QUARTIC, A TOF for ATLAS/CMS Forward Protons

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QUARTIC, A TOF for ATLAS/CMS Forward Protons
Andrew Brandt (UTA) Jim Pinfold (Alberta), Mike
Albrow (FNAL)

• You didnt know that ATLASCMS had forward
  protons?
• FP420 Forward Protons 420m downstream of CMS
  ATLAS (joint RD project)
• Physics is
• p H/WW/ZZ
  p
• Measure ps with very high precision within 3 mm
  of beam
• Gives mass and quantum numbers of central state.

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FP420 Challenges

• ? Tracker, perhaps 10 layers per station, 3
  stations, 3D silicon
• (edgeless, 10um res., fast, rad hard) ....
  Hawaii/SLAC Brunel
• TOF counter, quartz fiber Cerenkov MCP-PMTs
• Vacuum mechanics
• Detectors in secondary vacuum, space
  constraints
• between beam pipes, not room for roman pots.
• High precision movement (microns),
  reproducibility,
• fail-safe.
• Funding, approvals, etc.

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Cerenkov Effect
n1
ngtgt1
Use this property of prompt radiation to develop
a fast timing counter
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Cant put our PMT in 7 TeV beam!
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QUARTIC
Preliminary UTA drawing of Mike Albrows concept
for a fast time resolution Cerenkov counter
Initial design used 2 mm2 rods, but not enough
light, this drawing shows 6mm2 rods
proton
?z (mm) 0.21 ?t (psec) (2.1 mm for ?t10 psec)
zc(TR-TL)/2
Microchannel plate PMT
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Where do Protons go at 420m
120 GeV Higgs courtesy Peter Bussey, Manchester
(irony of particle physicseasier to get plot of
protons from Higgs than single diffraction)
y
xlt2.5 cm
?3mm
x
x
x
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GEANT4 Simulation (Alberta)

• A GEANT4 simulation is well underway (see GEANT4
  produced graphics above.
• The detector simulation includes
• Tracking of Cerenkov photons to the MCP-PMT
  through the medium.
• Wavelength dependent refractive index of the
  medium
• Wavelength dependent attenuation of the photons
• Wavelength dependent reflectivity of the
  aluminium reflector
• Timing of photons from generation to the MCP-PMT
• The effects of coupling grease (if necessary)

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QUARTIC Background Rejection (UTA)

• 2 single diffractive protons overlayed with a
  hard scatter (1 of
• interactions have a proton at 420m)

97.4 of events primary vertex and fake vertex
from combining proton times more than 2.1mm (1?)
apart 94.8 if 20 psec
2) double pomeron overlayed with a hard scatter
97.8 of time vertices more than 2.1mm apart
95.6 if 20 psec
3) hard SD overlayed with a soft SD
95.5 of time primary vertex and fake vertex more
than 2.1mm apart 91.0 if 20 psec
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Cerenkov Light in Fused Silica (UTA)
? PE QE pQ E Tc n
180-250 1652.6 15.70 259.5 49.6 1.544
250-350 1148.7 18.00 206.8 47.8 1.490
350-450 624.7 19.90 124.3 47.2 1.471
450-550 394.3 11 43.4 46.9 1.464
550-650 271.1 1.50 4.1 46.7 1.458
total 638.0

P ave ?c ave L Q E ave P.aveQE ave
4161.6 48.8 3.99cm 15.57 648.0
UV is important! 640-650 total pes 130
pe/6mm rod
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Preliminary Time Distributions
Single ? n1.52 ?c49? 7.4 of pes in 10
psec 21.3 in 50 psec
red totally internally reflected light green
extra light if aluminized
0.01

• over ? including QE
• 1.9 of pes in 10 psec
• 19.1 in 50 psec

0.01
50 psec
50 psec
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Next Steps

• Preliminary design studies are promising
• Need to learn more about MCPs preliminary
  indications are Burle tubes are currently only
  option due to size of active area
• Burle 85021 600 has 1.5 mm pixels could give very
  useful
• x-segmentation for measuring multiple
  protons in same detector, but it seems that best
  timing using single MCP_OUT channel (1/tube)
  (Wilma Raso)
• Starting to think about electronics (Alberta)
• Test beam at Fermilab summer 2006