The Mu2e crystal calorimeter Eleonora Diociaiuti LNF-INFN and Tor - - PowerPoint PPT Presentation

The Mu2e crystal calorimeter

Eleonora Diociaiuti LNF-INFN and Tor Vergata University

• n behalf of the Mu2e calorimeter group

July 7, 2018 XXXIX INTERNATIONAL CONFERENCE ON HIGH ENERGY PHYSICS

FERMILAB-SLIDES-18-79E This document was prepared by Mu2e collaboration using the resources of the Fermi National Accelerator Laboratory (Fermilab), a U.S. Department of Energy, Office of Science, HEP User Facility. Fermilab is managed by Fermi Research Alliance, LLC (FRA), acting under Contract No. DE-AC02-07CH11359.

Talk overview

• The Mu2e experiment
• CLFV introduction
• Experiment layout
• Mu2e Electromagnetic Calorimeter
• Components
• Performance
• Production status

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Charged Lepton Flavor Violation

• CLFV processes are forbidden in SM
• Even allowing neutrino oscillation BR ~ 10-54
• Observation of a CLFV process: clear evidence of New Physics
• Mu2e : Coherent muon conversion in the electric field of a nucleus
• Broad sensitivity across different models
• Very clear signature: monoenergetic electron
• Improve of 4 orders of magnitude the previous limit set by the

SINDRUM II experiment (6.1× 10-13)

Rµe = µ− + N(A, Z) → e− + N(A, Z) µ− + N(A, Z) → νµ + N(A, Z − 1) < 8.4 × 10−17

µ-e conversion in the field of a nucleus Nuclear capture of muonic Al atom

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3 Ee = mµc2 − (B.E.)1S − Erecoil = 104.96MeV

8 × 10−17

M

• r

e i n f

• i

n G . P e z z u l l

• t

a l k

The Mu2e experiment

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25 m TRANSPORT SOLENOID

• π decay to µ
• Selection and transportation of low momentum µ-

DETECTOR SOLENOID

• Capture µ on the Al target
• Momentum measurement in the tracker and energy reconstruction with calorimeter
• CRV to veto cosmic ray events

PRODUCTION SOLENOID

• Protons hitting the target and producing mostly π
• Graded magnetic field reflects slow forward π

Calorimeter requiremens

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High acceptance for reconstructing energy, time and position of signals for:

• Particle Identification: e/µ separation à reject µ background
• Improve the track pattern recognition
• Standalone trigger

Calorimeter requirements

• energy resolution σE/E <10%
• timing resolution σ(t) < 500 ps
• position resolution < 1 cm
• Work in vacuum @ 10-4 Torr
• 1 T Magnetic Field

Crystals coupled with Silicon PhotoMultipliers(SiPM)

• Light Yield(photosensor)>20 pe/MeV
• Fast signal for pileup and timing
• Survive an high radiation

environment − Total Ionizing Dose (TID) of 90 krad/5 year for crystal − TID of 75 krad/5 year for sensor − 3x1012 n/cm2 for crystal − 1.2x1012 n/cm2 for sensor @ 105 MeV

Calorimeter Design

• Readout: 2 UV-extended SiPMs/crystal
• Analog FEE and digital electronics located

in near-by electronics crates

• Source for energy calibration
• Laser system for monitoring gain stability

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2 disks each with 674 undoped (34x34x200)mm3 square pure CsI crystals

Mu2e EMC: MC performance

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The calorimeter energy resolution is estimated taking into account signal and predominant background, as the difference of the conversion electron energy and the cluster energy.

FWHM/2,35 = 3.8 ± 0.1 MeV

Longitudinal Response Uniformity LRU=RMS/MEAN of LO along the crystal

The overall resolution depends on the crystal features

Crystal preproduction

• Optical properties:

− 100 pe/MeV with PMT readout − LRU < 5% − Fast/Total>75%

• Radiation hardness

− Smaller than 40% LY loss @ 100 krad − Radiation Induced Noise <0.6 MeV

• 24 crystals from three different vendors: SICCAS, Amcrys, Saint Gobain
• 22Na source to test crystal properties along the crystal axis
• Crystals coupled in air to an UV-extended PMT

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Selected vendors: SICCAS and Saint Gobain

SiPM preproduction

• 2 arrays of three 6x6 mm2 SiPMs
• total active area of (12x18) mm2
• 50 µm pitch
• Photon Detection Efficiency (@ 315 nm)>20%
• The series configuration à narrower signals

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• 150 Pre-production SiPMs (3×50 Mu2e SiPMs

from Hamamatsu, SensL and AdvanSiD):

• 3×35x6 cells fully characterized (Vop, G, Idark, PDE)
• 1 sample/vendor exposed up to a fluence of

8.5×1011 n1MeVeq/cm2 (@ 20 °C)

• Mean Time To Failure estimated by operating 15

SiPM at 50 °C for 3.5 months à MTTF > 0.6x106 h

]

2

/cm

1MeV

Integrated flux [n 100 200 300 400 500 600 700 800

9

10 I [mA] 10 20 30 40 50 60

~ 150 V

Selected vendor: Hamamatsu

• Hamamatsu
• SensL
• AdvanSiD

6x6 mm2

t wrapped

Module-0

• Goals:
• Test the performances
• Test integration and assembly

procedures

• e- beam (60-120 MeV), May 2017
• Orthogonal and 50° incidence

(CE)

• Operate under vacuum, low

temperature and irradiation tests

• Readout: 1 GHz CAEN digitizers (DRS4

chip), 2 boards x 32 channels

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Large size prototype: 51 crystals coupled to 102 sensors

Entries 1190 / ndf

χ 26.39 / 27 η 0.04812 ± 0.07021 σ 0.202 ± 6.572 µ 0.38 ± 88.12 N 33.8 ± 1108

E [MeV] 20 40 60 80 100 120 Entries/ 1 MeV 10 20 30 40 50 60 70 80 90

Entries 1190 / ndf

χ 26.39 / 27 η 0.04812 ± 0.07021 σ 0.202 ± 6.572 µ 0.38 ± 88.12 N 33.8 ± 1108

DATA MC

Entries 1902 Mean 87.87 Std Dev 7.702 / ndf

χ 23.5 / 12 η 0.0846 ± 0.2011 σ 0.199 ± 4.723 µ 0.29 ± 89.48 N 50.2 ± 1552

E [MeV] 20 40 60 80 100 120 Entries/1 MeV 20 40 60 80 100 120 140 160

Entries 1902 Mean 87.87 Std Dev 7.702 / ndf

χ 23.5 / 12 η 0.0846 ± 0.2011 σ 0.199 ± 4.723 µ 0.29 ± 89.48 N 50.2 ± 1552

DATA MC

Module-0: Energy resolution

• Single particle selection
• Calibration:
• Cosmic
• Beam

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Orthogonal incidence

Orthogonal Run: σE~ 5% Tilted Run : σE~ 7.5% @ Ebeam = 100 MeV

50° incidence

0.05 0.06 0.07 0.08 0.09 0.1 0.11 [GeV]

dep

E 1 2 3 4 5 6 7 8 9 10 [%]

dep

/E σ

/ ndf

2

χ 0.8783 / 2 a ± 0.6 b 0.02913 ± 0.2732 c 0.2705 ± 4.05 / ndf

2

χ 0.8783 / 2 a ± 0.6 b 0.02913 ± 0.2732 c 0.2705 ± 4.05 / ndf

2

χ 3.142 / 3 a ± 0.6 b 0.045 ± 0.3747 c 0.3911 ± 5.863 / ndf

2

χ 3.142 / 3 a ± 0.6 b 0.045 ± 0.3747 c 0.3911 ± 5.863

Orthogonal Beam ° Beam @ 50

σE E = a √ E ⊕ b E ⊕ c

Energy [MeV] 10 20 30 40 50 60 70 80 90 100 [ns]

T

σ 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5

/ ndf

2

χ 3.081 / 5 a 0.2043 ± 8.906 b 0.007005 ± 0.118 / ndf

2

χ 3.081 / 5 a 0.2043 ± 8.906 b 0.007005 ± 0.118 / ndf

2

χ 5.155 / 3 a 0.1425 ± 6.858 b 0.004349 ± 0.0911 / ndf

2

χ 5.155 / 3 a 0.1425 ± 6.858 b 0.004349 ± 0.0911

• Hamamatsu
• Beam at 0

Cosmic Rays - Hamamatsu

• SensL
• Beam at 50

Cosmic Rays - SensL

TimeHist

/ ndf

106.6 / 20 0.0444 0.6526 1.21 17.12 0.7 216.6 N 640.2 8782 t [ns] 200 400 600 800 1000 Amplitude [mV] 50 100 150 200 250 300 350

TimeHist

/ ndf

106.6 / 20 0.0444 0.6526 1.21 17.12 0.7 216.6 N 640.2 8782

Χ η σ μ

Module-0: Single Sensor Time resolution

• Log Normal fit on leading edge
• Constant Fraction method used CF = 5%
• Comparison between 1GHz (TB sampling) and

200 MHz (Mu2e sampling) shows no deterioration in the resolution

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Entries 1531 / ndf

19.56 / 15 Constant 7.6 240.9 Mean 0.0049 0.1664 Sigma 0.0035 0.1874

t [ns] 1.5 1 0.5 0.5 1 1.5 Entries / (0.075 ns) 50 100 150 200 250

Entries 1531 / ndf

19.56 / 15 Constant 7.6 240.9 Mean 0.0049 0.1664 Sigma 0.0035 0.1874

σ (T1+T2)/ ! ~ 132 ps @ Ebeam = 100 MeV

σt = a E ⊕ b

Central Crystal

Δ

Central Crystal

QA room @ FNAL for production

• QA tests started on March 2018
• ~1000 SiPMs tested (25% of the total number)
• ~300 crystals (23% of the total number)

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Motor support CS137holder behind a Lead shielding 2 SiPMs per crystal 6 crystals tested at the same time

CsI holder SiPM Power LED driver

UV PMT

Diffusing sphere (Gain measurement)

Na22 + tagger

Motor on the back moves source + tagger + tagger

Motor for Tyvek cap RotaKng motor (to test a and b sides) TranslaKon motor (CsI & sphere)

CsI RIN CsI QA CsI dimensional test SIPM dimensional test SiPM QA SiPM MTTF

First QA results - Crystal

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q 99% of crystals satisfy the specifications concerning

• ptical properties

q Some problems to satisfy the mechanical specs

RIN (MeV) 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Entries 2 4 6 8 10 12 14 16

SICCAS Saint Gobain

Y (mm) 33.6 33.8 34 34.2 34.4 Entries 20 40 60 80 100 Z (mm) 33.6 33.8 34 34.2 34.4 Entries 10 20 30 40 50 60 70 80 X (mm) 199.6 199.8 200 200.2 200.4 Entries 10 20 30 40 50 60

x [mm] y [mm] z [mm] Entries Entries Entries Entries Entries Entries

Dimensional test

Npe/MeV LRU σ/μ Fast/Total

Optical test

RIN [MeV]

RIN test

Entries

First QA results -SiPMs

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q 96% of SiPMs satisfy the Mu2e requirements q Performances after the irradiation OK

38 rejected sipms (3.4%)

• RMS Idark [%]
• RMS Vbr [%]

MTTF> 4×106 hours

σ

• Gain x PDE

38 rejected SiPMs(3.4%) T=20°C T=20°C

20°C 0°C

• 10°C

Summary

• Mu2e calorimeter is a state of the art Crystal Calorimeter with

energy (<10 %) and timing (< 500 ps) resolution @ 100 MeV.

• Preproduction of crystals and SiPMs completed
• Un-doped CsI crystals perfom well
• Mu2e SiPMs performances in agreement with requirements
• Large size prototype tested with e- beam in May 2017
• Good time(~100 ps) and energy resolution(~8%) achieved @ 100 MeV
• Calorimeter production phase started in March 2018
• Detector installation expected to begin in 2020

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spares

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Vendor Comparison -time

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Small prototype TB

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• Small prototype tested @ BTF (Frascati) in April 2015, 80-120 MeV e-
• 3×3 array of 30×30×200 mm2 undoped CsI crystals coupled to one Hamamatsu SiPM

array (12x12) mm2 with Silicon optical grease

• DAQ readout: 250 Msps CAEN V1720 WF Digitizer

FOTO matrice

Good agreement between the DATA and MC Log-normal fit

JI JINST 12 12 (2017) 2017) P05007 05007

Single channel slice test

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SG SG cr crystal + H + Hamamatsu Si SiPM + F + FEE Optical coupling in air.

• 22

22Na

Na s sou

• urce
• TRG: small scintillator readout by a PMT
• Study distance effect for air-coupling

Time [ns]

80 100 120 140 160 180 200 220

Amplitude [mV]

5 10 15 20 25

Hamamatsu 4 - DIstance from Crystal 0 mm 1 mm 2 mm

~ 10% loss

• Co

Cosm smic ra ray te test à 2 SiPMs readout

• TRG: crystal between 2 small scintillators

2 SiPMs

Single channel – CR test

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• TRG time resolution ~ 170 ps
• Constant fraction method used
• Pulse height correction applied

(slewing)

After jitter subtraction: Si SiPM 1 1 – σT ~ 3 ~ 330 ps ps Si SiPM 2 2 – σT ~ 3 ~ 340 ps ps T( T(SiPM1 - Si SiPM2) 2)/2 2 à ~ 2 ~ 215 ps ps @ ~ 23 MeV energy deposition (MIP energy scale from Na22 source peak) Ti Timing re result we well co compares wi with h ol

• ld te

tests: à Reduced light output/SiPM (22 vs 30 pe/MeV) à 2 SiPMs/crystal à LY of 44 vs 30 à 215 ps (now) vs 250 ps (old).

Entries 727 Constant 6.2 ± 133.6 Mean 0.0161 ± 0.1234 Sigma 0.012 ± 0.429

Time [ns]

• 3
• 2
• 1

1 2 3 Entries / 25 ps 20 40 60 80 100 120 140

Entries 727 Constant 6.2 ± 133.6 Mean 0.0161 ± 0.1234 Sigma 0.012 ± 0.429

SiPM 1 - SiPM 2 Σ

Particle Identification

With a CRV inefficiency of 10-4 an additional rejection factor of ~ 200 is needed to have < 0.1 fake events from cosmic in the signal window

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A rejection factor of 200 can be achieved with ~ 95% efficiency for CE

Calorimeter Calibration

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• Liquid source FC 770 + DT generator: 6 MeV + 2 escape peaks
• Laser system to monitor SiPM performance

Calorimeter trigger

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• Calo info can provide additional trigger capabilities in Mu2e:
• Calorimeter seeded track finder
• Factorized into 3 steps: hit pre-selection, helix search and track fit
• ε ~ 95% for background rejection of 200
• Standalone calorimeter trigger that uses only calo info
• Ε ~ 65% for background rejection 200

Calorimeter seeded track finder

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Calorimeter Mechanics

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Background for Mu2e

• Intrinsic physics background:
• Muon Decay in Orbit (DIO)à end point @ signal energy
• Radiative Muon Capture àπN à γN’; γàe+e-
• Neutron from muon nuclear capture
• Proton from muon nuclear capture
• Beam related backgrounds:
• Radiative Pion Capture (RPC)
• Beam electron
• Muon decay in flight
• Neutron
• Antiprotons producing pions when annihilating in the target
• Cosmic rays

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DIO background

• Electron energy distribution

from the decay of bound muons follows a modified- Michel spectrum:

• The Michel spectrum is

distorted by the presence of the nucleus and the electron can have an energy similar to the one of CE if neutrino are almost at rest àTo separate DIO endpoint from CE line Mu2e needs an high Resolution Spectrometer

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(Econv - Ee)5

Minimizing prompt background

• Prompt backgrounds arise from the interaction occurring at the

stopping target

• Radiative Pion Capture ( τπ

Al = 26 ns)

• π/µ decay in flight
• Muonic atomic life>> prompt background
• Narrow pulsed proton beam
• Delayed signal window starting 700 ns after the initial proton pulse
• Out-of-time proton suppressed by O(1010)

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π−N → γN ∗ → e+e−N ∗