Squeezed Fermions at Relativistic Heavy Ion Colliders

Large back-to-back correlations of observable fermion -- anti-fermion pairs are predicted to appear, if the mass of the fermions is modified in a thermalized medium. The back-to-back correlations of protons and anti-protons are experimentally observable in ultra-relativistic heavy ion collisions, similarly to the Andreev reflection of electrons off the boundary of a superconductor. While quantum statistics suppresses the probability of observing pairs of fermions with nearby momenta, the fermionic back-to-back correlations are positive and of similar strength to bosonic back-to-back correlations.Comment: LaTeX, ReVTeX 12 pages, uses epsf.sty, 2 eps figures, improved presentatio

Back-to-Back Correlations for Finite Expanding Fireballs

Back-to-Back Correlations of particle-antiparticle pairs are related to the in-medium mass-modification and squeezing of the quanta involved. They are predicted to appear when hot and dense hadronic matter is formed in high energy nucleus-nucleus collisions. The survival and magnitude of the Back-to-Back Correlations of boson-antiboson pairs generated by in-medium mass modifications are studied here in the case of a thermalized, finite-sized, spherically symmetric expanding medium. We show that the BBC signal indeed survives the finite-time emission, as well as the expansion and flow effects, with sufficient intensity to be observed at RHIC.Comment: 24 pages, 4 figure

Size fluctuations of the initial source and the event-by-event transverse momentum fluctuations in relativistic heavy-ion collisions

We show that the event-by-event fluctuations of the transverse size of the initial source, which follow directly from the Glauber treatment of the earliest stage of relativistic heavy-ion collisions, cause, after hydrodynamic evolution, fluctuations of the transverse flow velocity at hadronic freeze-out. This in turn leads to event-by-event fluctuations of the average transverse momentum, p_T. Simulations with GLISSANDO for the Glauber phase, followed by a realistic hydrodynamic evolution and statistical hadronization carried out with THERMINATOR, lead to agreement with the RHIC data. In particular, the magnitude of the effect, its centrality dependence, and the weak dependence on the incident energy are properly reproduced. Our results show that bulk of the observed event-by-event p_T fluctuations may be explained by the fluctuations of the size of the initial source.Comment: 5 pages, 4 figures, version accepted in PR

On freeze-out problem in hydro-kinetic approach to A+A collisions

A new method for evaluating spectra and correlations in the hydrodynamic approach is proposed. It is based on an analysis of Boltzmann equations (BE) in terms of probabilities for constituent particles to escape from the interacting system. The conditions of applicability of Cooper-Frye freeze-out prescription are considered within the method. The results are illustrated with a non-relativistic exact solution of BE for expanding spherical fireball as well as with approximate solutions for ellipsoidally expanding ones.Comment: 4 pages including 2 figures, RevTex, stylistic and clarifying corrections are made, submitted to Phys. Rev. Let

Comparison of optical model results from a microscopic Schr\"odinger approach to nucleon-nucleus elastic scattering with those from a global Dirac phenomenology

Comparisons are made between results of calculations for intermediate energy nucleon-nucleus scattering for 12C, 16O, 40Ca, 90Zr, and 208Pb, using optical potentials obtained from global Dirac phenomenology and from a microscopic Schr\"odinger model. Differential cross sections and spin observables for scattering from the set of five nuclei at 65 MeV and 200 MeV have been studied to assess the relative merits of each approach. Total reaction cross sections from proton-nucleus and total cross sections from neutron-nucleus scattering have been evaluated and compared with data for those five targets in the energy range 20 MeV to 800 MeV. The methods of analyses give results that compare well with experimental data in those energy regimes for which the procedures are suited.Comment: 22 pages, 12 figure

Coulomb Distortion Effects for (e,e'p) Reactions at High Electron Energy

We report a significant improvement of an approximate method of including electron Coulomb distortion in electron induced reactions at momentum transfers greater than the inverse of the size of the target nucleus. In particular, we have found a new parametrization for the elastic electron scattering phase shifts that works well at all electron energies greater than 300 $MeV$. As an illustration, we apply the improved approximation to the $(e,e'p)$ reaction from medium and heavy nuclei. We use a relativistic ``single particle'' model for $(e,e'p)$ as as applied to $^{208}Pb(e,e'p)$ and to recently measured data at CEBAF on $^{16}O(e,e'p)$ to investigate Coulomb distortion effects while examining the physics of the reaction.Comment: 14 pages, 3 figures, PRC submitte

Status Report of LNS Accelerator Complex in 2002(IV. Status Report of LNS Accelerator Complex in 2002)

Operation status of an electron accelerator complex at Laboratory of Nuclear Science, Tohoku University is reported. After a completion of a new building containing an experimental vault, the inspection for the radiation safety was done in the beginning of October, 2003, so that most of user machine time was consumed in the latter half of the fiscal year 2002

Status Report of LNS Accelerator Complex in 2001(IV. Status Report of LNS Accelerator Complex in 2001)

The electron accelerator complex at the Laboratory of Nuclear Science, Tohoku University has been operated for various fields of science. A 35-year-old 300 MeV electron linac is still working well. However troubles due to aging is rapidly getting serious. In addition, because of multi-purpose use of the linac many different beam characteristics are requested by the users, so that the operation mode has been complicate. In this report, the operation status of the accelerator complex including major troubles experienced in the fiscal year 2001 is described and future plan is shortly discussed by showing the present machine operation

Quantum Molecular Dynamics Approach to the Nuclear Matter Below the Saturation Density

Quantum molecular dynamics is applied to study the ground state properties of nuclear matter at subsaturation densities. Clustering effects are observed as to soften the equation of state at these densities. The structure of nuclear matter at subsaturation density shows some exotic shapes with variation of the density.Comment: 21 pages of Latex (revtex), 9 Postscript figure