Vus from τ: status and perspectives at new facilities

by Dr Emilie Passemar (Los Alamos National Laboratory, USA.)

Thursday 10 Jan 2013, 15:00 → 17:00 Europe/Rome

Aula Seminari (LNF INFN)

Several experimental collaborations have recently devoted considerable effort to the precise measurements of hadronic τ decays. Moreover, new measurements are expected at the Tau-Charm and B (Belle-II) factories. These measurements allow us to study QCD at low energy but also to test the presence of physics beyond the Standard Model. A famous test consists in the determination of the CKM matrix element |Vus| and the test of unitarity of the first row of this matrix. In this talk, we will review the different possibilities offered by the hadronic τ decays to extract this matrix element. All these determinations require precise calculations of the hadronic quantities involved (form factors, decay constants, correlators, etc) that have become at reach with recent advances in QCD. We will present a new extraction relying on recent measurements of the τ → Kπντ decay from Belle and BaBar collaborations, together with the use of dispersion relations and precise measurements of the kaon leptonic and semi-leptonic decays. Finally, we will discuss the prospects of such an analysis at the future flavour factories.

Slides LNF_EPassemarv1.pdf