the system. The importance of the choice of narrow centrality bins and the corrections of centrality bin width effect for controlling volume fluctuations have been discussed. It is observed that the mean and width of the multiplicity distributions monotonically increase as a function of increasing centrality at all collision energies, whereas the multiplicity fluctuations show minimal variations with centrality. The beam energy dependence shows that the multiplicity fluctuations have a slow rise at lower collision energies and remain constant at higher energies.
↳ nucl-exhep-exhep-phnucl-thJ.Phys.G(2016)·17 citations
17
Functional renormalization group analysis of the soft mode at the QCD critical point
Takeru Yokota🇯🇵 · Teiji Kunihiro🇯🇵 · Kenji Morita🇯🇵
We make an intensive investigation of the soft mode at the quantum chromodynamics (QCD) critical point on the basis of the functional renormalization group (FRG) method in the local potential approximation. We calculate the spectral functions $ρ_{σ, π} (ω, p)$ in the scalar ( $σ$ ) and pseudoscalar ( $π$ ) channels beyond the random phase approximation in the quark--meson model. At finite baryon chemical potential $μ$ with a finite quark mass, the baryon-number fluctuation is coupled to the scalar channel and the spectral function in the $σ$ channel has a support not only in the time-like ( $ω > p$ ) but also in the space-like ( $ω < p$ ) regions, which correspond to the mesonic and the particle--hole phonon excitations, respectively. We find that the energy of the peak position of the latter becomes vanishingly small with the height being enhanced as the system approaches the QCD critical point, which is a manifestation of the fact that the phonon mode is the {\em soft mode} associated with the second-order transition at the QCD critical point, as has been suggested by some authors. Moreover, our extensive calculation of the spectral function in the $(ω, p)$ plane enables us to see that the mesonic and phonon modes have the respective definite dispersion relations $ω_{σ . ph} (p)$ , and it turns out that $ω_{σ} (p)$ crosses the light-cone line into the space-like region, and then eventually merges into the phonon mode as the system approaches the critical point more closely. This implies that the sigma-mesonic mode also becomes soft at the critical point. We also provide numerical stability conditions that are necessary for obtaining the accurate effective potential from the flow equation.
↳ hep-phnucl-thPTEP(2016)·42 citations
18
White Paper on Nuclear Astrophysics
Almudena Arcones🇩🇪 · Dan W. Bardayan🇺🇸 · Timothy C. Beers🇺🇸 · Lee A. Berstein🇺🇸 · Jeffrey C. Blackmon🇺🇸 · Bronson Messer🇺🇸 · B. Alex Brown🇺🇸 · Edward F. Brown🇺🇸 · Carl R. Brune🇺🇸 · Art E. Champagne🇺🇸 · Alessandro Chieffi · Aaron J. Couture🇺🇸 and 31 other authors
This white paper informs the nuclear astrophysics community and funding agencies about the scientific directions and priorities of the field and provides input from this community for the 2015 Nuclear Science Long Range Plan. It summarizes the outcome of the nuclear astrophysics town meeting that was held on August 21-23, 2014 in College Station at the campus of Texas A&M University in preparation of the NSAC Nuclear Science Long Range Plan. It also reflects the outcome of an earlier town meeting of the nuclear astrophysics community organized by the Joint Institute for Nuclear Astrophysics (JINA) on October 9- 10, 2012 Detroit, Michigan, with the purpose of developing a vision for nuclear astrophysics in light of the recent NRC decadal surveys in nuclear physics (NP2010) and astronomy (ASTRO2010). The white paper is furthermore informed by the town meeting of the Association of Research at University Nuclear Accelerators (ARUNA) that took place at the University of Notre Dame on June 12-13, 2014. In summary we find that nuclear astrophysics is a modern and vibrant field addressing fundamental science questions at the intersection of nuclear physics and astrophysics. These questions relate to the origin of the elements, the nuclear engines that drive life and death of stars, and the properties of dense matter. A broad range of nuclear accelerator facilities, astronomical observatories, theory efforts, and computational capabilities are needed. With the developments outlined in this white paper, answers to long standing key questions are well within reach in the coming decade.
↳ astro-ph.SRnucl-exnucl-thPPNP(2017)·55 citations

Affiliations

first authorsco-authorsvia INSPIRE