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Charm production cross section and charm physics at the Tevatron

Charm production cross section and charm physics at the Tevatron. Sandro De Cecco INFN Roma 1 “Rencontres de physique du Vietnam”, Hanoi 07 aout 2004. Outline. The Tevatron collider CDF detector and triggers. Highlights on hadronic heavy flavours production.

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Charm production cross section and charm physics at the Tevatron

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  1. Charm production cross section and charm physics at the Tevatron Sandro De Cecco INFN Roma 1 “Rencontres de physique du Vietnam”, Hanoi 07 aout 2004 Sandro De Cecco - INFN Roma 1

  2. Outline • The Tevatron collider • CDF detector and triggers. • Highlights on hadronic heavy flavours production. • Measurement of prompt charm production cross section. • Search for direct ACP in D0Cabibbo suppressed decays. • Search for FCNC decay D0mm. • Conclusions and perspectives ! Disclaimer:results come from CDF only; D0 is going to publish charm physics results soon Sandro De Cecco - INFN Roma 1

  3. The Tevatron pp collider Superconducting proton-synchrotron: 36p36p bunches, crossing each 396 ns at √s = 1.96 TeV Luminosity……………………………..: record peak L=1  1032 cm-2s-1 (as of July 04) # interactions / bunch-crossing……...: < N >= 1.5 (@ 5 x 1031cm-2s-1) Luminous region size………………...: 30 cm (beam axis) x 30 mm (transverse) Sandro De Cecco - INFN Roma 1

  4. Tevatron plans • RECYCLER had a first successful test • Plans beyond FY 05 depends on Recycler ring and electron cooling performances • Will see after aug./nov.04 shutdown Sandro De Cecco - INFN Roma 1

  5. Tevatron FY04 performance L (pb -1) FY04Design FY04 Base 1st May 2004 2003 1st Jan. 2004 2002 • Tevatron is working very well this year (Design plan): • Initial luminosity (may 04) = 7.2 X 1031sec-1 cm-2 (now 1.x1032) • Weekly Integrated luminosity ~ 10 pb-1/w • ~350 pb-1 on tape, 100-200 pb-1 used for analysis so far Sandro De Cecco - INFN Roma 1

  6. The upgraded detectors • New silicon detector • new drift chamber • Upgraded calorimeter, m • Upgraded DAQ/trigger, • displaced-track trigger • New TOF PID system • New tracking: silicon and • fibers in magnetic field • Upgraded muon system • Upgraded DAQ/trigger • (displaced track soon) Sandro De Cecco - INFN Roma 1

  7. b b g g b g q b b b b b q g g g q q Flavor Excitation Flavor Creation (gluon fusion) Flavor Creation (annihilation) Gluon Splitting HF Physics at pp collider bb/cc production mechanics in hadron collider: LO NLO • Huge cross-section: 50-100 b • All B/D species produced: • Bu,Bd,Bs,Bc,B*,b, b… • D0,D,D*,Ds,D**,c, c… • BUT:(bb,cc) << (pp) (~65 mb)  HF events have to be selected with specific triggers • Trigger requirements:large bandwidth, background suppression, small dead-time Sandro De Cecco - INFN Roma 1

  8. Study bb correlation B production x-section, Run I B cross section measured from Run I at Tevatron is consistently higher than NLO QCD Theoretical development still ongoing. Ex: fragmentation effect ……. Experimental Approaches: More cross section measurement -- energy at 1.96TeV -- lower pT(B)  Measure CHARM production cross section Sandro De Cecco - INFN Roma 1

  9. ~ 1 mm b,c decays primary vertex secondary vertex Impact Parameter ( ~100mm) Heavy Flavours triggers at CDF II With the NewSilicon Vertex Trigger Conventional at colliders (Run I) Di-Muon (J/) Pt() > 1.5 GeV J/ modes down to low Pt(J/)~0 (Run II) Rare decays Displaced track + lepton (e, ) I.P.(trk) > 120m Pt(lepton) > 4 GeV Semileptonic modes 2-Displaced tracks PT(trk) > 2 GeV pT> 5.5 GeV I.P.(trk) > 120(100) m fully hadronic modes + Sandro De Cecco - INFN Roma 1

  10. COT track ( 2 parameters) 5 SVX coordinates beam spot d Impact Parameter (transverse projection) SiliconVertexTracker: thehadronic B trigger • Online Impact parameter • Available at Level 2 trigger (20µs latency) • Trigger decision • convolution of transverse size of the beam spot with the impact parameter resolution of the SVT: s≈47 um ≈ 35 um + 30 um SVT resolution Beam spot size ( Compare to offline ~ 46 mm ) Impact parameter distribution Collect large amount of fully reconstructed B,D hadrons: Sandro De Cecco - INFN Roma 1

  11. Prompt Charm Meson X-Section With early CDF data: 5.80.3pb-1 • Measure prompt charm meson • production cross section • Data collected by SVT trigger • from 2/2002-3/2002 • Measurement not statistics limited • Large and clean signals: Sandro De Cecco - INFN Roma 1

  12. Separating prompt from secondary Charm Separate prompt and secondary charm based on theirtransverse impact parameter distribution. Prompt D Secondary D from B • Need to separate direct D and BD decay • Prompt D point back to collision point • I.P.= 0 • Secondary D does not point back to PV • I.P. 0 Prompt peak Detector I.P. resolution shape measured from data in K0s sample. BD tail Direct Charm Meson Fractions: D0: fD=86.4±0.4±3.5% D*+: fD=88.1±1.1±3.9% D+: fD=89.1±0.4±2.8% D+s: fD=77.3±3.8±2.1% Most of reconstructed charm mesons are direct  Sandro De Cecco - INFN Roma 1

  13. Prompt Charm Meson X-Sections Determine trigger and reconstruction efficiency from data and MC Measure charm meson pT spectrum Integrated cross sections: As a comparison the beauty meson x-sec (CDF Run I): CDF prompt charm cross section result published in PRLhep-ex/0307080 Sandro De Cecco - INFN Roma 1

  14. Differential Charm Meson X-Section PT dependent x-sections: Theory prediction: CTEQ6M PDF Mc=1.5GeV, Fragmentation: ALEPH measurement Renorm. and fact. Scale: mT=(mc2+pT2)1/2 Theory uncertainty: scale factor 0.5-2.0 Calculation from M. Cacciari and P. Nason: Resummed perturbative QCD (FONLL) JHEP 0309,006 (2003) Sandro De Cecco - INFN Roma 1

  15. Comparison with Theory Ratio of measured to predicted cross sections: PRL89:122003,2002 • NLO calculations compatible within errors • pTshape is consistent for D mesons • Measured cross section is • ~1.5 factor higher: similar to B Sandro De Cecco - INFN Roma 1

  16. D0→h+h- direct CP Asymmetries and Decay Rate ratios • The huge amount data collected by the Two Track Trigger have been used for this analysis • Relative branching ratios: • G(D0→K+K-) / G(D0→Kp) • G(D0→p+p-) / G(D0→Kp) • G(D0→KK) / G(D0→pp)~2.8 (SM) • Direct CP asymmetries where • f is CP eigenstate (ex. K+K-,p+p-): • Candidates selected as: D*+/-→D0p (unbiased tag of the D0 flavor) Normalization mode D0→Kp ~180000 D*+/-→ D0p!!! Sandro De Cecco - INFN Roma 1

  17. D0 Cabibbo suppressed 2 body decays D0 pp KK D0 Sandro De Cecco - INFN Roma 1

  18. CP Asymmetries and Decay Rate ratios Very important to understand the asymmetry of the CDF detector at per mille level !!! • Results are computed after correction for: • intrinsic charge asymmetry • relative acceptance between the D0 modes Submitted to PRL august 04 Sandro De Cecco - INFN Roma 1

  19. Search for FCNC D0→mm • SM expectation BR~ 3∙10-13 • Best limit: <4.1∙10-6 (90% CL) (Beatrice/WA92, E771) • BR significantly enhanced with New Physics (e.g. R-Parity Violation Susy: ~3.5*10-6) • Experimental strategy: • Events from two-track trigger using first 69pb-1 of data • To cancel acceptance effects normalize toD0→pp • Only relative efficiency needed Sandro De Cecco - INFN Roma 1

  20. FCNCD0→mm: Results Combinatorial:1.5+-0.7 events Fakes: 0.22+-0.02 events 1.7 expected events 0 events observed Mmm with D* tag and 2 muons BR(D0→mm)<2.4x10-6 (@90% CL) Factor 2 improvement over best limit Next:use full muon coverage and 2-3 times more data (~1year)  also look atD+→pmm, D+→Kmm, D0→me, Ds Sandro De Cecco - INFN Roma 1

  21. Conclusions • Prompt charm cross-section has been measured for the first time at collider  useful input to QCD calculations for HF production and hadronization models. • Hadronic D0 decays relative BR’s measured with high accuracy • Search for direct CP asymmetries in Cabibbo suppressed D0 decays is world best single measurement. • CDF will soon be sensitive to beyond SM theories with rare D decays • Charm yields are competitive to B-factories and physics program complementary to CLEO-C. The charming side of the Tevatron… Sandro De Cecco - INFN Roma 1

  22. BACKUP slides Sandro De Cecco - INFN Roma 1

  23. CDF II tracking system TOF:100ps resolution, 2 sigma K/ separation for tracks below 1.6 GeV/c (significant improvement of Bs flavor tag effectiveness) - charge) TIME OF FLIGHT CDF Roma COT: large radius (1.4 m) Drift chamber • 96 layers, ~100ns drift time • Precise PT above 400 MeV/c • Precise 3D tracking in ||<1 (1/PT) ~ 0.1%GeV –1; (hit)~150m • dE/dx info provides >1 sigma K/ separation above 2 GeV • SVX-II + ISL: 6 (7) layers of double-side silicon (3cm < R < 30cm) • Standalone 3D tracking up to ||= 2 • Very good I.P. resolution: ~30m (~20 m with Layer00) LAYER 00:1 layer of radiation-hard silicon at very small radius (1.5 cm) (achievable: 45 fs proper time resolution in Bs  Dsp ) Sandro De Cecco - INFN Roma 1

  24. CDF II particle ID handles # s TOF PID • Specific Ionization of charged particles (dE/dx) measurement in the COT gas chamber. • Time of flight measurement with the new scintillator bars detector (TOF) at R=1.4m with a sTOF = 100 ps dE/dx PID p Total K/p separation power of at least 2sfor momentum up to 1.6 GeV/c with TOF And at least 1sfor momentum up to 4-5 GeV/c with TOF + dE/dx Sandro De Cecco - INFN Roma 1

  25. Crossing: 396 ns: 2.5 MHz Level 1: hardware Calorimeter, Muon, Track 15kHz (reduction ~x200) Level 2: hardware + CPU Cal cluster, Silicon track 300 Hz (reduction ~x5) Level 3: Linux PC farm ~ Offline quantities 50 Hz (reduction ~ x6) CDF Trigger System Overview Sandro De Cecco - INFN Roma 1

  26. CDF data tacking performance Data-Taking Efficiency Integrated Luminosity Detector efficiency ~85-90% Sandro De Cecco - INFN Roma 1

  27. Charge Asymmetry in the CDF Detector Study asymmetry using unbiased tracks and correct • Residual asymmetry syst.error (same track quality cuts generic track sample) (Expect no CP asymmetry) Sandro De Cecco - INFN Roma 1

  28. Normalization Mode: D0→pp Search window: 1.84<m<1.884 GeV Selection: intersect D0 with soft p 0.144<m(D*)-m(D0)<0.147 Optimized cuts: Lxy<0.45 cm, |dxy|<0.015cm, Angle cut between track and muon stub, Track quality cuts N(pp) = 1371+-53 Kp Relative efficiency from Monte Carlo: ( muon reconstruction and p decay in flight efficiency) Sandro De Cecco - INFN Roma 1

  29. D0→mmBackground Estimate combinatorics from high mass sideband where both tracks are muons Fakes from p misidentification: N(D0→pp) in mass window times (misid probability)2: p misid probability From D* tagged D0→Kp Combinatorics:1.5+-0.7 events Fakes: 0.22+-0.02 events Sandro De Cecco - INFN Roma 1

  30. X(3872) physics: the B fraction Sandro De Cecco - INFN Roma 1

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