Branching fractions for D0→K+K− and D0→π+π−, and a search for CP violation in D0 decays

Abstract Using the large hadroproduced charm sample collected in experiment E791 at Fermilab, we have measured ratios of branching fractions for the two-body singly-Cabibbo-suppressed charged decays of the D0: Γ(D 0 →K + K − ) Γ(D 0 →K − π + ) =0.109±0.003±0.003 , Γ(D 0 →π + π − ) Γ(D 0 →K − π + ) =0.040±0.002±0.003 , and Γ(D 0 →K + K − ) Γ(D 0 →π + π − ) =2.75±0.15±0.16 . We have looked for differences in the decay rates of D0 and D 0 to the CP eigenstates K+K− and π+π−, and have measured the CP asymmetry parameters ACP(K+K−)=−0.010±0.049±0.012 and ACP(π+π−)=−0.049±0.078±0.030, both consistent with zero.