Institut de Recherche sur les Lois Fondamentales de l'Univers

Goal

The main goal of the experiment is to perform a complete study of CP violation (CP is the symmetry linking particules and antiparticules) in the system of B mesons.

More generally the experiment studies the physics of heavy flavors: mesons and baryons with a b or a c quark and tau leptons.

Context

The ARGUS experiment at Hambourg and the CLEO experiment at Cornell in the eighties and nineties were the first "B factories" built to study the physics of B mesons. BABAR and the BELLE experiment at KEK in Japan are "B factories" from the second generation. They are able to study CP violation.

Themes/programms

The energy content of the Universe/Antimatter and CP violation.

Localisation

The experiment is located at Stanford Linear Accelerator Center (SLAC) at Stanford University in the United States, using the PEP-II electron-positron collider.

Data taking started in may 1999.

Contribution from Dapnia

The contributions

Dapnia played a major role in the construction and running of the DIRC detector (1995-1998). The DIRC is the main detector for particle identification in BABAR. 

In particular, Dapnia is responsible for:
- the mechanical structure of the Cerenkov light detector;
- the 11000 photomultiplicator tubes;
- the magnetic shielding;
- the calibration system;
- the reconstruction code;
- the alignement procedure.

Dapnia also plays a very active role in data analysis:
- measure of the alpha angle of the unitarity triangle (with the B decays to rho pi and rho rho);
- measure of sin(2beta+gamma) (B→D* pi mode);
- study of the B→K* rho modes;
- study of the eta_c meson, measure of the beta angle;
- measure of the Vub parameter;
- study of CP, T, and CPT violation in dilepton events.

Scientific responsabilities

Physicists from Dapnia have had important positions in the collaboration:
- physics analysis coordinator (2000-2001) ;
- chair of the speakers bureau (1997-1998) ;
- conveners of several physics analysis groups (dileptons, inclusive hadronic B meson decays, time dependent analyses of B meson decays to charm);
- co-system manager of the DIRC detector (1995-1998 and 2003-2007).

Scope of the experiment

The BABAR experiment has been one of the major experiment in High Energy Physics during the past years. Dapnia and SPP have been heavily involved with a maximum of 14 physicists at the same time.

Contact

Georges Vasseur, head of the BABAR group at Saclay.

The official website