FAST: A precision measurement of muon lifetime'

1
FAST A precision measurement of muon lifetime.

• Chiara Casella
• FAST collaboration
• A.Barczyk (1) , J. Berdugo (2) , J. Casaus (2) ,
  C. Casella (3,4) , K. Deiters (4), P. Dick (4),
• A. Dijksman (4), J. Kirkby (1), L. Malgeri (1),
  C. Mana (2), J. Marin (2), G. Martinez (2),
• C. Petitjean (4), M. Pohl (3,5), E. Sanchez (2),
  C. Willmott (2)

CERN 1 , CIEMAT 2 , UNIGE 3
, PSI 4 , NIJMEGEN 5
2
Goal of the experiment

• Balandin et al. (1974)
• Bardin et al. (1984)
• Giovanetti et al. (1984)

• the uncertainty on tm is the dominant
  contribution to the uncertainty on GF

• FAST goal

3
Description of the experiment
1 pixel 0.4 x 0.4 x 20 cm3 12.8 x 19.2 x 20.0
cm3 32 x 48 pixels 1536 pixels 8 x 12 96
groups of 16 bars
p
DC pion beam p 170 MeV/c at PSI - pM1 area
p ? mnm tp 26 ns m ? enmne tm 2.2 ms
4
1ppm requirement
5
Level 2 trigger (i.e. data reduction)
Max data rate sustainable by DAQ ? 80
MB/sec (Simulated) Raw data rate from the target
? 2300 MB/sec
Trigger system (level 2 trigger) to reduce data
bandwidth
6
Level 2 trigger

• Level 2 trigger the only hardware missing
  element
• CIEMAT Madrid in charge of it
• Prototype tests performed
• Single board (1/16) prototype tested - Dec 2003
• Prototype (1/4) tested - June 2004
• Prototype (1/4) test ? - July 2004 (?)
• Final level 2 commissioning end 2004

7
2003 Activities

• Target completed assembling at PSI
• 80/96 tubes available
• Complete readout and DAQ chain
• No LV2 trigger available

Beam time Sept Dec 2003
8
2003 beam test fine tuning
HV efficiency curves for each tube
Preliminary beam tuning (p stopping points
distribution)
Blind in the vertical (z) direction beam
profile ! ! !
beam
range of beam p (and m) in the target with
variable thickness absorber
y
x
9
2003 beam test timing properties
Time resolution monitored using straight tracks
st 1 ns stable with time
10
2003 beam test Muon lifetime

• few days run (long run)
• total statistics 7.4 107 events from online
  analysis
• (10 written to disk for offline studies)
• Run conditions
• - narrow p trigger
• - no LV2 trigger (? all 16 TDCs)
• - low LV1 (beam) trigger rate
• Good background suppression
• Good exponential fit
• - in agreement with PDG value,
• within a bigger error
• st PDG 40 ps
• st 2003 350 ps

11
2003 beam test Pion lifetime

• Unexpected result from HL run
• Pion lifetime not primary FAST goal
• Short dedicated high threshold run
• Good exponential fit, in agreement
• with PDG value
• st PDG 0.005 ns
• st 2003 0.024 ns
• Preliminary result
• but feasible measurement !!!

12
Whats going on now

• 20 old tubes replaced, 16 new tubes in place
• Preamplifiers modified, impedance mismatch cured
• ? Re-tuning of the target
• New DAQ version (faster!)
• Improvements in the target
• Magnetic field
• Z-counter

13
Near future improvements
14
Conclusions and future plans

• FAST is a small dimension experiment!
• 2003 testbeam successful test
• - Understanding of the detector
• - Readout and DAQ chain performances
• - Preliminary (and encouraging) results!
• 2004 beam time (? 6 August)
• magnet
• Z-counter
• End 2004
• Level 2 trigger ? First FAST data taking run