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CFT Occupancy dependence on Beam Luminosity

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 )

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CFT Occupancy dependence on Beam Luminosity

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  1. CFT Occupancy dependence on Beam Luminosity David Lam Nov 2003

  2. 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)

  3. 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.

  4. Occupancy distributions (180790) Blue: JT_45TT Red: JT_95TT Green: JT_125TT

  5. 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)

  6. Events between Feb. and Mar.

  7. Events in Aug (before shutdown)

  8. 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….

  9. 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.

  10. 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

  11. Occupancy vs. triggered luminosity (Set 1)

  12. Occupancy vs. triggered luminosity (Set 2)

  13. 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.

  14. 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?

  15. JT_45TT Events (Set 2)

  16. 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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