A measurement of the Z[sup 0] hadronic branching fraction to bottom quarks and the charged multiplicity of bottom quark events using precision vertex detectors at E[sub CM] = 91 GeV

Miscellaneous · Wed Jan 01 00:00:00 EST 1992

OSTI ID:7206796

Koetke, D S

Using the precision vertex detectors of the Mark II at the SLC, an impact parameter tag was developed to select a sample of hadronic Z[sup 0] 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 an enriched sample purity of 85% was achieved. This impact parameter tag was used to measure the fraction hadronic Z[sup 0] decays which produce b[bar b] events, F[sub b]. It is found that F[sub b] = 0.232[sub [minus]0.045][sup +0.053](stat) [sub [minus]0.021][sup +0.025](syst). This result is consistent with those found using other tagging methods as well as the Standard Model prediction of 0.217. The b[bar 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[sup 0] decays, [delta][bar n][sub 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 in [bar n][sub 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][sub 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. This also yields a determination of the average energy fraction of bottom hadrons in Z[sup 0] decays of [l angle]x[sub E][r angle][sub b] = 0.619[sub [minus].107[sup +.096]] (stat) [sub [minus].045[sup +.043]] (syst).

• Research Organization: Stanford Univ., CA (United States)
• OSTI ID: 7206796
• 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
BRANCHING RATIO
HADRONIC PARTICLE DECAY
BEAUTY PARTICLES
ELECTRON-POSITRON INTERACTIONS
BOSONS
DECAY
ELEMENTARY PARTICLES
INTERACTIONS
INTERMEDIATE BOSONS
INTERMEDIATE VECTOR BOSONS
LEPTON-LEPTON INTERACTIONS
PARTICLE DECAY
PARTICLE INTERACTIONS
662380* - Decays of Intermediate Bosons- (1992-)