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The rare decay in the Standard Model. Da f ne 04, June 2004. Christopher Smith Laboratori Nazionali di Frascati. G. Isidori, R. Unterdorfer, C.S., hep-ph/0404127. In K pp , CP-violation is small e 10 - 3 , and direct CPV even smaller e ’ /e 10 - 3 .
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The rare decay in the Standard Model Dafne 04, June 2004 Christopher Smith Laboratori Nazionali di Frascati G. Isidori, R. Unterdorfer, C.S., hep-ph/0404127
In Kpp, CP-violation is small e 10-3, and direct CPV even smaller e’/e 10-3. In contrast, direct CP-violation is expected to be dominant (or at least sizeable) in . Introduction Large direct CP-violation Small theoretical uncertainties Hadronic uncertainties plague the theoretical analysis of e’/e. In contrast, are semi-leptonic processes and the direct-CPV contribution can be computed with high accuracy. Indeed, the hadronic matrix element can be obtained from .
Theoretical Structure Direct CP-violation Indirect CP-violation CP-conserving Long-distance Chiral Perturbation Th. (KL-KS mixing) Long-distance ChPT, VMD, ... Short-distance Operator Product Exp. (large Z, W, t mass) Final State 0++: (Final State 2++: ) The only piece for ~ ~ ~ ~
Outline of the computation The leading order is obtained from the charged pion loop e+e- : helicity suppressed m+m- : leading CPC (0++) Equivalently, we can compute Provided is a function of T² only.
Standard Model Predictions I • with and . • with counterterm . • theoretical errors of 10% or less on all CPV coefficients. • conservative error estimate of 30% for the CPC term. Bounds on Imlt Current experimental bounds from KTeV imply:
Standard Model Predictions II Branching Ratios Constructivenow favored by two independent analyses* Destructive * G. Buchalla, G. D’Ambrosio, G. Isidori, Nucl.Phys.B672,387 (2003) S. Friot, D. Greynat, E. de Rafael, hep-ph/0404136
Sensitivity to New Physics Ratios of B Kp modes could be explained by enhanced electroweak penguin contributions*. Those processes would then affect the Wilson coefficients: and enhance the BR’s: * A. J. Buras, R. Fleischer, S. Recksiegel, F. Schwab, hep-ph/0402112
Prospects The set of decays , and - very clean theoretically, - is extremely well suited to test the SM, - very sensitive to New Physics signal, - non-trivial information on the nature of New Physics. On the experimental side, we would need : Required experimental sensitivity expected soon. : The main uncertainty in the CPV comes from aS. : Both rate (for CPC-0++) and spectrum (for CPC-2++).