Multiplicities of forward-backward particles in16O-emulsion interactions at 4.5 AGeV/c

An exclusive study of the characteristics of interactions accompanied by backward emission (θlab≥ 90°) of shower and grey particles in collisions of a 4.5 AGeV/c 16O beam with emulsion nuclei is carried out. The experimental multiplicity distributions of different particles emitted in the forward (θlab<90°) and backward hemispheres due to the interactions with the two emulsion components (CNO, AgBr) are presented and analyzed. The correlations between the different emitted particles are also investigated. The results indicate that there are signatures for a collective mechanism, which plays a role in the production of particles in the backward hemisphere. Hence, the backward multiplicity distribution of the emitted shower and grey particles at 4.5 AGeV/c incident momentum can be represented by a decay exponential law formula independent of the projectile size. The exponent of the power was found to increase with decreasing target size. The experimental data favor the idea that the backward particles were emitted due to the decay of the system in the latter stages of the reactions.     

利用中-质微分流探测对称能的高密行为

基于同位旋和动量依赖的强子输运模型IBUU04，研究了¹³²Sn+¹²⁴Sn在三种不同碰撞能量、两种不同对称能作用下，中-质微分流随快度的变化关系. 发现中-质微分流的强度随碰撞能量的增大而增强. 在碰撞能量为400 MeV每核子时，中-质微分流对对称能最为敏感. 关键词： 重离子碰撞 中-质微分流 对称能     

Neutron-rich rare isotope production below the Fermi energy and its application to the Texas A&;M RIB upgrade

Recent efforts to produce and separate neutron-rich rare isotopes in peripheral collisions below the Fermi energy are presented. The experiments have been performed at the Cyclotron Institute of Texas A&M University employing beams from the K500 Superconducting Cyclotron. Two magnetic separators were used: the MARS recoil separator and the Superconducting Solenoid Line (BigSol Line). An enhanced production of neutron-rich nuclides in comparison with high-energy fragmentation mechanisms has been observed and attributed to the role of the N/Z and the nuclear periphery of the target. From a practical viewpoint, these reactions below or around the Fermi energy offer a novel way to access very neutron-rich rare isotopes. The experience obtained in the production of rare isotope beams (RIB) below the Fermi energy will be exploited in the ongoing RIB upgrade of the Cyclotron Institute that will involve production, stopping and reacceleration of rare isotopes.     

On two perturbation estimates of the extreme solutions to the equations X ± A*XA = Q

Two perturbation estimates for maximal positive definite solutions of equations X + A*X⁻¹A = Q and X − A*X⁻¹A = Q are considered. These estimates are proved in [Hasanov et al., Improved perturbation Estimates for the Matrix Equations X ± A*X⁻¹A = Q, Linear Algebra Appl. 379 (2004) 113-135]. We derive new perturbation estimates under weaker restrictions on coefficient matrices of the equations. The theoretical results are illustrated by numerical examples.     

Ab initio calculations of energy transfer and non-additivity in the He-Ne laser system

Ab initio calculations were performed for several suggested mechanisms of energy transfer between helium metastable particles and neon. Optimized geometries and excited-state energies were calculated for neon excited-state complexes and the convergence properties of the non-additive contributions to the interaction energies were examined. The most probable excitation-transfer mechanism was found to be based on an energy difference of 0.0674 eV between the triplet excited state of and the singlet excited state of . No theoretical evidence was found for the production of neon singlet excited-state complexes other than 20.0858 to 20.4875 eV by the considered two-, three- and four-body models of energy transfer processes. The energy curves of the reactions involving the excited-state complexes and are provided and compared with the previously reported experimental results on the reaction . The relation between the probability of energy transfer and laser activity is discussed. The non-additive contribution to the total interaction energy of the nominated intermediate complex was found to be negligible, pointing to the possibility of constructing model potentials and simulation of larger systems. Received: 15 December 1998 / Received in final form: 20 March 1999     

Quark-gluon plasma: Status of heavy ion physics

Lattice quantum chromodynamics (QCD), defined on a discrete space-time lattice, leads to a spectacular non-perturbative prediction of a new state of matter, called quark-gluon plasma (QGP), at sufficiently high temperatures or equivalently large energy densities. The experimental programs of CERN, Geneva and BNL, New York of relativistic heavy ion collisions are expected to produce such energy densities, thereby providing us a chance to test the above prediction. After a brief introduction of the necessary theoretical concepts, I will present a critical review of the experimental results already obtained by the various experiments in order to examine whether QGP has already been observed by them.     

Parity violation in electron scattering

Approximations based on the 2PI effective action are used to investigate the process of equilibration in ϕ⁴ theory in 3+1 dimensions, both in the symmetric and broken phase. A special emphasis is put on the study of the kinetic and chemical equilibration.     

New approach to a description of relativistic particle collisions

Relativistic particle collisions are described by the 2-form of a cross product of particle momentum 1-forms. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 42–45, December, 2008.     

Velocity map imaging for low-energy electron–molecule collisions

The development of an experiment for velocity map imaging (VMI) of fragment ions arising from electron–molecule collisions is discussed. The angular distribution of O⁻ from the dissociative attachment and dipolar dissociation of O₂ is measured and compared with the existing data. The details of the technique and its importance to electron–molecule collisions are discussed.