@article{641be3337c5c46a5b8333a32fd10ea31,

title = "sin2β from K→πν ν{\= }",

abstract = "We point out the measurement of just the two branching fractions B(K+→π+ν ν{\= }) and B(KL→π0ν ν{\= }) can in a theoretically clean manner determine sin2β almost independently of mt and Vcb. This allows to obtain an interesting relation between the CP asymmetry ACP(ψKS) in B physics and the branching ratios for these two rare K decays. The recently calculated next-to-leading order QCD corrections improve the accuracy of this analysis. We find typically Δsin2β=±0.11 provided B(K+→π+ν ν{\= }) and B(KL→π0ν ν{\= }) are measured within ±10% accuracy. With decreasing uncertainty in ΛMS and mc this error could be reduced to Δsin2β<±0.10. The determination of sin2α and sin2γ on the other hand is rather poor. However respectable determinations of the Wolfenstein parameter η and of |Vtd| can be obtained.",

author = "Gerhard Buchalla and Buras, {Andrzej J.}",

note = "Funding Information: On the other hand it has been pointed out in \[9\] that measurements of B(K + ~ 7r+v~) and B(Kt. ~ ~r°v~) could also determine the unitarity triangle completely provided mt and Vcb are known. It should be stressed that these two decays are theoretically very clean. KL ~ 7r°v~ is dominated by short distance loop diagrams involving the top quark and proceeds almost entirely through direct CP violation \[1 0\]. K + ---, 7r+v~ is CP conserving and receives contributions from both internal top and charm exchanges. The recent calculation of next-to-leading QCD corrections to these decays \[1 1-13\] considerably reduced the theoretical uncertainty due to the choice of the renormalization scales present in the leading order expressions \[1 4\]. Since the relevant hadronic matrix elements of the weak current g),u (1 - )'5)d can be measured in the leading decay K + --* ~r°e+v, the resulting theoretical expressions for B(K + ~ 7r+v~) and B(KL ~ ~r°v~) are only functions of the CKM parameters, the QCD scale A~--g and the quark masses mt and mc. The long distance contributions * Supported by the German Bundesministerium fiir Forschung und Technologieu nder contract 06 TM 732 and by the CEC science project SC 1-CT91-0729.",

year = "1994",

month = jul,

day = "28",

doi = "10.1016/0370-2693(94)91034-0",

language = "English",

volume = "333",

pages = "221--227",

journal = "Physics Letters B",

issn = "0370-2693",

publisher = "Elsevier",

number = "1-2",

}