1. 1 Outline: HERA, H1 and ZEUS open beauty and charm photoproduction open charm spectroscopy charmonium production summary and conclusions A. Bertolin Heavy flavour production and spectroscopy at HERA

2. 2 HERA, H1 and ZEUS: a brief introduction e p collider at high CMS energy (like having an about 50 TeV e beam on fixed target) two large multipurpose experiments: H1 and ZEUS running ended mid 2007 after about 2500 days of activity and 470 pb -1 of integrated luminosity per experiment

3. 3 Open beauty and charm production at HERA main process: direct boson gluon fusion 0.8 < x obs < 1 other processes: resolved processes 0 < x obs < 0.8 photoproduction (PHP) regime scattered electron is undetected Q 2 < 1 GeV 2 key points: m Q (or E T jet …) >> QCD region of applicability of pQCD collinear vs. k T parton dynamics

4. 4 fully inclusive beauty tag with 2 jet events Open beauty and charm PHP at HERA exploits the large lifetime of b/c hadrons with respect to light hadrons silicon microvertex detector to have a good measurement of can measure beauty AND charm at the same time Significance =

5. 5 fully inclusive beauty tag with 2 jet events x obs peaks at 1 BGF is dominant what is called resolved- in the Pythia collinear MC is also reproduced in the Cascade k T MC without the need of a resolved- component … NLO QCD had is slightly underestimating the data for beauty but NLO QCD is as good for charm as for beauty … scale set by the jets p t Open beauty and charm PHP at HERA

6. 6 likelihood function based on 5 discriminant variables: dE/dx E EMC / E CAL E CAL / p track electron p t w.r.t. the associated jet axis azimuthal angle difference between the electron and the missing transverse momentum vector (// for signal) beauty tag with two jets and one associated semileptonic electron bkg enrichedc enrichedb enriched Open beauty and charm PHP at HERA

7. 7 beauty tag with two jets and one associated semileptonic electron NLO QCD is as good for charm as for beauty PYTHIA gives a fair description of the shapes but the normalization is significantly wrong … missing NLO corrections … Open beauty and charm PHP at HERA beauty charm

8. 8 beauty tag with D * + (no jets) Open beauty PHP at HERA unlike-sign D * like-sign D * beautycharm beauty

9. 9 many very different experimental methods in fair agreement can measure down to ~ 5 GeV (~ m b ) and up to ~ 25 GeV data are already as precise as theory … need more accurate theoretical predictions most recent points are right on top of the NLO predictions … Open beauty PHP at HERA

10. 10 Open charm production at HERA charm spectroscopy at HERA:

11. 11 Open charm production at HERA basic building blocks: D * K s D K D 0 K

12. 12 Open charm production at HERA: D * cross sections Pythia collinear massive fails Pythia collinear mass less fails (except for ) Cascade k T fails (except p t shape) NLO is quite reasonable except for lots of beautiful data but theory is poor … may be NLO is on the right track …

13. 13 Open charm production at HERA excited charm mesons: D 0 1 / D *0 2 D * D *0 2 D in this particular decay mode difficult to separate D 0 1 and D *0 2 due to spin parity conservation D 0 1 can NOT decay in this mode excited charm strange mesons: D s1 D * K s D s1 D 0 K

14. 14 Open charm production at HERA tabular summary: hopefully errors will be reduced extending the analysis to HERA II data and using microvertex detector data (available also for ZEUS in HERA II) the HERA rates are in reasonable agreement with those measured in others (e + e - ) experiments

15. 15 Charmonium production at HERA (1S) and S direct CS model 0.2 < z < 0.9 p-rest frame: z = E E( ) direct CO model this particular diagram: 0.2 < z < 0.9 more typical ones: z > 0.9 resolved CS model z < 0.2 open issues: size of the CO contributions collinear vs. k t parton dynamics (as in the CASCADE MC)

16. 16 < 1/10 of the total available luminosity (2S) to S cross section ratio consistent with being flat (2S) S X contribution NOT subtracted from the data … not easy experimentally ! 15 % increase of the J/ cross section other contributions: diffractive charmonium: suppressed restricting the z – p t J phase space charmonium from B mesons decay: much smaller than at TEVATRON contribution: tiny at HERA Charmonium production at HERA (1S) and S

17. 17 J/ cross section measurements PHP regime: NLO CS calculation with LARGE scale uncertainties describes the shapes LO CS + k t factorization (CASCADE) describes the data well LO CS + collinear factorization (EPJPSI) fine in shape DIS regime (3.6 < Q 2 < 100 GeV 2 ): no NLO prediction LO CS + k t factorization (CASCADE) describes the data well LO CS + collinear factorization (EPJPSI) fine in shape

18. 18 J/ cross section measurements PHP regimeDIS regime d dp 2 T for different z rages d 2 dp 2 T dz should be a stringent test of the matrix elements involved … would be nice to have NLO predictions as well … LO CS + k t factorization (CASCADE) describes the data well

19. 19 J/ helicity at HERA helicity: study of the angular distributions in the J/ rest frame learn about production channels contrary to TEVATRON at HERA mostly prompt J/ … cleaner environment can measure 2 out of 3 helicity parameters BKV collinear factorization Baranov CS LO CS k t factorization large differences in the predictions (sign is different …) none of the predictions is able to describe simultaneously all measurements …

20. 20 Conclusions several beauty inclusive measurements have been performed and will be refined in the immediate future … almost fully reconstructed final states (like D * + ) have also been measured measurements are not easy due to the small beauty cross section at HERA remarkably enough all measurements are giving a rather consistent picture on the experimental side in general beauty production is reasonably well described by NLO even at small p T b charm and charmonium states are produced copiously at HERA inclusive as well as precise exclusive final state measurements are available … can also perform charm spectroscopy at HERA in the presence of a reasonably large scale (E T jet >> m C ) NLO QCD is as good for open charm as for open beauty charmonium production at HERA is well described by the CASCADE MC with k T factorization … but polarization is not well described … looking forward to better theoretical predictions …

21. 21 Alessandro Bertolin (Padova) "Heavy flavour production and spectroscopy at HERA" Lorenzo Bellagamba (Bologna) "Search for new physics at HERA" Jan Figiel (Inst. of Nucl. Physics, Krakow) "Measurements of diffraction at HERA Hans-Christian Schultz-Coulon, Heidelberg University "Structure Function Measurements at HERA" Guenter Grindhammer, MPI Munich "Jet Production and alpha_s Measurements at HERA" Heavy flavour production and spectroscopy at HERA