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