1. B. Naroska Un. Hamburg Beauty at HERA HEP05 Lisbon 21/07/2005 1 Beauty Production at HERA HEP05 International Europhysics Conference on High Energy Physics EPS in Lisbon, Portugal. 21-27 July, 2005 Beate Naroska (Univ. Hamburg) Outline  Jets + Muons (H1, ZEUS)  D*muon (H1,ZEUS)  Di-muon (ZEUS)

2. B. Naroska Un. Hamburg Beauty at HERA HEP05 Lisbon 21/07/2005 2 Heavy Quark Production at HERA At HERA heavy quarks mainly produced via photon-gluon fusion: γg→bb, cc in photoproduction c & b are produced rarely w.r.t. u, d, s ; also c ≈ 200 * b. Cross sections directly sensitive to gluon density in the proton Contributions from hadronic component of the photon expected: which and how much? TESTS OF QCD AND PROTON/ PHOTON STRUCTURE

3. B. Naroska Un. Hamburg Beauty at HERA HEP05 Lisbon 21/07/2005 3 Theoretical Description NLO calculations in massive schemes: FMNR photoproduction ( hadronic resolved component small) ( Frixione, Mangano, Nason, Ridolfi) HVQDIS DIS (no resolved component) (Harris, S mith) LO-ME+PS models used: PYTHIA photoproduction (DGLAP) ( excitation+hadronic resolved) (Bengtsson, Sjostrand) CASCADE photoproduction (CCFM) (no resolved component) RAPGAP electroproduction (no resolved component) (H.Jung) Example: HVQDIS

4. B. Naroska Un. Hamburg Beauty at HERA HEP05 Lisbon 21/07/2005 4 Muon + Jet Events Select events with jets E T >6,7 GeV muon pT>2.5 GeV possibly scattered electron use P T rel and/or impact parameter δ to enrich and determine b fraction H1, ZEUS final: hep-ex/0502010; hep-ex/0405069;hep-ex/0312057 b fraction extracted by fit to P T rel (ZEUS) δ, PTrel (H1)

5. B. Naroska Un. Hamburg Beauty at HERA HEP05 Lisbon 21/07/2005 5 Muon + Jet Events) H1 and ZEUS Photoproduction Results ( Muon + Jet Events)  Good agreement H1-ZEUS  ZEUS no excess at low pTmu  Reasonable agreement with NLO calculations

6. B. Naroska Un. Hamburg Beauty at HERA HEP05 Lisbon 21/07/2005 6 Results DIS Muon + Jet Events p T (µ) excess H1 and ZEUS η µ excess mainly in forward direction µ

7. B. Naroska Un. Hamburg Beauty at HERA HEP05 Lisbon 21/07/2005 7 multi-tagged bb event no lifetime info used at present Double Tag : Motivation and goals Two tag strategies: D*µ (H1 final, ZEUS prel.) µµ (ZEUS Prel. NEW) New No Jets: phase space of b production reaches to low p T (b)

8. B. Naroska Un. Hamburg Beauty at HERA HEP05 Lisbon 21/07/2005 8 H1: D*μ correlations Data sample L = 89 pb -1 HERA I data, 97-00 Exploit el. charges of D*/µ to separate b events from charm and light quark background like-sign unlike-sign and separation in azimuth ΔΦ or ΔR (D*µ ) or use inv. mass Mµµ and +- ++/- -

9. B. Naroska Un. Hamburg Beauty at HERA HEP05 Lisbon 21/07/2005 9 D*μ correlations D* yield measured from the ΔM technique : ΔM = m Kππs – M Kπ Extract N(D*μ) from fit to Gaussian peak + background : N(D*μ) = 151 ± 22 ‘2D fit’ – simultaneous likelihood fit to ΔM in 4 correlation regions to extract c and b contributions D* peak and background shape from 1D fit 6 free parameters: N c, N b and four background regions (χ 2 = 145.5 / 154 d.o.f)

10. B. Naroska Un. Hamburg Beauty at HERA HEP05 Lisbon 21/07/2005 10 V. good agreement between 2D fit and individual 1D fits N c = 53 ± 12 N b = 66 ± 17 Use these to calculate visible cross sections for : σ c vis (ep → e D* μ X)=250±57±40 pb (NLO: 286+159-59) σ b vis (ep → e D* μ X)=206±53±35 pb (NLO: 52+14-9) Fit Result Charm: good agreement Beauty: data too high Visible kinematic region : p T (D*) > 1.5 GeV; |η(D*)| 2 GeV; |η(μ)| < 1.735; 0.05 < y < 0.75; Q 2 < GeV 2.

11. B. Naroska Un. Hamburg Beauty at HERA HEP05 Lisbon 21/07/2005 11 D*μ – (N)LO FMNR comparisons Expected deviations from LO due to higher order effects – flatter p T distribution and broader ΔΦ peak. Good agreement with NLO calculation Normalized Cross Sections!

12. B. Naroska Un. Hamburg Beauty at HERA HEP05 Lisbon 21/07/2005 12 D*μ – PYTHIA & CASCADE MC comparisons Both MCs give a good description of the data NB: Although different approaches to parton evolution are taken, the differences are smaller than the experimental errors

13. B. Naroska Un. Hamburg Beauty at HERA HEP05 Lisbon 21/07/2005 13 beauty BH + J/   +  ' charm LF background ZEUS di-  Events Aim: Total Cross Section Selection of muons with p T >1.5 (0.75) GeV Total calorimetric E T (θ>10 o ) >8 GeV (+implicit p T, η cuts; cleaning cuts) Remove J/ψ, ψ’, etc: Non isolation of muons less than 250 MeV around muons (2 GeV in charmonium regions) good MC descriptionLOW MASSHIGH MASS Data sample L = 121 pb -1 HERA I data, 96-00

14. B. Naroska Un. Hamburg Beauty at HERA HEP05 Lisbon 21/07/2005 14 Signal extraction:  use non-isolated µ pairs, all inv. masses  Use data for background determination fake muon background removed by taking difference between like-sign and unlike sign samples (light flavour cancels) charm contribution estimated with D*µ sample ZEUS:Signal Extraction Example of breakdown into contributions and agreement with MC: non-isolated unlike-sign µ pairs

15. B. Naroska Un. Hamburg Beauty at HERA HEP05 Lisbon 21/07/2005 15 For NLO comparison: two µ’s from different b’s M µµ >3.25 GeV (PhP +DIS) ZEUS µµ Events : Results More restrictive cuts on muons (p T >1.5 GeV, -2.2<η<2.5)

16. B. Naroska Un. Hamburg Beauty at HERA HEP05 Lisbon 21/07/2005 16 Comparison to NLO Calculations (Muon + Jet Events) Data in general above NLO pQCD up to 2 s.d. Good agreement between H1 and ZEUS

17. B. Naroska Un. Hamburg Beauty at HERA HEP05 Lisbon 21/07/2005 17 D*µ ZEUS PhP (rap.b<1, y range) D*µ H1 (vis.) D*µ ZEUS DIS (rap.b<1, y range) µµ ZEUS PhP +DIS tot. H1+ZEUS : Beauty from D*µ and Di-µ Events: NLO

18. B. Naroska Un. Hamburg Beauty at HERA HEP05 Lisbon 21/07/2005 18Summary  Beauty results HERA I with jets and muon final  B Cross sections tend to be above NLO pQCD calculations  Shapes of differential distributions deviate from QCD only in few places (e.g. forward, low p Tµ )  Double Tag Analyses started: D*µ, µµ - stat. limited reach to low p T (b)– total cross section possible  Measured cross sections higher than NLO QCD  Shape of Differential Distributions described: NLO effects visible

19. B. Naroska Un. Hamburg Beauty at HERA HEP05 Lisbon 21/07/2005 19 ZEUS : Beauty from Di-µ Events

20. B. Naroska Un. Hamburg Beauty at HERA HEP05 Lisbon 21/07/2005 20 Signal extraction: charm contribution estimated by D*mu sample fake muon backgrnd removed by taking difference between like-sign and unlike sign samples (light flavour cancels) ZEUS: Muon p T and  distributions non-isolated unlike-sign µ pairs ΔΦ Purity ~40-50%