Accelerator searches for oscillations Ioannina, 20-23 April 2000 Roumen Tzenov CERN and...
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![Page 1: Accelerator searches for oscillations Ioannina, 20-23 April 2000 Roumen Tzenov CERN and University of Sofia.](https://reader036.fdocuments.net/reader036/viewer/2022070416/56649d555503460f94a32dc5/html5/thumbnails/1.jpg)
Accelerator searches Accelerator searches
for for oscillations oscillations
Accelerator searches Accelerator searches
for for oscillations oscillations
Ioannina, 20-23 April Ioannina, 20-23 April 20002000
Roumen TzenovCERN and University of Sofia
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Legend
• Introduction to neutrino oscillations• Short baseline accelerator
searches for – CHORUS– NOMAD
• Future long baseline accelerator searches
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Associate neutrino flavour with the charged lepton flavour as seen in charged-current interactions:
For massive neutrinos: flavour eigenstate need not be a mass eigenstate but can be a coherent superposition:Mixing matrix U is unitary
The propagation of different mass eigenstates leads to flavour oscillation in vacuum:
Simplification for 2 mixing flavours with mixing angle (phase ):
Interactions are now nondiagonal with the mass eigenstates!
A U e Um
iM L
Em
m
m
2
2 *
A B
l m mm
U
Ue
e
i
i
cos sin
sin cos
Neutrino mixing
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The probability that a neutrino oscillates (changes flavour):
With definition:
To have a large effect:
Maximum at 1/4 oscillation length
P M eVL km
E GeV
sin sin .2 2 2 22 127
M M M222
12
M eVL km
E GeV2 2
1
L
EM
1
22127
.
Neutrino oscillations
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Two parametric oscillation plot
10 -1210 -1110 -1010 -910 -810 -710 -610 -510 -410 -310 -210 -1110100
m2
(
eV
2)
LSND
Cosmologically relevantSolar + seesaw + DM ?
Atmospheric
Solar (MSW)
Solar (vacuum oscillation)
KamiokandeSuperKamiokande
10 -5 10 -4 10 -3 10 -2 10 -1 1.sin2 2
e
e
e
CHORUS and NOMAD
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The The CollaborationCollaboration
Belgium (Brussels, Louvain-la-Neuve), CERN, Germany (Berlin, Münster), Israel (Haifa), Italy (Bari, Cagliari, Ferrara, Naples, Rome, Salerno),Japan (Toho, Kinki, Aichi, Kobe, Nagoya,Osaka, Utsunomiya) ,Korea (Gyeongsang),The Netherlands (Amsterdam), Russia (Moscow), Turkey (Adana, Ankara,Istanbul)
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• appearance in the SPS WBB beam via oscillation
• P() down to 1•10-4 for m2 ~10 eV2
• direct detection in 770 kg nuclear emulsion target
Tag: visible 1- and 3- prongs
decay of primary -lepton
(decay path ~1.5 mm)
CHORUS Main objectiveCHORUS Main objective
-
h-ne- e+--n
R
“Kink”
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CHORUS NOMAD
124 m 290 m 408 m
450 GeVSPS
protonsBeryllium
target horn reflector vacuum tunnelearth/ironshielding
CERN West Area Neutrino CERN West Area Neutrino FacilityFacility
<L> ~0.6 km; L(rms)/L~0.2
• WBB, <E > = 26.6 GeV
•~5•10 protons on target•~840K CC in CHORUS
• CC / CC ~ 3. 10
19
-6
(~0.1 background event)(~0.1 background event)(~0.1 background event)(~0.1 background event)
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WANFWANF West Area West Area Neutrino Facility Neutrino FacilityWANFWANF West Area West Area Neutrino Facility Neutrino Facility
The “horn”
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SPS and WANF SPS and WANF (() neutrino beam) neutrino beamSPS and WANF SPS and WANF (() neutrino beam) neutrino beamProtons on neutrino from 1994 to 1998
0.0E+00
2.0E+18
4.0E+18
6.0E+18
8.0E+18
1.0E+19
1.2E+19
1.4E+19
1.6E+19
1.8E+19
2.0E+19
1 21 41 61 81 101 121 141 161 181 201 221
19941995199619971998
protons
number of days of operation
1994
1998
1997
1995
1996
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CHORUSCHORUS detectordetectorCHORUSCHORUS detectordetector
770 kg emulsion target
and scintillating fibre tracker
Calorimeter
Air core spectrometer andemulsion tracker
Air core spectrometer andemulsion tracker Veto plane
Muon spectrometerMuon spectrometer
- -
h-h-
T=5°T=5°Nucl. Instr. Meth A 401 (1997) 7
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Scintillating fibreScintillating fibretrackerstrackersScintillating fibreScintillating fibretrackerstrackersNucl. Instr. Meth A 412 (1998) 19
~ 2 mrad, xy~150 m
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External electronicExternal electronicdetectors:detectors:External electronicExternal electronicdetectors:detectors:
P(h±)<20 GeV/cp/p ~25%
P(h±)<20 GeV/cp/p ~25%
E/E ~35%/E(GeV) E/E ~35%/E(GeV)
• sign and momentum of pions
• Hadronic and e-m shower energy and direction
• Muon momentum and idEvent pre-selection and
post-scanning analysis 3<P(±),GeV/c<100
p/p = 11-20% 3<P(±),GeV/c<100
p/p = 11-20%
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Neutrino data-taking collection efficiency 1994-1997
N.B. Longest/Largest emulsion exposure ever done
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Predictions and Scanback
tan
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1947, first nuclear emulsions. Lattes et al., Brown et al.:
Discovery of Discovery of ee
Nuclear emulsion yesterdayNuclear emulsion yesterday
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Target = 4 stacks (1.4Target = 4 stacks (1.41.4 m1.4 m22))
1 stack = 36 1 stack = 36 platesplates
MIP : 30 MIP : 30 40 grains / 100 40 grains / 100 mm
– Grain size ~ 0.3 mm
– Angular resolution 1.5 mrad 80 80 mm
100
1
00
mm emulsion 350 mkm
base 90 mkm
1/4 plate1/4 plate
CHORUS emulsion plateCHORUS emulsion plate
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CCD and XYZ stage
CCD and XYZ stage
New Track SelectorNew Track Selector
Host CPUHost CPU
Network Network data data
storagestorage
CHORUS automatic microscopesCHORUS automatic microscopes
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Megapixel CCD and XYZ stageMegapixel CCD and XYZ stage
High Performance optics
High Performance optics
DSPsDSPs
Processing ClusterProcessing Cluster
CHORUS automatic microscopesCHORUS automatic microscopes
1 m
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Inside a “vertex plate”Inside a “vertex plate”
-54 m-54 m
-36 m-36 m
-21 m-21 m
0 m0 m
View size: 120x150 View size: 120x150 mm22
Focal depth : ~3 Focal depth : ~3 mm
Red frame: ~30x40 Red frame: ~30x40 mm22
beam
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Decay searchDecay searchDecay searchDecay search
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Offline selectionOffline selection small impact parameter between parent and daughter kink point is in the vertex plate
- kink detection (parent search)
or h
PrinciplePrinciple:Parent track () can be detected bywider view and general angle scanningat the vertex plate
Impact parameter
scan-back track
general scanning area
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Off-line video-image analysisOff-line video-image analysisCHORUS Emulsion Display
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sD
*s NDN
Phys. Lett. B 435(1998) 458-464.
Manual scanning on special Manual scanning on special events:events:Diffractive D*s production, double leptonic decay
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* 0 decay search not finished yet (1996-1997), not
included in current results
Status of Phase I scanningStatus of Phase I scanningStatus of Phase I scanningStatus of Phase I scanning
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kink
11CC
CC
)(BrNA
AS
Det efficiency:
Ratio of Acceptances
Located Vertexes
S=N if P=1A=detector acceptanceN=normalization=Kink finding efficiency
In the same way, it is applied to the 0 sample
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• 1 sample (--)– charm production from antineutrino CC (with primary
lepton (e+ or +) unidentified
contamination of the beam
• 0 sample (-h-)
– charm production from antineutrino CC
– 1-prong nuclear interaction without visible recoil or
nuclear break-up (White kinks)
BackgroundBackgroundBackgroundBackground
~10-6 / N~10-6 / N
~10-7 / N~10-7 / N
~2•10-6 / N~2•10-6 / N
~2•10-5 / N~2•10-5 / N
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Includes also 17% systematic error (NIM A320 (1993) 331)
Includes also 17% systematic error (NIM A320 (1993) 331)
CHORUS current limit
sin2 2 < 8 •10-4• No candidates found
• n CC (expected) = P•S,
•S = 6003 ± 17% (syst)
•P < 2.38 / 6003 =
4•10-4 (@ 90% C.L.)
• No candidates found
• n CC (expected) = P•S,
•S = 6003 ± 17% (syst)
•P < 2.38 / 6003 =
4•10-4 (@ 90% C.L.)
sin2 2 sin2 2
m2/e
V2
m2/e
V2
Current ResultCurrent ResultCurrent ResultCurrent Result
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OutlookOutlook::OutlookOutlook::• Phase I scanning: Going to finish this year
Expected gain in sensitivity:
• ~1.2 from 1 (short decays, statistics)
• ~1.2 from 0 (3prongs, 0 96+97)
• Phase II scanning and analysis: years 2000-2001• New generation of automatic systems• Upgraded predictions• 3prongs dedicated search e ? (electron id by MS in emulsion)• Full vertex analysis
(NETSCAN, General tracking) charm physics:|Vcd|2,cc,D+/D0
PP < 1.0•10 < 1.0•10 -4 -4 (in absence of (in absence of -candidates)-candidates)
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What to dofurther with accelerator beams?
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Long baseline experiments
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Long base line beams compared to WANF
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MINOS detector
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ICANOE detector
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OPERA detector
200 ton iron/emulsion sandwiches + muon identificator
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OPERA module
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Long baseline experiments’ claims ...
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Conclusion
Current short baseline accelerator searches for oscillations have almost done their job;
No oscillations seen (so far) for large m2 and small mixing angles;
Atmospheric neutrino data suggest, on the opposite, small mass difference and large mixing angle;
Several long baseline accelerator experiments are on the start scratch to clarify the issue...