Spin asymmetry of kaon productions in polarized deep-inelastic scattering on deuterium target by HERMES experiment

The measurement of the spin asymmetry of kaon productions in deep-inelastic electron scattering on the polarized deuterium target at the HERMES experiment is reported in this thesis. The HERMES experiment is performed at DESY in Hamburg, Germany. It studies the spin structure of the nucleon. The HERMES experiment uses a longitudinally polarized target and the longitudinally polarized 27.5 GeV electron beam of the HERA storage ring. HERMES measures the electrons scattered off the target nucleon and identifies the hadrons in the final state in coincidence. HERMES has installed a Ring Imaging Cerenkov (RICH) detector with a dual-radiator, aerogel and C_4F_1_0 gas, just before the data taking period in 1998. Silica aerogel was used for the first time as a radiator of the RICH detector in the actual experiment. The RICH detector identifies kaons as well as pions and protons in a wide momentum range from 2 GeV to 15 GeV. The kaon is an important particle to study the contributions of the sea and strange quark spin to the nucleon spin as it has a strange quark as its constituent. The spin asymmetry of kaon productions was measured in the kinematic range 0.023<x<0.6 and 1 GeV"2<Q"2<10 GeV"2 using the polarized deuterium target data taken from 1998 to spring 1999. The result is shown as a function of x, the Bjorken's scaling variable. The spin asymmetry of kaon productions was measured for the first time in polarized deep-inelastic scattering. A clear difference between the asymmetries of K"+ (us) production and K"- (us) production was observed. K"- asymmetry provides the first direct experimental indication that the contribution of the sea quark spin to the nucleon spin is small. This result opened up a new technique of the polarized deep-inelastic scattering: #pi#, K, p (p) identification and studies of quark flavor which contributes to the nucleon spin. (orig.)Available from TIB Hannover: RA 8919(2001-017) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman