SU(3) Breaking in Hyperon Beta Decays: a Prediction for Xi0 -> Sigma+ e anti-neutrino

SU(3) breaking in hyperon semi-leptonic decays is discussed. The SU(3) parameters $F$ and $D$, relevant to the ``proton-spin puzzle'', are extracted and a prediction is presented for the decay Xi0 -> Sigma+ e anti-neutrino, currently under study by the KTeV collaboration. The values found are g1/f1 = 1.16+/-0.03+/-0.01 and Gamma = (0.80+/-0.03+/-0.01) x 10^6 s^-1.Comment: Presented at the III Int. Conf. on Hyperons, Charm and Beauty Hadrons (Genova, June-July 1998). 3 pages, LaTeX2e, uses fleqn, espcrc2, acromake and axodraw packages (incl.

QCD and Transverse-Spin Physics

A pedagogical presentation of single-spin asymmetries and transversity is offered. Detailed discussion is given of various aspects of single-spin asymmetries in lepton-nucleon and in hadron-hadron scattering and of the role of perturbative QCD and evolution in the context of transversity.Comment: Talk at the International Workshop on QCD: QCD@Work 2003 - Conversano (Italy) 14-18 June 2003 (eConf C030614). LaTeX2e; 8 pages; uses standard LaTeX macros (including psfrag), conference class file wqcd03.cls, and some personal macros (included). Figures are eps and feynmp generated (included in subfolders

Transversity and Drell-Yan KK-Factors

The Drell-Yan $K$-factors for transversely polarised hadrons are examined. Since transverse spin is peculiar in having no DIS reference point, the effects of higher-order corrections on DY asymmetries are examined via a DIS definition for transversity devised using a hypothetical scalar vertex. The results suggest that some care may be required when interpreting experimentally extracted partonic transversity, particularly when comparing with model calculations or predictions.Comment: 4 pages, 2 figures (eps and feynmp); uses World Scientific class ws-procs9x6, standard LaTeX/MiKTeX packages [amsmath, feynmp, graphicx, natbib, psfrag] and one homespun package (included in the zip file); contributed talk to appear in proc. of the XVI Int. Symp. on High-Energy Spin Physics, Trieste (Oct. 2004

Hyperon Beta-Decay Analysis and the Recent KTeV Data

The analysis of hyperon semi-leptonic decay data is addressed with reference to SU(3) breaking and isospin mixing between Lambda^O and Sigma^O. Various approaches to SU(3) breaking are discussed and compared. The phenomenological implications of Lambda^0-Sigma^0 mixing are not to be underestimated: it can induce vector couplings in decays otherwise purely axial and may also modify rates. In regard of the KTeV data on Xi^0O -> Sigma^+ e antineutrino, predictions are presented and the impact of present a future data on the extraction of F and D is also examined. In addition, the implications of the new data for the use of octet baryon beta decays in determining V_us are considered.Comment: 5 pages, uses aipproc.cls, aipproc.sty (included), axodraw.sty, cite.sty. Presented at SPIN 2000 (Osaka, Oct. 2000

Semi-Inclusive DIS and Transversity

A review is presented of some aspects of semi-inclusive deeply inelastic scattering and transversity. In particular, the role of $k_T$-dependent and higher-twist (or multi-parton) distributions in generating single-spin asymmetries is discussed.Comment: 8 pages, uses aipproc.cls, feynmp, psfrag, and some personal packages (included); invited talk presented at HiX 2004, Marseille, 26-28 July 200

Single-Spin Asymmetries and Transversity

A pedagogical introduction to single-spin asymmetries (SSA's) and transversity is presented. Discussion in some detail is made of certain aspects of (SSA's) in lepton-nucleon and in hadron-hadron scattering and the role of pQCD and evolution in the context of transversity.Comment: 10 pages, 11 figures, presented at the XV International Symposium on High-Energy Spin Physics (Brookhaven, 9-14 Aug. 2002

Hyperon Beta Decay and the CKM Matrix

I shall present a pedagogical discussion of hyperon semileptonic decays, covering some of the historical background, the basics notions of hyperon semileptonic decays, deeply inelastic scattering and the CKM matrix, and the description of SU(2) and SU(3) breaking. I shall also present a prediction for a process under current experimental study.Comment: 10 Pages, LaTeX2e, 1 EPS figure + 2 FeynFM figures. Invited talk at the Advanced Studies Institute, Symmetries and SPIN (SPIN-Praha-2003), Prague, July 12-19, 2003. Uses cjpsuppl.cls class file and other included style file

Proton Spin, Sum Rules, QCD and Higher Twist

We examine the present status of the Bjorken sum rule in the light of recent data on the spin structure functions of the proton, neutron and deuteron obtained by the CERN and SLAC experimental groups. We also discuss the role of possible higher-twist contributions and higher-order PQCD corrections and comment on the extraction of the necessary parameters, D and F, obtained from hyperon semi-leptonic decays.Comment: 4 pages, latex, no figures, requires the QCDPARIS.STY style file. One minor correction to references mad