[SEMINARI]: Observation of CP Violation in the B0 meson system

[Fernando Martinez]

Dear Colleagues and Friends,

It is a pleasure to announce you that on thursday 5th July, the BaBar
Collaboration has submitted to Physical Review Letters the paper

"Observation of CP Violation in the B0 meson system".

The paper will be available as preprint on sunday night (hep-ex/0107013),
but you can already find it from the BaBar Web page

http://www.slac.stanford.edu/BF

and also from

http://www.slac.stanford.edu/~martinef/cpObservation/paper2.ps

This paper is based on our previous PRL publication on February, PRL 86 (2001),

http://www.slac.stanford.edu/~martinef/cpObservation/paper1.ps

The result,

sin2beta = 0.59+/-0.14(stat)+/-0.05(syst)

establishes CP violation in the B0 meson system at 4.1 sigma level.
The probability to obtain this value or higher in the absence of CP
violation is less than 3x10^-5. We have also measured any possible
direct CP contribution,

|lambda|=0.93+/-0.09(stat)+/-0.03(syst)

compatible with no CP violation in the decay.

For your delight, here are few plots to ilustrate the unambiguous
observation. In,

http://www.slac.stanford.edu/~martinef/cpObservation/rawAsymmetry.eps

you can see the raw asymmetries for CP=-1 and CP=+1 final states, together with
the time distributions for B0 and B0bar tags. Overlaid curves are the
result of the unbinned maximum likelihood fit. In addition,

http://www.slac.stanford.edu/~martinef/cpObservation/unfoldedAsymmetry.eps

shows on top the stability of the sin2beta result when the analysis is
performed in bins of deltaT, and in the bottom it is shown the completely
unfolded asymmetry.

The result obtained for each decay mode is shown here:

http://www.slac.stanford.edu/~martinef/cpObservation/comparison.eps

Finally, in

http://www.slac.stanford.edu/~martinef/cpObservation/triangle.eps

you can find the constraints on the Unitarity Triangle, compared to
the range of values implied by other measurements and theoretical
estimates of the magnitudes of CKM matrix elements.

The CP era just started.

Best wishes,

Fernando Martinez-Vidal
for the BaBar Collaboration.