Relationship between Pileup and inelastic collision events

[Ruihu Zhu]

TL;DR Summary

why number of inelastic event approximately equals pileup event in detector?

I've read some stuff on pileup.In one paper, it says the number of inelastic event approximately equals pileup event in detector.I don't quitely understand it.Can someone explain?Thanks

 

[mfb]

Pileup is the number of events seen in the detector. Inelastic collisions are usually seen by the detectors, elastic collisions are often not (depends on the detector, however).

 

[Ruihu Zhu]

Pileup is the number of events seen in the detector. Inelastic collisions are usually seen by the detectors, elastic collisions are often not (depends on the detector, however).

Sir,I'd like to ask a few more questions.Does it mean inelastic collisions cause pileup?In one paper,it directly uses inelastic cross section to calculate number of pileup.I'd like to know the reason to do so.Thanks.

 

[mfb]

All collisions that lead to tracks in the detector contribute to pileup. That typically means inelastic collisions, yes, but it depends on the detector.

 

[Ruihu Zhu]

All collisions that lead to tracks in the detector contribute to pileup. That typically means inelastic collisions, yes, but it depends on the detector.

There's another question confusing me.In the lessons I've learned,pileup refers to muti-collision happening at the same time which causes pileup of detector signals.Pileups are not the events we are interested in.One should reduce number of pileup.But as what you reply before, detector can only see pileup event.This seems like pileups include events we are interested in. It seems that there's a conflict.

 

[Paul Colby]

In low energy nuclear physics the meaning of pileup is accidental overlap of events within the resolution (pulse) width of the detector. Pulses 'pile up' when they accidentally overlap in time. The pileup rate is computed by assuming events are Poisson distributed in time with the rate estimated by the observed count rate.

 

[mfb]

There's another question confusing me.In the lessons I've learned,pileup refers to muti-collision happening at the same time which causes pileup of detector signals.Pileups are not the events we are interested in.One should reduce number of pileup.But as what you reply before, detector can only see pileup event.This seems like pileups include events we are interested in. It seems that there's a conflict.

Two interesting collisions in the same event is essentially non-existing, so you only have events with zero interesting collisions and events with one interesting collision. Here is a non-intuitive result: The average number of extra "boring" collisions is the average number of collisions. If you have 0.05 collisions per bunch crossing on average, then your interesting collisions will have an average of 0.05 other collisions in the same event. To a good approximation in most experiments this average is the inelastic cross section times the integrated luminosity per bunch crossing. Mathematically this is related to the Friendship paradox. By choosing an interesting event you are more likely to choose an event with more collisions, simply because they have a higher chance to have an interesting event.