Randall Sundrum Gravitons and Black Holes at the
Randall- Sundrum Gravitons and Black Holes at the LHC Kevin Black Harvard University For the ATLAS and CMS Collaborations
Outline l l Te. V Scale Gravity Gravitons Black Holes Summary Landsberg
State of the Standard Model l l Effective model which describes data well Accommodates but does not explain l l l Fermion masses CP-Violation Well known fine-tuning, hierarchy, triviality problems m. H 2 ~ LEP EWWG – Winter 2007 ~ MPl 2
Why Gravity at the LHC l l View Standard Model as effective theory as a low energy approximation New theory takes over at energy scale comparable to the Higgs mass L ~ 1 Te. V l l l SUSY, Technicolor, Little Higgs, . . Perhaps there is no other scale , GUT scale is ~ Te. V Gravity made strong by extra dimensions where gravity propagates
Randall – Sundrum Model l l 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 Te. V Main parameters: l l l Mass of Graviton Curvature parameter ( c = k/Mpl) Signatures in dilepton, diboson, dijet final states q l wk = MPl e-kr
Current Direct Limits CDF Conference note 9160 PRL 100, 091802 (2008) Mass limits from 300 – 900 Ge. V depending on coupling
See Dilepton Talk Later this session Dimuon Signature l Two reconstructed muons l l One |h| < 2. 1 One with PT > 24 Ge. V Use angular distribution to discriminate spin Main background SM Drell-Yan 10 fb-1 100 fb-1 300 fb-1 c = 0. 02 c = 0. 05 c = 0. 10
Diphotons l l l Branching ratio twice as large as dilepton Z’ doesn’t decay into diphotons Backgrounds l l l Direct Diphoton Production Photon + Jet Dijets (photon misidentification) Drell-Yan (missing tracks) Two isolated photons with ET > 150 Ge. V l Isolated both by calorimeter and tracker
See Dijets talk later this session… Dijets l l Two jets |h| < 1 Fit invariant mass (leading 2 jets) Compare observed/predicted Including Systematics l l Jet Energy Scale Jet Resolution Trigger Prescales Radiation
Black Holes l Dimopolous, Landsberg l l l 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 l l Demographic Decay Spherically Symmetric b < Rs(E) BH forms E/2 b s = RS 2 E/2
Black Holes – Generator Studies l CATFISH l Collider gr. Avi. Tational FIeld Simulator for black Holes Comput. Phys. Commun. 177: 506 -517, 2007
Black Hole – CMS I l Parameters l l l Signature l l high sphericity high Σp. T high multiplicity Backgrounds l l Plank Scale 2 Te. V Black Holes 4 – 10 Te. V tt, W/Z + jets, Diboson, multijets Selection l l l MBH(reco) > 2 Te. V Multiplicity > 4 Sphericity < 0. 28
Black Hole – CMS II
ATLAS Black Holes l Event Selection l l Electron or muon with |h| < 2. 5, p. T > 50 Ge. V Two approaches (almost identical results) l |Sp. T| > 2. 5 Te. V (jets + leptons) l At least 4 jets and lepton p. T > 200 Ge. V A B C D A n=2, m = 5 -14 Te. V B n=4, m = 5 -14 Te. V C n=2, m = 8 -14 Te. V D n=7, m = 8 -14 Te. V
ATLAS Black Holes 2 l l Reconstruct the visible mass of the black hole from all objects and MET Very dramatic signature + large signal cross-sections
ATLAS Black Holes 3 l Investigated Event Shapes l l Do give separation with background Very different for different parameters
ATLAS Black Holes 4 l Discovery potential l S/ B > 5 S > 10 Discovery possible ranging from l l Few pb for 5 Te. V ~1 fb for 9 Te. V
Summary l l l Signatures from Gravitons and Black Holes would be dramatic compelling signatures RS Gravitons should be observable ~5 Te. V range and quickly observable for ~1 Te. V masses Black holes could be seen to very high masses (8 -9 Te. V) 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 l l Gravitons couple to momentum tensor (contribute to most SM processes) Monojets Single Vector Boson production Dilepton/Dijet/Diboson production l l As resonance q As non-resonant modification to SM crosssection q q g g g q G g G q V q q G q V G l q 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 l Systematics Theory l l l QCD and EW Scale – 13 -17% PDF – 7% Systematics Experiment l l l 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 – ideal Dotted – long term alignment Dashed – “first alignment”
Diphoton Backup I Diphoton production Dijet Drell-Yan Photon + Jet
Diphoton Backup II
Diphoton Backup III
Diphoton Backup 4 Hard Process Scale PDF Uncertainties
Dijet Backup
Sezen Sekmen SUSY 07
Sezen Sekmen SUSY 07
CMS Black Hole Backup PDF Uncertainties : Uncertainty on Signficance ~ 12% Sphericity
Black Hole Backup CMS TDR -2006
Atlas Black Hole backup l As a function of black hole threshold
- Slides: 35