neutron background simulation
DESCRIPTION
Neutron Background Simulation. R. Wilkinson. Neutron Background Simulation. Long-lived neutrons created, diffuse around collision hall They get captured by nuclei, emitting a photon Compton scattering or photoelectric effect makes MeV electrons, which cause hits in muon chambers. - PowerPoint PPT PresentationTRANSCRIPT
Neutron Background SimulationNeutron Background Simulation
R. WilkinsonR. Wilkinson
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Neutron Background SimulationNeutron Background Simulation
Long-lived neutrons created, Long-lived neutrons created, diffuse around collision diffuse around collision hallhall
They get captured by nuclei, They get captured by nuclei, emitting a photonemitting a photon
Compton scattering or Compton scattering or photoelectric effect makes photoelectric effect makes MeV electrons, which MeV electrons, which cause hits in muon cause hits in muon chamberschambers
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Because neutrons can live Because neutrons can live up to a second before up to a second before making a signalmaking a signal
They can’t be treated like They can’t be treated like ordinary minimum-bias ordinary minimum-bias pileup, because millions of pileup, because millions of collisions in the past can collisions in the past can contributecontribute
Why is neutron background hard to Why is neutron background hard to simulate?simulate?
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QGSP_BERT_HP physics tablesQGSP_BERT_HP physics tables
Other options needed to give long-lived, low energy particlesOther options needed to give long-lived, low energy particles No pT cuts or eta cutsNo pT cuts or eta cuts Long tracking timeLong tracking time No neutron thresholdNo neutron threshold
GEANT SimulationGEANT Simulation
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Old MethodsOld Methods
Parametrization (UC Davis)Parametrization (UC Davis)
Database of Chamber Hit Patterns (Wilkinson)Database of Chamber Hit Patterns (Wilkinson) Meant to be added only to chambers with signalMeant to be added only to chambers with signal
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Usually only affect one layer, sometimes two, Usually only affect one layer, sometimes two, sometimes more.sometimes more.
At At L L =10=103434, we expect at most 3% chance of a , we expect at most 3% chance of a neutron per chamber, per BX.neutron per chamber, per BX.
We had thought that the trigger would suppress We had thought that the trigger would suppress most of these, but it doesn’t!most of these, but it doesn’t!
We had thought suppression used LCTs, We had thought suppression used LCTs, which require four layerswhich require four layers
So we thought we should only add neutron So we thought we should only add neutron hits to chambers that already have signalhits to chambers that already have signal
In reality, it uses CLCT pretriggers, which In reality, it uses CLCT pretriggers, which only require two layersonly require two layers
Which means we need to simulate all Which means we need to simulate all chambers, and implement a more chambers, and implement a more accurate zero suppression in the accurate zero suppression in the simulationsimulation
CSC-specific issuesCSC-specific issues
Events to add, 10^34, 24 bx
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Shielded G3
G4
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Treat neutrons like regular pileupTreat neutrons like regular pileup
Take SimHits with a high time of flight, change the TOF to 0-25 ns, and save Take SimHits with a high time of flight, change the TOF to 0-25 ns, and save the new hits in a different collection.the new hits in a different collection.
SimMuon/Neutron/src/NeutronProducer.ccSimMuon/Neutron/src/NeutronProducer.cc Keep relative timing for hits within the same chamberKeep relative timing for hits within the same chamber
Drop all data except the high-TOF hits from the eventsDrop all data except the high-TOF hits from the events
Let the MixingModule mix in the new events.Let the MixingModule mix in the new events. Use the average number of interactions per bunch crossing, including gapsUse the average number of interactions per bunch crossing, including gaps Should get the correct occupancy, assuming steady-state running.Should get the correct occupancy, assuming steady-state running.
Should just work for DT & RPCShould just work for DT & RPC
WorkplanWorkplan
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Current Simulation:Current Simulation: Saves any layer which has signalSaves any layer which has signal Only simulates and reads out groups of strips (CFEBs) containing or near Only simulates and reads out groups of strips (CFEBs) containing or near
signalssignals Doesn’t always make all the noise strips neededDoesn’t always make all the noise strips needed
What’s needed:What’s needed: Create a transient container of unsuppressed digisCreate a transient container of unsuppressed digis
Neutron hits come from MixingModuleNeutron hits come from MixingModule Run the L1 trigger primitive simulationRun the L1 trigger primitive simulation
Move the module from the L1Trigger sequence to the SimMuon sequenceMove the module from the L1Trigger sequence to the SimMuon sequence Code would still live in L1TriggerCode would still live in L1Trigger
Input is unsuppressed digis Input is unsuppressed digis Creates a new transient collection of pretrigger digisCreates a new transient collection of pretrigger digis
Make a zero suppression module which produces the suppressed digisMake a zero suppression module which produces the suppressed digis Generating noise, if neededGenerating noise, if needed Prototype in SimMuon/CSCDigitizer/src/CSCDigiSuppressor.ccPrototype in SimMuon/CSCDigitizer/src/CSCDigiSuppressor.cc
CSC WorkplanCSC Workplan