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Search for Extra-Dimensions at D0

Search for Extra-Dimensions at D0. Tevatron and D0 status Extra Dimensions Large ED Tev-1 ED Randall Sundrum Model. M. Jaffr é LAL Orsay for the D0 Collaboration. Tevatron RunII Status. New Main Injector: 150 GeV New Recycler Higher Energy (1.96TeV)

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Search for Extra-Dimensions at D0

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  1. Search for Extra-Dimensions at D0 • Tevatron and D0 status • Extra Dimensions • Large ED • Tev-1 ED • Randall Sundrum Model M. Jaffré LAL Orsay for the D0 Collaboration

  2. Tevatron RunII Status • New Main Injector: 150 GeV • New Recycler • Higher Energy (1.96TeV) • Higher luminosity(36x36 bunches) Design “Run IIa” : 0.8x1032 cm-2s-1 “Run IIb” : 2-4x1032 cm-2s-1 • Upgrades to come Slip stacking end 04 Electron cooling end 05 ? Stacktail upgrade end 06 ? New helix beam separation end 06 ? • Projected Integrated lumi. / expt: 2006 2fb-1 2009 8fb-1 1.02 1032 cm-2 s-1 Run I record M.Jaffré EuroGDR Nov 24, 2004 2002 2003 2004

  3. SMT SMT SMT DØ Run II • Solenoid (2T) • 4-layer Silicon Vertex (barrels and disks) • 16-layer Fiber Trackers • Muon forward chamber (||<2 ), shielding • New preshower, upgrade Calorimeter electronics • Upgrade to Trigger and DAQ system For Run IIb (Fall 05) • Silicon layer 0 • Trigger upgrade M.Jaffré EuroGDR Nov 24, 2004

  4. Half A Femtobarn of Data! D0 analysis Integrated Luminosity more than doubled in the last 12 months Efficiency >80% M.Jaffré EuroGDR Nov 24, 2004

  5. Why ED ? • String theory is the only currently known way to incorporate gravity in Quantun Mechanics. • ED come « naturally » with string theory (n=6 or 7) • In short, models with ED try to address the problem of the huge hierarchy between EW and Planck scales. • …. • These ideas can be tested at existing and nearly existing colliders M.Jaffré EuroGDR Nov 24, 2004

  6. ADD Model: Arkani-Hamed,Dimopoulos,Dvali Phys Lett B429 (98) SM particles and gauge bosons are confined in D3-brane Only gravity propagates in n spatial ED Gauss law MPl (apparent 4D Planck Scale) Ms (fundamental Planck Scale) Size of ED’s (n=2-7) between ~100 mm and ~1 fm TeV-1 Scenario: Dienes,Dudas,Gherghetta Nucl Phys B537 (99) Lowers GUT scale by changing the running of the couplings Only gauge bosons (g/g/W/Z) propagate in a single ED; gravity is not in the picture Size of the ED ~1 TeV-1 or ~10-19 m G x5 Planck brane SM brane Models of Extra Dimensions RS Model: Randull,Sundrum Phys Rev Lett 83 (99) • A rigorous solution to the hierarchy problem via localization of gravity • Gravitons (and possibly other particles) propagate in a single ED, w/ special metric • Size of this ED as small as ~1/MPl or ~10-35 m M2Pl MSn+2 x Rcn M.Jaffré EuroGDR Nov 24, 2004

  7. ADD Model: KK excitations with energy spacing ~1/r, i.e. 1 meV – 100 MeV Can’t resolve these modes – they appear as continuous spectrum TeV-1 Scenario: KK excitations with nearly equal energy spacing ~1/r, i.e. ~TeV Can excite individual modes at colliders or look for indirect effects E ~1 TeV Kaluza-Klein Spectrum RS Model: • Coupling of graviton to SM fields is : k/MPl [0.01-0.1] • Light modes might be accessible at colliders • Model characterized by M1 and k/MPl E ~MGUT E ~MPl … … Mi Mi M0 M1 M.Jaffré EuroGDR Nov 24, 2004

  8. Real Graviton Emission Monojets at hadron colliders g g g q GKK GKK g q Single VB at hadron or e+e- colliders V GKK V V GKK GKK GKK V Virtual Graviton Emission Fermion or VB pairs at hadron or e+e- colliders f f V GKK GKK f f V Collider Signatures: Large Extra Dimensions • Kaluza-Klein gravitons couple to the energy-momentum tensor, and therefore contribute to most of the SM processes • For Feynman rules for GKK see: • Han, Lykken, Zhang, [PRD 59, 105006 (1999)] • Giudice, Rattazzi, Wells, [NP B544, 3 (1999)] • Since graviton can propagate in the bulk, energy and momentum are not conserved in the GKK emission from the point of view of our 3+1 space-time • Depending on whether the GKK leaves our world or remains virtual, the collider signatures include single photons/Z/jets with missing ET or fermion/vector boson pair production • Graviton emission: direct sensitivity to the fundamental Planck scale MD • Virtual effects: sensitive to the ultraviolet cutoff MS, expected to be ~MD (and likely < MD) • The two processes are complementary M.Jaffré EuroGDR Nov 24, 2004

  9. Search for Monojets • Very challenging because of instrumental background from MET mismeasurement, cosmics. • Irreducible Physics background from Z() + jet(s). • Special trigger for Physics with jets and MET since spring 03 : MHT =  pT(jets) > 30 GeV/c  85 pb-1 (april-august 2003) • Calorimeter Data Quality is very important for Jet+Met analyses, since most calorimeter problems (hot cells, noise...) will increase the MET tail distribution • Offline: to fight mixvertexing and cosmics : jets have associated tracks originating from primary vertex M.Jaffré EuroGDR Nov 24, 2004

  10. Search for Monojets Final Selection : • Leading jet pT > 150 GeV • Isolated electron and muon veto • MET > 150 GeV • No extra jet with pT > 50 GeV • MET separated from any jet by  30 Signal simulation = Pythia + Lykken-Matchev code (~ 5% signal efficiency) Largest uncertainty is from JES and have already been much improved With 85 pb-1 better than D0 Run I still below CDF Run I QCD bckg N=6 MD = 0.7 TeV before MET cut Mostly Z()+jets M.Jaffré EuroGDR Nov 24, 2004

  11. Search for effects in high mass dilepton, diphoton events • ED processes predict high mass di-lepton and/or di-photon events • Study High Pt di-electron, di-muon, and di-photon mass spectra • Main backgrounds: Drell Yan and QCD jet events where jets fake leptons and photons • Drell-Yan: shape vs mass known from theory • QCD: get shape from events that (just) fail particle ID cuts. • Normalize DY and QCD to “low mass” events (typically about 50 GeV to 120 GeV) includes Z. M.Jaffré EuroGDR Nov 24, 2004

  12. In the case of pair production via virtual graviton, gravity effects interfere with the SM (e.g., l+l- at hadron colliders): Therefore, production Xsection has three terms: SM, interference + direct gravity effects: where G= F/MS4 Hewett:F = 2l/p with l = ± 1 GRW: F = 1 HLZ:F = log(MS2/s) for n = 2 F = 2/(n-2) for n > 2 The sum in KK states is divergent in the effective theory, so in order to calculate the cross sections, an explicit cut-off is required An expected value of the cut-off MS MD,as this is the scale at which the effective theory needs to be used to calculate production. There are three major conventions on how to write the effective Lagrangian: Hewett [PRL 82, 4765 (1999)] Giudice, Rattazzi, Wells [NP B544, 3 (1999); revised version, hep-ph/9811291] Han, Lykken, Zhang [PRD 59, 105006 (1999); revised version, hep-ph/9811350] Fortunately all three conventions turned out to be equivalent and only the definitions of MS are different LED Virtual Graviton Effects cos = |cosine| of scattering angle in c.o.m frame M.Jaffré EuroGDR Nov 24, 2004

  13. diEM Selection • DiEM = ee +  2 EM objects ET > 25 GeV Track isolation CC : ||1.1; EC : 1.5<||2.4 Overall ID efficiency 851% / EM 200 pb-1 Signal G=0.6 TeV-4 DY + Direct  + QCD QCD M.Jaffré EuroGDR Nov 24, 2004

  14. Combine diphotons and dielectrons into “di-EM objects” to maximize efficiency Sensitivity is dominated by the diphoton channel (spin 2 graviton  1 + 1) Data agree well with the SM predictions; proceed with setting limits on large ED: alone or in combination with published Run I result [PRL 86, 1156 (2001)]: G95% = 0.292 TeV-4 Translated into the following mass limits RunII result Combined RunI + RunII result These are the most stringent constraints on large ED for n > 2 to date, among all the experiments Search for LED in diEM channel See these 2 evts in next slide 200 pb-1 rmax MS = 1 TeVn=6 M.Jaffré EuroGDR Nov 24, 2004

  15. Interesting Candidate Events Mee = 475 GeV, cos* = 0.01 Mgg = 436 GeV, cos* = 0.03 M.Jaffré EuroGDR Nov 24, 2004

  16. Search for LED in diMuon channel • 2 ’s with pT > 15 GeV • isolated, ||<2.0 • for M > 300 GeV:Nexp = 6.40.8 and Nobs = 5 • Systematics: ~ 13% Fit the 2D distributions as for diEM G95% = 0.72 TeV-4 (Bayesian) 250pb-1 M.Jaffré EuroGDR Nov 24, 2004

  17. Search for TeV-1 ED • Di-electron channel 200 pb-1 • QCD fake bckg much reduced compare to diEM • Apply the same 2D-technique as for LED search. Z/ KK states effects parameterized by C=2/3MC2 • Data agree with the SM predictions, which resulted in the following limit on their size: MC > 1.12 TeV @ 95% CL r < 1.75 x 10-19 m • Well below indirect contraints from EW measurement (6 TeV) CC-CC signal for C = 5 TeV-2 Note the negative interference M.Jaffré EuroGDR Nov 24, 2004

  18. DØ Search for RS Gravitons • Analysis based on 200 pb-1 of e+e- and gg data – the same data set as used for searches for LED • Search window size has been optimized to yield maximum signal significance;\ • G(1) is narrow compare to the mass resolution 300 GeV RS signal QCD DY+direct + QCD M.Jaffré EuroGDR Nov 24, 2004

  19. DØ Limits in the ee+gg Channel The tightest limits on RS gravitonsto date Assume fixed K-factor of 1.3 for the signal Masses up to 780 GeV are excluded for k/MPl = 0.1 DØ Run II Preliminary, 200 pb-1 Already better limits than the sensitivity for Run II, as predicted by theorists! DØ Run II Preliminary, 200 pb-1 M.Jaffré EuroGDR Nov 24, 2004

  20. Conclusion - Outlook • The data agree well with the Standard Model • New limits from D0 on Extra Dimensions • Twice the statistics is available, … more will come soon • Expect to increase the mass limits for LED models up to 2TeV before the LHC startup M.Jaffré EuroGDR Nov 24, 2004

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