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

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

  →  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 <  mrad –Investigate: 10 mrad <  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

From Tiem 4

5

From Frank –From the proposal estimation of the efficiency investigate where we can improve:   → e – For short decay DIS Track momentum > 1 GeV (  p ~ 66%) IP cut 5-20 micron (depends on Z of vertex in lead) (  IP ~45%) Electron energy cut (  E ~79%) Min P T ~ 50 MeV (  PT ~97%)  kine =  p x  IP x  E x  PT x  e->e ~ 22% – Long decay (DIS-QE) Electron energy cut (  E ~90%) P T ~ 100 MeV (  PT ~99%)  kine =  B2B x  E x  PT x  e->e ~ 83%-84% Small room for improvement Possible improvement to be investigate 6

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 e CC event found yet in 2008 data! We should expect events  Do we need dedicated work for e event search?   → e 7

 Kinematical Analysis: Variables obtained (E e, E vis,P T miss ) 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 P T the primary vertex to reduce NC contamination and suppress B(  →e)  Efficiencies: Brick finding, Vertex finding, Trigger and Fiducial Volume cut Previous analysis Previous analysis ( see arXiv:hep-ph/ v1 ) Signal and BG efficiencies: Signal  →e  CC→  NC  NC e beam    = Brick Finding*Vertex Finding*Trigger*Fiducial Volume Cut  = Final efficiencies according to the considered smearing (from Giulia) 8

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 E vis, P T miss 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

  → h 10

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

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

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  decay include  0 in decay daughter. – By detecting  from 2ry vertex, reduce background  set lower threshold for Pt cut. 13AATA

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

 → 3h 15

Charm background discrimination in the   3h channel has been studied for the first time at detector level, after vertex reconstruction. The D 0 events have been taken into account with reconstruction inefficiency for each decay channel. Vertex reconstruction is a key issue for this particular topology  analysis and charm separation in the 3-prong channel : 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 (D. Duchesneau); report based on Magali’s thesis work

Conclusion The work of efficiency estimation has started for each channel Some work are common for each channel –  ID, vertex reconstruction, kink angle, gamma detection, IP … 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

Status of Charm study

Charm Production 2008 Number of events in bricks 1690, i.e CC –Based on Talks of Dario (Japan) and Francesco (Sorrento) (D 0 )/(CC)=(1.91±0.13)% Inclusive charm production at OPERA energy neutral charm (C + )/(CC)=(2.47±0.22)% charged charm (Charm)/(CC)=(4.38±0.26)% ~ 52.1±3.6 Events N C + =29.4±2.0 N 1p =19±2 N 3p =10±1 N fully neutrals 3±1 N 2p 16±0.2 N 4p 3.3±0.3 N D 0 =22.7±1.5 by Francecso

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 N C + =12.9±0.9 N 1p =8.4±0.9 N 3p =4.4±0.4 N fully neutrals 1.3±0.4 N 2p 7±0.1 N 4p 1.5±0.1 N D 0 =10.0±0.6 Efficencies expected events in 2008 by Thomas

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) Charm events status N 1p = 0 (1)N 2p = 1 (2)N 3p = 1(2) N 4p = 0 N C + =3.2±0.3 N 1p =2.1±0.3 N 3p =1.1±0.1 N fully neutrals 0.3±0.1 N 2p 1.7±0.2 N 4p 0.4±0.03 N D 0 =2.5±0.1

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 Charm events status

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 cm 2 ) –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  m< IP< 500  m 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)

Procedure after primary vertex location 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 1 st 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 Proposal by Tomoko and Ariga

Procedure after primary vertex location 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 > 3 , 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 Proposal by Tomoko and Ariga

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

BACKUP

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

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

First charm events Found in Padova

First charm events top view beam view mu side view GeV/c 1.3 GeV/c 5.5 GeV/c mu Found in Bern