The Mu3e Experiment Introduction and Current Status

The Mu3e Experiment Introduction and Current Status

Moritz Kiehn for the Mu3e Collaboration

Physikalisches Institut, Universität Heidelberg

NuFACT2014, Glasgow, 25. August 2014

The Mu3e Experiment 2

• Precision experiment

• Search forµ⁺→e⁺e⁻e⁺

• Sensitivity<1 in 10¹⁶ decays In this talk

• Experimental Concept

• Current Status

• Pixel Sensor Prototypes

µ → eee in the Standard Model 3

Features

• Charged lepton flavor violating

• Via neutrino mixing

• Expected BR(µ→eee)≪10⁻⁵⁰

• Current Limit from Sindrum

BR(µ→eee)<1·10⁻¹² @90 % CL

Nucl.Phys. B299(1)

Importance

• Observable rate only from New Physics

• Sensitive New Physics Search

Muon Beamlines at PSI 4

Paul Scherrer Institute

• Villigen, Switzerland

• Currently hosts the MEG Experiment Muon Beamlines

• Low energy DC beams

• Current beam lines:

≈1·10⁸µ/s(πE5)

• Future high intensity beam:

>1·10⁹µ/s

2x109 µ/s

50 ns integration

Signal and Backgrounds 6

Signal

e⁺

e⁺ e^-

Backgrounds Internal Conversion

e^- e⁺

e^{+ ν}

ν

Combinatorial

e⁺

e⁺ e^-

• Common vertex

•

P~p_i =0

• p <53 MeV

• Common vertex

•

Pp~_i 6=0

• In-time

• No common vertex

• Out-of-time Requires σp<0.5 MeV

σ_t <1 ns

Multiple Scattering 7

Ω MS

θ

B

θ

∼

p x / X

Example

• p =35 MeV

• 200 µm Si

• ΩR =5 cm

• ∆y ≈1 mm

→ Low material budget

Detector Concept 8

Target μ Beam

Environment

• >10⁹ µ⁺ Decays/s

• Electrons p<53 MeV

• Multiple scattering dominates

Detector Concept 8

Target Inner pixel layers μ Beam

Environment

• >10⁹ µ⁺ Decays/s

• Electrons p<53 MeV

• Multiple scattering dominates

Detector Concept 8

Target Inner pixel layers

Scintillating fibres

Outer pixel layers μ Beam

Environment

• >10⁹ µ⁺ Decays/s

• Electrons p<53 MeV

• Multiple scattering dominates

Detector Concept 8

Target Inner pixel layers

Scintillating fibres

Outer pixel layers Recurl pixel layers

Scintillator tiles

μ Beam

Environment

• >10⁹ µ⁺ Decays/s

• Electrons p<53 MeV

• Multiple scattering dominates

Full Detector 9

Magnetic field∼1 T Continuous readout

Tracker Requirements

• Fast serial readout ∼20 MHz

• Thin<1 ‰X₀

• 80 µm×80 µm pixel

• 1 cm×2 cm sensor area

Timing

• Resolution<1 ns

Ultra-Lightweight Mechanics 10

• 50 µm Silicon sensor

• 25 µm Kapton flexprint

• 25 µm Kapton support frame

→ ∼1 ‰Radiation length

Scintillating Fibres 12

Fibre and SiPM Array

Signal Spectrum

Efficiency > 98%

(2 photons or more)

Single Photon

• 3-5 layers of fibres

• Readout with SiPM and custom ASIC (StiC)

• Time resolution

∼1 ns (²²Na-source)

Scintillating Tiles 13

Tile Station

Tile Prototype

3.5 cm

Time Resolution

Time Difference [ps]

-7500 -500 -250 0 250 500 750

2000 4000 6000 8000 10000

σ = 79.2 ps

• ∼0.5 cm³ per tile

• Readout with SiPM and custom ASIC (StiC)

• Time resolution

∼80 ps(testbeam)

Monolithic Active Pixel Sensors 14

I. Peric, P. Fischer et al. NIMA 582(2007)876

• HV∼70 V (HV-MAPS)

• Fast charge collection by drift

• Thin active zone<20 µm

• Cheap, commercial process

HV-MAPS Prototypes 15

Design Specifications

• 80 µm×80 µm pixel size

• 1 cm×2 cm active area MuPix2

• 39 µm×30 µm pixel size

• 1.8 mm×1 mm active area

• Proof of Concept MuPix3/4

• 92 µm×80 µm pixel size

• 2.9 mm×3.2 mm active area

MuPix4 HV-MAPS Prototype 16

32 Columns / 2.944 mm

40 Rows / 3.2 mm ^• 92 µm×80 µm pixel size

• Global threshold

• Zero-suppressed digital readout

• Timestamps

• Additional readout FPGA

Single Hit Resolution 19

1.5 1.0 0.5 0.0 0.5 1.0 1.5

Column Residuals

1.5 1.0 0.5 0.0 0.5 1.0 1.5

Row Residuals

Pixel 92 µm

80 µm

0 500

Rate / a.u.

0 200

Rate / a.u.

612 1824 3036 4248 54

Rate / a.u.

0° incidence angle 70 V high voltage 823 mV threshold

Global Efficiency 20

820 830 840 850 860 870 880

Global Threshold / mV

0.88 0.90 0.92 0.94 0.96 0.98 1.00

Efficiency

HV = 70V E = 5GeV

0.0° incidence angle 22.5° incidence angle 45.0° incidence angle

Effective thickness∼1/cosα

Pixel Efficiency 21

0 5 10 15 20 25 30

Column Number

0 5 10 15 20 25 30 35

Row Number

0.980.99 1.00

Efficiency

0.98 1.00

Efficiency

0.10.2 0.30.4 0.50.6 0.70.8 0.91.0

Efficiency

0° incidence angle 70 V high voltage 823 mV threshold

Subpixel Efficiency / 4x4 Pixels 22

0 1 2 3

Column Number

0 1 2 3

Row Number

0.980.99 1.00

Efficiency

0.98 1.00

Efficiency

0.10.2 0.30.4 0.50.6 0.70.8 0.91.0

Efficiency

0° incidence angle 70 V high voltage 823 mV threshold

Timing 23

-400 -200 0 400

500 1000 1500 2000 2500 3000

200

Difference between trigger and timestamp [ns]

σ = 16.6 ns

Hits per 10 ns bin

Timestamp frequency 100 MHz

• Sensor + DAQ

• Resolution 17 ns

Future MuPix Prototypes 24

MuPix6

• Currently in the lab

• Updated analog part, e.g.

2-stage amplifier

• Same geometry MuPix7

• Just submitted

• Fast serial readout

• Full digital logic

• Still small scale prototype

Cooling with Helium 25

Why Helium?

• Low density, low scattering

• High mobility Temperature Gradient

3.5 m/s in air

Reconstruction 26

Reconstruction Efficiency

• >90 % efficiency for 4-hit tracks

• Dropoff is detector acceptance

Momentum Resolution

3-hit track, σ ≈1.5 MeV

6-hit track, σ≈0.2 MeV

• Full GEANT4 simulation

• Custom reconstruction

• Noenergy loss correction

Expected Sensitivity 27

Phase IA: earliest 2016

• 2·10⁷µ/s

• Central pixel layers Phase IB: 2017+

• 1·10⁸µ/s + Timing

+ 1^st recurl stations Phase II: 2019+

• 2·10⁹µ/s

• Full detector

• Future Muon Beamline

Expected Sensitivity 27

Phase IA: earliest 2016

• 2·10⁷µ/s

• Central pixel layers Phase IB: 2017+

• 1·10⁸µ/s + Timing

+ 1^st recurl stations Phase II: 2019+

• 2·10⁹µ/s

• Full detector

• Future Muon Beamline

Expected Sensitivity 27

Phase IA: earliest 2016

• 2·10⁷µ/s

• Central pixel layers Phase IB: 2017+

• 1·10⁸µ/s + Timing

+ 1^st recurl stations Phase II: 2019+

• 2·10⁹µ/s

• Full detector

• Future Muon Beamline

The Mu3e Collaboration 28

Paul Scherrer Institute University Geneva ETH Zürich University Zürich Heidelberg University

Karlsruhe Institute of Technology Mainz University

Summary and Outlook 29

Mu3e

• Search forµ⁺→e⁺e⁻e⁺

• Sensitivity<1 in 10¹⁶ decays Features

• HV-MAPS silicon sensors

• Ultra-thindetector

• Down to100 pstiming

• Up to2·10⁹µ/s

In the Future

• First data in 2016+

• Full rate not before 2019

http://www.psi.ch/mu3e

Backup

Silicon Pixel Sensors A1

Hybrid

Sensor 250 μm Readou

t chip 180 μm

Pixel

Pixel electronics Connection via solder bump

Global logic and data driver

Monolithic Active Pixel Sensor

Mon olithic Senso

r 50 μm

Pixel

Pixel electronics

Global logic and data driver On-chip interconnect

• HV ∼700 V

• Sensor thickness∼250 µm

• Extra material

• Complex and expensive

• HV ∼70 V (HV-MAPS)

• Thin active zone<20 µm

• Cheap, commercial process

Beyond the Standard Model A2

In Loops At Tree Level

• e.g. SUSY • e.g new heavy boson

Global Efficiency / High Voltage A3

820 830 840 850 860 870 880

Global Threshold / mV

0.82 0.84 0.86 0.88 0.90 0.92 0.94 0.96 0.98 1.00

Efficiency

0° incidence angle E = 5GeV

HV = 50V

HV = 70V

ǫ =