TY - JOUR

T1 - K → πvv̄

T2 - A model-independent analysis and supersymmetry

AU - Buras, Andrzej J.

AU - Romanino, Andrea

AU - Silvestrini, Luca

N1 - Funding Information:
We wish to thank M. Misiak for carefully reading the manuscript. This work has been supported by the German Bundesministerium fiir Bildung and Forschung under contract 06 TM 874 and DFG Project Li 519/2-2. L.S. acknowledges the partial support of Fondazione Angelo della Riccia, Firenze, Italy. The work of A.R. was partially supported by the TMR Network "Physics beyond the Standard Model" under EEC contract No. ERBFMRX-CT960090.

PY - 1998/6/1

Y1 - 1998/6/1

N2 - We present a model-independent analysis of new-physics contributions to the rare decays K+ → π+vv̄ and KL → π0vv̄. We parameterize the effects of new physics in these decays by two parameters: rK and the phase θK, with rK = 1 and θK = 0 in the Standard Model. We show how these parameters can be extracted from future data together with the relevant CKM parameters, in particular the angle β of the unitarity triangle. To this end CP asymmetries in B → ψKS and B → π+π- as well as the ratio |Vub/Vcb| have to be also considered. This analysis offers simultaneously some insight in a possible violation of a "golden relation" between K → πvv̄ decays and the CP asymmetry in B → ψKS in the Standard Model pointed out some time ago. We illustrate these ideas by considering a general class of supersymmetric models. We find that in the "constrained" MSSM, in which θK = 0, the measurements of Br(K+ → π+vv̄) and Br(KL → π0vv̄) directly determine the angle β. Moreover, the "golden relation" remains unaffected. On the other hand, in general SUSY models with unbroken R parity the present experimental constraints still allow for substantial deviations from rK = 1 and θK = 0. Typically 0.5 < rK < 1.3 and -25° < θK < 25°. Consequently, in these models the violation of the "golden relation" is possible and values for Br(K+ → π+vv̄) and Br(KL → π0vv̄) departing from the Standard Model expectations by factors 2-3 cannot be excluded. Simultaneously, the extraction of the "true" angle β from K → πvv̄ is not possible without additional information from other decays. Our conclusions differ in certain aspects from the ones reached in previous analyses. In particular, we stress the possible importance of left-right flavour-violating mass insertions that were not considered before.

AB - We present a model-independent analysis of new-physics contributions to the rare decays K+ → π+vv̄ and KL → π0vv̄. We parameterize the effects of new physics in these decays by two parameters: rK and the phase θK, with rK = 1 and θK = 0 in the Standard Model. We show how these parameters can be extracted from future data together with the relevant CKM parameters, in particular the angle β of the unitarity triangle. To this end CP asymmetries in B → ψKS and B → π+π- as well as the ratio |Vub/Vcb| have to be also considered. This analysis offers simultaneously some insight in a possible violation of a "golden relation" between K → πvv̄ decays and the CP asymmetry in B → ψKS in the Standard Model pointed out some time ago. We illustrate these ideas by considering a general class of supersymmetric models. We find that in the "constrained" MSSM, in which θK = 0, the measurements of Br(K+ → π+vv̄) and Br(KL → π0vv̄) directly determine the angle β. Moreover, the "golden relation" remains unaffected. On the other hand, in general SUSY models with unbroken R parity the present experimental constraints still allow for substantial deviations from rK = 1 and θK = 0. Typically 0.5 < rK < 1.3 and -25° < θK < 25°. Consequently, in these models the violation of the "golden relation" is possible and values for Br(K+ → π+vv̄) and Br(KL → π0vv̄) departing from the Standard Model expectations by factors 2-3 cannot be excluded. Simultaneously, the extraction of the "true" angle β from K → πvv̄ is not possible without additional information from other decays. Our conclusions differ in certain aspects from the ones reached in previous analyses. In particular, we stress the possible importance of left-right flavour-violating mass insertions that were not considered before.

UR - http://www.scopus.com/inward/record.url?scp=0032093115&partnerID=8YFLogxK

U2 - 10.1016/S0550-3213(98)00169-2

DO - 10.1016/S0550-3213(98)00169-2

M3 - Article

AN - SCOPUS:0032093115

SN - 0550-3213

VL - 520

SP - 3

EP - 30

JO - Nuclear Physics, Section B

JF - Nuclear Physics, Section B

IS - 1-2

ER -