1 / 27

Jets in ep collisions at HERA

Jets in ep collisions at HERA. Alexander A. Savin. on behalf of the H1 and ZEUS collaborations. Hadron Structure and QCD 2004, 18-22 May 2004, St.Petersburg, Russia. Kinematic variables. e +(-). p. (820). Photon virtuality.  * P center-of-mass energy squared. inelasticity.

portia-roman
Download Presentation

Jets in ep collisions at HERA

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. Jets in ep collisions at HERA Alexander A. Savin on behalf of the H1 and ZEUS collaborations Hadron Structure and QCD 2004, 18-22 May 2004, St.Petersburg, Russia

  2. Kinematic variables e+(-) p (820) Photon virtuality *P center-of-mass energy squared inelasticity Bjorken scaling variable ep enter-of-mass energy squared

  3. Jets at HERA 1 jet QCD Compton Boson-gluon fusion 2 jets

  4. Three jets

  5. Events simulation LO: ARIADNE LEPTO PYTHIA RAPGAP Parton Level Hadron Level CDM+LUND etc GEANT Detector Simulation NLO: DISENT DISASTER++ MEPJET NLOJETS Uncertainties: pdf hadronisation detector

  6. Breit Frame Jet Finding i j Longitudinally invariant kT cluster algorithm DIS Event Lab Frame Breit Frame Inclusive mode, combine if: PT Exclusive mode: PL Breit Frame combine until

  7. DGLAP vs BFKL DGLAP: BFKL: no ordering in k T Unordered parton evolution, e.g. CCFM (Cascade) Different parton-shower models: BFKL/DGLAP-like Ariadne/LEPTO

  8. Real and virtual photon structure High Pt jets at Pt > Q probe the photon structure. direct resolved In the BFKL both are taken in account due to arbitrary ordering of the kT

  9. Real photon structure: inclusive jet PHP at high Et Non-perturbative effects: multiple interactions and hadronisation are small Comparison with NLO H1

  10. Real photon structure: dijet PHP with charm ZEUS

  11. Virtual photon structure: dijet DIS at hight Et Comparison with NLO ZEUS

  12. Virtual photon structure: dijet DIS at hight Et Comparison with Herwig and Cascade H1

  13. Virtual photon structure: dijet DIS with charm ZEUS

  14. Structure of the proton • Uncertainties: • -NLO QCD due to terms beyong NLO; • NLO QCD due to • -statistical and correlated systematic • uncertainties(fits); • -hadronisation etc. PDF New results on PDFs using jets in global PDF fits!

  15. Structure of the proton: inclusive jets in DIS ZEUS

  16. Structure of the proton: jets in the PDF fit Use jet data to tie down the high-x region in PDF analysis The improvement in the determination of the gluon distribution at moderate to high-x is striking

  17. Structure of the proton: inclusive jets in DIS H1

  18. Forward jets DGLAP The probability for is low BFKL Low xBj,high Q2, high pt,jet2 in the p-direction H1

  19. Forward jets Comparison with NLO ZEUS to suppress

  20. Interjet energy flow Dijet events with Rapidity Gap H1 All Dijet events Color singlet added g-remnant P- remnant 2p Jet R Gap Jet R 0 -2.4 2.4 h

  21. Multijet production Ratios: R2/1 and R3/2 ZEUS

  22. Multijet production: ratio 3jets/2jets

  23. Jets substructure kT inclusive - for jets kT exclusive - for subjets At high ET,jet and ycut not too low, fragmentation effects are small – subjet multiplicity in pQCD

  24. Jets substructure ZEUS PHP and DIS

  25. measurements

  26. at HERA

  27. Conclusions Considerable progress in jets studying in ep: precise measurements, NLO etc In many cases the theoretical uncertainties are still dominant One may expect more new information about photon and proton pdfs by including more jet data in global PDF fits.

More Related