A study of the decays. tau. sup minus yields K* sup minus. nu. sub. tau. and. tau. sup minus yields. rho. sup minus. nu. sub. tau

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:5184221

Kanekal, S G

Measurements of branching fractions for decays {tau}{sup {minus}} {yields} K*{sup {minus}}{nu}{sub {tau}} and {tau}{sup {minus}} {yields} {rho}{sup {minus}}{nu}{sub {tau}} are presented. The measurements were done using the multi-purpose spectrometer ARGUS at the e{sup +}e{sup {minus}} storage ring DORIS. They are based on a data sample of 198 pb{sup {minus}1} collected at center of mass energies of about 10 GeV and represent the largest event samples to date. The measurements yield the following results: BR({tau}{sup {minus}} {yields} K*{sup {minus}}{nu}{sub {tau}}) = (1.23 {plus minus} 0.21{sub {minus}0.21}{sup +0.11})% BR({tau}{sup {minus}} {yields} {rho}{sup {minus}}{nu}{sub {tau}}) = (21.5 {plus minus} 0.4 {plus minus} 1.9)% The branching fraction for the decay {tau}{sup {minus}} {yields} {rho}{sup {minus}} {nu}{sub {tau}} is in good agreement with previous measurements and theoretical predictions based on CVC. This decay mode is particularly important in view of the present unresolved discrepancy between topological and exclusive branching ratios, as it is the largest exclusive mode. Theoretical predictions for the decay {tau}{sup {minus}} {yields} K*{sup {minus}}{nu}{sub {tau}}, are based on QCD sum rules. The measurements are in agreement with these predictions. Previous measurements, based on smaller event samples, show a large dispersion. Furthermore the ratio of the two branching ratios is found to be BR({tau}{sup {minus}} {yields} K*{sup {minus}}{nu}{sub {tau}})/BR({tau}{sup {minus}} {yields} {rho}{sup {minus}}{nu}{sub {tau}}) = 0.057 {plus minus} 0.010{sub {minus}0.010}{sup +0.006} which is in good agreement with the sum rule predictions. Alternatively if one assumes the validity of the QCD sum rules, one may extract tan {theta}{sub c} = 0.248 {plus minus} 0.031{sub {minus}0.031}{sup +0.018} as a measurement of the Cabibbo angle, a fundamental parameter in the standard model.

• Research Organization: Kansas Univ., Lawrence, KS (United States)
• OSTI ID: 5184221
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BOSONS
BRANCHING RATIO
CABIBBO ANGLE
DATA
DECAY
DORIS STORAGE RING
ELEMENTARY PARTICLES
ENERGY RANGE
EQUATIONS
EXPERIMENTAL DATA
FERMIONS
FIELD THEORIES
GEV RANGE
GEV RANGE 10-100
HADRONS
HEAVY LEPTONS
INFORMATION
LEPTONS
MASSLESS PARTICLES
MEASURING INSTRUMENTS
MESONS
NEUTRINOS
NUMERICAL DATA
PARTICLE DECAY
POSTULATED PARTICLES
QUANTUM CHROMODYNAMICS
QUANTUM FIELD THEORY
SEMILEPTONIC DECAY
SPECTROMETERS
STORAGE RINGS
SUM RULES
TAU NEUTRINOS
TAU PARTICLES
WEAK PARTICLE DECAY