Status of the Mu3e Experiment https://www.psi.ch/mu3e/ Search for + - - PowerPoint PPT Presentation

• A. Schöning on behalf of Mu3e 1

CLFV19 Conference

Status of the Mu3e Experiment

CLFV 2019 Conference “Charged Lepton Flavor Violation” 17.-20.6. 2019, Fukuoka (Kyushu)

https://www.psi.ch/mu3e/

Search for µ+ → e+ e+ e-

• A. Schöning on behalf of Mu3e 2

CLFV19 Conference

Mu3e Collaboration

Germany

• University Heidelberg
• Karlsruhe Institute of Technology
• University Mainz

Switzerland

• University of Geneva
• Paul Scherrer Institute
• ETH Zurich
• University Zurich
• [University of Applied Sciences Northwestern Switzerland]

United Kingdom

• Bristol
• Liverpool
• Oxford
• UC Londonabout 60 members; ~15 PhD students

• A. Schöning on behalf of Mu3e 3

CLFV19 Conference

HiPA @ PSI & PiE5 Area

Compact Muon Beamline for Mu3e:

MEG

Mu3e World’s most intense continuous muon beam (f=50MHz) World’s most intense continuous muon beam (f=50MHz) 2.4 mA protons at 590 MeV → 1.5 MW 2.4 mA protons at 590 MeV → 1.5 MW

• Low momentum muons 29 MeV/c
• PiE5 beamline will be shared between MEGII and Mu3e

HiPA and Experimental Hall: expect 1.4∙108 μ+7s at 2.4 mA for a 60 mm target

• A. Schöning on behalf of Mu3e 4

CLFV19 Conference

Mu3e Experiment

Pixel Tracker Scintillating Fibers Scintillating Tiles Aiming for a sensitivity (SES)

BR(μ → e e e ) < 2·10-15 BR(μ → e e e ) < 10-16

(phase I) (phase II)

requires: → 108 muons/s (PiE5) → >109 muons/s (HiMB)

HiMB = High intensity Muon Beamline (under study)

• A. Schöning on behalf of Mu3e 5

CLFV19 Conference

LFV Decay μ+ →fe+e+e- LFV Decay μ+ →fe+e+e-

Exotic Physics

Supersymmetry Little Higgs Models Seesaw Models GUT models (Leptoquarks) many other models

loop diagrams (similar to µ → e γ) tree diagram (Mu3e specific)

Higgs Triplet Model New Heavy Vector bosons (Z') Extra Dimensions (KK towers)

Most models “naturally” induce lepton flavor violation!

• A. Schöning on behalf of Mu3e 6

CLFV19 Conference

Matrix Element Dependence Matrix Element Dependence

use effective operator framework

OV

RL

OS

RR or OV RR

OD

R

Very distinct signal distributions!

generator level:

thesis A.-K.Perrevoort

e.g. A. Crivellin et al. JHEP 05 (2017) 117.

m1(e+e-) vs m2(e+e-)

thesis A.-K.Perrevoort

• A. Schöning on behalf of Mu3e 7

CLFV19 Conference

Matrix Element Dependence Matrix Element Dependence

use effective operator framework

OV

RL

OS

RR or OV RR

OD

R

Very distinct signal distributions! (also after full reco)

reconstructed:

e.g. A. Crivellin et al. JHEP 05 (2017) 117.

m1(e+e-) vs m1(e+e-)

thesis A.-K.Perrevoort

• A. Schöning on behalf of Mu3e 8

CLFV19 Conference

e+ e+ e-

∑i E i = mμ ∑i ⃗

pi = 0 e+ e+ e- ν ν

B(μ+ →f e+e+e- νν) = 3.4 ·10- 5

Mu3e signal

Irreducible Background Irreducible Background

radiative decay with internal conversion μ+ →f e+e+e-

• A. Schöning on behalf of Mu3e 9

CLFV19 Conference

Irreducible Background Irreducible Background

radiative decay with internal conversion

e+ e+ e- ν ν

missing energy from two neutrinos steeply falling!

R.M.Djilkibaev, R.V.Konoplich PRD79 (2009)

B(μ+ →f e+e+e- νν) = 3.4 ·10- 5

very good momentum + total energy resolution required!

missing energy taken by neutrinos

• A. Schöning on behalf of Mu3e 10

CLFV19 Conference

Accidental Backgrounds Accidental Backgrounds

Overlays of two ordinary µ+ decays with a (fake) electron (e-)

Electrons from: Bhabha scattering, photon conversion, mis-reconstruction Need excellent: Vertex resolution Timing resolution Kinematic reconstruction

• A. Schöning on behalf of Mu3e 11

CLFV19 Conference

Expected Electron Backgrounds Expected Electron Backgrounds

Momentum distribution of electrons produced in target region

Bhabha γ conversion Compton IC

• A. Schöning on behalf of Mu3e 12

CLFV19 Conference

Mu3e Baseline Design

p=28 MeV/c

108 muons per second (phase I)

• A. Schöning on behalf of Mu3e 13

CLFV19 Conference

Mu3e Baseline Design

• ultra thin silicon pixel detector (HV-MAPS) with 1 per mill radiation length / layer

80 x 80 µm2 pixel

• A. Schöning on behalf of Mu3e 14

CLFV19 Conference

Mu3e Baseline Design

• fast timing detectors (scintillating fibers)
• ultra thin silicon pixel detector (HV-MAPS) with 1 per mill radiation length / layer

σ(t) < 1 ns

• A. Schöning on behalf of Mu3e 15

CLFV19 Conference

Mu3e Baseline Design

~180 cm

Long cylinder!

~15 cm not to scale!

recurl stations with silicon pixel detector (HV-MAPS) and scintillating tiles

σ(t) < 100 ps

• A. Schöning on behalf of Mu3e 16

CLFV19 Conference

Mu3e Baseline Design

+ strong magnetic field (B=1T) + helium gas cooling

helium atmosphere transverse view:

• A. Schöning on behalf of Mu3e 17

CLFV19 Conference

Standard spectrometer: σ p P ∼ ΘMS Ω

requires large lever arm large bending angle Ω

(linearised)

Momentum Resolution Momentum Resolution

“Half turn” spectrometer: σ p P ∼ O(ΘMS

2 )

multiple-scattering angle

best precision for half turn tracks measure recurlers

• A. Schöning on behalf of Mu3e 18

CLFV19 Conference

50 µm MuPix (HV-MAPS) High Density Interconnect (< 100 µm)

(LTU, Ukraine)

(Outer) Pixel Tracker Module

Monolithic pixel sensor in 180 nm HV-CMOS

Ultra-thin pixel sensor modules with a radiation length of X/X0 = 1.15 per mil

• A. Schöning on behalf of Mu3e 19

CLFV19 Conference

Pixel Detector Technology

I.Peric et al., NIM A 582 (2007) 876

transistor logic embedded in N-well (“smart diode array”)

• active sensors

→f hit finding + digitisation + readout

• HV-CMOS 180nm: 60-120 V
• low cost process (AMS, TSI)
• “thinned” to ~50 μm (~ 0.0005 X0)

High Voltage-Monolithic Active Pixel Sensor (HV-MAPS)

MuPix8 prototype (2018) MuPix has been fully characterized in the lab and in several test beams

• efficiency
• noise + rate
• (radiation hardness)
• temperature-dependence

2 cm pixel size 80 x 80 μm2

• A. Schöning on behalf of Mu3e 20

CLFV19 Conference

Mupix8 Performance Plots

efficiency ~99.9% noise ~1Hz/pixel

time resolution ~ 6.5ns

Mupix 8 beam telescope (4 layers) → Mupix10 submission (20x20 mm2) in summer

• A. Schöning on behalf of Mu3e 21

CLFV19 Conference

Mupix10 will implement three design variations for final sensor decision → Mupix11

Mupix10 Specification

not to scale!

• A. Schöning on behalf of Mu3e 22

CLFV19 Conference

Thermo-Mechanical Prototype

used to test:

• assembly procedures
• mechanical stability (vibrations)
• helium cooling

steel plates

Mu3e Vertex layer

• A. Schöning on behalf of Mu3e 23

CLFV19 Conference

Pixel Detector + Helium Gas Cooling

He gas cooling concept → temperatures 20-50 °C → no extra material in active volume!

He gas cooling simulation ~15 cm

pixel tracker: central and two recurl stations ~ 200 million pixels

• A. Schöning on behalf of Mu3e 24

CLFV19 Conference

Timing Detectors

Scintillating Tiles

• tiles

6.5 × 6.5 × 5mm

• 3
• SiPM 3 x 3 mm2
• Readout with MuTrig ASIC
• time resolution < 100ps

Scintillating Fibres

• 3 staggered layers of 250 µm scintillating fibres

(SCSF-78MJ from Kuraray)

• very thin ~0.2% X0
• 128 channel SiPM array from Hamamatsu
• Readout with MuTrig ASIC
• time resolution < 500ps

• A. Schöning on behalf of Mu3e 25

CLFV19 Conference

Timing Performance

Scintillating Tile Sub-Module

DESY test beam

Time resolution < 100ps Scintillating Fibres

4-layer ribbon in test beam 3-layer ribbon in test beam

Time resolution ~ 370ps

• A. Schöning on behalf of Mu3e 26

CLFV19 Conference

Simulation and Performance

• A. Schöning on behalf of Mu3e 27

CLFV19 Conference

Charge Identification

positron loopers → charge confusion

Main process: μ+ → e+ νe νμ

positrons electrons

Significant reduction of BG for: μ+ → e+ e+ e-

X X

t1 t2

Time difference vs path length

Δt=t2 - t1 [ns] Δs/c [ns]

transverse view

• A. Schöning on behalf of Mu3e 28

CLFV19 Conference

Simulation and Performance

Track Momentum Resolution Track Reconstruction Efficiency

gaps between pixel track stations excellent! σp/p= 1% limited acceptance DS US

• A. Schöning on behalf of Mu3e 29

CLFV19 Conference

Mu3e Mass Plot (Phase I)

(upper limit)

10-12 10-13 10-14 10-15

Simulation

hypothetical signal

• A. Schöning on behalf of Mu3e 30

CLFV19 Conference

Mu3e Sensitivity (Phase I)

• A. Schöning on behalf of Mu3e 31

CLFV19 Conference

Mu3e Status and Plans

New “Skywalk” Superconducting Solenoid B=1 Tesla

Superconduction solenoid produced by Cryogenic (London) Delivery expected in summer 2019

• A. Schöning on behalf of Mu3e 32

CLFV19 Conference

Mu3e Summary

Very successful R&D program e.g. HV-MAPS, fast timing, (GPU-filter farm) Mu3e Technical Design finished (TDR unpublished) Working on Production Readiness and Pre-production Phase 1 Detector construction in 2020721 More muons with High Intensity Muon Beamline (HiMB Project) Aim: B(μ+ →f e+e+e-) ≤ 10-16 (90% CL) Unique discovery potential for New Physics

• A. Schöning on behalf of Mu3e 33

CLFV19 Conference

Mu3e Future Prospects

Mu3e Phase II

• requires design and approval of High Intensity Muon Beam Line (HiMB)
• not before 2025, physics program up to ~2030
• redesign of phase I detector → larger acceptance + higher rates

• A. Schöning on behalf of Mu3e 34

CLFV19 Conference

Exotic Searches with Mu3e

• A. Schöning on behalf of Mu3e 35

CLFV19 Conference

Search for Familons μ+→ e+X

mX=60 MeV Michel BG Projected Mu3e Sensitivity (Phase I)

• Familons are the Goldstone Bosons of a

spontaneously broken flavor symmetry

• μ+ → e+ X is 2-body decay
• Search for a peak on the e+ momentum distr.

thesis A.-K.Perrevoort thesis A.-K.Perrevoort

• A. Schöning on behalf of Mu3e 36

CLFV19 Conference

Search for Dark Photons in A’→ e+e-

signal backgrounds

• Search for Dark Photons with zero
• r short lifetime:

µ+ → e+ νe νµ A’ with A’ → ee

• peak in m(e+e-) invariant mass

thesis A.-K.Perrevoort