1 / 46

Future Perspectives for Charm Physics at Hadron Machines

Future Perspectives for Charm Physics at Hadron Machines. Sandro De Cecco FNAL-PPD/CDF and INFN Roma 1. Outline:. Introduction on Heavy Flavour physics at hadron colliders. Charm production, charm as a probe for QCD Heavy quarks hadro-production in pp and NN interactions DD correlations

leora
Télécharger la présentation

Future Perspectives for Charm Physics at Hadron Machines

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Future Perspectives for Charm Physicsat Hadron Machines Sandro De Cecco FNAL-PPD/CDF and INFN Roma 1 Sandro De Cecco - FNAL / INFN Roma

  2. Outline: • Introduction on Heavy Flavour physics at hadron colliders • Charm production, charm as a probe for QCD • Heavy quarks hadro-production in pp and NN interactions • DD correlations • Charmonium • Excited states, c-barions • Charm input to CP violation picture • D0 mixing • Direct CPV in Charm decays • FCNC decays • The Experimental “Charm” of Hadron Colliders Sandro De Cecco - FNAL / INFN Roma

  3. Heavy-Quark production in hadron collisions Leading Order and Next to Leading Order Q g Q g g g Flavor excitation radiative corrections Flavor creation Gluon splitting B/D-Hadrons and/or b/c-jets are the observables rather than b/c-quark Observed Proton structure Fragmentation NLO QCD Factorize physical observable into a calculable part and a non-calculable but universal piece Sandro De Cecco - FNAL / INFN Roma

  4. Fragmentation functions Db/c B/D Perturbative part: probability to find a hadron with fraction x’ of original parton momentum Hadronization: non perturbative QCD, need models Charm will have softer P-spectrum than b. Sandro De Cecco - FNAL / INFN Roma

  5. (-) s(pp→X) Tevatron SppS LHC 1mb s(bb) 1mb 1nb 1pb 0.001 0.01 0.1 1.0 10 102 √s (TeV) Charm and beauty at collider • Total inelastic x-sec ~100 mb • = 103-104 x s(cc/bb) • x-sec is 105-106 larger than at e+e- • Open spectrum of mesons and barions: • Bu , Bd , Bs , Bc , b , b… • D+, D0, Ds , c , cc , c… • Large cross section  • Select triggering on: • Semileptonic decays • Trigger m, e • Hadronic decays (CDF-SVT) • One or more displaced tracks i.e. large impact parameter Sandro De Cecco - FNAL / INFN Roma

  6. Lxy ~ 1 mm B/D decay Primary Vertex Secondary Vertex Impact Parameter( ~100mm) Selecting heavy flavour decays CLEO • To select charm and beauty • In hadronic environment: •  High resolution tracking • detector is mandatory • Only way to access hadronic decays is to trigger on tracks CDF Example: the CDFSecondary Vertex Trigger SVT • Online (L2) selection of displaced tracks • based on Silicon detector hits. D0 K Sandro De Cecco - FNAL / INFN Roma

  7. Charm program at hadronic machines Tevatron • First experiment doing high precision charm physics at collider, collecting huge yields in hadronic D modes • Many results already (in this talk) and more to come • Nice charm physics program mainly on rare FCNC and LFV rare decays ( see Frank Lenher talk ) • Relies on the presence of a muons to trigger charm • Expect to be able to select clean charm signals thanks to fine tracking and PID • Will measure cc x-sections in pp, pN and NN collisions LHC • Thinking about having a dedicated D* charm trigger selecting huge and clean samples of hadronic D modes • Will definitely take over what CDF started in the search for CPV and mixing in charm Sandro De Cecco - FNAL / INFN Roma

  8. Open cc Production Sandro De Cecco - FNAL / INFN Roma

  9. Prompt Charm Meson X-Section With very 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 is not statistics limited • Large and clean signals: Sandro De Cecco - FNAL / INFN Roma

  10. Separating prompt from secondary Charm Separate prompt and secondary charm based on their transverse 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 D impact parameter 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 mesons are prompt Sandro De Cecco - FNAL / INFN Roma

  11. 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 - FNAL / INFN Roma

  12. Differential Charm Meson X-Section D*+ D+ Ds D0 PT dependent x-sections: (as reference) Data/Theory PRL89:122003,2002 Theory prediction: Calculation from M. Cacciari and P.Nason: Resummed perturbative QCD (FONLL) JHEP 0309,006 (2003) Measured x-section is ~1.5 factor higher: similar to B+ Sandro De Cecco - FNAL / INFN Roma

  13. Open cc production future studies: • Studying cc correlations through angular difference Df. • Can separate contributions from different production mechanisms: • Flavour creation • Flavour Excitation • Gluon splitting • Issues are: • Low efficiency to have opposite charm in the acceptance • Backgrounds at low Df from BDDX decays. • CDF already has clean samples of D*-D0, D*-D+ and D*Ds consisting of ~ few 100’s / few 1000’s events depending on the modes. • Expect to have correlation results based on 1 fb-1 of Luminosity Df BDD BBbar Sandro De Cecco - FNAL / INFN Roma

  14. Charm as a probe in Pb-Pb collisions ( from C. Fabjan ) • Heavy quarks with momenta < 20–30 GeV/c  v << c • Gluon radiation is suppressed at angles < mQ/E • “dead-cone” effect • Due to destructive interference (inside cone gluon with v=c would violate causality) • Contributes to the harder fragmentation of heavy quarks and implies lower energy loss for heavy quarks relative to light quarks A.Dainese nucl-ex/0311004 D mesons quenching reduced Ratio D/hadrons (or D/p0) enhanced and sensitive to medium properties Yu.L.Dokshitzer and D.E.Kharzeev, Phys. Lett. B519 (2001) 199 [arXiv:hep-ph/0106202]. Sandro De Cecco - FNAL / INFN Roma

  15. Hadroniccharm selection Combine ALICE tracking + secondary vertex finding capabilities (sd0~60mm@1GeV/c pT) + large acceptance PID to detect processes asD0K-+ ~1 in acceptance / central event ~0.001/central event accepted after rec. and all cuts Results for 107 PbPb ev. (~ 1/2 a run) significance vs pT S/B+S ~ 37 S/B+S ~ 8 for 1<pT<2 GeV/c (~12 if K ID required) Sandro De Cecco - FNAL / INFN Roma

  16. mc PDFs scales pp, 14 TeV down to 1 GeV/c! down ~ 0! D0 Cross section measurement Pb-Pb Sandro De Cecco - FNAL / INFN Roma

  17. Charmonium Production Sandro De Cecco - FNAL / INFN Roma

  18. Inclusive J/yproduction CDF: Lower pT trigger threshold for : pT() ≥ 1.5 GeV J/y acceptance down to pT=0 0<pT<0.25 GeV D0: Larger acceptance for  total J/y production cross section at Tevatron is: D0: 4.8 pb-1 CDF: 39.7 pb-1 Sandro De Cecco - FNAL / INFN Roma

  19. Inclusive bcross section • Run I: b cross-section ~ 3x old NLO QCD • Theoretical approaches: new physics, Next-to-Leading-log resummations, non perturbative fragmentation function from LEP, new factorization schemes… • Experimentally: unbinned maximum likelihood fit to the flight path of the J/yin the R- plane to extract the b fraction Run II: Bottom Quark Production cross-section: PRD 71, 032001 (2005) Good agreement  Sandro De Cecco - FNAL / INFN Roma

  20. g + b/c x-section • Probes heavy flavor content of the proton and its PDF (also with Z0) • Experimental approach: • One isolated and High Etg (> 25 GeV) • One jet with a secondary vertex (b/c “like” jet) • Fit on the secondary vertex mass distribution of the tagged jets to separate b, c and light quarks g + c g+ b s(b + g) = 40.6 +/- 19.5 (stat.) + 7.4 -7.8 (sys.) pb s(c + g) = 486.2 +/- 152.9 (stat.) + 86.5 -90.9 (sys.) pb Sandro De Cecco - FNAL / INFN Roma

  21. Other charm states Sandro De Cecco - FNAL / INFN Roma

  22. excited D** states • Plenty of D**: Dj narrow, wide, radial, orbital, resonant, nonresonant… • Narrow states are the only widely observed objects so far… • HQET predicts splitting of states vs mQ • The large statistics of charm at CDF gives access to D** Sandro De Cecco - FNAL / INFN Roma

  23. D** Properties D1,2 D*+- D*+D0+ D0K-+ D2 D+- D+K+-- Prompt D1,2 • Huge sample of narrow D** resonances • Competitive in measuring prompt D** properties! • … and secondary from B’s Secondary D** Sandro De Cecco - FNAL / INFN Roma

  24. D** results High precision masses and widths from prompt D1,2 M(D1)=2421.7 0.7 0.6 MeV (D1)=20.0 1.7 1.3 MeV M(D2)=2463.3 0.6 0.8 MeV (D2)= 49.2 ±2.3 ±1.3 MeV Non-leptonic mass in BlXcwhere Xc is D** mass moments analysis mean r.m.s Probe HQET and contraints for CKM element Vcb Sandro De Cecco - FNAL / INFN Roma

  25. …charm et al. … c-Barions decaying in fully hadronic modes accessibles with SVT trigger and … X(3872) J/y pp M(pp) spectrum fraction from B: (16.0 ±4.9 ±1.0)% Sandro De Cecco - FNAL / INFN Roma

  26. Charm Rare Decays Sandro De Cecco - FNAL / INFN Roma

  27. Search for FCNC D0→mm • SM expectation BR~ 3∙10-13 • Best limit: <4.1∙10-6 90% CL, Beatrice/WA92,E771 • Enhanced in N.P. (R-Parity Violation Susy: ~3.5*10-6) • Experimental strategy CDF: • Events from two-track trigger using first 69pb-1 of data • To cancel acceptance effects normalize toD0→pp Result: BR(D0→mm)<2.4x10-6 at 90% CL Comment:muon fake rate will set limit (~10-6) Next:use full muon coverage, add statistics, explore electron modes (less coverage but lower fake rate)  also look atD+→pmm, D+→Kmm, D0→me and Ds … see Frank Lenher talk in this workshop for details Sandro De Cecco - FNAL / INFN Roma

  28. CP Violation and Mixing in neutral D Sandro De Cecco - FNAL / INFN Roma

  29. D0→h+h- direct CP Asymmetries and BR’s • Search for direct CP asymmetries where f is CP eigenstate (ex. K+K-,p+p-): • …in single Cabibbo suppressed modes (KK) • Almost null in Cabibbo allowed (Kp) •  Use D0Kp as normalization mode • Data collected by the SVT trigger with 123 pb-1 of int. Luminosity • 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) • Candidates selected as: D*+/-→D0p • (unbiased tag of the D0 flavor) Normalization mode D0→Kp ~180kfrom D*+/-→ D0p Sandro De Cecco - FNAL / INFN Roma

  30. Direct ACP in Cabibbo suppressed D0 decays D0KK 16220 200 D0pp 7334 97 • Systematic dominated by tracking charge asymmetry, scales with statistics of control sample • KK channel suffers from partially reconstructed D background , would benefit from PID. • CDF yields prospects: 2MD* taggedD0Kp per 1 fb-1 • sACP ~ 10-3is achievable with full Tevatron run (4-9 fb-1) - at SM limit • issue will be if SVT trigger can cope with Lumi increase. Sandro De Cecco - FNAL / INFN Roma

  31. Mixing in the D0 system • D0 mixing receives x and y contributions • SM model expectations: • x and y : ~ 10-4 - 10-2 • (depending on the model) • Enhancements in x could be hint of New Physics • RSM ~ O(10-6) Sandro De Cecco - FNAL / INFN Roma

  32. Search for D0 mixing through DG Can search for DG comparing lifetime of CP eigenstate (D0→KK) and CP mixed state (D0→K): yCP  t(K)/t(KK) - 1 Best measurement at present from BaBar: syCP=0.006 yCP=0.034 0.0140.007 • CDF is currently performing D0  KK, pp, Kplifetime analysis • expect s(ct) < 2 mm (statistical only) • most of systematics cancel in the ratio, but: • Deconvolve SVT trigger bias at 1 mm level is a challenge • Nasty effect from secondary D0 from B’s Sandro De Cecco - FNAL / INFN Roma

  33. Direct Search for Mixing • Most sensitive method comes from looking for ‘Wrong Sign’ K pairs in D0 decays. • These occur directly through DCS decays. • Time dependent analysis can decouple contributions from: DCS • Direct DCS • Interference • Mixing D0K+ - D0 Mix (x’ and y’ because of possible strong phase difference between diagrams) Sandro De Cecco - FNAL / INFN Roma

  34. D0 Wrong Sign decays (time integrated analysis) • Almost 0.5 M Right Sign D*D0preconstructed in 350 pb-1 selected by SVT trigger • No PID so use of kinematics to reduce background from misreconstructed D0 Get the WS D* yield binning in D* mass difference  fit the signal NWS = 2005 ± 104 Sandro De Cecco - FNAL / INFN Roma

  35. D0 Wrong Sign rate results: Time integrated WS/RS ratio: Which in the limit of no mixing is: RWS:RS = RD = BR(D0K+p-)/BR(D0K-p+) • Results competitive with B-factories (CDF has x2 data on tape) • Next step:time dependent analysis and limit in the x’ y’ plane Sandro De Cecco - FNAL / INFN Roma

  36. LHC-b prospects for charm CPV and mixing ( from Guy Wilkinson and Frederic Teubert ) • Will implement a dedicated D* trigger stream: • Hadron trigger: displaced vertex +high PT tracks (4kHz). Expected compositionb:c~ 50%:20% • High level D*(D0hh)pselection “offline quality” (250Hz). Expect b:c ~ 36%:24% • In one year of running (107 s) at nominal luminosity (2·1032cm-2s-1): • Expect 250 - 500 M D*  D0pdecays with D0Kp channel, 102 x CDF ! • Raw estimates (based on signals statistics only) for sensitivity to charm CPV and mixing are: • s(ACP)[D0KK] ~ 10-4 normalizing to Kp mode • s(yCP) ~ 10-4in the lifetime difference analysis • s(x’) ~ 10-5 in mixing search through Wrong Sign' Kp signals LHC-b will possibly be sensitive in SM range, detailed studies on-going … Sandro De Cecco - FNAL / INFN Roma

  37. Summary • Charm production (cc and charmonium) is usefull test of QCD calculations to be tuned for precise background estimates in NP searches. • Already high precision results from Tevatron, to be explored at LHC. • A wide range of charmed hadrons are accessible at collider experiments, complementarity to e+e- • CDF demonstrates that is possible to perform high precision searches for charm CPV and mixing in hadronic modes D0hh • LHC-b will have 2 orders of magnitude more D0hh yields and will be very competitive in this field. • Huge CDF and D0 legacy of knowledge in doing Charm Physics at hadronic machines is left to next generation experiments. Sandro De Cecco - FNAL / INFN Roma

  38. Backup slides Sandro De Cecco - FNAL / INFN Roma

  39. Tevatron performances • CDF II has collected so far ~ 1.26 fb-1 out of 1.57 fb-1 delivered by Tevatron. • Record peak luminosity is ~1.8∙1032cm-2s-1 • Around 900 pb-1are availablefor Charm/Beauty physics (good tracking detector conditions) • Current analysesuse 180 - 350 pb-1 of integrated luminosity Sandro De Cecco - FNAL / INFN Roma

  40. The CDF II detector CDF Tracking System • Lepton ID • Particle ID • Muons:CMU, CMP, CMX (||<1.1) • dE/dX in COT • Electrons: CEM (EM calorimeter) • CPR (pre-shower detector) • Time Of Flight detector Sandro De Cecco - FNAL / INFN Roma

  41. COT track ( 2 parameters) 5 SVX coordinates Lxy ~ 1 mm B decay Primary Vertex Secondary Vertex Impact Parameter( ~100mm) beam spot d Impact Parameter (transverse projection) SVT: the CDF hadronic h.f. trigger • Online Impact parameter • Available at Level 2 trigger (20µs latency) • convolution of transverse size of the beam spot with the impact parameter resolution of the SVT: s≈47 mm ≈ 35mm + 30 mm SVT resolution Beam spot size Impact Parameter distribution Offline s ~ 45mm Sandro De Cecco - FNAL / INFN Roma

  42. B physics triggers at CDF II Conventional at colliders (Run I) With SVT trigger 2-Displaced tracks PT(trk) > 2 GeV 120 m < I.P.(trk) < 1mm SpT> 5.5 GeV fully hadronic modes 1-Displaced track + lepton (e, ) 120 m < I.P.(trk) < 1mm PT(lepton) > 4 GeV Semileptonic modes Di-Muon (J/) Pt() > 1.5 GeV J/ modes down to low Pt(J/)~0 (Run II) + Sandro De Cecco - FNAL / INFN Roma

  43. 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 - FNAL / INFN Roma

  44. 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 - FNAL / INFN Roma

  45. Charmonium as probe for diffractive Higgs • Calibration signature: • exclusive D.P.E. production of cc • search for cc  J/y g •  Esclusive channel:p + p  p + H (bb) + p • Hexcl ~ 3 fb , signal / background ~ 3 @ LHC • then: MH= Mmiss = Sandro De Cecco - FNAL / INFN Roma

  46. Welcome back to Bc • Mode that gave the first evidence of the Bc (CDF Run I) • Large yield, no clean resonance though! 106 events 46.07.3 events • First signal of fully reconstructed Bc • Mass measurement on ~0.8 fb-1 ~ 39 signal candidates Sandro De Cecco - FNAL / INFN Roma Hep-ex/0505076

More Related