# EPS HEP 2015

22-29 July 2015
Europe/Vienna timezone

## Flavours at a high luminosity e+e- collider (FCC-ee)

Jul 25, 2015, 10:50 AM
15m
HS21

### HS21

talk Flavour Physics and Fundamental Symmetries

### Speaker

Stephane Monteil (Univ. Blaise Pascal Clermont-Fe. II (FR))

### Description

A possible long-term strategy for high-energy physics at colliders considers a tunnel of about 100 km circumference, which takes advantage of the present CERN accelerator complex.A possible first step of the project is high-luminosity $e^+ e^−$ collider aimed at studying comprehensively the electroweak scale with centre-of-mass energies ranging from the $Z$ pole up to beyond the $t \overline{t}$ production threshold. A 100 TeV pp collider is considered as the ultimate goal of the project. FCC groups have been formed in a design study hosted by CERN, aiming at a CDR in time for next European Strategy milestone (2018-2019). The unprecedented statistics at the Z pole ($O(10^{12-13})$ Z decays potentially delivered by the $e^+ e^−$ collider can be studied in particular to explore further the Flavour Physics case at large. We’ll discuss the possible measurements of rare decays of b-hadrons, which can complement the anticipated knowledge from the foreseen b-Physics programs. This very statistics can be used as well to study Lepton Flavour Violating Z decays, which would serve as an indisputable evidence for New Physics if seen. In absence of signal, we’ll discuss the constraints to be set on models embedding additional right-handed sterile neutrinos. Heavy sterile neutrinos, addressing in some models both the questions of dark matter and baryonic asymmetry in the Universe, can also be searched for directly at FCC-$ee$. Prospects of these direct searches will be described.