1. Short Baseline neutrino experiments Jaap Panman, CERN Neutrino 2004, Paris, 15 June 2004 Outline Status of oscillation experiments Charm production Summary

2. Oscillation searches In this talk concentrate on CERN programme, other experiments are covered by other speakers. MOTIVATION of the CERN  -  programme: At proposal time: Cosmologically relevant region (few eV scale) Seesaw mechanism could accommodate eV scale masses and relatively small mixing After SuperK: Smaller mass-differences more likely But, LSND …

3. Neutrino beam Wide Band Beam –5.06  10 19 POTs (1994-1997) – ~ 27 GeV – ~ 0.6 km –Prompt  : negligible West Area Neutrino Facility at CERN SPS CHORUS, NOMAD 450 GeV / ~ 2  10 -2 km/GeV   m 2 > 1 eV 2

4. NOMAD  detection by kinematical selection

5. CHORUS Active target Nuclear emulsion Sci-Fi tracker Calorimeter Spectrometer Air-core magnet Veto   -,h - , (  o ’s)   path vertex kink -54  m -36  m -21  m 0  m Red frame: ~30x40  m 2 beam  detection by decay KINK recognition

6. Status of oscillation into   –  e  –  NOMAD data: final - CHORUS phase-II not yet finished

7. Search for  – e oscillation in NOMAD Motivated by LSND result Final results available Due to electron neutrino component in beam (1%) – careful simulation of beam line needed Exploit powerful electron identification Study energy spectra (enhanced at low energy) and radial distributions (enhanced in the center)

8. Final results Define ratio of electron and muon neutrino CC events Events are compatible with known sources No evidence for oscillations NOMAD result rules out the LSND allowed region with  m 2 above 10 eV 2

9. Charm production Additional results of NOMAD and CHORUS: Charm physics (for other results see Camilleri’s talk) NOMAD charm physics D* production and fragmentation study Exploiting mass resolution CHORUS charm physics Neutral and charmed particle production Decay properties, fragmentation studies Exploiting topological decay recognition Charm studies only possible with PHASE-II NetScan technology

10. Automatic emulsion data acquisition (phase-II) 1 2 3 Angular acceptance : 400 mrad Track segments from 8 plates overlapped At least 2-segment connected tracks Eliminate passing through tracks Reconstruct full vertex topology Volume : 1.5 x 1.5 mm 2 x 6.3 mm 1 2 Location of interaction vertex guided by electronic detector. Full data taking around interaction vertex called Netscan Offline tracking and vertex reconstruction ~ 11 minutes / event

11. Measurement of D 0 production Phys. Lett. B 527 (2002) 173, based on ~25% of statistics NOW : full sample: 95450 CC events Candidate selection Detector muon I.P. Primary track matched to detector muon Daughter track matched to detector track 3 ~ 13 μm < I.P. wrt. 1ry vtx < 400 μm 2 prong (V2) 841 (background: 35) 4 prong (V4) 227 (no background) Confirmed D 0 sample Selection efficiencies V4 : 74.2 ± 0.9 x 10 -2 V2 : 56.3 ± 0.5 x 10 -2 BG subtracted, efficiency corrected V2 1426 ± 52 V4 305 ± 21 (D 0 V4 ) / ( D 0 V2) = 21.4 ± 1.6 x 10 -2 Preliminary

12. σ(D 0 )/σ(CC) = 2280/95450/0.88 = = 2.71 ± 0.22 x 10 -2 Fully neutral D 0 decay modes: BR4/BR2 – measured BR4 = 0.1338 BR4 = 0.1338 ± 0.0058 PDG BR2/BR4 ) = 24.1 4.5% (6 prong negligible) BR(D 0 neutrals) = 1-BR4 x(1+ BR2/BR4 ) = 24.1 ± 4.5% (6 prong negligible) Total production cross section: All All D 0 ’s = N V4 /BR4 = 2280 ± 151(stat.) ± 26(stat.eff.) ± 99( BR4 err. ) Relative detection efficiency D 0 /CC = 0.88 Preliminary

13. Study of fragmentation Different strategies to study fragmentation Properties of charm production: NOMAD isolates D* using invariant mass reconstruction For these events, kinematic quantities are well measured, but statistics is low CHORUS uses a high statistics and pure sample of D 0 events obtained by isolating neutral particle decays. However, distributions have to be obtained by an unfolding method.

14. Nomad D* + measurement Step 1: exploit invariant mass combinations Step 2: kinematical cuts Step 3: neural network to reduce combinatorial background Cleanest sample: Neural Net estimator cut at K=0.8735 35+-7.2 events (12 background) Larger statistics: K>0.6 Use decay chain:

15. Study larger statistics sample: Background is combinatorial MC: S+B Data D* mass in clean sample D* yield in CC events (T): Compatible with BEBC

16. p T 2 distribution of charmed particles The transverse momentum of charmed particles wrt the direction of the hadronic system is usually parametrized as Phys. Lett. B 206 (1988) 380-384 NOMAD47-12 events Phys. Lett. B 526 (2002) 278-286 NOMAD

17. Measurement of D 0 momentum Use correlation between opening angle of decay daughters and charm momentum to obtain momentum distribution D Momentum Inverse of geometrical mean of opening angle of daughters Momentum distribution of D0 can be measured by unfolding opening angle distribution (curve is the model in the CHORUS MC) Preliminary

18. NOMAD Z-distribution NOMAD Fits to Collins-Spiller and Peterson:  Also an E531 measurement  Indirect measurements from dimuon data:  CDHS, CCFR, CHARMII, NuTeV, CHORUS CHORUS Preliminary CHORUS: Fit to Peterson formula (dotted curve is MC model)

19. Feynman x distribution Preliminary NOMAD Most charmed particles are produced in the forward region CHORUS

20. Charm fragmentation results Large spread in values Maybe due to different mixtures of charm final states: E531: all charm decays Nomad: D* CHORUS: D 0 Dimuon experiments: weighted by muonic decay mode

21. Measurement of Λ c production A statistical approach using flight length distribution Short flight decay : Λ c enriched sample Long flight decay : D +, D s dominant Two different set of criteria have been adopted. Strategy Flight length in μm MC ΛcΛc D+D+ DsDs Phys.Lett.B 555 (2003) 156 based on 50414  CC

22. Measurement of Λ c production Short flight decay (A) Daughter track : Distance to the muon 5 µm to 30 µm Long flight decay (B) Candidate selection Parent track : distance to the muon < 5 µm Distance between daughter and parent 5µm to 30 µm 1614 events from 50,414 CC events were selected for visual inspection Detector muon 586 events from 56,761 CC events were selected for visual inspection (A) (B) Samples after flight length cut 1 prong 3 prong (A) 40 mm < FL < 400 mm (B) 400 mm < FL < 2400 mm 62 66 133 195

23. Combining short (A) and long (B) decay search,and taking into account efficiency and background: Combining short (A) and long (B) decay search,and taking into account efficiency and background:  c = 861  198 (stat.)  98 (syst.) +140 (QE)  c = 861  198 (stat.)  98 (syst.) +140 (QE) Br(  c 3prong) = (24  7 (stat.)  4 (syst.))  10 -2 Br(  c 3prong) = (24  7 (stat.)  4 (syst.))  10 -2 σ  (  c) /σ(CC)= (1.54  0.35(stat)  0.18 (syst))  10 -2 - 54 σ  (  c)/σ(CC)  Br(  c 3prong)=(0.37  0.10(stat)  0.02(syst))X10 -2 ΛcΛc

24. a)  n   -  c + b)  n   -  c + (  c *+ ) c)  p   -  c ++ (  c *++ ) Quasi-elastic charm production Require 2 or 3 tracks at primary vertex   165° (angle between muon and charm in the transverse plane) Flight length < 200  m (enriched  c sample) Calorimeter energy < 10 GeV and electromagnetic energy < 2 GeV Topological and kinematical selection criteria:  0.6 13 events with a background of 1.7  0.6 (mainly from DIS  c) QE production is about 15% of  c production Phys.Lett.B 575 (2003) 198 based on 46105  CC

25. Energy measured in calorimeter Azimuthal angle Kinematical selection of QE candidates Events in first bin

26. Associated charm production Charged-current Gluon bremsstrahlung c – c W g  D+D+X – One event has been observed and published. Phys. Lett B 539 (2002) 188, CHORUS Coll. In CC interactions

27. c – c g Z Z-gluon fusion D+D+X – Associated charm production NEW In NC interactions AND Gluon bremsstrahlung c – c Z g D+D+X – In the past only one event Observed in E531 emulsion Indirect search performed by NuTeV Production rate (2.6x1.6)x10-3 of CC Systematic search for double decay topologies Events observed in NC and CC interactions with very low background (order 0.1 event)

28. TT #6 P P >0.66 GeV/C @ 90 CL. TT #3 P d4 >2.72 GeV/c @ 90 CL. TT #8, P d2 >4.66 GeV/C @ 90 CL. TT #5, P d1 > 1.39 GeV/C @ 90CL. pl23 pl22 example of NC event example of NC event E=29.9GeV P d3 >3.33 GeV/c @ 90 CL. Both neutral decays inconsistent with two-body decay (acoplanarity)

29. E=36.9 GeV P=-16.9 GeV/c Pl31 pl30 Pl31 pl30 example of CC event example of CC event P d1 >4.70 GeV/c @ 90 CL.(TT #2) P d2 >0.67 GeV/c @ 90 CL. P d2 >0.67 GeV/c @ 90 CL. P d3 >2.32 GeV/c @90 CL.(TT #7) P d2 >1.92 GeV/c @90 CL.(TT #5) P d2 >1.92 GeV/c @90 CL.(TT #5) Evis= 53.8 GeV Both neutral decays inconsistent with two-body decay (acoplanarity)

30. C Charm production in antineutrino interactions N  + = 2725 N  - = 93890 Selected events = 82 found charm = 61 after  reconstruction cut = 32 “1  spectrometer events”  kink > 50 mrad, F.L > 50  m fC-fC- fCofCo = 2.9 + 1.9 - 1.2 (stat)  (  N   + cX)  (  N   + X) = 4.8 % + 1.2 - 0.9 N  = 4374 ± 135 Preliminary Energy dependence

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

32. Angle between leading    and sum of two others DATA All MC Charm->  +     Int. bremsstrahlung Trimuons   no int. bremsstrahlung

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

34. SUMMARY SBL oscillation programme at CERN: – NOMAD final data – CHORUS, final statistics, but phase-II analysis ongoing Many additional measurements (in this talk concentrated on charm physics) – Production cross-sections – Fragmentation functions – Decay properties Other results will be shown by Camilleri