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Cross section measurements in CHORUS

Cross section measurements in CHORUS. Andrei Artamonov ITEP, Moscow. NuInt04, Gran Sasso , Italy 17 – 21 March 2004. CHORUS detector. Active target. Air-core magnet.  p/p = 0.035 p (GeV/c)  0.22. -nuclear emulsion target (770kg) -scintillating fiber tracker. .  p/p = 10 – 15%

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Cross section measurements in CHORUS

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  1. Cross section measurements in CHORUS Andrei Artamonov ITEP, Moscow NuInt04, Gran Sasso , Italy 17 – 21 March 2004

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

  3. Targets • Emulsion (1 m precision -> decay topology) ET • 770 kg, 4 X0 • 2x106 CC ν interactions, 1994-1997 • Calorimeter CT • 112 ton, lead, 5.2 , • 1.5x107 CC ν interactions, 1994-1998 • Special 4 targets 4T • 100x4 kg, marble, plastic, Fe, Pb • ~106 CC ν interactions, 1998

  4. Non-oscillation physics in CHORUS • Charm • D0, Λc, QE charm production • cc CC/NC production • BR->m, fragmentation functions • anti-neutrino charm production • total charm production cross section • Structure functions • Dimuons • Trimuons • J/Ψ NC production • Z/A dependence of CC cross-section (ET) (CT) (CT) (CT) (CT) (4T)

  5. 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

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

  7. 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

  8. Z/A dependence of mCC cross-section • Eur. Phys. J. C30 (2003) 159-167 • for the first time 4 targets in the same experiment • were exposed simultaneously • positions rotated to avoid acceptance differences • mCC 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

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

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

  11. Λc production • Phys. Lett. B. 555 (2003) 156-166 • Analysis is based on statistical approach using flight length distribution Short flight decay (40 mm < FL <400 mm): Λ c enriched sample Long flight decay: (400 mm < FL < 2400 mm): D+, Ds dominated sample Λ c D+ Ds Flight length in μm • Analysis has been performed applying two different selections.

  12. m m Λc ~50000 CC events – half of full statistics • Short flight decay (A) Daughter track : distance to the muon 5 µm to 30 µm 1614 events were selected for visual inspection • Long flight decay (B) Parent track ; distance to the muon < 5 µm Distance between daughter and parent 5µm to 30 µm 586 events were selected for visual inspection (A) (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

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

  14. Quasi-elastic charm production 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

  15. I.P. Detector muon NEW 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 Selection efficiencies V2 : 56.3 ± 0.5 x 10-2 V4 : 74.2 ± 0.9 x 10-2 Confirmed D0sample 2 prong (V2) 841 227 4 prong (V4) (D0 V4) / (D0 V2) = 21.4 ± 1.6 x 10-2 BG subtracted, efficiency corrected V2 1426 ± 52 V4 305 ± 21

  16. D0 NEW Fully neutral D0 decay mode: BR4/BR2 – measured BR4 = 0.1338 ± 0.0058 PDG BR(D0neutrals) = 1-BR4 x(1+ BR2/BR4 ) = 24.1 ± 4.5% Total production cross secton: 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

  17. NEW n m W – c g c – D+D+X Associated charm production in CC One event has been observed and published. Phys. Lett B 539 (2002) 188, CHORUS Coll. Charged-current Gluon bremsstrahlung

  18. Z-gluon fusion n n – c Z g – c D+D+X Associated charm production in NC • In the past only one event observed in the E531 emulsion • Production rate ~10-3 normalised to CC • Indirect search performed by NuTeV • Production rate (2.61.6)x10-3 normalised to CC at 154 GeV • Currently a search for this process is in progress in CHORUS

  19. cc Event 81332312 V2&V2 in 0mu 1ry@pl23 Ns=1, Nh=3 V2(1) @pl 23 Dq =96.3 mrad fl= 62.8mm V2(2) @pl 22 fl= 976.6mm Dq =203.4 mrad TT #5 TT #8 TT #3 TT #6 pl23 pl22

  20. cc PLATE 18 PLATE 17 TT TT TT 210µm 140µm 120µm Event 77393952 Ns = 6 Nh = 1 (gray) 4Vee @ pl 17 FL = 884 µm C3 @ pl 17 FL = 426 µm

  21. + 1.2 = 4.8 % s(n N  m+cX) - 0.9 s(n N  m+X) + 1.9 = 2.9 (stat) - 1.2 fCo fC- Nn= 4374 ± 135 PRELIMINARY charm production in antineutrino interactions Nm+ = 2725 Nm- = 93890 Selected events = 82 found charm = 61 after m reconstruction cut = 32 “1m spectrometer events” Qkink> 50 mrad, F.L > 50 mm

  22. mCharm Charm production rate as a function of n energy

  23. Many types of analysis are still in progress MORE NEW RESULTS WILL BE AVAILABLE IN COURSE OF 2004

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