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Fourth Tropical Workshop on Particle Physics and Cosmology

CP Violation, Dark Matter and Extra Dimensions in the D-Zero experiment at the Tevatron ?. Peter Ratoff Lancaster University. Fourth Tropical Workshop on Particle Physics and Cosmology FLAVOUR PHYSICS AND PRECISION COSMOLOGY 9-13 June 2003, Cairns, Queensland, Australia. The Tevatron. _.

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Fourth Tropical Workshop on Particle Physics and Cosmology

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  1. CP Violation, Dark Matter and Extra Dimensions in the D-Zero experiment at the Tevatron ? Peter Ratoff Lancaster University Fourth Tropical Workshop on Particle Physics and Cosmology FLAVOUR PHYSICS AND PRECISION COSMOLOGY 9-13 June 2003, Cairns, Queensland, Australia

  2. The Tevatron _ p-p collisions at s = 1.96 TeV

  3. The DØ Detector in Run 2 + New Software (OO C++) + STT displaced track trigger, Summer’03

  4. Run 1 Run 2 Now Date 1992 – 1996 2001 - 2009 2003 Integrated Luminosity 110 pb-1 6.5 – 11 fb-1 ~200 pb-1 c.m. energy 1.8 TeV 1.96 TeV 1.96 TeV Luminosity 2 x 1031 cm-2 s-1 2 x 1032 cm-1 s-1 4.5 x 1031 cm-2 s-1 Bunch spacing 3.5 ms 396 – 132 ns 396 ns Tevatron operating parameters

  5. Run 2 Luminosity Performance

  6. QCD Jet cross-section, shapes, multijet events Heavy flavour Lifetimes, cross-section, Bc, LB, Bs studies, CP violation, xs Electroweak W: mass, width, gauge couplings Top: mass, cross-section, branching ratios Searches Higgs, SUSY, extra dimensions, leptoquarks compositeness, etc. Physics in Run 2 # events in 1 fb-1 1014 1011 107 104

  7. Detector Performance: electrons and muons Electrons: D0: 10% Lumi error Muons

  8. Detector Performance: Jets Dominant systematic error: Jet energy scale (will improve with statistics)

  9. Detector Performance: b’s and B’s Jet Signed IP Golden mode for CP viol’n (Sin2) Interaction vertex Track

  10. Detector Performance: Taus Isolated electron opposite to narrow, single track jet. Signal enhanced using NN: Evidence forZ  +- eth (similar study in Z h) (New at DØ)

  11. Putting everything together: the top ! 3 observation X-section:

  12. B Physics at the Tevatron? • Large Cross Section! • Produce bottom mesons with all flavor combinations as well as bottom baryons • Bd, Bu, Bc, Bs, Lb, b, ... • DØ is a multipurpose detector capable of reconstructing many B final states • Rich B physics program • Cross-sections • Bs mixing • B lifetime • CP violation in Bd and Bs • Rare decays Bd Lb Bs

  13. B Physics Triggers • Have to go down from 2.5 MHz crossing rate to 50 Hz writing to disk (0.25 MB/event) • Sophisticated 3-level trigger system • Most useful triggers for B physics so far: dimuon triggers (simple and unprescaled) • Central (||<1): pT>3.5 GeV • Forward (1<||<2): pT>2-2.5 GeV • But can also do physics with single muon trigger ... • Coming soon (this summer): • L2 track trigger (track match to m/e) • L2 (STT) silicon track trigger (displaced vertices)

  14. m+jet T m Inclusive b cross-section • Begin with m in jet cross section • Extract b content via fit to pTrel distribution • Unfold jet energy resolution (unsmearing) • Dominant error: jet energy scale corrections

  15. J/ data sample • Exploit J/  m+m– mode • Results based on 40 pb-1 collected data (75k J/) • Calibration not finalized, mass not in good agreement with PDG

  16. Charged B lifetime Full reconstruction (B±  J/ K ±): no hadronization or momentum uncertainties ctB = Lxy M B / pTB <tB> = 1.76  0.24(stat) ps (PDG : 1.674  0.018)

  17. Semi-leptonic B meson decay 2% of current Run II data ! • single muon trigger works! • abundance of SL B decays • other decay channels to follow: • B  D*X • B  D+X • B  Ds X • excellent opportunities for various • B measurements (mixing, CP viol) • good source of B hadrons for • technical studies (trigger, b-tagging)

  18. e= 63.0 3.6% e= 8.3 1.9% D=15.8 8.3 % D=44.4 21.1% e= 65.8 2.4% e= 8.5 1.6 % D=2.4 4.1% D=-3.7 19.2% 2.4 1.7% 3.3 1.8 % B mixing - flavour tagging status Tagging power: eD2Significance of a mixing measurement is proportional to eD2 e: efficiency for a tag = D: Dilution = Tagging performance measured in B+ J/K+ - close to simulation expectations Jet tag Muon tag Signal region Sidebands eD2 for signal Muon tag: Charge of highest pT muon in the event (excluding those from reconstructed B) gives (opposite-side) b-tag Jet tag: Q=S qi pTi / S pTi, count events with |Q|>0.2

  19. CP violation in B hadron decays • Able to reconstruct “golden’’ channels for CP violation measurements • High statistics measurements with BS only possible at hadron colliders

  20. B physics prospects(with 2fb-1) Both competitive and complementary to B -factories • Bs mixing: Bs Ds(Ds)(xsup to 60, with xd meas. one side of U.T.) • Angle : B0 J/ Ks(refine CDF Run1 meas. up to (sin2)  0.05) • CP violation, angle: B0(K), Bs KK(K) • Angle s and s/ s : Bs J/(probe for New Physics) • Precise Lifetimes, Masses, BRfor all B-hadrons: Bs, Bc, b … (CDF observed: Bc J/ e(). Now hadronic channels Bc Bs X can be explored) • Cross sections • Stringent tests of SM … or evidence for new physics !!

  21. SUSY models • SUSY is the best motivated scenario today for physics beyond the Standard Model • doesn’t contradict precise Electroweak data • predicts light Higgs • unification of gauge couplings at GUT scale • essential element of String Theories • … provides explanation of Cold Dark Matter in the Universe! • SUSY must be broken symmetry (otherwise MSUSY = MSM) • variety of models proposed - differ mainly in the nature of the “messenger interactions” • most experimental results obtained in the context of the SUGRA and GMSB models

  22. ~ ~ b1 b 20  10 e+ e- ~ SUSY production • Neutralinos/charginos - trilepton channel - dilepton channel • squarks/gluinos (dominant) • jets + mET stop and sbottom ~ squarks and gluinos are quite heavy  decay via multi-step cascades:  many high Pt jets and leptons plus large missing transverse energy

  23. SUGRA models • SUSY breaking is communicated to the physical sector by gravitational interactions • GUT scale parameters + RGE’s  low-scale phenomenology M0 = common scalar mass M1/2 = common gaugino mass A0 = common trilinear coupling value tanb = ratio of the V.E.V. of the two Higgs doublets sign of m = Higgsino mass parameter Highly constrained minimal SUGRA  LSP is lightest neutralino - a neutral WIMP  excellent CDM candidate

  24. SMT CFT CAL Tracks as we know Kinks Large dE/dx Hot cell Photons as we know Impact parameter GMSB models • ‘Messenger’ sector couples to source of SUSY-breaking and physical sector of MSSM (through gauge interactions) • The identity of the NLSP and its lifetime determine the phenomenology c neutralino G slepton llG NLSP

  25. Current DØ searches for new phenomena • Model Independent • e + X • Supersymmetry: • SUGRA-inspired • Jets + Missing ET (Squarks) • Trileptons (Gauginos) • GMSB • Diphotons + Missing ET • Leptoquarks • 1st and 2nd generations • New Gauge Bosons • Dielectrons • Large Extra Dimensions • Dielectrons + Diphotons • Dimuons

  26. Jets + missing ET Generic signature for squarks and gluinos which, in SUGRA inspired models, cascade decay to (quarks and gluons  jets) + (two LSP’s  missing ET) • Select events with • at least one jet with pT > 100 GeV • Apply topological cuts • (e.g., on jet- missing ET angles) • Simulate physics backgrounds • (with real missing ET) • Estimate the large instrumental • QCD background from the data • (empirical fit) “Proof of existence” with ~ 4 pb-1 No surprise: For missing ET > 100 GeV: 3 events observed vs. (2.7  1.8) expected

  27. eel + X Backgrounds Data p (e ) > 15 GeV, p (e ) > 10 GeV 3216 ± 43.2 3132 T 1 T 2 10 GeV < M(ee) < 70 GeV 660.2 ± 19.1 721 M > 15 GeV 96.4 ± 8.1 123 T Add. Isolated Track, p > 5 GeV 3.2 ± 2.3 3 T Missing E > 15 GeV 0.0 ± 2.0 0 T Similar analysis in the el channel Signal: Start from dielectron sample (~40 pb-1) allows for h Typical mSUGRA selection efficiency: 3 to 4% at the edge of the excluded region Sensitivity still about a factor 7 away from extending the excluded domain “Golden channel”: very low backgrounds, but large statistics will be needed

  28. GMSB - diphotons In GMSB, the LSP is a light gravitino With a “bino” NLSP, the signature is therefore two photons with missing ET: Require two isolated photons with pT > 20 GeV Apply topological cuts Determine the instrumental QCD background from the data (inversion of photon quality cuts) Theory = "Snowmass“ slope: M = 2, N5 = 1, tan = 15, > 0 With ~50 pb-1, the Run I limit is approached

  29. Large Extra Dimensions where Search for the effects of KK graviton exchange in the ee,  and  final states: Ms is the fundamental Planck scale. To solve the hierarchy problem, one can have Ms in the TeV scale for n > 2 extra dimensions (n=1 is ruled out and n=2 is tightly constrained). • Two discriminating variables are used: • the dilepton/diphoton mass • the scattering angle in the rest frame

  30. LED in the ee/ channels • Determine • Physics backgrounds from simulation • Instrumental backgrounds from data • Require • 2 EM objects with pT > 25 GeV • and missing ET < 25 GeV Fit G => MS > 1.12 TeVin GRW formalism MEM-EM = 394 GeV cos * = 0.49 (with ~50 pb-1: close to Run I, similar to LEP)

  31. LED in the  channel • Determine • Drell-Yan background from simulation • QCD background from data • Require • 2 opposite sign muons with pT > 15 GeV • and M > 40 GeV With ~ 30 pb-1: MS > 0.79 TeVin GRW formalism M = 347 GeV (New channel at the Tevatron, similar to LEP)

  32. Large Extra Dimensions Search: Results • Fit the distributions in the Mll - cos* plane to determine the value of hG ( hG = 0 in SM)Di-EM analysis: hG = 0.0 ± 0.27 TeV-4Di-Muon analysis: hG = 0.02 ± 1.35 TeV-4 • Extract 95% CL upper limits on hG • Translate to 95% CL lower limits on Planck scale MS , in TeV, using different formalisms for F Di-EM limit close to Run I Di-Muon (new)

  33. Summary and Conclusions • DØ is almost fully operational following major upgrades • for Run II (some trigger improvements to come e.g STT) • The Run I data sample has now been exceeded and physics • results are emerging from the first 40-50 pb-1 • The B physics potential of DØ has been established • Good lepton, photon, jet and missing ET detection enables • DØ to perform many new physics searches • Measurements of cosmological significance can be expected • in the coming few years with data samples > 5 fb-1 • CP violation (unitary triangle angles, beyond the SM?) • dark matter candidates/limits (e.g. neutralino LSP) • large extra dimensions/limits

  34. SUSY Particle Zoo

  35. SUSY search Run I(120 pb-1) Run II Jets +mET (new) ---------  x < 4.2 pb(4.1 pb-1) mET >70 GeV e +mET ? A xs<0.1 pb(33 pb-1) mET >45 GeV lll+mET (Run I) eel+mET (Run II) • xBR< 0.3 pb M(0)60 GeV mET >10-15 GeV sxBR< 2.2 pb(42 pb-1) M(0)=62 GeV mET >15 GeV Where we are standing: Run I vs Run II

  36. Analysis Run I(120 pb-1) Run II SUSY 2 + mET M(0) > 75 GeV M(0) > 66 (40 pb-1) 1st LQ 2 e + 2 jets MLQ > 225 GeV MLQ > 179 (43 pb-1) 2nd LQ 2  + 2 jets MLQ > 200 GeV MLQ > 157 (30 pb-1) LED 2em MS> 1.1 TeV MS> 1.0(50 pb-1) LED 2  (new) ------- MS> 0.71(30 pb-1) Where we are standing: Run I vs Run II A lot of another analyses are going on: gauge interactions search, SUGRA particles search with the different jets & leptons & mET signatures … etc

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