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Report of the Oscillation Working Group and status of Charm study

Report of the Oscillation Working Group and status of Charm study. F. Juget – D. Duchesneau Ankara, April 1rst 2009. 1. Tau decay channel study Summary of last Physics coordination meeting Charm study Charm analysis status for 2008 data Strategy for 2008 and 2009 data. 2.

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Report of the Oscillation Working Group and status of Charm study

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  1. Report of the Oscillation Working Group andstatus of Charm study F. Juget – D. Duchesneau Ankara, April 1rst 2009 1

  2. Tau decay channel study • Summary of last Physics coordination meeting • Charm study • Charm analysis status for 2008 data • Strategy for 2008 and 2009 data 2

  3. t→ m • Work from Tiem: • Re-estimation of the efficiency for long decay DIS, using “beamfile” was done – compatible with proposal values • Possible improvement to investigate w.r.t to proposal: • Changing the range of kink angle (see next slide): • Proposal: 20 mrad < q < 500 mrad • Investigate: 10 mrad < q < 700 mrad • Understand efficiency for angles > 500 mrad • Optimized kinematical cuts – study correlation • Investigate decay in plastic base • The efficiency re-estimation will be redone with OpEmurec data • Work already started on likelihood function to separate tau to charm background 3

  4. From Tiem 4

  5. From Tiem 5

  6. t→ e • From Frank • From the proposal estimation of the efficiency investigate where we can improve: • Long decay (DIS-QE) • Electron energy cut (eE~90%) • PT~ 100 MeV (ePT~99%) • ekine= eB2B x eE x ePTx ee->e ~ 83%-84% • For short decay DIS • Track momentum > 1 GeV (ep~ 66%) • IP cut 5-20 micron (depends on Z of vertex in lead) (eIP~45%) • Electron energy cut (eE~79%) • Min PT~ 50 MeV (ePT~97%) • ekine= ep x eIP x eExePT x ee->e ~ 22% Small room for improvement Possible improvement to be investigate 6

  7. t→ e • To be done: • Investigate possible improvement of kinematical cuts (mainly possible in short decay) • Re-estimate all the efficiency using MC and information from 2008 data • Re-estimate and study all the background • Remark: no neCC event found yet in 2008 data! We should expect 10-20 events Do we need dedicated work for ne event search? 7

  8. (from Giulia)  Kinematical Analysis: Variables obtained (Ee, Evis,PTmiss) with a smearing according to OPERA resolutions:  Cut on the visible energy to reduce γ component and the prompt e component from the background  Cut on the number of grains associated with the e-track to reduce B(CC→NC)  Cut on PTmiss@ the primary vertex to reduce NC contamination and suppress B(→e)  Efficiencies: Brick finding, Vertex finding, Trigger and Fiducial Volume cut Previous analysis (see arXiv:hep-ph/0210043v1 ) Signal and BG efficiencies: = Brick Finding*Vertex Finding*Trigger*Fiducial Volume Cut = Final efficiencies according to the considered smearing 8

  9. Conclusions(from Giulia) • Cuts to be re-optimized • Study of vertex location efficiency: full simulation needed, real data comparison Important for QE events • Study of gamma conversion: full simulation needed, real data comparison •  CC data needed to validate the analysis on Evis, PTmiss • Data needed to validate the π/e mis-ID study • Demonstrate the knowledge of the e component in the beam, in order to study e wrt other beam distributions (,) 9

  10. t→ h 10

  11. Overall efficiency of kinematical analysis for th Long Proposal p = DIS 20% QE 28% To reduce hadronic int BG, severe cut is applied. Kinematical analysis at the decay vertex. Kinematical analysis at the primary vertex. Only for HM events LM : low multiplicity, HM : High Multiplicity Pt > 600 MeV/c (most severe cut) Daughter momentum > 2GeV/c Ptmis < 1GeV/c at 1ry vertex Large in NC int, small in CC int. f > p/2 for t candidate AATA 11 11

  12. Pt cut MC MC Daughter particle of hadronic interactions Daughter particle of τ Pt(GeV/c) Pt(GeV/c) Cut with 600 MeV/c in the proposal.  too high? AATA 12

  13. To recover some efficiency Most severe cut is Pt cut. Set lower threshold. 2 approaches • Study of Hadronic interaction. • Pt distribution of the daughter particles from had-int. • Fraction of white kink. • Big uncertainty in MC. • Hopefully to set lower threshold for Pt cut. • Study of gamma reconstruction. • Most of t decay include p0 in decay daughter. • By detecting g from 2ry vertex, reduce background  set lower threshold for Pt cut. AATA AATA 13

  14. Summary t h Long decay MC Kink detection Gamma detection Hadronic interaction study Detection efficiency Short decay Scan Forth g Energy reconstruction Momentum measurement Pointing resolution MC MC MC IP accuracy improvement A lot of work to do… AATA AATA 14

  15. t → 3h 15

  16. analysis and charm separation in the 3-prong channel : (D. Duchesneau); report based on Magali’s thesis work • Charm background discrimination in the t3h channel has been studied for the first time at detector level,after vertex reconstruction. • The D0 events have been taken into account with reconstruction inefficiency for each decay channel. • Vertex reconstruction is a key issue for this particular topology • Prospects: • Clear possibility of improvements to be investigated; this analysis should be redone using similar approach but: • adapt the official charm rate and branching fractions • using new more discriminating variables (like phi angle etc…) in the likelihood • using more refined muon misidentification estimates for charm rejection • study a different vertex algorithm as suggested in OPERA Internal note #97 • re-evaluate background (ex Fluka) 16

  17. Conclusion • The work of efficiency estimation has started for each channel • Some work are common for each channel • m ID, vertex reconstruction, kink angle, gamma detection, IP …. • 2008 data has to be used to validate the simulation results (vertex reconstruction, MCS, kink, gamma, Ptmiss, kinematical analysis….) • Simulation and 2008 data will be used to study background

  18. Status of Charm study

  19. (Charm)/(CC)=(4.38±0.26)% ~ 52.1±3.6Events ND0=22.7±1.5 NC+=29.4±2.0 Nfully neutrals 3±1 N1p=19±2 N2p 16±0.2 N3p=10±1 N4p 3.3±0.3 Charm Production 2008 • Number of events in bricks 1690, i.e. 1190 CC • Based on Talks of Dario (Japan) and Francesco (Sorrento) (D0)/(CC)=(1.91±0.13)% neutral charm (C+)/(CC)=(2.47±0.22)% charged charm Inclusive charm production at OPERA energy by Francecso

  20. ND0=10.0±0.6 NC+=12.9±0.9 Nfully neutrals 1.3±0.4 N1p=8.4±0.9 N2p 7±0.1 N3p=4.4±0.4 N4p 1.5±0.1 Efficenciesexpected events in 2008 • Trigger 99.9% • Brick Finding 70-80% • Geometry 96.5% • Vertex localisation 85-90% • Muon requested 80-90% • Decay category • Long ~50%, short ~50% • Charm candidate selection • Muon energy > 1 Gev, primary vertex in plate 56 or lower • 88% of all charm events (from MC) • Reconstruction efficency Not included yet, O(75%) • Overall ~44%  22.9±1.6 Charm Events by Thomas

  21. ND0=2.5±0.1 NC+=3.2±0.3 Nfully neutrals 0.3±0.1 N1p=2.1±0.3 N4p = 0 N1p = 0 (1) N2p = 1 (2) N3p = 1(2) N2p 1.7±0.2 N3p=1.1±0.1 N4p 0.4±0.03 Charm events status • Up to know ~400 events found (in Europe) • ~320 CC events (~25% of the total) • Expected charm:22.9x0.25 = 5.7 ± 0.4 • Charm events found: • Long charged 3 prong Charm decay in Padova • Very short 2 prong in Bern • 3 new candidates: (to be confirmed) - 2 short (1 or 2 prong) and 1 short ( 3 prong) (- 1 in Japan + 1 new)

  22. Charm events status • Charm events number found in 2008 data is lower than the expectation ( 2 (or 5) found – 5.7 expected) • But: • statistic is very low (~25% of the total data analyzed yet) • The expected number is based on efficiency of 44% which should be re-estimated correctly • The statistic will increase (wait the final 2008 analysis) • Comment: • All the charm events were found close to the 1ry vertex with small IP of charm daughter tracks • No long charm decay (more than 2 plates). The actual method for vertex is not dedicated for charm. Large IP tracks are not taken into account. This affect mainly long decay but also short with large IP.  We need a dedicated strategy for charm search for all the 2008 data and for 2009 run

  23. Strategy for charm search • Scanning area 10 plates downstream the primary vertex • Vertex is within 5 plates then 5 plates more are needed to reconstruct the charm vertex (~1 cm2) • more plates required to reconstruct kinematics of charm decay • Improve the detailed analysis of primary vertex by scanning lab • Not only scanning, but also small analysis at that time • Need dedicated tools for kink search and 2ry vertex search • See next slide for procedure proposal (by Tomoko) - Look for tracks with 10-15mm< IP< 500 mm w.r.t. 1ry vertex - Possible with 3D viewer eda.C developped by Ariga • The previous analysis can be (has to be) performed offline with already scanned data • Kinematical analysis (offline)

  24. Procedure after primary vertex location Proposal by Tomoko and Ariga Using the interactive 3D viewer eda.C (latest version) • Select all the tracks and decay daughters (both for short and long decay) with: - IP w.r.t. 1ry < 500 micron and start within 5 plates from 1ry - Rejecting Penetrated tracks. • Check 1st segment of the track by scan or eyes  Reject e-pairs (when 2 BT found close). • For the selected tracks: • Make sure the tracks are measured at the vertex plate (in the closest emulsion w.r.t the 1 ry vertex ) • If not, Measure all the tracks by Prediction scan or Manual Check, in order to minimize measurement error for IP calculation for short decay search. • follow down all 1ry tracks (in Scan Forth), for small kink search and for very long decay

  25. Procedure after primary vertex location Proposal by Tomoko and Ariga 1. SHORT DECAY SEARCH: IP check and 2ry vertex search - if all IP < 10 micron  all tracks attached to 1ry vertex - NO SECONDARY (more analysis using momentum is needed to reduce the IP value) - if one track or more have IP > 10 micron  possible decay  Check minimum distance track by track (all pairs) - (study momentum dependence)  to confirm 2ry track  Re-calculate vertex position considering momentum (reject low momentum)  Calculate IP error at primary, for 2ry tracks. if IP > 3s , preliminary decay candidate 2. LONG DECAY: - if there are long decay daughter candidates, search for parent with eda: - single base-track search (for the future, micro-track search) - follow down all 1ry tracks (in Scan Forth), for small kink search and for very long decay

  26. Conclusion • Charm expected for 2008 assuming 44% efficiency and using 25% of the data: 5.7 ± 0.4 (only in Europe) • Found events: 2 (5) confirmed • This number is a rough estimation, we need: • Correctly estimate the efficiency • Use more statistics • Japanese data not yet taken into account • Perform a systematic search for charm • Strategy to have a dedicated search was proposed • Should be applied for already scanned 2008 data and 2009 • Next to be done (soon): • Re-estimate the charm expectation using all scanned data (Europe+ Japan) • Re-estimate the efficiency

  27. BACKUP

  28. Strategy for charm search IP of charm daughter track w.r.t. to the 1ry vertex D+ 1 prong D+ 3 prong

  29. Decay length D+ D0 c+ DS+ Decay will be within 5 plates of primary vertex, so we have to scan at least 10 plates to see it 30

  30. First charm events Found in Padova

  31. First charm events side view top view 145 mu mu 541 beam view 2.3 GeV/c 1.3 GeV/c mu Found in Bern 5.5 GeV/c

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