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Short Baseline neutrino experiments

Short Baseline neutrino experiments. Outline Status of oscillation experiments Charm production Summary. Jaap Panman, CERN. Neutrino 2004, Paris, 15 June 2004. Oscillation searches. In this talk concentrate on CERN programme, other experiments are covered by other speakers.

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Short Baseline neutrino experiments

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

  2. Oscillation searches In this talk concentrate on CERN programme, other experiments are covered by other speakers. • MOTIVATION of the CERN nm - ntprogramme: • 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. Neutrinobeam West Area Neutrino Facility at CERN SPS 450 GeV CHORUS, NOMAD Wide Band Beam • 5.06  1019 POTs (1994-1997) • <Enm> ~ 27 GeV • <L> ~ 0.6 km • Prompt nt : negligible <L>/<E> ~ 2  10-2 km/GeV  Dm2 > 1 eV2

  4. NOMAD nt detection by kinematical selection

  5. CHORUS nt nm, (po’s) m-,h- t path nt kink vertex n beam -54 mm -36 mm -21 mm Red frame: ~30x40 mm2 0 mm nt detection by decay KINK recognition Calorimeter Air-core magnet Spectrometer n • Active target • Nuclear emulsion • Sci-Fi tracker Veto

  6. Status of oscillation into nt ne – nt nm – nt NOMAD data: final - CHORUS phase-II not yet finished

  7. Search for nm–ne 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 NOMAD result rules out the LSND allowed region with Dm2 above 10 eV2 Define ratio of electron and muon neutrino CC events Events are compatible with known sources No evidence for oscillations

  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 1 Location of n interaction vertex guided by electronic detector. 2 2 Full data taking around n interaction vertex called Netscan Volume : 1.5 x 1.5 mm2 x 6.3 mm Angular acceptance : 400 mrad ~ 11 minutes / event 3 Offline tracking and vertex reconstruction Reconstruct full vertex topology At least 2-segment connected tracks Track segments from 8 plates overlapped Eliminate passing through tracks

  11. I.P. Detector muon Preliminary Measurement of D0 production Phys. Lett. B 527 (2002) 173, based on ~25% of statistics NOW: full sample: 95450 CC events Candidate selection • Primary track matched to detector muon • Daughter track matched to detector track • 3 ~ 13 μm < I.P. wrt. 1ry vtx < 400 μm Confirmed D0sample 2 prong (V2) 841 (background: 35) 4 prong (V4) 227 (no background) Selection efficiencies V2 : 56.3 ± 0.5 x 10-2 V4 : 74.2 ± 0.9 x 10-2 (D0 V4 ) / ( D0 V2) = 21.4 ± 1.6 x 10-2 BG subtracted, efficiency corrected V2 1426 ± 52 V4 305 ± 21

  12. Preliminary Fully neutral D0 decay modes: BR4/BR2 – measured BR4 = 0.1338 ± 0.0058 PDG BR(D0neutrals) = 1-BR4 x(1+ BR2/BR4 ) = 24.1 ± 4.5% (6 prong negligible) Total production cross section: All D0’s = NV4/BR4 = 2280 ± 151(stat.) ± 26(stat.eff.) ± 99(BR4 err.) Relative detection efficiency D0/CC = 0.88 σ(D0)/σ(CC) = 2280/95450/0.88 = = 2.71 ± 0.22 x 10-2

  13. Study of fragmentation Different strategies to study fragmentation Properties of charm production: CHORUS uses a high statistics and pure sample of D0 events obtained by isolating neutral particle decays. However, distributions have to be obtained by an unfolding method. NOMAD isolates D* using invariant mass reconstruction For these events, kinematic quantities are well measured, but statistics is low

  14. Nomad D*+ measurement Use decay chain: 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

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

  16. The transverse momentum of charmed particles wrt the direction of the hadronic system is usually parametrized as • Phys. Lett. B 206 (1988) 380-384 • NOMAD 47-12 events • Phys. Lett. B 526 (2002) 278-286 pT2 distribution of charmed particles NOMAD

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

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

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

  20. Charm fragmentation results Large spread in values Maybe due to different mixtures of charm final states: • E531: all charm decays • Nomad: D* • CHORUS: D0 • Dimuon experiments: weighted by muonic decay mode

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

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

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

  24. Quasi-elasticcharmproduction Phys.Lett.B 575 (2003) 198 based on 46105 CC a) n -c+ b) n -c+ (c*+) c) p -c++(c*++) Topological and kinematical selection criteria: • 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 13 events with a background of 1.70.6 (mainly from DISc) QE production is about 15% of c production

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

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

  27. Z-gluon fusion   – c Z  n g Z – c D+D+X – c g – c D+D+X Associated charm production NEW In NC interactions • 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) AND Gluon bremsstrahlung

  28. example of NC event E=29.9GeV Both neutral decays inconsistent with two-body decay (acoplanarity) TT #5, Pd1> 1.39 GeV/C @ 90CL. TT #8, Pd2>4.66 GeV/C @ 90 CL. Pd3>3.33 GeV/c @ 90 CL. TT #3 Pd4>2.72 GeV/c @ 90 CL. TT #6 PP>0.66 GeV/C @ 90 CL. pl23 pl22

  29. example of CC event Evis= 53.8 GeV E=36.9 GeV P=-16.9 GeV/c Both neutral decays inconsistent with two-body decay (acoplanarity) Pd1>4.70 GeV/c @ 90 CL.(TT #2) Pd2>0.67 GeV/c @ 90 CL. Pd2>1.92 GeV/c @90 CL.(TT #5) Pd3>2.32 GeV/c @90 CL.(TT #7) Pl31 pl30

  30. N= 4374 ± 135 fCo + 1.9 = 2.9 (stat) fC- - 1.2 (N +cX) + 1.2 = 4.8 % - 0.9 (N +X) 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 Energy dependence Preliminary

  31. Trimuon events in m CC interactions • CDHS and HPWF (1978): ~100 m- m- m+ events • - origin largely unknown • CHORUS: • ~6x106 2m calorimeter triggers • observed: 42 m- m- m+, 3m- m+ m+ (Pm > 5 GeV/c) • Detailed Monte-Carlo (LEPTO/JETSET/GEANT) • 4x106 events with full detector simulation • present knowledge of production rates and • m-decays of h, r, w, h’, f • data-MC validation using 2m events (known origin) • data-MC comparison for 3m event sample

  32. DATA All MC Charm-> + -/- Int. bremsstrahlung Angle between leading -and sum of two others Trimuons • >900 noint. bremsstrahlung

  33. MC 2 validation P and  well reproduced main 3 sources MC -  -  + predictions Charm-> + -/-decay8.32.8 Internal bremsstrahlung(theoretical) 8.64.5 40 Observed in experiment: 42 -  -  + Trimuons 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

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