Production of Λ and Λ correlations in the hadronic decays of the Z0

Abstract

An analysis of the production of the baryon in the hadronic decays of the Z 0 is presented, based on about 993K multihadronic events collected by the DELPHI detector at LEP during 1991 and 1992. The di erential cross section of the and the correlations between and produced in the same event are compared to current models, based both on string fragmentation and on cluster decay. The predictions of the string fragmentation model are found to give satisfactory agreements with the data, clearly better than those of the cluster model.

Hadronization in decay

“…Baryon number conservation implies that a baryon is always accompanied by an antibaryon; flavour conservation, via diquark pairs, suggests that the baryons may be preferentially particle-antiparticle pairs; and LPHD argues that these baryons occur close by in phase space. So far, studies have concentrated on measuring the proximity in phase space of p (p) [43,291], Λ (Λ) [194,209,292] and Λ (p) [162] baryon pairs. By introducing an event axis, typically the thrust or sphericity axis, correlations can be studied in rapidity, azimuthal angle or polar angle with respect to the axis.…”

Σ−-antihyperon correlations in Z0 decay and investigation of the baryon production mechanism

“…Intermediate mesons modify the rapidity difference between associated baryons and antibaryons. Rapidity correlations between pairs produced in Z 0 decays have been studied by several LEP collaborations and the conclusion was that best agreement between the experiments and the JETSET Monte Carlo model [10] was obtained with the popcorn effect included [12][13][14][15][16].…”

New Measurements of Hyperon Production from Charmonium States

“…For example, measurements of the energy spectra of inclusively produced hyperons from the LEP experiments using data taken at the Z 0 peak yielded information on such phenomena as how the production of hyperons with 2 s-quarks are suppressed relative to those containing 1 s-quark [8]. Another striking example is the difference in production rate between two hyperons with the same uds quark content, but different isospin, the I = 0 Λ 0 and the I = 1 Σ 0 [6]. This difference has been suggested to be important evidence in support of the existence of diquark correlations, and should therefore be searched for more widely.…”

“…There is a long history of studying hyperon production in e + e − colliders at Cornell (CLEO [1]), SLAC (TPC [2], HRS [3]), DESY (TASSO [4], CELLO [5]), and LEP (DEL-PHI [6], L3 [7], OPAL [8]). For example, measurements of the energy spectra of inclusively produced hyperons from the LEP experiments using data taken at the Z 0 peak yielded information on such phenomena as how the production of hyperons with 2 s-quarks are suppressed relative to those containing 1 s-quark [8].…”