A measurement of the Z⁰ hadronic branching fraction to bottom quarks and the charged multiplicity of bottom quark events using precision vertex detectors at E_cm = 91 GeV [Thesis]

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

DOI:https://doi.org/10.2172/7206010· OSTI ID:7206010

Koetke, Dale Steven ^[1]

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1. Stanford Univ., CA (United States)

Using the precision vertex detectors of the Mark 2 at the SLC, an impact parameter tag was developed to select a sample of hadronic Z° decays enriched in its fraction of bottom quark events. The nominal tagging method requires that there be at least three tracks whose impact parameters are inconsistent with the track having originated at the electron-position interaction point. A tagging efficiency for b$$\bar{b}$$ events of 50% with a enriched sample purity of 85% was achieved. This impact parameter tag was used to measure the fraction hadronic Z° decays which produce b$$\bar{b}$$ events, F_b. It is found that F_b = 0.232$$+0.053\atop{-0.045}$$ (stat) $$+0.025\atop{-0.021}$$ (syst). This result is consistent with those found using other tagging methods as well as the Standard Model prediction of 0.217. The b_b-enriched event sample was also used to measure the difference between the average charged multiplicity of b$$\bar{b}$$ events and that of all hadronic Z° decays, δ$$\bar{n}$$_b = 2.11 ± 1.82(stat) ± 0.57(syst). Using previous measurements of the total hadronic charged multiplicity, the corresponding total multiplicity for b$$\bar{b}$$ events is $$\bar{n}$$_b=23.05 ± 1.82 (stat) ± 0.60 (syst). Subtracting the contribution to the multiplicity from B hadron decays yields the multiplicity of the b$$\bar{b}$$ non-leading system, $$\bar{n}$$$$\bar{nl}$$ = 12.04 ± 1.82 (stat) ± 0.63(syst). Comparing this non-leading multiplicity to the total hadronic multiplicity data at lower energy supports the hypothesis that the non-leading particle production is independent of the flavor of the initial quarks.

• Research Organization: SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC03-76SF00515
• OSTI ID: 7206010
• Report Number(s): SLAC-396; SLAC-R-396; ON: DE92018236
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
Z NEUTRAL BOSONS
HADRONIC PARTICLE DECAY
BEAUTY PARTICLES
BRANCHING RATIO
EXPERIMENTAL DATA
MONTE CARLO METHOD
MULTIPLICITY
PERFORMANCE
QUARKS
STANDARD MODEL
STANFORD LINEAR COLLIDER DETECTOR
BOSONS
DATA
DECAY
ELEMENTARY PARTICLES
FERMIONS
INFORMATION
INTERMEDIATE BOSONS
INTERMEDIATE VECTOR BOSONS
MATHEMATICAL MODELS
NUMERICAL DATA
PARTICLE DECAY
PARTICLE MODELS
POSTULATED PARTICLES
UNIFIED GAUGE MODELS
662380* - Decays of Intermediate Bosons- (1992-)