h 4 m in the low mass region e meoni l larotonda m antonelli f cerutti
Download
Skip this Video
Download Presentation
H -> 4 m in the low mass region E.Meoni, L.Larotonda, M.Antonelli, F.Cerutti

Loading in 2 Seconds...

play fullscreen
1 / 18

H -> 4 m in the low mass region E.Meoni, L.Larotonda, M.Antonelli, F.Cerutti - PowerPoint PPT Presentation


  • 106 Views
  • Uploaded on

H -> 4 m in the low mass region E.Meoni, L.Larotonda, M.Antonelli, F.Cerutti. Introduction ATLFAST++ and MOORE/MuID performance Irreducible background rejection Reducible bkg. Rejection Status and prospects. Introduction. Study started more then 1 year ago with twofold goals:

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' H -> 4 m in the low mass region E.Meoni, L.Larotonda, M.Antonelli, F.Cerutti' - fayola


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
h 4 m in the low mass region e meoni l larotonda m antonelli f cerutti
H -> 4 m in the low mass regionE.Meoni, L.Larotonda, M.Antonelli, F.Cerutti
  • Introduction
  • ATLFAST++ and MOORE/MuID performance
  • Irreducible background rejection
  • Reducible bkg. Rejection
  • Status and prospects
introduction
Introduction
  • Study started more then 1 year ago with twofold goals:
    • Validate ATLFAST++ and ATHENA Moore/MuID
    • Improve analysis w.r.t. TDR by using multivariate techniques against irreducible (ZZ->4m) and reducible (tt and Zbb) backgrounds
  • Started with ATHENA release 6.0.3
  • Mass region studied: MH[130-180] GeV (low mass is the most challenging because of the off-shell Z and higher bkg)
  • Here results showed for MH=130 GeV
introduction1
Introduction
  • Samples produced with PYTHIA 6.2 with the exception of Zbb (ACERMC ME)
  • Filter: 4 m with Pt>4 GeV and |h|<2.7
introduction pt and h spectra
Introduction: Pt and h spectra

Pt(GeV)

h

ATLFAST++, MH=130 GeV

introduction analyses chain
Introduction: analyses chain

COMMON PRESELECTION

4 muons, null total charge :

2 with pT > 20 GeV and | | < 2.5

2 with pT > 7 GeV and | | < 2.5

Analysis with

Multivariate methods

TDR analysis

Couples µ+ µ- with invariant mass :

M12= Mz ± 15 GeV M34> 20 GeV

( mH= 130GeV )

M12= Mz ± 10 GeV M34>30 GeV

( mH= 150GeV )

M12=Mz ± 6 GeV M34>60 GeV

( mH= 180GeV )

Angular cut

likelihood/NN (with angular variables and M12 & M34) cuts

Lepton isolation cut

likelihood/NN (with isolation variables) cut

Mass window cut (mH  2 )

to compute significance

Lepton isolation cuts

(single variable cuts)

Mass window cut (mH  2 )

to compute significance

introduction software codes
Introduction: software codes
  • ATLFAST++ (object oriented version of ALTAS fast simulation implemented in ATHENA framework)
  • ATHENA: MOORE/MuID with muon spectrometer in standalone and combined
    • started with version 6.0.3 many bugs found
    • latest results with 7.0.2
  • First step check of general performance
    • Efficiency
    • Pt resolution
    • MH resolution
selection efficiency
Selection efficiency
  • Acceptance after kinematic cuts (4m and M12 and M34 cuts):
    • ATLFAST++: 33.0%
    • TDR: 33.5%
    • MOORE/MuID combined 6.0.3: 9%
    • Inefficiency concentrated in low Pt region

Muid Combined

Athena6.0.3

selection efficiency1
Selection efficiency
  • Improved with version 7.0.2
    • MOORE/MuID combined 7.0.2: 23%
    • Inefficiency concentrated eta~2 region

Muid Combined

Athena7.0.2

mass resolution
Mass resolution
  • Performance muon spectrometer:
    • TDR: 2.7 GeV
    • MOORE 7.0.2: 3.0 GeV
  • Combined (including Z mass constraint):
    • TDR: 1.4 GeV
    • ATLFAST++: 1.5 GeV
    • MOORE/MUID comb 7.0.2: 1.7 GeV
irreducible bkg zz 4 m
Irreducible bkg.: ZZ->4m
  • Multivariate analyses: in addition to MH, M12 and M34 there are other 9 independent kinematic variables (12 in total)
  • Try to select variable sensitive to the spin and parity of the signal
  • Combine all variables with multivariate techniques: likelihood and NN
  • Likelihood function (and neural network)
  • with 11 variables:
  • Angle of the decay planes of the two Z in Higgs rest frame
  • (see ATL-COM-PHYS-2003-001,Buszello et al.)
  • Angle between m- in Z rest frame and Z boost in Higgs rest
  • frame (both for on-shell Z and off-shell Z)
  • (see ATL-COM-PHYS-2003-001,Buszello et al.)
  • Angle between Z (both on-shell and off-shell) direction in
  • Higgs rest frame and the Higgs boost
  • Angle between the two m+ in Higgs rest frame
  • Angle between the two m- in Higgs rest frame
  • Angle between the two m of Z (both on-shell and off-shell)
  • Invariant masses of the two m+ m- couples (M12 and M34)
slide11

Angle between m- in the Z

rest frame and Z boost in Higgs rest frame

Angle between the decay

planes of the two Z

in Higgs rest frame

Angle between on-shell Z direction in Higgs rest frame and Higgs boost

H4

H4

H4

ATLFAST

ATLFAST

ATLFAST

ZZ4

ZZ4

ZZ4

ATLFAST

ATLFAST

ATLFAST

H4

H4

H4

FULL REC.

FULL REC.

FULL REC.

ZZ4

ZZ4

ZZ4

FULL REC.

FULL REC.

FULL REC.

results with fast simulation
Results with Fast simulation

Improvement: mainly coming from M12 and M34 optimization

angles relevant only at higher MH

reducible background
Reducible background
  • 2 out of 4 muons not isolated in tt and Zbb background
  • Likelihood (and neural network) with 6 variables:
  • the 2 largest normalized impact parameters(IP) in trasverse plane of the 4 IP
  • the 2 largest pT reconstructed inside a cone of R=0.2 around the 4 µ tracks
  • the 2 largest total transverse energy depositions in calorimeters (EM+HC) in a cone of R=0.2 around the 4µ tracks

We have added in CBNT ntuple block of Moore/Muid the energy deposition in cones of different radii around the “muon track”

“muon track” defined in 4 ways: moore trk, muid statandalone trk, muid combined trk, iPat trk

Best results with: energy of radius R=0.2 around “iPat” trk

slide14

Largest energy loss

Around iPat track

Signal

ttbar

Zbb

Signal

ttbar

Zbb

Largest IP

Signal

ttbar

Zbb

Largest pT

After pT &  cuts

and m12 & m34 cuts

slide15

Neural

Network

Likelihood

After pT &  cuts

and m12 & m34 cuts

mass plots
Mass plots
  • Preselection (as in TDR) : 4 m , total charge =0, pT &  cuts
  • Angular cut: likelihood- 11 variables
  • Isolation cut : likelihood– 6 variables

After preselection (4m,Qtot=0,pT& h cuts)

Signal

ZZ 4m

ZZ 2m2t

ttbar

Zbb

All channels

Signal

ZZ 4m

ZZ 2m2t

ttbar

Zbb

All channels

After overall analysis (preselection+ ang. lik cut+isol lik cut)

conclusions and prospects
Conclusions and Prospects
  • ATLFAST++ and MOORE/MuID (7.0.2) comb. performance studied on H->4m (low mass): worse performance then TDR, still low efficiency at |h|~2 to be understood

Prospects

  • Add Noise and pileup, relevant for lepton isolation
  • Control samples to study lepton isolation variables on data: tt-> WWbb: W->l W->jj select b jet with Mbjj=Mtop (b forced to leptonic decay)
  • Wait for bug fixes ?
  • Produce documentation: ATLAS note and SN
  • Participation to DC2 validation very important:
    • New digitization
    • New simulation GEANT4
    • New output data format
    • New reconstruction release
ad