HEPData Search

The polarization of Λ baryons from Z decays is studied with the Aleph apparatus. Evidence of longitudinal polarization of s quarks from Z decay is observed for the first time. The measured longitudinal Λ polarization is P L Λ = −0.32 ± 0.07 for z = p p beam > 0.3 . This agrees with the prediction of −0.39 ± 0.08 from the standard model and the constituent quark model, where the error is due to uncertainties in the mechanism for Λ production. The observed Λ polarization is diluted with respect to the primary s quark polarization by Λ baryons without a primary s quark. Measurements of the Λ forward-backward asymmetry and of the correlation between back-to-back Λ Λ pairs are used to check this dilution. In addition the transverse Λ polarization is measured. An indication of transverse polarization, more than two standard deviations away from zero, is found along the normal to the plane defined by the thrust axis and the Λ direction.

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CM Energies (GeV)

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ASYMMETRY OF THE CROSS-SECTION FOR THE REACTION GAMMA D ---> P N INDUCED BY LINEARLY POLARIZED GAMMA RAYS IN THE ENERGY REGION E (GAMMA) = 0.4-GEV - 0.8-GEV AND THETA (P) center-of-mass = 45-degrees 95-DEGREES

MEASUREMENT OF POLARIZATION IN THE pi- p ---> pi0, n, pi0 ---> 2 gamma REACTION AT 40-GeV/c WITH THE REGISTRATION OF ALL REACTION PRODUCTS

CROSS-SECTION ASYMMETRY OF THE gamma n ---> pi- p REACTION BY POLARIZED PHOTONS IN THE THIRD AND FOURTH RESONANCE REGIONS

THE OBSERVATION OF THE ASYMMETRY IN THE REACTION pi- polarized p ---> pi0 X AT THE ANGLE 90-degrees IN cms AT 40-GeV/c

OBSERVATION OF THE ASYMMETRY IN THE REACTION pi- polarized p ---> omega n AT 40-GeV/c

MEASUREMENT OF ASYMMETRY IN THE REACTION pi- polarized p ---> K0 LAMBDA AT 40-GeV/c

Polarization of Charmed $\Lambda(c$)+ Baryons Produced in Neutron - Carbon Interactions

POLARIZATION ASYMMETRY OSCILLATIONS IN REACTION pi- p ---> p0 n AT t <= 3-GeV/c**2

SPIN EFFECTS IN CUMULATIVE PRODUCTION OF PROTONS AND DEUTERONS IN PROTON - NUCLEUS INTERACTIONS AT 16-GeV TO 64-GeV

rivet Analysis
Measurement of Lambda polarization from Z decays