Dec. 8th, 2000NOON 20001 A new e experiment at PSI For the MUEGAMMA collaboration Stefan Ritt...
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Transcript of Dec. 8th, 2000NOON 20001 A new e experiment at PSI For the MUEGAMMA collaboration Stefan Ritt...
Dec. 8th, 2000 NOON 2000 1
A new e experiment at PSI
For the MUEGAMMA collaborationStefan Ritt
(Paul Scherrer Institute, Switzerland)
• Introduction
• Experimental Technique
• Current status
Dec. 8th, 2000 NOON 2000 2
Physics Motivation• SUSY theories generically predict LFV• LFV forbidden by Standard Model• Processes like + e+ are not “contaminated” by SM
processes and therefore very clean• Discovered oscillations are expected to enhance LFV
rate• The search for + e+ is therefore a promising field to
find physics beyond the SM
Dec. 8th, 2000 NOON 2000 3
Prediction from SUSY SU(5)
This experiment
Current experimental bound 2)
ft(M)=2.4 >0 Ml=50GeV 1)
1) J. Hisano et al., Phys. Lett. B391 (1997) 3412) MEGA collaboration, hep-ex/9905013
Dec. 8th, 2000 NOON 2000 4
10
J ust so
(GeV)M R2
141312101010
bound
Experimental
-1-2-3 11010
MSW small angle
MSW large anglesmall mass
J ust so
MSW large angle
sin 22
m
2(e
V )2
e
)
Br(
10
10
10
10
10
10
10
10
-3
-4
-5
-6
-7
-8
-9
-10
10
-11
10
10
10
10
10
10
-10
-11
-12
-13
-14
-15
MSW
larg
e an
gle
MSW
small a
ngle
~ larg
e an
gle sm
all m
ass
Connection with oscillations1)
1) J. Hisano and D. Nomura, Phys. Rev. D59 (1999) 116005
2) MEGA collaboration, hep-ex/9905013
2)
This experiment
Dec. 8th, 2000 NOON 2000 5
Previous + e+ Experiments
Place Year Upper limit Author
SIN (PSI), Switzerland 1977 < 1.0 10-9 A. Van der Schaaf et al.
TRIUMF, Canada 1977 < 3.6 10-9 P. Depommier et al.
LANL, USA 1979< 1.7 10-10
W.W. Kinnison et al.
LANL, USA 1986 < 4.9 10-11 R.D. Bolton et al.
LANL, USA 1999 < 1.2 10-11 MEGA Collab., M.L. Brooks et al.
• New experiment: 10-14 at PSI• Letter of Intend 1998• Proposal 1999, approved May 1999
• New experiment: 10-14 at PSI• Letter of Intend 1998• Proposal 1999, approved May 1999
Dec. 8th, 2000 NOON 2000 6
MEG Collaboration
Institute Country Main Resp. Head Scientists Students
ICEPP, Univ. of Tokyo Japan LXe Calorimeter T. Mori 12 2
Waseda University Japan Cryogenics T. Doke 5 2
INFN, Pisa Italye+ counter, trigger, M.C.
C. Bemporad 4 3
IPNS, KEK, Tsukuba JapanSupercoducting Solenoid
A. Maki 5 -
PSI SwitzerlandDrift Chamber, Beamline, DAQ
S. Ritt 4 -
BINP, Novosibirsk RussiaLXe Tests and Purification
B. Khazin 4 -
Nagoya University Japan Cryogenics K. Masuda 1 -
35 7
Dec. 8th, 2000 NOON 2000 7
Experimental Method
1m
e+
Liq. Xe Scintilla tionDetector
Drift Chamber
Liq. Xe Scintilla tionDetector
e+
Tim ing Counter
Stopping TargetThin S uperconducting Coil
M uon Beam
Drift Chamber
• Stopped beam of 108 s-1, 100% duty factor
• Liquid Xe calorimeter
for detection
• Solenoidal magnetic spectrometer with gradient field
• Radial drift chambers for e+ momentum determination
• Timing counter for e+
• Stopped beam of 108 s-1, 100% duty factor
• Liquid Xe calorimeter
for detection
• Solenoidal magnetic spectrometer with gradient field
• Radial drift chambers for e+ momentum determination
• Timing counter for e+
Ee = 52.8 MeV
Kinematics e= 180°
Eg = 52.8 MeV
e
Dec. 8th, 2000 NOON 2000 8
Signal and Background• + e+ signal very clear
– E = Ee+ = 52.8 MeV
– e+ = 180°
– e+ and in time
• Background– Radiative + decays– Accidental overlap
• Detector Requirements– Excellent energy resolution– Excellent timing resolution– Good angular resolution
e
e
e
e
e
e
e
Dec. 8th, 2000 NOON 2000 9
e Signature
eEe,E = 52.8MeV
eEe,E < 52.8MeV
0.9
0.92
0.94
0.96
0.98
1
1.02
0.9 0.92 0.94 0.96 0.98 1 1.02X
Y
10 14 Decays in Acceptance
X = Ee/52.8MeV
Y =
E/
52.8
MeV
Dec. 8th, 2000 NOON 2000 10
Sensitivity and Background Rate
BR(e) = (N • T • /4 • e • • sel )-1 = 0.94 10-14
N 1108
T 2.2 107 s (~50 weeks)
/4 0.09
e 0.95
0.7
sel 0.8
FWHM
Ee 0.7%
E 1.4%
e 12 mrad
te 150 ps
Prompt Background Bpr 10-17
Accidental Background Bacc Ee • te • (E)2 • (e)2 5 10-15
Dec. 8th, 2000 NOON 2000 11
Paul Scherrer Institute
ExperimentalHall
Dec. 8th, 2000 NOON 2000 12
Experimental Hall
Dec. 8th, 2000 NOON 2000 13
Sindrum II @ PSI
-Ti e-Ti :
Oct. 2000 (50d) beam time:
90% C.L. limit: 6.1• 10-13
Bue=4 •10-12Bue=4 •10-12
Dec. 8th, 2000 NOON 2000 14
E5 Beam Line
e
U-versionE52
Z-versionE51
AST
First Degrader
Beam transport
ASC
Detector
solenoid
• 108 /s on 55 mm2
• Neutron background measured in 1998• Beam test planned in Spring 2001
• 108 /s on 55 mm2
• Neutron background measured in 1998• Beam test planned in Spring 2001
Dec. 8th, 2000 NOON 2000 15
Detector
1m
e+
Liq. Xe Scin tilla tionDetector
Drift Cham ber
Liq. Xe Scin tilla tionDetector
e+
Tim ing Counter
Stopping TargetThin S uperconducting Coil
M uon Beam
Drift Cham ber
Dec. 8th, 2000 NOON 2000 16
LXe Calorimeter
• ~800l liquid Xe (3t)
• ~800 PMTs immersed in LXe
• Only scintillation light detected
• Fast response (45 ns decay time)
• High light output (70% of NaI(Tl))1)
• High uniformity compared with segmented calorimeters
• High channel occupancy will be accommodated by special trigger scheme
• ~800l liquid Xe (3t)
• ~800 PMTs immersed in LXe
• Only scintillation light detected
• Fast response (45 ns decay time)
• High light output (70% of NaI(Tl))1)
• High uniformity compared with segmented calorimeters
• High channel occupancy will be accommodated by special trigger scheme
Liq. Xe
H.V.
Vacuum
for thermal insulation
Al Honeycombwindow
PMT
Refrigerator
Cooling pipe
Signals
fillerPlastic
1.5m
1) T. Doke and K. Masuda, NIM A 420 (1999) 62
Dec. 8th, 2000 NOON 2000 17
Response
3 cm
Liq. Xe
Liq. Xe
14 cm
(a)
(b)
05 10 15
2025
3035
0
10
20
30
40
50
0
2000
4000
6000
8000
10000
05
1015 20 25
3035
0
10
20
30
40
50
0
200
400
600
800
1000
1200
1400
1600
1800
52.8 MeV
52.8 MeV
• Signal is distributed over many PMTs in most cases
• Weighted mean of PMTs on the front face x ~ 4mm FWHM
• Broadness of distribution z ~ 16mm FWHM
• Timing resolution t ~ 100ps FWHM
• Energy resolution ~ 1.4% FWHMdepends on light attenuation in LXe
• Signal is distributed over many PMTs in most cases
• Weighted mean of PMTs on the front face x ~ 4mm FWHM
• Broadness of distribution z ~ 16mm FWHM
• Timing resolution t ~ 100ps FWHM
• Energy resolution ~ 1.4% FWHMdepends on light attenuation in LXe
x
z
Dec. 8th, 2000 NOON 2000 18
Calorimeter Prototypes
• 32 PMTs, 2.3 l LXe• Tested with radioactive sources
51Cr, 137Cs, 54Mn, 88Y• Extrapolated resolutions at 52.8 MeV
in agreement with quoted numbers
“Small” “Large”
• 264 PMTs,150 l LXe
• Assembly finished next January
• Measure resolutions with 40 MeV photon beam at ETL, Tsukuba, Japan
Dec. 8th, 2000 NOON 2000 19
Positron SpectrometerHomogeneous Field
Gradient Field(COnstant-Bending-RAdius)
e+ from +e+e+ from +e+
Ultra-Thin (~3g/cm2)superconducting solenoidwith 1.2 T field
Ultra-Thin (~3g/cm2)superconducting solenoidwith 1.2 T field
Dec. 8th, 2000 NOON 2000 20
Drift Chamber
• 16 radial chambers with 20 wires each• Staggered cells measure both position and time• He – C2H6 gas to reduce multiple scattering• Vernier pattern to determine z coordinate
• 16 radial chambers with 20 wires each• Staggered cells measure both position and time• He – C2H6 gas to reduce multiple scattering• Vernier pattern to determine z coordinate
Dec. 8th, 2000 NOON 2000 21
Prototype Test at PSI
• 0, 0.6, 0.8, 1T field
• 3 tilting angles
• Data analysis finished soon
• 0, 0.6, 0.8, 1T field
• 3 tilting angles
• Data analysis finished soon
Dec. 8th, 2000 NOON 2000 22
Positron timing counter
z
(t )z L
(t )R
L(t )
Rz(t )
e+
e+
e+
Impact Point
1m
• Aimed resolution ~100ps FWHM
• Beam tests at KEK in July 1999
• Taken over by Pisa group
• Scintillators ordered• Beam tests next
spring
• Aimed resolution ~100ps FWHM
• Beam tests at KEK in July 1999
• Taken over by Pisa group
• Scintillators ordered• Beam tests next
spring
e+
Timing Counter
Stopping TargetThin Superconducting Coil
Muon Beam
Drift Chamber
Dec. 8th, 2000 NOON 2000 23
Trigger Requirements
Beam rate 108 s-1
Fast LXe energy sum > 45MeV2103 s-1
interaction point e+ hit point in timing counter time correlation – e+ 200 s-
1
angular corrlation – e+ 20 s-1
Beam rate 108 s-1
Fast LXe energy sum > 45MeV2103 s-1
interaction point e+ hit point in timing counter time correlation – e+ 200 s-
1
angular corrlation – e+ 20 s-1
Ee = 52.8 MeV
Kinematics e= 180°
Eg = 52.8 MeV
e
M.C.
e+
Dec. 8th, 2000 NOON 2000 24
Trigger Implementation
FADC
100MHz 8-bit
FPGAFADC
FADC
FADC
SRAM
Trigger
FADC
FPGAFADC
FADC
FADC
SRAM
BS
BS
BS
BS
Max
Max
Max
.
.
.
T[ns] 0 50 60 70..150 160 170
>45MeV
e+
AND
10 stages = 1024 chn
…800 channels
-
BaselineSubtraction
. . .
Dec. 8th, 2000 NOON 2000 25
Waveform Digitizing
• Waveform Digitizing for all channels• Custom domino sampling chip (DSC) designed at PSI• Costs per DSC ~1US$• 2.5 GHz sampling speed 40ps timing resolution• Sampling depth 1024 bins 400ns (100ns+300ns)• Readout electronics similar to trigger• Drift chamber signals go directly to FADC (100MHz)
• Waveform Digitizing for all channels• Custom domino sampling chip (DSC) designed at PSI• Costs per DSC ~1US$• 2.5 GHz sampling speed 40ps timing resolution• Sampling depth 1024 bins 400ns (100ns+300ns)• Readout electronics similar to trigger• Drift chamber signals go directly to FADC (100MHz)
FPGAFADC SRAM. . .
Analog Waveform Sampling Chip (DSC)
2.5GHz
40MHz, 10 bit
VME
Previous Version 1.2 GHz
C. Brönnimann et al., NIM A420 (1999) 264
Dec. 8th, 2000 NOON 2000 26
Time Table
1997 1998 1999 2000 2001 2002 2003 2004 2005
Planning R & D Assembly Data Taking
now
Conclusions• Preparations are going well in all areas of the experiment• Innovative technologies developed useful for other experiments• Next major milestone: Large prototype test in Tsukuba spring 2001• Increasing support from PSI and Pisa• New collaborators are welcome
• Preparations are going well in all areas of the experiment• Innovative technologies developed useful for other experiments• Next major milestone: Large prototype test in Tsukuba spring 2001• Increasing support from PSI and Pisa• New collaborators are welcome
http://meg.icepp.s.u-tokyo.ac.jphttp://meg.pi.infn.ithttp://meg.psi.ch
http://meg.icepp.s.u-tokyo.ac.jphttp://meg.pi.infn.ithttp://meg.psi.ch