Spin correlations and consequences of quantum-mechanical coherence

The difference in the properties of the spin correlation tensor for factorizable and nonfactorizable two-particle states is analyzed. The inequalities for linear combinations of the components of this tensor are obtained for the case of incoherent mixtures of factorizable two-particle spin states. They include the well known Bell inequalities and can be violated for coherent superpositions of two-particle spin states. The possibility to verify the consequences of the quantum-mechanical coherence is discussed using the angular correlations in the asymmetric (parity violating) decays of the pairs of spin-1/2 particles (muons, top-quarks or lambda-hyperons), the coherence arising either from the production dynamics or due to the effect of quantum statistics.Comment: 11 pages, LaTe

Time Delay Correlations in Chaotic Scattering: Random Matrix Approach

We study the correlations of time delays in a model of chaotic resonance scattering based on the random matrix approach. Analytical formulae which are valid for arbitrary number of open channels and arbitrary coupling strength between resonances and channels are obtained by the supersymmetry method. We demonstrate that the time delay correlation function, though being not a Lorentzian, is characterized, similar to that of the scattering matrix, by the gap between the cloud of complex poles of the $S$-matrix and the real energy axis.Comment: 15 pages, LaTeX, 4 figures availible upon reques

Multiboson effects in multiparticle production

The influence of multiboson effects on pion multiplicities, single-pion spectra and two-pion correlation functions is discussed in terms of an analytically solvable model. The applicability of its basic factorization assumption is clarified. An approximate scaling of the basic observables with the phase space density is demonstrated in the low density (gas) limit. This scaling and also its violation at high densities due to the condensate formation is described by approximate analytical formulae which allow, in principle, for the identification of the multiboson effects among others. For moderate densities indicated by the experimental data, a fast saturation of multiboson effects with the number of contributing cumulants is obtained, allowing for the account of these effects in realistic transport code simulations. At high densities, the spectra are mainly determined by the universal condensate term and the initially narrow Poisson multiplicity distribution approaches a wide Bose-Einstein one. As a result, the intercepts of the inclusive and fixed-$n$ correlation functions (properly normalized to 1 at large relative momenta) approach 2 and 1, respectively and their widths logarithmically increase with the increasing phase space density. It is shown that the neglect of energy-momentum constraints in the model is justified except near a multipion threshold, where these constraints practically exclude the possibility of a very cold condensate production. It is argued that spectacular multiboson effects are likely to be observed only in the rare events containing sufficiently high density (speckle) fluctuations.Comment: 30 pages including 10 figures, LaTex, a revised version of SUBATECH 99-04 (aps1999_mar21_001) resubmitted to Phys. Rev. C; Chapter II made shorter, figure description made more clear, a comparison with most recent works added in Chapter V

Sum rule of the correlation function

We derive a sum rule satisfied by the correlation function of two particles with small relative momenta, which results from the completeness condition of the quantum states.Comment: 6 pages, no macro

Reducing nonideal to ideal coupling in random matrix description of chaotic scattering: Application to the time-delay problem

We write explicitly a transformation of the scattering phases reducing the problem of quantum chaotic scattering for systems with M statistically equivalent channels at nonideal coupling to that for ideal coupling. Unfolding the phases by their local density leads to universality of their local fluctuations for large M. A relation between the partial time delays and diagonal matrix elements of the Wigner-Smith matrix is revealed for ideal coupling. This helped us in deriving the joint probability distribution of partial time delays and the distribution of the Wigner time delay.Comment: 4 pages, revtex, no figures; published versio

Statistics of delay times in mesoscopic systems as a manifestation of eigenfunction fluctuations

We reveal a general explicit relation between the statistics of delay times in one-channel reflection from a mesoscopic sample of any spatial dimension and the statistics of the eigenfunction intensities in its closed counterpart. This opens a possibility to use experimentally measurable delay times as a sensitive probe of eigenfunction fluctuations. For the particular case of quasi-one dimensional geometry of the sample we use an alternative technique to derive the probability density of partial delay times for any number of open channels.Comment: 12 pages; published version with updated reference

Vacuum-field level shifts in a single trapped ion mediated by a single distant mirror

A distant mirror leads to a vacuum-induced level shift in a laser-excited atom. This effect has been measured with a single mirror 25 cm away from a single, trapped barium ion. This dispersive action is the counterpart to the mirror's dissipative effect, which has been shown earlier to effect a change in the ion's spontaneous decay [J. Eschner et al., Nature 413, 495-498 (2001)]. The experimental data are well described by 8-level optical Bloch equations which are amended to take into account the presence of the mirror according to the model in [U. Dorner and P. Zoller, Phys. Rev. A 66, 023816 (2002)]. Observed deviations from simple dispersive behavior are attributed to multi-level effects.Comment: version accepted by PR

Production of para-- and orthopositronium at relativistic heavy ion colliders

We consider the ortho-- and parapositronium production in the process $AA \to AA+$ Ps where A is a nucleus with the charge number Z. The inclusive cross section and the energy distribution of the relativistic Ps are calculated which are of primary interest from the experimental point of view. The accuracy of the corresponding cross sections is given by omitting terms $\sim (Z\alpha )^2/L^2$ for the para--Ps and $\sim (Z\alpha)^2/L$ for the ortho--Ps production where $L=\ln{\gamma^2} \approx 9$ and 16 for the RHIC and the LHC. Within this accuracy the multiphoton (Coulomb) corrections are taken into account. We show that the RHIC and the LHC will be Ps factories with a productions rate of about $10^5 \div 10^8$ relativistic Ps per day. The fraction of the ortho--Ps is expected to be of the same order as that of the para--Ps for Au--Au and Pb--Pb collisions.Comment: 22 pages, 5 figures, RevTeX, misprint correcte