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

Daisuke Kaneko,on behalf of the MEG(II) collaboration26 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

MEGexperiment

MEGA

SM + ν oscillation

example of SUSY

MEG 2013PRL110, 201801(2013)

E842 μ (g-2)PRD73(2006)072

Example of MSSMLarge tanβ & Heavy squarkIsidori et al, Phys. Rev. D 75, 115019 (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+ e +

Accidental BG

μ+ e +νμνeγ μ+ e +

νμ

νeγ

Radiative Decay

event Eγ Ee+ Time Angle note

Signal

52.8 MeV 52.8 MeV Te = Tγ 180°

Acc BG

<52.8 MeV

≦52.8 MeV

uniform no correlate

Dominant BG

RD <52.8 MeV

<52.8 MeV

Te = Tγ ≦180° < 1/10 of Acc

Today :

MEG I experiment


MEG at Paul Scherrer Institute• The world’s most intense μ

beam– 108 μ/s @ πE5 line

• DC current– Advantage to avoid accidental pile up

• Surface muon– Small momentum spread


590 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


Liquid xenonγ-ray

detector

Timing counter

COBRA magnet with

Gradient B field

Low-massDrift

chamber

μ+ stopping

targetBeing

disassembled

MEG I steps


2008 : First physics data taking

2010 : Result with 2008 data S = 1.3 x 10-11, UL = 2.8 x 10-11 (90% CL)

2011 : surpassed previous experiment Result with 2009+2010 data S = 1.6 x 10-12, UL = 2.4 x 10-12 (90% CL)

2013 : current world record Combined result 2009-2011 S = 7.7 x 10-13, UL = 5.7 x 10-13 (90% CL)

Phys. Rev. Lett. 107, 171801

Phys. Rev. Lett. 110, 201801

Integrated statistical amount

2013 : Finished data acquisition

2015 : final result of MEG I (expected)

Nucl. Phys. B, 834 1

×2

×2

×2

1 /

Sin

gle

Even

t Sensi

tivit

y

(10

-12)

Blindeddata

sensitivity

upper limit

Analysis of MEG data


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

Analy

sis

regio

n

Tim

esi

de b

an

d

Tim

esi

de b

an

d

Eγside band

teγ[ns]

Eγ[MeV]

Constraints of NBG and NRD estimated from the sideband data

signalcontour1σ1.64σ2σ

MEG I final result


In final MEG analysis, data amount is doubled.

In addition, analysis has been improved since previous analysis for 2013 result.

S ~ 7.7×10-13

S ~ 5×10-13

Reduction of BG-γ from annihilation in flight of positronWhen BG γ is generated by annihilation in tracker. It can be tagged by checking disappearing e+ track and γ hit point.

Positron missing turn recoveryImprove 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 scannerIn 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


MEG II concept

• 10 times better sensitivity, B ～ O(10-14) !

– 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


Over view of the detector upgrades


thinnertarget

additionaldetector“RDC”

Liquid xenonread out with SiPM

Unified volumeStereo wiredDrift chamber

PixelatedTiming counter

ManySiPMs

xenon detector

timing counter

RDC

Upgraded γ detector


Lesson from MEG I :

Improve uniformity of light collection especially when γ ray converts near inner wall.

PMT

MPPC

PMT

CG image

depth<2cm2.4%

↓1.1%

present

upgraded

depth from window [cm]

pos

itio

n r

esol

uti

on [

mm

]

presentupgraded

The energy and position resolutions will be greatly improved.

γ detection efficiency increases by 10%,thanks to low-mass of MPPC.

LXe MPPC


New sensor has been developed in collaboration with Hamamatsu

2-inch PMT

Normal MPPC(3x3 mm2)

VUV MPPC(12x12 mm2)

>15% PDE for LXe scintillation light (λ ～ 175nm).

Four 6x6 mm2 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

22nF

Status of γ-detector upgrade


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


Lesson from MEG I :

Many positrons were lost by hitting structure atthe 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 ～0.1mmmore detect points by finer cell

Angular resolution of e+ emission

9mrad → 5mradMomentum resolution

350 keV → 130 keV

timing counter

No extra materials between timing counter

Status of new Drift chamber


・ 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 startedWiring machine Mockup delivered

New Timing counter


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

4/5

cm

t 5mm

average Nhit

Status of new TC


Beam test was performed to demonstrate multi-hit scheme

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 resolutionRC AnalysisOdd–Even AnalysisRC Analysis with hit selection

Reference Counters

New Detector to reduce BG


Low energy positron

Down-stream RDCplastic scintillator

+ LYSO

Up-stream RDCscintillation fiber

UnderConstructi

on

needs studyabout beam

disturbance

RadiativeDecayCounter

Developments in Electronics


“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


After 3 years of data taking,Expected sensitivity is 4-5 x10-14

Schedule


2015 2016 2017

Accelerator ONAccelerator OFFAccelerator ONAccelerator

OFF

construction

Engineeringrun preparation

μbeamDAQ

InstallationCalibration

Beam tuningCalibrationTest DAQ

Start MEG II physics runwhen we will get ready

Conclusion


Thank you for your listening

MEG beam line


μ-e

Separator

Beam Transportation Solenoid

gradient B field


e+ quickly swept out.

Bending radius depends on emission angle on ly little.

Positron AIF


AIF ObservablesΔθAIF, ΔφAIF, ΔtAIF :

Comparison of e+ &

γ

RAIF, ZAIF, φAIF :

Where AIF occurred

target

Liquid Xenon

Drift Chamber

Δθ,φ,tAIF

R,φ,ZAIF

ΔθAIF ΔφAIF ΔtAIF correctAIF pair

randomAIF pair

Signal RDsimulate

missing turn


1st trun2nd trun

wrong vertex

true vertex

BG γ


PDE of LXe MPPC


crosstalk suppressionapplied

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

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