June_2004 E. Gallas - SUSY 2004 1

Searches for Extra Dimensions and

Heavy di-lepton Resonances at D0

Elizabeth Gallas Fermi National Accelerator Laboratory

Computing Division

12th International Conferenceon Supersymmetryand Unification of Fundamental InteractionsJune 17-23, 2004Epochal Tsukuba, Tsukuba, Japan.

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Outline• 3-Space / Time:

– Fermilab Tevatron with Experiment DØ / mid Run 2 • What can Extra Dimensions (ED) do for you ?• Phenomenology (of interest for pp colliders)

– 2 particular ED models• Large Extra Dimensions

– ADD (Arkani-Hamed, Dimopoulos, Dvali)• TeV-1 ‘longitudinal’ Extra Dimensions

– DDG (Dienes, Dudas, Gherghetta)– DØ: A window into ‘Extra Dimensions’ (ED)

• DØ: Lepton/Photon Final state searches for :– Large Extra Dimensions (ED)– TeV-1 ‘longitudinal’ Extra Dimensions– Z’ boson

• Summary and Conclusions

–

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Chicago

Tevatron

Main Injector & Recycler

DØCDF

p source

TEVATRON Run 2 Upgrade

• New Main Injector : 150 GeV– Store protons, shoot to

target for anti-proton production

• New recycler :– Magnet storage ring for anti-

proton

• Higher energy:– 1.96 TeV vs 1.8 TeV– Higher cross sections

(30 % for the SUSY)

• Higher antiproton intensity:– 6x6 36x36 bunches

(3.5 μs 396 ns)– Higher luminosity

• Run 1 : 2x1031 cm-2s-1

• Run 2 : 2x1032 cm-2s-1

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SMTSMT

SMT

DØ Run 2a UpgradeSolenoid (2T)

4-layer Silicon Vertex and 16-layer Fiber Trackers

Muon forward chamber (||<2 ), shielding

New preshower, upgrade Calorimeter electronics

Upgrade to Trigger and DAQ system

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What can Extra Dimensions do for you ?

…proposals dating at least back to 1920’s…

• Recent renaissance in the theory proposes:– unite all known forces (including gravity)

• known particles, electroweak and strong interactions– confined to a ‘brane’ - a hypersurface in the “bulk” of 4+n Dim

• gravity appears weak – diluted in extra dimensions.

– There is no “desert”– Offers alternative to the “hierarchy

problem”• only one important scale in nature --

may be accessible at Tevatron and LHC energies

– Lends practical aspects to string theory…

it’s not just a beautiful idea… we can test it !

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Large Extra Dimensions (LED)in the ADD Model

• ADD (Arkani-Hamed, Dimopoulos, Dvali) model assumes:– n Extra Dimensions of size R– SM particles and interactions are confined to 4D-world (brane)– Gravity propagates in 4+n Dimensional space

• Gravity appears weak – diluted in extra dimensions

– In this formulation:

• where MPl (apparent 4D Planck Scale):• Ms (fundamental Planck Scale) is brought to

the TeV range

• Constraints (cosmology, tabletop expts):– Extra dimensions ‘compactified’ (RC < 1 mm)– require n>1 (g forces at large distances)Collider experiments – only probe for ED for n3 !

nc

nSPl RMM 22

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LED Tevatron Search Modes

• Direct Searches (graviton escapes the brane)– look for JET recoiling against missing ET (next talk)

• Indirect Searches (this talk)– virtual graviton - contributions to l+l-, production

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Virtual Graviton Exchange

• The predicted cross section is described by:

where g = F/MS4 == (in TeV-4)

describes strength of gravity in the presence of LEDand F is a dimensionless parameter ~ 1 which depends on the formalism (for the effective Lagrangian):

GRW: F = 1HLZ: F = log(Ms

2/M2), n =2 F = 2/(n-2), n > 2Hewett F = 2/, =±1

• Experimentally, the process is defined by the – invariant mass of the di-boson or di-leptons (M)– cosine of the scattering angle, * (|cos *|).

2int

2

cosM GKKGSM fffdd

d

•SM term•interference term•direct gravity term

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Search for ED in ee/ channel

• Dataset 200 pb-1

• Use di-EM objects– both ee and

• SelectionsTwo EM with Et > 25 GeV

with tight quality cuts

Fiducial requirements:• central EM objects:

|eta| < 1.1

• central/forward objects:1.5 < |eta| < 2.4

LED signal MC for g =0.6

fakes

Bkg

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Highest mass Drell-Yan event

Invariant mass 475 GeV/c2, cos θ* = 0.01

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di-EM Mass,Cos θ* distributions

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• Uncertainties:

Uncertainties in G for di-EM sample

Source of Systematic Uncertainty

K-factor (NLO effects) 10%

Choice of p.d.f. 5%

Normalization x eff iciency 2%

ET dependence of eff iciency 5%

Total 12%

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LED: LED in at DØ -

MS > 880 GeV (95% CL)Run 2 Preliminary

•Luminosity = 100 pb-1

•Select events with2 muons PT> 15 GeVM > 50 GeV

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Summary: Limits on LED MS

for various formalisms F• No evidence for signatures in excess of high-mass dielectron,

diphoton or dimuon events over SM expectation, from coupling to Kaluza-Klein gravitons

• Fit (di-EM Mass,Cos θ*) distribution – Single parameter for ED effects: ηG = F/M4

S

• Translate ηG limits to 95% CL lower limits on Planck scale MS , in TeV, using different formalisms for F

• DiEM limits - combine Run I & Run 2 – best limits on LED to date• Di limits for Run 2 with more statistics -- in preparation

GRW HLZ for n=: 2 3 4 5 6 7

Hewett

diEM 1.43 1.67 1.70 1.43 1.29 1.20 1.14 1.28

diMU 0.88 0.68 0.95 0.79 0.72 0.67 0.63 0.71

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Dedicated ee Search for ‘longitudinal’ Extra Dimensions

• Another ED model (TeV-1 “longitudinal” EDs):– proposed by Dienes, Dudas, and Gherghetta (DDG)

– Fermions confined to 4D

– but SM gauge bosons propagate in TeV-1 ED of size:

R = 1/MC

– Predicts Kaluza-Klein states of gauge bosons (KK, WKK, ZKK, gKK)

• produced directly (with sufficient energy)

• produced indirectly (virtual exchange of KK modes)

• Lepton pair production cross section depends on

C = 2 / 3 MC2, where MC = ‘compactification’ scale of TeV-1 ED

• This analysis:– look for virtual exchanges of KK excitations of the Z and

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Jet mis-ID signal

C=5TeV-2

SM + fakes

Dedicated ee Search for TeV-1 Dimensions (DDG)

Predicts strong negative interference effects unlike LED discussed before

Use di-EM dataset (200 pb-1)– adding track match– fiducial requirements –

same as for LED analysis

Find upper limit on

C < 2.63 TeV

and thereby (lower limit):

Mc > 1.12 TeV (95% CL)

First search of this type

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Z Limits from ee: SM, E6

• Various models propose new neutral gauge bosons– SM couplings– variety of E6 GUT inspired

• Dataset 200 pb-1 – same as in ED analysis• Limits on Z’ mass in GeV/c2:SM couplings

Run I Run II 670 780

E6 couplings

ZI Zχ Zψ Zη 575 640 650 680

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Z’:

No evidence: Set limitsM(Z’) > 610 GeVRun 2 Preliminary

This is a previous result under revision with increased statistics:We used the same dimuon sample as used for LED search to look for heavy Z-like resonances

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Summary• No signal for new physics observed so far

– but some interesting events !

• New Limits from DØ: Extra Dimensions and Z’

* limits under revision with increased statistics

• improved limits on additional gauge bosons !• most sensitive collider search for ED’s to date!

– higher efficiency in widest acceptance– di-EM channels using 200 pb-1 integrated luminosity (now 300 pb-1 on tape)– first collider search for TeV-1 ‘longitudinal’ Extra Dimensions

Topic Prelim. Run 2

LED : ee and MS >1.43 TeV (Run 1&2)

LED : MS > 880 GeV *

TeV-1 ‘longitudinal’ ED: ee Mc > 1.12 TeV

Z’ : M(Z’) > 610 GeV *

Z’ : ee M(Z’) > 780 GeV