First Year of BABAR/PEP-II - Harvard University Laboratory for ...

Event Signature: B 0 → J/ψ K S
B 0
e - ϒ e +
4S
B 0
µ +
µ - J/ψ
∆z
K S
e +
π +
π -
A CP
() t
Γ( B 0 () t → f )–
Γ( B 0 () t → f )
= ------------------------------------------------------------------------
Γ( B 0 () t → f ) Γ B 0 = sin 2β
+ ( () t → f )
⋅
sin( ∆m
⋅ t)
Three steps to measure A CP (t):
◆ Reconstruct one B 0 (or anti-B 0 ) from J/ψ and K S .
◆ Measure time from ∆z = βγ∆t.
◆ Determine the flavor of the B 0 by tagging the other B 0 .
First Year of BaBar/PEP-II Masahiro Morii SLAC