Randall- Sundrum Gravitons and Black Holes

at the LHC

Kevin Black

Harvard University

For the ATLAS and CMS Collaborations

Outline

TeV Scale Gravity Gravitons Black Holes Summary

Landsberg

State of the Standard Model

Effective model which describes data well

Accommodates but does not explain Fermion masses CP-Violation

Well known fine-tuning, hierarchy, triviality problems

LEP EWWG – Winter 2007

mH2 ~ ~

MPl2

Why Gravity at the LHC View Standard Model as

effective theory as a low energy approximation

New theory takes over at energy scale comparable to the Higgs mass 1 TeV SUSY, Technicolor, Little

Higgs, .. Perhaps there is no other

scale , GUT scale is ~ TeV Gravity made strong by extra

dimensions where gravity propagates

Randall – Sundrum Model SM fields on one of two

4-dimensional brane in a 5-D space time

Graviton can propagate in the bulk

Kaluza-Klein States on the order of TeV

Main parameters: Mass of Graviton Curvature parameter

( c = k/Mpl) Signatures in dilepton,

diboson, dijet final states

wk = MPl e-kr

q

q

l

l

Current Direct Limits

CDF Conference note 9160 PRL 100, 091802 (2008)

Mass limits from 300 – 900 GeV depending on coupling

Dimuon Signature Two reconstructed muons

One || < 2.1 One with PT > 24 GeV

Use angular distribution to discriminate spin

Main background SM Drell-Yan

c = 0.01c = 0.02c = 0.05c = 0.10

10 fb-1

100 fb-1

300 fb-1

See Dilepton Talk Later this session

Diphotons

Branching ratio twice as large as dilepton

Z’ doesn’t decay into diphotons Backgrounds

Direct Diphoton Production Photon + Jet Dijets (photon misidentification) Drell-Yan (missing tracks)

Two isolated photons with ET > 150 GeV Isolated both by calorimeter and

tracker

Dijets

Two jets | Fit invariant mass (leading 2 jets) Compare observed/predicted Including Systematics

Jet Energy Scale Jet Resolution Trigger Prescales Radiation

See Dijets talk later this session…

Black Holes

Dimopolous, Landsberg Black holes could form if

two colliding partons have impact parameter smaller than RS

Partonic Cross-Section given by geometry, total cross-section convoluted with PDFS

Decay by Hawking Radiation Demographic Decay Spherically Symmetric

E/2

E/2b

b < Rs(E) BH forms

RS2

Black Holes – Generator Studies

CATFISH Collider

grAviTational FIeld Simulator for black Holes

Comput.Phys.Commun.177:506-517,2007

Black Hole – CMS I Parameters

Plank Scale 2 TeV Black Holes 4 – 10 TeV

Signature high sphericity high ΣpT high multiplicity

Backgrounds tt, W/Z + jets, Diboson,

multijets Selection

MBH(reco) > 2 TeV Multiplicity > 4 Sphericity < 0.28

Black Hole – CMS II

ATLAS Black Holes Event Selection

Electron or muon with ||pT > 50 GeV Two approaches (almost identical results)

|pT| > 2.5 TeV (jets + leptons) At least 4 jets and lepton pT > 200 GeV

A n=2,m = 5-14 TeV

C n=2,m = 8-14 TeV

B n=4,m = 5-14 TeV

D n=7,m = 8-14 TeV

ABCD

ATLAS Black Holes 2

Reconstruct the visible mass of the black hole from all objects and MET

Very dramatic signature + large signal cross-sections

ATLAS Black Holes 3

Investigated Event Shapes Do give separation with

background Very different for different

parameters

ATLAS Black Holes 4

Discovery potential S/B > 5 S > 10

Discovery possible ranging from Few pb for 5 TeV ~1 fb for 9 TeV

Summary

Signatures from Gravitons and Black Holes would be dramatic compelling signatures

RS Gravitons should be observable ~5 TeV range and quickly observable for ~1 TeV masses

Black holes could be seen to very high masses (8-9 TeV) with a few to ~ 30 fb-1 of data (depending on parameters)

For older results go to ATLAS and CMS exotics pages

New ATLAS results expected to be made public ~few months…

Backup

Graviton Signatures at the LHC

Gravitons couple to momentum tensor (contribute to most SM processes)

Monojets Single Vector Boson

production Dilepton/Dijet/Diboson

production As resonance As non-resonant

modification to SM cross-section

q

q

g

g

g

G

g

G

q

q G

V q

q G

V

q

q

l

l

q

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V

V

Backup Dimuon I

Signal Cross-Sections

Drell-Yan Backgrounds – others on ~ 10 to 40 times smaller

Dimuon Backup II

Dimuon Backup III

Dimuon backup 4

Systematics Theory QCD and EW Scale – 13-17% PDF – 7%

Systematics Experiment Misalignment Pileup - negligible Background Shape – 10-15% shift in signficance Trigger –negligible (normalizations float in fit) Magnetic Field – negligable

Dimuon Backup 5

C = 0.01

C= 0.1

Solid line – idealDotted – long term alignmentDashed – “first alignment”

Diphoton Backup IDiphoton production

Photon + Jet

Dijet

Drell-Yan

Diphoton Backup II

Diphoton Backup III

Diphoton Backup 4Hard Process Scale PDF Uncertainties

Dijet Backup

Sezen Sekmen SUSY 07

Sezen Sekmen SUSY 07

CMS Black Hole Backup

Sphericity

PDF Uncertainties :

Uncertainty on Signficance ~ 12%

Black Hole Backup

CMS TDR -2006

Atlas Black Hole backup

As a function of black hole threshold