Transcript Urbana DAQ/Trig meeting

CLEO-c Detector Issues
Mats Selen
University of Illinois

The CLEO-c event environment

Subsystem Plans
 Tracking
 Calorimetry
 Particle ID
 Muon Detector
 Trigger
 DAQ

Conclusions
CLEO PAC 28/September/01 M. Selen, University of Illinois
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The CLEO-III Detector
CLEO PAC 28/September/01 M. Selen, University of Illinois
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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.
CLEO PAC 28/September/01 M. Selen, University of Illinois
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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.
CLEO PAC 28/September/01 M. Selen, University of Illinois
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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).
CLEO PAC 28/September/01 M. Selen, University of Illinois
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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)
sp/p (Si now)
sp/p (Si no r-f)
sp/p (ZD)
0.25
0.32
0.34
0.32
0.49
0.32
0.34
0.32
0.97
0.35
0.39
0.35
1.91
0.43
0.53
0.45
CLEO PAC 28/September/01 M. Selen, University of Illinois
3.76
0.67
0.89
0.71
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ZD Upgrade Plan

Low cost & quick assembly.
Use same (left over) bushings, pins & wire as
DR3.
Won’t 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.
TDC’s from spare pool and from muon
system.

Ten cell prototype has proven that design in sound
(both mechanically and electrically).
CLEO PAC 28/September/01 M. Selen, University of Illinois
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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.
CLEO PAC 28/September/01 M. Selen, University of Illinois
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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
K p p
CLEO PAC 28/September/01 M. Selen, University of Illinois
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Muon Detector


Works as in CLEO-III.
No changes needed.
CLEO PAC 28/September/01 M. Selen, University of Illinois
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Trigger

Tracking Trigger
For B = 1.5 T, the combined axial and stereo
trigger hardware is ~100% efficient for tracks
having PT > 200 MeV/c.
When B = 1.0 T, we expect to have ~100%
efficiency for tracks having PT > 133 MeV/c.
200 MeV
200 MeV
not real
Tracking Trigger Efficiency
versus 1/P(GeV) for electrons
Tracking Trigger Efficiency
versus 1/P(GeV) for hadrons
CLEO PAC 28/September/01 M. Selen, University of Illinois
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Trigger…
Calorimeter Trigger
During CLEO-III running the mode of combining
analog signals was the same as that used in CLEOII.
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.
Simulated
Efficiency

Contained
shower
Shared mode
CLEO-II mode
Threshold = 500 MeV
CLEO PAC 28/September/01 M. Selen, University of Illinois
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TILE Board Fixes to improve “Sharing Mode”:
Added a couple
of capacitors
to back of
each board
39 pF
15 pF
pin number: 8
7
6
5
4
3
2
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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 backplanes and retrofitting many of the boards to avoid
a serious problem as trigger experts leave.
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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
CLEO PAC 28/September/01 M. Selen, University of Illinois
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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 < 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 (TDC’s, for example).
Hope to augment this prior to running.
CLEO PAC 28/September/01 M. Selen, University of Illinois
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Conclusions

The CLEO-III detector is a beautiful instrument for
running at energies around 10 GeV.
It’s 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.
CLEO PAC 28/September/01 M. Selen, University of Illinois
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