1 / 19

H1 and ZEUS R esults on B eauty P roduction   

H1 and ZEUS R esults on B eauty P roduction   . Isabell-Alissandra Melzer-Pellmann DESY Hamburg, ZEUS XXXIXth Rencontres de Moriond QCD and High E nergy H adronic Interactions March 28th - April 4th, 2004. Outline. Introduction and Theory

nikki
Télécharger la présentation

H1 and ZEUS R esults on B eauty P roduction   

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. H1 and ZEUS Results on Beauty Production    Isabell-Alissandra Melzer-Pellmann DESY Hamburg, ZEUS XXXIXth Rencontres de Moriond QCD andHigh Energy HadronicInteractions March 28th -April 4th, 2004

  2. Outline • Introduction and Theory • Measurement techniques and Results (gP and DIS) • Jets + m • D*m correlations • Summary and Outlook

  3. Introduction: HERA p e Maximum centre of mass energies: s = 300 GeV (1992-1997) s = 318 GeV (1998-2000) Luminosity (1996-2000): e+p scattering: L  100 pb-1 e-p scattering: L  15 pb-1

  4. Theory:Beauty production at HERA • Driven by gluons in the proton • Kinematic regions dependent on the virtuality of the photon Q2: • Photoproduction (gP): Q2 < 1GeV2 • Hard scales: mb, pT Deep inelastic scattering (DIS): Q2 > 1GeV2 • Hard scales: mb, Q2, pT b b • Always more than one hard scale for as available • perturbative QCD should work…

  5. Theory:Description in pQCD Factorisation: Photon structure  Matrix element  Proton structure Photon structure: Role of resolved photons in beauty production? • QCD models • compared to data: • LO O(as) + parton shower: • Pythia MC (DGLAP) • Cascade MC (CCFM) • NLO O(as2) : • gP: FMNR • DIS: HVQDIS Hard ME Proton structure: Test pQCD approximation for gluon radiations: DGLAP, BFKL, CCFM

  6. Measurement technique:B -> mjjX Large B mass: A pT of m relative to the closest Jet is larger Large B lifetime: Am impact parameter d H1 gP (prel.): Combined max Likelihood fit (d, pT ): fb=30.72.5 % rel

  7. Results: B -> mjjX in Photoproduction Pseudorapidity • NLO is in good agreement with data • H1 slightly higher than ZEUS (agreement within errors)

  8. gP: Comparison of NLO QCD and LO+PS NLO QCD as well as LO + Parton shower MC describe the data reasonably well (MC below data for high hm and high pT)

  9. gP: Comparison NLO QCD and LO+PS for xg jets • tool to measure photon-gluon • fusion (peak at xg =1) in • comparison to other contributions • (e.g. gluon-gluon fusion or higher • order diagrams (photon structure, • distributed over the whole range) jets NLO QCD: good description of data Pythia: good description (large contribution from flavour excitation at low xg ) Cascade: underestimates data at low xg (generation of these events via initial state radiation without using a parton density in the photon) jets jets

  10. Results: B -> mjX in DIS • Jet variables: • Jets in Breit frame: • + 2x P = 0 • : momentum of exchanged photon x: Bjorken x P: Proton momentum Space-like photon and proton collide head-on Jet variable: ZEUS : sep = (40.9  5.7stat-4.4 sys) pb NLO QCD (HVQDIS): sep = 20.6 –2.2 pb Cascade (CCFM): sep = 28 pb RAPGAP (DGLAP): sep = 14 pb +6.0 vis +3.1 vis vis vis Isabell-A. Melzer-Pellmann Moriond QCD, 28.3.-4.4.2004

  11. DIS: Results for DIS variables (Q2, log10(x)) DIS variables: NLO QCD and Cascade (CCFM) describe data reasonably well, Rapgap (DGLAP) underestimates cross sections. Data slightly higher than NLO QCD (2s) at small Q2 and at small x.

  12. DIS: Results for m variables (pT, hm) m m Variables: NLO QCD and Cascade (CCFM) describe data reasonably well, Rapgap (DGLAP) underestimates cross sections. Data slightly higher than NLO QCD (2s) at small pT. m

  13. Measurement technique:D*m correlations Beauty Charm Separation by angular and charge correlations: • DF 90°-180°, unlike charge DF 0°- 90°, unlike charge DF 90°- 180°, unlike charge DF 90°- 180°, like charge

  14. Results:D*m correlations like charge unlike charge ZEUS: H1: incl. data: sep = (380  120stat  130sys) pb incl. data: sep = (214  52stat -84 sys) pb vis vis +96 Visible cross sections for H1 and ZEUS agree within errors.

  15. Event display:D*m correlations m- m- ps p- p e+ ps K+ p- e+ K+ e+

  16. Summary:Beauty at HERA • H1 and ZEUS performed various measurements • in different kinematic regions: • NLO QCD is in general in good agreement with data in most phase space regions, small discrepancies in some regions have been identified: • gP: NLO QCD in good agreement for all regions, LO + PS models slightly below data for high hm and high pT • DIS: NLO QCD underestimates rate for high ET,jet, low Q2, low x, low pT and high hm. LO + PS models behave similar. m m Breit

  17. Outlook • HERA I has come close to the sleeping beauty… • measurements of beauty cross sections require more data to really judge agreement with pQCD • HERA II is prepared to • wake the sleeping beauty! • Expect factor 5 higher integrated luminosity • Detector upgrade (ZEUS: microvertex detector) • Improvements on trigger HERA II

  18. BACKUP

  19. Summary plot:Beauty at HERA Recent H1 and ZEUS results imply smaller discrepancy between data and NLO QCD in gP as well as in DIS. DIS gP

More Related