1. Muon g-2 and SLAC Detector Test T-519 Momentu m Spin e David Hertzog University of Washington

2.  a Subset of g-2 Collaboration* 2/20 *38 Institutes, 150 members At SLAC

3. Three sigma is not enough to claim a discovery BNL E821 2012 e + e - Thy 3.6  x10 -11 Future Goals Goal: 140 ppb Expected Improvement Expect to turn on in late 2016 a P5 priority

4. 4 Ring moved to FNAL and Magnet being assembled g-2

5. Why SLAC is important We measure muon decay to electrons 0 – 3.1 GeV Detectors must measure Energy and its Time and we must optimize them e+e+ Calorimeter Electronics Events above threshold Software threshold 5

6. Read out by SiPMs (pixelated avalanche photodiodes run in Geiger mode) Compact, non-magnetic calorimeters made of 54 Lead-Fluoride Cherenkov Crystals

7. 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

8. July 2014: T-519 Test 4x7 array of PbF2 crystals with SiPM readout using 2.2 – 4.5 GeV beam 8

9. 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  m id) –Front plate + Focusing Lens »Crystals / SiPMs Pulse shape pe from laser pulses

10. Typical beam on detector 0 1 2 3 4 5 electrons per pulse Usually Good small spot But, not always so …

11. 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”)

12. Now a selection of the good findings in what should be a publishable set of results  E/E = 2.2% 3.27 GeV 1500 pe/GeV Resolution 2.7% at 2 GeV Energy resolution exceeds our goal by a factor of 2

13. 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)

14. Gain stability very important for g-2 Measured over 8 hours: (1.0 ± 1.4) x 10 -4 / hour Data corrected by concurrent laser calibration system

15. 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