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
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”
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
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.
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.
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.
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
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
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
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
Injection, kicker and positron detector Muon beam is injected here Magnet coil kicker detector mm mm
Expected time spectrum of me+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
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
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
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)
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
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
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
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).
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