115151673
Identification of baryon resonances in central heavy-ion collisions at energies between 1 and 2 AGeV

Abstract. The mass distributions of baryon resonances populated in near-central collisions of Au on Au and Ni on Ni are deduced by defolding the pt spectra of charged pions by a method which does not depend on a specific resonance shape. In addition the mass distributions of resonances are obtained from the invariant masses of (p, π±) pairs. With both methods the deduced mass distributions are shifted by an average value of −60 MeV/c2 relative to the mass distribution of the free Δ(1232) resonance, the distributions descent almost exponentially towards mass values of 2000 MeV/c2. The observed differences between (p, π−) and (p, π+) pairs indicate a contribution of isospin I = 1/2 resonances. The attempt to consistently describe the deduced mass distributions and the reconstructed kinetic energy spectra of the resonances leads to new insights about the freeze out conditions, i.e. to rather low temperatures and large expansion velocities.
96428988
On the transverse momentum distribution of strange hadrons produced in relativistic heavy ion collisions
Particles with strange quark content produced in the system 1.93A·GeV58Ni on58Ni have been investigated at GSI Darmstadt with the FOPI detector system. The correlation of these produced particles was analyzed with respect to the reaction plane.Λ baryons exhibit a very pronounced sideward flow pattern which is qualitatively similar to the proton flow. However, the kaon (K+,Ks0) flow patterns are significantly different from that of the protons, and their form may be useful to restrict theoretical models on the form of the kaon potential in the nuclear medium.
119275897
A new mass for asymptotically flat manifolds
Abstract In this paper we introduce a mass for asymptotically flat manifolds by using the Gauss–Bonnet curvature. We first prove that the mass is well-defined and is a geometric invariant, if the Gauss–Bonnet curvature is integrable and the decay order τ satisfies τ > n − 4 3 . Motivated by an elegant idea of Lam [35] , we then show a positive mass theorem for this new mass for asymptotically flat graphs over R n . Moreover we obtain various Penrose type inequalities in this case. In these Penrose type inequalities we establish relationship between the new mass and various geometric integrals.
119303730
Annihilation Rate of Heavy 0^{++} P-wave Quarkonium in Relativistic Salpeter Method
Abstract Two-photon and two-gluon annihilation rates of P-wave scalar charmonium and bottomonium up to third radial excited states are estimated in the relativistic Salpeter method. We solved the full Salpeter equation with a well defined relativistic wave function and calculated the transition amplitude using the Mandelstam formalism. Our model dependent estimates for the decay widths: Γ(χc0 → 2γ) = 3.78 keV, Γ(χ′c0 → 2γ) = 3.51 keV, Γ(χb0 → 2γ) = 48.8 eV and Γ(χ′b0 → 2γ) = 50.3 eV. We also give estimates of total widths by the two-gluon decay rates: Γtot(χc0) = 10.3 MeV, Γtot(χ ′ c0) = 9.61 MeV, Γtot(χb0) = 0.887 MeV and Γtot(χ ′ b0) = 0.914 MeV.
117013801
Instantaneous Bethe–Salpeter Equation and Its Exact Solution
We present an approach to solve Bethe-Salpeter (BS) equations exactly without any approximation if the kernel of the BS equations exactly is instantaneous, and take positronium as an example to illustrate the general features of the exact solutions. The key step for the approach is from the BS equations to derive a set of coupled and well-determined integration equations in linear eigenvalue for the components of the BS wave functions equivalenity which may be solvable numerically under a controlled accuracy, even though there is no analytic solution. For positronium, the exact solutions precisely present corrections to those of the corresponding Schrodinger equation in order upsilon(1) (v is the relative velocity) for eigenfunctions, in order upsilon(2) for eigenvalues, and the mixing between S and D components in J(PC) = 1(--) states etc., quantitatively. Moreover, we also point out that there is a questionable step in some existent derivations for the instantaneous BS equations if one is pursuing the exact solutions. Finally, we emphasize that one should take the O(upsilon) corrections emerging in the exact solutions into account accordingly if one is interested in the relativistic corrections for relevant problems to the bound states.
119180431
Empirical constraints on parton energy loss in nucleus–nucleus collisions at RHIC
Abstract We present empirical features of parton energy loss in nucleus–nucleus collisions at RHIC through studies of the spectra and nuclear modification factors ( R A A ) for charged hadrons, neutral pions ( π 0 ) and non-photonic electrons. The flat distribution of R A A at high transverse momentum ( p T ) for a given collision centrality is consistent with a scenario where parton energy loss Δ p T is proportional to p T . The centrality dependence of the parton energy loss indicates the absence of path length dependence in the magnitude of energy loss. The lack of strong path length dependence suggests a dynamical picture where the dense partonic medium undergoes rapid expansion and the density of the medium falls rapidly in the first a few Fermi interval, which may be much shorter than the full path length. Implications of the empirical constraints on the parton energy loss will also be discussed.
122069833
Quantum Phase Transition Like Phenomenon in a Two-Qubit Yang-Baxter System
The quantum phase transition for the “q-deformed” Yang-baxter Hamiltonian has been discussed. The calculation shows when the deformed parameter q approaches 1, there exists a quantum critical point for spectral parameter θ. In this Yang-Baxter system, quantum entanglement and the geometric phase can characterize quantum phase transition.