1. Bottom and Charm Quark Production in Two-Photon Collisions at LEP Wilfrid da Silva LPNHE, Paris 17-23 july 2003 J/  production in  collisions (DELPHI) Cross section  e + e -  cc,bb X )  charm tagged by D* ± (L3)  beauty, charm tagged by leptons (DELPHI, L3) Summary EPS2003 Aachen DELPHI Collaboration - -

2. J/  production at LEP2 (DELPHI) e + e -  e + e - J/  X ● Two independent leading processes Data LEP2 = 161-207 GeV, L = 617 pb -1  VDM (pomeron exchange or diffractive dissociation of the photon)  Resolved processes + color octet model : most probable hypothesis. ● MC : PYTHIA 6.156  Select  events  Tag J/   with muon pairs N=36 ± 7 evts Results  Background : J/  coming from bb estimated 2.1 ± 0.6 evts Estimated fraction of resolved processes: 74% ± 22% Rate = N J/  / N vis  = ( 6.7 ± 1.3 (stat) ± 0.2 (syst)) 10 -3  J/  X  = 45 ± 9 (stat) ± 17 (syst) pb N( e+e _  Z   J/  X) < 0.2 evts N(    c2  J/        ) < 0.3 evts Klasen -

3. Direct term Single resolved term  Measurement of  (e + e -  e + e - ccX) and  (e + e -  e + e - bbX) At LEP2 energies direct and single resolved contributions are of the same order ● Two LO main contributions direct and single resolved terms NLO total cross sections computations available Use the 10 years old Drees, Kraemer, Zunft, Zerwas   VDM and double resolved contribution are expected to be smal l ● Open charm and beauty production measurement  provide a good test of PQCD Large m b and m c  more reliable calculations. ● Default MC used in all analyses : PYTHIA /  pdf SaS1D at = 180 GeV - -

4. ● LEP II data = 183 - 209 GeV  L = 683 pb -1 ●     selection and antitagged events Charm tagged by D* ± :   Results : d  /dp T (D* ± ) with |  | < 1.4 and 1. GeV < p T < 12. GeV Extraction of the charm cross section +0.54 Measurement of  (e + e -  e + e - ccX) using D* ± Comparison with PYTHIA LO Frixione NLO MC  (e + e -  e + e - ccX) = ( 1.12 ± 0.09 (stat) ± 0.16 (syst) -0.25 ) nb D* ± Visible region  (e + e -  e + e - D* ± X) vis = 71.2 ± 5.3 (stat) ± 9.8 (syst) pb - D* +  D 0  S +                      -

5. Event selection strategy (for L3 and DELPHI) Select anti-tagged   events Identify a lepton as a signature for semi-leptonic charm and beauty decays Reconstruct jets and compute the sensitive variable ( the lepton transverse momentum with respect to the lepton jet axis) Measurement of  (e + e -  e + e - ccX) and  (e + e -  e + e - bbX) Jet axis computed without the   P T - -

6. Fitting strategy ● Data LEP2 = 189-209 GeV, L =413 pb -1 Charm and beauty contributions well separated in p T distribution Charm Beauty Result Use muons  N bb fit parameter variable  estimated background from MC  fixed by LEP average charm cross section  N uds contribution estimated from the data      one variable fit Measurement of  (e + e -  e + e - bbX)  -

7. ● Data = 189 – 209 GeV  L = 627 pb -1  ● Use muons and electrons ●   : 3 variable fit N bb, N cc, N uds   (e + e -  e + e - bbX) muons = 13.0 ± 2.3 (stat) ± 2.3 (syst) pb    (e + e -  e + e - bbX) electrons = 12.6 ± 2.4 (stat) ± 2.3 (syst) pb  result in agreement with L3 previous measurement  Measurement of  (e + e -  e + e - ccX) and  (e + e -  e + e - bbX) Muons Electrons  Upgrade of their previous measurement  Results   and e tag results are consistent  (e + e -  e + e - bbX) combined = 12.8 ± 1.7 (stat) ± 2.3 (syst) pb  as a subproduct of the control test of the charm sample    (e + e -  e + e - ccX) combined = 998 ± 117 (stat) pb (in agreement with L3 previous measurement )  Charm Beauty - - - - - -

8. Identify a K in lepton jet with RICH and TPC K-lepton charge correlations for beauty or charm enrichment Measurement of  (e + e -  e + e - ccX) and  (e + e -  e + e - bbX) cc : K + l - charge correlation fix N bb : value given by the previous measurement fit N cc bb : K + l + charge correlation fix N cc : value given by LEP average fit N bb  in agreement with previous DELPHI measurement - - - - -

9. Summary New results from DELPHI with K-lepton charge correlations for the first time in  physics Single resolved processes are needed to describe the data Measurement of  (e + e -  e + e - ccX) and  (e + e -  e + e - bbX) Consistent LEP results DELPHI confirms the L3 and OPAL beauty excess - - Good agreement with QCD Drees, Kraemer, Zunft, Zerwas