a review on the long baseline neutrino experiments pasquale migliozzi infn, sezione napoli, italy
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A review on the long baseline A review on the long baseline neutrino experiments neutrino experiments
Pasquale MigliozziPasquale MigliozziINFN, Sezione Napoli, Italy
The PMNS matrixThe PMNS matrix
3
2
1
321
321
321
UUU
UUU
UUU eeeeanalysesreactor Solar,
100
0cossin
0sincossexperimentnew by probed Terms
cos0sin
010
sin0cosanalyses K2K c,Atmospheri
cossin0
sincos0
001
1212
1212
1313
1313
2323
2323
CPCP ii ee
• e is suppressed due to small m122
• m232 and 23 dominate
• CP is the CP violation phase
23
223
213
4
232
132
232
232
132
232
sinsincos
sinsincos
sinsinsin
P
P
P
e
e
E
kmLm
)(27.1 2
2323
Leading oscillations in vacuum
Neutrino Oscillation MassesNeutrino Oscillation Masses
Three different types of experiments three different mass ranges!
Mass range accessible tolong baseline experiments
Super-Kamiokande Super-Kamiokande atmospheric atmospheric results results
1289 days
The atmospheric neutrino The atmospheric neutrino deficitdeficit
There is an apparent deficit of atmospheric 's seen in both Cerenkov detectors and calorimeters
While the atmospheric flux has large uncertainties, the L/E dependence implies oscillations
If it is oscillations, m2~3x10-3 eV2 @sin22=1 It is likely to be - (-s oscillations are
excluded at 99% CL)
Why long baseline Why long baseline experiments?experiments?
Check atmospheric neutrino results with a controllable beam
See appearance
Measure the product |m223|x23 with ~10%
precisionMeasure e and 13
Constrain or measure s
K2K
250 km
Close Detectors (CD)Far Detector
Sensitivity of the experimentSensitivity of the experiment
Sensitive to m2 above 2x10-3 eV2!
The neutrino beamThe neutrino beam
Pion monitor
Target/Horn systemAl alloy250 kA current
Proton intensity~5.5x1012/spill
Decay pipe200 m long and filledwith Helium @1atm
Average energy<E> ~ 1.3 GeV
K2K close detectorK2K close detector
Features Good vertex resolution Good angular resolution Good momentum resolutionfor high energy muons
Aim Measure energy Measure profile
Features Similar systematics as Super-Kamiokande
Aim Measure rate Measure 0 production
Fine grained calorimeter 1kton detector
(MRD)
to SK
MRD consists Drift tubes +12 layers of Fe(10cm x4 + 20cm x8) Fiducial mass 312 ton 200k evts/2.1x1019pot
Profile and spectrum stabilityProfile and spectrum stabilitymonitored with the MRDmonitored with the MRD
Stability of the profile Stability of the spectrum
To SK
1mrad
1mrad
beam direction is stable within 1 mrad
interaction @ different interaction @ different locationslocations
Event selection at SKEvent selection at SK
Using GPS timing
TOFTTT KEKSK
require
s1.3T2.0
28 evts fully contained in the fiducial volumehave been observed
10-3 background events up to nowmainly from atmospheric events
Trigger similar to the one used for atmospheric neutrino induced events
Expected #Expected # evts at SK (1) evts at SK (1)
CD
SKSK
CDFD
CD TL
TLRNN
..
..1observedexpected
#evts expected at SK assuming null oscillations
#evts observed in the near detector
Live time correctionusing proton on target
target
target
d
d
CD
SK
CDCD
SKSK
CDFD
N
N
E
ER
Event ratio R from MC calculation but
SK and CD confirmed bypion monitor (E > 1 GeV)
Expected #Expected # evts at SK (2) evts at SK (2)
The 1kton water Cerenkov detector is used as reference CD detector same neutrino interaction target
(cross section uncertainty cancels out) same detection energy threshold same event reconstruction scheme
small systematic error
The MRD and Scifi/Water detectors are used to check the consistency of the 1kton detector results
Expected #Expected # evts at SK (3) evts at SK (3)
Main source of sys. Error Sys. error from 1kton meas. (mainly due to fid. vol.) 5% Sys. error from SK meas. 3% Sys. Error from extrapolationFar/Close 7% Statistical error 1%
From June 1999 to June 2000 (2.3x1019 pot)
Results consistent with a deficit @90% C.L.K2K is running now, energy spectrum distortion is under study
The CNGS neutrino beamThe CNGS neutrino beam
ICARUS
The beam will
start
in may 2005
The CNGS beamThe CNGS beam
Shared SPS operation
200 days/year 4.5x1019 pot / year
Nominal beam
( m-2 / pot) 7.78x10-9
CC / pot / kton 5.85x10-17
< E > ( GeV ) 17
(e + e) / 0.87 %
/ 2.1 %
prompt negligible
ICARUS liquid argon imagingICARUS liquid argon imaging
The ICARUS technique is based on the fact that ionization electrons can driftover large distances (meters) in a volume of purified liquid Argon under a strongelectric field. If a proper readout system is realized (i.e. a set of fine pitch wiregrids) it is possible to realize a massive "electronic bubble chamber", withsuperb 3-D imaging.
C.R. shower from3 ton prototype
The ICARUS T600 moduleThe ICARUS T600 module
3
Atmospheric neutrinos Large event statistics with
Detection down to production thresholdsComplete event final state reconstructionIdentification all neutrino flavors Identification of neutral currents
Excellent resolution on L/E reconstructionDirect appearance search
Neutrinos from CERNSearch for µ Search for µ e
Solar neutrinosEnergy threshold: 5 MeV Large statistics, precision measurements“Smoking gun”: CC & NC
ICARUS 5kton physics reach (I)ICARUS 5kton physics reach (I)
m232, 23
m212
m232 23 13
m212, 12
extract
extract
extract
Proton decay
Large variety of decay modes accessible
study branching ratios free of systematics
Background free searches linear gain in sensitivity with
exposure
Neutrino “factory”
Precise measurement oscillation
Matter effects, sign of m223
First observation of e
CP violation
ICARUS 5kton physics reach ICARUS 5kton physics reach (II)(II)
m232 23 13
m232>0 or m2
32<0 ?
Unitarity of mixing matrix
0?
extract
oscillations (I)oscillations (I)
Analysis of the electron sampleExploit the small intrinsic e contamination of the beam (0.8% of CC)Exploit the unique e/π0 separation
Statistical excess visible before cuts this is the main reason for performing this experiment at long baseline !
At m2=3.5x10-3 eV2 110 e events are expected
Main background from charged current interactions of e in the beam 470 events are expected
oscillations (II)oscillations (II)
Reconstructed energy
e CC
signal
Reconstructed visible energy spectrum of electron events clearly evidences excess from oscillations into tau neutrino
oscillations (III)oscillations (III)
e CC
Transverse missing PT
Kinematical selection in order to enhance S/B ratio
Can be tuned “a posteriori” depending on the actual m2
For example, with cuts listed below, reduction of background by factor 100 for a signal efficiency 33%
m232=3.5x10–3 eV2; sin2223 = 1
Search for Search for 1313≠0 (I)≠0 (I)
P( e) sin2 213sin2232
32P( )cos4 13 sin2 223
232
4 years @ CNGS
P( e) sin2 213sin2232
32P( )cos4 13 sin2 2232
32
m232=3.5x10–3 eV2; sin2223 = 1 ; sin2213 = 0.05
Transverse missing PTTotal visible energy
Search for Search for 1313≠0 (II)≠0 (II)
Sensitivity to Sensitivity to 1313 in three family- in three family-mixingmixing
Estimated sensitivity to e oscillations in presence of (three family mixing)
Factor 5 improvement on sin2213 at m2 = 3x10–3 eV2
Almost two-orders of magnitude improvement over existing limit at high m2
4 years @ CNGS
The OPERA experimental The OPERA experimental technique technique
Emulsion Cloud Chamber (ECC) Emulsions for tracking, passive material as target Basic technique works
charmed “X-particle” first observed in cosmic rays (1971) DONUT/FNAL beam-dump experiment: events observed
m2 = (1.6 - 4) x10-3 eV2 ( SuperK) Mtarget~2 kton of ECC
large detector sensitivity, complexity modular structure (“bricks”): basic performance is preserved
Ongoing developments in the emulsion technique, required by the large vertex detector mass:
industrially produced emulsion films automatic scanning microscopes with ultra high-speed
Pb
Emulsion layers
1 mm
Experience with emulsions and/or searches : E531, CHORUS, NOMAD and DONUT
~ 10
m
The detector at The detector at Gran SassoGran Sasso(modular structure, configuration with three “supermodules”(modular structure, configuration with three “supermodules”))
spectrometerMagnetised Iron Dipoles
Drift tubes and RPCs
target and decay detector
Each “supermodule” is a sequence of 24 “modules”
consisting of - a “wall” of Pb/emulsion “bricks”- planes of orthogonal scintillator
strips
scintillator strips
brick wall
module
brick(56 Pb/Em. “cells”)
8 cm (10X0)
supermodule
Detector ready by may 2005
Sensitivity to Sensitivity to oscillations oscillations
Decay mode DIS long QE long DIS short Overall
e 3.0 2.6 1.3 3.7 2.7 2.8 - 2.7 h 2.2 2.8 - 2.3Total 8.0 8.3 1.3 8.7
5 years
3 years
e h Total
Charm production 0.15 0.03 0.15 0.33
e CC and 0 0.01 - - 0.01Large scattering - 0.10 - 0.10Hadronreinteractions
- - 0.10 0.10
Total 0.16 0.13 0.25 0.54
Total 0.19 0.13 0.25 0.57
Summary of Summary of detection efficiencies detection efficiencies(in % and including BR)(in % and including BR)
Expected background(5 years data taking)
m2 = 1.2x10-3 eV2 at full mixing
sin2 (2) = 6.0x10-3 at large m2
After 5 years data taking
Full mixing
5 years with shared SPS operation (2.25x1020 pot)
Average target mass = 1.8 kton (accounting for mass reduction with time, due to brick removal for analysis)
Uncertainties on background and efficiencies accounted for in the following
Expected Expected events events
decay 1.6 2.5 4.0 b.g.e 1.9 4.7 11.8 0.19 1.5 3.5 8.8 0.13h 1.3 3.0 7.6 0.25
Total 4.7 11.2 28.2 0.57
)eV 10(m 232
Statistical significanceStatistical significance
6 events
4 discoveryEvents observed
Sig
nif
ican
ce(e
qui
vale
nt )
NN44
Poisson distribution of the expected background
#evts observedNn
Probability that the b.g. fakes the
signal: < Pn if #observed evts
Nn
P4 = 6.3x10-5
P3 = 2.7x10-3
Probability of 4Probability of 4 significance significance
Schematic view of theSK allowed region
sin22
m2 (
eV2 )
68%
22%
9%
• Simulate a large number of experiments with oscillation parameters generated according to the SuperK probability distribution
• N4 events required for a discovery at
4
• Evaluate fraction P4 of experiments observing N4 events
years P3 P4
3 94% 80%
5 97% 92%
90 % CL limits * m2 ( 10-3 eV2 )
1.6 2.5 4.0
Upper limit 2.2 3.1 4.6
Lower limit 0.9 1.8 3.4
(U - L) / (2xTrue) 41 % 26 % 15 %
OPERA90 % CL in 5 years
* assuming the observation of a number of events corresponding to those expected for the given m2
Determination of Determination of mm22
(mixing constrained by SuperK)(mixing constrained by SuperK)
The MINOS ExperimentThe MINOS Experiment
Two Detector NeutrinoOscillation Experiment
(Start 2004)
Near detector: 980 tons
Far detector: 5400 tons
Iron/ScintillatorSampling calorimeter
1 cm x 4 cm plastic scintillator+
2.5 cm iron plates
The neutrino beam The neutrino beam
Target and horn 2 are moveable the beam energy can be changed
1st oscillation maximum
Need the low energy beamwith <E> = 7.6 GeV to see1st oscillation maximum which occurs at 2 GeV
SK best fit
Osc
illat
i on
Pro
babi
lity
Physics MeasurementsPhysics Measurements
Obtain firm evidence for oscillationsCharge current (CC) interaction rate and energy
distributionNC/(CC+NC) ratio (T-test)
Measurement of oscillation parameters, m2, sin22CC energy distribution
Determination of the oscillation mode(s) or s from NC and CC energy distributions
e limits or observation by identification of electrons
Limit from the T-testLimit from the T-test
likeNClikeCC
likeCC
NN
NT
NCC-like events with identified muonNNC-like events with no muon
10 kton-yr exposure2% overall flux uncertainty2% CC effciency uncertainty2% NC trigger efficiency uncertainty
Limit from the CC Energy Limit from the CC Energy SpectrumSpectrum
10 kton-yr exposure
2% overall flux uncertainty
2% bin-to-bin flux uncertainty
2% CC efficiency uncertainty
CC Energy Spectrum for various CC Energy Spectrum for various mm22
mm22, sin, sin2222 sensitivity sensitivity
10 kton-yr exposure
2% overall flux uncertainty
2% bin-to-bin flux uncertainty
2% CC efficiency uncertainty
For m2 = 0.0035 eV2 should be able to achieve better than 10% error at 68% C.L on both m2 and sin22
Limit on Limit on ee
MINOS 10 kt-yr 90% C.L. limit
Chooz 1999
m3 > m2
Matter effects includedm2
solar = 3 10-5 eV2
12 = 23 = 45 degrees = 010% systematic error on background
Ue32 < 0.013 @ m2>3 10-3 eV2
sin2213 < 0.05 @ m2>3 10-3 eV2
Already close to systematics limited with 10% error on background
JHF-Kamioka neutrino JHF-Kamioka neutrino experimentexperiment
Approved in December 2000Construction 2001-2006
50 GeV PS machineSuper-Kamiokande as a far detectorBaseline 295 kmLow energy neutrino beam tuned at the oscillation maximum
Physics measurementsPhysics measurements
Factor 10 improvement in disappearance
(sin2223)~0.01 (m223)~2x10-4 eV2
Search for e appearance with a sensitivity 20 times better than CHOOZ limit
sin22e 0.5 x sin2213 > 0.003
Search for a small admixture of sterile neutrinos
Layout of JHF and the Layout of JHF and the beam beam
Narrow Band Beam Off Axis beams
Thin solid line shows the WBB
• A large variety of beams is available to tune the energy at the oscillation maximum• Neutrino beam energy scan possible• Energy peak around 1 GeV• Electron neutrino contamination well below 1%
disappearance disappearance
energy reconstruction for QE (red)and non-QE interactions
m2 = 0.003 eV2
sin2223 = 1
non-QE events
All events
w/o oscillations
with oscillations
The error bar is from the statistics of 5 years
disappearance sensitivitydisappearance sensitivity
Ratio of measured spectrum with oscillations to the expectedone after subtraction of non-QEevents
Final sensitivity to oscillation parameters:•Off Axis 2 beam•NBB 1.5 GeV •NBB 3 GeV
ee appearance search appearance search
• Signal: e(Far)/(Near) expected to appear at the disappearance dip• Backgrounds
• misidentification: negligible• e contamination ~0.2-03%• 0 (neutral current) background ~0.3%
Sensitivity to sin22e > 0.003 A factor 20 better than the CHOOZ limit
~ 3x1020 e yr~ 3x1020 yr
The CERN present scenario
Neutrinos from a muon Neutrinos from a muon storage ringstorage ring
A very complex acceleration and storage A very complex acceleration and storage systemsystem
Optimal baseline is around 3000 kmfor CP violation + matter effects.
Search for long-baseline detector Search for long-baseline detector laboratorieslaboratories
Physics from Physics from e e ee with a long baseline program at a Neutrino with a long baseline program at a Neutrino
FactoryFactory
disappearance
(m2) ~ 5 x 10-5 (sin2223) ~ 5 x 10-3
– e appearance sensitivity down to sin22e ~ 10-3 - 10-4
Matter effects sign of m13
CP violationHigh energy e essential and unique
Neutrino interaction rates x 10 or more w/r to present beamsVery large detectors needed
ConclusionConclusion
The existing experiment is running smootly and could give soon conclusive results
(yes or no to oscillations) Experiments foreseen in the next years will probe mixing
angles deeply(23 and 13)
Future accelerators will be able to pin down with high precision the oscillation parameters and study CP violation
( in the PMNS matrix)
There is a lot of work to do!