The Belle 2 experiment at the SuperKEKB accelerator records collisions between electrons with energy E₁ = 7 GeV and positrons with Ee+ = 4 GeV. The aim is to produce a large number of B-meson pairs through the Y(4S) resonance and study their decays. a) Calculate the center-of-mass energy and the momentum of the Y(4S) resonance in the laboratory. (You can neglect the mass of the electron/positron in the calculation.) b) The Belle2 experiment has an electromagnetic calorimeter based on scintillating Cesium- lodide (Csl) crystals with a depth of 30 cm (see appendix) and a Cerenkov detector which uses an aerogel with n = 1.045. Calculate the minimum number of crystal layers needed to contain the signal produced by a high-energetic electron or photon. Calculate the minimum energy of a + and a 7° needed to create a signal in the Cerenkov detector.

The Belle 2 experiment at the SuperKEKB accelerator records collisions between electrons with energy E₁ = 7 GeV and positrons with Ee+ = 4 GeV. The aim is to produce a large number of B-meson pairs through the Y(4S) resonance and study their decays. a) Calculate the center-of-mass energy and the momentum of the Y(4S) resonance in the laboratory. (You can neglect the mass of the electron/positron in the calculation.) b) The Belle2 experiment has an electromagnetic calorimeter based on scintillating Cesium- lodide (Csl) crystals with a depth of 30 cm (see appendix) and a Cerenkov detector which uses an aerogel with n = 1.045. Calculate the minimum number of crystal layers needed to contain the signal produced by a high-energetic electron or photon. Calculate the minimum energy of a + and a 7° needed to create a signal in the Cerenkov detector.