Authors: Andrzej J Buras Dario Buttazzo Jennifer GirrbachNoe Robert Knegjens
Publish Date: 2015/11/05
Volume: 2015, Issue: 11, Pages: 33-
Abstract
In view of the recent start of the NA62 experiment at CERN that is expected to measure the K+to pi+nu overlinenu branching ratio with a precision of 10 we summarise the present status of this promising decay within the Standard Model SM We do likewise for the closely related K Lto pi0nu overlinenu which will be measured by the KOTO experiment around 2020 As the perturbative QCD and electroweak corrections in both decays are under full control the dominant uncertainties within the SM presently originate from the CKM parameters V cb V ub and γ We show this dependence with the help of analytic expressions as well as accurate interpolating formulae Unfortunately a clarification of the discrepancies between inclusive and exclusive determinations of V cb and V ub from treelevel decays will likely require results from the Belle II experiment available at the end of this decade Thus we investigate whether higher precision on both branching ratios is achievable by determining V cb V ub and γ by means of other observables that are already precisely measured In this context ε K and ΔM sd together with the expected progress in QCD lattice calculations will play a prominent role We find mathrmmathcalBleftK+to pi+nu overlinenuright=left911 pm 072right times 1011 and mathrmmathcalBleftK Lto pi0nu overlinenurightBig = left300 pm 030right times 1011 which is more precise than using averages of the present treelevel values of V cb V ub and γ Furthermore we point out the correlation between mathrmmathcalBleftK+to pi+nu overlinenuright overlinemathrmmathcalBleftB mathrmsto mu+muright and γ within the SM that is only very weakly dependent on other CKM parameters Finally we update the correlation of K Lto pi0nu overlinenu with the ratio ε′ /ε in the SM taking the recent progress on ε′ /ε from lattice QCD and the large N approach into accountThis article is published under an open access license Please check the Copyright Information section for details of this license and what reuse is permitted If your intended use exceeds what is permitted by the license or if you are unable to locate the licence and reuse information please contact the Rights and Permissions team
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