1. Andrea Bocci Riccardo Ranieri Massimiliano Chiorboli Alessia Tricomi
Catania Lepton Tag
Andrea Bocci Riccardo Ranieri
INFN and Università di Firenze
Massimiliano Chiorboli Alessia Tricomi
INFN and Università di Catania
CMS Tracker Week bTau Meeting
20th July 2004

2. Soft Lepton Tag
Based on identification of the soft leptons from semileptonic B-meson decays
we studied only leptons=muons case
Efficiency of soft lepton tagging limited by the fraction of B-meson decays containing leptons (17%)
Provide a valuable complement with respect to the impact parameter tagging
Preliminary studies at parton level presented at bTau Workshop in Bari (28th May-1st June)
Now first very very preliminary results with ORCA reconstruction
bTau Meeting
20th July 2004
Catania Lepton Tag

3. The test samples di-jets from Christian’s test samples
2500 b, 4750 c, [5000 udsg]
80<pT[GeV/c]<120
no pileup
QCD jets for ttH background (6500 evts processed)
120<pT[GeV/c]<170
cross section: σ=3.82x10-4 mb
Kinematic Selection: ε=5.70x10-2
at least 4 jets
ΣETjet>300 GeV
jets: ET1,2>40 GeV; ET3,4>30 GeV
more details from Susannna’s talk on MC requests for ttH channel studies talks/030603/Susanna.pdf ^ - ^ -
bTau Meeting
20th July 2004
Catania Lepton Tag

4. Reconstruction Studies done with ORCA_8_2_0
Reconstruction of RecMuon objects
L3 Muon Reconstructor
RecQuery query ("L3MuonReconstructor");
no further thresholds applied
Reconstruction of JetWithTracks objects
L2 Kt jet algorithm
RecQuery jetFinder ("PersistentJetFinder");
jetFinder.setParameter ("JetAlgorithm", 4); // Kt=4
Tracks in cone ∆R<0.3 around jet axis
RecQuery query ("BTagJetWithTracksAlgo");
query.setComponent ("JetFinder", jetFinder);
query.setComponent ("TrackFinder", RecQuery(“CombinatorialTrackFinder”));
query.setParameter ("deltaRCut", 0.3);
bTau Meeting
20th July 2004
Catania Lepton Tag

5. Monte Carlo Truth Muons Jets
information on the origin of the muon (i.e. “mother” particle of the generated muon)
information on the origin of the decay chain (i.e. the particle which originates the decay chain)
to separate bμ from bcμ
some problems with u,d,s,g, results need better understanding
Jets
we used Christian’s BReco/BTagMCTools package
associates main parton to the reconstructed jet and assigns jet flavour
some modifications inside JetIdentifier and MCParton/LundCode classes
bTau Meeting
20th July 2004
Catania Lepton Tag

6. L2 Jet Axis Resolution - from ttH QCD background
Jet axis η-φ measurements resolution improved with tracks
weighted mean on tracks pT, see DAQ-TDR section
before: σ(η)=0.068 σ(φ)=0.060
after: σ(η)=0.039 σ(φ)=0.036
bTau Meeting
20th July 2004
Catania Lepton Tag

7. Muon pTrel and pTrel,excl
Entries/bin
Entries/bin
Muon transverse momentum relative to jet axis
left: pTrel relative to measured jet momentum direction
vector pjet direction
right: pTrel,excl relative to jet momentum lepton excluded
vector pjet-pμ direction   
bTau Meeting
20th July 2004
Catania Lepton Tag

8. Direct vs Cascade b decays
pTrel,excl>0.8 GeV/c
pTrel>0.8 GeV/c
Efficiency of bμ chain versus Rejection of bcμ chain
bTau Meeting
20th July 2004
Catania Lepton Tag

9. b-c comparison pTrel>3.2 GeV/c pTrel,excl>3.2 GeV/c
Efficiency of bμ+bcμ versus Rejection of cμ
bTau Meeting
20th July 2004
Catania Lepton Tag

10. Conclusion excerpt from ToDo list (bTau Workshop): First step:
Start with muons
Look for muon inside jet tracks and evaluate pTrel or pTrel,excl and IP for muon candidate
pTrel and pTrel,excl done but… problems with samples
too few events
MC info on u,d,s,g to be better understood
The bulk of the code is there, we miss only the last point: Impact Parameter
coming soon
WE NEED MORE EVENTS !!!
bTau Meeting
20th July 2004
Catania Lepton Tag