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.
Cross sections for LAMBDA and SIGMA0 pair production in the mass region 2.23 to 3.5 GeV.
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.
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.
Using the CLEO detector at the Cornell $e~+e~-$ storage ring, CESR, we study the two-photon production of $\Lambda \overline{\Lambda}$, making the first observation of $\gamma \gamma \to \Lambda \overline{\Lambda}$. We present the cross-section for $ \gamma \gamma \to \Lambda \overline{\Lambda}$ as a function of the $\gamma \gamma$ center of mass energy and compare it to that predicted by the quark-diquark model.
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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.
Topological cross section for events in anti-tagged two photon processes.
Ratios of cross sections. Here 'p' includes the protons from the decay of any hadrons, except for lambdas. 'lambda' includes all decay products.
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.
Two-photon production of the exclusive final statesp\(\bar p\)+nπ (n=0, 1, 2, and 3) has been investigated using the ARGUS detector at thee+e− storage ring DORIS II at DESY. The reactionsγγ→p\(\bar p\)π andγγ→p\(\bar p\)π+π−π0 have been observed for the first time, as have theΔ++ and\(\overline {\Delta ^{ ++ } } \) baryons in the final statep\(\bar p\)π+π−. No evidence was found forΔ++\(\overline {\Delta ^{ ++ } } \) production. Topological cross sections for two-photon production ofp\(\bar p\),p\(\bar p\)π0,p\(\bar p\)π+π− andp\(\bar p\)π+π−π0, as well as the crosssection forγγ→Δ++\(\bar p\)π+π−+c.c., have been measured. Upper limits are given for the cross section forγγ→Δ0\(\overline {\Delta ^0 } \),γγ→Δ++\(\overline {\Delta ^{ ++ } } \) andγγ→Λ\(\bar \Lambda \).
Data read from graph.. Additional overall systematic error 13% not included.
Data read from graph.. Additional overall systematic error 13% not included.
Data read from graph.. Additional overall systematic error 13% not included.
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