# Presentation: 444584

## 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.