# Presentation: 730370

## Les Houches Plans

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

## 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

- Greg Landsberg - Les Houches Plans

- June 28, 2007 - Les Houches Workshop

## 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 cos* distribution leaving the Mll intact
- Formalism: 2D fit:

- 200 pb-1, e+e-

- Event
- Callas

- Interference effect

**TeV****-1**** ED, 1/R = 0.8 TeV**

- Clean signature, low backgrounds

- Greg Landsberg - Les Houches Plans

- June 28, 2007 - Les Houches Workshop

## The Signature

- Spectacular signature; spectacular events

- Event Callas: Mee = 475 GeV, cos* = 0.01

- Greg Landsberg - Les Houches Plans

- June 28, 2007 - Les Houches Workshop

## Other Possibilities

- Compositeness/ADD		   RS Model

- Run II, 200 pb-1

- Greg Landsberg - Les Houches Plans

- June 28, 2007 - Les Houches Workshop

## Signature Matrix

- Table of signatures

| Model | Effect | Next step |
| --- | --- | --- |
| GRS |  = 0, N  0 | Look in diphotons; look for BH, second resonance |
| ZKK/KK |   0, N  0 | Correlate the interference dip with the peak cross section |
| Z’, ZH |  = ?, N  0 | Cu/Cd fit – get Tim Tait to work! |
| ADD |   0, N = 0 | Look in diphotons; look for BH |
| T/T |  = 0, N  0 | Look in W+jj channel; send Ken flowers; send Gordy a card |
| LQ’s, RPV |   0, N = 0 | Look for pair LQ production in lljj; generic search for RPV SUSY |
| Compositeness |   0, N = 0 | Look in diphotons; correlate dielectrons and dimuons; look in dijets |

- Greg Landsberg - Les Houches Plans

- June 28, 2007 - Les Houches Workshop

## 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

- Greg Landsberg - Les Houches Plans

- June 28, 2007 - Les Houches Workshop

## 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. LQ’s and DY

- Greg Landsberg - Les Houches Plans

- June 28, 2007 - Les Houches Workshop

## 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/view/CMS/SomeSamplesSUSYBSM2007](https://twiki.cern.ch/twiki/bin/view/CMS/SomeSamplesSUSYBSM2007)_

- Greg Landsberg - Les Houches Plans

- June 28, 2007 - Les Houches Workshop

## 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.htm](http://hep.brown.edu/users/Greg/TrueNoir/index.htm)_

- Greg Landsberg - Les Houches Plans

- June 28, 2007 - Les Houches Workshop