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Searches for New Phenomena With the D  Detector Nick Hadley The University of Maryland

Searches for New Phenomena With the D  Detector Nick Hadley The University of Maryland. Outline. Detector and Accelerator Status Search for Extra Dimensions Large Extra Dimensions Tev-1 Extra Dimensions Randall Sundrum Model Search for SUSY Trilepton Search. Tevatron Run II Status.

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Searches for New Phenomena With the D  Detector Nick Hadley The University of Maryland

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  1. Searches for New PhenomenaWith the D Detector Nick Hadley The University of Maryland

  2. Outline • Detector and Accelerator Status • Search for Extra Dimensions • Large Extra Dimensions • Tev-1 Extra Dimensions • Randall Sundrum Model • Search for SUSY • Trilepton Search

  3. Tevatron Run II Status • Significant upgrade of Detectors and accelerator • New Main Injector and antiproton recycler • Higher energy 1.8 TeV → 1.96 TeV • Shorter bunch crossing time (396 ns) and more bunches (6x6 → 36 x 36) • Projected Integrated Luminosity per experiment: 2 fb-1 by 2006, 8 fb-1 by 2009 • Highest L to date 1.03 x 1032 cm-2 s-1 • Nearly 0.5 fb-1 on tape to date • Data taking efficiency 85%-90%

  4. Fy2004 Tevatron Performance Goal Exceeded 106% of Design Goal at 96% through the Fiscal Year

  5. AØ: The High Rise FØ: The RF BØ: CDF EØ: This Space For Rent CØ: Future BTeV DØ:

  6. D Detector • 2T Solenoid • Silicon detector • Fiber Tracker • Upgraded Muon system • Upgraded DAQ/trigger

  7. Integrated Luminosity Integrated Luminosity more than doubled in the last 12 months

  8. ADD Model: “Eliminates” the hierarchy problem by stating that physics ends at a TeV scale Only gravity lives in the “bulk” space Size of ED’s (n=2-7) between ~100 mm and ~1 fm Doesn’t explain how to make ED large TeV-1 Scenario: 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: • 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

  9. ADD Model: Winding modes with energy spacing ~1/r, i.e. 1 meV – 100 MeV Can’t resolve these modes – they appear as continuous spectrum TeV-1 Scenario: Winding modes 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: • “Particle in a box” with a special metric • Energy eigenvalues are given by zeroes of Bessel function J1 • Light modes might be accessible at colliders E ~MGUT E ~MPl … … Mi Mi M0 M1

  10. 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

  11. Intermediate-size extra dimensions with TeV-1 radius Introduced by Antoniadis [PL B246, 377 (1990)] in the string theory context; used by Dienes, Dudas, Gherghetta [PL B436, 55 (1998)] to allow for low-energy unification Expect ZKK, WKK, gKK resonances at the LHC energies At lower energies, can study effects of virtual exchange of the Kaluza-Klein modes of vector bosons Current indirect constraints come from precision EW measurements: 1/r ~ 6 TeV No dedicated experimental searches at colliders to date TeV-1 Extra Dimensions Antoniadis, Benaklis, Quiros [PL B460, 176 (1999)] ZKK

  12. x5 SM brane Randall-Sundrum Scenario • Randall-Sundrum (RS) scenario[PRL 83, 3370 (1999); PRL 83, 4690 (1999)] • + brane – no low energy effects • +– branes – TeV Kaluza-Klein modes of graviton • Low energy effects are given by Lp; for krc ~ 10, Lp ~ 1 TeV and the hierarchy problem is solved naturally G Planck brane

  13. RS Model Parameters • Need only two parameters to define the model: k and rc • Equivalent set of parameters: • The mass of the first KK mode, M1 • Dimensionless coupling • To avoid fine-tuning and non-perturbative regime, coupling can’t be too large or too small • 0.01 ≤ ≤ 0.10 is the expected range • Gravitons are narrow Expected Run II sensitivity in DY Drell-Yan at the LHC M1 Davoudiasl, Hewett, Rizzo[PRD 63,075004 (2001)]

  14. Search Strategy • 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 photon • 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.

  15. Example: diEM Mass

  16. No excess seen • No excess of di-lepton or di-photon events is seen. (Typical luminosities 200 pb-1) • Set limits…

  17. In the case of pair production via virtual graviton, gravity effects interfere with the SM (e.g., l+l- at hadron colliders): Therefore, production cross section has three terms: SM, interference, and direct gravity effects: 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 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 Virtual Graviton Effects

  18. Combine diphotons and dielectrons into “di-EM objects” to maximize efficiency High-mass, low |cosq*| tail is a characteristic signature of LED Cheung, Landsberg [PRD 62, 076003 (2000)] Sensitivity is dominated by the diphoton channel (2  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)]: These are the most stringent constraints on large ED for n > 2 to date, among all experiments, (tabletop gravity n= 2, M>1.7TeV, r < 160m) DØ Search for Virtual Graviton Effects 200 pb-1 rmax MS = 1 TeVn=6

  19. DØ Search for Virtual Graviton EffectsDi-muon channel • Preliminary Di-muon results just approved • 250 pb-1, no deviations from SM seen.

  20. Interesting Candidate Events • While the DØ data are consistent with the SM, the two highest-mass candidates have low values of cosq* typical of ED signal: Event Callas: Mee = 475 GeV, cosh* = 0.01 Mgg = 436 GeV, cosh* = 0.03

  21. While the Tevatron sensitivity is inferior to the indirect limit, it’s searching for effects of virtual KK modes, as they are complementary to those in the EW data DØ has performed the first dedicated search of this kind in the dielectron channel based on 200 pb-1 of Run II data (ZKK, gKK  e+e-) The 2D-technique similar to the search for ADD effects in the virtual exchange yields the best sensitivity in the DY production Cheung, Landsberg [PRD 65, 076003 (2002)] Data agree with the SM predictions, which resulted in the following limit on their size: 1/r > 1.13 TeV @ 95% CL r < 1.75 x 10-19 m First Dedicated Search for TeV-1 Extra Dimensions 200 pb-1, e+e- Event Callas Interference effect 1/r = 0.8 TeV

  22. 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 • “Naturally” combine two channels by NOT distinguishing between electrons and photons! • Search window size has been optimized to yield maximum signal significance • Analysis technique is similar to CDF’s; acceptance is higher due to forward photons

  23. 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 CDF gg Hot! 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

  24. Extra Dimension Summary • No di-electron, di-muon or di-photon excess seen • Set LED, TeV-1 and RS limits • Z’ limit • 780 GeV at 95% CL (ee 200 pb-1) • 680 GeV at 95% CL ( 250 pb-1) • Check www-d0.fnal.gov/Run2Physics/WWW/results/NP/np.htmfor updates and details (D Searches public results page)

  25. SUSY • Numerous results including searches for RPV SUSY. • All limits (unfortunately) • See (same page as before) for details www-d0.fnal.gov/Run2Physics/WWW/results/NP/np.htm • One example: trilepton search

  26. Trilepton Chargino and Neutralino Search • Associated production of lightest chargino and next to lightest neutralino in tri-lepton channels • Results interpreted in mSUGRA model • Tan  = 3,  > 0, A0 = 0 • Four channels combine overlaps removed • Two electrons + third lepton (249 pb-1) • Electron + muon + third lepton (221 pb-1) • Two muons + third lepton (235 pb-1) • Two like sign muons (147 pb-1) • Third lepton = isolated track (for higher efficiency)

  27. Trilepton Chargino and Neutralino Search (cont) • No excess of events seen in any single channel or in all channels combined • see 3 events total • expected background = 2.93 events) • Set limits… • Significant improvement over Run 1 results • Will reach mSUGRA interesting region with about 25% more data (have x2 on tape)

  28. Trilepton Chargino and Neutralino Search (cont)

  29. Summary • D is actively searching for new phenomena and particles in our data. Techniques are maturing, sensitivities substantially exceed old bounds • Detector and accelerator performing well. • Only limits so far… • Let us know about your favorite model • We’re glad to look…

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