Exploring New Phenomena at CDF

Jane Nachtman (Fermilab) for the CDF collaboration

Objective• This workshop is about bringing theorists and

experimentalists together to focus on maximizing the Tevatron’s discovery potential

• The experimental talks will briefly summarize searches for new physics at CDF and D0– To help us think about what is possible and where

we should go from here– Looking for theorists’ input!

• We split the signatures– CDF – photons, jets + MET, hi-pt dileptons– D0 – leptons+jets, multi-leptons, long-lived

signatures

Overview of my talk• Brief CDF and Tevatron intro• CDF searches

– Signature-based, then applied to models• Photons

– Applied to GMSB, Extra Dimensions• Hi-pt dileptons

– Z’, G• MET+jet(s)

– SUSY, LED– Global, signature-based search of all CDF hi-

pt data (Vista+Sleuth)

CDF Detector

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Tevatron

Almost 2 fb-1 delivered, ~1.6 fb-1 recorded( 0.95 – 1.2 fb-1 for analysis, depending on which subsystems are used)4-8 fb-1 by 2009

The Tevatron’s performance is better than ever!!

Signature-based searches at CDF

• Philosophy – models come and go, but the data should stand on its own

• Design “simple” searches– No optimization for models no sophisticated cuts– Attempt to provide general result for theoretical input– Basic result : N expected from SM, N observed– Study kinematic distributions– Publish acceptance functions – plug in your own model

• Drawback – may not provide maximal sensitivity to a particular model – But may point us in the right direction to look further

Signature-based searches for photon+X

• Inspired by Run I hints– “eeMET” event– Excess in lepton+photon+MET (16 obs, 7.6 +/- 0.7

exp)

• Theoretical models suggest these signatures (eg GMSB)

• Mix-n-match: photons, leptons (e,), MET, jets,b-jets

Search for photon+lepton+X• 2 channels

– Photon + lepton(e,) + MET– Photon + lepton + lepton + X

• Look for high-pt leptons, photons, high MET (reduce fakes, SM backgrounds)

• In 930 pb-1 of data e+MET +MET l+MET SM 948 547 14813 Data 96 67 163

ee+X +X ll+XSM 395 263 658Data 53 21 74

SM is W/Z gamma, W+fakeNo events with extra photons, leptons observedSM is W/Z gamma, W+fakeNo events with extra photons, leptons,MET observedNo e

Check kinematics in l+gamma+MET

Diphoton + X searches• X = e,,,MET • Backgrounds evaluated from data

– Use sidebands – loose photons not passing signal photon selection

• Dataset = 1 – 1.2 fb-1

gg+X, X= SM Nobs e 3.8 +/- 0.5 1 0.7 +/- 0.1 0 MET 116 +/- 24 126 2.2 +/- 0.7 4

Kinematics in +X channels

Control region

Signal region

High-mass diphotons

• high ET (>15) isolated diphoton resonance– Backgroun

d : QCD diphotons (simulation), jets (from data)

Long-lived Exotic particles• D0 talk will cover more in detail, just one

photon-based search here• Several models predict long-lived particles:

charged or neutral, decaying inside or outside detector– Charged – look like slow muon (new CDF results

soon) or delayed jet– Neutral

• decay inside detector – delayed photons CDF analysis

• decay outside detector – photon + MET planned analysis

Delayed Photon Analysis• Relies on EM calorimeter timing

detector

Measure photon arrival time

background signal

signal region No new physics found here, so far

Interpret in GMSB

Search for Delayed Photons

Signature-based searches for dileptons + X at CDF• Look for excess above SM prediction in dilepton +X (X = photon,

lepton, b-jet, HT, Missing ET; dileptons can be same-sign or opposite-sign)– Set cuts on first 1/3rd of dataset,apply to larger dataset– can be further applied to many models; e.g. heavy quarks as first

exampleDilepton (ee, , e) + high HT

HT == scalar sum of electron and jet ET, muon pT, missing ET

No excess, but one event at HT=900!

Good agreement in HT<200 control region.

High mass dileptons• High ET electrons,

optimized to look for high-mass resonances (150-950 GeV)

• Applied to spin-1 Z’ and spin-2 RS Graviton

19% pe’s have 2E-3

Combine limits with diphoton on coupling vs graviton mass in RS model

Set limits on SM-like Z’

Search for Massive Resonances Decaying to ZZ eeee

Spectacular signature!!Model: RS Gravitons can

decay to ZZ, xBr=292fb (0.66 events expected in 2 fb-1 – not yet sensitive)

Signal region M(eeee) 500-1000 GeV

Like-Sign dileptons• Signature-based search • Currently: chargino-

neutralino production

Basic selection: expect 34+/-4, see 44Tight selection: expect 8 +/- 1, see 13

MET + Jets• Signature:

monojet events• Model: LED (ADD)• Graviton

production leads to excess (not resonance)

Set limits on MD vs N extra dimensions

MET + jets in SUSYSearch for

squarks/gluinos in MET + jets

Add flavor tagging for stop/sbottom

Vista/Sleuth – the ultimate signature-based search

• Algorithm to look at Tevatron data globally– Because new physics will probably not show up

where we are expecting it– Look in hundreds of final states simultaneously

• Vista – look at bulk distributions, find compatibility with SM (chi-square fit)

• Sleuth – look in hi-pt tails– Flag a final state as “interesting”– Show us where to look in more detail

• Further steps Quaero and Bard…to interpret new physics

summary• Tevatron searches are going at full steam

– Lots of analyses ongoing, new and interesting results coming out

– No new physics yet, but we remain hopeful• Need to focus our efforts for the full

Tevatron dataset – What can we learn from what we’ve already

done, to plan for the future?• We’ve tried to cover as much as possible,

but are we overlooking important signatures, models?

• Theoretical guidance for our program of Searches for New Physics

Backup Slides

SM and Other BackgroundsSM Collisions

Beam Halo

Cosmics

Signal Monte Carlo

How do I know how each background looks like? Can not use photons.

Signal (Blinded) Region

4 sources, all estimated from dataCollision photons from SM•Right vertex•Wrong vertexNon-collision “look-like photons”•Beam Halo•Cosmics

Highest Mass Diphoton Event (604 GeV/c2)

Highest Mass Diphoton Event

Top dilepton event at HT=900?

Leptons:e 28 GeV, 159 GeV

Jets :216 GeV (b-tag)199 GeV156 GeV15 GeV

MET: 90 GeV