accelerator searches for oscillations ioannina, 20-23 april 2000 roumen tzenov cern and...
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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
Legend
• Introduction to neutrino oscillations• Short baseline accelerator
searches for – CHORUS– NOMAD
• Future long baseline accelerator searches
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
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
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
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)
• 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”
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)
WANFWANF West Area West Area Neutrino Facility Neutrino FacilityWANFWANF West Area West Area Neutrino Facility Neutrino Facility
The “horn”
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
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
Scintillating fibreScintillating fibretrackerstrackersScintillating fibreScintillating fibretrackerstrackersNucl. Instr. Meth A 412 (1998) 19
~ 2 mrad, xy~150 m
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%
Neutrino data-taking collection efficiency 1994-1997
N.B. Longest/Largest emulsion exposure ever done
Predictions and Scanback
tan
1947, first nuclear emulsions. Lattes et al., Brown et al.:
Discovery of Discovery of ee
Nuclear emulsion yesterdayNuclear emulsion yesterday
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
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
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
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
Decay searchDecay searchDecay searchDecay search
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
Off-line video-image analysisOff-line video-image analysisCHORUS Emulsion Display
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
* 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
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
• 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
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
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)
What to dofurther with accelerator beams?
Long baseline experiments
Long base line beams compared to WANF
MINOS detector
ICANOE detector
OPERA detector
200 ton iron/emulsion sandwiches + muon identificator
OPERA module
Long baseline experiments’ claims ...
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...
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