Measurement of the bottom hadron lifetime at the Z sup 0 resonancce

Technical Report · Mon Jun 01 00:00:00 EDT 1992

DOI:https://doi.org/10.2172/7205993· OSTI ID:7205993

Fujino, D H

We have measured the bottom hadron lifetime from b{bar b} events produced at the Z{sup 0} resonance. Using the precision vertex detectors of the Mark II detector at the Stanford Linear Collider, we developed an impact parameter tag to identify bottom hadrons. The vertex tracking system resolved impact parameters to 30 {mu}m for high momentum tracks, and 70 {mu}m for tracks with a momentum of 1 GeV. We selected B hadrons with an efficiency of 40% and a sample purity of 80%, by requiring there be at least two tracks in a single jet that significantly miss the Z{sup 0} decay vertex. From a total of 208 hadronic Z{sup 0} events collected by the Mark II detector in 1990, we tagged 53 jets, of which 22 came from 11 double-tagged events. The jets opposite the tagged ones, referred as the untagged'' sample, are rich in B hadrons and unbiased in B decay times. The variable {Sigma}{delta} is the sum of impact parameters from tracks in the jet, and contains vital information on the B decay time. We measured the B lifetime from a one-parameter likelihood fit to the untagged {Sigma}{delta} distribution, obtaining {tau}{sub b} = 1.53{sub {minus}0.45}{sup +0.55}{plus minus}0.16 ps which agrees with the current world average. The first error is statistical and the second is systematic. The systematic error was dominated by uncertainties in the track resolution function. As a check, we also obtained consistent results using the {Sigma}{delta} distribution from the tagged jets and from the entire hadronic sample without any bottom enrichment.

• Research Organization: SLAC National Accelerator Lab., Menlo Park, CA (United States)
• Sponsoring Organization: USDOE; USDOE, Washington, DC (United States)
• DOE Contract Number: AC03-76SF00515
• OSTI ID: 7205993
• Report Number(s): SLAC-399; ON: DE92018235
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
BEAUTY PARTICLES
LIFETIME
Z NEUTRAL BOSONS
WEAK PARTICLE DECAY
EXPERIMENTAL DATA
MEASURING METHODS
MONTE CARLO METHOD
PARTICLE TRACKS
QUARKS
STANFORD LINEAR COLLIDER DETECTOR
BOSONS
DATA
DECAY
ELEMENTARY PARTICLES
FERMIONS
INFORMATION
INTERMEDIATE BOSONS
INTERMEDIATE VECTOR BOSONS
NUMERICAL DATA
PARTICLE DECAY
POSTULATED PARTICLES
662440* - Properties of Other Particles Including Hypothetical Particles- (1992-)
662380 - Decays of Intermediate Bosons- (1992-)