Jay Wacker SLAC 34th Annual Johns Hopkins Workshop May 24, 2010 with M. Lisanti, J. Alwall, & M-P Le, and E. Izaguirre, & M. Manhart arXiv: , , , 1005.XXXX O GLUINO, WHERE ART THOU?

Plan of Talk An Odyssian Voyage Where we have been (Tevatron) Where we will be (14 TeV LHC) Where we are now (7 TeV LHC)

All started a few years back... Had an MSSM model that predicted a spectrum 70 GeV 80 GeV 140 GeV... Surely this must be excluded!?! The production cross section at the Tevatron is

I went through the 25 years of squark and gluino searches They all came back to versions of this: mSUGRA (Five parameters to rule them all) but where is ?

mSugra has “Gaugino Mass Unification” Most models look like this A shocking lack of diversity (see the pMSSM)

Solution to Hierarchy Problem Jets + MET Dark Matter Fewest requirements on spectroscopy If the symmetry commutes with SU(3) C, new colored top partners (note twin Higgs exception) Wimp Miracle: DM a thermal relic if mass is 100 GeV to 1 TeV Usually requires a dark sector, frequently contains new colored particles Doesn’t require squeezing in additional states to decay chains

Spectrum in Different Theories MSSM Universal Extra Dimensions High Cut-OffLow Cut-Off Large Mass SplittingsSmall Mass Splittings

Back to the question: Is an 80 GeV standard-issue gluino allowed? Hope to catch in Jets + MET Require energetic jets and unbalanced momentum

Jets + Missing Energy Cuts at D0 (Not exclusive searches) 1fb -1 analysis Which search will an 80 GeV gluino fall into? Simple searches counting experiments on tail of SM distribution

A careful look at the signal 80 GeV particle going to 70 GeV LSP and 2 jets In rest frame of each gluino: two 3 GeV “jets” and a LSP with 3 GeV momentum Parton level Detector level Totally invisible: faked by QCD with

Give the gluino big boost! Jets merge and MET points in direction of jet More energy, but looks like jet mismeasurement

Radiate off additional jet Unbalances momentum of gluinos

The Parameter Space in Gluino Searches mSugra Need to calculate:

Calculating Additional Jets Matrix Elements Necessary for well-separated jets Includes quantum interference Fixed order calculation Computationally expensive Limited number of partons Parton Showering QCD Bremstrahlung Soft/Collinear Approximation Resums large logs Computationally Cheap Unlimited number of partons Matching merges best of both worlds Necessary to avoid double counting A big advance in Monte Carlo calculations over past 10 years

Calculating Additional Jets Matrix Elements Parton Shower Decay veto if

An Example High MET cut doesn’t kill signal Unmatched Matched Tail is enhance by a factor of 10!

Start with a model and design a search to discover it Model Dependent Design Design a set of searches that will catch anything Most studies currently available are benchmarks within specific parameterizations (e.g. SU#, etc) What is the efficacy of searches outside parameterizations? (let alone to different theories e.g. UEDs) Make sure unexpected theories aren’t missed

Exclusive Jets + MET Search 4 Separate Searches, Individually Optimized Maximize significance for each

Tevatron Summary Necessary to consider multiple searches Multiple cuts for& Difficult to pull signal from background Searches are challenging Frequently low values of & are necessary These are hard searches!

A Comparison Between Optimized Cuts and Original Cuts Dijet most effective channel Not easy... but they’re providing more information now CDF (2.0 fb -1 ) BG Signal BG

Tevatron Reach 4 fb -1 An 80 GeV gluino is “ruled out”!

Where are we going to get to with the LHC? A lot further, a lot faster! The LHC is not a SuperTevatron (thankfully)

Casting a Wide Net Alwall, Le Lisanti, JW ( ) Kinematics matters more than spin or A-terms,... Tevatron Gluino Sensitivity mSugra 500 GeV 250 GeV

Signals “Gluinos” Large color, High Jet Multiplicity, High MET Large color, High Jet Multiplicity, Lower MET Octet Majorana Fermions “Squarks” Small color, Low Jet Multiplicity (6 copies of) Triplet Scalars Different “modules” used to explore generality

Plan of Talk Distinguishing Signal from Background Where the LHC can get to (soon) *

Discovery Criteria All jet channel Effective cuts really kill QCD NLO predictions not available for SM 30% Systematic uncertainty 5σ discovery requires S/B >1.5 Really want to eliminate SM backgrounds 1 fb -1 analyses at

QCD Backgrounds Madgraph+PythiaPGS Matching crucial to getting MET tail vaguely right 4 + jets

Signals Should use same methods for signals as backgrounds Parton Shower - Matrix Element Matching Signal may be in a different place than expected Extra jets aren’t a nuisance, they can qualitatively alter signal

Search Design Start with a range of jet multiplicities that can be statistically combined Lepton veto, MET separated from hardest 3 jets Lore is that only multijet is useful Based most from benchmark studies “Susy Without Prejudice” found multijets more useful, but didn’t go away from ATLAS cuts

New Initial States Possible at higher order Parton Luminosities

Radiation Degenerate spectra require radiation to generate signal Unbalanced momentum set by As p T of gluino increases, Final state jets get harder (and eventually merge), but won’t gain significant MET UED-like Theories

Radiation Radiation unbalances LSP’s momentum MET is generated by radiated jets Without extra jets, signal is invisible

Spectrum of Radiation Harder for New Physics Cross section for background is large due to lower SM CM energy When LSP is heavy (rest mass of LSP is unobservable)

Spectrum of Radiation Harder for New Physics Consider the additional cost of energy for radiating a jet off a particle, X, of mass m Identify

Spectrum of Radiation Harder for New Physics Cross section for background is large due to lower SM CM energy Equalizes CM energy for signal and background Increases S/B significantly When LSP is heavy (rest mass of LSP is unobservable) Radiate off a jet with Works because we’re beyond last SM threshold at the LHC

Plan of Talk Distinguishing Signal from Background Where the LHC can get to (soon) *

Multijet Universality Never found lower jet multiplicity to significantly enhance discovery Tried many different event shape variables and search strategies Degenerate spectra Light Squarks, Heavy Gluinos Qualitatively different than the Tevatron

14 TeV

3 Searches High MET Alpha Mid MET Gluinos, Squarks & Degenerate Spectra Gluinos, Squarks Cascade Decays

The Searches High MET Search

Introduced by L. Randall & D. Tucker-Smith The Alpha Variable Modified by CMS to multijet searches Group to minimize momentum imbalance

Discovery Reach Alpha Search AlphaHigh MET Directly decaying Squarks Directly decaying gluinos Alpha High MET Multijet still more effective than dijets

Cascade Decays Mid MET Search High MET Alpha Mid MET Lowers MET in Events

Squarks Squarks need radiation to get additional jets Multijet still more effective than dijets Alpha High MET

Extended Cascade Decays LSP is great-granddaughter Momentum is divided many different ways Reduces MET dramatically Worse case scenario Need a low MET search

7 TeV High MET Interpolating from Tevatron to 14TeV LHC (in progress) Base Search

Direct Gluino Decays Doubling the reach in the next year! Tevatron High MET

Direct Squark Decays High MET

Cascade Gluino Decays High MET Base

Other Gluinos Model Independent Bounds R-Parity ViolationSplit Susy Decays to 3 jetsQuasi-stable Use jet substructure w/G. Salam & A. Raklev Use jet substructure

Conclusion O GLUINO, WHERE ART THOU? Comin’ soon to a collider near you! Lessons from Tevatron (and before) on how not to design/present searches Simple search strategies will provide extensive coverage Discovery at the LHC in Jets + MET much easier than at the Tevatron