MEG Overview

1
MEG Overview

• Cobra (W. Ootani)
• LXe calorimeter (S. Mihara)
• Calibrations (G. Signorelli)
• Drift Chambers (J. Egger)
• Timing counter (F. Gatti)
• Electronics and DAQ (M. Grassi)
• Software (R. Sawada)
• Schedule

2
Quench Problem Status (W. Ootani)

• The shielding and grounding scheme was improved
  after the December run.
• There hasnt been no unexpected shutdown since
  then.
• No shutdown for 10 days with SCNCBypass during
  shutdown period.
• No shutdown for 10 days with SC (BTS) after
  accelerator started to run.
• The problem by the external noise seems fixed.

A new problem happened during CW accelerator
testing. COBRA was unexpectedly shutdown after
40 hrs operation. Still under investigation, but
it seems there was a problem with NC power supply
according to the measured waveform.
3
Xenon detector (S. Mihara)Honeycomb panel test
completed

• 3rd panel delivered to Pisa at 1630 on 20/Feb
• Mounted on the text box and tested on 22, 23/Feb
• 3 bar
• Inspection by a Plyform expert
• 4 bar x4 times
• Hold for 3 minutes at 4 bar in the last test
• Panel deformation (max)
• 0.3 mm at 1 bar
• 3.4 mm at 4 bar

Holes for evacuation
4
Cryogenic Test at SIMIC

• -18/May
• All nuts on the covers of the cold vessel were
  fastened tightly and the warm vessel was
  evacuated whole weekend.
• 21/May
• He leak test. 1.8Bar He was filled and found that
  the leak rate was larger than 10-4 mbarl/sec.
  Keep evacuation during the night.
• 22/May
• cooling using cold gas from the LN2 tank. Cold
  gas in the cold vessel Most parts were cooled
  down to -5-10 degree C.
• 23/May
• liquid N2 through the cooling pipe. All parts
  cooled below -110 degreeC around 1200.
• Then N2 gas at 1.0Bar and He gas filled step by
  step with measuring leak rate.
• N2 1.0 bar He 0.2 bar ? 5x10-7 mbarl/sec
• N2 1.0 bar He 0.4 bar ? 1.6x10-6mbarl/sec
• N2 1.0 bar He 0.6 bar ? 7.8x10-6mbarl/sec
• N2 1.0 bar He 0.8 bar ? 2.2x10-5mbarl/sec
• The leak was not fixed at SIMIC by any means.
• We decided to bring the cryostat to PSI and
  perform a leak test

5
Cryostat arrived at PSI

• Delivery at 700 am on 5/June
• Works to be done
• Cleaning
• Leak/pressure test
• Alignment
• PMT installation

6
CW received on middle of may(G. Signorelli)
7
(No Transcript)
8
m radiative decay
LED
Laser
Lower beam intensity lt 107 Is necessary to reduce
pile-ups Better st, makes it possible to take
data with higher beam intensity A few days 1
week to get enough statistics
g
e
m
(rough) relative timing calib. lt 23 nsec
n
n
PMT Gain Higher V with light att. Can be repeated
frequently
p0? gg
p- p ? p0 n p0 ? gg (55MeV, 83MeV) p- p ?
g n (129MeV) 10 days to scan all volume
precisely (faster scan possible with less
points) LH2 target
alpha
Xenon Calibration
PMT QE Att. L Cold GXe LXe
e
g
e-
Nickel g Generator
Proton Acc
Li(p,?)Be LiF target at COBRA center 17.6MeV
g daily calib. Can be used also for initial
setup
9 MeV Nickel ?-line
on
off
quelle
K
NaI
Bi
Illuminate Xe from the back Source (Cf)
transferred by comp air ? on/off
Tl
Li(p, ?1) at 14.6 MeV
F
Polyethylene
0.25 cm Nickel plate
Li(p, ?0) at 17.6 MeV
9
DC (J. Egger)
10

• 4 Levels of test
• Pretest HV Air tightness
• Aquarium functionality tightness
• Cosmics Lab other preamps correct signal
  assignment inside COBRA up to panel
• Cosmics pE5, with and without COBRA

11
DC test with Cosmic ray (in Lab.)
12
cosmic ray counter for DC wire alignment

• 10 counters (10 plastic scintillators 20 PMTs)
  are prepared
• DC wire alignment will be performed w/o COBRA
  field

13
TC F. Gatti
14
TC MC vs data E loss in bars

15
6 years of operation !!
16
(No Transcript)
17
(No Transcript)
18
Positron efficiency
Confirmed by a 3 calculation including PR,
tracking and fitting from DC to TC
19
missing hits
missing hits
Positrons from off-centre m-decays and hitting
DCH outer frame
20
Where do they come from?

• Front view (x-y) of
• m-decay vertices on
• the target
• all events
• c2gt50 N1lt5
• Source of inefficiency
• for the TC

21
Way(s) out?

• Reduction of beam spot size on the target?
• (sx,y ? 1.1 cm ? 0.5 cm)
• is it achievable by shrinking the target (not
  this year)
• Background ? Investigate...
• Increase of the magnetic field?
• shrinking of the bending radius by ? 1 cm needed
• increase of B by ? 7 (B0 1.26 T ? 1.35 T)
• distortion of hit pattern on TC?
• might it affect COBRA behaviour?
• ...

22
Multi-threading model
Electronics and DAQ M. Grassi
Calibration Thread
Zero-copy ring buffers
VME
Round-Robin distribution
Calibration Thread
VME Transfer Thread
Collector Thread
Calibration Thread
Network
Calibration Thread
23
DRS Readout rate

• Optimal readout rate of DRS full waveforms with 4
  calibration threads 30 events/s
• During Dec 06 run max readout at 7 events/s
• Double event readout
• Code optimization
• Single calibration thread

24
DAQ rate vs. amount of data

• DAQ speed is not a limiting factor
• The total data size needs solution
• 30 Hz is maximal VME speed for full waveforms ?
  gt270 MB/sec
• Data transmission limit is 20 MB/sec
  (250TB/year)? need online reduction 10x (M.
  Grassis and R. Sawadas talk)
• Storage limit is 30 TB/year? need offline
  reduction 8x (R. Sawadas talk)

25
Conclusions

• Splitters installed, operational, expected
  performances, test in Dec 06
• Fiber preamp problem with an IC fixed, test
  passed, mounted on the TC detector, installation
  in Aug 07
• Hit registers mezzanine boards produced, FPGA
  firmware ready (PSI GPVME board), installation in
  Aug 07
• Trigger installed, operational, built-in
  debugging and control tool, need tuning after
  detector turn on, test in Dec 06
• DRS2 installed, operational, good for timing,
  temperature dependence, usable with DC
• DRS3 prototype test phase, final solution, not
  available in 2007
• Aux digitizer production problem solved,
  prototype test completed successfully, ready for
  2007 run
• DAQ installed, operational, good performances,
  test in Dec 06 run
• The electronics and the DAQ systems are expected
  to be ready for the 2007 run

26
Software (R. Sawada)
27
(No Transcript)
28
Pdfs 1)
g
e
Signal
Signal
RD
Accidental
FWHM 0.8
RD
FWHM 5
Accidental
All pdfs normalized to 1 and summed by relative
weights of different types of events. Positron
FWHM improved from 1.0 ? 0.8 photon FWHM
improved from 6.5 ? 5 .
29
Pdfs - 2)
Signal
Dq
Dt
Signal RD
RD
FWHM ? 1o
FWHM 180 ps
Accidental (assumed flat in cos q)
Accidental (assumed flat)
Dt assumed flat for accidental and gaussian for
signal/RD (MC results predict gaussian shape,
but with worse resolution) Dq taken from MC
(results close to the proposal FWHM).
30
Sensitivity result

• Three different sets of windows results do not
  depend on the cuts.
• The sensitivity limit is
• 2.15 x 10-13
• equivalent to the sensitivity that one
  obtains with a box
• analysis assuming ? 0 bck.
• (not surprising).
• Important point the spill-in
• of bck events within the signal region is
  automatically
• taken into account by the
• knowledge of the bck pdf.

2.15 x 10-13
N.B. Empty circles crosses shifted by 0.05 on
B.R. axis for clarity.
of null experiment
31
Advantage boundary effect
0 events in box analysis
Box analysis window
Likelihood analysis window
1 event in box analysis
Box analysis window
Likelihood analysis window
Box analysis quote a worse upper limit, with a
sudden jump. Likelihood analysis treated as
a bck fluctuation, likelihood value only
slightly changed ? upper limit increases by a
small amount and continuously.
32
Conclusions
First result very good agreement of rates
predicted by MC ? no significant unwanted
backgrounds !!
33
Schedule
34
(No Transcript)