b-ID Status

Andy Haas - Columbia University

on behalf of the b-ID group

Higgs Workshop

April 12, 2007

Certified p17 NN TRFs

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:

Negative tag rate now determined using the COMB skim with !isEM cut applied

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

Analyzers should use certified TRFs on light-jet MC for p17 publications!

https://plone4.fnal.gov/P1/D0Wiki/object-id/bid/bidnnp17cert

All jets

Jet EMF<0.8

TRFs and JSSR

Fabrice pointed out that it's important to run BTagProcessor after JSSR

Otherwise pT>15 for taggability has different meaning in data vs. MC

Result is to enhance the number of taggable jets at low pT

Is now the certified procedure for p17 (and p20) publications!

https://plone4.fnal.gov/P1/D0Wiki/object-id/bid/bidjssr

Old, btagging->JSSR

New, JSSR->btagging

1 b-tags (L4)

pT of second-leading jet (GeV)

Old, btagging->JSSR

New, JSSR->btagging

Better agreement (at low pT) when tagging smeared MC jets...

pT of second-leading jet (GeV)

>=2 b-tags (L4)

b-ID Issues

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

Taggability Issues

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

Will be done in time for p20 analyses
(i.e. within ~1 month)

Ratio of taggability for

all jets / PV jets

p20 NN Certification

p20 NN certification (Sarah Schlobohm + Andy Haas + Dale Johnston)

Need to make sure we understand how to run the certification macros (nn_cert)

Compare:

Certified p17 NN plots (from p17 team = Tim/Stephen/Miruna)

Re-cert p17 data / MC certification plots (by p20 team)

New p20 data / p17 MC certification plots (by p20 team)

Will take only ~1 week to run p20 data/MC certification once samples are available!

We expect that the initial p20 certification will use the (final) p17 JES

Hopefully the p20 JES will not be significantly different
(otherwise, corrections could be made in CAFe)

p17 (re-cert)

p20 data/ p17 MC

p20 NN Certification

p17 (re-cert)

p20 data/ p17 MC

Super-duper-extra preliminary !

Things look OK, certification “works”

Need re-processed data before we see a higher efficiency in data?

Also competing with SMT aging and tracking luminosity effects...

Next step: include vertexing improvements from Yvonne, and compare
(see backup slide...)

p20 NN Certification

p20 NN certification (Sarah Schlobohm + Andy Haas + Dale Johnston)

In the meantime, study p20 data (and MC – not shown in this talk)

Important to properly account for new v15 trigger biases

>=2 jets with pT>10 GeV (skim, uncorrected pT)
>=1 jet matched in dR<0.7 to medium muon with pT>4 GeV

Trigger turn-on at 20 GeV

Trigger turn-on at 15 GeV

muon pT

looks nicely

unbiased

dR matching

looks as

expected

bID skim

bID skim

bID skim

bID skim

p20 NN Certification

And look at “fake tag” samples -> QCD and EM skims

Have also studied DQ, jet/muon eta, phi, etc. for all these samples

Plenty of jets down

to low pT (<15 GeV)

muon pT is OK

dR matching OK

EM skim

EM skim

EM skim

QCD skim

Wacky pT distribution,

various trigger thresholds

But plenty of jets at all pT

muon pT is OK

dR matching OK
(sharper due to
higher jet pT)

QCD skim

QCD skim

Continuous NN Output

Several people have expressed interest in using the continuous b-ID NN output as a variable for input to a NN event selection

Not an easy thing to do right!

MC and data do not give the same NN output shape!

There are several plausible methods for correcting the shape

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

Please email if interested in working on this -> (haas@fnal.gov)

Off by a factor of 2 at

high NN output

And there's more fakes

in data at low NN output

Things are in pretty good shape

In p17 we're fixing and understanding many 5-10% uncertainties / biases

Lots of other recent work I haven't mentioned!!!

Luminosity / time dependence, high-luminosity studies, p20 MC, etc.

Need more involvement from people in physics groups...

Many small issues that can be solved with ~1 month of work each
(tau TRFs, for example)
Will improve the quality of your analysis!

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

Optimized / improved vertexing, NN muon-jet tagger, JLIP L0 usage, etc.

p20 certification work has started, and things are going relatively smoothly

Schedule will be driven by (reprocessed) data and (good) MC availability

All efforts are being made to reduce the time needed from the day samples are available to preliminary certification

b-ID Status

Backup / Details

b-ID Improvements

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

Andy Haas

2004-07-07T15:59:13