arXiv subjects

B. Lorstad

Publications and source records attributed to B. Lorstad.

27 records · Page 2Linked to original sources

arXiv1998

Tests of the JETSET Bose-Einstein correlation model in the e+e- annihilation process

Studies of implementation of the simulation of the Bose-Einstein correlation effects in the JETSET particle generator are performed. Analysis of dependance of the one-dimensional correlation function parameters on the presumed boson source size reveals appearance of the effective new length scale, which limits applicability of the simple momentum-shifting mechanism, employed by JETSET to simulate the Bose-Einstein correlation. Two- and three-dimensional correlation functions are analysed as well and compared to the DELPHI data.

hep-ex↗

arXiv1997

Quantum-Statistical Correlations and Single Particle Distributions for Slowly Expanding Systems with Temperature Profile

Competition among particle evaporation, temperature gradient and flow is investigated in a phenomenological manner, based on a simultaneous analysis of quantum statistical correlations and momentum distributions for a non-relativistic, spherically symmetric, three-dimensionally expanding, finite source. The parameters of the model emission function are constrained by fits to neutron and proton momentum distributions and correlation functions in intermediate energy heavy-ion collisions. The temperature gradient is related to the momentum dependence of the radius parameters of the two-particle correlation function, as well as to the momentum-dependent temperature parameter of the single particle spectrum, while a long duration of particle evaporation is found to be responsible for the low relative momentum behavior of the two-particle correlations.

nucl-th↗

arXiv1996

Hydrodynamic Parameterization of NA44 Data on Kaon and Pion Correlations and Spectra

An analytically calculable model has been proposed recently for the simultaneous description of particle spectra and correlations, which is able to explain in a natural manner the $m_t$ scaling of the radius parameters of the Bose--Einstein correlation functions. We present here preliminary results on fitting this model to data sampled by NA44 collaboration in central S + Pb reactions at CERN SPS, which indicate that both pions and kaons freeze-out at a surprisingly low temperature of T approximately 108 MeV.

hep-ph↗

arXiv1996

Numerical Study of Spectrum and HBT Radii for Three-Dimensionally Expanding, Cylindrically Symmetric, Finite Systems

This study is devoted to a detailed numerical testing of the analytical results obtained recently for the $M_t$-scaling of the parameters of the Bose-Einstein correlation functions. Numerical testing of analytical results for the spectrum is also performed, since the geometrical sizes are folded into the momentum distribution in the scaling limiting case. The analytical results are shown to be valid in a wider rapidity-range than thought before.

hep-ph↗

arXiv1996

Bose-Einstein Correlations for Systems with Large Halo

Model-independent considerations are presented for the calculation of Bose-Einstein correlation functions and momentum distributions which describe boson-emitting systems containing a central part surrounded by a large halo. If the characteristic geometrical size of the halo is sufficiently large, the contributions of central part and the halo to the invariant momentum distribution are shown to be separable. The momentum-dependence of the intercept parameter of the correlation function plays a central role. Almost all high energy reactions including lepton-lepton, lepton hadron, hadron-hadron and nuclear reactions are shown to be interpretable as boson emitting systems with large halo. The results are applied to certain high energy heavy ion data at CERN SPS. New insights are obtained for the description of low transverse momentum enhancement of pions.

hep-ph↗

arXiv1995

Bose-Einstein Correlations for Jets and Heavy Ion Reactions

Bose-Einstein correlations and invariant momentum distributions are analyzed for longitudinally expanding finite systems, like jets in elementary particle collisions or systems created in high energy heavy ion reactions. Cross-term generating hyperbolic mixing angle is introduced for HBT. Temporal or spatial temperature gradients are shown to contribute to thermal length and time scales for HBT. Results are illustrated in three figures.

hep-ph↗

arXiv1995

Bose-Einstein Correlations for Three-Dimensionally Expanding, Cylindrically Symmetric, Finite Systems

The parameters of the Bose-Einstein correlation function may obey an {\it $M_t$-scaling}, as observed in $S + Pb$ and $Pb + Pb$ reactions at CERN SPS. This $M_t$-scaling implies that the Bose-Einstein correlation functions view only a small part of the big and expanding system. The full sizes of the expanding system at the last interaction are shown to be measurable with the help the invariant momentum distribution of the emitted particles. A vanishing duration parameter can also be generated in the considered model-class with a specific $M_t$ dependence.

hep-ph↗

arXiv1995

Bose-Einstein Correlations for Expanding Finite Systems or from a Hot Fireball to a Snow-Flurry

Most boson emitting sources contain a core of finite dimensions surrounded by a large halo, due to long-lived resonances like $ω,η,η',K^{0}$ etc. When the Bose-Einstein correlation (BEC) function of the core can be determined we show that its intercept ($λ$) measures, as a function of momentum, the square of the fraction of core particles produced. A simultaneos measurement of BEC and the single-particle distributions can thus determine the characteristics of the core. If the geometrical sizes of the core are sufficiently large the parameters of the BEC function obey the $m_{t}$-scaling observed in $SPb$ and $PbPb$ reactions at CERN. The model can describe the measurements of the single- and two-particle distributions in the central region of $SPb$ reactions. A fit to experimental data shows that the freeze-out of hadrons occurs at a larger volume and at a much lower temperature than that given by the measurement of the inverse slope of the $m_{t}$-spectrum and standard BEC analysis.

hep-ph↗

arXiv1995

Bose-Einstein Correlations for Expanding Finite Systems

There are two length-scales present simultaneously in all the principal directions for three-dimensionally expanding, finite systems. These are discussed in detail for the case of a longitudinally expanding system with a transverse flow and a transverse temperature profile. For systems with large geometrical sizes we find an $m_t$-scaling for the parameters of the Bose-Einstein correlation function, which may be valid in the whole transverse mass region for certain model parameters. In this limit, the Bose-Einstein correlations view only a small part of the source. The large geometrical sizes can be inferred from a simultaneous analysis of the invariant momentum distribution and the Bose-Einstein correlation function. A preliminary analysis of the NA44 data indicates that instead of a small fireball we are observing a big and expanding snowball in $S + Pb $ reactions at CERN SPS energies.

hep-ph↗