Les Houches Plans

1
Les Houches Plans

• Greg Landsberg
• Les Houches Workshop
• June 28, 2007

2
Dileptons in Early LHC Data

• Many models predict observable effects in the
  dilepton spectrum
• Mass peak(s)
• Broad enhancement or depression of the DY
  background
• Two issues
• How to claim an observation?
• How to interpret an excess?
• Proposal
• Differential cross section or amplitude fit to a
  template

3
The Formalism

• Two variables the dilepton invariant mass and
  the scattering angle in the c.o.m. frame define
  the LO 2 ? 2 process completely
• NLO effects smear cosq distribution leaving the
  Mll intact
• Formalism 2D fit

200 pb-1, ee-
Event Callas
Interference effect
TeV-1 ED, 1/R 0.8 TeV

• Clean signature, low backgrounds

4
The Signature

• Spectacular signature spectacular events

Event Callas Mee 475 GeV, cosh 0.01
5
Other Possibilities

• Compositeness/ADD RS Model

Run II, 200 pb-1
6
Signature Matrix

• Table of signatures

Model Effect Next step
GRS L 0, N ? 0 Look in diphotons look for BH, second resonance
ZKK/gKK L ? 0, N ? 0 Correlate the interference dip with the peak cross section
Z, ZH L ?, N ? 0 Cu/Cd fit get Tim Tait to work!
ADD L ? 0, N 0 Look in diphotons look for BH
rT/wT L 0, N ? 0 Look in Wjj channel send Ken flowers send Gordy a card
LQs, RPV L ? 0, N 0 Look for pair LQ production in lljj generic search for RPV SUSY
Compositeness L ? 0, N 0 Look in diphotons correlate dielectrons and dimuons look in dijets
7
Comments

• Amplitude vs. cross section fit
• Fitting amplitudes is theoretically cleaner
• Extracting amplitudes may be experimentally
  challenging, especially due to NLO effects need
  to study
• Cu/Cd approach
• Promising
• Need to understand limitations
• Attempt to put TC models on the Cu/Cd plane

8
Plans

• Provide a code to do the cross section or
  amplitude fit in the mass/scattering angle plane
• Look at the interference effects between the
  s-channel and t-channel processes, e.g. LQs and
  DY

9
Highly-Boosted Top Quarks

• A number of models predict high-mass resonances,
  decaying predominantly into top pairs
• UED, RS models
• Z with enhanced couplings to third generation
• Challenges
• Highly-boosted top is likely to be reconstructed
  as a single fat jet
• B-tagging is challenging as the opening angle
  between tracks with high IP is very small
• Plans
• Use calorimeter information to try distinguishing
  such a fat jet from QCD using jet substructure
  and jet mass
• Work with others interested in b-tagging/tracking
  for such boosted jets
• Generated first samples of Z ? tt for 2 TeV and
  5 TeV Z mass with a full CMS detector
  simulation, see https//twiki.cern.ch/twiki/bin/v
  iew/CMS/SomeSamplesSUSYBSM2007

10
Black Hole MC Generators

• TRUENOIR a simple PYTHIA plug-in has been
  available since 2001
• Plans continue adding feature in the code,
  maintaining the Web page
• http//hep.brown.edu/users/Greg/TrueNoir/index.ht
  m