WIN02, Christchurch (NZ), Jan’02
Charm in emulsionBart Van de Vyver (VUB,Brussels)
• CHORUS detector & CHORUS detector & emulsionemulsion
•Automatic event location, Automatic event location, ‘analysis-driven’ ‘analysis-driven’
vertex analysisvertex analysis
•Charm in opposite-sign Charm in opposite-sign dimuonsdimuons
•Dedicated searches Dedicated searches (manual)(manual)
•Net scan technique,Net scan technique,‘general’ vertex analysis‘general’ vertex analysis
•Semi-inclusive DSemi-inclusive D00 search search
•Associated charm Associated charm productionproduction
•OutlookOutlook
Heart of the detector:
Nuclear emulsion target
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) 7-44
CHORUS detector
0 m0 m
CHORUS emulsion
-21 m-21 m
-36 m-36 m
-54 m-54 m
~ 800 kg active target~ 800 kg active target
MIP : 30 MIP : 30 40 grains / 100 40 grains / 100 mm
transverse resolution ~ 0.5 transverse resolution ~ 0.5 mm
depth of focus : 1 to 3 depth of focus : 1 to 3 mm
350 m
90 m
Nucl. Instr. Meth. A 447 (2000) 361-376
Automatic Scanning
track
90 m plastic backing
350 m (175 m)emulsion sheet
CCDcamera
CCDcamera
microscope stroke
tomographic image
X50 magnification~3m focal depth
150x150 m view
Tracks reconstructed Tracks reconstructed by a hardware video by a hardware video processorprocessorframe to frame frame to frame emulsion grains emulsion grains coincidencecoincidence
350 m (175 m)emulsion sheete
muls
ion p
late
T.Nakano, Ph.D. Thesis, Nagoya Univ., 1997
Neutrino charm production
d,sd,scc
EEhadhad
--
hh
Beam knowledge
|Vcd|2,|Vcs|2
Quark density functions,strange sea ()
Charm fragmentationD0 : D+ : Ds
+ : c+
z = pc/pD
B(c)
+ NLO effects
g
s
cc
c
sg
s
+ radiative gluonand self energydiagrams
CDHS (CERN WBB)CDHS (CERN WBB)
Previous experiments
CCFR (NuTeV)CCFR (NuTeV)
CHARMII (CERN WANF)CHARMII (CERN WANF)
Zeitschr. Phys. C (1982) 19-31
Phys. Lett. B 206 (1988) 375-379
Zeitschr. Phys. C (1995) 189-198
E531 (Fermilab, E531 (Fermilab,
Nagoya)Nagoya)131 charm events in emulsion
only measurement of D0 : D+ : Ds+ :
c+
B(c) crucial for other
experiments
Eur. Phys. J., C11 (1999) 19-34
NOMAD (CERN WANF)NOMAD (CERN WANF) CERN EP 2000-072, submitted to Phys.Lett.B
9922 -+ , 2123 +- events
5044 -+ , 1062 +- events
4111 -+ , 871 +- events
2714 -+ , 115 +- events
CHORUS Phase I : dimuons
ZoomD+
h
‘Proof of principle’
0
5
10
15
20
25
94 95 96 97
Charged
Neutral
94/95 sample94/95 sample5 plates manual follow down
96/97 sample96/97 sample(N)TS automatic kink finding
xBjorken
A.U.sc
dc
fit
0.2 0.4 0.6
Event selectionEvent selectionE 2.3 GeV < 400 mradkink > 0.1 flightlength > 10 m
O. Melzer, Ph.D. Thesis, NIKHEF, 1997
N Ds* - N’
Ds+
+
+
Diffractively produced Ds
event
Phys. Lett. B 435 (1998) 458-464
All track segments (All track segments ( < 0.4 rad) in < 0.4 rad) in
Fiducial volume: 1.5 x 1.5 mmFiducial volume: 1.5 x 1.5 mm22 x 8 x 8
plates plates
Offline analysis of emulsion dataOffline analysis of emulsion data
Track segments from 8 plates overlapped
At least 2-segment
connected tracks
Eliminate passing-through
tracks
Reconstruct full vertex topology
CHORUS Phase II : net scan
8 plates
1.5 mm
1.5 mm
Charm selection
• matching to electronic matching to electronic detectorsdetectors
• track and vertex fitting track and vertex fitting (MCS)(MCS)
• displaced vertex with at displaced vertex with at least one or more matched least one or more matched trackstracks OROR• isolated, matched track isolated, matched track with large impact parameterwith large impact parameter
V2 226V2 226 V4 57V4 57
C1 121C1 121C3 124C3 124 C5 7C5 7
2ry int. 68 2ry int. 68 ee++ e e--, , ray 44 ray 44 low p 204low p 204
Manual checks
• Sample of 25,693 Sample of 25,693 CC interactions, ~15% of final statistics CC interactions, ~15% of final statistics
• selection efficiency : V2 selection efficiency : V2 58.6 58.60.7% , V4 0.7% , V4 70.1 70.11.7% 1.7%
• 851 (3.3%) selected events851 (3.3%) selected events
Neutral ~ 33 %Neutral ~ 33 %
Charged ~ 30 %Charged ~ 30 %
Backgr ~ 37 %Backgr ~ 37 %
(D(D00) / σ (CC) = 1.99 ) / σ (CC) = 1.99 0.13 (stat.) 0.13 (stat.) 0.17 (syst.) % 0.17 (syst.) %
<E<E>=27GeV, P>=27GeV, P < 30GeV/c < 30GeV/c
D0 production rate
(D0)/(CC)
E
(GeV)To appear in Phys.Lett.B (Measurement of D0 production in …, A.Kayis-Topaksu et al.)
(D(D00) / σ (charm) ) / σ (charm) = 53 = 53 11 % 11 %
Slow rescaling model Slow rescaling model mmcc = 1.3 GeV/c = 1.3 GeV/c22
CHORUSCHORUS
E531E531DD00 V4 / D V4 / D00 V2 V2 = 23.1 = 23.1 4.0 % 4.0 %
Associated charm production
30 29
21
1010 m 6735 m
transverse plane
-
D0
kink parent
Ns = 2Nh = 6
kink = 420 mrad
D0 f.l. = 340 m
f.l. = 1010 m2 = 310 mradf.l. = 7560 m
2ry vertex
pMeV/c
dE/dx proton
P = 0.78 GeV/c
P > 330 MeV/c
+180- 110
1st vertex
Data taking ongoing : 25k CC 200k CCImproved selection : purity 65% 90%
Outlook
• D0 production rate
• Inclusive charm, including charged
• Associated charm production
No need for manual?
c absolute BR,QE c production,D*+D0+
• Exclusive channels
~ 4,000 neutrino-induced charm events Fragmentation fractions D0 : D+ : Ds
+ : c+
B(c), Vcd, s(x), ...
Background evaluation based on CHORUS data and FLUKA Improved selection : efficiency 1% 25%
Proton identificationMCS momentum measurement detection
High purity selection
original loose tightselected 338 291 261charm 261 242 236secondary 29 28 13background 48 21 12 not checked 14 0 0 primary 13 5 3 e+e- 6 5 3 passing 8 6 2 fake vee 3 1 1 unrelated 2ry 4 4 3
VVudud0.1 %0.1 %
nuclear beta decay
The CKM matrix
VVcbcb5 %5 %
Be3 decay
VVcscs15 %15 %
De3 decay
VVubub 25 %25 %
b u l
VVusus1 %1 %
Ke3 decay
VVcdcd7 %7 %
charm production
VVtdtd VVtstsVVtbtb30 %30 %
t b l
Review of particle physics, 98 edition
d’d’
s’s’
b’b’
dd
ss
bb
==
Measuring Vcd
d(x) |Vcd|2 + s(x) |Vcs|2
d(x) + s(x)
CCcharm
CCall
had
hadcharm ~~
|Vcd|2
1 + s/d s|Vcs|2
++ d + s
s s 0 for large x 0 for large xBjorkenBjorken |Vcd|2
DifficultiesDifficultiesNo antineutrino data in emulsion
(5 % contamination in neutrino mode)No invariant mass reconstruction or particle ID
(inclusive analysis)Biases in the sample of vertices located in Nagoya
(CERN microscopes)Too low statistics for the time being
(Phase II rescan of all events)Hadronic decays more interesting than muonic ones, but harder
(Net scan both in Nagoya and at CERN)
A microscope view
120 m
150 m
3 m focal depth
Plates are orthogonal to Plates are orthogonal to the neutrino beamthe neutrino beam
An AgBr emulsion grain An AgBr emulsion grain has about 0.5 mm has about 0.5 mm diameterdiameter
Large angle nuclear Large angle nuclear fragments (if any) are fragments (if any) are seen as a ‘star’ of heavy seen as a ‘star’ of heavy ionizing ‘tracks’ in the ionizing ‘tracks’ in the vertex viewvertex view
Interaction tracks are Interaction tracks are seen as the coincidence seen as the coincidence of a single grain from of a single grain from each vieweach view
nuclear fragments
10 m