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The silicon detector of the muon g-2 experiment at J-PARC

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  1. The silicon detector of the muon g-2 experiment at J-PARC Vertex 2011, Rust June 24, 2011 Tsutomu Mibe (KEK) for the J-PARC muon g-2/EDM collaboration

  2. Particle dipole moments Hamiltonian of spin 1/2 particle includes Magnetic dipole moment Electric dipole moment Magnetic dipole moment g = 2 from Dirac equation, in general g≠2 due to quantum-loop effects Example : electron + + + … = a “anomalous magnetic moment”

  3. Anomalous magnetic moment : g-2 Dal(exp)/al Dal(SM)/al • Standard model can predict g-2 with ultra high precision • Useful in searching for new particles and/or interactions • Experiment has reached the sensitivity to see such effects... 0.24ppb 0.54ppm 4.5 ppb 0.41ppm HLMNT,Tau 2010 workshop DHMZ, Tau 2010 workshop  To be confirmed by new experiments

  4. Muon anomalous spin precessionin B and E-field • Muon spin rotates “ahead” of momentum due to g-2 >0. • Precession frequency • BNL E821 • Focusing electric field to confine muons. • At the magic momentum g = 29.3, p = 3.094 GeV/c (am -1/(g2-1) ) = 0 Safely be neglected with current upper limit on EDM Continuation of the experiment at FNAL is planned.

  5. Our approach BNL E821 (FNAL ) J-PARC g-2 Compact storage ring • Suited for precision control of B-field • Example : MRI magnet , 1ppm local uniformity • Completely different systematics than the BNL E821 or FNAL 80 cm 14m P= 0.3 GeV/c , B=3.0 T P= 3.1 GeV/c , B=1.45 T Hitachi co.

  6. Our approach (cont’) Zero Focusing Electric field (E = 0 ) Equations of spin motion is as simple as at the magic momentum Ultra-cold muon beam(pT/p < 10-5) by utilizing the laser resonant ionization of muonium makes it possible to realize such experimental condition.

  7. BNL, FNAL, and J-PARC

  8. J-PARC Facility (KEK/JAEA) LINAC 3 GeV Synchrotron Neutrino Beam To Kamioka Materialand Life Science Facility Main Ring (30 GeV 50 GeV) Hadron Hall Bird’s eye photo in Feb. 2008

  9. Surface muon Ultra Cold m+ Source Muon storage Muon LINAC (300 MeV/c) New Muon g-2/EDM Experiment at J-PARC with Ultra-Cold Muon Beam

  10. 3 GeV proton beam ( 333 uA) Graphite target (20 mm) Surface muon beam (28 MeV/c, 4x108/s) Muonium Production (300 K ~ 25 meV⇒2.3 keV/c) Surface muon Ultra Cold m+ Source Muon storage Resonant Laser Ionization of Muonium (~106m+/s) Muon LINAC (300 MeV/c) New Muon g-2/EDM Experiment at J-PARC with Ultra-Cold Muon Beam

  11. 3 GeV proton beam ( 333 uA) Graphite target (20 mm) Silicon Tracker Surface muon beam (28 MeV/c, 4x108/s) 66 cm diameter Muonium Production (300 K ~ 25 meV⇒2.3 keV/c) Surface muon Super Precision Magnetic Field (3T, ~1ppm local precision) Ultra Cold m+ Source Muon storage Resonant Laser Ionization of Muonium (~106m+/s) Muon LINAC (300 MeV/c) New Muon g-2/EDM Experiment at J-PARC with Ultra-Cold Muon Beam

  12. Injection, kicker and positron detector Muon beam is injected here Magnet coil kicker detector mm mm

  13. Expected time spectrum of me+nn decay High energy positron tends to be emitted in the direction of muon spin. ParasiticEDM search in up-down asymmetry g-2 precession spectrum wa Up-down asymmetry ∝EDM dm=2E-20 e・cm Time

  14. Requirements Analyzing power • Detector should be efficient for • Positron track with p = 200 - 300 MeV/c in 3Tsolenoidal B-field • Immune to early-to-late effect • The decay positron rate changes by two orders of magnitude. • 1.6 MHz/strip  10kHz/strip for 200 um pich Silicon strip. • The positron detector must be stable over the measurements. • Zero E-field (<<10-2 V/cm) at muon storage area • Not spoil the precision B-field ( <<0.1ppm) at muon storage area Number of event Above threshold pth(e+) 100MeV/c 200MeV/c 300MeV/c rate per 200 mm strip 1.6 MHz 0.01 MHz Muon life time 6.6 ms

  15. g-2 silicon tracker 576 mm • Tracking vanes made of Double-sided Silicon strip sensor • Anticipating excellent stability and high granularity • Number of sensors • 384 for 24 vanes* • Number of channels • 0.2 mm pitch • 288k for 24 vanes • Detector area • 0.12 * number of vanes [m2] • 2.9 m2 for 24 vanes • * design studies in progress to determine these parameters 580 mm g-2 silicon tracker front back g-2 silicon vane

  16. The detector model • A GEANT4 model made of DSSD sensors (300mm thick) has been developed. • Dynamical Si response yet to be implemented (as discussed by ZbynekDrasal on Wed) • Track-finding performance is a key in the tracker design • Maximum ~10 tracks/10 ns • Algorithm based on the Hough transform in “zf” plane is being explored. Example event display Top view Side view Signal e+ (>150MeV) BG e+ (<150MeV) Lead developers: Kazu Ueno (RIKEN) Hiromi Iinuma (KEK)

  17. Evaluation of DSSD sensor HPK’s Belle-II DSSD sensor (discussed by Markus Fridel on Tue) was used to evaluate timing response of the sensor. A fast shaping ASD was wire-bonded to a part of strips (3x16 strip) ASD Special thanks to Toru Tsuboyama (KEK) and Belle-II SVD group ASD Belle-II DSSD Bias XY stage p-side

  18. Sensors from HPK • Technical details (layers 4,5,6): • Dimensions: 59.6 x 124.88 mm2 • p-side: • Readout pitch: 75 µm • 768 strips • n-side: • Readout pitch: 240 µm • 512 readout strips n-side • Atoll p-stop scheme Markus Friedl

  19. First look at signal from sensor Test pulse (7fC) • Full depletion above 60 V • Well identified signals from 90Sr as well as IR laser with a rise time of 10 nsec • Plan to investigate timing response as a function of bias voltage, instantaneous rate, and temperature. • Plan to perform a beam test at CERN in collaboration with the SiLC. 20 mV/div 40 ns/div IR laser (1060nm), n-side

  20. Front-end electronics • Muon spill comes in every 40 msec. We measure decay positrons for first 33 msec. • Data acquisition sequence resembles to that of LC. The SiLC collaboration led by Aurore Navarro-Savoy (Paris) has been developing FEE for LC. • R&D started to adopt the SiLC front-end technology to this experiment (French-Japan collaborative research program, 2011-2012).

  21. Summary • A new muon g-2/EDM experiment at J-PARC: • Off magic momentum • Ultra-slow muon beam + compact g-2 ring • Start in 2016 • Complementary to FNAL g-2 • Silicon tracker for g-2 • Not quite a vertex detector, but a tracker for incoming low energy positrons • Stringent requirements on early-to-late effect, E-field and B-field • Conceptual design and R&D are in progress