search for charged higgs bosons with h ± -> -> hadrons decay mode in fully hadronic final...
TRANSCRIPT
Search for Charged Higgs bosons with
H± -> -> hadrons decay mode in fully
hadronic final state
Ritva Kinnunen Matti Kortelainen, Sami Lehti and Lauri Wendland
Helsinki Institute of Physics
Alexandre Nikitenko Imperial College, UK
Monoranjan GuchaitTata Institute, Mumbai
Tiit SeppTarto, Estonia
Alexandros AttikisNicosia, Cypros
Outline
•IntroductionSignal and background processes Short term goals for H± searches
•Research highligts from 2008/2009-jet identification for H± searches
Muon replacement methodTau-trigger efficiency measurement
•Status and Plans for analysis with dataAnalysis methodsBackground measurements from data
Signal and background processesSignal and background processes
Production through tt -> tbtbH±, gb -> tgb -> tH±, gg(qq) -> gg(qq) -> tbH± processes
Background processes for fully hadronic final states: tt, W1->W2->qq’’ tt, W1->W2->e//+ ’ W+3/4jets, W-> QCD multi-jet events, fake ’s, fake MET
Simulated event display oftbH+ bW(cs) + b +
with radiative gluon in r, projection
Short term goals for H± searches
The focus of the HIP group has been so far the search of the heavy
charged Higgs bosons with mH+ > mtop
In view of the LHC low luminosity runs emphasis has been moved
towards lower Higgs boson masses, mH+ ≤ mtop
New process included
tt -> tb tbH± -> jet + 2 b jets + 2 jets + missing ET
with fully hadronic final state
Reach of H± discovery and exclusion in tt -> tb tbH± production is
expected to superseed that of Tevatron already with 200 fb-1
•Backgrounds und analysis methods similar to the searches of heavy
Charged Higgs bosons
Responsability of this channel on the HIP group
Light charged Higgs bosons from tt->WbH+bTevatron and LEP limits
Andrey Korytov (UF) Physics Week, May 14, 2009 7
Current list of “must-do” analyses
– all analyses going beyond this list are always welcome—bring it on!
– A few analyses not listed above are being evaluated for their competitiveness: BSM double-charged Higgs, VBF HWW, MSSM heavy charged Higgs, MSSM H
Research highlights from 2008/2009
1. -jet identification for H± searches
2. Implementation of a new method to replace muons with MC ’s for for background measurement from data
3. Tautrigger efficiency measurement from data
-jet identification for H+ searchesl Cuts were reoptimized for best separation against QCD multi-jet events
- correlations between the selections taken into account- cuts can still be tightened, if necessary
l Standard -jet identification cuts were used with high ET cut- Jet ET > 119 GeV, leading track pT > 20 GeV/c- Charged track isolation and isolation of electromagnetic energy deposition- Matching of track p to hadronic energy deposition to reject electrons
l Helicity correlations were used to suppress taus from W decays- R=ptrack/Evis. jet > 0.8- suppresses also further hadronic jets with neutral particles
l Results for 1-prong decays with triggerexcluding missing ET
- Signal efficiency 2-5 % with high purity- QCD background suppressed by a factor of 105 or better- ttbar and W+3/4 jets backgounds suppressed by a factor of 104 or better
l Also 3-prong decays are promisingl Improvement expected from
particle flow jets- Better energy resolution of jets, etc.
Cro
ss-s
ect
ion, fb
Results for 1-prong tau identification
signal
QCD
ttbar
W+3/4 jets
R. KinnunenHelsinki Institute of Physics
FinnCMS meeting, December 19, 2008
Muon replacement method
• A method for replacing a muon with MC tau is being developed as a
tool in CMSSW
• For each selected muon a tau with the same momentum is generated
with correct polarization state
• Full detector simulation for taus
• Muons are removed from the event, and the new taus are merged with
the rest of the event at DIGI level
• Event is finally reconstructed with the standard CMSSW algorithms
and used for analysis
R. KinnunenHelsinki Institute of Physics
FinnCMS meeting, December 19, 2008
Muon replacement validation
• First testing and validation with Z -
>μμ data by replacing the muon with
higher pT
with a muon
– We were able to identify a few problems which have been fixed
– The figures on the right show that the replacement is technically working well
• Physics validation with tt and W+jets data samples by replacing a muon with a tau
Tau Trigger Efficiency Measurement
Matti Kortelainen and Sami Lehti
Helsinki Institute of Physics
Chi-Nhan Nguyen
Texas University
Michail Bachtis
University of Wisconsin
Andres Florez, Eric Brownson, Edouardo Luiggi
Vanderbilt University
Simone Gennai
Pisa
Goals
• Develop methods and tools for measuring the tau trigger efficiency• Starting the development and testing with simulated Monte-Carlo data • Preparing for the real data
o Planning a study with the first data and aiming for one of the early publications in CMS
Methods
• Start with fake taus, since there won’t be enough genuine taus for some time• Selection
o Muon triggers to avoid bias on jets- W+jets as fake tau source- Z-> with one tau decaying into a muon as the signal
• Parameterizationo Usually a lot of fake taus with soft Calo deposits pass tau identificationo Efficiency obtained from the fake tau methods give usually lower efficiencies than real taus (CDF experience)o Use parametrization to take that into account
Jet reconstruction efficiencies
1 jet reco eff• Z->• QCD
L2 jet reco eff• Z->• QCD
Level-1 efficiencies
Level-2 efficiency
R. KinnunenHelsinki Institute of Physics
Staus and Plans
Status and
Plans for analysis with data
The group will work in the following sectors with the 2009/2010 data
1. Measurement of tau-trigger efficiencies
1.Testing of analysis methods for H± searches
3. Measurement of backgrounds for H± searches
4. Search of the light charged Higgs bosons with
tt -> tbH± -> jet + 2 b jets + 2 jets + missing ET
Publication expected with 200 fb-1
R. KinnunenHelsinki Institute of Physics
FinnCMS meeting, December 19, 2008
Analysis methods
• Selection of fully hadronic events - Veto on associated electrons and muon (from W->e) to be
performed with standard e,-identification methods: optimization in progress - Veto on associated jets (from W->) challenging: work for a new method in progress
Identification of one energetic hadronicjet, ET > 100 GeV: -optimization already performed with calorimeter jets -optimization with Pflow method in progress Missing ET > 100 GeV: tests of the new methods tcMET, PFMET in progress
B tagging: standard methods for b-tagging in tt events
W and top mass reconstruction: application of kinematic fit methods of the Top group in progress
Transverse mass reconstruction from the jet and Missing ET - backgrounds: mT( jet, MET) < mW
R. KinnunenHelsinki Institute of Physics
FinnCMS meeting, December 19, 2008
Measurement of tt and W+jet backgrounds from data
Motivation:• tt and W+3/4jet events can lead to background in signal area (large mT( jet, MET))due to MET uncertainty• tt events can lead to background in signal area also due to leptonic decaysof the associated W• The W-> decays in muonic multi-jet events can be used to measure these backgrounds from data
Method:• Replace exatly one isolated muon with a with the same energy and decay the with correct polarization state -> muon replacement method
• Select and replace two isolated muons to estimate the background from recidual associated W-> decays• Perform the identification and run the standard signal selection • No separation of tt and and W+jet backgrounds
Status:- MC studies in progress- Preparation for transfering the muon data (muon trigger + muon skimms) to Helsinki T2 center
R. KinnunenHelsinki Institute of Physics
FinnCMS meeting, December 19, 2008
Method:•Select QCD multi-jet events taking randomly one jet with ET
jet > 100 GeV as the – jet candidate•Perform the standard event selection• Scale the selected events with -jet mis-identification efficiencymiss-id) to be measured with QCD di-jet events from pre-scaled jettriggers with the early LHC data (the +jet and Z+jet event rates are too low for ET > 100 GeV)
Measurement of QCD multi-jet background from data
Motivation:•The QCD multi-jet background can lead to background in the signal area due to fake MET•This background can be measured exploiting the hadronic multi-jet data
Status:•Preparive studies in progress•Apply and optimize methods of the the ongoing -fake rate studies for other physics channels