2 research outputs found
Observation of CP violation in the B0 meson system
We present an updated measurement of time-dependent CP-violating asymmetries
in neutral B decays with the BABAR detector at the PEP-II asymmetric B Factory
at SLAC. This result uses an additional sample of Upsilon(4S) decays collected
in 2001, bringing the data available to 32 million B-anti-B pairs. We select
events in which one neutral B meson is fully reconstructed in a final state
containing charmonium and the flavor of the other neutral B meson is determined
from its decay products. The amplitude of the CP-violating asymmetry, which in
the Standard Model is proportional to sin2beta, is derived from the decay time
distributions in such events. The result sin2beta = 0.59 +/- 0.14 (stat) +/-
0.05 (syst) establishes CP violation in the B^0 meson system. We also determine
|lambda| = 0.93 +/- 0.09 {stat} +/- 0.03 {syst}, consistent with no direct CP
violation.Comment: 8 pages, 2 figures, submitted to Physical Review Letter
Measurement of the CP violating asymmetry amplitude sin 2beta
We present results on time-dependent CP-violating asymmetries in neutral B
decays to several CP eigenstates. The measurements use a data sample of about
88 million Y(4S) --> B Bbar decays collected between 1999 and 2002 with the
BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We study
events in which one neutral B meson is fully reconstructed in a final state
containing a charmonium meson and the other B meson is determined to be either
a B0 or B0bar from its decay products. The amplitude of the CP-violating
asymmetry, which in the Standard Model is proportional to sin2beta, is derived
from the decay-time distributions in such events. We measure sin2beta = 0.741
+/- 0.067 (stat) +/- 0.034 (syst) and |lambda| = 0.948 +/- 0.051 (stat) +/-
0.030 (syst). The magnitude of lambda is consistent with unity, in agreement
with the Standard Model expectation of no direct CP violation in these modes.Comment: 7 pages, 2 postscript figures, submitted to PR