10 - H1 - Desy

56 Event reconstruction and preselection
TE 1 [a t1] rate (kHz)
0.14
0.12
0.1
0.08
0.06
0.04
0.02
a.
s67 TE 2 L1 [a raw t2] rate (kHz) (Hz)
16
14
12
10
8
6
4
2
b.
0
200 250 300 350 400
day of ’0607
day of ’0607
0
200 250 300 350 400
day of ’0607
s67 prescale factor
6
5
4
3
2
1
0
c.
200 250 300 350 400
day of ’0607
s67 L1 raw rate (Hz)
16
14
d.
12
10
8
6
4
2
0
0 5 10 15 20 25 30 35 40 45
30
inst. lumi. (10 cm -2 s -1 )
s67 prescale factor
Figure 4.3: Rates for the TE1 (a), s67 (b), s67 prescale factor (c) as a function of time
and the s67 trigger rate as a function of instantaneous luminosity (d) for the 2006/07 e + p
data.
4.3.2 Trigger efficiency
6
Trigger efficiency has been studied using events triggered by a set of independent conditions,
such as detection of the scattered electron in the SPACAL or ETAG.
The main trigger monitor sample is triggered by a localised energy deposition (E IET )
in the outer region 2 of the SPACAL. Three different subtriggers are used with different
energy thresholds and different prescale factors. The subtrigger s3, with the highest
energy threshold of 9 GeV has a prescale equal to one, while subtriggers with lower energy
thresholds are consequently downscaled. The radial position (R Spacal ) of the electron
candidate is further verified on L2. The L2 condition for s9 has been changed in 2005
from run 421376 on from R Spacal > 30 cm to R Spacal > 40 cm.
The alternative monitor sample was used to evaluate possible systematic bias of the trigger
efficiency determination. It has been triggered by the scattered electron in the electron
tagger (E ET6 ) placed 6 m away from the main detector and a sufficient number of high
2 The outer region is defined as everything except the inner region being the square 8.1 × 8.1cm 2 in
the centrum of the SPACAL.