1. Neutrino DIS measurements in CHORUS DIS2004 Strbske Pleso 14-4-2004 Alfredo G. Cocco INFN – Napoli

2. CHORUS detector   p/p = 0.035 p (GeV/c)  0.22   p/p = 10 – 15% (p < 70 GeV/c) -nuclear emulsion target (770kg) -scintillating fiber tracker  E/E = 32 %/  E (hadrons) = 14 %/  E (electrons)  h = 60 mrad @ 10 GeV ~ 27 GeV Air-core magnetActive target muon  spectrometer Calorimeter WB Neutrino beam :: :   :  : e : e ::: 1.00 : 0.06 : 0.017 : 0.007

3. Neutrino targets ET Emulsion ( 1  m precision  decay topology ) ET 770 kg, 4 X 0 2x10 6 CC ν interactions, 1994-1997 CT Calorimeter CT 112 ton, lead-scint.fiber, 5.2 1.5x10 7 CC ν interactions, 1994-1998 4T Special 4 targets 4T 100x4 kg, marble, plastic, Fe, Pb ~10 6 CC ν interactions, 1998

4. Charm D 0, Λ c, QE charm production cc CC/NC production BR  , fragmentation functions anti-neutrino charm production total charm production cross section Structure functions J/Ψ NC production Dimuons Trimuons Z/A dependence of CC cross-section Non-oscillation physics in CHORUS (ET) (CT) (4T)

5. Dimuons analysis To extract:  m c    (fragmentation)  B  (charm into  decay fraction) Dimuons

6. Data selection

7. Data sample  Data taken from 1995 to 1998 with a dedicated trigger setup  6.6  10 6 triggers  At least 2 reconstructed muons  5  10 5 events Dimuons

8. Selection criteria  5  E sh  200 GeV  ngap1  5 ngap2  5  E  1  5 GeV E  2  5 GeV  d 12  15 cm  q 2  4 GeV 2   V y,z   120 cm 295 cm  V x  394 cm  20  E  200 GeV x bj  1.0 y bj  1.0 Dimuons

9. Final sample 2  selected : N  = 2801 N  + = 13132 N +  = 1224 N ++ = 70 The leading muon is that one with the highest P T (96 % efficiency)             Leading muon 2nd muon Dimuons

10. MCDIS generator Dimuons

11. MCDIS  A new complete event generator for neutrino CC DIS has been implemented  Based on Aivazis helicity formalism  Leading Order cross section  Strange quark parametrization ( ,  )  Implements JETSET for hadronization  Fermi motion, radiative correction (Bardin)  Full control on each step via runcards Dimuons

12. MCDIS Leading Order cross section F = helicity structure functions (m t m c V CKM pdf(  ))  = Lorentz boost between lepton and hardon configurations Aivazis et al. (1994) Dimuons

13. MCDIS Leading Order cross section Where  in the limit of M 2 /Q 2  0 is the “slow rescaling” variable For charm neutrino production and neglecting initial quark mass Dimuons

14. MCDIS Fragmentation function z Z=P(h c )/P max (h c )  = 0.05 Peterson parametrization Dimuons

15. MCDIS Transverse momentum PT2PT2  = 1.1 W+W+ PTPT hchc N Dimuons

16. MCDIS Parton Distribution Functions  = 1 for a flavour SU(3) symmetric sea  Used: GRV94LO and CTEQ3L  Strangeness parametrization: Dimuons

17. Data – MC comparison E (GeV) E sh (GeV) E  1 (GeV) E  2 (GeV) P  2 (GeV/c) P  1 (GeV/c) data MC Dimuons

18. Data – MC comparison x y Q 2 (GeV 2 ) z V z (cm) V y (cm) data MC Dimuons

19. Data – MC comparison V x (cm) d 12 (cm) cos  2  12 Invariant mass (GeV) data MC cos  1 Dimuons

20. Evaluation of N charm

21. Background Background is due to  and K decay into  in CC interactions This can be evaluated using same sign dimuons in data and the ratio between opposite and same sign events in CC MonteCarlo Selection efficiencies and neutrino-antineutrino cross contamination also to be taken into account Dimuons

22. Background MonteCarlo:  High statistics (10 6 ) fully simulated CC interaction sample to evaluate Dimuons

23. Background In order to subtract background using this procedure it is crucial to verify that MC reproduces the distributions of the same sign dimuon events in the data Dimuons

24. Same sign Data-MC comparison E (GeV) E sh (GeV) E  1 (GeV) E  2 (GeV) P  2 (GeV/c) P  1 (GeV/c) data MC Dimuons

25. induced opposite sign dimuon events neutrino antineutrino CDHS 9922 2123 CHORUS 10718  288 420  63 NOMAD 2714  227 115  40 CHARM II 3100 700 CCFR 5030 1060 NUTEV 5102 1458 Dimuons

26. 4 parameters Maximum Likelihood fit  Event by event (unbinned) likelihood function in order to extract m c   B   Probability density given by MonteCarlo as a function of the unknown parameters Dimuons

27. ML fit result  Correlation coefficients  Systematic uncertainties Dimuons

28. Dimuon analysis result (preliminary)  m c = 1.46  0.15 (stat)  0.10 (syst)   = 0.56  0.05 (stat)  0.045 (syst)   = 0.040  0.003 (stat)  0.015 (syst)  B  = 0.098  0.005(stat)  0.014 (syst) Dimuons

29. Dimuon Analysis Summary  Largest sample of neutrino induced dimuons to date  Results from LO analysis in agreement with other experiments  Slow Rescaling model confirmed Dimuons

30. CDHS and HPWF (1978): ~100        events - origin largely unknown CHORUS: ~6x10 6 2  calorimeter triggers  observed: 42      , 3       (P  > 5 GeV/c) Detailed Monte-Carlo (LEPTO/JETSET/GEANT) 4x10 6 events with full detector simulation present knowledge of production rates and  -decays of  ’   data-MC validation using 2  events (known origin) data-MC comparison for 3  event sample Trimuon events in  CC interactions

31. Angle between leading    and sum of two others DATA All MC Charm ->  +     Int. bremsstrahlung Trimuons  < 90 o no int. bremsstrahlung

32. Trimuons MC 2  validation P  and   well reproduced Charm ->  +      decay  8.3  2.8 Internal bremsstrahlung (theoretical) 8.6  4.5 40 main 3  sources MC       predictions Observed in experiment: 42       Conclusions – MC predictions on 3  rate are in agreement with measurements

33. Z/A dependence of  CC cross-section for the first time 4 targets in the same experiment were exposed simultaneously positions rotated to avoid acceptance differences   CC interactions in calorimeter used to monitor neutrino flux and for relative normalisation of events empty target period recorded for background subtraction only muons used in event reconstruction events are assigned to particular target by extrapolating muon trajectory to the target plane Eur. Phys. J. C30 (2003) 159-167

34. Z/A Pb Fe M P Relative total cross sections Predictions are based on GRV98LO PDF and modifications according to A.Bodek-U.K.Yang model Predictions equalized to measurements at marble point  ( n)/  ( p) = 1.71

35. Z/A Comparison with previous experiments Conclusions: the result is in agreement with previous experiments and with predictions obtained by parton model calculations

36. Many analyses are still in progress NEW RESULTS WILL BE AVAILABLE WITHIN 2004