Transcript Time Resolution: trecon

Particle ID Software
Steve Kahn
Brookhaven National Lab
27 March 2003
Stephen Kahn
Particle ID Software
Mice Collaboration Meeting
Page 1
Particle Identification Systems
• Time-of-Flight system:
– Can separate  from  in the incoming beam by transit time
between two upstream TOF stations.
– Can separate e from  decay based on transit time.
• Cherenkov Detector Systems:
– Upstream system
• Supplied by University of Mississippi
– Downstream system
• Supplied by Université de Louvain.
• EM calorimeter:
– Downstream to separate electromagnetic energy (e, ) from .
Stephen Kahn
Particle ID Software
Mice Collaboration Meeting
Page 2
Glossary of Terms Used in MICE Software
• Simulation:
– Tracking through cooling and detector channels.
– Hits produced in active detectors contain the true track parameters.
– Output file is called Sim.out
• Digitization:
– A response to a track traversing a detector can be recorded.
• This recording is referred to as a digitization. It can be
– ADC counts representing the pulse height in a phototube.
– TDC counts representing a time measurement of the track
traversing the detector.
– These digitizations are not the true track variables. They represent
how the detector sees the track.
– The digitization output file is called Dig.out
Stephen Kahn
Particle ID Software
Mice Collaboration Meeting
Page 3
Glossary, continued.
•
•
Reconstruction:
– Although the detector digitizations contain all the information that can be
known about the, they are not directly realizable as kinematic variables.
– The reconstruction process translates the digits into kinematic variables as
best it can.
• These reconstructed variables will differ from the original simulated
measurements because of detector measurement errors.
– The output file of this process we call rec.out
• The original true variables are carried along for comparison, however
they will not be available for the experiment.
Analysis:
– Plotting detector simulated data.
– Comparing reconstructed variables to true variables.
– Determining the particle ID (is this a muon?)
– Calculating the emittance.
Stephen Kahn
Particle ID Software
Mice Collaboration Meeting
Page 4
TOF I Station
• TOF I is located after 1st diffuser where beam comes into
hall.
– This at –15 meters from center of cooling cells.
– TOF I is 1212 cm2 in size.
– TOF I is composed of two planes oriented in X and Y
respectively
• Each plane is segmented into two slabs with
phototubes on each end.
• Each slab is 1262.5 cm3.
• Using Bicron BC-420 fast Scintillator.
– Use Hamamatsu R4998 Phototubes on each end.
Stephen Kahn• 0.7 ns rise time,Particle
Page 5
160 IDpsSoftware
transit time jitter
Mice Collaboration Meeting
TOF II AND TOF III Stations
• TOF II (TOF III) is located before (after) the upstream (downstream)
measurement solenoid.
– This is at –5.544 meters from the center of the cooling cells.
– TOF II, III are 4040 cm2 in size.
– TOF II, III are composed of a single Y oriented plane.
• The plane is segmented into 8 slabs.
• Each slab is 4062.5 cm3.
– There is ~1 cm overlap at the edges of the slabs to allow crosscalibration.
• Bicron BC-404 Scintillator is used for these stations since it
has a longer attenuation length than the BC-420 used in station
I.
Stephen Kahn
– =1.7 meters.
Particle ID Software
Mice Collaboration Meeting
Page 6
TOF II and III continued
• The choice of phototube to use for the TOF II and TOF III
stations is complicated by the presence of fringing
magnetic field from the measurement solenoids.
– The field situation is shown in the following
transparencies.
– The fast phototube used for TOF I (R4998) does not
tolerate much magnetic field. The choices are
• Shield the fast Hamamatsu R4998 phototubes.
• Use the Hamamatsu R5505 fine mesh phototube
which can handle fields up to ~1 Tesla.
Stephen Kahn
Particle ID Software
Mice Collaboration Meeting
Page 7
Stephen Kahn
Particle ID Software
Mice Collaboration Meeting
Page 8
Stephen Kahn
Particle ID Software
Mice Collaboration Meeting
Page 9
Time Resolution: trecon-ttrue
TOF 1: =35 ps
TOF 2:
=108 ps
TOF 3:
=108 ps
Stephen Kahn
Particle ID Software
Mice Collaboration Meeting
Page 10
Transit Time from TOF1 to TOF11
~20 tracks
consistent
w/ electrons
from mu
decay
Stephen Kahn
Particle ID Software
Mice Collaboration Meeting
Page 11
Original Mississippi Downstream Cherenkov
•
The original downstream Č system
that was in the Dec ’02 version of
the simulation was based on a
10010015 cm3 aerogel radiator
segmented into an array of 1010
cm2 tiles, each with 2 PMT for
light collection.
– The geometry of this system
was implemented in Geant4.
– There was a detector response
coded for the PMTs, but it does
not appear to have a Č
response.
• Geant, itself, can create
and track Č photons.
Stephen Kahn
Particle ID Software
Mice Collaboration Meeting
Page 12
Upstream Cherenkov Detector
• The upstream Cherenkov detector will be based on the
Mississippi design. It is likely to be simpler than the
original.
• At this point it is not in the current MICE Geant package.
– It should be straight forward to modify the original
code from Romulus Godang to put it in.
Stephen Kahn
Particle ID Software
Mice Collaboration Meeting
Page 13
Downstream Cherenkov System
• Developed by G. Grégoire of
Université de Louvain.
• The radiator is aerogel with
nrefraction=1.02 and covers 9090 cm2
and has a thickness of 10 cm.
• Light is reflected by 45º mirrors into
20 diameter Hamamatsu R3600-02
PMTs. (Super K kind).
– Large gain 3106 needed for low
Č light yield in aerogel.
– 24 cm PMT photocathode radius.
Stephen Kahn
Particle ID Software
Mice Collaboration Meeting
Page 14
Spatial distributions
qxz
1000
Muons
1500
Muons
N
Electrons
Electrons
1000
500
500
0
-40
-20
0
20
X (mm)
40
0
-300
Theta XZ (degrees)
-200
-100
qy
1000
Muons
0
100
300
x
1500
N
Muons
z
Electrons
200
Electrons
1000
Slide from Gh. Grégoire
July 9, 02 Presentation
500
500
0
-40
-20
0
20
Y (mm)
40
0
Theta YZ (degrees)
-300
-200
-100
0
100
200
300
Beam spot ~300 mm diam. ~ size of the radiator
Divergence q ~ 20°
Stephen Kahn
Numerical aperture (f-number) = ~ 1.5
Particle ID Software
Mice Collaboration Meeting
f 
y
1
2 sin q
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Angular and energy distributions
1400
Angle with respect to beam axis
Muons
1200
Electrons
1000
N
800
600
400
200
0
0
10
20
30
40
Theta (degrees)
1800
Muons
N
1600
Kinetic energy distribution
Electrons
1400
1200
1000
Slide from Gh. Grégoire
July 9, 02 Presentation
800
600
400
Electrons have very low energies ( E< m )
200
0
0
100
Stephen Kahn
200
300
400
500
Total energy (MeV)
It is not obvious (to me) to separate e-
on calorimetric principles at such low
electron energies!
Particle ID Software
Mice Collaboration Meeting
Page 16
Current Status of the Downstream Č Geant
Software
• A model of the Louvain Č detector has been coded.
– DetModel classes: CKOV2Tracker
• CKOVHit and CKOVSD slightly modified, but are
common with Upstream Č
– Config classes: CKOV2TrackerGeom
– Interface classes: CKOV2HitBank
• Inherits from CKOVHitBank
– DetResp classes: CKOV2Digits
– Calib classes: CKOV2DigitParams
Stephen Kahn
Particle ID Software
Mice Collaboration Meeting
Page 17
Current Status of Č Software
• The CKOV2Digit does try to simulate what each of the 4
PMTs would see from the Č process.
– There is no signal for imaginary Č angles. µ’s and e’s
will look different.
• This new downstream Č classes exists on my computer.
– They are not yet in CVS (Yagmur says that means they
do not exist)
– They compile and link. They are being verified.
Stephen Kahn
Particle ID Software
Mice Collaboration Meeting
Page 18
Particle ID Package Status
Package
Geometry Digitization
Reconstruction
Analysis
TOF
√
√
√
?
Orig Č
√
√
Downstream Č
√
√
EM Cal
√
√
Upstream Č
Stephen Kahn
Particle ID Software
Mice Collaboration Meeting
Page 19