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Search for Large Extra Dimensions at the Tevatron Bob Olivier, LPNHE Paris XXXVI ème Rencontre de Moriond 17 - 24 Mars 2001 1 Search for Large Extra Dimensions.

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Presentation on theme: "Search for Large Extra Dimensions at the Tevatron Bob Olivier, LPNHE Paris XXXVI ème Rencontre de Moriond 17 - 24 Mars 2001 1 Search for Large Extra Dimensions."— Presentation transcript:

1 Search for Large Extra Dimensions at the Tevatron Bob Olivier, LPNHE Paris XXXVI ème Rencontre de Moriond Mars Search for Large Extra Dimensions at the Tevatron Bob Olivier LPNHE - Paris XXXVI ème Rencontre de Moriond Mars 2001 On behalf of the CDF and D0 collaborations

2 Search for Large Extra Dimensions at the Tevatron Bob Olivier, LPNHE Paris XXXVI ème Rencontre de Moriond Mars Signatures for Large Extra Dimensions at the Tevatron Real Gravitons z Single Energetic jet z Missing Energy from the graviton G KK g q q g g g z Single Vector Boson z Missing Energy from the graviton G KK V V V V Virtual Gravitons z Fermion or Vector Boson pairs V V G KK f f f f  CDF and D0 analysis on going...  New Results from D0 !

3 Search for Large Extra Dimensions at the Tevatron Bob Olivier, LPNHE Paris XXXVI ème Rencontre de Moriond Mars Effects of Virtual Graviton Exchange at the Tevatron In models with Large Extra Dimensions, Kaluza-Klein gravitons can modify difermion/diphoton production in collisions :  interference between SM and gravity contribution (e.g., l + l - production): z : difermion/diphoton production angle z M: difermion/diphoton mass z n: number of large extra dimensions z M S : cut-off scale for KK-diagrams  search for deviations in distributions for and M

4 Search for Large Extra Dimensions at the Tevatron Bob Olivier, LPNHE Paris XXXVI ème Rencontre de Moriond Mars Search Strategy at DØ Based on Cheung/Landsberg PRD 62, (2000) DØ detector does not have a central magnetic field, hence cannot measure electric charge of electrons  use |cos  * | Dimuon mass resolution at high mass is poor  use dielectrons, do not use dimuons EM objects not separated into electrons and photons Low background expected at high mass : use loose EM-ID cuts  maximize EM efficiencies use EM cluster direction to pick vertex  better and M resolutions

5 Search for Large Extra Dimensions at the Tevatron Bob Olivier, LPNHE Paris XXXVI ème Rencontre de Moriond Mars Data Selection and Efficiency Use entire Run I luminosity, low-threshold, di-EM triggers:  Ldt = 127  6 pb -1 Offline criteria: z Exactly 2 EM clusters, E T >5 GeV, passing basic EM ID criteria z No other kinematic restrictions in the analysis, since (M, ) define the process completely Resulting data sample contains 1250 events Overall Signal efficiency: 79  2% 10,711EM ID 1,250ET > 45 GeV 30,585Acceptance 36,409E T > 25 GeV 82,425=2 EM  2 EM 82,947Quality criteria 87,542Starting sample # of eventsCriterion (79  2)% Eff. per event (99.8  0.1)% Event quality (98  1)% MET < 25 GeV (87  2)% EM ID Signal EfficiencyCriterion

6 Search for Large Extra Dimensions at the Tevatron Bob Olivier, LPNHE Paris XXXVI ème Rencontre de Moriond Mars Backgrounds SM backgrounds in the MC: – Drell-Yan (e-pairs) – qq   (gg   is negligible  not included) W+j/ ,WW, Top, Z negligible , fb/bin M(di-EM), GeV Total SM background qq   gg   At high mass, SM background dominated by qq   Instrumental background: QCD induced jj/j  “  ” (jet fake a  [Landsberg & Matchev, PRD 62, (2000)]

7 Search for Large Extra Dimensions at the Tevatron Bob Olivier, LPNHE Paris XXXVI ème Rencontre de Moriond Mars MC Description of Data and Systematics Kinematic distributions are well described by the sum of SM and instrumental backgrounds Following systematic uncertainties on differential cross sections were taken into account: Instrumental background (uncertain to 25%) 12%Overall 3%Efficiency 4%  Ldt 5%Choice of PDF 10%K-factor UncertaintSource

8 Search for Large Extra Dimensions at the Tevatron Bob Olivier, LPNHE Paris XXXVI ème Rencontre de Moriond Mars Observe good agreement in > 500 GeV > 550 GeV N 1.00<0.1> 600 GeV > 450 GeV > 400 GeV > 350 GeV > 300 GeV > 250 GeV > 200 GeV > 150 GeV > 100 GeV PBMass cutoff

9 Search for Large Extra Dimensions at the Tevatron Bob Olivier, LPNHE Paris XXXVI ème Rencontre de Moriond Mars Instrumental background Mass and Angular Distributions

10 Search for Large Extra Dimensions at the Tevatron Bob Olivier, LPNHE Paris XXXVI ème Rencontre de Moriond Mars Monte Carlo for Signal and Background SM 44 88 M S = 1 TeV n=4

11 Search for Large Extra Dimensions at the Tevatron Bob Olivier, LPNHE Paris XXXVI ème Rencontre de Moriond Mars DØ Results in Di-EM Channels High mass and small |cos  | are characteristic signatures of LED 2-dimensional analysis resolves LED from high-mass and large |cos  | tail from QCD diphotons No excess seen at high mass, where LED signal is expected signal background

12 Search for Large Extra Dimensions at the Tevatron Bob Olivier, LPNHE Paris XXXVI ème Rencontre de Moriond Mars DØ Limits on Large Extra Dimensions No evidence for SM deviations in D0 data Measured fitted with parametrized contributions from large extra dimensions Fit result consistent with 0, extracts limits at 95% C.L. Complementary to those from LEP2 ( TeV), probing different range of energies CDF pursues similar dilepton and diphoton analyses (similar sensibility expected) Combined Tevatron limits are expected to be the most restrictive to date PRL 86, 1156 (2001) Sensitivity is limited by statistics; reach in terms of M S will double in Run-2a (2 fb -1 ) and triple in Run-2b (20 fb -1 )

13 Search for Large Extra Dimensions at the Tevatron Bob Olivier, LPNHE Paris XXXVI ème Rencontre de Moriond Mars Highest-Mass Candidate Parameters of the candidate event of highest mass: Event with highest mass observed in Run I M(  ) = 574 GeV cos  * = photons with Et = 81 GeV Met= 15 GeV GeV GeV  15GeV3.6 cm N jet cos  * M 22 11 ET2ET2 ET1ET1 TypeME T Z vtx EventRun

14 Search for Large Extra Dimensions at the Tevatron Bob Olivier, LPNHE Paris XXXVI ème Rencontre de Moriond Mars Monojet Signatures n =2, M S = 1 TeV,  s= 1.8 TeV CDF sensitivity study in progress Typical process: Single jet Missing energy from the graviton

15 Search for Large Extra Dimensions at the Tevatron Bob Olivier, LPNHE Paris XXXVI ème Rencontre de Moriond Mars Real Graviton Signature (CDF) Sensitivity on transverse mass (jet, Etmiss) for different values of n CDF analysis on going

16 Search for Large Extra Dimensions at the Tevatron Bob Olivier, LPNHE Paris XXXVI ème Rencontre de Moriond Mars Summary DO has searched for contributions from virtual graviton exchange in the context of “large” extra spatial dimensions. On the basis of the production of massive e-pairs and di- photons, such a scale, must be higher than ~ 1 TeV More studies are being pursued at both DO and CDF, both on virtual-graviton exchange as well as real graviton (mono-jet) production. Expected spring Run I limits are most stringent up to date Run II will be sensitive to scales of 3-4 TeV The LHC will be able to access effective “Planck” scales of 10 TeV

17 Search for Large Extra Dimensions at the Tevatron Bob Olivier, LPNHE Paris XXXVI ème Rencontre de Moriond Mars Run II ! Tevatron Run II has started March One of the first Run II events in D0: A lot of “missing energy”…  new physics ???


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