Study of inclusiveΛproduction ine+e−annihilations at 29 GeV

Abstract

Cross sections are presented for the inclusive production of A hyperons in electron-positron annihilations at &s =29 GeV based on the full 291-pb sample of data taken in the High Resolution Spectrometer experiment at the SLAC e+e storage ring PEP. These results, and the associated correlation analyses, are consistent with the Lund model predictions with the strange diquark suppression ratio 5 fixed at 0.59+0.10+0.18, as compared to the standard Lund value of 0.32. The A multiplicity has been found to be 0. 182+0.020 per event. The opposite-strangeness multiplicity (nAA) has been measured to be 0.046+0.020, whereas the like-strangeness multiplicity (n~~+ ") is 0.009+0.028. A strong correlation is found between A's and A 's; when one is found in an event, the other is found in the same event with a probability that exceeds 50&o. PACS number(s): 13.65.+i, 13.87.Fh, 14.20 The baryons most accessible for study are the proton and lambda hyperon. Complicating the analysis of the production of these particles, however, is the fact that they arise as products of e+e annihilations both as a result of fragmentation processes and as a result of the decays of other baryonic states.In present fragmentation models baryons are produced via the creation of diquark pairs which then combine with a neighboring quark to produce the baryon. The Lund model parameter that governs the ratio of the baryonic to mesonic production rates is (qq/q), specifying how much more difficult it is to produce a diquark pair than a quark pair. In the inclusive production of A' s the strangeness quanta can come either from the quark or the diquark. To describe both the E and A inclusive production data, two additional parameters are required: A variant of this simple parametrization for producing baryons is the "popcorn model, " in which the remnant quarks left over after the quark pair and diquark pair produce a baryon contribute to the production of intermediate mesons and other baryons, rather than directly forming the counterpart antibaryon. This effect is illustrated in Fig. 1 [6 Their general overall agreement with available data is impressive and their A multiplicity prediction of 0.18 compares well with the value to be presented here.In this paper we utilize the large sample of A and A events to extract the 5 parameter and to examine the dominance of the simple Lund fragmentation mechanism through an analysis of the production rates of likestrangeness and opposite-strangeness A (A) pairs.The HRS consisted of an inner and outer driftchamber system which permitted charged-particle track positions to be determined to 200 pm over a radial distance of 1.89 m, and a barrel shower system which had an