Observation of direct CP violation in $B^0 \to K^+ \pi^-$ decays

We present a measurement of the direct CP violating asymmetry in the decay B0 -> K+pi- using 227 x 10^6 Y(4S) -> BBbar decays collected with the BaBar detector at the PEP-II asymmetric-energy e+e- collider at SLAC, we observe a total signal yield of n(K-pi+) + n(K+pi-) = 1606 +- 51 decays and measure the asymmetry [n(K-pi+)-n(K+pi-)]/[n(K-p+-)+n(K+pi-)] = -0.133+-0.030 (stat) +- 0.009 (syst). The probability of observing such an asymmetry in the absence of direct CP violation is 1.3 x 10^-5, corresponding to 4.2 standard deviations.

Note:

PRL version Journal-ref: Phys.Rev.Lett. 93 (2004) 131801

12.15.Hh
11.30.Er
13.25.Hw
CP invariance
B mesons
meson hadronic decay
electron positron: colliding beams
electron positron: annihilation
Upsilon(10570): electroproduction
B0: pair production

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Observation of direct CP violation in B0→K+π−B^0 \to K^+ \pi^-B0→K+π− decays

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Observation of direct CP violation in $B^0 \to K^+ \pi^-$ decays