The BeamCal Simulation Project

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• The BeamCal
  Simulation Project
• Progress Report
• Keith Drake, Tera Dunn, Jack
  Gill,
• Gleb Oleinik, Uriel Nauenberg
• University of Colorado at
  Boulder

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Beam Calorimeter Studies

Two photon process cross section about 105
larger than SUSY cross section. Serious source
of background for SUSY if not tagged .
Pointed out by our group around 1998
3

2 Photon Process
e e
Very forward into BEAMCAL
- -
?
q , l
Very forward into BEAMCAL
in the detector
?
q , l
e- e-
4

Lumi Cal
-7 mrad ent.
7 mrad exit
Beam Cal
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• Solenoid field keeps the low
  energy charged particle in the forward direction.
  Beam hole is at 7 mrad. Need to add an x field
  component to move low energy charged particles in
  the 7 mrad direction. Anti-DiD
• dipole field proposed by Andrei Seryi.

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Beamstrahlung ee- pairs. Energy deposited in
0.25 x0.25 cm2 cells.
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Outside Beam Pipe
Integrated

Energy into the Beam Pipe is TeV
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Shower in Beamcal from 2 ? process alone

side view
head-on view
core of shower
Radius of 25 mm
Radius of 25 mm
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• head on view

side view
beamstrahlung
electron from 2? process
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Beamstrahlung Energy Deposition in a Tile

Tile at start of BeamCal
Tile 3.0 cm in
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Beamstrahlung Energy Deposition in a Tile

Tile 4.7 cm in
Tile 6.0 cm in
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• Consequences of Beamstrahlung Energy
• Deposition
• Energy Deposition is not Gaussian until one
• reaches a depth gt 3 cms.
• Distribution is very wide and hence affects
  
• energy resolution if we subtract an
  average
• value.
• This problem is seen in the study how to
  measure
• the electron/positron energies.
  Resolution.

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Electron from 2 photon overlayed
Beamstrahlung
Beamstrahlung with average subtracted
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Clustering Cuts in Depth and Energy, Example 1

Beamstrahlung Electron from 2-photon
Beamstrahlung Alone
Cut 30 mm
Work in Progress
Cut 10 MeV
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Clustering Cuts in Depth and Energy, Example 2

Beamstrahlung Electron from 2-photon
Beamstrahlung Alone
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Clustering Cuts in Depth and Energy, Example 3

Beamstrahlung Electron from 2-photon
Beamstrahlung Alone
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Energy observed as a function of distance from
center of BeamCal

f
Exit Beam Pipe
r
Entrance Beam Pipe
?f 5 deg
?r 1 mm
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Energy Deposition versus r and f

F0.0
F30.0
30.0
Effect of Exit Beam Pipe
Effect of Exit Beam Pipe
Distance from center of beamcal (mm)
Distance from center of beamcal (mm)
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Energy Deposition versus r and f

F150.0
F180.0
150.0
180.0
Effect of Entrance Beam Pipe
Effect of Entrance Beam Pipe
Distance from center of beamcal (mm)
Distance from center of beamcal (mm)
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sensors
Within a radius of 25mm no clustering
Full detector
Full Detector with clustering
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Fraction of Energy Observed within a Radius of
0.5 cm of Electron Path

No clustering cuts
With clustering cuts
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Fraction of Energy Observed within a Radius of
1.0 cm of Electron Path

No clustering cuts
With clustering cuts
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Fraction of Energy Observed within a Radius of
2.0 cm of Electron Path
With clustering cuts
No clustering cuts
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Fraction of Energy Observed within a Radius of
3.0 cm of Electron Path

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• Energy Resolution of High Energy Electrons

E(measured)- E(expected) /E(expected)
Best Possible Resolution No Beamstrahlung effects
included
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• Energy Resolution of High Energy Electrons

E(measured)- E(expected) /E(expected)
Energy Resolution with Beamstrahlung
Included. Average Substracted. Only energy
deposited in a 25 mm radius from maximum. Sum
energy over full Beamcal thickness. Effect of
Beamstrhalung fluctuation in resolution clearly
has an effect
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• Energy Resolution of High Energy Electrons

E(measured)- E(expected) /E(expected)
Energy Resolution. Beamstrahlung Included and
Average Substracted. Measurements from 3.0 cm in
and Including only cells with more than 10 MeV
energy deposited.
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• Energy resolution of the reconstruction of the
  electrons from 2-photon
  events including the effects of beamstrahlung
  

Preliminary results
Preliminary results
Using Bayesian Statistical Analysis
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Case of no Beamstrahlung Included in analysis
Case of Best Analysis with Beamstrahlung
Included.
Exit Beam Pipe Region
Exit Beam Pipe Region
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• Reason for Resolution Tail
  

Measured Energy loss due to cuts
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• Work to be Done
• Understand the low energy tails of the energy
  resolution
• distribution. Develop a better scan.
• What is the missing Pt distribution of 2 photon
  events given
• the resolution.
• Study the resolution of new geometries.

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• Work to be Done
• Optimize signal to Background.
• Check all our Calculations.
• Find other analysis techniques that reduce the
• beamstrahlung fluctuations and hence improve
  the
• signal resolution.
• Study the effect of this analysis on SUSY
  signal.
• Missing Pt limits.

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• Study of a Scintillator Calorimeter
• We are simulating a scintillator based
  calorimeter where the tiles
• are offset in alternate layers. We are making now
  a great deal of
  
  progress.

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? s are well separated
5 cm
100 GeV
100 GeV
p0 mostly low p
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ALCPG
Geometrical Arrangement
5 cm
Scintillator Panels
Worst separation
1.25 cm
?
?
?
?
f
?????
0 0.5 1.0 0.25 0.75
?
Best separation
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Track Following into the Calorimeter

Low momentum curlers
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Cluster Correlation with Charged Tracks Success
Probability

Energy cluster in the calorimeter associated with
a charged track interaction Success
Conclude that it is a neutral cluster Failure
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ALCPG

• The Chi-Square Structure
• µi average photon energy deposited in ith
  tile
• si standard deviation in the energy
  deposition
• Hij si sj
• ?2 S (xi µi )Hij (xj
  µj )
• where xi is the energy deposited by the
  shower being tested in the ith tile.

9
-1
i,j 1
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• We are now in the middle of trying to separate
• photon clusters by means of the chi-square
• method. Hard problem. Crucial aspect of
• pattern recognition and calorimeter resolution.

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Fitted ? direction from shower energy
distribution

Z vs R
50 GeV
20 GeV
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• Study of the Characteristics of
• Silicon Photomultipliers

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• New Silicon Photo-Detectors

Bias Voltage 40 volts
Photonique, SA Pulsar, Russia Moscow
Eng. Physics Inst.
2mm
Scintillator performance
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50
2mm scint., cosmic rays

0 lt t lt 200 nsec
20 lt t lt 70 nsec
1 photo elec.
Similar resolution
5 photo elec.
Need to Improve Resolution
8 photo elec.
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Sipm attached to the center of surface of the
scintillator tile

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New Nat. Inst. PHA
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• Special Budgetary Issue
• ILC RD in DOE (Paul Grannis) awarded us a
• 20 K late award that could not be sent to CU
• but could only be deposited at SLAC because of
• the timing.
• I request that I use these funds for BaBar work
• and be allowed to used BaBar funds deposited
• in Colorado for ILC RD work.

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• Because ILC RD funds become available in
• July the funds cover 2 years of BaBar work
• 1 year of differential housing costs for
  Nagel
• 5 K
• 1 year travel costs from Colorado to SLAC
• 5 K
• The total award from ILC RD is 53 K
  

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• The University has contributed to my research
• a total of 38 K towards support of a Research
• Associate since I have become Chair of the
• Boulder Faculty Assembly and my research time
• is now limited. I propose to use these and the
• ILC RD funds towards the Research
• Associate if DOE accepts the ILC-BaBar fund
• exchange.

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The Calorimeter

• Modules
• Each module 12 tons

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Removal of Charged Track Hits

Extrapolation of charged tracks
Charged hits removed
Track Interact
Jason Gray, Jiaxin Yu
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Pattern Recognition of Showers

Chris Geraci
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Chi Square Separation, 1st order

Sarah Moll Joseph Proulx
100 GeV p0 Odd layers
100 GeV p0 Even layers
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2 Photon Process
Very forward into BEAMCAL
e e
- -
?
q , l
in the detector
?
q , l
Very forward into BEAMCAL
e- e-
Discussion in Beam Cal section at end
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• Study the efficiency to observe
  the electron and positron of the two photon
  process above the beamstrahlung background
• Essential to remove this background in the
• study of Supersymmetry in the dynamic region
• of low Pt. Needed to measure the masses.

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Testing GEANT 4.0

Evidence for multiple scattering
air in beam pipe
No field, 50 GeV muons
No field, 50 MeVmuons
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50 MeV, solenoid on, forward
50 MeV, no field, forward

Solenoid field shrinks mult. Scat.
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Beamstrahlung Distribution with Solenoid
Anti-DiD

Beam pipes Entrance Exit
No beam pipes
Difficult region to detect 2 photon process
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• GEANT 4.0 seems to be working
• properly We have fixed various bugs
  in
• collaboration with SLAC team.
• All Simulation is work in
  progress.

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• Hardware Studies
• Keith Drake, Elliot Smith

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• Long Term Tests of Scint. Fiber Stability

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• Latest Pulse Distribution from
  
• Photonique/Russia

6 photoelectrons
10 photoelectrons
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Pulse National Inst.
.
.
.
.
.
.
3 pe
.
1 pe
8 pe
Scan every 2.5 nsec
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Our Measurements

6 photo-elec.
Blue LED, 10nsec, 2.5 volts drive
50 nsec gate
noiseless SiPD
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1st 10 nsec
2nd 10 nsec
3rd 10 nsec
4th 10 nsec
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• Cosmic Rays in a 1 cm Thick Scintillator
  

20 lt t lt 70 nsec
0 lt t lt 200 nsec
poorer resolution
1 pe
2pe
4pe
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1cm scint

10 lt t lt 20
30 lt t lt 40
40 lt t lt 50
60 lt t lt 70
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• Pulse Height versus Temperature
• Gain of SiPD Increases x4

Noisy SiPD Could not detect peaks
Room temp
-300 C
Needs to be repeated with New SiPDs noiseless
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2 mm scint

10 lt t lt 20
30 lt t lt 40
40 lt t lt 50 nsec
60 lt t lt 70 nsec
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• By time tagging we are observing the
• photons arriving in time sequence. Possibility
• to use this to improve resolution. Need beam
  tests
• to check this hypothesis.

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• Work still in progress. Comparison with
  Russian
• plots indicate 100 Mhz x 4 (measuring pulse
  height
• every 2.5 nsec) not enough resolution.
• National Instruments has just released a 2
• Gigahertz unit. Using our trick of x4 will allow
  us to
• scan every 0.125 nsec. A demo is on its way here
  to
• check whether 8 bits resolution is good enough.
  

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• Conclusions
• A new revolution in photo-detection. A lot of
• improvements still possible. A lot of work to be
• done in this area. If one is bold and reckless
  one
• may say that It may revolutionize calorimetry
• resolution.

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• Conclusions
• Our simulation work with the undergraduates is
• moving ahead. A lot of work needs to be done
• still. Need manpower help. Most of the pieces are
  
• in place to study Z and W mass resolution.

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We helped with the organization of the Linear
Collider Workshop and the various ALCPG
meetings up to but not including Vancouver