(PF2)-P-3 neutron superfluidity in neutron stars and three-body force effect

We investigate the (PF2)-P-3 neutron superfluidity in beta-stable neutron star matter and neutron stars by using the BCS theory and the Brueckner-Hartree-Fock approach. We adopt the Argonne V-18 potential supplemented with a microscopic three-body force as the realistic nucleon-nucleon interaction. We have concentrated on studying the three-body force effect on the (PF2)-P-3 neutron pairing gap. It is found that the three-body force effect is to enhance remarkably the (PF2)-P-3 neutron superfluidity in neutron star matter and neutron stars.

Neutron (PF2)-P-3 superfluidity in neutron matter and the effect of microscopic three-body force

The neutron (PF2)-P-3 pairing gap in pure neutron matter has been studied by using the Brueckner-Hartree-Fock( BHF) approach and the BCS theory. We have concentrated our attention on investigating the three-body force effect on the neutron superfluidity in the (PF2)-P-3 channel. The calculated results indicate that the three-body force enhances remarkably the (PF2)-P-3 superfluidity in neutron matter. When adopting the BHF single-particle spectrum, the three-body force turns out to increase the maximum value of the pairing gap from about 0.22 MeV to about 0.5 MeV.

Probing density-dependent symmetry energy by using the double n/p ratio

Based on a transport model IBUU04, the double n/p ratio is studied. It is found that the double n/p ratio has almost the same sensitivity to the density dependence of nuclear symmetry energy as the single n/p ratio does. Because the double n/p ratio of nucleon emissions taken from two reaction systems can reduce systemic errors effectively, it is thus more useful for constraining the density-dependent symmetry energy further.

Measurement of the Bottom Quark Contribution to Nonphotonic Electron Production in p plus p Collisions at root s=200 GeV

The contribution of B meson decays to nonphotonic electrons, which are mainly produced by the semileptonic decays of heavy-flavor mesons, in p + p collisions at root s = 200 GeV has been measured using azimuthal correlations between nonphotonic electrons and hadrons. The extracted B decay contribution is approximately 50% at a transverse momentum of p(T) >= 5 GeV/c. These measurements constrain the nuclear modification factor for electrons from B and D meson decays. The result indicates that B meson production in heavy ion collisions is also suppressed at high p(T).

X(3915) and X(4350) as New Members in the P-Wave Charmonium Family

The analysis of the mass spectrum and the calculation of the strong decay of P-wave charmonium states strongly purport to explain the newly observed X(3915) and X(4350) as new members in the P-wave charmonium family, i.e., chi'(c0) for X(3915) and chi ''(c2) for X(4350). Under the P-wave charmonium assignment to X(3915) and X(4350), the J(PC) quantum numbers of X(3915) and X(4350) must be 0(++) and 2(++) respectively, which provide important criteria to test the P-wave charmonium explanation for X(3915) and X(4350) proposed by this Letter. The decay behavior of the remaining two P-wave charmonium states with the second radial excitation is predicted, and an experimental search for them is suggested.

gamma cross section in p plus p collisions at root s=200 GeV

We report on a measurement of the gamma(1S + 2S + 3S) -> e(+)e(-) cross section at midrapidity in p + p collisions at root s = 200 GeV. We find the cross section to be 114 +/- 38(stat + fit)(-24)(+23)(syst) pb. Perturbative QCD calculations at next-to-leading order in the color evaporation model are in agreement with our measurement, while calculations in the color singlet model underestimate it by 2 sigma. Our result is consistent with the trend seen in world data as a function of the center-of-mass energy of the collision and extends the availability of gamma data to RHIC energies. The dielectron continuum in the invariant-mass range near the gamma is also studied to obtain a combined yield of e(+)e(-) pairs from the sum of the Drell-Yan process and b-(b) over bar production.

Neutron spectroscopic factors of Ar-34 and Ar-46 from (p,d) transfer reactions

Single-neutron-transfer measurements using (p,d) reactions have been performed at 33 MeV per nucleon with proton-rich Ar-34 and neutron-rich Ar-46 beams in inverse kinematics. The extracted spectroscopic factors are compared to the large-basis shell-model calculations. Relatively weak quenching of the spectroscopic factors is observed between Ar-34 and Ar-46. The experimental results suggest that neutron correlations have a weak dependence on the asymmetry of the nucleus over this isotopic region. The present results are consistent with the systematics established from extensive studies of spectroscopic factors and dispersive optical-model analyses of Ca40-49 isotopes. They are, however, inconsistent with the trends obtained in knockout-reaction measurements.