BABAR Notes

The Asymmetric B-Factory at the Stanford Linear Accelerator Center will study the BB meson system with focus on CP violation. Its detector BABAR contains a high-resolution CsI(Tl) calorimeter, which is currently under construction. The final design of the calorimeter (from the crystals to the calibration system) will be presented in this report.

The actual positions of the BABAR barrel crystals were calculated from measurements taken during module assembly and module alignment. The numbers and calculations are described in this note.

For the radiative Bhabha calibration of BABAR’s electromagnetic calorimeter, the measures energy of a photon cluster is being compared with the energy obtained via kinematic fit involving other quantities from that event. The details of the fitting algorithm are described in this note, together with its derivation and checks that ensure that the fitting routine is working properly.

During the quality control process, the CsI(Tl) crystals of the barrel calorimeter were measured with a photo multiplier tube (PMT) in one of three different light yield scanners. After gluing the photo diodes (PD) on the crystals, the light yield was again measured in another setup suitable for the photo diodes. In this note, the measurements via PMT and via PD are compared, time dependencies identified, the overall error of the measurement discussed, and history of the measurements recorded.

The observation of the Υ(5S) resonance is an important step to evaluate the feasibility of using measurements of B_s⁰ decays to test the theoretical models of B_s⁰ meson decays. We discuss a measurement of absolute branching fraction B_s⁰→D_s^*+ ℓ^-ν_ℓ at the Υ(5S) using a double-tag technique. We partially reconstructed the decays B_s⁰→D_s^*+ ℓ^-ν_ℓ, where we only use the information from the charged lepton combined with the soft photon from the decay D_s^*+→D_s⁺γ.