ttH, H->bb: Update

UK Atlas Higgs Meeting - RHUL - 22 April 2005 1

ttH, H->bb: Update

Janice DrohanUniversity College London

Overview:Atlfast SamplesTop reconstruction: Χ2 vs Δ2


ttH, H->bb: Update Generation Status:

Signal: Pythia vs Herwig (Jimmy) Very good agreement, slightly more jets in events

Problems: Producing large numbers of mc@nlo events.

Still to do: Need to produce a ttjj (light jets only) sample

Cammin produced this by filtering at Atlfast level

Sample Generator # Atlfast AOD Events Restricted decay of tops

ttH 120GeVPythia 300,000 Yes

Jimmy 55,000 Yes

ttjjPythia 22M No

mc@nlo 720,000 No

qq->ttbb AcerMC 400,000 No

gg->ttbb AcerMC 1.8M No


Top Reconstruction

TDR Method: Minimises: Δ2=(mlvb-mt)2+(mjjb-mt)2

Correct Jets assigned to Higgs ~25% cases Started looking at 2nd lowest Δ2 value:

Produces correct Higgs in a similar number of cases

MH (MeV)


Top Reconstruction

MH (MeV)


Trying to use instead of Δ2:

Using errors from within Atlfast Code for Jet energies and electron energy:

Jet: e: eta<1.4

Don’t yet have muon energy error S. Dean writing helper function to do this.

03.05.0

EE

Top Reconstruction

2

2

2

2

2

22 )()()(

jj

Wjj

lvb

tlvb

jjb

tjjb mmmmmm

007.012.0245.0

EpE T


Top Reconstruction

Errors looking reasonable:

Plans: Look into performance of χ2

Assigning of b-jets to Higgs in case of 3 left 138 events out of 2155, 60 wrong combinations

when choosing jets with highest pT

ANN for signal/background separation

mjjb σmjjb mlvb σmlvb mjj σmjj

152.9 10.5 270.2 12.5 105.1 11.4

307.8 17.1 138.5 24.3 65.4 33.5

ttH, H->bb: Update

Documents

Transcript of ttH, H->bb: Update