If you have questions or more information, please contact Doug.Wright@llnl.gov.
<hr>
<p>Both the BaBar and BELLE collaborations have published their first
results on the measurement of CP violation in B mesons. The BaBar
result is based on 23 million B Bbar pairs (twice the amount of data
than BELLE's).

<br>
<br>Phys. Rev. Lett. 86, March 19, 2001:
<ul>
<li>BaBar <a href=babar_prl1.pdf>(pdf)<a href=babar_prl1.ps>(ps)</a>
<li>Belle <a href=belle_prl1.pdf>(pdf)<a href=belle_prl1.ps>(ps)</a>
</ul>

<p>In the Standard Model, CP violation in B mesons is parameterized by
the quantity sin2beta. The measurements are:
<br>
<br>  sin2beta = 0.34 +- .20 +- .05 (BaBar)
<br>  sin2beta = 0.58 +- .33 +- .10 (BELLE)
<br>
<br>No CP violation would imply sin2beta = 0. To accommodate the
CP-violating signal in neutral kaons (first observed in 1964),
sin2beta should be in the range (0.4-0.8). The astute reader will
notice that these measurements are consistent both with zero and
with the Standard Model.

<p>So the new world average for CP violation in B mesons is:
<br>
<br>sin2beta = 0.49 +- 0.16   (BaBar + BELLE + CDF + OPAL)
<br>sin2beta = 0.41 +- 0.18   (B Factories only: BaBar + BELLE)
<br>
<p>In July 2000, both BaBar and BELLE reported results on sin2beta at the
Osaka conference on High Energy Physics. At that time BELLE had
accumulated 7 fb^-1 and BaBar 10 fb^-1. Neither experiment published
those results.