The CLEO-c event environment

1
CLEO-c Detector Issues
Mats SelenUniversity of Illinois

• The CLEO-c event environment
• Subsystem Plans
• Tracking
• Calorimetry
• Particle ID
• Muon Detector
• Trigger
• DAQ
• Conclusions

2
The CLEO-III Detector
3
Event Environment

• Details depend on energy, although generally
  speaking
• Multiplicities will be lower (about half).
• Tracks showers will be softer.
  
• Physics cross-sections will be higher.
• 500 nb at the ? (includes Bhabhas)
• 1000 nb at the J/? (just resonance)
• Relative backgrounds rates will be lower.

4
Tracking System

• CLEO-III drift chamber (DR3) is very well suited
  to running at lower energies.
• We will probably lower the detector solenoid
  field from 1.5 T to 1.0 T.
• This will shift the PT for a given curvature down
  by the same factor.
• The silicon detector presents two problems.
• It represents a lot of material
• 1.6 X0 in several scattering layers.
• CLEO-c momentum resolution as already
  multiple-scattering dominated(crossover momentum
  is 1.5 GeV/c).
• It seems to be dying from radiation damage.
• Performance is degrading fast.

5
ZD Upgrade Plan

• Replace the 4-layers of silicon with an inner
  drift chamber (dubbed the ZD).
• Six layers.
• 10mm cells
• 300 sense wires.
• All stereo (10.3o 15.4o).

6
ZD Upgrade Plan

• Low mass is optimally distributed.
• 1.2 X0, of which only 0.1 X0 is in the active
  tracking volume.
• With DR3, this will provide better momentum
  resolution than silicon.

P (GeV/c) 0.25 0.49 0.97 1.91 3.76
sp/p (Si now) 0.32 0.32 0.35 0.43 0.67
sp/p (Si no r-f) 0.34 0.34 0.39 0.53 0.89
sp/p (ZD) 0.32 0.32 0.35 0.45 0.71
7
ZD Upgrade Plan

• Low cost quick assembly.
• Use same (left over) bushings, pins wire as
  DR3.
• Wont have to hire stringers (only 300 cells).
• Fabrication will be complete by late summer
  2002.
• Will use existing readout electronics.
• Preamps build from existing parts PCBs.
• Eight 48-channel data-boards from slightly
  modified existing spares.
• TDCs from spare pool and from muon system.
• Ten cell prototype has proven that design in
  sound (both mechanically and electrically).

8
Calorimeter

• Very well suited for CLEO-c operation.
• Barrel calorimeter functioning as well as ever.
• New DR3 endplates have improved the calorimeter
  end-cap significantly (now basically as good as
  the barrel).
• The good coverage now extends to 93 of 4p.
• Large acceptance key for partial wave analyses
  and radiative decays studies.
• No changes needed.

9
Particle-ID

• RICH works beautifully!
• Complemented by excellent dE/dx.
• Will provide virtually perfect K-p separation
  over entire CLEO-c momentum range.
• No changes needed.

RICH
dE/dx
p
p
K
10
Muon Detector

• Works as in CLEO-III.
• No changes needed.

11
Trigger

• Tracking Trigger
• For B 1.5 T, the combined axial and stereo
  trigger hardware is 100 efficient for tracks
  having PT gt 200 MeV/c.
• When B 1.0 T, we expect to have 100
  efficiency for tracks having PT gt 133 MeV/c.

not real
200 MeV
200 MeV
Tracking Trigger Efficiency versus 1/P(GeV) for
hadrons
Tracking Trigger Efficiency versus 1/P(GeV) for
electrons
12
Trigger

• Calorimeter Trigger
• During CLEO-III running the mode of combining
  analog signals was the same as that used in
  CLEO-II.
• The trigger was designed to operate in a more
  efficient shared mode, but this was not
  implemented due to relative timing uncertainties
  between shared signals.
• This problem was addressed during the shutdown,
  and shared mode running will hopefully be
  implemented soon after turning back on.

13
TILE Board Fixes to improve Sharing Mode
Added a coupleof capacitors to back of each
board
14
Trigger

• Global Level-1
• Flexible enough to design almost any needed
  trigger lines.
• Rate is not an issue (trigger processing is
  effectively dead-time-less).
• Spares Maintenance
• The spare situation is not ideal
• Only a few spares of each kind
• In particular, our 6 TPRO boards seem to be quite
  fragile and we only have 2 spares.
• The Hard metric connectors on most of our boards
  require a very trained hand to swap a board
  without bending pins.
• Hard metric connector technology has improved
  since we designed the trigger, and we are
  considering the task of rebuilding several
  back-planes and retrofitting many of the boards
  to avoid a serious problem as trigger experts
  leave.

15
Data Acquisition System

• Achieved Performance
• Readout Rate 150 Hz (prior test) 300 Hz
  (expected now) 500 Hz (random trigger)
• Average Event Size 25 kBytes
• Data Transfer Rate 6 Mbytes/sec
• Low dead-time

Trigger Rate 100 Hz
16
Data Acquisition System

• The biggest challenge will be running on the J/?
  resonance where the effective cross-section is
  1mb.
• Physics Rate 100-200 Hz if L 1-2x1032
  cm-2s-1 and DEbeam 1 MeV.
• We can handle 300 Hz.
• With ZD replacing Silicon, the event size could
  be reduced significantly.
• Under almost any assumption, average throughput
  to tape will be lt 6 Mbyte/s, which is compatible
  with current online system.
• Although not anticipated, if necessary there are
  several straight-forward incremental upgrade
  paths.
• Gigabit switch (already bought).
• Faster online computer.
• One potential vulnerability is the shortage of
  spare readout components (TDCs, for example).
• Hope to augment this prior to running.

17
Conclusions

• The CLEO-III detector is a beautiful instrument
  for running at energies around 10 GeV.
• Its performance speaks for itself.
• CLEO-c is a small perturbation of CLEO-III.
• Apart from machining the end-plates, the whole ZD
  upgrade will be done in house using existing
  parts.
• All other detector components are OK as is.
• We are convinced that CLEO-c will be a beautiful
  instrument for studying charm and resonance
  physics in the 3-5 GeV regime.
• Excellent tracking covers 93 of 4p.
• Excellent calorimeter covers 93 of 4p.
• RICH provides superb particle ID for 80 of 4p.
• Fully capable trigger DAQ.
• Best device to ever accumulate data in this
  energy range.