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Q. H. Zhang

Publications and source records attributed to Q. H. Zhang.

29 records · Page 2Linked to original sources
arXiv1998

Multi-boson effects and the normalization of the two-pion correlation function

The two-pion correlation function can be defined as a ratio of either the measured momentum distributions or the normalized momentum space probabilities. We show that the first alternative avoids certain ambiguities since then the normalization of the two-pion correlator contains important information on the multiplicity distribution of the event ensemble which is lost in the second alternative. We illustrate this explicitly for specific classes of event ensembles.

nucl-th↗
arXiv1998

Multi-pion Bose-Einstein correlations in high energy heavy-ion collisions

Multi-pion correlations and wavepacket size effects on the pion multiplicity distribution, pion momentum distribution and two-pion interferometry are studied. It is shown that multi-pion Bose-Einstein correlations and the wavepacket size cause an abundance of pions at low momentum, increase the mean pion multiplicity and decrease both the apparent radius of the source and the coherent source parameter derived from two-pion interferometry.

hep-ph↗
arXiv1998

Finite coherent length and multi-pion correlation effects on two-pion interferometry

The effects of multi-pion correlations and finite coherent length on two-pion interferometry are studied. It was shown that as the pion multiplicity and coherent length become larger, the apparent radius and the apparent coherent parameters derived from two-pion interferometry become smaller. The influence of the coherent length on the effective temperature is discussed.

hep-ph↗
arXiv1998

Coherent source radius in ppbar collisions

We use a recently derived result to extract from two-pion interferometry data from $p\bar{p}$ collisions the radius of the coherent component in the source. We find a coherent source radius of about $2 fm$.

hep-ph↗
arXiv1997

Coherence effects on pion spectrum distribution

The effects of two kinds of coherent lengths, the wave packet length of the emitter and the radius of the coherent source, on pion spectrum distribution are studied. It is shown that both coherent lengths can cause abundant pions at low momentum, but the DCC size effects on pion spectrum distribution is more important. So observing abundant pions at low momentum may be taken as a signal of DCC effects.

hep-ph↗
arXiv1997

Quantum Mechanical Localization Effects for Bose-Einstein Correlations

For a set of N identical massive boson wavepackets with optimal initial quantum mechanical localization, we calculate the Hanbury-Brown/Twiss (HBT) two-particle correlation function. Our result provides an algorithm for calculating one-particle spectra and two-particle correlations from an arbitrary phase space occupation (q_i,p_i,t_i)_{i=1,N} as e.g. returned by event generators. It is a microscopic derivation of the result of the coherent state formalism, providing explicit finite multiplicity corrections. Both the one- and two-particle spectra depend explicitly on the initial spatial wavepacket width which parametrizes the quantum mechanical wavepacket localization. They provide upper and lower bounds which suggest that a realistic value for this width has the order of the Compton wavelength.

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arXiv1997

What can we learn from three-pion interferometry ?

We address the question which additional information on the source shape and dynamics can be extracted from three-particle Bose-Einstein correlations. For chaotic sources the true three-particle correlation term is shown to be sensitive to the momentum dependence of the saddle point of the source and to its asymmetries around that point. For partially coherent sources the three-pion correlator allows to measure the degree of coherence without contamination from resonance decays. We derive the most general Gaussian parametrization of the two- and three-particle correlator for this case and discuss the space-time interpretation of the corresponding parameters.

nucl-th↗
arXiv1997

Independent domains of disoriented chiral condensate

The probability distribution of a neutral pion fraction from independent domains of disoriented chiral condensate is characterized. The signal for the condensate is still clear for a large number of independent domains if one of them is predominant.

hep-ph↗