Report of the Oscillation Working Group

andstatus 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

From Tiem 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 PT~ 50 MeV (PT~97%)

kine= p x IP x ExPT x e->e ~ 22%

– Long decay (DIS-QE)• Electron energy cut (E~90%)

• PT~ 100 MeV (PT~99%)

kine= B2B x E x PTx 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 eCC event found yet in 2008 data! We should expect 10-20 events

Do we need dedicated work for e event search?

→ e

7

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 PT

miss @ the primary vertex to reduce NC contamination and suppress B(→e) Efficiencies: Brick finding, Vertex finding, Trigger and Fiducial Volume cut

ee analysisanalysis ee analysisanalysis

Previous analysis Previous analysis (see arXiv:hep-ph/0210043v1 ) Signal and BG efficiencies:

Signal →e CC→NC NC e beam

0.53 0.53 0.52 0.48 0.53

0.31 0.032 0.34 10-4 7.0 10-4 0.082

= Brick Finding*Vertex Finding*Trigger*Fiducial Volume Cut= Final efficiencies according to the considered smearing

(from Giulia)

8

ee analysisanalysis ee analysisanalysis ConclusionsConclusions (from Giulia)(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

→ 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

Ptmis < 1GeV/c at 1ry vertexLarge 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 τDaughter particle of hadronic interactions

Pt(GeV/c) Pt(GeV/c)

MC MC

12AATA

AATA

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

AATA

h h

Short decay

Long decay

Summary

Hadronic interaction study

Kink detection

MC

MC

Momentum measurement

MC

Scan Forth

Energy reconstruction

Gamma detection

MC

Pointing resolution

Detection efficiency

IP accuracy improvement

14AATA

modedecayh

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 D0 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 ….

• 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

Status of Charm study

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)%

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

NC+

=29.4±2.0

N1p=19±2

N3p=10±1

Nfully neutrals 3±1

N2p 16±0.2

N4p 3.3±0.3

ND0

=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

NC+

=12.9±0.9

N1p=8.4±0.9

N3p=4.4±0.4

Nfully neutrals 1.3±0.4

N2p 7±0.1

N4p 1.5±0.1

ND0

=10.0±0.6

Efficenciesexpected 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

N1p = 0 (1) N2p = 1 (2) N3p = 1(2) N4p = 0

NC+

=3.2±0.3

N1p=2.1±0.3

N3p=1.1±0.1

Nfully neutrals 0.3±0.1

N2p 1.7±0.2

N4p 0.4±0.03

ND0

=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 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 10-15m< 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 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

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+ D0

DS+ 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 eventstop view

beam view

mu

mu

side view

145

541

2.3 GeV/c

1.3 GeV/c

5.5 GeV/c

mu

Found in Bern