SUSY LHC Darin Acosta University of Florida On behalf of the ATLAS and CMS Collaborations.

SUSY Physics @ LHCSUSY Physics @ LHCDarin Acosta

University of Florida

On behalf of the ATLAS and CMS Collaborations

HCP 2006, SUSY @ LHC acosta @ phys.ufl.edu2

OutlineOutlineConcentrate on inclusive search strategies for SUSYNew proto-analyses from CMS Physics TDR

Canonical SUSY searches : Jets + Missing transverse energy Lepton + jets + Missing transverse energy Dileptons (OS, SS) + Jets + Missing transverse

energy Di-taus + jets + Missing transverse energy

Heavy Reconstructed Object based SUSY searches Z0 + Missing transverse energy top + Missing transverse energy

sParticle spectroscopy and spin analysis:

MSSM Higgs covered in previous talk


SupersymmetrySupersymmetryA symmetry between fermions and bosons

Avoids fine-tuning of SM, can lead to GUTs, prerequisite of String Theories, possible dark matter candidate (LSP)

Generally assume LSP is stable (Rp conservation)SUSY breaking mechanism is unknown many params.mSUGRA:

Supergravity inspired model, 5 free parameters: m0, m1/2, A0, tan , Sign(µ)


Cross Sections and SignaturesCross Sections and Signatures

Complex decays chains MET (LSP) High PT jets ( q, g ) Leptons ( , l, W, Z ) Heavy flavor (high tan)

A0=0, tan(β)=10, sign(µ)=+1

~ ~~ ~


The Large Hadron ColliderThe Large Hadron Collider

Proton-proton collider, s = 14 TeVLow luminosity phase: L = 21033 cm-2s-1

5 inelastic pile-up collisionsHigh luminosity phase: L = 1034 cm-2s-1 (100 fb-1/yr)

25 inelastic pile-up collisions Start-up slated for 2007, second half

R = 4.5 kmE = 7 TeV

CERN

CMS

Atlas


The Compact Muon Solenoid (CMS) Expt.The Compact Muon Solenoid (CMS) Expt.

PbWO4 Crystals: / e detection

Muon chambers

Silicon Tracker:charged particle tracking and b/ id

4T magnet

Hadronic calorimeter:Jets, missing ET ()

One of two large general purpose experiments at the LHC


CMS at Surface Assembly HallCMS at Surface Assembly Hall2/

06


A Toroidal LHC ApparatuS (ATLAS)A Toroidal LHC ApparatuS (ATLAS)

Muon chambersSilicon and TRT Tracker2T solenoid

0.6T Toroids

Calorimeters (LAr): / e, Jets, missing ET () measurements

Complementary detector technologies to CMS


ATLAS UndergroundATLAS Underground5/

06

New Analysis Developments from CMSNew Analysis Developments from CMS

http://cmsdoc.cern.ch/cms/cpt/tdr/

CERN/LHCC 2006-001 CERN/LHCC 2006-021

Published Coming June 2006


CMS Physics TDRCMS Physics TDRCMS has recently published Volume 1 of its Physics Technical Design Report, with Volume 2 to come next month (but new results included here) ATLAS Physics TDR: CERN/LHCC 1999-14/15

Volume 1: Compendium of detector performance, calibration &

alignment strategies, and reconstruction algorithms for physics objects (e, , µ, , b, jet, MET)

Volume 2: Detailed study of several benchmark analyses, including

SUSY, to demonstrate key performances of the detector and including all the methodology of a real data analysis

Background estimation, systematic uncertainties, etc. Comprehensive collection of analyses that span most final

state topologies to determine overall reach (e.g. mSUGRA) Analyses based on GEANT4 detector simulations

(or derived parameterizations) for backgrounds and signals and real reconstruction algorithms studied in Vol.1

Inclusive Search Strategies for Inclusive Search Strategies for Final States with METFinal States with MET


StrategyStrategyUse Missing Transverse Energy (MET) as the key signature for SUSY in analyses presented here Rp conservation, neutral LSP

SUSY benchmark points studied in detail using GEANT-based detector simulation and full reconstruction algorithms

Consider all backgrounds as well as lepton fakes QCD multi-jets, W/Z+jets, t-tbar, diboson

Optimize significance to determine cuts at a particular benchmark point(s)

Determine 5 reach in mSUGRA space using fast simulation


MET ReconstructionMET ReconstructionSum over calorimeter towers

Can correct for jets, muonsMET Resolution

Measure from data Use min-bias and prescaled

jet triggers to measure resolution CMS stochastic term ~0.6–0.7

Jet calibration crucial to improve resolution Variety of techniques possible -Jet balancing, di-jet balancing, W mass constraint in hadronic

W decays in top pair events CMS: Achieve 3% JES uncertainty

for ET>50 GeV with 1–10 fb-1

QCD Minbias


CMS Benchmark Test PointsCMS Benchmark Test PointsBasis of detailed studies Low mass points for

early LHC running but outside Tevatron reach

High mass points for ultimate LHC reach

Indirect constraints from WMAP for strict mSUGRA exclude most except LM1, 2, 6, 9


Inclusive MET + JetsInclusive MET + JetsMost sensitive signatureFor low mass Supersymmetry, no problem to have a large excess of events over the SM at the LHCDifficult part is to convince yourself that there is a real excess! MET dataset cleanup

Use e.g. Tevatron-inspired event shape cuts for non-collision backgrounds (no LHC data yet!)

Event EM fraction >0.1 Event charged fraction >0.175 1 vertex

Set up control regions that enhance background over signal to calibrate from data W/Z+jets, top pairs, QCD dijets

Understanding of systematic uncertainties Sensitivity to Jet Energy Scale uncertainty and

resolution

D. Tsybychev, Fermilab-thesis-2004-58

EEMF ECHGF


MET calibration using Z-candleMET calibration using Z-candleMeasure Z+jets with Zµµ in data to normalize the Z (invisible) contribution and calibrate MET spectrum

With ~1fb-1 we will have enough Z+jets in the PT(Z)>200 region of interest to normalize within 5% the Z invisible process as well as W+jets through the W/Z ratio and lepton universality

CMS


Inclusive MET + Jets Inclusive MET + Jets Cuts

MET>200 + Clean-up 3 jets:

ET> 180, 110, and 30 GeV

||< 1.7, 3, 3 Cuts on between jets and MET HT=ET1+ET2+ET3+MET >500 GeV Indirect lepton veto

Results LM1 efficiency is 13% S/B ~ 26 Systematic uncertainty:

~6 pb-1 for 5 discovery Low jet multiplicity requirement reduces sensitivity to higher-order QCD corrections

CMS


Add lepton, clean triggerCuts (optimize @ LM1):

1 isolated muon pT > 30 GeV

MET > 130 GeV 3 jets:

ET> 440, 440, and 50 GeV

||< 1.9, 1.5, and 3

Cuts on between jets and MET

Background (10 fb-1) 2.5 events, Systematic uncertainty 20%

30 fb-1 and 60 fb-1 : Re-optimised cuts for higher lumi

Optimised cuts for 10 fb-1 luminosity

10 fb-1

30 fb-1

60 fb-1

A0=0, tan(β)=10, sign(µ)=+1

Inclusive MET+Jets+MuonsInclusive MET+Jets+Muons

m0

m1/

2


Same-Sign Muon SignatureSame-Sign Muon SignatureSignal: Background:

Motivation and Strategy: Clean objects for trigger and reconstruction

(muons) Reduced detector uncertainties vs pure Jets/MET

Low background (same-sign signature) Isolate the SUSY diagrams with strong isolation and

quality cuts on the reconstructed muonsTheoretical studies include:

H. Baer et al. PR D41, #3 (1990); R. Barnett et al. PL B315 (1993), 349; K. Matchev and D. Pierce hep-ph/9904282 (1999)

Lpp gu X 1 d

L

01

1t t1 b

L 01

pp tt X W b

Y

W b


LEPTevatron

Same-Sign Muon: ReachSame-Sign Muon: ReachCuts (optimize @ LM1):

2 SS isolated muons pT > 10 GeV

MET > 200 GeV 3 jets:

ET1>175 GeV

ET2>130 GeV

ET3>55 GeV

Background (10 fb-1) 1.5 events Systematic uncertainty 23%

A0=0, tan(β)=10, sign(µ)=+1

Optimized cuts for 10 fb-1 luminosity

CMSCMS

m0

m1/

2


MET + Opposite Sign Leptons MET + Opposite Sign Leptons Cuts (optimize @ LM1):

2 OS SF isolated leptons

pT > 10 GeV MET > 200 GeV 2 jets:

ET1>100 GeV

ET2>60 GeV

|| < 3

Background (1 fb-1) 200 events, mostly t-tbar Systematic uncertainty 20%

LM1 Signal (1 fb-1) 850 events

CMS


Opposite Sign Leptons: Mass EdgeOpposite Sign Leptons: Mass EdgeMeasure invariant mass distribution of same-flavor opposite-sign (SFOS) leptons as evidence for or

Striking signature: endpoint in mass spectrum exhibits sharp edge dependent on sparticle masses

LM1 with 1 fb-1 : with uncertainty on alignment and energy scale

0 02 1 0 0

2 1

max 0 02 1m m m max 2 0 2 2 2 0

2 1 /m m m m m m

max 80.4 0.5 (stat) 1.0 (syst) GeVm

Subtract different favor leptons


Inclusive MET + ZInclusive MET + Z00

Catch Mostly from q, g decays Z0 gives extra handle against

non-resonant dilepton bkg

Cuts (optimize @ LM4): MET > 230 GeV 2 OS SF leptons

pT(e) > 17 GeV, or pT(µ) > 7 GeV

81 < Mll < 96.5 GeV < 2.65 rad

Background (10 fb-1) SM: 200 40 (t-tbar + diboson) Systematic uncertainty 20%

LM4 Signal (10 fb-1) 1550 30

0 0 02 1 Z

e+e–

~ ~ CMS


Inclusive MET + TopInclusive MET + Top Catch stop decays to topSearch (optimize @ LM1):

MET>150 GeV Hadronic top selection and 2C fit

1 b-jet + 2 non-b jets Use the W and top mass constraints to fit top

and require good 2

LM1: ~200 pb-1 for 5 observation!

sParticle Spectroscopy, circa “2010”sParticle Spectroscopy, circa “2010”

End of decade: excess observed in a channel like one these shown!

What are the masses?

Is it SUSY?

The fun begins…


MET + di-TauMET + di-TauCatchMeasure di-tau endpoint and infer sparticle massesBut no sharp reconstructed endpoint due to Fit to signal + background can

be translated to endpoint measurement

Measure a number of invariant mass distributions, e.g. 2-tau, tau1+jet, tau2+jet,

tau1+tau2+jetExtract the masses of the sparticles by solving for the kinematics of the decay chain; example measurement at 40 fb-1 at LM2:

0 02 1q q q q

CMS


ATLAS sParticleATLAS sParticle


ATLAS SpinATLAS Spin


ConclusionsConclusions

SUSY LHC Darin Acosta University of Florida On behalf of the ATLAS and CMS Collaborations.

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Transcript of SUSY LHC Darin Acosta University of Florida On behalf of the ATLAS and CMS Collaborations.