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CFT Occupancy dependence on Beam Luminosity. David Lam Nov 2003. CFT Occupancy vs. Luminosity. Choose 3 classes of events for the study: Zero-biased triggered Minimum-biased triggered Jet triggered Events with delivered luminosity range from 6E30 to ~40E30 (cm -2 s -1 ) - PowerPoint PPT Presentation
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CFT Occupancy dependence on Beam Luminosity
David Lam
Nov 2003
CFT Occupancy vs. Luminosity
Choose 3 classes of events for the study: Zero-biased triggered Minimum-biased triggered Jet triggered
Events with delivered luminosity range from 6E30 to ~40E30 (cm-2 s-1)
Two set of events: Set 1: 10 events between Feb and Mar 2003 Set 2: 11 events in August (just before the shutdown)
Method Use a modified version of cft_offline_mon Use D0TriggerFilter to pick out the desired events. Once the desired trigger is found, no further restrictions
are applied to other triggers. For example, some of the min-biased events may also have zero-biased and jet triggers.
However, due to the large prescales applied to min-biased and zero-biased events (in order of 105 – 106), we don’t see any overlapping of triggers in our data sample.
That is, all the min-biased events found in the data contain min-biased trigger only. This applies to zero-biased events as well.
Occupancy distributions (180790)
Blue: JT_45TT
Red: JT_95TT
Green: JT_125TT
Results
Fitting results show occupancies increased with luminosity as expected Green: Zero-biased triggered Red: Min-biased triggered Blue: JT_45TT triggered Grey: JT_95TT triggered Yellow: JT_125TT triggered (for set 2 only)
MC min-biased and zero-biased events are also included.
When extrapolated, at 200E30, jet triggered occupancy is approximately: 0.40 - 0.44 (CFTX1)
Events between Feb. and Mar.
Events in Aug (before shutdown)
Zero-biased and min-biased results
Zero-biased events triggered on beam crossing: Contain mostly electronic background “noise” Occupancy variation due to p/anti-p halo
Min-based events triggered on collision: Signal in luminosity monitors above threshold on both ends Number of collision increases with luminosity – Poisson
distribution. Supposedly, occupancies increase faster with luminosity
compared to zero-biased event. But, slopes for the fits of min-biased events are lower
than zero-biased and jet triggered – so dig deeper….
Jet triggers results
The different jet trigger fits (JT_45TT, JT_95TT and JT_125TT) look similar, and the slopes are close to the slopes of zero-biased events.
As the delivered luminosity reaches 200E30, the average CFT occupancies for Axial layer 1 is close to 0.40-0.44.
Trigger luminosity
Look into the recorded luminosity for each event Recorded luminosity are stored by luminosity
block (LBN), which usually corresponds to time interval of 1 minute.
Multiply the recorded luminosity by appropriate L1 prescales to obtain trigger luminosity.
Plot occupancy vs. trigger luminosity for each trigger. Luminosities are in unit of (1030 cm-2), which corresponds to luminosity in a LBN
Occupancy vs. triggered luminosity (Set 1)
Occupancy vs. triggered luminosity (Set 2)
Result (cont.)
The fits look similar to the occupancy vs. beam (delivered) luminosity plots.
Again, the min-biased events have the smaller slopes compared to zero-based and jet triggered events. This suggest zero-biased events not only contain detector noise but also include min-biased events as well.
JT_95TT trigger is not prescaled for Runs in set 1. This trigger is used to compare with prescaled JT_45TT trigger, and the fit for the two triggers agree well.
JT_45TT trigger for set 2
It turns out JT_95TT is also not prescaled for Runs in set 2 as well, by comparing with JT_125TT trigger (which is never prescaled).
However, the triggered luminosity for JT_45TT for set 2 are about 10 times larger than expected (after prescale correction) – suggest something wrong with the prescales?
JT_45TT Events (Set 2)
Conclusion
This confirms that CFT occupancies increase with delivered luminosities.
The dependencies are linear in the range of beam luminosities investigated (6E30 ~ 40E30), for events of different triggers.
If such dependencies still hold in luminosity range up to 200E30, the expected occupancy for Axial layer 1 will be around 0.40 – 0.44.
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