SUSY Inclusive Study & Discovery Potential
Mar.28-29, 2008. LHC kenkyukai @ U of Tokyo/ICEPP

Naoko KANAYA(University of Tokyo / ICEPP)SUSY CSC Note
ATLAS CSC note will be published in June.

• Show performance (significance) with various selections(N-jet, tau, b-jet, SS and 3-lepton) for some SUSY samples.
• Cut optimization and discovery reach for some SUSY models(mSUGRA, NUHM, mAMSB and GMSB etc)
SUSY５(inclusive studies)のアトラス公式結果はCSCノートを見てください。

SUSY signature @ LHC
Search for signatures of R-parity conserving SUSY
associated with neutral LSP.

Signatures @ LHC
cascade decay from squark
gluino productions yields

Multi-jet with missingET (MET)In this talk, the performance and our current knowledgeof inclusive SUSY searches.
Other SUSY signatures, GMSB -> O.Jinnouchi

Outline
Inclusive SUSY Analyses
Trigger and MissingET
Discovery Potential @ ATLAS
Summary and Outlook

Inclusive SUSY Analysis -1
Selection should :• gives good significance• robust to SUSY models and systematic errors fordiscovery (not for measurement)• easy to control at the point of systematic uncertainties
including background prediction.
Our bench mark analysis is so-called 4-jet analysis:

4-jet + n-lepton + MissingET

Understand 4-jet analysis (performance and systematicuncertainties) rather than further optimization.

Inclusive SUSY Analysis -2
4-jet selection (for multi-jet + MET)• NJET>3 : pT1st>100GeV, pT4th>50GeV and |η|<2.5• MET>100GeV• MET>0.2*Meff (Meff=Σ|pT| + MET)
• ST>0.2
Additional cut for better S/B•0-lepton•1-lepton•2-lepton(OS)Δφ(jeti-MET)>0.2 (i=0..2)mT(l-MET)>100GeV, pTe,µ>20GeV
OS (opposite sign), pTe,µ>20GeV, 10GeV

Background component (Alpgen prediction)•0-lepton•1-lepton•2-lepton(OS)ttbar(57%) , W(21%), Z(10%), QCD(12%)
ttbar(94%), W(5%)
ttbar(98%), W(1%)

Trigger -1
MissingET and Jet trigger are important for SUSY.
Jet will be more reliable especially at the early stage.
L1 granuｌality : towers = 0.2x0.2 (0.4x0.4 for FWD)
L1 noise suppression : 0.5-0.75 GeV
L2 : is similar to L1.
EF : cell base,0-th order calibration(no muon)

ttbar

110%
86%
57%

600GeV-1.5TeV

WMAP allowed region in mSUGRA
Benchmark Points(m0, m1/2,tanβ)

Trigger -2
Trigger menu is not fixed yet
for early run.
Example trigger menu (1033)•SU1(coannihilation) : 70, 350, 10•SU2(focus): 3550,300, 10•SU3(bulk): 100, 300, 6•SU4(low): 200, 160, 10•SU6(funnel): 320, 375, 50•SU8.1(coannihilation) : 210, 360, 40

Trigger efficiencies wrt events passing 0-lepton analysis
4jet 0-lepton

4jet 1-lepton• JETS = J400 | 3J165 | 4J110• XE=MET trigger

MSUSY~400GeVMET(Details was given by K.Terashi yesterday)

Need to understand performance :• Resolution• ScaleMore important for SUSY discovery• TailStart with simple MET reconstruction : cell-base + muon
Source of tails• dead/hot cells• bad run/data quality• fake/lost muons
No standard muonreconstruction @ η~0 and 1.1muon
CMSCorrection
(QCD)
• w/o
• withDiscovery Potential
A lot of things need to be done before physics analysis
and after too…

MC Data Sample
Background : Full Detector Simulation
Alpgen+Jimmy MC samples + EF

next pageSUSY Signal : Fast Simulation + transfer function
Too many parameters (not predictive).
Need some constraints.
Additional theoretical assumption on SUSY breaking.

• mSUGRA (scan m0-m1/2 plane with tanβ=10, A>0 and µ>0)
Bino LSP,• mAMSB (scan m0-m3/2 plane with tanβ=10 and µ>0)*+0+Wino LSP, "m = m(x1 # x1 ) ~ m($ )• NUHM (scan m0-m1/2 plane with tanβ=10, A>0 and µ>0)
Bino~Mixed LSP
Choice of |µ| and mA for ΩDM=0.1-0.16, Br(b->sγ)=(2.9-3.5)E-4!

Transfer Function (simulation)
There are many SUSY points in each models.
Not realistic to perform full simulation for all samples.
Parameterised detector response will be enough.
(not useful for complicated analysis, like b-tag)

Transfer Function (TF) -> Jet scale, resolution and lepton eff and fake.

MET resolution
FullFastTF

pT of fake lepton
ttbar
sample

Full
Fast

ttbar
sampleY. Kataoka, O. Jinnouchi

Background prediction
Dominant uncertainties originate in:-Fraction of W/top in control/signal sample-SUSY contamination• In Normalization Region (size)• In Control Sample (shape)

MET (1-lepton @ 1fb-1)

MET shape difference (bkg)

MSUSY=550GeV

Ntrue-NestNtrue

Background prediction -2
Example (mSUGRA with low/high msusy in 1-lepton mode)
Msusy=0.4TeV (m0=500,m1/2=150)
Bkg+SUSY
Bkg(pred)
Bkg(true)Msusy=1TeV (m0=400,m1/2=450)
Bkg+SUSY
Bkg(pred)
Bkg(true)

Need subtraction of SUSY contamination, like new MT
method for low MSUSY cases.

Background prediction -3
SUSY contamination is negligible Msusy>~600GeV…
mSUGRA (Control Sample)
SUSY contaminationin control sample

mSUGRA (1-lepton)
SUSY contaminationin normalization region(met=100-200GeV)

CS : May not problem (depends on shape of MET)

Need subtraction of SUSY contamination and evaluate its
uncertainty, like new MT method (G.Akimoto, Y.Kataoka)
for low MSUSY cases.

Discovery (ex. 1-lepton mode)
It will be problematic at low MSUSY(<600GeV).
No effect at the point of discovery reach.
S/√B (true)

S/√B (data-driven)

The study is on-going.
Assume the subtraction of SUSY contamination is successfully
done for the moment.

Discovery - 2
Significance Ns (C&H like) : 5σ -> discovery• 30% uncertainties on background prediction.
• background level : believe current MC prediction (true)
Example : mSUGRA 0-lepton (@1fb-1)
mgluino - msquark planem0 - m1/2 plane

No EWSB

stau LSP

5-sigma
5-sigma

NoEWSB

M0<100not scanned* msquark = average of 4 light flavor squark’s masses

Discovery Reach -1
Discovery reach on mgluino-msquark plane for mSUGRA @ 1fb-1mSUGRA (0-lepton)

mSUGRA (MET scan)

Fixed MET(100)MET scan0-lepton
1-lepton
2-lepton(OS)* MET scan (MET=100-500GeV)• Optimal MET cut depends on Msusy• Ns(0-lepton)~Ns(1-lepton) > Ns(2-lepton)
Of course, it depends on SUSY models.

Discovery Reach -2
Not completed, but discovery is strongly determined bySusy mass scale and almost independent of decay.
mSUGRA vs NUHM (@1fb-1)
0-lepton
1-lepton
2-lepton(OS)@low m1/2~~~~ prod.
qq+qg

mSUGRA
NUHM∼0∼0x4 " x3 Z∼+∼+x 2 " x1 Z!
!
~~qg prod.

Need systematic study for AFTER discovery*AFTER discovery… (will start..)What kind of information can be obtained in inclusive analyses?
Or.. Wait for exclusive analysis?

mSUGRA 1-lepton @ 1fb-1
m0=500,m1/2=350

Bkg(true)
Bkg(est)Bkg+SUSY
SUSY
Effective mass (Meff=Σ|pTjet| + MET) peakhas good correlation with MSUSY.

• Mpeak -> SUSY mass scale• Cross-section -> SUSY mass scale• B-jet, tau-jet, lepton rich or not…

AFTER discovery…-2
Effective mass peak
After Background subtraction
Bkg(true)
Bkg(est w/o SUSY)
Bkg(est w SUSY)

Effective Mass (1fb-1) : 0-lepton
True
Over est(+30%)
Under-est(-30%)

MSUSY~1TeV
Cross-section : Nobs*ε/LEfficiency (0-lepton) = 10-20%
Sys(JES=10%) -> dε=5-8%
Luminosity : 5%

Meff peak + cross-section--> SUSY mass scale

AFTER discovery…-3<Rlep1/0> ( = N(=1)/N(=0) )m1/2=300 GeV(Msusy~0.8TeV)MSUSY~0.8TeV
Meff > 1TeV~ 0 + q)~64%
Br (q~R ->χ
1~~
Br (χ + -> τ + + ν )~63%11τ

Nf1εε1
f1ε1=
Nf0εε0+Nf1ε(1−ε1) f0ε0+f1(1−ε1)m1/2=500 GeV(Msusy~1.3TeV)

MSUSY~1.3TeV
Meff >1.5TeV~ ~Br (qL ->χ1+ + q)~65%~+ ~+Br (χ1 -> l1 + νl )~38%
Br (g ->~t + ~t )~95%

Summary & Outlook
Study SUSY discovery potential with the latest event
reconstruction/detector simulation(geometry)
considering systematic uncertainties from detector
performance and background predictions.
Need to evaluate/subtract/suppress SUSY contaminationin control sample and normalization region, especially forlow mass SUSY.
Optimize cut/selection not at the point of significance but
Understand background and inclusive measurement.
Need to think about AFTER discovery, likeMsusy/cross-section measurement in inclusive studies.
Important to evaluate systematic uncertainties.