b-ID Status

p17 NN – v1.2 (Tim, Miruna, Stephen)

CERTIFIED by the certification board – updated D0Note

Main worry was the fake-tag-rate (FTR) – have now changed the procedure:

The negative tag rate is now determined using the COMB skim with the !isEM cut applied

Used to not apply !isEM cut

Systematic error includes the difference between the QCD and EM skims and the difference between the QCD skim with and without the !isEM cut

New light-jet TRFs are being checked into btags_cert

Analyzers should re-b-tag light-jet MC samples before p17 publications!

All jets

Jet EMF<0.8

b-ID Status

TRF discrepancies

studied TRFs for gluon-splitting samples, like Wbb, Zbb

Observes a 5-10% overestimate of the TRF, compared to actual tagging in MC

Finds that it is due to lower b-quark momentum (as a fraction of the jet momentum) in these samples

Need a fix for this..

Use direct MC tagging + scale factor for these samples?

Use different TRFs for these samples?

Taus

No TRF has been measured for taus!

Just using the light-jet fake rate

We know this is wrong. Taus are tagged about as often as charm (after taggability)

5-10%, low pT

b-ID Status

Taggability (Thorsten)

Taggability parameterizer processor

Checked into CVS: btags_cert_caf

Needs to be tested / improved

We are underestimating the taggability for jets from the PV at low pT by 5-10% and 2% at high pT

BTagProcessor is able to apply parameterized taggability

We need to account for different taggability of b,c,tau,light jets

Ratio of taggability for

all jets / PV jets

b-ID Status

SVT Optimization (Yvonne)

Done! D0Note 5265.

Random grid search of taggability and secondary-vertexing parameters

Fix old feature of re-using tracks on vertices

More realistic number of secondaries

Important – input to NN tagger!

Revive the 2-pass vertexing algorithm

Look for a tight vertex first, then a loose one if no tight was found

Better vertex parameters

Input to NN tagger!

Slightly higher efficiency

muon NN tagger for p17? (Hwidong)

Adds ~5% efficiency to b-ID / negligible extra fake rate

Major milestone – have measured the tagging efficiency in data and MC!

Now working on measuring fake-tag-rate

Will use a similar NTR approach?

current operating points

points from search

b-ID Status

p17 NN – v2.0 (Sarah Schlobohm and me) – Do we need this??????

Final JES

Optimized SVT/taggability parameters

p20 NN certification (Sarah + me + Who???)

Running nn_cert over p20 TMB skims!

Can measure b-tagging efficiency and negative-tag-rate in data

Will compare to p17

Can not do full certification without the full set of p20 MC samples

Things are in pretty good shape

We're fixing and understanding many 5-10% uncertainties / biases

EMQCD / QCD NTR ratio

New TRF for Wbb/Zbb type samples

Tau TRF

Taggability things

Need more involvement from people in physics groups... these issues can be solved with ~1 month of work each...

Significant work has gone into improving tagging performance....
will see benefits in p20

Optimized / improved vertexing, NN muon-jet tagger

Some p20 work has started

Certification schedule will be driven by (re-processed) data and MC availability

New co-convener: Don Lincoln

b-ID Status

P.S. : Continuous NN Output

Several people have expressed interest in using the continuous b-ID NN output as a variable

For instance as an input to a NN event selection

This is a good idea

It should replace (and be more sensitive than!) the optimized combination of tight-single/loose-double tag technique

We would be happy to coordinate these efforts through the b-ID group!

Please write me an email if still interested in working on this
(haas@fnal.gov)

Andy Haas

2004-07-07T15:59:13