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A first look at H -> . Catherine Wright University of Glasgow Glasgow Atlas Meeting 19/01/06. H -> . Ideal decay channel for low mass discovery. 100 < m H < 150 GeV If discovered via different channel, ideal for accurate mass measurement. Requires excellent calorimetry.
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A first look at H -> Catherine WrightUniversity of GlasgowGlasgow Atlas Meeting19/01/06
H -> • Ideal decay channel for low mass discovery. • 100 < mH < 150 GeV • If discovered via different channel, ideal for accurate mass measurement. • Requires excellent calorimetry. • Need good photon efficiency, high jet rejection. The decay mechanism for H ->.
H -> There are four main channels via which the higgs is generated. The production mechanism studied can have an effect on our ability to find the higgs via H ->
Production Mechanism Selection of production mechanism leads to different triggers and event selection requirements for H -> .
The Backgrounds The backgrounds for this decay are different depending on the production channel being analysed. Irreducible Background: real continuum from quark bremsstrahlung, born and box mechanism – direct production. W , Z , tt, bb - associated production. Reducible Background: jet/, e/ - for direct production l/jet, /jet, /jet/jet, l/jet/jet - for associated production Need excellent background reduction algorithms!
Initial Analysis The significance of this channel was below 5 in initial studies of only one production channel -> NOT a discovery channel!
Combined Analysis Researchers at Wisconsin focussing on this channel and on combined production channel analysis! In particular they are looking at H-> + jet(s). Different MC generators are used to produce various aspects of the signal and background. e.g. MC@NLO used to generate g-g fusion events. Events then face pre-selection cuts!
Combined Analysis cont’d • Currently: • Fixed jet rejection applied. What are the effects of this analysis on the significance of the H -> channel? • Results show not only VBF important but gg-fusion also significant.
The Significance This new combined analysis has lead to an improvement in the significance for the channel.
The Comparator • Developed by Chris Collins-Tooth • Designed to optimise, via 2 analysis, the fast simulation – forcing it towards the full simulation. • Provides a set of parameter values that minimises 2 for your data sets. • Opposite: • Example of • comparator run • for photons. Original Photon plot at low eta (<1,4) Tuned Photon plot at low eta (<1,4)
Future Analysis (??) • Future analysis should include better statistical determination of combined backgrounds, via e.g. cousins-huygens approximation. Plus investigation into systematic errors in this channel required. • Further studies of rejection of g/q initiated jets needed. • Effects of pile-up on mass reconstruction at low luminosity. • Use of Event Views in Analysis – this is the future of data analysis and therefore H-> should move in this direction. • Introduction of comparator for generating accurate, fast large backgrounds e.g. continuum.
Conclusions • Plan to investigate this channel further as a first year project and as part of a combined low mass Higgs analysis. • There is still much to be done with this low significance channel. • By using combined analysis methods the significance is raised above the all critical 5 level – one can further extend this idea to include other decay channels! Thank you!!
