Transcript Results From the Radphi LGD Dan Krop 12/11/03 The Radphi Experiment Radphi Experiment Took Data in Jlab Hall B From May to July 2000 962

Results From the Radphi LGD
Dan Krop
12/11/03
The Radphi Experiment
Radphi Experiment Took Data in Jlab Hall B
From May to July 2000
962 Hours Of Beam Written To Disk
700 M Triggers Recorded
Radphi was a gp->Xp Experiment
JLab End Station
40m photon
beam path
radphi
detector
location
electron beam dump
photon tagger
e- beam from
accelerator
Detector Apparatus 620 element
downstream
calorimeter
8 paddle upstream
charged particle veto
70 cm
Be target
4 inch lead shield
to protect detectors
from beam halo
target region barrel shaped
charged particle detection
and 24 element calorimeter
downstream
charged particle
detector wall
Beam Energy
Radphi is a low energy/large angle experiment
Electron beam energy was 5.65 GeV
Brehmsstrahlung photons were from 75% to
95% of electron energy - 4.24 GeV to 5.37
GeV
Photon Angles
LGD
was ~ 1 m
downstream from
target
many large angle
events

Run Environment
Radphi situated behind CLAS
Material around the beam from interactions with
upstream apparatus
Beam not as well collimated as Hall D will be
Brehmstrahlung angle ~
m
E
Even with the EM background, the LGD performed
well.
Lead Glass Detector
light collection by
Russian FEU-84-3
phototubes
powered by
custom CockroftWalton bases
Glass recycled
from BNL E852
620 lead glass blocks
4x4x45 cm
15 radiation lengths
8cm diameter
beam hole
subtends angles out to
27 degrees from the
beam direction
2 Photon Events
3 Photon Events
4 Photon Events
LGD Energy Resolution
• Combined Resolution
Study on Single h & p
• Includes spatial terms
E
7.3%
 3.6% 
E
E
2
 0.64 
2
  
   X 0 sin   cm
 E 
0.64
  
cm
E
Conclusions
Pb/Glass Calorimetry is possible in noisy
brehmsstrahlung environment
LGD key component in L2 and L3 trigger
Identification of exclusive final states
With run conditions worse than GlueX will
have, Radphi was still able to get good
calorimeter performance
Backup Slides
Three Level Trigger
(tagger-BSD
coincidence)
Rate=600k/s
Basic
interaction
trigger
Level 1
(tagger-BSD
coincidence+
not busy)
Level 2
(any LGD
channel above
a threshold)
Level 3
(digitized
energy sum)
rate:
274,000 Hz
pass rate:
8000 Hz
pass rate:
350 Hz
1.2 s
dead time
8-12 s
dead time
32% dead time
contribution
8% dead time
contribution
L2 modules designed and built
at IU for radphi
L3 module designed and built
At IU for E852