Measurement of the bottom hadron lifetime at the Z⁰ resonancce

Thesis/Dissertation · Mon Jun 01 00:00:00 EDT 1992

DOI:https://doi.org/10.2172/10165405· OSTI ID:10165405

Fujino, Donald Hideo ^[1]

---

1. Stanford Univ., CA (United States)

We have measured the bottom hadron lifetime from b$$\bar{b}$$ events produced at the Z⁰ 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 μm for high momentum tracks, and 70 μm 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 Z⁰ decay vertex. From a total of 208 hadronic Z⁰ 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 Σδ 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 Σδ distribution, obtaining τ_b = 1.53 $$+0.55\atop{-0.45}$$ ± 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 Σδ 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
• DOE Contract Number: AC03-76SF00515
• OSTI ID: 10165405
• Report Number(s): SLAC-399; ON: DE92018235
• Resource Relation: Other Information: TH: Thesis (Ph.D.); PBD: Jun 1992
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
Z NEUTRAL BOSONS
WEAK PARTICLE DECAY
BEAUTY PARTICLES
LIFETIME
QUARKS
STANFORD LINEAR COLLIDER DETECTOR
EXPERIMENTAL DATA
PARTICLE TRACKS
MONTE CARLO METHOD
MEASURING METHODS
662440
662380
PROPERTIES OF OTHER PARTICLES INCLUDING HYPOTHETICAL PARTICLES
DECAYS OF INTERMEDIATE BOSONS