Nuclear Theory·nucl-th

Monday·June 25, 2018

8 papers—3 primary·5 cross-listed

01
Lattice calculations for two-component fermion systems with unequal masses: one dimension
Serdar Elhatisari🇩🇪
We consider systems of two-component fermions with unequal masses and interacting via a short-range attractive potential. We discuss the case where the two-component fermions form a shallow dimer with large scattering length. The three-fermion and four-fermion systems with such properties are universal and charazteried by the two-fermion scattering length $a_{ff}$ and the ratio of the mass of spin- $↑$ fermion to the mass of spin- $↓$ fermion, $m_{↑} / m_{↓}$ . In this study using lattice effective field theory we analyze fermion-dimer and dimer-dimer systems, and calculate the universal fermion-dimer and dimer-dimer scattering lengths for various values of the mass ratio $m_{↑} / m_{↓}$ . We find that these universal scattering lengths increase logarithmically with the mass ratio $m_{↑} / m_{↓}$ .
nucl-thcond-mat.quant-gashep-latphysics.atom-phTurk.J.Phys.(2018)·0 citations
02
Asymmetric Relativistic Fermi Gas model for quasielastic lepton-nucleus scattering
M.B. Barbaro🇮🇹 · A. De Pace🇮🇹 · T.W. Donnelly🇺🇸 · J.A. Caballero🇪🇸 · G.D. Megias🇪🇸 · J.W. Van Orden🇺🇸
We develop an asymmetric relativistic Fermi gas model for the study of the electroweak nuclear response in the quasielastic region. The model takes into account the differences between neutron and proton densities in asymmetric (N > Z) nuclei, as well as differences in the neutron and proton separation energies. We present numerical results for both neutral and charged current processes, focusing on nuclei of interest for ongoing and future neutrino oscillation experiments. We point out some important differences with respect to the commonly employed symmetric Fermi gas model.
nucl-thPRC(2018)·11 citations
03
Electron Capture Beta Decay of Partially Polarized Nuclei
Rourav Basak🇺🇸 · Vladimir I. Tsifrinovich🇺🇸
We compute the spin excess for the neutrinos radiated in the process of electron capture beta decay of partially polarized nuclei. The results of computation are presented for the $^{119}$ Sb nuclei polarized by the strong hyperfine field in a ferromagnetic substance. This system was suggested as a possible source of directed neutrino radiation. We directly compute the spin excess of radiated neutrinos and show that it is greater than that estimated previously under simplifying assumptions.
nucl-thnucl-exMod.Phys.Lett.A(2019)·0 citations
04
A nucleation model analysis of neck emission yields in 124Sn+112,124Sn reactions at 26 MeV/nucleon
J. Gauthier🇺🇸 · M. Barbui🇺🇸 · X. Cao🇺🇸 · K. Hagel🇺🇸 · R. Wada🇺🇸 · S. Wuenschel🇺🇸 · J. B. Natowitz🇺🇸
A recent analysis of experimental ternary fission fragment yields using a nucleation moderated statistical equilibrium model reproduced observed yields with fairly good accuracy. In the present work, the same approach is applied to neck emission in peripheral and mid-peripheral 124Sn+112,124Sn collisions at 26A MeV. The model can reasonably reproduce the yields of lithium to silicon isotopes with realistic time and temperature values. A comparison is made between equilibrium constants derived from the present data and those previously obtained for ternary fission of 242Pu.
↳ nucl-exnucl-th0 citations
05
Doubly-Charged Scalars in the Type-II Seesaw Mechanism: Fundamental Symmetry Tests and High-Energy Searches
P. S. Bhupal Dev🇺🇸 · Michael J. Ramsey-Musolf🇺🇸 · Yongchao Zhang🇺🇸
We analyze the sensitivity of low-energy fundamental symmetry tests to interactions mediated by doubly-charged scalars that arise in type-II seesaw models of neutrino mass and their left-right symmetric extensions. We focus on the next generation measurement of the parity-violating asymmetry in Møller scattering planned by the MOLLER collaboration at Jefferson Laboratory. We compare the MOLLER sensitivity to that of searches for charged lepton flavor violation (CLFV) and neutrinoless double beta-decay ( $0 ν β β$ -decay) as well as present and possible future high-energy collider probes. We show that for the simplest type-II seesaw scenario, CLFV searches have the greatest sensitivity. However, in a left-right symmetric extension where the scale of parity-breaking is decoupled from the $S U (2)_{R}$ -breaking scale, the MOLLER experiment will provide a unique probe of scalar triplet interactions in the right-handed sector for a doubly-charged scalar mass up to $\sim$ 10 TeV and help elucidate the mechanism of $0 ν β β$ -decay.
↳ hep-phhep-exnucl-exnucl-thPRD(2018)·65 citations
06
A framework for the chiral extrapolation of the charmed baryon ground-state masses
Yonggoo Heo🇹🇭 · Xioa-Yu Guo🇩🇪 · Matthias F.M. Lutz🇩🇪
We consider the chiral Lagrangian for charmed baryon fields with $J^{P} = \frac{1}{2}^{+}$ or $J^{P} = \frac{3}{2}^{+}$ quantum numbers. A chiral expansion framework for the baryon ground state masses is worked out to N $^{3}$ LO as to compute their dependence on the up, down and strange quark masses for finite box QCD lattice simulations. It is formulated in terms of on-shell meson and baryon masses. The convergence of such a scheme is illustrated with physical masses as taken from the PDG. The counter terms relevant at N $^{3}$ LO are correlated systematically by large- $N_{c}$ sum rules to leading and subleading order in a manner that keeps the renormalization scale invariance of the approach.
↳ hep-phhep-latnucl-thPRD(2018)·4 citations
07
Gap equation with pairing correlations beyond mean field and its equivalence to a Hugenholtz-Pines condition for fermion pairs
L. Pisani · P. Pieri · G. Calvanese Strinati
The equation for the gap parameter represents the main equation of the pairing theory of superconductivity. Although it is formally defined through a single-particle property, physically it reflects the pairing correlations between opposite-spin fermions. Here, we exploit this physical connection and cast the gap equation in an alternative form which explicitly highlights these two-particle correlations, by showing that it is equivalent to a Hugenholtz-Pines condition for fermion pairs. At a formal level, a direct connection is established in this way between the treatment of the condensate fraction in condensate systems of fermions and bosons. At a practical level, the use of this alternative form of the gap equation is expected to make easier the inclusion of pairing fluctuations beyond mean field. As a proof-of-concept of the new method, we apply the modified form of the gap equation to the long-pending problem about the inclusion of the Gorkov-Melik-Barkhudarov correction across the whole BCS-BEC crossover, from the BCS limit of strongly overlapping Cooper pairs to the BEC limit of dilute composite bosons, and for all temperatures in the superfluid phase. Our numerical calculations yield excellent agreement with the recently determined experimental values of the gap parameter for an ultra-cold Fermi gas in the intermediate regime between BCS and BEC, as well as with the available quantum Monte Carlo data in the same regime.
↳ cond-mat.supr-concond-mat.quant-gasnucl-thPRB(2018)·15 citations
08
Efimov effect in a $D$ -dimensional Born-Oppenheimer approach
D. S. Rosa · T. Frederico · G. Krein · M. T. Yamashita
We study a three-body system, formed by two identical heavy bosons and a light particle, in the Born-Oppenheimer approximation for an arbitrary dimension $D$ . We restrict $D$ to the interval $2 < D < 4$ , and derive the heavy-heavy $D$ -dimensional effective potential proportional to $1/ R^{2}$ ( $R$ is the relative distance between the heavy particles), which is responsible for the Efimov effect. We found that the Efimov states disappear once the critical strength of the heavy-heavy effective potential $1/ R^{2}$ approaches the limit $- (D - 2)^{2} /4$ . We obtained the scaling function for the $^{133}$ Cs- $^{133}$ Cs- $^{6}$ Li system as the limit cycle of the correlation between the energies of two consecutive Efimov states as a function of $D$ and the heavy-light binding energy $E_{2}^{D}$ . In addition, we found that the energy of the $(N + 1)^{th}$ excited state reaches the two-body continuum independently of the dimension $D$ when $E_{2}^{D} / E_{3}^{(N)} = 0.89$ , where $E_{3}^{(N)}$ is the $N^{th}$ excited three-body binding energy.
↳ physics.atom-phcond-mat.quant-gasnucl-thquant-phJ.Phys.B(2018)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE