short baseline neutrino experiments
DESCRIPTION
Short Baseline neutrino experiments. Outline Status of oscillation experiments Charm production Summary. Jaap Panman, CERN. Neutrino 2004, Paris, 15 June 2004. Oscillation searches. In this talk concentrate on CERN programme, other experiments are covered by other speakers. - PowerPoint PPT PresentationTRANSCRIPT
Short Baseline neutrino experiments
Jaap Panman, CERN
Neutrino 2004, Paris, 15 June 2004
Outline
Status of oscillation experiments
Charm production
Summary
Oscillation searches In this talk concentrate on CERN programme, other
experiments are covered by other speakers.
MOTIVATION of the CERN - programme:
At proposal time:
•Cosmologically relevant region (few eV scale)
•Seesaw mechanism could accommodate eV scale masses and relatively small mixing
After SuperK:
•Smaller mass-differences more likely
•But, LSND …
Neutrino
beam
Wide Band Beam – 5.06 1019 POTs (1994-1997)
– <E> ~ 27 GeV
– <L> ~ 0.6 km
– Prompt : negligible
West Area Neutrino Facility at CERN SPS
CHORUS, NOMAD
450 GeV
<L>/<E> ~ 2 10-2 km/GeV m2 > 1
eV2
NOMAD
detection by kinematicalselection
CHORUS
Active target
•Nuclear emulsion
•Sci-Fi tracker
Calorimeter
Spectrometer
Air-core magnet
Veto
-,h-
, (o’s)
path
vertex
kink
-54 m-54 m
-36 m-36 m-21 m-21 m
0 m0 mRed frame: Red frame:
~30x40 ~30x40 mm22
beam
detection by decay KINK recognition
Status of oscillation into – e –
NOMAD data: final - CHORUS phase-II not yet finished
Search for –e oscillation in NOMAD
• Motivated by LSND result• Final results available• Due to electron neutrino component in beam (1%) – careful simulation of
beam line needed• Exploit powerful electron identification• Study energy spectra (enhanced at low energy) and radial distributions
(enhanced in the center)
Final results
Define ratio of electron and muon neutrino CC events
Events are compatible with known sourcesNo evidence for oscillations
NOMAD result rules out the LSND allowed region with m2 above 10 eV2
Charm production
Additional results of NOMAD and CHORUS:• Charm physics• (for other results see Camilleri’s talk)
NOMAD charm physics• D* production and fragmentation study• Exploiting mass resolution
CHORUS charm physics• Neutral and charmed particle production• Decay properties, fragmentation studies• Exploiting topological decay recognition• Charm studies only possible with PHASE-II NetScan technology
Automatic emulsion data
acquisition (phase-II)1
2
3
Angular acceptance : 400
mrad
Track segments from 8 plates overlapped
At least 2-segment connected tracks
Eliminate passing through tracks
Reconstruct full vertex topology
Volume : 1.5 x 1.5 mm2 x 6.3 mm
1
2Location of interaction vertex
guided by electronic detector.
Full data taking around interaction vertex called Netscan
Offline tracking and vertex
reconstruction
~ 11 minutes / event
Measurement of D0 production Phys. Lett. B 527 (2002) 173, based on ~25% of statistics
NOW: full sample: 95450 CC events
Candidate selection
Detector muon
I.P.
Primary track matched to detector muon
Daughter track matched to detector track
3 ~ 13 μm < I.P. wrt. 1ry vtx < 400 μm
2 prong (V2) 841 (background: 35)
4 prong (V4) 227 (no background)
Confirmed D0sample
Selection efficiencies
V4 : 74.2 ± 0.9 x 10-2
V2 : 56.3 ± 0.5 x 10-2
BG subtracted, efficiency corrected
V2 1426 ± 52
V4 305 ± 21
(D0 V4 ) / ( D0 V2)
= 21.4 ± 1.6 x 10-2
Preliminary
σ(D0)/σ(CC) = 2280/95450/0.88 =
= 2.71 ± 0.22 x 10-2
Fully neutral D0 decay modes:
BR4/BR2 – measuredBR4/BR2 – measured
BR4 = 0.1338 BR4 = 0.1338 ± 0.0058 PDG
BR(D0 neutrals) = 1-BR4 x(1+ BR2/BR4 ) = BR2/BR4 ) = 24.1 24.1 ± 4.5% 4.5% (6 prong negligible) (6 prong negligible)
Total production cross
section:All All D0’s = NV4/BR4 = 2280 ± 151(stat.) ± 26(stat.eff.) ± 99(BR4 err.)
Relative detection efficiency D0/CC = 0.88
Preliminary
Study of fragmentation
Different strategies to study fragmentation Properties of charm production:
NOMAD isolates D* using invariant mass reconstruction
For these events, kinematic quantities are well measured, but statistics is low
CHORUS uses a high statistics and pure sample of D0 events obtained by isolating neutral particle decays.
However, distributions have to be obtained by an unfolding method.
Nomad D*+ measurement
Step 1: exploit invariant mass combinationsStep 2: kinematical cutsStep 3: neural network to reduce combinatorial background
Cleanest sample: Neural Net estimator cut at K=0.8735
35+-7.2 events (12 background)
Larger statistics: K>0.6
Use decay chain:
Study larger statistics sample:Background is combinatorial MC: S+B Data
D* mass in clean sample
D* yield in CC events (T):
Compatible with BEBC
pT2 distribution of charmed particles
The transverse momentum of charmed particles wrt thedirection of the hadronic system is usually parametrized as
2
2Tbp
T
edp
dN
Phys. Lett. B 206 (1988) 380-384• NOMAD 47-12 eventsPhys. Lett. B 526 (2002) 278-286
NOMAD
Measurement of D0 momentum
Use correlation between
opening angle
of decay daughters and
charm
momentum to obtain
momentum distribution
D Momentum
Inverse of
geometrical
mean of
opening angle
of daughters
Momentum distribution of D0
can be measured by
unfolding opening angle
distribution
(curve is the model in the
CHORUS MC)
Prelim
inary
NOMAD
Z-distribution
NOMADFits to Collins-Spiller and Peterson:
Also an E531 measurement Indirect measurements from dimuon
data: CDHS, CCFR, CHARMII, NuTeV,
CHORUS
CHORUSCHORUS
Prelim
inary
CHORUS:
Fit to Peterson formula
(dotted curve is MC model)
Feynman x distribution
Prelim
inary
NOMAD
Most charmed particles are produced in the forward region
CHORUS
Charm fragmentation
results
Large spread in valuesMaybe due to different mixtures of charm final states:• E531: all charm decays• Nomad: D*• CHORUS: D0
• Dimuon experiments: weighted by muonic decay mode
Measurement of Λc production
A statistical approach using flight length
distribution
Short flight decay :
Λc enriched
sample
Long flight decay :
D+, Ds dominant
Two different set of
criteria
have been adopted.
Strategy
Flight length in
μm
MC
Λc
D+
Ds
Phys.Lett.B 555 (2003) 156 based on 50414 Phys.Lett.B 555 (2003) 156 based on 50414 CCCC
Measurement of Λc production
Short flight decay (A)Daughter track : Distance to the muon 5 µm to 30
µm
Long flight
decay (B)
Candidate selection
Parent track : distance to the muon < 5 µm
Distance between daughter and parent 5µm to 30
µm
1614 events from 50,414 CC events were
selected for visual inspection
Detector muon
Detector muon
586 events from 56,761 CC events were
selected for visual inspection
(A)
(B)
Samples after flight length
cut1
prong
3 prong
(A) 40 mm < FL < 400 mm
(B) 400 mm < FL < 2400 mm
62 66133 195
• Combining short (A) and long (B) decay search,and taking Combining short (A) and long (B) decay search,and taking
into account efficiency and background:into account efficiency and background:
• c c = 861 = 861 198 (stat.) 198 (stat.) 98 (syst.) 98 (syst.)+140 +140 (QE)(QE)
• Br(Br(cc 3prong) = (24 3prong) = (24 7 (stat.) 7 (stat.) 4 (syst.)) 4 (syst.)) 10 10-2-2
σσ((c) /σ(CC)= (1.54 c) /σ(CC)= (1.54 0.35(stat) 0.35(stat) 0.18 (syst)) 0.18 (syst)) 10 10-2-2
-54-54
σσ((c)/σ(CC)c)/σ(CC)Br(Br(cc 3prong)=(0.37 3prong)=(0.37 0.10(stat) 0.10(stat)
0.02(syst))X100.02(syst))X10-2-2
Λc
a) n - c+ b) n - c
+ (c*+) c) p - c
++(c*++)
Quasi-elastic charm production
•Require 2 or 3 tracks at primary vertex• 165° (angle between muon and charm in the transverse plane)•Flight length < 200 m (enriched c sample)
•Calorimeter energy < 10 GeV and electromagnetic energy < 2 GeV
Topological and kinematical selection criteria:
13 events with a background of 1.70.60.6 (mainly from DIS c)
QE production is about
15% of c production
Phys.Lett.B 575 (2003) 198 based on 46105 Phys.Lett.B 575 (2003) 198 based on 46105 CCCC
Energy measured in calorimeter
Azimuthal angle
Kinematical selection of QE candidates
Events in first bin
Associated charm production
Charged-current
Gluon bremsstrahlung
c
–c
W
g
D+D+X–
One event has been observed and published.
Phys. Lett B 539 (2002) 188, CHORUS Coll.Phys. Lett B 539 (2002) 188, CHORUS Coll.
In CC interactions
c
–cg
Z
Z-gluon fusion
D+D+X–
Associated charm productionNEW
In NC interactions
ANDGluon bremsstrahlung
c
–c
Z
g
D+D+X–
In the past only one event• Observed in E531 emulsionIndirect search performed by NuTeV• Production rate (2.6x1.6)x10-3 of CCSystematic search for double decay topologies Events observed in NC and CC interactions with very low background (order 0.1 event)
TTT #6 PT #6 PPP>0.66 GeV/C @ 90 CL.>0.66 GeV/C @ 90 CL.
TTT #3 T #3 PPd4d4>2.72 GeV/c @ 90 CL.>2.72 GeV/c @ 90 CL.
TTT #8, T #8, PPd2d2>4.66 GeV/C @ 90 CL.>4.66 GeV/C @ 90 CL.
TTT #5, T #5, PPd1d1> 1.39 GeV/C @ 90CL.> 1.39 GeV/C @ 90CL.
ppl23l23 ppl22l22
example of NC eventexample of NC event
E=29.9GeVE=29.9GeV
PPd3d3>3.33 GeV/c @ 90 CL.>3.33 GeV/c @ 90 CL.
Both neutral decays Both neutral decays inconsistent with two-inconsistent with two-body decay body decay (acoplanarity)(acoplanarity)
E=36.9 GeVE=36.9 GeV P=-16.9 P=-16.9 GeV/cGeV/c
Pl31Pl31 pl30 pl30
example of CC example of CC eventevent
PPd1d1>4.70 GeV/c @ 90 CL.(>4.70 GeV/c @ 90 CL.(TTT #2)T #2)
PPd2d2>0.67 GeV/c @ 90 CL.>0.67 GeV/c @ 90 CL.
PPd3d3>2.32 GeV/c @90 CL.(>2.32 GeV/c @90 CL.(TTT T #7)#7)
PPd2d2>1.92 GeV/c @90 CL.(>1.92 GeV/c @90 CL.(TTT #5)T #5)
Evis= 53.8 GeVEvis= 53.8 GeV
Both neutral decays Both neutral decays inconsistent with two-inconsistent with two-body decay body decay (acoplanarity)(acoplanarity)
CCharm production in antineutrino
interactionsN+ = 2725
N- = 93890
Selected events = 82
found charm = 61
after reconstruction cut = 32
“1 spectrometer events”
kink> 50 mrad, F.L > 50 m
fC-
fCo= 2.9
+ 1.9
- 1.2 (stat)
(N +cX)(N +X) = 4.8 %+ 1.2
- 0.9
N= 4374 ± 135
Prelimina
ry
Energy dependence
CDHS and HPWF (1978): ~100 events - origin largely unknown
CHORUSCHORUS:: ~6x10~6x106 6 22 calorimeter triggers calorimeter triggers
observed: observed: 42 , 3 (P(P > 5 GeV/c) > 5 GeV/c) Detailed Monte-Carlo (LEPTO/JETSET/GEANT) Detailed Monte-Carlo (LEPTO/JETSET/GEANT)
4x104x106 6 events with full detector simulationevents with full detector simulation present knowledge of production rates andpresent knowledge of production rates and
-decays of -decays of ’
data-MC validation using 2data-MC validation using 2 events (known origin) events (known origin)
data-MC comparison for data-MC comparison for 3event sampleevent sample
Trimuon events in CC interactions
Angle between leading Angle between leading and sum of two othersand sum of two others
DATADATA
All MCAll MC
Charm->Charm-> + +
Int. bremsstrahlungInt. bremsstrahlung
TrimuonsTrimuons
nono int. bremsstrahlungint. bremsstrahlung
TrimuonsTrimuons
MC 2MC 2 validation validationPP and and well reproducedwell reproduced
Charm->Charm-> + + decaydecay 8.38.32.82.8Internal bremsstrahlungInternal bremsstrahlung (theoretical) (theoretical) 8.68.64.54.5 4040
main 3main 3 sources sources MC MC predictions predictions
Observed in experiment: 42 Observed in experiment: 42
Conclusions – MC predictions Conclusions – MC predictions on on 33 rate are in agreement rate are in agreement with measurementswith measurements
SUMMARY
• SBL oscillation programme at CERN:– NOMAD final data
– CHORUS, final statistics, but phase-II analysis ongoing
• Many additional measurements (in this talk concentrated on charm physics)– Production cross-sections
– Fragmentation functions
– Decay properties
• Other results will be shown by Camilleri