Katerina Tzamariudaki NTUA & MPI-Munich

1. Recent Highlights on Heavy Flavour Production at HERA Katerina Tzamariudaki NTUA & MPI-Munich Heavy Flavour Production at HERA

2. Heavy Flavour Production at HERA Heavy flavour production dominated byBoson Gluon Fusion (BGF) or Kinematics: = 320 GeV : 4-momentum transfer squared : Bjorken : Inelasticity : Mass of the hadronic system Two kinematic regimes: Photoproduction DIS Factorization: Fragmentation function Photon structure Proton PDF Heavy Flavour Production at HERA

3. Heavy Flavour Production at HERA Heavy Flavour Production at HERA Perturbative QCD: study production mechanism • ()provides a hard scale pQCD applicable • ,( ) also provide a hard scale multiscale problem • sensitivity to the parton evolution model Non-perturbative: • parton densities in the proton and in the photon • Fragmentation testuniversality DGLAP CCFM Heavy Flavour Production at HERA

4. pQCD calculations Different approximations to avoid large terms with or massive scheme (FO NLO): massless scheme: c, b produced dynamically c, b partons in proton or photon leading NLO graphs leading NLO graphs neglect resum valid at valid at Variable FNS: match between massive and massless Programs: NLO parton level or LO + PS hadron level MC (DGLAP or CCFM) Heavy Flavour Production at HERA

5. c, b Identification • Resonance reconstruction • Lepton tag - large c, b mass (high pTrel, high jet mass) • Long lifetime (impact parameter, secondary vertices) • Heavy Flavour double tag studying correlations talk by A. Keramidas Heavy Flavour Production at HERA

6. Charm Production in DIS Charm tagging with NLO pQCD: generally good description of inclusive charm production over 4 orders of magnitude in Q2 Heavy Flavour Production at HERA

7. HERA c, b Production (LO) Momentum fraction of photon in jets: resolved direct p Structure Functions Heavy Flavour Production at HERA

8. Charm in the photon jet2 -exchange: -exchange: Clear evidence for charm from the photon Strong rise in towards the direction for Heavy Flavour Production at HERA

9. Charm Production in Photoproduction FONLL (massless) NLO QCD (massive) • Measurements more precise than theoretical calculations • shape of not well described • at large values massive calculation agrees better than massless expect the opposite • at low values massless calculation agrees better than massive Heavy Flavour Production at HERA

10. Charm Production in DIS CCFM NLO DGLAP (massive) NLO DGLAP (massless) • NLO QCD (massless) describes the cross section • shape of distribution is well described only by CASCADE Heavy Flavour Production at HERA

11. Charm + Jets in Photoproduction (Q2 ~0) • PYTHIA (LO+PS): dir+res contributions describes the data only moderately • CASCADE (LO+PS): describes the data well • NLO pQCD: one parton radiation not sufficient • Need NNLO? Heavy Flavour Production at HERA

12. Charm + Jets in Photoproduction (Q2 ~0) direct enriched resolved enriched • NLO QCD is below the data mostly for resolved enriched • LO + PS can describe the shape but not the normalization Heavy Flavour Production at HERA

13. Charm + dijets in DIS (Q2 >2GeV2) D*±+2 Jets D*±+2 Jets D*± D*± CCFM NLO DGLAP (massive) • both NLO QCD (massive) and CASCADE (CCFM) describe the cross section though CASCADE overeshoots high and Heavy Flavour Production at HERA

14. Charm + dijets in DIS (Q2 >2GeV2) • NLO pQCD: no need for additional resolved photon (photon PDF) • NLO pQCD: NLO not sufficient? • CASCADE: kt distribution too large? • comparion with gluon extracted from inclusive F2 Heavy Flavour Production at HERA

15. F2cc • measure displacement of tracks from the primary vertex using the vertex detector • consistent results with H1 and ZEUS D* measurements • differences in NLO QCD predictions mostly at low Q2 Heavy Flavour Production at HERA

16. F2cc • precise charm data • consistent with QCD predictions Heavy Flavour Production at HERA

17. Extraction of F2bb • F2bb • Large differences in NLO QCD predictions from inclusive fit mostly at low Q2 • Data errors large – consistent with all QCD predictions • F2qq / F2 • charm: ~ 15 – 30% • beauty: ~ 0.3 – 3.5% Heavy Flavour Production at HERA

18. b Production Cross Section Comparison withpQCD NLO • Independent methods - constrained visible region • Differences concentrated in specific parts of phase space NLO predictionsstill below the data in all cases both in and DIS Heavy Flavour Production at HERA

19. Summary plenty of studies on the production mechanism currently measure access charm: • reasonable description by pQCD • data reach precision to have impact on PDF fits beauty: still limited by statistics Impressive first measurements from HERA-II will be available soon! Heavy Flavour Production at HERA

20. Charm Production in DIS CCFM NLO DGLAP (massive) • both NLO QCD (massive) and CASCADE (CCFM) describe the cross section • shape of distribution is well described only by CASCADE Heavy Flavour Production at HERA

21. Extraction of F2cc • Signed impact parameter significance define highest significance tracks subtract the negative bins from the positive to reduce sensitivity to resolution of δ and light quark normalisation Heavy Flavour Production at HERA

22. Extraction of F2cc • earlier measurements: • c tagging by fully reconstructed D* mesons • extrapolation to full pT, η space • measure displacement of tracks from the primary vertex using the vertex detector • c, b have large positive impact parameter • light flavours have symmetric small positive and negative impact parameters Heavy Flavour Production at HERA

23. Extraction of F2cc • precise charm data • confirm fusion picture • constrain gluon distribution Heavy Flavour Production at HERA