Violation in Mixing

2.2 The BABAR detector. 51
Integrated Luminosity (fb -1 )
62
60
58
56
54
52
50
48
46
44
42
40
38
36
34
32
30
28
26
24
22
Dec 1
Nov 1
Oct 1
Sep 1
Aug 1
Jul 1
Jun 1
May 1
Apr 1
Mar 1
Feb 1
Jan 1
Dec 1
Nov 1
Oct 1
Sep 1
Aug 1
Jul 1
Jun 1
May 1
Apr 1
Mar 1
Feb 1
Jan 1
Dec 1
Nov 1
Oct 1
20
18
16
14
12
10
8
6
4
2
0
1999
BABA R
PEP-II Delivered 61.58/fb
BABAR Recorded 58.44/fb
BABAR off-peak 6.49/fb
2000
2001
Efficiency (percent)
100
90
80
70
60
50
Dec 1
Nov 1
Oct 1
Sep 1
Aug 1
Jul 1
Jun 1
May 1
Apr 1
Mar 1
Feb 1
Jan 1
Dec 1
Nov 1
Oct 1
Sep 1
Aug 1
Jul 1
Jun 1
May 1
Apr 1
Mar 1
Feb 1
Jan 1
Dec 1
Nov 1
Oct 1
40
30
20
10
0
1999
2000
BABA R
Figure 2-2. Left plot: integrated luminosity plot including 1999, 2000 and 2001 periods: the red line
represents the total BABARrecorded luminosity. The green line shows the off peak luminosity taken. Right
plot: BABAR efficiency.
2.2 The BABAR detector.
The BABAR detector has been optimized to reach the primary goal of the �È asymmetry measurement. This
measurement needs the complete reconstruction of a � decay in a �È eigenstate (possibly with good
efficiency since the branching fraction is so small), the flavour identification (tagging) of the non-�È �
and a measure of the distance of the two decay vertices. To fulfill these needs, the detector is provided
with a magnetic field to measure charged particles momenta, it is able to reconstruct tracks coming from the
production vertex, to recognize leptons and � and à mesons and to measure photon energy and direction.
The BABAR detector is shown in figure 2-3 and it includes the following subsystems:
a silicon vertex detector: ËÎÌ (Silicon Vertex Tracker);
a drift chamber: ��À;
a particle identification system: �ÁÊ� (Detector of Internally ReflectedČerenkov light);
an electromagnetic calorimeter: ��;
a muon and neutral hadron identification system: Á�Ê (Instrumented Flux Return).
2001
THE BABAR EXPERIMENT