Test T-519 Momentum Spin e David Hertzog University of Washington
Dec 31, 2015
Muon g-2 and SLAC Detector TestT-519
Momentum
Spin
e
David HertzogUniversity of Washington
wa Subset of g-2 Collaboration*
2/20
University of Washington
Cornell
University of Kentucky
University Illinois
University of VirginiaJames Madison
Shanghai Jiao Tong
*38 Institutes, 150 members
Frascati
Naples
Trieste
Pisa
Roma II
Udine
At SLAC
Three sigma is not enough to claim a discovery
BNL E821
2012 e+e- Thy
3.6 s
x10-11
Future Goals
Goal: 140 ppb
Expected Improvement
Expect to turn on in late 2016
a P5 priority
4
Ring moved to FNAL and Magnet being assembled
g-2
Why SLAC is importantWe measure muon decay to electrons 0 – 3.1 GeVDetectors must measure Energy and its Time and we must optimize them
e+
Calorimeter
Electronics
Events above threshold
Software threshold
5
Muon g-2
• Read out by SiPMs• (pixelated avalanche photodiodes run in Geiger mode)
Compact, non-magnetic calorimeters made of 54 Lead-Fluoride Cherenkov Crystals
Muon g-2
Last November: SLAC T-512
7
• 2.5 – 4 GeV e-
• SiPMs (cooled), augmented by PMTs on sides
• Digitizers for pulse shapes
3.5 GeV
Linearity
Measured resolution with limited size array
Learned how to use the beam effectively
Muon g-2
July 2014: T-519 Test 4x7 array of PbF2 crystals with SiPM readout using 2.2 – 4.5 GeV beam
8
Muon g-2
Calibration System Set Absolute Gains
Tested in Seattle 2 weeks ago and also at SLAC
9
• Laser Filter Wheel 10:90 Splitter– Source Monitor (pin diode) & PMT– Sphere or Diffuser
• 4 monitors (pin diodes, PMT)• Fiber Bundle (60; 800 mm id)
– Front plate + Focusing Lens» Crystals / SiPMs
Pulse shape
pe from laser pulses
Typical beam on detector
0 1 2 3 4 5
electrons per pulse
Usually Good small spot
But, not always so …
Linearity Beam Energy Selection
There remains an ambiguity between “requested” energy and delivered energy and an independent system that can calibrate the beam true energy (i.e., not the detector under “test”)
Now a selection of the good findings in what should be a publishable set of results
dE/E = 2.2%
3.27 GeV
1500 pe/GeV
Resolution 2.7% at 2 GeVEnergy resolution exceeds our goal by a factor of 2
Position scanning using high-quality pencil-like beam and remote XY table
Horizontal Scan (no gain correction)
Comment: Only possible with steady and high-quality beam conditions(takes many hours)
Gain stability very important for g-2Measured over 8 hours: (1.0 ± 1.4) x 10-4 / hour
Data corrected by concurrent laser calibration system
Summary• Important for g-2• Beam setup and quality critical• Great results to far
• Hope to come again with complete calorimeter and all onboard electronics and DAQ. Possibly also Straw Tracker system
• Thanks