Transcript NuMass Experiment An Improved Limit on the Muon Neutrino

International Summer School on
Particle and Nuclear Astrophysics
in Nijmegen 2003
NuMass Experiment
An Improved Limit on the Muon
Neutrino Mass from Pion Decay in
Flight
Carmen-Miruna Anăstăsoaie
Alex Eduardo de Bernardini
Sven Lafèbre
Martin Vlček
NuMass will improve the value of the upper limit of the mass of the
muon neutrino.
Current limits:
m(ne) < 4.35 - 15 eV
< 23 eV
< 0.5 - 9 eV
Tritium b-decay endpoint
TOF spread from SN1987A
Double b-decay for Majorana n’s
m(nm) < 170 keV
p -> mn (stopping p’s)
m(nt) < 18.2 MeV
Inv. Mass of t -> n + hadrons (e+e- Colliders)
improvement by NuMass by order of 20 to m(nm) < 8 keV
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What is the aim of the project?
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History of the Muon Neutrino
Mass Limit
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verification of theoretical backgrounds
- neutrino mass generation mechanism
- complementary information to neutrino oscillation results
- neutrino decays understanding
- chiral left-right symmetry
improvement of the theoretical description of the Fermi constant
understand some loopholes in cosmology
- lack of dark matter
- limits to the density of Universe
minimal left-right model verification
some propagation phenomena related to supernova pulses
it is, after all, a fundamental constant !
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Why is this measurement so
important?
In a perfectly uniform magnetic field
any charged particle returns to origin
independent of B or p or angle
Uniformity is more important value of B
“origin”
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Highlights of the experimental
technique
Beam counter
p Injection
J-veto: restrict early
m‘s at large angles
J-cal: 2nd turn
electron id
24 g-2 calorimeters
restrict late decays
identify electron bkg
initial beam tuning
C-veto: restrict
incoming p’s
decay m
p orbit
p -> mn observed event by event
we will need SEB
S1
S2
Trigger
Hodoscope
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Highlights of the experimental
technique
NuMass will use the existing
G-2 Storage Ring in the BNL
facility at Brookhaven with
only minor modifications
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Highlights of the experimental
technique
S2
Embedded Scintillator:
2 mm Prescale Strips
Trigger pads
S1
Beryllium
Degrader
Silicon μ-strip
Detectors
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Highlights of the experimental
technique
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Endpoint structure
Expected distance
between first pass pion
and second pass muon
(in mm)
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Sources of background
J-Veto
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Beam-gas scatters
=> vacuum is 10-6 torr
Injected p (27 %)
=> rejected in embedded scintilators ΔT = 7
ns / turn slower
Injected e (12 %)
=> rejected in J-veto, calorimeter or
position, lose 1 MeV / turn
μ → enn
=> rejected by g-2 calorimeter
< 10-4 of good π-μ events
π → en => rejected by calorimeter in inner
J-veto
C-Veto
g-2 Cal’s
S1
S2
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run in dedicated mode or in conjuction with K-decay (E949)
or MECO experiment
another project may run nearly immediately after our
beamtime, there are only minor changes on beam
pure 2 body decay p -> mn, no model dependent
nuclear/atomic environment
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Advantages of NuMass
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Responsibilities
Beamline and Ring
SSD and readout electronics
Active Vetoes and Scint Trigger
Feedthrus and positioners
DAQ and g-2 electronics
Field Measurements
Orbital dynamics, Monte Carlo
Analysis
BNL
CERN, Minnesota
BU, Illinois, Tokyo IT
Tokyo IT, Heidelberg, BNL
Minnesota, BU
Yale, Heidelberg, BNL
Cornell, BNL, Yale, NYU,
Minnesota, BU
The team!
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Budget
$ 770k BNL
- modifications on G-2 and SEB
- improved sensitivity for the V1 beamline
instrumentation
- beam time
$ 330k CERN, Universities
- silicon detectors, degrader, active vetoes
- feedthrus, positioners
- electronics, DAQ
$ 1.1 M TOTAL COST
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Year 2000
build 2-SSD detectors plus removable degrader unit
build active vetos or simple prototype
write software for new electronics readout and integrate with g-2
Year 2001
install and test prototype detectors by running parasitically
understand the π-μ orbital parameters
test AGS/beamline modifications for slow extraction to g-2
build and test final silicon detector + degrader
Year 2002
commission slow extraction to g-2
run the experiment parasitically with E 949
Year 2003
dedicated experiment or further parasitic running to completion
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Scheduling
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Thank you for your attention ...
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Neutrino oscillation
Neutrino oscillation experimental results are theoretically dependent.
Some effects surrounding the standard formulation of neutrino
oscillation phenomena:
(flavor) quantum
number oscillation
existence of sterile
neutrino
chiral oscillation
Δm2
DIRECT !!!
p -> mn
Neutrino oscillation
I’m
understanding
of the mixing angles
Dirac formulation
of neutrino oscillation
matter effect
wave packet
description
nm
If you believe atmospheric neutrino result:
nm => nt with only Dm2~.002
Then this experiment reduces the t neutrino mass limit
by 3 orders of magnitude!
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Neutrino oscillation
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T0
J-Veto
Inflector
Flash Counter
Pion on orbit
Muon hits J-Veto
on 1st turn
pion 2nd time around
collimator
Degrader
pion => pion
residual profile
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Some background
configurations
p -> e n
p -> mn
J-Calorimeter
g-2 Calorimeters
5 mm endpt (q=70 MeV/c)
SR shrinks it 2 mm
m -> enn
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Cross section of g-2
superconducting magnet
Contours every 1 ppm of
field gradient represents
lines every 1.5 μTesla
Magnetic field is 1.45 Tesla
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Cross section of the field
E949 Running Conditions
E952 Parameters
2.8 x 106 p+ into g-2 ring/TP
5.4 x 1012 p+ for an 8 keV result
25 Gev protons
70 TP in a 4.1 s spill / 6.4 s cycle
Running Time
5% of SEB beam =>
492 hrs
(crystal extr. eff.)
Triggers
Instantaneous rates (100% extr. eff.)
Entering Ring
8 x 106 part/s
Detector
p-p
Offline
p-m
1 x 106 part/s
1.8 x 105 s-1
910 s-1
400 Hz/strip
55 ms/SSD
11 ms/SSD
Prescale in trigger
100 MB/s
0.5 MB/s
(p-m)+vetoes
42 s-1
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Proposed Parasitic Running with AGS Crystal Extraction