S-Space College of Natural Sciences (자연과학대학) Dept. of Physics and Astronomy (물리·천문학부) Physics (물리학전공) Theses (Ph.D. / Sc.D._물리학전공)
Study of tau lepton decays involving K0S at Belle
- 자연과학대학 물리·천문학부(물리학전공)
- Issue Date
- 서울대학교 대학원
- 학위논문 (박사)-- 서울대학교 대학원 : 물리·천문학부(물리학전공), 2012. 8. 최선호.
- The τ lepton is the only known lepton massive enough to decay into hadrons via a weak vector current, and this provides a sensitive probe of the standard model parameters,
, αs and ms. However, because of the limited numbers of τ+τ− events, the hadronic decays involving kaons in τ lepton which is directly related to
determination has not been well studied for the decades.
The Belle experiment provides the best environments for studying τ leptons because of the high luminosity of e+e− collisions result in the production of large numbers of τ+τ− events. We report measurements of
branching fractions for inclusive/exclusive τ decays involving K0S → π−π+ with 669 fb−1 accumulated data at Belle detector at the asymmetric energy KEKB e+e− collider. The branching fraction measured for the inclusive decay is B(τ− → K0S X−ν ) = (0.910±0.001±0.046)%, where X− can be anything
for exclusive decays we report:
B(τ− → π−K0S ν ) =(4.10 ± 0.01 ± 0.21) × 10−3
B(τ− → K−K0S ν ) =(7.09 ± 0.06 ± 0.41) × 10−4
B(τ− → π−K0S π0ν ) =(1.95 ± 0.02 ± 0.11) × 10−3
B(τ− → K−K0S π0ν ) =(7.31 ± 0.12 ± 0.49) × 10−4
We also studied decays involving two K0S:
B(τ− → π−K0SK0Sν ) =(2.41 ± 0.04 ± 0.26) × 10−4
B(τ− → π−K0SK0Sπ0ν ) =(2.06 ± 0.23 ± 0.24) × 10−5
where B(τ− → π−K0SK0Sπ0ν ) is the first measurement. We also report the first observation of the channel τ− → f1(1285)-ν in π−K0SK0Sπ0 decay with its total branching fraction of (1.07±0.23±0.16)×10−5. With these results,
we expect the most precise value of
can be achieved.