Some Work on ZH -> mumubb

Andy Haas

Columbia U. / Nevis Labs

ZH->llbb Meeting

October 9, 2007

Z->tautau

Turns out to be negligible

tau->mu ~10%

Z->tautau->mumu ~1%

and 1/3 of the tau energy goes to mu

Very little Z->tautau left in Z mass window...

Z->tautau

Z->tautau

Note Bene

That's it for p17 ZH->mumubb

Working on the p17 ZH->llbb paper

Rest of this talk is studies for a future p17+p20 analysis...

Isolation

Using product scaled (track+cal) iso <0.01

QCD turned out to be a small background

Should probably loosen isolation

Look at mumu mass in “QCD” sample

There are Z's in there...

Isolation

I like a cut of 0.1 (instead of 0.01)

I think 0.4 is getting dangerous, and any higher than that is useless...

Isolation Efficiency

ZH->mumubb (115):

/cafe/tmu : 1000

/cafe/tzmumu : 689

/cafe/tjes : 624

Of the 65 events with 2 muons but no Z

some failed pt cuts on the muon

some failed opposite charge

Probably failed to find the Z muon and picked up a b-decay muon

Using 0.1 isolation instead of 0.01, we got 77 failing after isolation cut, vs. 119

Increase eff. by 4.2%!!!

Cosmic Veto

HZ->mumubb (115):

Without cosmic veto, go from

624

to

648

Increase eff. by 2.4%!!!

No idea what this does to the background...

DCA cuts

HZ->mumubb (115):

Standard:

0.02 cm w/ SMT

0.2cm w/ no SMT

Remove the cuts:

648

to

653

Increase eff. by 0.5%

No idea what this does to the background...

may want to keep the cuts, and drop the cosmic veto???

No Track Match

HZ->mumubb (115):

Remove requirement of central track match... had to hack Zmumu.cpp

(remove dz cut, etc.)

653

to

683

Increase eff. by 3%!!!

No idea what this does to the background...

In ALPGEN Z->mumu 0lp:

477

to

511

Increase of 3.4%

Consistent with ZH->mumubb.

Z Efficiency

Still have only 511/1000 Z->mumu events reconstructed?!

The loose muon efficiency should be ~90% at least, so would have >810/1000 reconstructed?

Look at parton info, to see if the parton muons are there...

Only 80% of each lepton in |eta|<2
for Z->mumu 0lp (64% of Z)

92% of each lepton in |eta|<2
for ZH->mumubb 115 (82% of ZH)

Z->mumu

ZH->mumubb
115 GeV

Isolated Tracks

But could still find the track!

Since we lose 18% of Z's in ZH 115 due to muons in |eta|>2, we can gain a lot by requiring only a track

Working on the code to combine muons and tracks into Z's...

Look at IsoTrack branch for a match to the parton-level lepton...

For now, study Z->mumu only...

When there is a match, the match is very good

Isolated Tracks

The pt resolution is good, of course

The overall efficiency is ~90%

Better in the central region, but still not bad up to eta ~3.0!

Efficiency ~75% @ 2<|eta|<3... where there's ~15% of ZH events, so should get:

an efficiency increase of ~11%!

In total can get Z eff. in ZH of ~80% instead of ~60%!

Andy Haas

2004-07-07T15:59:13