Nuclear Theory·nucl-th

Friday·June 7, 2019

13 papers—5 primary·8 cross-listed

01
[Submitted on 5 Jun 2019]
Near-threshold $η^{'}$ meson production in $π^{-} A$ reactions
E.Ya.Paryev🇷🇺
We study the inclusive near-threshold production of $η^{'}$ mesons in $π^{-}$ meson-nucleus reactions on the basis of the first-collision model relying on the nuclear spectral function and including incoherent processes of $η^{'}$ production in $π^{-}$ meson--proton collisions. The model accounts for the absorption of initial $π^{-}$ and final $η^{'}$ mesons, the binding of intranuclear protons and their Fermi motion, as well as the effect of the scalar $η^{'}$ --nucleus potential (or the in-medium shift of the $η^{'}$ meson mass) on these processes. We calculate the differential and total cross sections for $η^{'}$ production off carbon and tungsten nuclei at laboratory angles of 0 $^{\circ}$ --10 $^{\circ}$ and 10 $^{\circ}$ --45 $^{\circ}$ by $π^{-}$ mesons with momentum of 1.7 GeV/c, which is close to the threshold momentum for $η^{'}$ creation on a free target proton at rest. We show that the calculated $η^{'}$ production cross sections are larger than those, studied earlier in the $η^{'}$ photoproduction reactions, by about two orders of magnitude. We also demonstrate that the high absolute values of the present differential and total $η^{'}$ production cross sections in the momentum ranges of 0.2--0.3 GeV/c and 0.1--0.6 GeV/c, respectively, possess a high sensitivity to changes in the in-medium shift of the $η^{'}$ mass. This offers the possibility of evaluating the above shift at these momenta from the respective data, which could be taken in future experiments at the GSI pion beam facility or at J-PARC.
Comments:
12 pages. arXiv admin note: text overlap with arXiv:1806.00303
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1906.02185 [pdf]
NPA(2019)·2 citations
02
[Submitted on 5 Jun 2019]
Absence of hindrance in microscopic $^{12}$ C+ $^{12}$ C fusion study
K. Godbey · C. Simenel · A. S. Umar
Background: Studies of low-energy fusion of light nuclei are important in astrophysical modeling, with small variations in reaction rates having a large impact on nucleosynthesis yields. Due to the lack of experimental data at astrophysical energies, extrapolation and microscopic methods are needed to model fusion probabilities. Purpose: To investigate deep sub-barrier $^{12}$ C+ $^{12}$ C fusion cross sections and establish trends for the $S$ factor. Method: Microscopic methods based on static Hartree-Fock (HF) and time-dependent Hartree-Fock (TDHF) mean-field theory are used to obtain $^{12}$ C+ $^{12}$ C ion-ion fusion potentials. Fusion cross sections and astrophysical $S$ factors are then calculated using the incoming wave boundary condition (IWBC) method. Results: Both density-constrained frozen Hartree-Fock (DCFHF) and density-constrained TDHF (DC-TDHF) predict a rising $S$ factor at low energies, with DC-TDHF predicting a slight damping in the deep sub-barrier region ( $\approx 1$ ~MeV). Comparison between DC-TDHF calculations and maximum experimental cross-sections in the resonance peaks are good. However the discrepancy in experimental low energy results inhibits interpretation of the trend. Conclusions: Using the fully microscopic DCFHF and DC-TDHF methods, no $S$ factor maximum is observed in the $^{12}$ C+ $^{12}$ C fusion reaction. In addition, no extreme sub-barrier hindrance is predicted at low energies. The development of a microscopic theory of fusion including resonance effects, as well as further experiments at lower energies must be done before the deep sub-barrier behavior of the reaction can be established.
Comments:
9 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1906.02268 [pdf]
PRC(2019)·33 citations
03
[Submitted on 4 Jun 2019]
Light (anti)nuclei production in Cu+Cu collisions at $s_{NN} = 200$ GeV
Liu Feng-Xian🇨🇳 · Chen Gang🇨🇳 · She Zhi-Lei🇨🇳 · Zhou Dai-Mei🇨🇳 · Xie Yi-Long🇨🇳
The production of light (anti)nuclei have been investigated using the dynamically constrained phase-space coalescence model based on the final-state hadrons generated by the PACIAE model in Cu+Cu collisions at $s_{NN} = 200$ GeV with $∣ η ∣ < 0.5$ and $0 < p_{T} < 8$ GeV/c. The results show that there is a strong centrality dependence of yields of $d$ , $d$ , $^{3} He$ , $^{3} He$ , $^{4} He$ , and $^{4} He$ , i.e., their yields decrease rapidly with the increase of centrality, and the greater the mass is, the greater the dependence shows; whereas their ratio of antinucleus to nucleus and coalescence parameter $B_{A}$ remain constant as the centrality increases. In addition, the yields of (anti)nuclei are strongly dependent on the mass of the (anti)nuclei, indicating that the (anti)nuclei produced have mass scaling properties in high-energy heavy-ion collisions. Our results are consistent with the STAR experimental data.
Comments:
arXiv admin note: text overlap with arXiv:1812.05148 by other authors
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1906.02592 [pdf]
EPJA(2019)·10 citations
04
[Submitted on 6 Jun 2019]
Finite size effects on cumulants of the critical mode
Moussa Agah Nouhou (SUBATECH, Nantes)🇫🇷 · Marcus Bluhm (Wroclaw U. & SUBATECH, Nantes)🇵🇱 · Anna Borer🇫🇷 · Marlene Nahrgang🇫🇷 · Taklit Sami🇫🇷 · Nathan Touroux (SUBATECH, Nantes)🇫🇷
In this work we study the temperature dependence of the equilibrium variance of critical fluctuations near the QCD critical point. In particular, we take the finite size of the fireball created in heavy-ion collisions into account and systematically obtain corrections to the leading-order result. We find that not only is the variance globally reduced in a finite size system, but for certain combinations of parameters a two-peak structure can develop for temperatures near the critical point.
Comments:
Proceedings for the 12th International Conference on The Critical Point and Onset of Deconfinement (CPOD 2018), September 24 - 28, 2018, Mon-Repos, Corfu Island, Greece
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1906.02647 [pdf]
PoS(2019)·8 citations
05
[Submitted on 6 Jun 2019]
New method of analytic continuation of elastic-scattering data to the negative-energy region and asymptotic normalization coefficients for $^{17}$ O and $^{13}$ C
L. D. Blokhintsev · A. S. Kadyrov · A. M. Mukhamedzhanov · D. A. Savin
A new method is proposed for extrapolation of elastic-scattering data to the negative-energy region for a short-range interaction. The method is based on the analytic approximation of the modulus-squared of the partial-wave scattering amplitude. It is shown that the proposed method has an advantage over the traditional one based on continuation of the effective-range function. The new method has been applied to determine the asymptotic normalization coefficients for the $^{17}$ O and $^{13}$ C nuclei in the $n +^{16}$ O and $n +^{12}$ C channels, respectively.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1906.02696 [pdf]
PRC(2019)·8 citations
06
[Submitted on 4 Jun 2019] (cross-list from nucl-ex)
Symmetry energy constraints from GW170817 and laboratory experiments
M.B. Tsang🇺🇸 · W.G. Lynch🇺🇸 · P. Danielewicz🇺🇸 · C.Y. Tsang🇺🇸
The LIGO-Virgo collaboration detection of the binary neutron-star merger event, GW170817, has expanded efforts to understand the Equation of State (EoS) of nuclear matter. These measurements provide new constraints on the overall pressure, but do not elucidate its origins, by not distinguishing the contribution to the pressure from symmetry energy which governs much of the internal structure of a neutron star. By combining the neutron star EoS extracted from the GW170817 event and the EoS of symmetric matter from nucleus-nucleus collision experiments, we extract the symmetry pressure, which is the difference in pressure between neutron and nuclear matter over the density region from 1.2 $ρ_{0}$ to $4.5 ρ_{0}$ . While the uncertainties in the symmetry pressure are large, they can be reduced with new experimental and astrophysical results.
Comments:
arXiv admin note: substantial text overlap with arXiv:1901.07673
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1906.02180 [pdf]
PLB(2019)·59 citations
07
[Submitted on 5 Jun 2019] (cross-list from nucl-ex)
Ground State Electromagnetic Moments of $^{37}$ Ca
A. Klose · K. Minamisono · A. J. Miller · B. A. Brown · D. Garand · J. D. Holt · J. D. Lantis · Y. Liu · B. Maaß · W. Nörtershäuser · S. V. Pineda · D. M. Rossi and 5 other authors
The hyperfine coupling constants of neutron deficient $^{37}$ Ca were deduced from the atomic hyperfine spectrum of the $4 s^{2} S_{1/2}$ $\leftrightarrow$ $4 p^{2} P_{3/2}$ transition in Ca II, measured using the collinear laser spectroscopy technique. The ground-state magnetic-dipole and spectroscopic electric-quadrupole moments were determined for the first time as $μ = + 0.7453 (72) μ_{N}$ and $Q = - 15 (11)$ $e^{2}$ fm $^{2}$ , respectively. The experimental values agree well with nuclear shell model calculations using the universal sd model-space Hamiltonians versions A and B (USDA/B) in the $s d$ -model space with a 95\% probability of the canonical nucleon configuration. It is shown that the magnetic moment of $^{39}$ Ca requires a larger non- $s d$ -shell component than that of $^{37}$ Ca for good agreement with the shell-model calculation, indicating a more robust closed sub-shell structure of $^{36}$ Ca at the neutron number $N$ = 16 than $^{40}$ Ca. The results are also compared to valence-space in-medium similarity renormalization group calculations based on chiral two- and three-nucleon interactions.
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1906.02298 [pdf]
PRC(2019)·20 citations
08
[Submitted on 5 Jun 2019] (cross-list from hep-th)
Equilibrium thermodynamic susceptibilities for a dense degenerate Dirac field
Ashish Shukla🇨🇦
Parity preserving relativistic fluids in four spacetime dimensions admit seven independent thermodynamic susceptibilities at the second order in the hydrodynamic derivative expansion. We compute all parity-even second order thermodynamic susceptibilities for a free massive Dirac field at zero temperature and a nonzero chemical potential, based on the Kubo formulas reported in P. Kovtun and A. Shukla, Kubo formulas for thermodynamic transport coefficients, J. High Energy Phys. 10 (2018) 007. We also compute the second order constitutive relations for the energy-momentum tensor and the conserved current in the absence of external gauge fields.
Comments:
10 pages, 7 figures. v2: Minor typo fixed. v3: Minor presentation improvements; matches version published in PRD
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1906.02334 [pdf]
PRD(2019)·13 citations
09
[Submitted on 6 Jun 2019] (cross-list from astro-ph.HE)
Astrophysical aspects of general relativistic mass twin stars
David Blaschke🇷🇺 · David Edwin Alvarez-Castillo🇷🇺 · Alexander Ayriyan🇷🇺 · Hovik Grigorian🇷🇺 · Noshad Khosravi Lagarni🇷🇺 · Fridolin Weber🇺🇸
In this chapter we will introduce an effective equation of state (EoS) model based on polytropes that serves to study the so called "mass twins" scenario, where two compact stars have approximately the same mass but (significant for observation) quite different radii. Stellar mass twin configurations are obtained if a strong first-order phase transition occurs in the interior of a compact star. In the mass-radius diagram of compact stars, this will lead to a third branch of gravitationally stable stars with features that are very distinctive from those of white dwarfs and neutron stars. We discuss rotating hybrid star sequences in the slow rotation approximation and in full general relativity and draw conclusions for an upper limit on the maximum mass of nonrotating compact stars that has recently be deduced from the observation of the merger event GW170817.
Comments:
47 pages, 10 figures, 9 tables, chapter in "Topics in Strong Gravity: A Modern View on Theories and Experiments", Edited by Cesar Zen Vasconcellos, World Scientific (2020)
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1906.02522 [pdf]
in: "Topics on Strong Gravity" C. A. Zen …·21 citations
10
[Submitted on 5 Jun 2019] (cross-list from astro-ph.HE)
The early life of millisecond magnetars
D I Jones
Some neutron stars may be born spinning fast and with strong magnetic fields---the so-called \emph{millisecond magnetars}. It is important to understand how a star's magnetic axis moves with respect to the spin axis in the star's early life, as this effects both electromagnetic and gravitational wave emission. Previous studies have highlighted the importance of viscous dissipation within the star in this process. We advance this program by additionally considering the effect of the electromagnetic torque. We find an interesting interplay between the viscous dissipation, which makes the magnetic axis orthogonalise with respect to the spin, verses magnetic torques that tend to make the magnetic axis align with the spin axis. We present some results, and highlight areas where our model needs to be made more realistic.
Comments:
To appear in the AIP Proceedings of the Xiamen-CUSTIPEN Workshop on the EOS of Dense Neutron-Rich Matter in the Era of Gravitational Wave Astronomy, Jan. 3-7 2019, Xiamen, China
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1906.02610 [pdf]
AIP Conf.Proc.(2019)·0 citations
11
[Submitted on 6 Jun 2019] (cross-list from hep-ph)
Resummation for the Field-theoretical Derivation of the Negative Magnetoresistance
Kenji Fukushima🇯🇵 · Yoshimasa Hidaka🇯🇵
We show detailed derivation of the electric conductivity of quark matter at finite temperature and density under a magnetic field. We especially focus on the longitudinal electric conductivity along the magnetic direction and establish the field-theoretical description of the negative magnetoresistance as observed in chiral materials. With increasing magnetic field our microscopic calculation leads to changing behavior from approximately quadratic to asymptotically linear dependence of the electric conductivity, while the magnetic dependence is quadratic in the conventional relaxation time approximation. The presented formulation founds a firm basis for the physical interpretation of the negative magnetoresistance as manifestation of the chiral anomaly, as well as it offers general methodology applicable for various transport coefficients.
Comments:
41 pages, 8 figures; JHEP accepted version; some misleading discussions clarified
Subjects:
High Energy Physics — Phenomenology (hep-ph); Strongly Correlated Electrons (cond-mat.str-el); Nuclear Theory (nucl-th)
arXiv:
1906.02683 [pdf]
JHEP(2020)·25 citations
12
[Submitted on 6 Jun 2019] (cross-list from hep-ph)
Leading order corrections to the Bethe-Heitler process in the $γ p \to l^{+} l^{-} p$ reaction
Matthias Heller🇩🇪 · Oleksandr Tomalak🇩🇪 · Marc Vanderhaeghen🇩🇪 · Shihao Wu🇨🇦
The ratio of di-lepton production cross sections on a proton, using the $γ p \to l^{+} l^{-} p$ process, above and below di-muon production threshold allows to extract the effective lepton-proton interaction, which is required to be identical for electrons and muons if lepton universality is exact. To test for a scenario of broken universality at the percent level, of the size which could explain the different proton charge radii extracted from electron scattering and from muonic hydrogen spectroscopy, we evaluate all one-loop QED corrections to this process, including the full lepton mass dependencies. We furthermore show that two-photon exchange processes with both photons attached to the proton line vanish after averaging over di-lepton angles, and estimate the relatively small radiation off the proton. We compare the full one-loop calculation with a soft-photon approximation of the same order, and present estimates for a planned experiment.
Comments:
arXiv admin note: text overlap with arXiv:1802.07174
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1906.02706 [pdf]
PRD(2019)·16 citations
13
[Submitted on 6 Jun 2019] (cross-list from hep-ph)
The CKM unitarity problem: A trace of new physics at the TeV scale?
Benedetta Belfatto🇮🇹 · Revaz Beradze🇬🇪 · Zurab Berezhiani🇮🇹
After the recent high precision determinations of $V_{u s}$ and $V_{u d}$ , the first row of the CKM matrix shows more than $4 σ$ deviation from unitarity. Two possible scenarios beyond the Standard Model can be investigated in order to fill the gap. If a 4th quark $b^{'}$ participates in the mixing, with $∣ V_{u b^{'}} ∣ \sim 0.04$ , then its mass should be no more than 6 TeV or so. A different solution can come from the introduction of the gauge horizontal family symmetry acting between the lepton families and spontaneously broken at the scale of about 6 TeV. Since the gauge bosons of this symmetry contribute to muon decay in positive interference with Standard Model, the Fermi constant is slightly smaller than the muon decay constant so that unitarity is recovered. Also the neutron lifetime problem, that is about $4 σ$ discrepancy between the neutron lifetimes measured in beam and trap experiments, is discussed in the light of the these determinations of the CKM matrix elements.
Comments:
11 pages, 10 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1906.02714 [pdf]
EPJC(2020)·170 citations

Affiliations

first authorsco-authorsvia INSPIRE