Charm Quark Jet Research Articles

Ideas for a vertex detector at the future e+e− linear collider

Abstract The LCFI Collaboration has been formed in order to study all aspects of heavy flavour identification at future e + e − linear colliders in the TeV energy region. Over several years of work it has become clear that this environment, characterized by multi-jet events potentially rich in new physics processes, will provide unprecedented opportunities and challenges for detectors in general, and for vertex detectors in particular. Fortunately, as already seen at SLC, the linear collider environment lends itself to extremely powerful pixel-based vertex detectors. The particular characteristics of the TeV-scale machine will permit a small diameter beam-pipe at the interaction region. This, coupled with ongoing developments which will lead to even greater reduction in detector thickness, should permit the very high efficiency and purity for heavy flavour identification (charm and bottom quark jets) needed to satisfy the most challenging physics requirements. This paper describes plans for an R&D programme which will address the critical problems associated with the design of a detector matched to these requirements.

Production of charm quark jets in DIS diffractive dissociation

We present a calculation of open charm quark production in diffractive deep inelastic electron-proton scattering in a perturbative QCD framework. The cross section is proportional to the square of the gluon density and explicitly displays breaking of Regge factorization. Jet cross sections as well as the charm contribution to the diffractive structure function are calculated. As a consequence of the steep rise of the gluon density at small x the charm contribution to $F_2^{D}$ rises with decreasing x_P.

On the helicity of charm jets

We discuss the determination of initial quark polarization from the characteristics of the jet it gives rise to, since theory indicates that quark-antiquark pairs produced ine− e+ annihilation have a large polarization correlation and that individual quarks have longitudinal polarization due to γ-Z0 interference. On the basis of a model calculation, we deduce that the mean value of\(S_c \cdot \hat P_D \times \hat P_\pi \) for charm quark jets, averaged over theD*(2010), can be non zero and is then a measure of the initial quark helicity. Expectation values are, however, very small, for reasons which are discussed. The extension tob andt quarks is briefly considered.

Comparison of light quark and charm quark fragmentation

Separate samples of charm quark and light quark (u, d, s) jets have been isolated in an experiment studying e +e − annihilations at s = 29 GeV . The results come from data corresponding to an integrated luminosity of 111 pb −1 collected by the High Resolution Spectrometer. Differences were observed in charged multiplicities, momentum distributions, and rapidity of the size expected from the different fragmentation functions and leading particle decay properties of the two samples.