Motivation

  • No Higgs left behind!
  • A Standard Model (SM) Higgs doesn't couple to neutrinos, the "invisible" particles.
    • neutrinos escape detection as they are stable, neutral and interact only via weak force.
    • nature doesn't make right-handed neutrinos.
  • A Higgs decay is therefore almost always partly or fully visible.
    • only exception is .
  • Many Beyond-Standard-Model (BSM) models are shipped with invisible particles:
    • neutralino, gravitino (SUSY models), Kaluza-Klein neutrino (Extra Dimension models), Majoron, 4th generation neutrinos, ...
    • some of them are dark matter candidates.
    • e.g. in the R parity-conserved SUSY models, the SM-like Higgs can decay into two neutralinos, provided the neutralino mass is < 0.5 .
  • Define .
    • in SM, = 0.
    • in BSM, can be > 0 if the Higgs couples to the invisibles. - all the SM Higgs branching fractions are rescaled by a constant term: - - effectively, the upper exclusion limit of the Higgs production rate can be reinterpreted as the lower limit of given the SM Higgs production rate. - since detectors measure
  • LEP had excluded invisibly decaying higgs with GeV

Datasets

2011 7 TeV

  • Signal MC need to be generated
    • Full Sim: best if centrally produced but probably very difficult to request
    • Fast Sim: fast and used in many BSM analyses.
      • however, b-tagging can be inaccurate
  • Background MC are ready

Dataset
/ZZToAnything_Ptmin200_TuneZ2_7TeV-pythia6-tauola/
/WZToAnything_Ptmin200_TuneZ2_7TeV-pythia6-tauola/
/WWToAnything_Ptmin200_TuneZ2_7TeV-pythia6-tauola/
? /ZZ_TuneZ2_7TeV_pythia6_tauola/
? /WZ_TuneZ2_7TeV_pythia6_tauola/
? /WW_TuneZ2_7TeV_pythia6_tauola/
/ZJetsToNuNu_Pt-100_7TeV-herwigpp/
/WJetsToLNu_Pt-100_7TeV-herwigpp/
? /WJetsToLNu_TuneZ2_7TeV-madgraph-tauola/
/TTJets_TuneZ2_7TeV-madgraph-tauola/
/T_TuneZ2_s-channel_7TeV-powheg-tauola/
/Tbar_TuneZ2_s-channel_7TeV-powheg-tauola/
/T_TuneZ2_t-channel_7TeV-powheg-tauola/
/Tbar_TuneZ2_t-channel_7TeV-powheg-tauola/
/T_TuneZ2_tW-channel-DR_7TeV-powheg-tauola/
/Tbar_TuneZ2_tW-channel-DR_7TeV-powheg-tauola/
/QCD_Pt-30to50_TuneZ2_7TeV_pythia6/
/QCD_Pt-50to80_TuneZ2_7TeV_pythia6/
/QCD_Pt-80to120_TuneZ2_7TeV_pythia6/
/QCD_Pt-120to170_TuneZ2_7TeV_pythia6/
/QCD_Pt-170to300_TuneZ2_7TeV_pythia6/
/QCD_Pt-300to470_TuneZ2_7TeV_pythia6/
/QCD_Pt-470to600_TuneZ2_7TeV_pythia6/
/QCD_Pt-600to800_TuneZ2_7TeV_pythia6/
? /ZH_ZToNuNu_HToBB_M-120_7TeV-powheg-herwigpp/
  • Data

Dataset
/METBTag/Run2011A-May10ReReco-v1/
/MET/Run2011A-PromptReco-v4/
/MET/Run2011A-05Aug2011-v1/
/MET/Run2011A-PromptReco-v6/
/MET/Run2011B-PromptReco-v1/

2012 8 TeV

  • Signal MC need to be generated
    • Full Sim: best if centrally produced but probably very difficult to request
    • Fast Sim: fast and used in many BSM analyses.
      • however, b-tagging can be inaccurate
  • Background MC are ready

Dataset
To be taken from AN-2012/181
  • Data

Dataset
/MET/Run2012A-PromptReco-v1/
/MET/Run2012B-PromptReco-v1/

Search strategy

  • Associated production of Higgs with a provides a way to detect the otherwise invisible decay.
    • Associated production with a suffers from huge single production.

zbbhinv_diagram.png

  • Interesting at low mass region < 140 GeV.
    • before turns on.
    • narrow width approximation is valid.
  • The signature is a recoiling against transverse missing energy (MET):
    • can be reconstructed from the pair.
    • opening angle between and MET in the transverse plane should be .
      • assuming no ratiation, perfect detector coverage and energy measurements etc.
    • should be equal to MET.
  • 1st pass: use existing Step 1 PAT-tuples, optimize selection in Step 2 ntuples.
    • do simple cut-based analysis and MVA BDT
  • 2nd pass: improve Step 1 PAT-tuples, reoptimize selection in Step 2 ntuples.
    • do simple cut-based analysis and shape-based MVA BDT

Triggers

  • Use the same triggers as used by Z(nunu)H(bb) search
  • Can keep the same MET threshold at 8E33?

2011 7 TeV

Dataset Run range
HLT_PFMHT150 160404 - 180252
HLT_CentralJet80_MET80 160404 - 165000
HLT_DiCentralJet20_MET80 165000 - 175900
HLT_DiCentralJet20_MET100_HBHENoiseFiltered 175900 - 180252

2012 8 TeV

Dataset Run range
HLT_PFMET150 190456 -
HLT_DiCentralJet20_MET80 190456 - 193752
HLT_DiCentralJet20_MET100_HBHENoiseFiltered 193752 -

Object definitions

Jets

  • anti-kT PF jets with R = 0.5 (ak5PF)
  • Apply charged hadron subtraction (PFnoPU)
  • (2nd pass) possible use of fat jets, jet substructure?

MET

  • Type-1 corrected PF MET (Type1METPF)
  • (2nd pass) possible use of Type-0 correction?
  • (2nd pass) possible use of MVA MET?

Leptons, Photons

  • As used by Z(nunu)H(bb) search

b-tagging

  • Combined Secondary Vertex (CSV)
  • (2nd pass) possible use of CSV with Inclusive Vertex Finder (CSV_IVF) designed by Andrea and co?

Pile-up reweighting for MC

  • As used by Z(nunu)H(bb) search

Signal selection

Z reconstruction

  • Select jets with > 20 GeV, < 2.5
    • select dijet pairs with > 150 GeV (tentatively)
      • select the dijet pair with highest sum of CSV as the candidate
  • Apply -tagging
    • CSV high > CSVT, CSV low > CSVL
  • Apply mass cut
    • < 30 GeV (tentatively)
  • (2nd pass) Apply -jet energy BDT regression
    • or apply jet energy fit using mass constraint

Higgs reconstruction

Event reconstruction

  • Good primary vertex selection
  • Isolated lepton veto
  • > 2.9
  • min > 0.5
  • looking for ideas...

Background estimation

Irreducible

    • difference #1: difference in the invisibly decaying boson mass
      • transverse mass () retains memory of the mass
      • and razor variable might help?
    • difference #2: ZZ is a t-channel diagram, Zh is a s-channel
      • ZZ is more forward
    • difference #3: difference in spin
      • angular distribution of the jets in the dijet pair
  • SM
    • difference #1: difference in the dijet mass
    • difference #2: difference in spin

Z resonance

  • if is too soft or falls outside detector acceptance
    • difference #1: isolated lepton
    • difference #2: mediated by a virtual W
    • difference #3: difference in spin
  • with and a badly mismeasured jet
    • difference #1: MET tends to align with a jet
    • difference #2: MET is not 'significant'

Heavy flavor

  • , with
    • difference #1: the dijet mass is not within Z resonance
  • , with
    • difference #1: isolated lepton
    • difference #2: the dijet mass is not within Z resonance
  • , with semileptonic top decay
    • difference #1: more outgoing jets
    • difference #2: isolated leptons
    • difference #3: the dijet mass is not within Z resonance
  • single
    • difference #1: the dijet mass is not within Z resonance
    • more?
  • Heavy flavor QCD with a badly mismeasured jet
    • difference #1: MET tends to align with a jet
    • difference #2: MET is not 'significant'
    • difference #3: the dijet mass is not within Z resonance

Other

  • Due to -jet mistagging, other processes with 2 jets and missing energy can also enter:
    • QCD with badly mismeasured jets
  • Ignore possible BSM processes for now...

Results

  • Figures of merit: , ,

Interpretations

  • Exclusion Confidence limits (CLs)

Systematics

  • Theoretical cross section
  • MC spectrum
  • MC statistics
  • Fast Sim signal MC
  • Luminosity
  • Trigger efficiency
  • Lepton efficiency
  • b-tagging efficiency
  • Jet energy scale
  • Jet energy resolution
  • MET

Grocery list

  • Fast Sim signal generation
  • Step 1 signal production
  • Step 2 modifications and production
  • Optimization of signal selection
  • Development of background estimation techniques
  • Data/MC comparison
  • Result interpretation
  • Result interpretation in specific BSM models, dark matter constraint
  • Extension to
Error during latex2img:
ERROR: problems during latex
INPUT:
\documentclass[fleqn,12pt]{article}
\usepackage{amsmath}
\usepackage[normal]{xcolor}
\setlength{\mathindent}{0cm}
\definecolor{teal}{rgb}{0,0.5,0.5}
\definecolor{navy}{rgb}{0,0,0.5}
\definecolor{aqua}{rgb}{0,1,1}
\definecolor{lime}{rgb}{0,1,0}
\definecolor{maroon}{rgb}{0.5,0,0}
\definecolor{silver}{gray}{0.75}
\usepackage{latexsym}
\begin{document}
\pagestyle{empty}
\pagecolor{white}
{
\color{black}
\begin{math}\displaystyle \Gamma_{h_{\rm inv}} = \Gamma(h \to {\rm invisibles})\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle \geq\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle W \to \ell \nu\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle Z \to b \bar b\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle \Gamma'_(h \to xx) = \Gamma(h \to xx) \cdot \frac{\Gamma_{h_{\rm SM}}}{\Gamma_{h_{\rm SM}} + \Gamma_{h_{\rm inv}}}\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle \Delta\phi({\rm jet},h_{\rm cand})\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle t \bar t + j\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle \Delta\phi(Z_{\rm cand},h_{\rm cand})\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle \mathcal{L} ({\rm fb}^{-1})\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle Z \to \nu \bar \nu\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle W + b \bar b\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle Z~p_{\rm T}\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle |M_{jj} - M_Z|\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle Z\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle W + c \bar c\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle ZW \to b \bar{b} \ell \nu\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle W\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle |\eta|\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle W^*\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle h \to ZZ \to 4 \nu\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle \sigma_{h_{\rm SM}} \cdot \operatorname{BR}(h \to xx) \cdot \mathcal{L}\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle h\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle Z + c \bar c\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle Z + j\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle \alpha_{\rm T}\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle b \bar b\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle t\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle m_h < 114.4\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle ZZ \to jj \nu \bar{\nu}, ZW \to jj \ell \nu, WW \to jj \ell \nu, Z + {\rm jets}, W + {\rm jets}\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle m_h\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle \pi\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle h \to WW\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle Z + b \bar b\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle Zh \to \nu \bar \nu b \bar{b}\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle S/{a/2 + \sqrt{B}\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle M_{\rm T}\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle \Gamma_{h_{\rm inv}}\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle b\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle t \bar t\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle p_{\rm T}\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle \ell\end{math}
}
\clearpage
{
\color{black}
\begin{math}\displaystyle ZZ \to b \bar{b} \nu \bar \nu\end{math}
}
\clearpage
\end{document}
STDERR:
This is pdfTeX, Version 3.1415926-2.5-1.40.14 (TeX Live 2013)
 restricted \write18 enabled.
entering extended mode
(/tmp/0Nnf111GbA/cFNlYXmmvd
LaTeX2e <2011/06/27>
Babel  and hyphenation patterns for english, dumylang, nohyphenation, lo
aded.
(/usr/share/texlive/texmf-dist/tex/latex/base/article.cls
Document Class: article 2007/10/19 v1.4h Standard LaTeX document class
(/usr/share/texlive/texmf-dist/tex/latex/base/fleqn.clo)
(/usr/share/texlive/texmf-dist/tex/latex/base/size12.clo))
(/usr/share/texlive/texmf-dist/tex/latex/amsmath/amsmath.sty
For additional information on amsmath, use the `?' option.
(/usr/share/texlive/texmf-dist/tex/latex/amsmath/amstext.sty
(/usr/share/texlive/texmf-dist/tex/latex/amsmath/amsgen.sty))
(/usr/share/texlive/texmf-dist/tex/latex/amsmath/amsbsy.sty)
(/usr/share/texlive/texmf-dist/tex/latex/amsmath/amsopn.sty))
(/usr/share/texlive/texmf-dist/tex/latex/xcolor/xcolor.sty
(/usr/share/texlive/texmf-dist/tex/latex/latexconfig/color.cfg)
(/usr/share/texlive/texmf-dist/tex/latex/graphics/dvips.def))
(/usr/share/texlive/texmf-dist/tex/latex/base/latexsym.sty)
No file cFNlYXmmvd.aux.
(/usr/share/texlive/texmf-dist/tex/latex/base/ulasy.fd) [1] [2] [3] [4]
[5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20]
[21] [22] [23] [24] [25] [26] [27]
! Misplaced alignment tab character &.
l.152 \begin{math}\displaystyle m_h &
                                     lt; 114.4\end{math}
[28] [29] [30] [31] [32] [33] [34]
! Missing } inserted.
 
                }
l.187 ...\displaystyle S/{a/2 + \sqrt{B}\end{math}
                                                  
[35] [36] [37] [38] [39] [40] [41] [42] (./cFNlYXmmvd.aux) )
(see the transcript file for additional information)
Output written on cFNlYXmmvd.dvi (42 pages, 10376 bytes).
Transcript written on cFNlYXmmvd.log.
Edit | Attach | Watch | Print version | History: r2 < r1 | Backlinks | Raw View | WYSIWYG | More topic actions
Topic revision: r2 - 2012-06-29 - JiaFuLow
 
    • Cern Search Icon Cern Search
    • TWiki Search Icon TWiki Search
    • Google Search Icon Google Search

    Sandbox All webs login

This site is powered by the TWiki collaboration platform Powered by PerlCopyright & 2008-2020 by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
or Ideas, requests, problems regarding TWiki? use Discourse or Send feedback