Albrecht, H.
GAMMA GAMMA --> LAMBDA LAMBDABAR
Two-Photon
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Lambda and Sigma0 pair production in two photon collisions at LEP

The L3 collaboration Achard, P. ; Adriani, O. ; Aguilar-Benitez, M. ; et al.
Phys.Lett.B 536 (2002) 24-33, 2002.
Inspire Record 585621 DOI 10.17182/hepdata.48892

Strange baryon pair production in two-photon collisions is studied with the L3 detector at LEP. The analysis is based on data collected at e+e- centre-of-mass energies from 91 GeV to 208 GeV, corresponding to an integrated luminosity of 844 pb-1. The processes gamma gamma -> Lambda Anti-lambda and gamma gamma -> Sigma0 Anti-sigma0 are identified. Their cross sections as a function of the gamma gamma centre-of-mass energy are measured and results are compared to predictions of the quark-diquark model.

3 data tables
Table 1

Cross sections for LAMBDA and SIGMA0 pair production in the mass region 2.23 to 3.5 GeV.

Table 2

Cross sections for LAMBDA pair production as a function of the 2 photon invariant mass W. The average W of each bin is assumes a W**(-8) distribution.

Table 3

Cross sections for SIGMA0 pair production as a function of the 2 photon invariant mass W. The average W of each bin is assumes a W**(-8) distribution.


Study of inclusive baryon - anti-baryon pair production of P or Lambda in two photon processes

The VENUS collaboration Uehara, S. ; Abe, K. ; Amako, K. ; et al.
Z.Phys.C 69 (1996) 597-606, 1996.
Inspire Record 400152 DOI 10.17182/hepdata.38341

Inclusive baryon-antibaryon pair production was studied in two-photon events which were collected at the e+e− collider TRISTAN, and correspond to an integrated luminosity of 303 pbt?1. Correlations between a baryon and an antibaryon were studied for their flavors (p or Λ) and their momentum vectors. The experimental results were compared with the expectations from a jet-fragmentation Monte Carlo simulation. We have found that although the ratios of the cross sections of different baryon-flavor combinations are consistent with the Monte Carlo expectations, the cross section shows an excess over the Monte Carlo expectation in a low invariant-mass region of final-state particles at large angles, that indicates a significant contribution from higher-order QCD or non-perturbative effects. The experimental data show no narrow azimuthal-angle correlation, which is expected from a jet-fragmentation Monte Carlo. A search for exclusive Λ pair production has also been made. We have no candidates and have obtained the upper limit for the cross section.

4 data tables
Table 1

Topological cross section for events in anti-tagged two photon processes.

Table 2

Ratios of cross sections. Here 'p' includes the protons from the decay of any hadrons, except for lambdas. 'lambda' includes all decay products.

Table 3

Upper limits (95% CL) assuming shape of the W dependence is W**(-12)(BETA*(LAMBDA)) where BETA*(LAMBDA) is the velocity of the LAMBDA in the c.m. frame of the gamma-gamma.

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