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LCWS14, Belgrade, 06-10 October 2014. M. Pandurović, H→WW at 350 GeV and 1.4 TeV CLIC
Measurement of H→WW* in HZ at 350 GeV and WW fusion at 1.4 TeV CLIC
Mark Thomson Mila Pandurović
on behalf of the CLICdp collaboration
M. Pandurović, H→WW at 350 GeV and 1.4 TeV CLIC LCWS14, Belgrade, 06-10 October 2014.
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Outline
Motivation for H→WW* decay in CLIC physics program
Analysis overview
Simulation and reconstruction
H→WW* at 350 GeV
H→WW* at 1.4 TeV
Conclusion
M. Pandurović, H→WW at 350 GeV and 1.4 TeV CLIC LCWS14, Belgrade, 06-10 October 2014.
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Introduction
BF (H→WW)~23% Considering only fully hadronic H→WW*→qqqq decays BF (H→WW→qqqq)~10% Full reconstruction of mH possible only in these fully hadronic decays
M. Pandurović, H→WW at 350 GeV and 1.4 TeV CLIC LCWS14, Belgrade, 06-10 October 2014.
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Parallels of studies
s-channel (central jets) t-channel (forward jets ) final states 4 jets + 2 leptons (Zll) 4 jets +missing energy
6 jets (Zqq)
H
HWW2
HZZ2 gg
H
HWW4g
From ZH: model independent measurement of absolute coupling of the Higgs to Z boson 0.8 %<
M. Pandurović, H→WW at 350 GeV and 1.4 TeV CLIC LCWS14, Belgrade, 06-10 October 2014.
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Backgrounds
M. Pandurović, H→WW at 350 GeV and 1.4 TeV CLIC LCWS14, Belgrade, 06-10 October 2014.
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Analysis strategy
Lepton Isolation
Fast Jet
Lcfi Vertexing
Preselection
MV selection
Results
HZ, Z→ll at 350GeV
Reduction of large cross-section background
2 jet hypothesis to apply btagging
BDT350 Likelihood based1.4TeV
TMinuit: fit to extract x-sec
S
BS
kT exclusive, selectedPFO’s Force events into: 4 or 6 jets
M. Pandurović, H→WW at 350 GeV and 1.4 TeV CLIC LCWS14, Belgrade, 06-10 October 2014.
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Simulation and reconstruction
Event generation with WHIZARD v.1.95 , ISR
Beam spectrum generated with GUINEAPIG
Hadronization with PYTHIA
- hadrons overlaid
Assuming mH=126 GeV
CLIC_ILD detector
Particle reconstruction and identification
PandoraPFA
M. Pandurović, H→WW at 350 GeV and 1.4 TeV CLIC LCWS14, Belgrade, 06-10 October 2014.
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H→WW* at 350 GeV
Vinca Institute of Nuclear sciences, University of Belgrade
Mila Pandurović
M. Pandurović, H→WW at 350 GeV and 1.4 TeV CLIC LCWS14, Belgrade, 06-10 October 2014.
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Signal signature
Signature: Semileptonic final state: 4 jets +2 leptons
Main background :qqll, qql, other Higgs decays
Hadronic final state: 6 jets Main background: qqqq, other Higgs decays
Signal evts: BF(H→WWqqqq)~10%
BF(Z→ll )~10% 1%~700 evts BF(Z→qq)~70% 7%~5000 evts
f
f
M. Pandurović, H→WW at 350 GeV and 1.4 TeV CLIC LCWS14, Belgrade, 06-10 October 2014.
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First step : Lepton isolation
Lepton identification: track energy >12 GeV energy contained in a cone around the track (cos <0.995) ECAL/HCAL depositions
Signal - reconstructed lepton pairs event: 85% electron pairs 84% muon pairs 3% false lepton pairs
Z→ee Z→µµ Z→qq
Etrack[GeV]
Econe[G
eV]
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Jet Matching Preselection
Grouping 4 jets to form W real
Grouping 6 jets to form W, Z and Higgs
114 jets + 2 leptons
6 jets final state
H
2
2Hijmn
Z2
2Zkl
W2
2Wij2 MMMMMM
|MM|min)dmin( Wijij
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Event selection BDT
1. other H decays, HZ, Z→ll 2. qqll 3. qql
1. other H decays, HZ, Z→qq 2. qqqq
126 jet FS4 jet FS
After preselection the most difficult backgrounds are used as an input to MV:
M. Pandurović, H→WW at 350 GeV and 1.4 TeV CLIC LCWS14, Belgrade, 06-10 October 2014.
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Reduction efficiencies
M. Pandurović, H→WW at 350 GeV and 1.4 TeV CLIC LCWS14, Belgrade, 06-10 October 2014.
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Outlook
The analysis is constructed
Refinement of the each analysis step:
Lepton isolation: optimize the isolated lepton identification using MC truth matching
Jet matching : refine the ’s of the H,W, Z distributions
Include backgrounds with 6 fermions in the final state
Preselection: redefine
Optimize set of BDT variables
M. Pandurović, H→WW at 350 GeV and 1.4 TeV CLIC LCWS14, Belgrade, 06-10 October 2014.
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H→WW* at 1.4 TeV
University of Cambridge
Mark Thomson
M. Pandurović, H→WW at 350 GeV and 1.4 TeV CLIC LCWS14, Belgrade, 06-10 October 2014.
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Signal signature
Signature: missing pt 4 jets mH (4 jets) , mW (2 jets)
Preselection targeted at main background: Hνν other Higgs decays, qqνν, qqqqν
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70 GeV < mH <150 GeV 40 GeV < mW < 95 GeV
mw* < 65 GeV
Force all samples into 2,3,4 jets Use the kT value from which jet
transitions from: - 2 to 3 jets -log10 (y23)< 2.75
- 3 to 4 jets -log10 (y34)< 3.5
Mass variables: mH mW ,mW*
Jet transitions
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Preselection
Evis & pt
125 GeV < Evis < 600 GeV
pT > 90 GeV P(b)1 , P(b)2 < 0.95
b tag
|MM|min)dmin( Wijij Jet Matching grouping 4 jets to form W real
M. Pandurović, H→WW at 350 GeV and 1.4 TeV CLIC LCWS14, Belgrade, 06-10 October 2014.
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Constructing likelihood for relevant event types:
signal H →WW* background H→bb, gg, qqνν, qqqqν
Using 2d distributions (correlations included)
mw vs. mH
y23 vs. y34
P(b)1 vs. P(b)2
Constructing relative likelihood distributions:
1,5)(i213423HWi ),b,b(P x )y,y(P)m,m(PL x
Relative likelihood selection
)L(qqqq )L(qq L(gg) L(bb) *)WW(L
*)WW(L*WW -- -
cut=0.35
M. Pandurović, H→WW at 350 GeV and 1.4 TeV CLIC LCWS14, Belgrade, 06-10 October 2014.
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Reduction efficiencies
S/B~1:1
M. Pandurović, H→WW at 350 GeV and 1.4 TeV CLIC LCWS14, Belgrade, 06-10 October 2014.
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Signal and background shapes not so different need to include constraints
Branching fractions of Higgs to bb,cc and gg are constrained to the values obtained from the independent measurements at 1.4 TeV
Constrained fit
b2
22
cc2
2cc
2
bb2
2bb
2
gg2
2gg
2
22 )b1()s1()s1()s1(~
%4.1
(assumed) % 1.0σ 0.3%,σ
2.9%,σ 1.8%,σ
bbb
ccbb
FIT
M. Pandurović, H→WW at 350 GeV and 1.4 TeV CLIC LCWS14, Belgrade, 06-10 October 2014.
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Conclusions
H →WW* decay plays an important role in the CLIC physics program, especially in the determination of the total Higgs decay width.
Analysis of the H → WW* decay from the HZ at 350 GeV constructed and being refined.
The (hee ) x BR(H →WW*) at the 1.4 TeV CLIC is determined with a statistical precision of 1.4 %.
-
M. Pandurović, H→WW at 350 GeV and 1.4 TeV CLIC LCWS14, Belgrade, 06-10 October 2014.
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END
Acknowledgements: P. Roloff, S. Redford, S. Lukic & HEP Group Vinca
