Transcript Determination of Yukawa Couplings at LHC and ILC

Higgs Boson Searches with ATLAS
Based on Data Collected in 2010
Markus Schumacher (Albert-Ludwigs-Universität Freiburg) bmb+f
on behalf of the ATLAS Collaboration
Rencontres de Moriond 2011 Electroweak Session
 Prologue
 Hgg
 HWW  lnln
 HZZllnn/llqq
 Htt in MSSM
 Amm at low mass
 Epilogue
Signal Rates and Limit Derivation Technique
 signal rates and their theoretical uncertainties (mf, mr, PDF and as) based on
„Handbook of LHC Higgs Cross Sections: 1. Inclusive Observables.“ arXiv:1101.0593 [hep-ph]
 frequentist limit derivation based on:
- profile likelihood method (nuisance parameters for systematic uncertainties)
- power constraint CLS+B (impose CLB >16%) i.e. if observed cross section limit
smaller than median expected – 1s, then quote median expected – 1s
- for comparison also CLS used at LEP and TEVATRON shown
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Higgs Boson Searches with ATLAS Based on 2010 Data
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The Challenge: Tiny Signal-to-Background Ratio
measurements of “EW“ backgrounds
multijet background:
estimation from data
and/or found to be negligible
W+,W-
Z/g*
top pairs
< 1 detectable Higgs boson
per 1012 collisions
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H 2 Photons with 37.6 pb-1
 2 isolated photons with pT > 40 / 25 GeV
 main backgrounds:
reducible: g-jet and jet-jet
q
g
 discriminate
g
g
g photon from jet
q
p0
irreducible: gg
 excellent
g reconstruction of Mgg
g
q
q
MC event
 check of backgrounds from „sideband“
B
D
loose g ID
A
C
tight g ID
isolated
comparison of MC prediction
and estimation from data
non isolated
iterative „A=B*C/D“ method
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H 2 Photons: Exclusion Limit
 signal mass shape described by
Crystal Ball + Gaussian
FWHM
= 4.4 GeV
MH=120 GeV
 background extraction via exponential
shape with two nuisance parameters
signal systematic uncertainties
Source
Uncertainty (%)
Luminosity
±3.4
Cross section
+20/-15
Photon identification
±11
Photon Isolation
±10
Trigger
+1.1/-3.7
Energy resolution
±13 on sM
 exclusion limit
comparable to Tevatron 2010 result
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H WWlnln with 35 pb-1
 production via gluon fusion + VBF considered
 backgrounds: diboson qq,ggWW,ZZ,WZ
W+jets, Z+jets, tt, single top, ...
 preselection:
- 2 leptons (e,m), pT>20(15) GeV
- Mll >15, |MZ-Mll|>10GeV (ee,mm)
- MET>30 GeV
- Dfll <1.3 (1.8) for MH<170 (>=170GeV)
(see ATLAS-CONF-2011-005 for details)
 optimise sensitivity by
branching in 0, 1 and 2 jets
and additional topological cuts
 uncertainty on signal events
0 / 1 / 2 jets: 10 / 6 / 35 %
evaluated by variation of
mf, mr, PDF, as
in NNLO+NNLL calculation
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HWWlnln: MT Distributions and Background Estimate
 final cut on transverse mass 0.75 MH<
0 jet
1 jet
2jet
Data
3
1
0
BG
1.7±0.3
1.3±0.5
0.02±0.03
Higgs
1.3±0.4
0.6±0.2
0.06±0.03
<MH
0 jets
1jet
 estimation of all major backgrounds from control regions in data
 sys. uncertainties on a and b
- experimental:
E scales and resolutions,
tagging efficiencies, ...
- theo. uncertainties
renormalisation scales, ..
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Higgs Boson Searches with ATLAS Based on 2010 Data
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HWWlnln: Exclusion Limits
 absolute limit on cross section
 limit w.r.t. SM prediction
2010
cross section limits:
54 (11,71) pb at MH=120 (160,200) GeV
sensitivity dominated by gluon fusion
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1.2 x SM cross section sSM
excluded at MH = 160 GeV
Higgs Boson Searches with ATLAS Based on 2010 Data
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H  ZZ llqq and llnn with 35 pb-1
 improves sensitivity for large MH where HZZ4 leptons rates gets small
 2 leptons (e,m) with pT>20GeV 76 GeV < Mll <106 GeV
 llqq: final discriminant Mlljj
MET<50 GeV , 70< Mjj<105 GeV, MH>360 GeV: pT(jets)>50GeV, Df ll ,Df jj < p/2
 llnn: final discriminant : transverse mass
b-jet veto, MET>66/82GeV,Df ll <2.64/2.25forMH</≥260GeV
 background estimation: ZZ/WW/WZ from MC (uncertainty 15%)
other backgrounds confirmed from sideband in Mjj and Mll and reversed cuts
s(Z) = 5% s(tt) = 25% s(W) = 50% s(multijet) = 50%
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Higgs Boson Searches with ATLAS Based on 2010 Data
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H  ZZ llqq and llnn: Exclusion Limits
 combination of both channels:
expected 6.5 to 24.5 x sSM
observed 3.5 to 39 x sSM
signal uncertainties:
theoretical :
17%
experimental : 20 to 25%
+ shape uncertainties
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Higgs Boson Searches with ATLAS Based on 2010 Data
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MSSM: H  tt  e/m + thad with 36 pb-1
 MSSM Higgs sector: 5 bosons h,H,A,H+,Hgoverned by 2 parameters MA, tanb at Born level
 signal: b(b)H and gluon fusion production
 backgrounds: - irreducible: Ztt, ttlthad X
- reducible: W+jets,tt,Zll, ...
 selection
- e (pT>20 GeV) or m (pT>15 GeV) + 1 thad (pT>20 GeV)
- MET > 20 GeV
-
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< 30 GeV
 visible mass reconstruction
 tau and lepton ID, MET
 event yields: data versus MC
Data
Total
BG
Ztt
W+jets
206
207±6
101 ±4
67± 3
h/H/A
tanb=40
MA=120GeV
52 ±1
but use of data-driven techniques to
predict spectrum for Mtt (visible)
Higgs Boson Searches with ATLAS Based on 2010 Data
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H  tt  e/m thad: Background Estimation
 Ztt from embedding: select Zmm in
data and replace m by t from simulation
 multijet and W+jets:
same sign (SS) mass spectrum
and opposite sign OS/SS ratios
from control regions
NOS(estimated)
NOS-SSW+jets (data/MC)
195 ± 33
31 ± 5
NOS-SSZ+jets (MC)
105 ± 32
NOS-SS other (MC)
24 ± 5
Nss
36 ± 6
(data)
Data
206
MC w/o multijet
207 ± 6
 dominant systematic uncertainties:
exp. : jet and tau energy scale (5%) signal +17/-14%
Ztt +32/-21%
theo: cross section
signal 10 to 20%
Ztt
4%
total uncertainty on signal efficiency: 24.2% (15.4%) for MHiggs= 120 (200) GeV
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Higgs Boson Searches with ATLAS Based on 2010 Data
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H  tt  e/m thad: Mass Spectrum and Exclusion Limit
 visible mass pectrum after all cuts
background prediction from
data-driven methods
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 limit in „MA versus tanb“ plane
in „mh max“ scenario (m>0)
4 flavour calculation used
as yields more conservative
limit than 5 flavour calculation
Higgs Boson Searches with ATLAS Based on 2010 Data
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A  mm at low mass with 35 pb-1
 search for low mass scalar A in range [6,9] and [11,12] GeV e.g. inspired by NMSSM
 two muons with pT>4 GeV (blue line)
 likelihood ratio selection (black markers)
with PDFs derived from data itself
signal : 9 to 11 GeV (Us and A agree)
background: 4.5 to 5.5, 12.5 to 14.5 GeV
 PDFs for likelihood ratio inputs: primary vertex c2/ndf and calo. isolation of muons
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Higgs Boson Searches with ATLAS Based on 2010 Data
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A  mm: Exclusion Limit
 limit setting: normalisations floating
- signal A: double gaussian with width and
fractions of 2 gaussian related to U
- U(1/2/3s) double gaussian:
widths and fractions free parameters,
masses fixed to PDG values
- continuum BG: 4th order Chebyshev
polynom with all parameters free
 signal efficiency uncertainties
Source
MA=6(11.5)GeV
Luminosity
3.4 (3.4)%
PYTHIA vs MC@NLO
67 (20)%
Muon Efficiency
14 (15)%
Dimuon Trigger
13 (12)%
Likelihood Method
3 (3) %
Total
70(28)%
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 limit on s(ggA)x BR(Amm)
Higgs Boson Searches with ATLAS Based on 2010 Data
Moriond EW, March 2011
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Conclusions and Prospects
 ATLAS detector performs very well, but no hint for Higgs @ LHC yet
 so far: inclusive and simple cut-based selections
 dominant background contributions determined with data-driven techniques
 sensitivity in H2 photons comparable to Tevatron 2010 findings
 close to SM sensitivity in HWWlnln (1.2 x SM) already with 35 pb-1
 HZZllnn/llqq best limits in high mass regime
 h/H/Att in MSSM supersedes published Tevatron 2010 results
projection of
sensitivity
with <4fb-1 we could exclude down to LEP limit, but hopefully we will not do so!
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Higgs Boson Searches with ATLAS Based on 2010 Data
Moriond EW, March 2011
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Documentation
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/
 H  2 photons
ATLAS-CONF-2011-025
 HWWlnln
ATLAS-CONF-2011-005
 HZZllnn/llqq
ATLAS-CONF-2011-026
 Htt
ATLAS-CONF-2011-024
 Amm
ATLAS-CONF-2011-020
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Higgs Boson Searches with ATLAS Based on 2010 Data
Moriond EW, March 2011
Backup
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Higgs Boson Searches with ATLAS Based on 2010 Data
Moriond EW, March 2011
H 2 photons: Comparison of Limits
 power constraint CLS+B limit
 CLS limit
 exclusion limits in numbers:
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Higgs Boson Searches with ATLAS Based on 2010 Data
Moriond EW, March 2011
H WWlnln: Details of Limits
 power constraint CLS+B limit
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Higgs Boson Searches with ATLAS Based on 2010 Data
Moriond EW, March 2011
H WWlnln: Analysis Details
 signal production via gluon fusion and VBF considered
 backgrounds: diboson qqbar,ggWW,ZZ,WZ, W+jets, Z+jets, ttbar, single top
 preselection:
- 2 pleptons (e,m), pt >20(15) GeV
- MET>30 GeV: em (ee,mm)
 final cut on transverse mass
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- Mll >15, |MZ-Mll|>10GeV (ee,mm)
- Dfll <1.3 (1.8) MH<170 (>=170GeV)
0.75 MH<
Higgs Boson Searches with ATLAS Based on 2010 Data
<MH
Moriond EW, March 2011
HWWlnln: Branching in Jet Multiplicities
 branch analysis in 0, 1 and 2 jets top optimise sensitivity
- jets reconstructed with anti-kt R=0.4 algorithm, pt>25 GeV, |h|<4.5
- associated to primary vertex PV by requiring fraction of momentum from
tracks from PV to total jet energy > 0.75
 uncertainty on fraction of signal events in multiplicity bins
0 jet: 10%
1 jet: 6% 2 jet:35%
evaluated by variation of renorm., factor. scales, PDFs, as in HNNLO
 additional cuts for each jet multiplcity branch:
0jet:
<30 GeV
1jet: veto on b-jet ,
2 jet: veto on b-jet,
<30GeV, Ztt veto,
<30 GeV, Ztt veto,
<80GeV
plus VBF cuts: mjj>500GeV, Dhjj>3.8, no 3rd central jet
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Higgs Boson Searches with ATLAS Based on 2010 Data
Moriond EW, March 2011
HWWlnln : Section Results
H+0 jets:
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H+1jet:
Higgs Boson Searches with ATLAS Based on 2010 Data
H+2 jets:
Moriond EW, March 2011
BG Estimate e.g.: ttbar and WW BG in H+1 Jet Analysis
 ttbar control region: replace b-veto by b-tag and drop cuts on mll, MT, Dfll
 att + systematic uncertainty
 WW control region: mll >100 GeV and drop cuts on MT, Dfll
aww + systematic uncertainty
combining both tables  btt (pollution in WW control region)
 similar methods for all backgrounds in all jet mutiplicity bins
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Higgs Boson Searches with ATLAS Based on 2010 Data
Moriond EW, March 2011
HWWlnln: Systematic Uncertainties
Background extraction
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Experimental uncertainties
Higgs Boson Searches with ATLAS Based on 2010 Data
Moriond EW, March 2011
MSSM: H  tt  e/m + hadronic tau decay thad
 signal: b(b)H and gluon fusion production  backgrounds:
- irreducible: Ztt, ttlthad X
mass reconstruction
- reducible: W+jets,tt,Zll, ...
tau and lepton ID,MET
signature: e or m , t , MET from 3 n
had
 e (pT>20 GeV) or m (pT>15 GeV) and 1 thad (pT>20 GeV)
 MET > 20 GeV
 Transverse mass
< 30 GeV
observed data and MC prediction
after MET cut
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process
e channel
m channel
data
74
132
total BG
70+/- 3
137+-4
Ztt
30+/-2
81+-3
Zll
10 +/-1
11+-1
W+jets
26 +/-2
41+-2
Top
3.3 +/-0.2
4.6+-0.2
h/H/A tanb=40
MA=120 GeV
17.9/-0.6
35.4+-0.8
Higgs Boson Searches with ATLAS Based on 2010 Data
Moriond EW, March 2011
H  tt  e/m thad: Background Estimation
 estimation of background from same sign lepton + had. tau events
 assumptions verified in simulated MC events:
shape of visible mass distribution is the same for OS and SS events
ratio r between OS and SS events is the same in signal and control region
ratiofor multijet production rQCD= 1
 rQCD from control region CR with MET<15 GeV: 1.16+/- 0.04+/-0.09
 kW+jets =r W+jets-1 from CR with MT>50GeV:
1.43+/- 0.15
 shape of W+jets and shape + normalisation of other backgrounds from MC
NOS(all)
195 +/- 33
k W+jets NSSW+jets
31+/- 5
 MC prediction w/o QCD: 207 ± 6
 QCD estimate from data: 12 ±
NOS-SSZ+jets
105 +/- 32
NOS-SS other
24 +/- 5
 Daten driven estimate:
195 ± 33
Nss
36 +/- 6
 Data:
206
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Higgs Boson Searches with ATLAS Based on 2010 Data
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Moriond EW, March 2011
H  tt  e/m thad: Background Estimation
 good agreement between background prediction from data and data in signal region
 details of
systematic
uncertainties
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Higgs Boson Searches with ATLAS Based on 2010 Data
Moriond EW, March 2011
H  tt  e/m thad: Verification of Ztt Description
 use jjZmm to model jjZttX as they have same topology
 Zmm: signal free and high purity control sample selectable
 apart from m and tX energy deposits same detector response
(including pileup, underlying event, noise, …)
 Methodology:
1) select Zmm event in collision data
2) use 4-momenta of m as input for t decays
3) simulate ZttXY decay
4) replace cones around m in data event
by cones in simulated Ztt decay
on calorimeter cell level
 „embedding“
5) re-reconstruct merged hybrid event
6) apply standard selection
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Higgs Boson Searches with ATLAS Based on 2010 Data
Moriond EW, March 2011
H  tt  e/m thad: Cross-Sections
 MHMAX scenario:
 5 flavour versus
4 flavour calculation
 comparison of
production cross section from
gluon fusion and
in association with b-quarks
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Higgs Boson Searches with ATLAS Based on 2010 Data
Moriond EW, March 2011
H  ZZ  llqq: Analysis Details
 event yields
including
systematic
uncertainties
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Higgs Boson Searches with ATLAS Based on 2010 Data
Moriond EW, March 2011
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H  ZZ llqq: Background Estimate
 Z+jets: control region from Mjj sideband 40 to 70 and 105 to 150 GeV
 tt background: control region from Mll sideband 60 to 76 and 106 to 160 GeV
+ reversed MET>50GeV cut
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Higgs Boson Searches with ATLAS Based on 2010 Data
Moriond EW, March 2011
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H  ZZ  llnn : Analysis Details
 event yields
including
systematic
uncertainties
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Higgs Boson Searches with ATLAS Based on 2010 Data
Moriond EW, March 2011
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H  ZZ llnn: Background Estimate
 W+jets ++ tt : control region from Mll sideband 60 to 76 and 106 to 160 GeV
tt:
MET>20 GeV,
one b-tagged jet
W+jets:
MET>36 GeV,
no b-tagged jet
 tt b-tagged control region:
data 17 events
 W+jets b-vetoed control region: data 27 events
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MC prediction 18.6 ± 0.5 events
MC prediction 25.8 ± 2.0 events
Higgs Boson Searches with ATLAS Based on 2010 Data
Moriond EW, March 2011
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H  ZZ lljj and llnn : Details on Limit
 limits in numbers
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 combined limit
Higgs Boson Searches with ATLAS Based on 2010 Data
Moriond EW, March 2011
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H  ZZ lljj/llnn: Comparison of PCLS+B and CLS
 power constraint CLS+B limit
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 CLS limit
Higgs Boson Searches with ATLAS Based on 2010 Data
Moriond EW, March 2011
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H  ZZ llqq: Comparison of PCLS+B and CLS
 power constraint CLS+B limit
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 CLS limit
Higgs Boson Searches with ATLAS Based on 2010 Data
Moriond EW, March 2011
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H  ZZ  llnn: Comparison of PCLS+B and CLS
 power constraint CLS+B limit
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 CLS limit
Higgs Boson Searches with ATLAS Based on 2010 Data
Moriond EW, March 2011
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