A proposed future electron-positron collider would run for one year sitting exactly…
PHYSICS · Multi-part · Fermi University Physics · Particle Physics & Quantum Fields · Particles, interactions and experiment · Flavour, neutrinos and CP violation
Symmetry and Flavour, Ch Heavy flavour: charm and beauty decays and the magnitudes of the CKM elements
Problem
A proposed future electron-positron collider would run for one year sitting exactly on the Z resonance, so that Z bosons are produced and decay as e+e−→Z→bbˉ, each event giving one beauty hadron and one anti-beauty hadron, a bbˉ pair. Near the peak the cross section for this process is σ=6.3nb, and the design integrated luminosity for the year is L=150ab−1. Treat σ as constant over the run, take the full design luminosity as delivered, and ignore any background or loss of pairs.
((a)) Estimate the number of bbˉ pairs produced in the one-year run.
((b)) A study of a particular rare decay chain needs at least 105 tagged bbˉ pairs of a certain type to reach the required precision. Such pairs occur, and are successfully tagged, with overall probability 5×10−8 per bbˉ pair produced (this already includes the relevant branching fraction and the detector's tagging efficiency). Estimate how many years of running at the design luminosity are needed to collect 105 tagged pairs.
((c)) Belle and BaBar together recorded about 1.2×109BBˉ pairs at the Υ(4S) over their combined lifetimes. Express the one-year yield of part (a) as a multiple of this figure.