040617 GALLAS E talk

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Published on September 29, 2007

Author: Freedom

Source: authorstream.com

Searches for Extra Dimensions and Heavy di-lepton Resonances at D0:  Searches for Extra Dimensions and Heavy di-lepton Resonances at D0 Elizabeth Gallas Fermi National Accelerator Laboratory Computing Division 12th International Conference on Supersymmetry and Unification of Fundamental Interactions June 17-23, 2004 Epochal Tsukuba, Tsukuba, Japan. Outline:  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 – TEVATRON Run 2 Upgrade:  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 DØ Run 2a Upgrade:  DØ Run 2a Upgrade Solenoid (2T) 4-layer Silicon Vertex and 16-layer Fiber Trackers Muon forward chamber (|h|<2 ), shielding New preshower, upgrade Calorimeter electronics Upgrade to Trigger and DAQ system What can Extra Dimensions do for you ?:  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 ! Large Extra Dimensions (LED) in the ADD Model:  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 n3 ! LED Tevatron Search Modes:  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 Virtual Graviton Exchange:  Virtual Graviton Exchange The predicted cross section is described by: where hg = F/MS4 == (in TeV-4) describes strength of gravity in the presence of LED and F is a dimensionless parameter ~ 1 which depends on the formalism (for the effective Lagrangian): GRW: F = 1 HLZ: F = log(Ms2/M2), n =2 F = 2/(n-2), n > 2 Hewett F = 2l/p, l=±1 Experimentally, the process is defined by the invariant mass of the di-boson or di-leptons (M) cosine of the scattering angle, * (|cos *|). SM term interference term direct gravity term Search for ED in ee/ channel:  Search for ED in ee/ channel Dataset 200 pb-1 Use di-EM objects both ee and  Selections Two 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 Bkg Highest mass Drell-Yan event:  Highest mass Drell-Yan event Invariant mass 475 GeV/c2, cos θ* = 0.01 di-EM Mass,Cos θ* distributions:  di-EM Mass,Cos θ* distributions Uncertainties in G for di-EM sample:  Uncertainties: Uncertainties in G for di-EM sample LED: :  LED:  MS > 880 GeV (95% CL) Run 2 Preliminary Luminosity = 100 pb-1 Select events with 2 muons PT> 15 GeV M > 50 GeV Summary: Limits on LED MS for various formalisms F:  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/M4S 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 Dedicated ee Search for ‘longitudinal’ Extra Dimensions:  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  Dedicated ee Search for TeV-1 Dimensions (DDG):  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 Z Limits from ee: SM, E6:  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 Z’: :  Z’:  No evidence: Set limits M(Z’) > 610 GeV Run 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 Summary:  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

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