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Alessandro Bravar
Journée de réflexion DPNC18 June ‘12
Lepton Flavor ViolationLepton Flavor Violation3e @ PSI3e @ PSI
UniGE @ PSI
Lepton Flavor Violation
The 3e experiment ( → eee)
Sci-Fi ToF Tracker
UniGE planned contributions
Lepton Flavor ConservationLepton Flavor ConservationOrigin of Lepton Flavor Number / Conservation the neutrino produced along with a + (e) in + decay, when interacting with matter will produced only s (es), → is different from e ; → Lepton Flavor (Family) Conservation
Neutrino oscillations, however, violate this ansatz:after traveling some distance the can produce a (OPERA) or an e (T2K)
Flavor Conservation in the charge lepton sector:Processes like A → e A
→ e + → e e e have not been observed yet.
The mechanism and size of LFV remain elusive.
In the quark sector the situation is quite different:quarks decay, mix, … only the baryonic number is conserved.However Flavor Changing Neutral Currents (FCNC) have not been observed.
Lepton Flavor Violation in Lepton Flavor Violation in → eee eee
neutrino oscillations SUSY exotic particles
Current experimental limitBR(→ eee) < 1012 (90% c.l., SINDRUM 1988)
This experiment (3e @ PSI)BR( → eee) < 1015 (90% c.l. exclusion) phase I (2015 – 2017)
BR( → eee) < 1016 (90% c.l. exclusion) phase II (2018 – 2020)BR( → eee) = 3 1016 (5 discovery)
Explore physics up to the PeV scaleComplementary to direct searches at LHC
LFV in the Standard ModelLFV in the Standard Model
process is heavily suppresseddue to the small mass differenceof neutrinos (m2 ~ 10-3 eV2) !
BR ( → eee) < 1050
→ measurement not affected bySM processes
Beyond the Standard ModelBeyond the Standard ModelLFV addresses issues like origin of flavor
neutrino mass generation CP violation
LFV predicted by many BSM models: Supersymmetry Higgs triplet models Little Higgs models New heavy Vector Bosons (Z’) Leptoquark (GUT models) Extra dimensions
In many models sizeable andtherefore observable LFV effectsare expected:
BR( → eee) ~ 1012 possible(just beyond SINDRUM limit)
LFV Searches : Current SituationLFV Searches : Current SituationThe best limits on LFVcome from PSImuon experiments
→ eee BR < 1012
SINDRUM 1988
+ Au → e + Au BR < 7 1013
SINDRUM II 2006
→ e + BR < 2.4 1012
MEG 2011
BR( → eee) / BR( → e) ~ o(em/)
BR(A → eA) / BR( → e) ~ o(em/)
SINDRUMSINDRUM II
MEG
Comparison Comparison → e e and and → eee eeeEffective charge LFV Lagrangian (“toy” model) (Kuno and Okada)
effective mass scale (including coupling)
– “contact” vs “loop” amplitude contribution (parameter of “toy” model)
→ e
1 PeV
+
UniGE @ PSI (MuLAN and FAST)UniGE @ PSI (MuLAN and FAST)Measurement of the lifetime and GF
“search” for W propagator effects on GF
MuLAN
FAST
Mu3e @ PSIMu3e @ PSIan experiment to search for Lepton Flavor Violation in e e e
using the most intense surface muon beam (p ~ 28 MeV/c) in the worldsensitivity ~10-16 (PeV scale !) observe ~1017 decays (over a reasonable time scale) rate ~ 2 109 decays / sec (1 y ~ 107 sec)
200 M HV-MAPS (Si pixels w/ embedded ampli.) channels10 k ToF channels
acceptance ~ 70% for m → eee decay (3 tracks!)
B ~ 1 – 2 T
surface
p ~ 28 MeV/c
How to Find How to Find → eee decays eee decays50 nsec time frames (Si “resolution”) → 100 decays @ 2 109 stops / sec
challenge : isolate → eee events
t ~ few 100 psTime of Flight ~ few 100 ps
BackgroundsBackgrounds
irreducible backgrounds accidental backgrounds (pileup)
signal
0~
0
tracks
i i
i i
t
mE
p
BR(→ eee) = 3.4 105
precise timing (ToF): t ~few 100 psprecise kinematics (p and E resolution):
p / p < 0.5% (i.e. ~ 100 keV/c) precise vertexing: x ~0.1 mm
to suppress backgrounds
Silicon Pixel Detector HV-MAPSSilicon Pixel Detector HV-MAPSHigh Voltage Monolithic Active Pixel Sensors
< 50 m thicknessactive sensorsstandard CMOS processlow noiseradiation tolerantlow power
~ 20 20 m2 pixels200 M channels
transistor logic embedded in N-well
Heidelberg
The ToF TrackerThe ToF Tracker
3000 Sci-Fi channels 250 m fibers readout with Si-PM arrays
6000 scint. tiles readout with Si-PMs
rate ~ several MHz / Sci-Fi channels
time resolution ~ few 100 ps
readout with wave-form digitizers real time analysis pileup separation background rejection
huge data rate !
~12 cm diameter24 ribbons 16 mm wide
Hamamatsu MPPC array 5883
250 effective pitch
UniGE + ?
Sci-Fi ArraysSci-Fi Arrays5 staggered layersof 250 m fibers double cladding Kurarayscintillating fibers
SCSF-81M peak ~ 437 nm decay ~ 2.4 ns att > 3.5 m
minimize thickness to reduce multiple scatteringminimal thickness for good time resolution (light output)effective thickness ~ 1 mm (+ glue and / or TiO2 paint and / or support structure)
track “topologies”
light propagation in multicladding fibers
Si-PMs DemystifiedSi-PMs Demystified
ADC ch.
distance between peaks is constant -> gain from ADC spectra
gain vs. HV linearin +-0.5 V window
effect of cross talk
part of Labo III program(A. Bravar and S. Orsi)
peak #15
Si-PM Photo Detection EfficiencySi-PM Photo Detection Efficiency
Hamamatsu KETEK
max (SciFi) ~ 440 nm
P.D.E. ~ 30 % P.D.E. ~ 60%
detect 2 more photons → gain ~ 2 in time resolution
SciFi SciFi
55-60%
PDE = geometrical QE Geiger
(50–70 %)(60–90%)
Read-OutRead-Outamplifier ~10x flash ADC
or SCA FPGA
CFD algorithm(real time)
optical link
Si-PM
> 1 GHz> 10 -12 bit
several MHz rate → very fast amplifier rise ~ 1 nsec decay ~ 10 nsec(noise not critical because read-out with WFD)
digitizer: start with DRS4 switched capacitor array (phase I) and later DRS5 (phase II)SCA time stretcher: GHz sampling → MHz readout
best timing can be obtained using waveform digitizing(e.g. real-time algorithms simulating the functioning of a constant fraction discriminator)
huge data rate → processing of DRS information in real time (on board)
data reduction (hit processing and matching) also in real time
UniGE + PSI
DRS4 @ PSI DRS4 @ PSI http://drs.web.psi.ch
DRS4 Evaluation Board4 channels 1 – 5 GSPS
12 bitUSB power
S. Ritt
again part of Labo III equipment
Next Generation SCA (DRS5)Next Generation SCA (DRS5)
Short sampling depth Deep sampling depth
only short segments of waveform need fast sampling and readout
PSI (S. Ritt)
UniGE plansUniGE plansMu3e collaboration: Geneva, Heidelberg, PSI, Zurich, ETHZ, + …
Develop ToF system (SciFi and scintillating tiles) hardware (SciFi ribbons, Si-PMs, …) in coll. with UniZH electronics (amplifiers, DRS, firmware, …) in coll. with PSI digitizing electronics: possible synergy with NA61 and AIDA
Simulations and optimization of Mu3e detector, in particular ToF system in coll. with ALL
More concrete (next 6 months) - build SciFi array prototype and test / optimize for time resolution rate capabilities - develop fast amplifiers, readout based on commercial DRS electronics - develop (offline → real time) algorithms for DRS electronics - R&D on Si-PM PDE
FNS request: 1 PostDoc + 1 CanDoc
ADDITIONAL TECHNICAL STUFF
Late ’80s – Early ’90s (the beginning)Late ’80s – Early ’90s (the beginning)
first Position-Sensitive PMswith “crossed wires” anodebefore the advent of multi-anode PMs
16 x 16 wires (channels)delay line readout
RD-17 / FAROS
Sci-Fi arrays and Si-PMTsSci-Fi arrays and Si-PMTsHamamatsu MPPC 5883
alternative solutions single fiber readout
Zecotek linear array of 18 1mm2 MAPDs(CMS HCAL upgrade) green light !could use Hamamatsu Si-PMs
can couple (glue) Sci-Fi ribbon directlyto the photosensor+ direct mapping of the Sci-Fi array+ best optical transmission- limited sensor size
monolithic photosensor (no dead regions)blue light !
total surface ~ 10 mm2
note: this is max surface for Si-PM50 x 50 m2 pixels5 columns of pixels grouped in a single readout ch. instead of a single ch.effective readout pitch 250 m
How To Measure Best TimingHow To Measure Best Timing
J.-F. Genat et al., arXiv:0810.5590 (2008) D. Breton et al., NIM A629, 123 (2011)
Simulation with realistic noiseand best discriminators
beam measurements@ SLAC and FNAL
17 ps () can be achieved with waveform digitizing and 40 photoelectrons(no jitter from scintillator decay)
Switched Capacitor Array (DRS Chip)Switched Capacitor Array (DRS Chip)
Shift RegisterClock
IN
Out
“Time stretcher” GHz MHz“Time stretcher” GHz MHz
Waveform stored
Inverter “Domino” ring chain0.2 - 2 ns
FADC 33 MHz
The DRS5 DigitizerThe DRS5 Digitizer
coun
ter
latc
hla
tch
latc
h
writepointer
readpointer
digital readout
analog readout
trigger
FPGA
100 ps sample time. 3.1 ns hold time 2 times better timing resolutiondata driven readout(almost) dead-time-less waveform digitizing 2 MHz sustained event rate planned for 2013
S. Ritt