Influence of Bose-Einstein Statistics on the Antiproton-Proton Annihilation Process

Abstract

Recent observations of angular distributions of TT mesons in p-p i, annihilation indicate a deviation from the predictions of the usual Fermi statistical model. In order to shed light on these phenomena, a modification of the statistical model is studied. We retain the assumption that the transition rate into a given final state is proportional to the probability of finding N free TT mesons in the reaction volume, but express this probability in terms of wave functions symmetrized with respect to particles of like charge. The justification of this assumption is discus sed. The model reproduces the experimental results qualitatively, provided the radius of the interaction volume is between one -half and three -fourths of the pion Compton wave length; the dependence of angular correlation effects on the value of the radius is rather sensitive. Quantitatively, there seems to remain some discrepancy, but we cannot say whether this is due to experi-. mental uncertainties or to some other dynamic effects. In the absence of information on TT-TT interactions and of a fully satisfactory explanation of the mean pion multiplicity for annihilation, we wish to emphasize the preliminary nature of our results. We consider them, however, as an indication that the symmetrization effects discussed here may well play a major role in the analysis of angular distributions although it is too early to say whether or -3-UCRL-9169 not these effects can account, quantitatively for the phenomena. It is pointed out that in this respect the ene'rgy dependence of the angular corre-

Centrality dependence of pion freeze-out radii in Pb-Pb collisions atsNN=2.76 TeV

“…The study of the freeze-out structure and dynamics of this process may reveal important information about the matter properties, such as its equation of state and the nature of the phase transition between deconfined and ordinary hadronic matter [11,12]. Two-pion correlations at low relative momentum were first shown to be sensitive to the interaction volume of the emitting source inp + p collisions by Goldhaber et al 50 years ago [13]. Since then, they were studied in e + + e − [14], hadronand lepton-hadron [15], and heavy-ion [16][17][18][19][20][21][22][23][24][25] collisions.…”

Bose-Einstein correlations in W-pair decays

“…This effect leads to an enhancement of the twoparticle differential cross section for pairs of identical pions close in phase space, which was first observed experimentally in pp collisions [1]. Bose-Einstein correlations were also studied in hadronic Z decays [2,3,4], and observations of these correlations in W-pair production at LEP 2 have already been reported [5][6][7][8][9].…”

Bose–Einstein correlation measurements at CMS

“…Experimentally, the two-particle correlation function C 2 ( q) of identical bosons is defined as the ratio 1 A list of members of the CMS Collaboration and acknowledgements can be found at the end of this issue.…”

“…Bose-Einstein correlations (BEC) of identical-pion pairs resulting in an enhancement at low relative momentum was first observed in pp collisions by Goldhaber, Goldhaber, Lee, and Pais more than 50 years ago [1]. This technique, also known as Hanbury Brown -Twiss (HBT) interferometry, and femtoscopy, has been extensively used to probe the space-time structure of the created system.…”