10 research outputs found
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Experiments in a neutral hyperon beam
The authors propose a survey experiment for a neutral hyperon beam, to measure production of {Lambda}{sup 0}, {bar {Lambda}}{sup 0}, {Xi}{sup 0}, {bar {Xi}}{sup 0}, K{sub 1}{sup 0} - K{sub 2}{sup 0} near zero mrad. by 200 GeV protons on complex nuclei. The detector will be sensitive to polarization of the hyperons. The same apparatus will then be used to search for {Xi}{sup 0} {yields} p{pi}{sup -} and to measure {Lambda}{sup 0} and {bar {Lambda}}{sup 0} total and diffractive elastic cross sections in hydrogen
Lambda polarization and single-spin left-right asymmetry in diffractive hadron-hadron collisions
We discuss Lambda polarization and single-spin left-right asymmetry in
diffractive hadron-hadron scattering at high energies. We show that the
physical picture proposed in a recent Letter is consistent with the
experimental observation that polarization in the diffractive
process, , is much higher than that in the inclusive
reaction, . We make predictions for the left-right asymmetry,
A_N, and for the spin transfer, , in the single-spin process
and suggest further experimental tests of the
proposed picture.Comment: 14 pages, 3 ps-figures. Phys. Rev. D (in press
Transverse Lambda polarization in semi-inclusive DIS
Following a previous description of Lambda and Lambda-bar polarization in
unpolarized p-p interactions, within a perturbative QCD factorization scheme
with new polarizing fragmentation functions, here we investigate the transverse
polarization of Lambda's and Lambda-bar's produced in semi-inclusive DIS.
Analytical expressions for both neutral and charged current exchange are given.
Since quantitative predictions cannot be given at this stage and comparison
with existing data are not yet significant, we present the general formalism
and a qualitative analysis displaying generic features of the Lambda and
Lambda-bar polarization for specific scenarios. Different kinematical
situations are considered, corresponding to experiments currently able to study
Lambda production in semi-inclusive DIS.Comment: LaTeX, 28+1 pages, 9 ps figures, uses epsfig.sty; v2: largely revised
version, 22+1 pages, 3 ps figures; to be published in Phys. Rev.
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Results from hadron colliders
The present status of hadron collider physics is reviewed. The total cross section for {bar p} + p has been measured at 1.8 TeV: {sigma}{sub tot} = 72.1 {plus minus} 3.3 mb. New data confirm the UA2 observation of W/Z {yields} {bar q}q. Precision measurements of M{sub W} by UA2 and CDF give an average value M{sub W} = 80.13 {plus minus} 0.30 GeV/c{sup 2}. When combined with measurements of M{sub Z} from LEP and SLC this number gives sin{sup 2}{theta}{sub W} = 0.227 {plus minus} 0.006, or m{sub top} = 130{sub {minus}60}{sup +40} GeV/c{sup 2} from the EWK radiative correction term {Delta}r. Evidence for hadron colliders as practical sources of b quarks has been strengthened, while searches for t quarks have pushed the mass above M{sub W}: m{sub top} > 89 GeV/c{sup 2} 95% cl (CDF Preliminary). Searches beyond the standard model based on the missing E{sub T} signature have not yet produced any positive results. Future prospects for the discovery of the top quark in the range m{sub top} < 200 GeV/c{sup 2} look promising. 80 refs., 35 figs., 7 tabs
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Measurement of the sigma^o Lifetime
The Coulomb production of {Sigma}{sup 0} hyperons on uranium and nickel nuclei has been measured in a beam of {Lambda} hyperons at the CERN Proton Synchrotron. The results for the {Sigma}{sup 0} lifetime, {tau}{Sigma}{sup 0} = (0.58 {+-} 0.13) x 10{sup -19} sec, and for the {Sigma}{sup 0}-{Lambda} magnetic transition moment, |{mu}{Sigma}{sub {Lambda}}| = (1.82{sub -0.18}{sup +0.25}) nuclear magnetons, are in agreement with SU(3) predictions