Lepton Flavor Violation: present and future experiments - 1 LNF- - - PowerPoint PPT Presentation

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Lepton Flavor Violation: present and future experiments - 1 LNF- - - PowerPoint PPT Presentation

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Lepton Flavor Violation: present and future experiments - 1 LNF- May, 11ht 2008 F.Gatti University and INFN of Genoa First experiment: E.P.Hincks and B. Pontecorvo (1948) At that time the motivation for a such searches was motivated

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SLIDE 1

Lepton Flavor Violation: present and future experiments - 1

LNF- May, 11ht 2008 F.Gatti University and INFN of Genoa

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SLIDE 2

First experiment: E.P.Hincks and B. Pontecorvo (1948)

At that time the motivation for a such searches was motivated by the general study

  • f m decay

ne, nm and e spectrum not discoverd

m was supposed to decay in e + ne (Yukawa)

Lead Degrader target PR 73 (1948)

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SLIDE 3

History and future of FLV m decay searches

Cosmic m stopped p m beams

MEG (2010) Mu2e PRIME

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SLIDE 4

e+ m+ g qeg = 180°

Ee = Eg = 52.8 MeV

Te = Tg

signal

m  e g

background

physical

m  e g n n

(radiative decay)

e+ m+ g n n accidental m  e n n m  e g n n ee  g g eZ  eZ g e+ m+ n n g

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SLIDE 5

The last of a series

Exp./Lab Year DEe/E

e

(%) DEg /Eg (%) Dteg (ns) Dqeg (mrad ) Stop rate (s-1) Duty cyc.(% ) BR (90% CL) SIN 197 7 8.7 9.3 1.4

  • 5 x 105

100 3.6 x 10-9 TRIUMF 197 7 10 8.7 6.7

  • 2 x 105

100 1 x 10-9 LANL 197 9 8.8 8 1.9 37 2.4 x 105 6.4 1.7 x 10-10 Crystal Box 198 6 8 8 1.3 87 4 x 105 (6..9) 4.9 x 10-11 MEGA 199 9 1.2 4.5 1.6 17 2.5 x 108 (6..7) 1.2 x 10-11 MEG 201 0.8 4 0.1 5 19 2.5 x 107 100 1 x 10-13

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SLIDE 6

Conceptual design of MEG

1m e

+

  • Liq. Xe Scintillation

Detector

g

Drift Chamber

  • Liq. Xe Scintillation

Detector

e

+

g

Timing Counter Stopping Target Thin Superconducting Coil Muon Beam Drift Chamber

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SLIDE 7

Actual MEG configuration

 Liquid Xenon

Calorimeter

 Drift Chambers  Timing counters  COBRA Magnet

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SLIDE 8

PSI-beam

The most powerful continuous machine in the world;

Proton energy 590 MeV;Power 1.1 MW;n ominal operational current 2.0 mA.

27.7 MeV/c muons from p stop at rest (surface muons);

Provides a DC beam of  108 m/s.

Primary proton beam

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SLIDE 9

PSI-Beam

The beam elements:

Wien filter for m/e separation

Degrader to reduce the momentum stopping in a 150 mm CH2 target

Transport Solenoid to couple beam with COBRA spectrometer

Rm (total) 1.3*108 m+/s

Rm (after W.filter & Coll.) 1.1*108 m+/s

Rm (stop in target) 6*107 m+/s

Beam spot (target) s  10 mm

m/e separation 7.5 s (12 cm)

  • Maximum beam stop rate  108 m/s,

but we will use only 3 x 107 because

  • f accidental background

(proportional to (muon rate)2 )

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SLIDE 10

COnstant Bending RAdius- COBRA- magnet

COBRA spectrometer was designed to provide a graded magnetic field whose flux lines have large divergence also in the center (1.27 T at the center and 0.49 T at both ends). Positrons with the same absolute momentum follow trajectories with a constant projected bending radius, independent on the emission angles over a wide angular range.

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SLIDE 11

COBRA-magnet

Constant bending radius independent of emission angles

High pT positrons quickly swept out Gradient field

Uniform field

Gradient field

Uniform field

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SLIDE 12

Target and positron tracking

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SLIDE 13

Positron Tracking

Sixteen drift chambers (ten degrees interval), each one equipped with 18 staggered wires and cathodic kapton foils.

Wires: r , f coordinates

Cathode: z coordinate

s(X,Y) ~ 200 mm

Chamber gas: He-C2H6 mixture

Vernier pattern to measure z- position made of 15 mm kapton foils(charge division)

s(Z) ~ 300 mm

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SLIDE 14

TC Final Design

  • A PLASTIC SUPPORT

STRUCTURE ARRANGES THE SCINTILLATOR BARS AS REQUESTED

  • THE BARS ARE GLUED

ONTOTHE SUPPORT

  • INTERFACE ELEMENTS

ARE GLUED ONTO THE BARS AND SUPPORT THE FIBRES

  • FIBRES ARE GLUED AS

WELL

  • TEMPORARY ALUMINIUM

BEAMS ARE USED TO HANDLE THE DETECTOR DURING INSTALLATION

  • PTFE SLIDERS WILL

ENSUREA SMOOTH MOTION ALONG THE RAILS

PM-Scintillator Coupling Scintillator Housing BC404-Scintillator slab Main Support Ladder Board & cabling PM APD APD F.E. Board Scintillating Fibers APD Cooled Support

Positron timing- Timing Counter

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SLIDE 15

Positron timing- Timing Counter

Two layers of scintillation counters placed at right angles with each other.

Outer layer: scintillator bars, mainly devoted to timing measurement.

Two sections of 15 bars each, read by PMTs, before and after DCH system.

Inner layer: scintillating fibres, devoted to provide trigger and z information.

5 x 5 mm2 fibres, read by APDs.

Measurements of TC bars timing resolution in dedicated test beams at several positions and impact angles at BTF in Frascati

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SLIDE 16

Limitations due to the B field

PMT TTS, gain as a function of magnetic field and orientation angles

Scintillation time, attenuation length, PMT-bar coupling

Fine-mesh PMTs show good timing properties even in magnetic field up to 1 Tesla

Gain behaviour is related to the orientation angle – best for q = 20-30°

A high number of photoelectrons is necessary to be in a 100 ps resolution range

5 10 15 20 20 40 60 80 100 120 140 160 180 200

s (ps) geometric angle (degrees)

1100 photoelectrons 300 photoelectrons 60 photoelectrons

Inner position PMT

5 10 15 20 20 40 60 80 100 120 140 160 180 200

Outer position PMT

1100 photoelectrons 300 photoelectrons 60 photoelectrons

0.0 0.2 0.4 0.6 0.8 1.0 1.2 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

time resolution  25 ps magnetic field (T)

q =0° q =20° q =30°

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SLIDE 17

B field and He atmosphere

Optimization of angular position of PMs

Protecting Bag with thin low diffusivity plastics (EVAL T)

Gas Flushing 1 atm He4 COBRA BORE N2Bag

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SLIDE 18

Experimental constraints: re- shaping the TC elements

Scintillator Cross Section 5mm PM outer Diameter :52 mm

PM active diameter: 39 mm

19º 22º 8.5º

From COBRA center

105 cm 11º 25 cm B B

0.75 T 1.05 T

Sectional view

  • Long. view

5mm

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SLIDE 19

Testing single element at Beam Test Facility (LNF)

Apparatus for 2-axis + longitidinal sample movements Typical BTF beam performance

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SLIDE 20

Single element timing resolution

20 40 60 80 100 2160 2180 2200 2220 2240 79.1 ps @ FWHM 25 50 75 100 3345 3360 3375 3390 3405 3420 108.3 ps @ FWHM

MCA channel number

counts/6.33 ps

70 80 90 100 110

  • 40
  • 30
  • 20
  • 10

90 100 110 120 130

time resolution @ FWHM (ps)

90.0° 65.0° 53.5° 40.0°

BC 404

distance from the

BC 408

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SLIDE 21

Timing performance with some

  • ther ToF

  • 1. B. Adeva et al., Nucl. Instr. and

Meth A 491 (2002) 41.

  • 2. G. Palla et al., Nucl. Instr. and
  • Meth. A 451 (2000) 406.

  • 3. V. Sum et al., Nucl. Instr. and
  • Meth. A 326 (1993) 489.

  • 4. M. Baldo-Ceolin et al., Nucl.
  • Instr. and Meth. A 532 (2004)

548.

  • 5. Y. Kubota et al., Nucl. Instr.

and Meth. A 320 (1992) 66.

  • 6. M. Baldo Ceolin et al., Nuovo

Cimento 105A (1992) 1679.

  • 7. G.C. Bonazzola et al., Nucl.
  • Instr. and Meth. A 356 (1995)

270.

  • 8. S. Benerjee et al., Nucl. Instr.

and Meth. A 269 (1988) 121.

  • 9. E.S. Smith et al., Nucl. Instr.

and Meth A 432 (1999) 265

10 J.S. Brown et al., Nucl. Instr. and Meth. 221 (1984) 503. Scintil. type PMT LxWxT (cm) s (ps) Ref . BC420 R1828-01 40x7x2.2 123 1 BC408 R3478 12-48x1-1.25x1.5-2.4 80 2 BC408 H1949 200x8.5x5 110 3 BC408 XP2020 180-250x21x2.5 160 4 BC408 XP2020 280x10x5 139 5 NE110† XP2020 210-300x21x2 300 6 NE110† XP2020 300x9.3x4 170 7 BC408 XP2020 305x10x5 110 8 NE Pilot F‡ XP2020 317.5x15.6x5.1 170 9 BC408 XP43132B/D1 32-450x15-22x5.1 163 10 BC404 R5924 80x4x4 40

  • ur
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SLIDE 22

Final detector, test at BTF (LNF) and run performance

DTD Time resolution s = 52 ps (with low z-cuts) Run Conditions

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SLIDE 23

APD readout of scintillating fibers detectors

VF3 R8 33 0 R7 13k

+
  • +
DIS

U2 OPA847 T1 2N3955 C3 10 0p V4 5 R4 10 R1 10 0k C4 1p R6 100k R5 33 0 R3 10

+
  • +
DIS

U1 OPA847 IG1 V3 400 R2 10 0k C2 80 p C1 10n V2 5 V1 5 T2 2N3955

2 x MMBF4392 2 x OPA847 145000 e- 1ns DIS

  • New solution with APD and scintillating fibers:

1. High QE of APD 2. Good performances, not influenced by magnetic field 3. Optimum matching APD-fiber 4. Better spatial resolution (5mm) 5. Lower cost per channel (total 512 channels) 6. Fast - Low noise electronics for analog signals (ENC = 1500e) custom made 7. Digital output with hitmap encoding

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SLIDE 24

Avalanche Photo-Diodes (APD)

Dark noise Total noise of illuminated APD including Shot niose, excess noise, photon noise Excess noise factor at M=500 x= 0.5

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SLIDE 25

APDs production

I dark vs H.V. Temperature 20°C

1.00E-03 1.00E-02 1.00E-01 1.00E+00 1.00E+01 2.50E+02 3.00E+02 3.50E+02 4.00E+02 4.50E+02 5.00E+02

H.V. (Volts) I Dark @ 10Mohm (Volts) I dark vs H.V. Temperature 20°C

1.00E-03 1.00E-02 1.00E-01 1.00E+00 1.00E+01 2.50E+02 3.00E+02 3.50E+02 4.00E+02 4.50E+02 5.00E+02

H.V. (Volts) I dark@ 10Mohm (Volts)

APDJA0304_20ID_M APDJA0316_20ID_M APDJA0305_20ID_M APDJA0288_20ID_M APDJA0296_20ID_M APDJA0302_20ID_M APDJA0307_20ID_M APDJA0312_20ID_M APDJA0308_20ID_M APDJA0309_20ID_M APDJA0311_20ID_M APDJA0295_20ID_M APDJA0289_20ID_M APDJa0290_20ID_M APDJA0292_20ID_M APDJA0294_20ID_M APDJA0307_20ID_M

I=50 nA Selected samples from Hamamatsu MEG APD s Irradiatted samples of CMS

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SLIDE 26

Fiber detector under run consitions

8 Channels analog sum 8 Channels analog sum 8 Channels analog sum

Signal of 8+8 Interleaved fibers

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SLIDE 27

Liquid Xe Calorimeter -XEC

Xe + radiation Xe* Xe+ Xe+ + Xe Xe2+ + e- Xe + Xe** Xe** → Xe* Xe* + Xe Xe2* 2Xe + hv

excitation ionization excimer l=175nm, 14 nm FWHM

Xe Xe Xe Xe e e e

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SLIDE 28

XEC

Compact

Z=54, ρ=2.95 g/cm3 (X0=2.7 cm), RM=4.1 cm @ T=165 K

High light yield

L.Y.=42000 phe/MeV ≈ 0.7 LY(NaI) for m.i.p.’s

Fast

t1=4ns, t3=22ns, trec=45ns

Particle ID

tg  2 ta

L.Y.a= 1.2 x LYmip

n = 1.65 ( nquartz)

 good optical coupling with PMTs

No self-absorption (λAbs=∞)

 position-independent energy response  homogeneous calorimeter

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SLIDE 29

First test made in 100l prototype

40 x 40 x 50 cm3, 100 l LXe

(same depth, 1/10 of the final volume)

the world-wide largest at that time

Equipped with 240 PMTs

(HAMAMATSU R6041+R9288TB)

  • K-Cs-Sb photocathode

  • Quartz window (suited for

VUV)

Gas purification system

(getter+Oxysorb) to keep impurity

content < 1ppb

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SLIDE 30

100 l prototype

Demonstrated: high energy and timing resolution and absorption length >> 1m

s=125 ps

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SLIDE 31

Calibration of position reconstruction

Alpha sources electroplated onto 50 um wire  alpha rings

G XE L XE

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SLIDE 32

XEC

800 l of Liquid Xenon equipped with 846 PMTs; 9% W/4p; Only scintillation light; 19 X0 depth and 0.4X0 of front material. PMT quartz windows to match LXe scintillation UV spectrum

  • Liq. Xe

H.V.

Vacuum

for thermal insulation Al Honeycomb window PMT Refrigerator Cooling pipe

Signals filler

Plastic

1.5m

molecular filter pump

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SLIDE 33

TC calibration with 12 ps laser

 12 ps fwhm NYVO laser for TC-XEC

time calibration designed for MEG

TC Data s=54 ps 12 ps fwhm

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SLIDE 34

Calibration with (p,g)

 500 KeV CW generator excite Boron or Li

target at COBRA center,

Reacti

  • n

Peak energy s peak g-lines Li(p,g)B e 440 keV 5 mb (17.6, 14.6) MeV B(p,g)C 163 keV 2 10-1 mb (4.4, 11.6, 16.1) MeV

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SLIDE 35

TC-DC time relative timing

LXe charge

TC charge 11.6 MeV

11.6 MeV and 4.4 MeV coincident gamma’s

(small angular correlation)

4.4 MeV 11.6 MeV 4.4 MeV

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SLIDE 36

TC timing resolution stable

  • ver the full run
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SLIDE 37

TC – hit map before and after calibration

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SLIDE 38

XEC L.Y. increased over the RUN

 Continuous improvement of XEC L.Y.

(expected value 26.000 phe at 17.5 MeV)

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SLIDE 39

MC of gamma spectrum

Red: Radiative decay

Green: Annihilation In Flight

Black: Cosmics

Blue: Total (including pile- up) Energy (MeV) Rm = 3.2 x 107 s-1

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SLIDE 40

Data-MC

Data (Blue Points): Beam @ 3.2 x 107 m s-1, threshold  45 MeV

MC (Black line): full background simulation. Absolute rate reproduced

Pile-up subtracted by charge distribution; cosmics rejected.

Final pile-up rejection by using waveforms (not here).

Energy (MeV) Energy (MeV)

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SLIDE 41

Radiative Decay in the timing sginal

Blue: no kinematical bound; Red: kinematical bound applied.

Kinematical bound has no effect on signal and a factor 2.5 reduction on bck 100 ps 25 ps

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SLIDE 42

MEG expectations

 )

0.6 ε 0.7 0.9 ε 0.9 ε

γ 3 sel e

 =  

0.09 4π Ω s μ 10 0.3 R s 10 2.6 T

8 μ 7

=  =  = Cuts at 1,4FWHM

Detector parameters

sel e μ sig

   p

g 

  W    = 4 R T BR N

Signal

1 

         W   =

sel e μ

   p

g

4 R T SES

 410-14 Single Event Sensitivity

corr

BR

2

     BR R E E θ t

2 2 acc μ e γ eγ eγ

Δ Δ Δ Δ

 310-14  310-15 Backgrounds Upper Limit at 90% CL BR (meg)  110-13 Discovery 4 events (P = 210-3) correspond BR = 210-13