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b Identification for D
• Responsibilities in the group bcId:
– bcJetReco/bcjet/bcJetChunk
–
–
–
–
–
–
bcjet_analyze
bc_eTagReco
bc_muTagReco
bc_impTagReco
bc_vtxTagReco
bc_likeTagReco
– MC Production
May 29th, 2001
R.Van Kooten
R.Van Kooten, P.Demine
G. Steinbrueck, F.Baudette
O.Peters, V.Jain
F.Tilthaut, B.Wijngoarden
A.Schwarzman, M.Narain
P.Demine, A.Lucotte
P.Demine, A.Lucotte
P. Demine (ISN Grenoble)
1
Documentation
http://www-d0.fnal.gov/~d0upgrad/d0_private/
/software/bid/review_2001.html
May 29th, 2001
P. Demine (ISN Grenoble)
2
Primary vertex
efficiency
Track Reconstruction
Track selection -> Ntrk
Ntrk>2
No
Stop
Yes
Fit set of Ntrk tracks
Find 2max=
Max{2(Ntrk)- 2(Ntrk-1)}
Ntrk=Ntrk-1
Nrej=Nrej+1
Yes
2max > max
Ntrk = Nrej
No
Save Vertex
May 29th, 2001
P. Demine (ISN Grenoble)
3
Secondary vertex
Track Reconstruction
Tracks selection:
- SMT hits number
- pT > 500 MeV/c
Track selection -> Ntrk
Form 2-track seed
Good seed
No
Yes
Fit set of Ntrk tracks
Find 2min=
Max{2(Ntrk+1)- 2(Ntrk)}
Ntrk=Ntrk+1
Yes
2min < max
No
Save Vertex
May 29th, 2001
P. Demine (ISN Grenoble)
4
Tagging with vtx: Algorithm
•
•
•
•
Reconstruct primary vertex.
Reconstruct secondary vertices.
Reconstruct calorimeter jets.
Match secondary vertices to jets.
a) For each vertex:
•
•
Find the closest jet in R
If R < 0.3, the vertex is associated to the jet and
removed from the list of vertices.
b) Go to (a) until no more vertices remain in the list.
•
Tag jets based on the decay length of the
matched vertices.
May 29th, 2001
P. Demine (ISN Grenoble)
5
bc_vtxTagreco.rcp
// 2: Imp. param, 9: Kalman filter
int VertexType = 9
//dR for vertex-jet matching
float DeltaR = 0.3
// decay length (r-phi)
float DecayLengthRPHI = 2.5
// decay length (z)
float DecayLengthZ = 3.0
// decay length significance
float DecayLengthSignificance = 0.0
May 29th, 2001
P. Demine (ISN Grenoble)
6
Tag with vtx: Technicalities
• Algorithm is implemented in the
bc_vtxTagreco package;
• Documentation web page:
http://www-d0.fnal.gov/~sch/bid.html
May 29th, 2001
P. Demine (ISN Grenoble)
7
Tagging with Impact Parameter
• Use b-hadron long lifetime without
reconstructing secondary vertex (to gain
efficiency)
• Consider compatibility of “collection of
tracks” (jet) with primary vertex
• Use decay length significance of tracks:
Jet direction
Track direction
Decay length
dca
May 29th, 2001
vertex
P. Demine (ISN Grenoble)
8
Tagging with dca: Algorithm
1. Select best primary vertex for each jet
2. Select tracks:
1.
2.
3.
4.
5.
6.
(Quality of track fit)
Number of track hits (total / SMT)
Track pT
|2D Impact Parameter|
(V0 Rejection)
(Study further cuts)
3. Calculate PV probability for each track,
based on decay length significance
distribution
4. Combine tracks in jet to form
discriminant
May 29th, 2001
P. Demine (ISN Grenoble)
9
Jet discriminant
•
•
•
Simplest approach: tag jet with a minimum
number of tracks that have significance
exceeding a certain value
Simple product of probabilities:
D = -ln, = (Pi)
…will yield larger values as #tracks increases
Default, independent
of #tracks:
ntracks 1
i
D = -lnP, P Π lnΠ/i!
i0
ntracks
Π Π
Pi
i1
May 29th, 2001
P. Demine (ISN Grenoble)
10
Tag with dca: Technicalities
• Algorithm is implemented in the
bc_impTagreco package;
• Documentation web page:
http://www-d0.fnal.gov/~dwijngaa/btag/
http://www-d0.fnal.gov/~filthaut/btag/vrev0401.ps
May 29th, 2001
P. Demine (ISN Grenoble)
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Tag with : Algorithm
• Reconstruct calorimeter jets.
• Take the muon closest to the jet axis
direction within a 0.7 cone.
• Calculate the PTRel and Pμ / Ejet
variables with this muon.
• Use cut values to distinguish b jets
from background:
– 1 GeV/c < PTRel < 5 GeV/c
– 0.15 < Pμ / Ejet <0.5
May 29th, 2001
P. Demine (ISN Grenoble)
12
Tag with : Tagging Variables
• Currently using:
μ
– PTrel
Pμ2
2
(Pμ Pjet )
2
Pjet
– P / Ejet
• Possible other tagging variables:
– DCA of muon
– PLRel
– PTRel significance
May 29th, 2001
P. Demine (ISN Grenoble)
13
PTRel tagging variable
T itle:
T itle:
Creator:
ROOT Vers ion2.25/03
Preview:
T his EPS pic ture was not s aved
with a preview i nc luded i n i t.
Comment:
T his EPS pic ture wi ll pri nt to a
Pos tScri pt printer, but not to
other types of printers.
Creator:
ROOT Vers ion2.25/03
Preview:
T his EPS pic ture was not s aved
with a preview i nc luded i n i t.
Comment:
T his EPS pic ture wi ll pri nt to a
Pos tScri pt printer, but not to
other types of printers.
generator level
May 29th, 2001
reconstructed jets and
muons
P. Demine (ISN Grenoble)
14
Pμ / Ejet tagging variable
T itle:
T itle:
Creator:
ROOT Vers ion2.25/03
Preview:
T his EPS pic ture was not s aved
with a preview i nc luded i n i t.
Comment:
T his EPS pic ture wi ll pri nt to a
Pos tScri pt printer, but not to
other types of printers.
Creator:
ROOT Vers ion2.25/03
Preview:
T his EPS pic ture was not s aved
with a preview i nc luded i n i t.
Comment:
T his EPS pic ture wi ll pri nt to a
Pos tScri pt printer, but not to
other types of printers.
generator level
May 29th, 2001
reconstructed jets and
muons
P. Demine (ISN Grenoble)
15
Tag with : Technicalities
• Algorithm is implemented in the
bc_muTagreco package;
• Documentation web page:
www-d0.fnal.gov/nikhef/muonbtag/analyses/ttbar/
/d0note_btag.doc
May 29th, 2001
P. Demine (ISN Grenoble)
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Tagging b with electrons
• Use the electron from the decay of the b
quark to tag the b jet
• Challenge: Soft electrons inside jets.
SEmReco with the road method
• Need good tagging variables: pTrel,
p(track)/E(electron)
May 29th, 2001
P. Demine (ISN Grenoble)
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Tagging with e: Algorithm
• Find all SemParticles > 2 GeV inside the
jet (R < 0.7)
• Sort according to quality:
–
–
–
–
3 EM and PS match,
2 EM match,
1 PS match,
0 no match.
• If there is more than one track of the
highest quality present, sort in pTrel
• Use the highest quality, highest pTrel track
to tag the jet.
May 29th, 2001
P. Demine (ISN Grenoble)
18
PTrel for Z->bb
generator level (except
light quarks)
May 29th, 2001
reconstructed jets and
electrons
P. Demine (ISN Grenoble)
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bc_eTagreco.rcp
// pt cut for tracks
float Tagtrackptcut = 1.5
//dR for SEMParticle (track) in Jet
float drTrackJetCut = 0.7
// minimum ptrel for a tag
float Ptrelcut = 0.0
// minimum p(track)/E(jet)
float poveECut = 0.0
// 0 no, 1 PS, 2 EM, 3 EM+PS
int minSemMatchQual = 2
May 29th, 2001
P. Demine (ISN Grenoble)
20
Tag with e: Technicalities
• Algorithm is implemented in the
bc_eTagreco package;
• Documentation web page:
http://www-d0.fnal.gov/~steinbru/d0_private/etag/
/bc_eTagReco.html
May 29th, 2001
P. Demine (ISN Grenoble)
21
Likelihood: Algorithm
• For every jet in event:
– find secondary vertices in jet cone
ΔR(jet,vtx ) Δφ 2 Δη 2 0.6;
– select the vertex with max(Mvtx);
– find muon in jet cone
ΔR(jet,muo n) Δφ 2 Δη 2 0.7;
– calculate likelihood using different
probability tables for different || - PT
regions.
May 29th, 2001
P. Demine (ISN Grenoble)
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Likelihood: Definition
L
p( x | b jet)
p( x | uds jet) n p( x | c jet) p( x | b jet)
x
nuds
c
x
x
x
H
f
(
x
|
H
)
P
if a value is found,
p(x|H)
H
1
P
otherwise
f(x|H) is the probability density function of
discriminating variable
P H probability to find discriminating function value
Note: in current version nuds = 1 and nc = 0
May 29th, 2001
P. Demine (ISN Grenoble)
23
Discriminating variables
• Decay length significance:
(x0 x1) ( y0 y1)
Lxy
2
2
2
2
σLxy
(x0 x1) (σx0 σx1) ( y0 y1) (σy0 σy1)
2
2
• Secondary vertex mass:
2
2
M vtx M ch
PchT
PchT
• momentum transverse to jet direction:
μ
PTrel
Pμ2
May 29th, 2001
2
(Pμ Pjet )
2
Pjet
P. Demine (ISN Grenoble)
24
Likelihood: Technicalities
• Algorithm is implemented in the
bc_likeTagreco package;
• Probability tables are generated using
bcjet_like_db package;
• Documentation web page:
http://isnwww.in2p3.fr/d0/bcid/doc/liketagreco.html
May 29th, 2001
P. Demine (ISN Grenoble)
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bcjet_analyze: Algorithm
• Loop over bcJet objects in event:
– fill blocks with information from bcJet
related objects:
•
•
•
•
•
•
calorimeter jet;
secondary vertices in jet cone;
electron associated with jet;
muon associated with jet;
reconstructed tracks associated with jet;
reconstructed tracks associated with
secondary vertices;
• impact parameter tagger;
• likelihood tagger.
May 29th, 2001
P. Demine (ISN Grenoble)
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bcjet_analyze: Advantages
• bcjet_analyze has
– modular structure;
– simple interface;
• new modules can be added very
easily;
May 29th, 2001
P. Demine (ISN Grenoble)
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bcjet_analyze.rcp
• What to do ?
–
–
–
–
–
–
–
–
–
–
–
–
bool
bool
bool
bool
bool
bool
bool
bool
bool
bool
bool
bool
doEvent = true
doJet = true
doMuon = true
doElec = true
doVtxFit = true
doVtxRec = true
doLikl = true
doTrkJet = true
doTrkVtx = true
doMC = true
doImp = true
doImpTrk = true
• Output file
– string hbk_file = "bcjet.ntpl"
– string nt_manager = "ROOT" // " HBOOK"
May 29th, 2001
P. Demine (ISN Grenoble)
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bcjet_analyze: Documentation
• NTuple content description is located at:
http://isnwww.in2p3.fr/d0/bcid/bcjetntpl0804.html
May 29th, 2001
P. Demine (ISN Grenoble)
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