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 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... Dal(exp)/al Dal(SM)/al 0.24ppb 0.54ppm 4.5 ppb 0.41ppm a exp – a SM = (296 ± 81)  10 –11 (259 ± 81)  10 –11  3.2~3.6 ”standard deviations“ HLMNT,Tau 2010 workshop DHMZ, Tau 2010 workshop  To be confirmed by new experiments

Muon anomalous spin precession in 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 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 BNL E821 (FNAL ) J-PARC g-2 80 cm 14m P= 3.1 GeV/c , B=1.45 T P= 0.3 GeV/c , B=3.0 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.

BNL, FNAL, and J-PARC BNL-E821 Fermilab J-PARC Muon momentum 3.09 GeV/c 0.3 GeV/c gamma 29.3 3 Storage field B=1.45 T 3.0 T Focusing field Electric quad None # of detected m+ decays 5.0E9 1.8E11 1.5E12 # of detected m- decays 3.6E9 - Precision (stat) 0.46 ppm 0.1 ppm

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

New Muon g-2/EDM Experiment at J-PARC with Ultra-Cold Muon Beam 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

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 (~106 m+/s) Muon LINAC (300 MeV/c) New Muon g-2/EDM Experiment at J-PARC with Ultra-Cold Muon Beam

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 (~106 m+/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 mm detector

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

Requirements Detector should be efficient for Positron track with p = 200 - 300 MeV/c in 3T solenoidal 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 Analyzing power 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 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 576 mm 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 Zbynek Drasal 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 21 June 2011 Markus Friedl

First look at signal from sensor Test pulse (7fC) 20 mV/div 40 ns/div IR laser (1060nm), n-side 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.

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