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DOE REVIEW. Wisconsin at ATLAS (2) SUSY and Exotics. Yibin Pan. For the Wisconsin Task H. May 15, 2007. Physics Beyond The Standard Model. Our Wisconsin group has been doing wonderful work on the Standard Model Higgs (see Sau Lan’s presentation).

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slide1

DOE REVIEW

Wisconsin at ATLAS (2)

SUSY and Exotics

Yibin Pan

For the Wisconsin Task H

May 15, 2007

physics beyond the standard model
Physics Beyond The Standard Model
  • Our Wisconsin group has been doing wonderful work on the Standard Model Higgs (see Sau Lan’s presentation).
    • We are a leader in the studies for the SM Higgs
    • But that’s not the only physics we are working on at ATLAS
  • Topics we are working on besides SM Higgs
    • SUSY searches.
    • Heavy resonances like Z’ and W’
    • Non-SM Higgs or Higgs-like particles
  • Experience and Efforts
    • Since LEP time, we have accumulated a lot of experience on the searches for new particles.
    • In ATLAS Higgs analyses, we cover all important final states with signatures made of jets, leptons, photons, missingET, etc.
    • We are in a privileged position with our expertise on missingET
    • We are making extensive efforts to put all these expertise together for new particle searches at ATLAS.
super symmetry susy searches

p

p

~

c01

~

~

~

q

~

c02

l

g

Missing energy

A sample SUSY decay chain

q

q

l

l

Jets

Leptons

Super Symmetry (SUSY) Searches
  • SUSY events are rich combinations of:
    • Missing energy.
    • Leptons
    • Jets
  • The keys to SUSY searches:
    • Make good use of identified objects (missET, e/m, jets)
    • Using data control samples to estimate backgrounds.
    • Interpret any excess over background with statistical analyses

 Our group is a major player in all these areas.

slide4

SUSY signals are not

“well defined”

Backgrounds need

to be estimated

from data.

An Example SUSY “Discovery” Plot

S. Padhi

Meff=∑|pTi| + ETmiss for 1 lepton+jets

inclusive susy searches
Inclusive SUSY Searches
  • Given the vast SUSY parameter space, it is important and beneficial to have a versatile search strategy.
  • Our group is conducting “inclusive” SUSY searches in which we scan through topology space of missingET plus:
    • 0-Lepton + Jets*
    • 1-Lepton + Jets*
    • 2-Lepton + Jets*
    • 3-Lepton + Jets*

* The “jets” requirement can be 2-jet/3-jet/4-jet/inclusive, etc.

  • It is important to have accurate estimation of the backgrounds in each case.

 Background estimation has to be data driven.

extraction of the w jets background a fully data driven approach developed by wisconsin

Calibration

side

Signal side

MT<80GeV

MT>80GeV

Extraction of the W+jets Background: A Fully Data Driven Approach Developed By Wisconsin
  • The goal: Obtain a reliable estimation of W+jets bkg from data.
  • Divide the sample into Calibration and Signal Sides
  • Obtain absolute normalization of W+jets on the calib. side with Z+jets data
  • Find a data control sample that reproduces W+jets shape
  • Extrapolate from calib. side to signal side
formalism for w jets extraction
Formalism For W+jets Extraction
  • This fully data driven method was first proposed and presented by our group in July 2006.
  • It is a unique method.

* Separately, we also proposed a method for ttbar background estimation

control sample performance
Control Sample Performance

Just one of the possible choices

Control Sample (ptj1>150, ptj3=0,1 lepton)

Signal selection samples:

“4jets”:ptj1,ptj2>100, ptj3,ptj4>50, 1 lepton

“3jets”:ptj1,ptj2>100, ptj3>50, 1 lepton

“inclusive”:S|ptj|>600, ptj3>0, 1 lepton

MET>250 GeV

w+jets

MT (GeV)

a sample progress report slide we showed in one of the susy working group meetings
A Sample “Progress Report” Slide We Showed In One of the SUSY Working Group Meetings

Significance Including bkg. Uncertainties @100pb-1

(Cuts: PTlep>20, S|PTjet|>600 , Ptj3>0, MT>80 GeV)

w/o sys.

w/ Dwj

working area

w/ Dwj, Dtt

30% better than previous analyses

slide10

2-lepton

SUSY Might Be Seen In The Very Early Days of LHC

(Same Sign)

(Opposite Sign)

0 and 1-Lepton+Jets(20 pb-1)

100pb-1

SU3

SU1

SU6

2-Lepton+Jets(100pb-1)

SU5

summary of our susy efforts
Summary of Our SUSY Efforts
  • Since last fall, our group has given ~30 talks in the ATLAS SUSY working group.
  • We covered a broad range of topics:
    • Inclusive (0-Lepton,1-Lepton, 2-Lepton, 3-Lepton) + Jets
    • Cut optimization
    • New discriminating variables
    • W+jets estimation, ttbar estimation.
    • Comparison of “fast” and “full” simulation
    • Fake lepton studies
    • Strategy of defining topology of “Jets”
    • Statistical methods
  • We are active and productive.
  • Will be ready when data come
slide12

Resonances at TeV Scale (Z’)

 Narrow resonances for ee and mm, if they exist, should be seen during early ATLAS runs. (~1000 events for 10 fb-1)

M(Z’)=1 TeV

Mee (GeV)

Mmm (GeV)

Z’tt is not as narrow,

But still feasible

slide13

W’ at ATLAS

  • Instead of a narrow peak, W’ events have a distinct distribution of transverse mass (MT)
  • The signal may be visible at 100 pb-1.

MW’=4TeV

MW’=2TeV

Background-only hypothesis

S+B hypothesis

MW’=2TeV

slide14

jet

jet

Heavy WW resonances(Higgs or Higgs-like particles)

Signal

Background

MH=500 GeV

MH=700 GeV

700 GeV Signal

3.48 fb

500 GeV Signal

5.34 fb

W+4jet

Background

14.94 fb

W+4jet

Background

14.94 fb

slide15

Discovery Reach

Z’→ee

SUSY

Higgs

W’

2009?

2008

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