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

M.Jaffré EuroGDR Nov 24,  New Main Injector: 150 GeV  New Recycler  Higher Energy (1.96TeV)  Higher luminosity ( 36x36 bunches) Design “Run IIa” : 0.8x10 32 cm -2 s -1 “Run IIb” : 2-4x10 32 cm -2 s -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. / exp t : fb fb -1 Tevatron RunII Status cm -2 s Run I record

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

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

M.Jaffré EuroGDR Nov 24, Models of Extra Dimensions ADD Model: Arkani-Hamed,Dimopoulos,Dvali Phys Lett B429 (98) l SM particles and gauge bosons are confined in D3-brane l Only gravity propagates in n spatial ED l Gauss law M Pl (apparent 4D Planck Scale) M s (fundamental Planck Scale) Size of ED’s (n=2-7) between ~100  m and ~1 fm TeV -1 Scenario: Dienes,Dudas,Gherghetta Nucl Phys B537 (99) l Lowers GUT scale by changing the running of the couplings Only gauge bosons (g/  /W/Z) propagate in a single ED; gravity is not in the picture l Size of the ED ~1 TeV -1 or ~ m RS Model: Randull,Sundrum Phys Rev Lett 83 (99) l A rigorous solution to the hierarchy problem via localization of gravity l Gravitons (and possibly other particles) propagate in a single ED, w/ special metric l Size of this ED as small as ~1/M Pl or ~ m G Planck brane x5x5 SM brane M 2 Pl  M S n+2 x R c n

M.Jaffré EuroGDR Nov 24, Kaluza-Klein Spectrum ADD Model: l KK excitations with energy spacing ~1/r, i.e. 1 meV – 100 MeV l Can’t resolve these modes – they appear as continuous spectrum TeV -1 Scenario: l KK excitations with nearly equal energy spacing ~1/r, i.e. ~TeV l Can excite individual modes at colliders or look for indirect effects RS Model: l Coupling of graviton to SM fields is : k/M Pl [ ] l Light modes might be accessible at colliders l Model characterized by M 1 and k/M Pl ~1 TeV E ~M GUT E … M0M0 MiMi ~M Pl E … M1M1 MiMi

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

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

M.Jaffré EuroGDR Nov 24, 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 Search for Monojets N=6 M D = 0.7 TeV QCD bckg Mostly Z( )+jets before MET cut

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

M.Jaffré EuroGDR Nov 24, LED Virtual Graviton Effects l In the case of pair production via virtual graviton, gravity effects interfere with the SM (e.g., l + l - at hadron colliders): l Therefore, production Xsection has three terms: SM, interference + direct gravity effects: where  G = F/M S 4 Hewett : F = 2 /  with = ± 1 l GRW : F = 1 l HLZ: F = log(M S 2 /s) for n = 2 F = 2/(n-2) for n > 2 l 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 l An expected value of the cut-off M S  M D,as this is the scale at which the effective theory needs to be used to calculate production. l There are three major conventions on how to write the effective Lagrangian: l Hewett [PRL 82, 4765 (1999)] l Giudice, Rattazzi, Wells [NP B544, 3 (1999); revised version, hep-ph/ ] l Han, Lykken, Zhang [PRD 59, (1999); revised version, hep-ph/ ] l Fortunately all three conventions turned out to be equivalent and only the definitions of M S are different cos  = |cosine| of scattering angle in c.o.m frame

M.Jaffré EuroGDR Nov 24, diEM Selection min. MassDataBckg Signal  G =0.6 TeV pb -1 l DiEM = ee +  2 EM objects E T > 25 GeV Track isolation CC : |  |  1.1; EC : 1.5< |  |  2.4 Overall ID efficiency 85  1% / EM QCD DY + Direct  + QCD Source of systematicsUncertainty K-factor Choice of p.d.f. Luminosity x efficiency E T dependence of efficiency 10% 5% 2% 5% Total12%

M.Jaffré EuroGDR Nov 24, Search for LED in diEM channel l Combine diphotons and dielectrons into “di- EM objects” to maximize efficiency l Sensitivity is dominated by the diphoton channel (spin 2 graviton  1 + 1) l 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)]: l  G 95% = TeV -4 l Translated into the following mass limits RunII result Combined RunI + RunII result l These are the most stringent constraints on large ED for n > 2 to date, among all the experiments 200 pb -1 Hewett GRW HLZ CL)  = +1  =  1 n = 2n = 3n = 4n = 5n = 6n =  m 1.5 nm 5.7 pm 0.2 pm 21 fm4.2 fm r max M S = 1 TeV n=6 See these 2 evts in next slide

M.Jaffré EuroGDR Nov 24, Interesting Candidate Events M ee = 475 GeV, cos  * = 0.01M  = 436 GeV, cos  * = 0.03

M.Jaffré EuroGDR Nov 24,   2  ’s with p T > 15 GeV  isolated, |  |<2.0  for M  > 300 GeV: Nexp = 6.4  0.8 and Nobs = 5  Systematics: ~ 13% Search for LED in diMuon channel Hewett GRW HLZ CL) l = +1l = -1 n=2n =3 n=4n =5n=6n= Fit the 2D distributions as for diEM  G 95% = 0.72 TeV -4 (Bayesian)  G 95% = 0.72 TeV -4 (Bayesian) 250pb -1

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

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

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

M.Jaffré EuroGDR Nov 24, Conclusion - Outlook l The data agree well with the Standard Model l New limits from D0 on Extra Dimensions l Twice the statistics is available, … more will come soon l Expect to increase the mass limits for LED models up to 2TeV before the LHC startup TopicPrelim. Results LED : ee +  :  M S >1.43 TeV (GRW Run 1&2) M S > 1.09 GeV TeV -1 ‘longitudinal’ ED: ee M c > 1.12 TeV RS: ee +  M(G (1) ) > 785 GeV for k/M Pl =0.1