Production polarization and magnetic moment of anti-cascade minus hyperon produced by 800 GeV/c protons

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 1990

OSTI ID:7206044

Ho, Pakming

In 1976 it was shown that {Lambda} hyperons are substantially polarized when produced in the reaction p + Be {yields} {Lambda} + X, where X represents unobserved particles. It was a surprising discovery since polarization effects were believed to be washed out at high energy and small transverse momentum. It indicated that important spin effects exist in high energy collisions. Later on, polarization of comparable magnitude was also found in inclusive production of {Sigma}{sup 0}, {Sigma}{sup +}, {Sigma}{sup {minus}}, {Xi}{sup 0}, and {Xi}{sup {minus}} hyperons by protons. On the contrary, the polarization of {bar {Lambda}} was found to be consistent with zero. The polarization of {bar {Xi}}{sup 0} was inconclusive. Models based on the recombination of valence quarks in the projectile with quarks from the sea to form the hyperon can explain the qualitative behavior of the data. These models also predict no polarization for particles that do not share any valence quarks with the incoming particle, for example, anti-hyperons such as {bar {Xi}}{sup +}. In the experiment E756 at Fermilab, they have discovered that {bar {Xi}}{sup +}'s produced by 800 GeV/c protons were polarized with an average polarization of P{sub {bar {Xi}}}+ = {minus}0.097 {plus minus} 0.012 {plus minus} 0.009 at {l angle}x{sub F}{r angle} = 0.39, {l angle}p{sub t}{r angle} = 0.76 GeV/c. For comparison, the {Xi}{sup {minus}} polarization was measured to be P{sub {Xi}}{minus} = {minus}0.102 {plus minus} 0.012 {plus minus} 0.010 at {l angle}x{sub F}{r angle} = 0.41, {l angle}p{sub t}{r angle} = 0.78 GeV/c. The near equality of the {bar {Xi}}{sup +} and {Xi}{sup {minus}} polarizations calls into question models of hyperon polarization which predict zero polarization for all anti-hyperons.

• Research Organization: Michigan Univ., Ann Arbor, MI (United States)
• OSTI ID: 7206044
• Country of Publication: United States
• Language: English

Related Subjects

662340* -- Hadron Interactions-- (1992-)
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ALKALINE EARTH METALS
BARYON REACTIONS
BARYONS
BERYLLIUM
CHARGED-PARTICLE REACTIONS
DISTRIBUTION
ELEMENTARY PARTICLES
ELEMENTS
ENERGY RANGE
FERMIONS
GEV RANGE
GEV RANGE 100-1000
HADRON REACTIONS
HADRON-HADRON INTERACTIONS
HADRONS
HYPERONS
INCLUSIVE INTERACTIONS
INTERACTIONS
MAGNETIC MOMENTS
METALS
NUCLEAR REACTIONS
NUCLEON REACTIONS
PARTICLE INTERACTIONS
PARTICLE PRODUCTION
POLARIZATION
POSTULATED PARTICLES
PROTON REACTIONS
QUARKS
STRANGE PARTICLES