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CKMFitter

Presentation

CKMfitter is a group of about ten theoreticians and experimentalists who propose global electroweak interpretations of the Flavour Physics data in the framework of the Standard Model (SM) of Particle Physics and beyond (BSM). The involved laboratories are by alphabetical order : CPT (Marseille), KEK (Japan), LAPP (Annecy-Le-Vieux), LPC (Clermont), LPNHE (Paris), LPT (Orsay), and the Universities of Berlin (Germany) and Melbourne (Australia). A rather complete description of the group and its activities (including the main results and publications) can be found here : http://ckmfitter.in2p3.fr. In particular, we provide the High Energy Physics community with the metrology of the four SM parameters describing the quark flavour charged current transitions in the Cabibbo-Kobayashi-Maskawa (CKM) paradigm, established with frequentist techniques to analyse the data.

The members of the group and their current activities

The members of the LPC group are Olivier Deschamps (MCF, since 2005), Stéphane Monteil (PU, since 2005), Valentin Niess (CR, since 2008) and Jean Orloff (PU, since 2011). Their current activities, specific to the LPC group, are gathered in four actions, to endorse the newly defined vocabulary of the laboratory projects.

- The angle \alpha denotes the weak phase responsible of the mixing-induced CP asymmetries in the quark transitions b \to u \bar u d. In the SM framework, \alpha can be interpreted as -\arg{V^*_{ub}V_{ud} / V^*_cb V_cd} where the V_{ij} are elements of the CKM matrix. Three methods can be used to determine \alpha. The most precise is nowadays the isospin analysis of the series of charged and neutral decay modes B \to \rho\rho. The experimental measurements which serve as inputs of the \alpha determination are published by the B-factories experiments and the LHCb experiment. The CKMfitter group provides results for the three methods as well as their average, gathering all experimental results published so far. Proponents : O. Deschamps and V. Niess.

- The Constrained Minimal Flavour Violation Model : a minimal bottom-up extension of the Standard Model embracing a large class of New Physics (NP) models consists in assuming that BSM Physics can modify SM amplitudes while not bringing any additional CP-violating phase. In a model-independent approach, 5 NP parameters are defined to account for BSM amplitudes in electroweak transitions. This idea was initially brought by A. Buras. We have analysed the constraints issued from the flavour Physics data on the related NP parameter governing the neutral kaon and B meson mixing processes. This action is at an exploratory stage. Proponents : J. Orloff and S. Monteil.

- Studies of systematic uncertainties : the treatment of theoretical uncertainties, in particular related to the knowledge of the strong interaction, is a key stone to any sound electroweak interpretation of the flavour Physics data. Elsewhere, the frequentist statistical treatment used in the CKMfitter group is subjected to intrinsic systematic uncertainties related to the employed methodology. We’re studying new avenues to tackle both problems. Proponent : V. Niess.

-  CKM live  : the CKMfitter software, while it was written in Fortran language, used to be made publicly available. The developments of a new CKMfitter software aimed at handling more sophisticated NP analyses were making use of the Mathematica package and was forbidding any public release, which the group regrets unanimously. We therefore thought of a workaround and are developing a web application which will allow a user to build up a his/her own analysis of the flavour Physics data. The LPC is coordinating this project and provides the technical support for the development of the application. The application should be online by the 2015 Winter conferences. Proponents : Alexandre Claude (IT-LPC) and S. Monteil.

 
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