Q.W. Wu

Study of π+π− transitions from the γ (3S) state

Abstract With the CUSB-II detector at CESR we have studied the processes γ (3S) → γ (1S) π + γ − and γ (3S) → γ (2S) π + π − , where the final state γ (1S or 2S) decays into a pair of leptons. We have found 451 γ (3S) → γ (1S) π + π − events and 138 γ (3S) → γ (2S) π + π − events. The corresponding branching ratios are (4.46 ± 0.34 ± 0.50)% and (4.82 ± 0.65 ± 0.53) % respectively, where the first error is statistical and the second systematic. The properties of the π + π − system have been studied and compared with several models.

CUSB-II: a high precision electromagnetic spectrometer

Abstract The design, construction and performance of a very compact precision electromagnetic spectrometer is described. The CUSB-II detector has been used to study ϒ spectroscopy, search for exotic particles and measure properties of the B and B ∗ mesons at the Cornell Electron Storage Ring.

Measurement of the B∗ cross section at s = 10.61 to 10.70 GeV☆

Abstract Using the CUSB-II detector at CESR we have measured the B ∗ cross section in the energy range from s = 10.61–10.65 GeV and 10.70 GeV to be 0.16±0.03 nb and 0.33±0.13 nb respectively. The photon energy for B ∗ →Bγ decays is measured to be 45.4±0.8 MeV, in agreement with our earlier determination. The implication of this measurement for future B factories is discussed.