ar X iv : 0 70 5 . 03 42 v 1 [ he p - ex ] 2 M ay 2 00 7 Υ ( 5 S ) : What has been learned and what can be learned
نویسنده
چکیده
The Υ(5S) was discovered about 20 years ago in ee collisions at CLEO [1] and CUSB [2]. Its mass is (10865 ± 8) MeV, about 300 MeV higher than the Υ(4S) resonance, and its width of (110± 13) MeV is about five times larger than the Υ(4S) resonance. Its production cross-section was measured to be about 0.3 nb, about ten times lower than the Υ(4S) cross-section. Owing to its mass, the Υ(5S) can decay to a variety of final states containing B and B s mesons. The accessible B-meson final states include: BB̄, BB̄, BB̄, BB̄π, BB̄π, BB̄π and BB̄ππ; final states with B s are: B 0 s B̄ 0 s , B 0∗ s B̄ 0 s , and B s B̄ 0∗ s . Further study of the Υ(5S) is of great interest because of it being a potentially large source of B s mesons at an e e machine. If suitably large samples can be collected, their study would provide a complementary probe of CP violation and rare decays to LHCb. Studies involving rare decays, particularly those with soft photons, and untagged time-dependent and timeindependent measurements, which provide access to the width difference between the B s mass eigenstates, ∆Γs, offer complementary information to measurements at hadron machines [3]. Because of the small Lorentz boost at the Υ(5S) and the large value of the mixing frequency, ∆ms [4], time-dependent CP violation measurements in mixing are not possible. Until recently, there existed only weak limits on the production rate of B s at the Υ(5S). Several models attempt to describe the hadronic cross-
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ar X iv : 0 71 2 . 42 46 v 1 [ he p - ph ] 2 7 D ec 2 00 7 Υ ( 1 s ) → γ ( η ′ , η ) Decays Bing
The decays of Υ(1s) → γ(η, η) are studied by an approach which has successfully predicted the ratio Γ(J/ψ→γη ) Γ(J/ψ→γη) . Strong dependence on quark mass has been found in the decays (J/ψ,Υ(1s)) → γ(η, η). Very small decay rates of Υ(1s) → γ(η, η) are
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