Journal
JOURNAL OF HIGH ENERGY PHYSICS
Volume -, Issue 11, Pages -Publisher
SPRINGER
DOI: 10.1007/JHEP11(2018)014
Keywords
Heavy Quark Physics; Perturbative QCD
Categories
Funding
- Ministry of Science and Technology of R.O.C. [106-2112-M-001-015]
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The lifetimes of bottom and charmed hadrons are analyzed within the framework of the heavy quark expansion (HQE). Lifetime differences arise from the spectator effects such as weak W-annihilation and Pauli interference. Spectator effects originating from dimension-7 four-quark operators are derived. Hadronic matrix elements of fourquark operators are parameterized in a model-independent way. Using the dimension-6 bag parameters recently determined from HQET sum rules and the vacuum insertion approximation for meson matrix elements of dimension-7 operators, the calculated B meson lifetime ratios t (B +)/t (B 0 d) = 1.074 +0. 017 -0. 016 and t (B 0 s)/t (B 0 d) = 0.9962 +/- 0.0024 are in excellent agreement with experiment. Likewise, based on the quark model evaluation of baryon matrix elements, the resulting baryon lifetime ratios t (tau-b)/t (tau 0 b), t (tau -b)/t (tau 0 b), t (tau -b)/t (tau -b) and the tau b -B 0 lifetime ratio t (tau 0 b)/t (B 0 d) = 0.953 also agree well with the data. Contrary to the bottom hadron sector where the HQE in 1/mb works well, the HQE to 1/m 3 c fails to give a satisfactory description of the lifetimes of both charmed mesons and charmed baryons. This calls for the subleading 1/mQ corrections to spectator effects. The relevant dimension-7 spectator effects are in the right direction for explaining the large lifetime ratio of t (tau+ c)/t (tau+ c). However, the destructive 1/mc corrections to (tau 0 c) are too large to justify the validity of the HQE, namely, the predicted Pauli interference and semileptonic rates for tau 0 c become negative. Demanding these rates to be positive for a sensible HQE, we find the lifetime pattern t (tau+ c) > t (tau 0 c) > t (tau+ c) > t (tau 0 c), contrary to the current hierarchy t (tau+ c) > t (tau+ c) > t (tau 0 c) > t (tau 0 c). We conclude that the tau 0 c, which is naively expected to be shortest-lived in the charmed baryon system owing to the large constructive Pauli interference, could live longer than the tau+ c due to the suppression from 1/mc corrections arising from dimension-7 four-quark operators. The new charmed baryon lifetime pattern needs to be tested in forthcoming experiments.
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