Logo of the experiment.
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.
Site of the experiment.
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.
Mesurement of the alpha angle of the unitarity triangle.
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.
last update : 03-17 00:00:00-2010 (2226)
Energy content of the Universe 
Antimatter and CP violation
The Electronics, Detectors and Computing Division The Particle Physics Division The Systems Engineering Division
 | Investigation means
High luminosity asymmetric electron-positron collider (9 GeV electron beam and 3.1 GeV positron beam).
BABAR high energy physics detector.
Computing: data reconstruction, simulation, data analysis.
Technical description
The BABAR detector is composed of five sub-detectors:
- silicium vertex detector;
- drift chamber to detect charged particules;
- Cerenkov detector for particle identification;
- electromagnetic calorimeter to measure neutral particules;
- external muon detector.
Il comprend également un solénoide supramagnétique.
Specificities
The study of ... More » |
 | History and main milestones
November 1993: start of the collaboration.
May 1999: beginning of data taking.
Summer 2001: first observation of CP violation in the B meson system.
Summer 2004: first observation of direct CP violation in the B meson system.
Summer 2005: the accelerator is operating at more than three times the nominal instantaneous luminosity.
September 2008: scheduled end of data taking.
Main achievements
First observation of CP violation in the B meson system in 2001.
Discovery of nes Ds mesons in 2003.
... More » |
 | International collaborationBABAR is an international collaboration with more than 600 physicists from 11 countries (United States, Italy, France, United Kingdom, Germany, Canada, Russia, China, Netherlands, Norway, Spain). Five French laboratories are involved in the experiment:
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