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A Search for New Physics in the High Mass Dilepton spectrum at CDF

A Search for New Physics in the High Mass Dilepton spectrum at CDF. Tracey Pratt, Oxford University Representing the CDF collaboration. CDF Detector Drell-Yan Signatures and New Physics Run I Limits and Run II reaches First Run II Data Near Future. pp collisions.

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A Search for New Physics in the High Mass Dilepton spectrum at CDF

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  1. A Search for New Physics in the High Mass Dilepton spectrum at CDF Tracey Pratt, Oxford University Representing the CDF collaboration • CDF Detector • Drell-Yan Signatures and New Physics • Run I Limits and Run II reaches • First Run II Data • Near Future DIS 2002, Poland

  2. pp collisions CDF at Fermilab CDF CDF Main Injector Tevatron D0 DIS 2002, Poland

  3. CDF Run I and Run II overview Run I ran from 1992 until 95 In total 110pb-1 of data was collected Centre of mass energy 1.8 TeV Since the shutdown in 1996, the Tevatron and CDF have undergone major upgrades Run II started in spring 2001 Centre of mass energy 2 TeV DIS 2002, Poland

  4. CDF detector – what’s new? Muon System Central Calorimeters Solenoid Plug Calorimeter New Partially New Old COT Time-of-Flight Silicon Tracker DIS 2002, Poland

  5. Cosmic Ray event in CDF Et 2 0 -6 4 2 0 2 4 300 200 100 0   DIS 2002, Poland

  6. Z  candidate Invariant Mass 90.0 GeV 46.3 GeV 44.8 GeV DIS 2002, Poland

  7. p q q p */ Z qq */ Z l+l- l+ l- Drell-Yan (DY) • The Drell-Yan process probes the parton distribution • functions (pdfs) of the protons at the scale Q2 = M*/ Z2 • Low background at high dilepton invariant mass • Distinctive signatures: • two oppositely charged leptons produced • have a high transverse momentum • are isolated • originate from a single interaction point • For */Z production :  q fq q(x1)q(x2) DIS 2002, Poland

  8. New Physics Searches with Dileptons Looking for deviations to the Standard Model at high invariant mass • New Gauge Bosons (Z') • Extra Dimensions • Quark-lepton Compositeness • Technicolor (T,T) DIS 2002, Poland

  9. d2/dMdy 101 100 10-1 10-2 10-3 10-4 Z and   only 0 100 200 300 400 Invariant Mass in GeV/c2 Run I Drell-Yan (DY) X88/89 CDF dileptons (ee+ 4pb-1) o 92-95 CDF dimuons (107.4pb-1) • AFB smaller than SM • AFB dips beyond 200 GeV/c2 CDF Collaboration, F.Abe et al., Phys. Rev. D 59, 052001 (1999) DIS 2002, Poland

  10. Run 1 Z' limits set limits for Z' ll, in both dielectron and dimuon channels CDF Run I (110pb-1), for MZ > 600 GeV/c2(Z ).BR(Z ->ll) is 40 fb. which excludes MZ withStandard Model coupling < 690 GeV/c2 (Phys. Rev. Lett.79: 2192-2197, 1997)) DIS 2002, Poland

  11. Run II Reaches 95 % CL Mass Reach (GeV/c2) Searches for New Gauge Bosons at Fermilab 1200 1000 800 600 400 200 0 Extrapolating from Run I, with 2 fb-1, if no candidates events in the high mass region are found, then predicted Z' mass reach could be extended to 1000 GeV/c2 with s =2.0 TeV W'e (1.8TeV) Z'll (2.0 TeV) W' dijet (1.8TeV) Z' dijet (1.8TeV) 10-2 10-1 110 102 Integrated Luminosity (fb-1) DIS 2002, Poland

  12. G G Extra Dimensions ADD model In which the fundamental Planck scale (MPl) can brought down to the TeV range, by allowing for a large compactified dimensions at the TeV scale. The SM fields are confined to a 3-D brane Massless gravitons propagate in the full 4+n dimensional space Gravitons can be detected by 1) Graviton Emission - gravitons radiate into the bulk appearing as missing energy 2) Graviton Exchange - deviations in the cross-section from SM prediction N. Arkani-Hamed et el., Phys. Lett. B 429, 263 (1998), I. Antoniadis et al., Phys Lett. B 436, 257 (1998) RS model MPl is determined by the higher-dimensional curvature rather than the size of the extra dimension. There is one additional dimension. Gravity can be localised near a brane. Kaluza-Klein states can be produced separately on resonance, and produce potentially observable spin 2 resonances. The cleanest signal for graviton resonance production is either an excess in Drell-Yan, or in the dijet channel. L.Randall and R.Sundrum, Phys. Rev. Lett. 83,3370 (1999), Phys. Rev. Lett. 83,4690 (1999) DIS 2002, Poland produce potentially observable spin 2 resonances at high energies which can be reconstructed from their decay products.

  13. q l- /Z0 q G q l+ q l- l- g G l+ l+ g Extra Dimensions Graviton Exchange - modifies the rate and angular distribution of high-mass Drell-Yan events • The SM exchange of a  or Z boson interferes with the exchange of a graviton + • There is also a gluon-gluon initiated graviton exchange process which has no SM analogue. + DIS 2002, Poland

  14. 10 -2 10 -4 10 –6 10 -8 700 GeV KK graviton K/MPl d/dM (pb/GeV) Run I 1 0.7 0.5 0.3 0.2 0.1 RS model 200 400 600 800 1000 1200 Mll (GeV) SM prediction Quantum Gravity Model for Ms values CDF results for dimuon samples ADD model and RS model limits Mll (GeV) Compactification scales R-1 (TeV)  0.9 Run 1 at 95% C.L., 1.2 Run II,6.7 LHC (hep-ph/9905311) Effective Planck Scale lower limit (95% C.L.) 0.9-1.5 TeV Run I 1.3-2.5 TeV Run IIa, 1.7-3.5 TeV LHC Range corresponds to number of extra dimensions n=7-2. (hep-ph/9904234, hep-ph/9909218) DIS 2002, Poland

  15. Compositeness Quark-lepton contact interaction was searched for in Run I in the dimuon and dielectron channels, by looking for an excess of dileptons compared to the Drell-Yan prediction. Run Ib dielectron data set the limits on the compositeness scale to - > 3.8 TeV and + > 2.6 TeV. In Run II we expect to be able to explore up to limits of approximately 5 TeV. (Where +/- corresponds to the constructive / destructive interference with the dominant up-quark contribution to the cross-section.) (Phys. Rev. Lett.79: 2198-2203, 1997)) DIS 2002, Poland

  16. *,Z* q l- • Run I Data • Background MT = 100 GeV M, - M = 60 GeV M, - M = 100 GeV D0 Run I data q T0,T0 l+ CC-CC 103 102 101 1 1 10-1 10-2 Number of Events CC-EC B(T  T e+e-)* (pb) 103 102 101 1 95 % C.L. theoretical limits for T  T e+e- • 200 300 400 Minimum Mee (GeV) 100 200 300 400 500 Mass (GeV) Technicolour Integrated plots of dielectron mass distributions of D0 120 pb-1data and expected background No signal above background found. T and  T with masses < 225 GeV/c2 are ruled out for M(T) and M(T) < MW DIS 2002, Poland

  17. Run II Run II started in spring 2001 • CDF Upgrade improvements for Drell-Yan measurements • Dielectron channel • New plug calorimeter • Dimuon channel • Increased muon chamber coverage • Better background rejection using Time-of-Flight detector to remove cosmic rays DIS 2002, Poland

  18. Time-Of-Flight (ToF) Detector in CDF 216 scintillator bars located just outside the COT Expected time resolution is  100 ps. DIS 2002, Poland

  19. Cosmic Ray Sample Z ee ToF Cosmic-Ray Rejection Removal of the cosmic ray background is important for high mass dimuon sample Tupper – Tlower ~ 2L/c for CR dimuons ~ 0 for interaction ee and  Move Cosmic Rays with a cut requiring Tupper – Tlower > -5 ns Above plots are from uncalibrated ToF. Calibration work is in progress. DIS 2002, Poland

  20. Run II Drell-Yan spectrum Dielectron Dimuon DIS 2002, Poland

  21. Future Plans It is hoped that approximately 50-70 pb-1 data will be collected by Summer 2002 And  150 pb-1 by end of 2002. We hope to find new physics or set new limits using the dilepton channels. DIS 2002, Poland

  22. The End ! DIS 2002, Poland

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