Global Mice Particle Identification
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Transcript of Global Mice Particle Identification
30 March 2004 1
Global Mice Particle Identification
Steve Kahn30 March 2004
Mice Collaboration Meeting
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Particle ID Elements Upstream Detectors:
Time of Flight system Rely on the time difference between stations
TOF0and TOF1 to provide velocity measurement. Upstream Cherenkov System
Verifies that the track is a muon.
Downstream Detectors: Time of Flight system
Verifies the existence and its time for a track exiting the detector solenoid.
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Particle ID Elements Downstream Detectors (cont.)
Downstream Cherenkov System Verifies that the track seen in TOF2 is an electron. Not sensitive to muons.
EM Calorimeter Shows whether a track that is seen in TOF2 has
an EM shower or not.
Tracking Systems Needed to know the particle momentum.
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Upstream TOF System Plots on the right show:
Upper plot shows time distributions at TOF0 and TOF1:
T=30 ns for these stations. Lower plot shows the transit
time of individual tracks. <T>=37.6 ns. T=176 ps The T corresponds well to
what we expect for with P=200 MeV
37.6 ns.
Obsolete
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Separating from in the Real World Tom Roberts has shown
an analysis using the Tof timing along with the momentum from the tracker to separate from .
Tof information is not sufficient by itself since there is some overlap in the and velocity distributions.
There are 17 in the lower plot; 5 of the overlap the distribution.
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Requirements for ToF Particle ID
The TofParticleID class will need: Access to TOF0 and TOF1 digitizations for the
same event (actually for the same track). Our ROOT structure keeps digitizations separate.
Knowledge of the Tracker reconstructed momentum.
All of the TOF0 hits in the pile-up time interval We need to estimate the likelihood that a time
coincidence is real or coincidental.
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The Upstream Cherenkov : Ckov1
C6F13 Radiator
CL
MIRROR
C6F14
PMT
UV
WINDOW
beam
mirror
PMT
0 20 40 60 80 100
Npe
e Candidates 186MeV/c 1cm C6F14
The figure shows clean separation of 186 MeV/c e, ,. However at 250 MeV/c we should expect significant overlap between and .
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Ckov1 Parameters and Status Status: we now see hits and digits for Ckov1. Radiator is C6F14 with nrefr=1.25
Thresholds are 0.7 (e), 140 () and 190() MeV/c respectively.
The Ckov1 alone will not be able to distinguish from since the velocities are close as we have seen.
The discrimination comes from the pulse height analysis, where the (dE/dx)Č is largely a function of alone.
With the knowledge of the momentum from the tracker we should be able to separate from .
The Ckov1 may be less sensitive to the background than TOF since TOF I is located in a position with lots of background.
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Ckov1 Particle ID Software Needs
The Ckov1 acts independent of the other particle ID detectors. Since it has a single PMT it cannot
measure the radius of the Cherenkov cone.
It will only measure a pulse height. It will need to know the momentum
from the tracker reconstruction.
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Electrons from Muon Decay are Present in the Downstream Track Sample
~1% of downstream tracks may be electrons, not muons.
80% of these electrons can be removed by kinematics, but this could bias the emittance measurement
Momentum Distribution
Angular Distribution
Spacial Distribution
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Downstream Detectors The figure on the
right shows the placement of the downstream detectors.
Both the Ckov2 and EMcal need a coincidence with the TOF III.
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Downstream Cherenkov Ckov2 is a threshold Cherenkov
The refraction index is nrefr=1.02 This corresponds to p>525 MeV/c for
muons But only pe>2.5 MeV/c for electrons If we see a signal in Ckov2 and TOF III it
is EM energy Single ionizing electron Twice minimum ionizing photon
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The Muon Beam Expands as the Field Falls Off
The calorimeter subtends 6060 cm
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Muon vs electron identification in EMcal
We have carried out simulation studies in G4MICE to optimize the mu/electron separation capabilities by varying: sampling fraction, i.e. lead layer thickness: 0.5-0.2 mm readout segmentation, i.e. cell size: 3.75x3.75 cm2, 3.25x3.25 cm2, 2.5x2.5 cm2, 2.5x4.0 cm2
We only consider a “pattern-based” identification algorithm, i.e. detection efficiency in layers >1
Stolen from A. Tonazzo
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Calorimeter signal, efficiency definition
Detection efficiency is defined by a cut on signal above noise threshold: 3-4 p.e.
PMT signalEnergy deposit“digitization”:•Light attenuation along fibers•Winston cone collection efficiency•Photocatode quantum efficiency
Stolen from A. Tonazzo
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Software Requirements of Particle ID Common Requirements:
Need to access information from more than one detector unit:
Upstream TOF requires two stations Downstream Ckov2 or Emcal also require TOF2 Need results of Tracker reconstruction.
Primarily the track momentum and error. Need to create an Event class that contains:
All detector results Digitizations for particle ID detectors Reconstruction for tracker detectors.
We are currently not organized that way.
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Particle ID Classes There should be a ParticleID class
for each ParticleID algorithm. There may be one or more than one
way to handle the information from each particleID detector system.
Each of these ParticleID classes should inherit from a ParticleIDBase class
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ParticleIDBase class Contain common quantities. Should contain:
Detector/Algorithm identification Reconstructed P, P from tracker for
track. Link to reconstructed track.
Probabilities of being ,,,e. Quality factor from algorithm
determination.