Recent Charm Production and Neutrino Oscillation Results From CHORUS

1
Recent Charm Production and Neutrino Oscillation
Results From CHORUS
Aysel Kayis Topaksu, University of Çukurova,
Adana
PANIC05, Santa Fe,NM 24 28 October 2005
2
Outline

• CERN Neutrino Beam Line
• CHORUS detector and Automatic emulsion data
  acquisition
• Results on charm analysis

• Measurement of total D0 production
• Anti-neutrino charm production
• Measurement of fragmentation properties of charm
• Bµ muonic branching ratio
• Measurement of D production
• Search for Superfragment and Hyperfragment

• Result on oscillation
• Conclusion

3
Neutrino beam
West Area Neutrino Facility at CERN SPS
450 GeV
CHORUS, NOMAD

• Wide Band Beam
• 5.06 ? 1019 POTs (1994-1997)
• ltEnmgt 27 GeV
• ltLgt 0.6 km
• Prompt nt negligible

ltLgt/ltEgt 2 ? 10-2 km/GeV
? Dm2 gt 1 eV2
4
CHORUS detector
Active target nuclear emulsion target (770kg)
scintillating fiber tracker
Air-core magnet ?p/p 0.035 p (GeV/c) ? 0.22
Muon spectrometer ?p/p 10 15
(p lt 70 GeV/c)
??
Calorimeter ?E/E 32 /? E (hadrons)
14 /? E (electrons) ?? h 60 mrad _at_ 10 GeV
27 GeV
CERN SPS
Veto
5
Automatic emulsion data acquisition
1
1
Location of n interaction vertex guided by
electronic detector.
2
2
Full data taking around n interaction vertex
called Netscan
Volume 1.5 x 1.5 mm2 x 6.3 mm
Angular acceptance 400 mrad
11 minutes / event
3
Offline tracking and vertex reconstruction
Reconstruct full vertex topology
At least 2-segment connected tracks
Track segments from 8 plates overlapped
Eliminate passing through tracks
6
Measurement of D0 production
Phys. Lett. B 527
(2002) 173, based on 25 of statistics
Phys. Lett. B 613
(2005) 105, based on full statistics NOW full
sample 95000 CC events
Candidate selection

• Primary track matched to detector muon
• Daughter track matched to detector track
• 3 13 µm lt I.P. wrt. 1ry vtx lt 400 µm

Confirmed D0sample

• 2 prong (V2) 819

• 4 prong (V4) 226

Selection efficiencies
(D0 V4 ) / ( D0 V2) 0.207 0.016
0.004

• V2 0.561 0.018

• V4 0.754 0.027

7
Fully neutral D0 decay mode
BR4/BR2 measured BR4 0.1338 0.0058
PDG BR(D0 neutrals) 1-BR4
x(1 BR2/BR4 ) 21.8 4.9 3.6 (6 prong
negligible)
Total production cross section
Relative detection efficiency D0/CC 0.88
s(D0)/s(CC) (2.69 0.18 x 0.13)
8
Charm production in antineutrino interactions
Phys. Lett. B 604 (2004) 11-21
N? 2704 N?- 95000 Selected events for visual
insp 81 found charm 40
1? spectrometer events
?kinkgt 50 mrad, F.L gt 50 ?m
4975 187 53
0.7)
9
Charm production rate as a function of neutrino
energy
10
Measurement of fragmentation properties of charm
Measurement of D0 momentum
Use correlation between opening angle of decay
daughters and charm momentum to obtain momentum
dist.
Inverse of geometrical mean of opening angle of
daughters
D Momentum
11
Z-distribution
zED/ ?
Fits to Collins-Spiller and Peterson
CHORUS Fit to Peterson formula (dotted curve is
MC model)

• Also an E531 measurement
• Indirect measurements from dimuon data
• CDHS, CCFR, CHARMII, NuTeV, CHORUS

12
Phys. Lett. B604 (2004) 145
Feynman x (xF) -distribution
Most charmed particles are produced in the
forward region
xFpL/pmax
13
Bµ muonic branching ratio
Phys. Lett. B626 2005,24-34
Direct observation of the charm parent and its
muon decay
Taking into account the new CHORUS measurement
of Br (D0 ? V0)
B? 7.3 ? 0.8 ? 0.2
B? (8.5 ? 0.9 ? 0.6)
Dimuon events have larger visible energy Evis gt
30 GeV
Bµ Vcd2LO(0.474 ? 0.027)x10-2 CDHS, CHARM II
CCFR averaged
VcdLO 0.239?0.046
0.221lt Vcdlt0.227 at 90 CL using CKM unitarity
and 3 generations
14
The results takes into account the new CHORUS
measurement of B(D0 ? V0)?22
15
Measurement of D production
Phys. Lett. B614 (2005) 155
Search for D in the decay channel D ? D0 ?
µ-
?
D0 flgt100mm
?
D signal in the D0 h sample
No signal in the D0h- sample
K-
µ- -
?
?
0.4 ltp(?)lt4 GeV/c 10lt pTlt50 MeV/c
D
D0
?
No signal in the Ch- sample
No signal in the Ch sample
Background prediction
(1)Shape of signal background normalized to
the observed events (2-3-4) shape normalized to
the total number of D0 and C respectively
16
Measurement of D production

Br(D ? D0 ?)0.6770.005 (PDG)
NOMAD 0.79 0.17 0.10 BEBC 1.22
0.25 Tevatron 5.6 1.8 (higher energy)
assuming that prompt D and D0 production rates
are equal we get
17
Search for Superfragments and Hyperfragments
18
Typical Candidate Event
A total of 28 non-mesic hyperfragments were found
19
Nuclear Physics B718, 2005, 35-54
Results
(2.00.4(stat) 0.3(syst))x10-3
Superfragment production limit /CC
lt 1.9 x 10-4 (90C.L.)
Using the Lambda_c production ratio
(s?(?c) /s(CC) (1.54 ? 0.35(stat) ?
0.18 (syst)) ? 10-2)
(90C.L.)
lt 1.3 x 10-2
20
Oscillation Analysis

• Decay mode considered
• i)-t - ?m- nm nt ii)- t - ?h-(np0)nt , iii)-
  t- ? 3h-(np0)nt
• Pre-selection (data from electronic detector)
• -vertex predicted in the emulsion
• -At least one negative track
• -1m sample
• -0m sample
• Emulsion Scanning
• -Scan back of selected tracks CS?SS?bulk?vertex
  plate
• -Vertex reconstruction decay Search, NETSCAN
• -Event selection
• -Eye-Scan Check, visible recoil, blob or Auger
  electron
• Final kinematical cuts
• -decay length, kink angle, Pt at vertex

21
Backgrounds
1m

• ?-??-???? (C1)
• Charm mesons in nm(nm) and ne CC interactions
• nm/e N ?D- m/e X
• m-/h- neutrals 10-6/ Nm
  0.11
• ?-?h-(nh0)?? (C1),
• ?-?hh-h-(nh0)?? (C3)
• Charm production similar to m channel
• White interactions

0m
22
White kink background
WK

• 1-prong nuclear interaction with no ionising
  activity at the interaction point (fake t decay
  topology)
• CHORUS measured
• lWK(PT gt 250 MeV/c) 24.0 8.5 m

t ? h
WK
PtGeV
Post-scanning WK rejection for C3
t ? h
Ft cut and ct cut
Fkink rad
23
Limit computation
24
Limit computation
? number of detectable ?? events if the
oscillation probability is 1
Ntmax
bg
data
0mC1
59
9,447
51.59.7
Phase II
0mC3
5112
48
4,974
5,014
1mC1
0
0.1000.025
Phase I
5,26
0mC1
0
0.3000.075
Feldman and Cousins unified approach G.J. Feldman
and R.D. Cousins Phys.Rev. D57 (1998) 3873
25
Status of oscillation into ??
This analysis excludes a region of the ?????
oscillation with sin22? gt 3.4x10-4 (at 90 CL)
at high ?m2.
P nm--gtnt lt 1.72x10-4 _at_ 90 CL S nm--gtnt
2.5x10-4 _at_ 90 CL P(L) 28

26
Conclusion

• CHORUS still working on charm analysis.
• Measurement of associated charm production in
  neutral- and
• charged-current neutrino int.
• Measurement of the x-distributions of charmed
  particle
• production in neutrino interactions
• Measurement of Lambda_c production and decay
  into Sigma
• in neutrino interactions
• Measurement of diffractive production of D_s in
  neutrino interactions
• .. Are still in progress