Question 1 :
Show that if a B0 B0-bar pair is produced in e+e- annihilation
in association with other particles far above the B B-bar
threshold, and both B's decay semileptonically,
the like to unlike sign ratio is
but if the pair is produced by the Upsilon (4S), the
ratio is simply r.
Question 2 :
Compare the results from the ARGUS Collaboration for r_d,
viewed as a measurement of x_d = delta m_d / Gamma_d
with those obtained from a direct measurement of
delta m_d using B's produced at higher energies, combined
with measurements of the B0 lifetime.
Consult the Review of Particle Properties (PDG), either
in its published form or on-line.
(delta m_d is the mass splitting of the two eigenmasses
of the B0 - B0-bar system, and Gamma_d is the average total-width
of the two.)