2 July 2004Journée DPNC 2004 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 July 2004Journée DPNC 2004 Goal of the experiment Balandin et al. (1974) Bardin et al. (1984) Giovanetti et al. (1984) the uncertainty on   is the dominant contribution to the uncertainty on G F : FAST goal: 0.07 ppm (PDG 2002) 0.5 ppm (Van Ritbergen and Stuart ) ≤12 ppm (PDG 2002) 9 ppm

2 July 2004Journée DPNC 2004 Description of the experiment 1 pixel = 0.4 x 0.4 x 20 cm x 19.2 x 20.0 cm 3 32 x 48 pixels = 1536 pixels 8 x 12 = 96 groups of 16 bars DC pion beam p = 170 MeV/c at PSI - pM1 area ++          ~ 26 ns      e   e   ~ 2.2  s PSPM x 96 Target and optoelectronics readout Preamp Discri x 96 Analogue electronics LV2 board TDC LL - data HL - data x 16 Digital electronics Dual threshold discriminators: - low thr: mip’s - high thr: stopping pcls

2 July 2004Journée DPNC ppm requirement Ability to disentangle overlapping events Tracking capabilities and high granularity of the target Very high data rate Constraints on the DAQ FAST DAQ design  80 MB/sec + ONLINE ANALYSIS !!! High beam rate, because PARALLELISATION is needed! ~ 1 MHz (2-3 months data taking) Sample of events needed (  +   +  e + ) Suppression of systematic effects at the ppm level Remove time dependent effects that, together with asymmetries in the target, could compromise the measurement DC beam Isotropic muon source (by the identification of  +   + decay)  SR effects suppression

2 July 2004Journée DPNC 2004 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: LV2 trigger idea: all the relevant time informations are contained in the “superpixel” (5x5 pixels) centered on the stopping  no need to read 16 TDC’s always at the same time – but only the TDC’s containing at least one pixel of the superpixel  DATA REDUCTION LV2 trigger task: find the stopping  coordinates search for the subsequent  trigger only the interested TDC’s flag the event if another  is found in the superpixel (LV2 trigger input = HL data from discriminators)   beam

2 July 2004Journée DPNC 2004 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

2 July 2004Journée DPNC Activities: Target completed + assembling at PSI  80/96 tubes available  Complete readout and DAQ chain  No LV2 trigger available DAQ chain tested  75 MB/sec Fine tuning of the detector and beam (High Voltages, Thresholds, Ranges, Timing properties)  Some problems found  Some improvements needed Few days of data taking, LV2 trigger prototype tested Beam time: Sept – Dec 2003

2 July 2004Journée DPNC beam test : fine tuning HV efficiency curves for each tube range of beam  (and  ) in the target with variable thickness absorber Preliminary beam tuning (  stopping points distribution) beam Blind in the vertical (z) direction beam profile ! ! ! x y

2 July 2004Journée DPNC tubes, 2000 commissioning 60 tubes, 2002 commissioning 2003 beam test : timing properties Time resolution monitored using straight tracks  t ~ 1 ns stable with time 50 ns mismatch prempl/discr Afterpulses structure in old commissioned tubes replaced 20 old tubes impedance mismatch cured: - preamp modified - replaced preamp / dicrim cables

2 July 2004Journée DPNC beam test: Muon lifetime few days run (‘long run’) total statistics : events from online analysis (10% written to disk for offline studies) Run conditions: - narrow  trigger - no LV2 trigger (  all 16 TDC’s) - low LV1 (beam) trigger rate Good background suppression Good exponential fit: - in agreement with PDG value, within a bigger error:   PDG ~ 40 ps;   2003 ~ 350 ps

2 July 2004Journée DPNC 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   PDG = ns   2003 = ns Preliminary result… but feasible measurement !!!

2 July 2004Journée DPNC 2004 What’s 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

2 July 2004Journée DPNC 2004 Near future improvements Permanent magnet ~ 80 G to suppress residual  SR effects: B = 80 G forces  ‘s to precess on a known time scale ( ~ 1  s) 1.Suppress beam  ’s 2.Measure vertical beam profile 3.Measure  as a function of the z position in the target Hodoscope Z-counter z y x

2 July 2004Journée DPNC 2004 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