Physics Analysis

Heavy Flavour Physics

• They can be tagged uniquely as quarks, while light quark induced processes can often not be distinguished from gluon induced processes. This gives direct access to the study of the photon-quark (QED) and gluon-quark (QCD) couplings.
• The quark mass (5 GeV or 1.5 GeV) is large enough to provide a "hard scale" for perturbative QCD calculations. The corresponding production processes can therefore always be treated perturbatively with "reliable" predictions. On the other hand, this scale comes in addition to other competing scales, like the tranverse momentum of the quarks, or the virtuality of the photon in deep inelastic scattering reactions. The interference and competition between these scales yields a challenging "playground" for QCD theorists, and a nice opportunity for experimentalists to check, validate, or refute some of the theoretical inputs to these calculations.
• Some aspects of physics beyond the standard model (e.g. anomalous single top production or the production of flavoured leptoquarks) explicitly involve heavy flavours in the final state as part of their signature. The observation of any significant deviations from standard model predictions for heavy flavour production could therefore be evidence for new physics. Although some deviations have been observed in the past, they have so far been attributed either to potential imperfections in the available theoretical calculations and/or their comparison with the data (e.g. historical discrepancies in beauty production) or to statistical fluctuations (differences between charm production in e+ and e- scattering). Nevertheless, some of these differences still need to be finally settled.
• Once Heavy Flavour Production is fully understood, this understanding can be used to
  • reduce the systematic error due to heavy flavours in the context of the extraction of proton structure functions from inclusive deep inlastic scattering.
  • directly acces the gluon distribution in the proton through the process of photon-gluon fusion to two heavy quarks. It is therefore also an important ingredient in the quest to understand "what the proton is made of".

Since fall 2003 ZEUS is taking data again in the framework of the HERA II upgrade program. Apart from increased luminosity, an important upgrade for ZEUS is the installation and use of a new Microvertex-Detector. With this detector, secondary vertices from beauty and charm are now tagged in ZEUS. Combining this with the other tagging methods used so far, with further detector improvements, and with corresponding improvements of the offline reconstruction, the sensitivity for beauty production is being increased by an order of magnitude or more with respect to the HERA I results. First encouraging results have already been obtained.

Contact

Staff:	Achim Geiser achim.geiser@desy.de Fon: +49-40-899837766 Office: 1b/249 (Heavy Flavour working group convener, D*-muon correlation studies)
Fellows and Postdocs:	Ingo Bloch ibloch@mail.desy.de Fon: +49-40-89983159 Office: 1b/259 (b/anti-b correlations from di-muon events)
	Benjamin Kahle kahle@mail.desy.de Fon: +49-40-89983159 Office: 1b/259 (Beauty production from semileptonic decays to muons in deep inelastic scattering)
Ph.D. Students:	Elizabeth Nuncio-Quiroz adriana-elizabeth.nuncio-quiroz@desy.de Fon: +49-40-89983062 Office: 1b/152c (Beauty production from semileptonic decays to electrons)
	Dmitri Gladkovdmitri.gladkov@desy.de Fon: +49-40-89982009 Office: 1b/124
	Elizabeth Nuncio-Quiroz adriana-elizabeth.nuncio-quiroz@desy.de Fon: +49-40-89983062 Office: 1b/152c (Beauty production from semileptonic decays to electrons)