WIN02, Christchurch (NZ), Jan’02 Charm in emulsion Bart Van de Vyver (VUB,Brussels) CHORUS detector & emulsion CHORUS detector & emulsion Automatic event location, ‘analysis-driven’ vertex analysisAutomatic event location, ‘analysis-driven’ vertex analysis Charm in opposite-sign dimuonsCharm in opposite-sign dimuons Dedicated searches (manual)Dedicated searches (manual) Net scan technique, ‘general’ vertex analysisNet scan technique, ‘general’ vertex analysis Semi-inclusive D 0 searchSemi-inclusive D 0 search Associated charm productionAssociated charm production OutlookOutlook

Heart of the detector: Nuclear emulsion target 770 kg emulsion target and scintillating fibre tracker Calorimeter Air core spectrometer and emulsion tracker Air core spectrometer and emulsion tracker Veto plane Muon spectrometer Muon spectrometer  - -  - - h-h- h-h- T=5° Nucl. Instr. Meth. A 401 (1997) 7-44 CHORUS detector

0  m CHORUS emulsion -21  m -36  m -54  m ~ 800 kg active target MIP : 30  40 grains / 100  m transverse resolution ~ 0.5  m depth of focus : 1 to 3  m  350  m  90  m Nucl. Instr. Meth. A 447 (2000)

Automatic Scanning track 90  m plastic backing 350  m (175  m) emulsion sheet CCD camera CCD camera microscope stroke tomographic image X50 magnification ~3  m focal depth 150x150  m view Tracks reconstructed by a hardware video processor frame to frame emulsion grains coincidence 350  m (175  m) emulsion sheet emulsion plate T.Nakano, Ph.D. Thesis, Nagoya Univ., 1997

Neutrino charm productiond,s c E had ----  h  Beam knowledge |V cd | 2,|V cs | 2 Quark density functions, strange sea (  ) Charm fragmentation D 0 : D + : D s + :  c + z = p c /p D B(c  ) + NLO effects g  s c c c sg  s + radiative gluon and self energy diagrams

CDHS (CERN WBB) Previous experiments CCFR (NuTeV) CHARMII (CERN WANF) Zeitschr. Phys. C (1982) Phys. Lett. B 206 (1988) Zeitschr. Phys. C (1995) E531 (Fermilab, Nagoya) 131 charm events in emulsion only measurement of D 0 : D + : D s + :  c + B(c  ) crucial for other experiments Eur. Phys. J., C11 (1999) NOMAD (CERN WANF) CERN EP , submitted to Phys.Lett.B 9922  -  +, 2123  +  - events 5044  -  +, 1062  +  - events 4111  -  +, 871  +  - events 2714  -  +, 115  +  - events

CHORUS Phase I : dimuons Zoom D+D+   h

‘Proof of principle’ 94/95 sample 5 plates manual follow down 96/97 sample (N)TS automatic kink finding x Bjorken A.U. scsc dcdc fit Event selection E   2.3 GeV   < 400 mrad  kink > 0.1  flightlength > 10  m O. Melzer, Ph.D. Thesis, NIKHEF, 1997

 N  D s *  - N’ D s +   +   +   Diffractively produced D s event Phys. Lett. B 435 (1998)

All track segments (  < 0.4 rad) in Fiducial volume: 1.5 x 1.5 mm 2 x 8 plates Offline 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 Charm selection matching to electronic detectors matching to electronic detectors track and vertex fitting (MCS) track and vertex fitting (MCS) displaced vertex with at least one or more matched tracks OR displaced vertex with at least one or more matched tracks OR isolated, matched track with large impact parameter isolated, matched track with large impact parameter

V2 226 V4 57 C1 121 C3 124 C5 7 2ry int. 68 e + e -,  ray 44 low p 204 Manual checks Sample of 25,693  CC interactions, ~15% of final statistics Sample of 25,693  CC interactions, ~15% of final statistics selection efficiency : V2  58.6  0.7%, V4  70.1  1.7% selection efficiency : V2  58.6  0.7%, V4  70.1  1.7% 851 (3.3%) selected events 851 (3.3%) selected events Neutral ~ 33 % Charged ~ 30 % Backgr ~ 37 %

 (D 0 ) / σ (CC) = 1.99  0.13 (stat.)  0.17 (syst.) % =27GeV, P  =27GeV, P  < 30GeV/c D 0 production rate  (D 0 )/  (CC) E (GeV) To appear in Phys.Lett.B (Measurement of D 0 production in …, A.Kayis-Topaksu et al.)  (D 0 ) / σ (charm) = 53  11 % Slow rescaling model m c = 1.3 GeV/c 2 CHORUS E531 D 0  V4 / D 0  V2 = 23.1  4.0 %

Associated charm production  m 6735  m transverse plane -- D0D0 kink parent N s = 2 N h = 6  kink = 420 mrad D 0 f.l. = 340  m f.l. = 1010  m 22 = 310 mrad f.l. = 7560  m 2ry vertex p  MeV/c dE/dx proton P = 0.78 GeV/c P > 330 MeV/c st vertex

Data taking ongoing : 25k CC  200k CC Improved selection : purity 65%  90% Outlook D 0 production rate Inclusive charm, including charged Associated charm production No need for manual?  c absolute BR,QE  c production,D *+  D 0  + Exclusive channels ~ 4,000 neutrino-induced charm events Fragmentation fractions D 0 : D + : D s + :  c + B(c  ), V cd, s(x),... Background evaluation based on CHORUS data and FLUKA Improved selection : efficiency 1%  25% Proton identification MCS momentum measurement   detection

High purity selection

V ud 0.1 % nuclear beta decay The CKM matrix V cb 5 % B e3 decay V cs 15 % D e3 decay V ub 25 % 25 % b  u l V us 1 % K e3 decay V cd 7 % charm production V td V ts V tb 30 % t  b l Review of particle physics, 98 edition d’ s’ b’ d s b =

Measuring V cd d(x) |V cd | 2 + s(x) |V cs | 2 d(x) + s(x)   CC charm   CC all had   had charm  ~ |V cd | s/d  s|V cs | 2+ d + s s  0 for large x Bjorken |V cd | 2 Difficulties No 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 the neutrino beam An AgBr emulsion grain has about 0.5 mm diameter Large angle nuclear fragments (if any) are seen as a ‘star’ of heavy ionizing ‘tracks’ in the vertex view Interaction tracks are seen as the coincidence of a single grain from each view nuclear fragments 10  m