b-ID Status

Andy Haas - Columbia University

on behalf of the b-ID group

Convener's Meeting

May 25, 2007

New TRFs

Tim Scanlon has made new TRFs for p17 JLIP and NN

Extends to higher pT

Separate pT parameterization for each |eta| bin, so smaller systematic uncertainties

Will be added to (p17) btags_cert soon, so can be used in CAFe

We can use the updated nn_cert for p20 certification

Did not affect the bbbbump

b-tag fake rate

b-tag efficiency

TRF W/Z+bb Discrepancies

Studied TRFs for gluon-splitting samples, like W+bb, Z+bb

Observe a 5-10% overestimate of the TRF, compared to actual tagging in MC at low pT

Due to lower b-quark momentum (as a fraction of the jet momentum) in these samples

Yvonne has measured a correction for this

Will be put into BTagProcessor...

You will tell it that you're running on W/Z+bb and the TRF will be corrected

5-10%, low pT

Scale factor for W/Z+bb

Taggability Issues

Thorsten works on the taggability processor

Checked into CVS: btags_cert_caf

BTagProcessor is able to apply parameterized taggability

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

Will be fixed in new processor?

Has made progress on the flavor dependence...

Also may study tau dependence...

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

Ratio of taggability for

all jets / PV jets

15

100

2.5

0

1.2

1.0

1.1

1.0

Taggability for b/c's goes up!

20% at 15 GeV

10% in ICR

To do...

A couple big holes
(in addition to the projects “underway”)

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)

No light-jet data/MC scale factor!

Can not do a “direct tagging” analysis involving light jets

“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

Alan Magerkurth has devised a way to use all 12 NN operating points

Mike Mulhearn will investigate correcting the full output distribution

Inst. Luminosity Dependence

Suneel Dutt

Showed before that NN inputs / outputs are not sensitive to inst. lum.

Taggability on average decreases with increasing inst. lum.

But taggability for “clean” events with <4 PV does not suffer at higher inst. lum.

Can see average number of taggable jets start to fall off around ~150e30

Muon Soft-lepton Tagger (NN)

Hwidong

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

Have measured the tagging efficiency in data and MC!

Modified System8 method used

Now working on measuring fake-tag-rate

Using Negative Tag Rate method based on muon IP significance

Next hurdle is the data/MC scale factors for the muon efficiency and fake rate in the jet

p20 NN Certification

Sarah Schlobohm + Andy Haas + Dale Johnston

Have run several “certifications” so far:

Re-cert p17 data / MC (to cross-check with old p17 certification)

p20 pass1 data / p17 MC

Now running on pass2 data – will be done next week

There were some technical problems switching to pass2
(needed to switch to p21.05.00, new JLIP package)

Currently running with the (preliminary) p17 JES

Testing the p20 preliminary JES (currently have some error messages)

Will switch to p20 JES next time we process the data

Still on schedule for preliminary p20 TRFs by end of June

p17 (re-cert)

p20 data/ p17 MC

Super-duper-extra preliminary !

SF

MC

Data

SF

MC

Data

p20 NN Certification

Dale studies the p20 data samples and understands “biased”/”unbiased” triggers

We must reject events which were triggered only on triggers with PVZ or L3IP terms

Also not using triggers like DiMU, EMMU, tau, etc.

Unbiased

Biased

Many improvements worked on lately, will be available soon:

New TRFs with higher pT range and smaller uncertainties

A correction for W/Z+bb TRFs

A taggability processor, with corrections for b,c,tau jet flavors, nPV cut

Several studies underway:

Use of continuous NN output

Inst. luminosity dependence

Muon soft-lepton tagger is maturing, fake-rate being measured in data

p20 certification on schedule for preliminary (pass2) TRFs by end of June

Will use p17 MC!

Will (likely) use p17 JES

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

current operating points

points from search

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)

Andy Haas

2004-07-07T15:59:13