Download - A first look at H ->
A first look at H -> A first look at H ->
Catherine WrightUniversity of Glasgow
Glasgow Atlas Meeting19/01/06
H -> H ->
The decay mechanism for 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.
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 MechanismProduction MechanismSelection of production mechanism leads to Selection of production mechanism leads to different triggers and event selection different triggers and event selection requirements for H -> requirements for H -> ..
The BackgroundsThe BackgroundsThe 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 AnalysisInitial Analysis The significance of this channel was below 5 in initial studies of only one production channel.
Combined AnalysisCombined Analysis
Different MC generators are used to produce various aspects of the signal and background.
Researchers at Wisconsin focussing on this channel and on combined production channel analysis! In particular they are looking at H-> + jet(s).
e.g. MC@NLO used to generate g-g fusion events.
Events then face pre-selection cuts!
Combined Analysis cont’dCombined Analysis cont’dCurrently:
• Fixed jet rejection applied.
• Results show not only VBF important but gg-fusion also significant.
What are the
effects of this
analysis on the
significance of the H ->
channel?
The SignificanceThe Significance
This new combined
analysis has lead to an
improvement in the
significance for the
channel.
The ComparatorThe Comparator
Original Photon plot at low eta (<1,4)
Tuned Photon plot at low eta (<1,4)
• 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.
Future Analysis (??)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.
ConclusionsConclusions
• 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!
• Any suggestions for future work will be greatly appreciated!!Thank you!!