University of Iowa HEP Group
CMS Analysis
1
Outline
As University of Iowa HEP group, we are involved with several
different physics analysis.
•
Electroweak Symmetry Breaking
qqH, H
•
Forward Physics
•
Majorana Neutrino Study
•
Supersymmetry (SUSY)
1. mT2 (Separate background from signal)
2. A Data Driven Method to Estimate high ETmiss tail in QCD Events
•
New physics in dijet topology
2
EWK Symmetry Breaking
• Vector boson fusion process has the
second largest cross-section for Higgs
particle production. This channel requires
jet tagging in forward detector (HF).
3
• Our group members (Anthony Moeller and Alexi Mestvirishvili) study leptonic
decay channels of Higgs particle with jets in the forward region within the Higgs
group.
qqH, H
A study on Monte Carlo data for qqH
progress.
Anthony Moeller
leptonic decay is currently in
• Mass reconstruction methods for Higgs and backgrounds
are being studied for 115 and 130 GeV Higgs masses.
• Reconstruction only depends on ETmiss and final state
leptons.
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qqH, H
Backgrounds and Forward Jet Cuts
•
Background Distributions
Without any cut:
Backgrounds (W+jets, Z+jets,
ttbar, etc.,) will dominate
signal region.
To eliminate background, a cut on forward
tagging jets (HF) can be applied.
Signal from Vector Boson Fusion (VBF) has a
pair of forward jets whereas most common
processes don’t.
Anthony Moeller
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Forward Physics
• Centrally produced particles with low-x processes or jets in the forward regions
require the use of HF detectors for trigger and tagging.
• Members at CERN (Taylan Yetkin, Kerem Cankocak and Sercan Sen) are sharing
their detector and jet expertise with the forward groups and participating in analysis
efforts.
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Majorana Neutrino Study
Mass Reconstruction
Warren Clarida
The Majorana nature of the neutrino allows for lepton
number violation via di-lepton production without any
ETmiss. As the SM doesn’t allow for lepton number
violation this is likely a discovery channel.
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Majorana Discovery & Exclusion Results
Discovery and Exclusion results for different Majorana Neutrino mass scales.
5 Sigma Discovery
With only 100 pb-1 integrated
luminosity neutrino masses
lower than 180 GeV can be
excluded.
3 Sigma Exclusive
Warren Clarida
Integrated Luminosity
SUSY with mT2
In decays where lightest supersymmetric
particle(LSP) is pair produced and
escaped the detector(ETmiss), it is not easy
to determine the mass of the mother
particle. mT2 (formed as transfer mass
from 3 objects: jet, jet, ETmiss ) is defined to
put constrain on the mother particle mass.
Taylan Yetkin
arXiv:0907.2713v1
Alan J.Barr and Claire Gwenlan
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A Data Driven Method to Estimate high
ETmiss tail in QCD Events
Estimating SM background for SUSY.
Introduce an artificial imbalance by
smearing pT of the jets.
Smearing is done by using a
response function.
E. Asli Albayrak and Taylan Yetkin
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Response Function
The response function represents the effect of jet mismeasurements on ETmiss and
it is a combination of a Gaussian (RG) and a non-Gaussian (RNG) response.
Application of Response Function
• We form a multi-jet sample with low .
• pT of jets in this low MET sample is smeared by the response
function as
•
MET is recalculated for low MET events with the effect of
smearing.
Smeared ETmiss distribution
E. Asli Albayrak and Taylan Yetkin
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New Physics in Dijet Topology
Dijet signal one of the early discovery
topologies for CMS.
Discriminator Shape
Jane Nachtman is co-convenor of LPC Dijet
Topology group which focuses Fermilab
based effort.
• Di-boson signatures prove Higgs search
viability
• Test or provide Jet Energy Scale calibration
for b jets, mass resolution for Higgs
• Observation of di-boson process is an
analysis in itself
•
resonance as signature for new physics
(Technicolor)
Jane Nachtman, Kai Yi, Colorado Reed
(undergrad), Scott Griffiths (grad, spring
2010)
Summer 2009 work by Reed and K.E. Raghav (summer UG).
Discriminator Cut
mis-tagging
• Control channel for VH with
Efficiency
Analysis
b efficiency
Study of efficiency and purity of CMS b-jet
tagging algorithms (Colorado Reed)
Meeting and Conferences
•
study
– qqH Task Force Meetings (LPC)
– VBF Higgs Subgroup Meetings (CERN)
–
Meetings (CERN)
– VBF Workshop @ Fermilab by A. Moeller, June 2009
• Estimating ETmiss tail in QCD Events
–
–
–
–
LPC JetMet Topology Group Meetings
SUSY All Hadronic Meetings (CERN)
JTerm Meetings @ Fermilab by E.A. Albayrak (January 09 , August 09)
APS Prairie Meeting in Iowa City by E.A. Albayrak (November 09)
• Majorana Neutrino Study
– Exotica Physics Meetings (CERN)
– APS DPF meeting in Detroit by Warren Clarida (July 09)
• Forward Physics Studies
– Forward Physics Meetings (CERN)
• Dijet Topology
– LPC Dijet Topology Group Meetings
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