Daisuke Kaneko, on behalf of the MEG(II) collaboration 26 Aug, Moscow Today and Tomorrow of the MEG experiment

Mu E Gamma Little SM background via ν oscillation Many beyond SM theories predict SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS 2 MEG experiment MEG A SM + ν oscillation example of SUSY MEG 2013 PRL110, (2013) E842 μ (g-2) PRD73(2006)072 Example of MSSM Large tanβ & Heavy squark Isidori et al, Phys. Rev. D 75, (2007) Too Low to detect Possibility to detect if exist prediction from new physics

Signal and BackGround SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS γ Signal Event μ+μ+ e + Accidental BG μ+μ+ e + νμνμ νeνe γ μ+μ+ νμνμ νeνe γ Radiative Decay eventEγEe+TimeAnglenote Signal52.8 MeV Te = Tγ180° Acc BG <52.8 MeV ≦ 52.8 MeV uniformno correlateDominant BG RD<52.8 MeV Te = Tγ ≦ 180° < 1/10 of Acc

Today : MEG I experiment SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS4

MEG at Paul Scherrer Institute The world’s most intense μ beam –10 8 πE5 line DC current –Advantage to avoid accidental pile up Surface muon –Small momentum spread SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS MeV, 2.2 mA, 1.3 MW, 50.6 MHz PSI SμS proton ring cyclotron ～ 60 researchers from 5 countries SINDRUM experiment (μ-e conv.) was done in the same place

MEG I instruments SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS 6 Liquid xenon γ-ray detector Timing counter COBRA magnet with Gradient B field Low-mass Drift chamber μ + stopping target Being disassemble d

MEG I steps SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS : First physics data taking 2010 : Result with 2008 data S = 1.3 x , UL = 2.8 x (90% CL) 2011 : surpassed previous experiment Result with data S = 1.6 x , UL = 2.4 x (90% CL) 2013 : current world record Combined result S = 7.7 x , UL = 5.7 x (90% CL) Phys. Rev. Lett. 107, Phys. Rev. Lett. 110, Integrated statistical amount 2013 : Finished data acquisition 2015 : final result of MEG I (expected) Nucl. Phys. B, ×2 1 / Single Event Sensitivity ( ) Blinded data sensitivityupper limit

Analysis of MEG data SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS 8 Best fit Nsig is estimated by likelihood fitting on analysis region. Confidence region is set by a frequentist method with a profile likelihood-ratio ordering The analysis region is blinded until the PDFs for the likelihood analysis are finalized. The PDFs are extracted from side-band data or calibration data. from MEG 2013 result Analysis region Time side band Time side band Eγ side band teγ[ns] Eγ[MeV] Constraints of N BG and N RD estimated from the sideband data signal contou r 1σ 1.64σ 2σ

MEG I final result SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS 9 In final MEG analysis, data amount is doubled. In addition, analysis has been improved since previous analysis for 2013 result. S ~ 7.7× S ~ 5× Reduction of BG-γ from annihilation in flight of positron When BG γ is generated by annihilation in tracker. It can be tagged by checking disappearing e + track and γ hit point. Positron missing turn recovery Improve the efficiency to connect track-segments of multiple turn e+ tracks, In a case where e + turns more than once, if 1st and 2nd turn were identified separately. A wrong vertex can be reconstructed. Target alignment with 3D scanner In 2012 and 2013 data, deformation of μ target was found. It is taken into account in vertex reconstruction and the systematic error is included the likelihood function. MEG I final result comes soon !

Tomorrow : MEG II experiment SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS10

MEG II concept 10 times better sensitivity, B ～ O( ) ! –Keep basic concept of experiment upgrade with low cost, in short term –Use full potential of PSI beam line Higher μ + intensity, ×2-3 –Improve detector performance Overall efficiency ×2 Resolution /2 for all Eγ, Ee, teγ, θeγ and φeγ SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS 11

Over view of the detector upgrades SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS 12 thinner target additiona l detector “RDC” Liquid xenon read out with SiPM Unified volume Stereo wired Drift chamber Pixelated Timing counter Many SiPMs xenon detector timing counter RDC

Upgraded γ detector SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS 13 Lesson from MEG I : Improve uniformity of light collection especially when γ ray converts near inner wall. PM T MPP C PM T CG image depth <2cm 2.4% ↓ 1.1% present upgraded depth from window [cm] position resolution [mm] present upgraded The energy and position resolutions will be greatly improved. γ detection efficiency increases by 10%, thanks to low-mass of MPPC.

LXe MPPC SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS 14 New sensor has been developed in collaboration with Hamamatsu 2-inch PMT Normal MPPC (3x3 mm 2 ) VUV MPPC (12x12 mm 2 ) >15% PDE for LXe scintillation light (λ ～ 175nm). Four 6x6 mm 2 chips are connected in series, in order to reduce sensor capacitance (, and thereby to get sharper signal). A technology to suppress crosstalk is applied to the final version 1 kΩ 22n F

Status of γ-detector upgrade SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS 15 We performed prototype test with 600 MPPCs in Liquid Xenon. Operation of MPPC, cable, connector, feedthrough etc. were confirmed. Now, ~4000 pcs of final version MPPCs are being produced, and tested.

New Drift chamber SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS 16 Lesson from MEG I : Many positrons were lost by hitting structure at the end of the drift chamber. timing counter Scattered at the flame and readout board Positron reconstruction efficiency 40% → 90% ・ Single volume ・ Stereo wired single hit resolution σ ～ 0.1mm more detect points by finer cell Angular resolution of e+ emission 9mrad → 5mrad Momentum resolution 350 keV → 130 keV timing counter No extra materials between timing counter

Status of new Drift chamber SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS 17 ・ Test of resolution and ageing with prototypes were already finished. ・ Full-scale and partially wired “mockup chamber” was made → tested in engineering run ・ Production of front-end electronics started Wiring machineMockup delivered

New Timing counter SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS 18 MEG I TC : As much photoelectrons with large scintillator (PMT readout) MEG II TC : Hit time measurement with multiple hits in segmented timing counter (SiPM readout) High rate tolerance, better timing resolution σ ～ 30ps Single Counter 6 series SiPMs (AdvanSiD) on both side 12cm 4/5cm t 5mm average Nhit

Status of new TC SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS 19 Beam test was performed to demonstrate multi-hit scheme e+e+ Prototype Counters Beam test in PSI πE5 area Beam test result Currently mass-production is underway. 1/4 of full detector will be tested in engineering run at end of this year. Expected timing resolution is obtained average Nhit resolution of single detector is worse due to the performance of SiPM Expectation from single resolution RC Analysis Odd–Even Analysis RC Analysis with hit selection Reference Counters

New Detector to reduce BG SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS 20 Low energy positron Down-stream RDC plastic scintillator + LYSO Up-stream RDC scintillation fiber Under Constructio n needs study about beam disturbanc e Radiative Decay Counter

Developments in Electronics SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS 21 “WaveDREAM” An integrated board with ・ Analog amplifier ・ HV supply ・ Waveform digitizer (DRS4) ・ 1st level trigger 16 channels in a board, 16 boards in a crate(3U), The first crate will be available in this autumn. The number of readout channels will increase by more than factor 2.

MEG II Prospects SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS 22 After 3 years of data taking, Expected sensitivity is 4-5 x

Schedule SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS Accelerator ONAccelerator OFFAccelerator ONAccelerator OFF construction Engineering run preparation μbeam DAQ Installation Calibration Beam tuning Calibration Test DAQ Start MEG II physics run when we will get ready

Conclusion SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS 24

Thank you for your listening

MEG beam line SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS 26 μ-e Separator Beam Transportation Solenoid

gradient B field SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS 27 e + quickly swept out. Bending radius depends on emission angle on ly little.

Positron AIF SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS 28 AIF Observables Δθ AIF, Δφ AIF, Δt AIF : Comparison of e + & γ R AIF, Z AIF, φ AIF : Where AIF occurred target Liquid Xenon Drift Chamber Δθ,φ,t AIF R,φ,Z AIF Δθ AIF Δφ AIF Δt AIF correct AIF pair random AIF pair Signal RD simulate

missing turn SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS 29 1 st trun 2 nd trun wrong vertex true vertex

BG γ SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS 30

PDE of LXe MPPC SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS 31 crosstalk suppression applied

SEVENTEENTH LOMONOSOV CONFERENCE ON ELEMENTARY PARTICLE PHYSICS 32