Extracting the Strange Density from xF3xF_3

We present a QCD analysis of the strange and charm contributions to the neutrino deep inelastic structure function $xF_3$. We show that next-to-leading order effects, which are relatively important for $F_2$, play a lesser role in the case of $xF_3$. The neutrino--antineutrino difference $xF_3^{\nu} - xF_3^{\bar \nu}$ provides a new determination of the strange density, which exhibits some advantages with respect to other traditional methods.Comment: 12 page

Coefficient Functions and Open Charm Production in Deep Inelastic Scattering

It is shown that the problem of double counting in open charm production in DIS can be solved by using the expression for DIS coefficient functions in terms of 2PI diagramsComment: 11 pages, REVTeX, no figure

Heavy-quark contributions to the ratio F_L/F_2 at low x

We study the heavy-quark contribution to the proton structure functions F_2^i(x,Q^2) and F_L^i(x,Q^2), with i=c,b, for small values of Bjorken's x variable at next-to-lading order and provide compact formulas for their ratios R_i=F_L^i/F_2^i that are useful to extract F_2^i(x,Q^2) from measurements of the doubly differential cross section of inclusive deep-inelastic scattering at DESY HERA. Our approach naturally explains why R_i is approximately independent of x and the details of the parton distributions in the small-x regime.Comment: 11 pages, 1 figur

Single-top production at future ep colliders

The production of top quarks in single mode at future ep colliders is studied, the attention being mainly focused to the case of the proposed LEPXLHC collider. We are motivated to reanalyse such a process following the discovery of the top quark at Fermilab. Thanks to the measurement of its mass one is now able to establish more accurately the relevance of single top production for itself and for many other processes to which it may act as a background. In addition, the recent improvement of our knowledge of the quark and gluon dynamics inside the proton now allows one to pin down the dependence of single top production on the partonic structure functions. Both the leptonic and hadronic decay channels of the top quark are studied and compared to the yield of the corresponding irreducible background in presence of b-taggingComment: 28 pages, latex, epsfig, 10 postscript figures, complete paper available at ftp://axpa.hep.phy.cam.ac.uk/moretti/cavendish_9704 and at http://www.hep.phy.cam.ac.uk/theory/papers

The Distribution of Constituent Charm Quarks in the Hadron

Using a statistical approach in the framework of non-covariant perturbation theory the distributions for light and charmed quarks in the hadron have been derived, taking into account the mass of the charmed quark. The parameters of the model have been extracted from the comparison with NA3 data on hadroproduction of J/psi particles. A reanalysis of the EMC data on charm production in muon-nucleon scattering has been performed. It has been found in comparison with the conventional source of charmed quarks from photon-gluon fusion, that the EMC data indicate the presence of an additional contribution from deep-inelastic scattering on charmed quarks at large x. The resulting admixture of the Fock states, containing charmed quarks in the decomposition of the proton wave function is of the order of 1%. The approach presented for the excitation of the Fock states with charmed quarks can also be applied to states with beauty quarks as well as to the hadronic component of the virtual photon (resolved photon component).Comment: 23 pages, 4 PostScript figures, Latex2e. In revised version in comparison with the original one all (?) mistypings have been corrected, one more thank has been added and the comparison of the pion and the proton J/psi production is described in more detai

Charm Contribution to the Structure Function in Diffractive Deep Inelastic Scattering

The charm contribution to the structure functions of diffractive deep inelastic scattering is considered here within the context of the Ingelman-Schlein model. Numerical estimations of this contribution are made from parametrizations of the HERA data. Influence of the Pomeron flux factor is analized as well as the effect of the shape of the initial parton distribution employed in the calculations. The obtained results indicate that the charm contribution to diffractive deep inelastic process might be large enough to be measured in the HERA experiments.Comment: 16 pages, RevTeX, 6 figures, to be published in Physical Review

Leptoproduction of Heavy Quarks II -- A Unified QCD Formulation of Charged and Neutral Current Processes from Fixed-target to Collider Energies

A unified QCD formulation of leptoproduction of massive quarks in charged current and neutral current processes is described. This involves adopting consistent factorization and renormalization schemes which encompass both vector-boson-gluon-fusion (flavor creation) and vector-boson-massive-quark-scattering (flavor excitation) production mechanisms. It provides a framework which is valid from the threshold for producing the massive quark (where gluon-fusion is dominant) to the very high energy regime when the typical energy scale \mu is much larger than the quark mass m_Q (where the quark-scattering should be prevalent). This approach effectively resums all large logarithms of the type (alpha_s(mu) log(mu^2/m_Q^2)^n which limit the validity of existing fixed-order calculations to the region mu ~ O(m_Q). We show that the (massive) quark-scattering contribution (after subtraction of overlaps) is important in most parts of the (x, Q) plane except near the threshold region. We demonstrate that the factorization scale dependence of the structure functions calculated in this approach is substantially less than those obtained in the fixed-order calculations, as one would expect from a more consistent formulation.Comment: LaTeX format, 29 pages, 11 figures. Revised to make auto-TeX-abl

Global QCD Analysis and the CTEQ Parton Distributions

The CTEQ program for the determination of parton distributions through a global QCD analysis of data for various hard scattering processes is fully described. A new set of distributions, CTEQ3, incorporating several new types of data is reported and compared to the two previous sets of CTEQ distributions. Comparison with current data is discussed in some detail. The remaining uncertainties in the parton distributions and methods to further reduce them are assessed. Comparisons with the results of other global analyses are also presented.Comment: (Change in Latex style only: 2up style removed since many don't have it.) 35 pages, 23 figures separately submitted as uuencoded compressed ps-file; Michigan State Report # MSU-HEP/41024 and CTEQ 40

Hard-scattering factorization with heavy quarks: A general treatment

A detailed proof of hard scattering factorization is given with the inclusion of heavy quark masses. Although the proof is explicitly given for deep-inelastic scattering, the methods apply more generally The power-suppressed corrections to the factorization formula are uniformly suppressed by a power of \Lambda/Q, independently of the size of heavy quark masses, M, relative to Q.Comment: 52 pages. Version as published plus correction of misprint in Eq. (45

Revisiting the Bs(∗)B^{(*)}_s-Meson Production at the Hadronic Colliders

The production of heavy-flavored hadron at the hadronic colliders provides a challenging opportunity to test the validity of pQCD predictions. There are two mechanisms for the $B^{(*)}_s$ hadroproduction, i.e. the gluon-gluon fusion mechanism via the subprocess $g+g\rightarrow B^{(*)}_s+b+\bar{s}$ and the extrinsic heavy quark mechanism via the subprocesses $g+\bar{b}\to B^{(*)}_s +\bar{s}$ and $g+s\to B^{(*)}_s +b$, both of which shall have sizable contributions in proper kinematic region. Different from the fixed-flavor-number scheme (FFNS) previously adopted in the literature, we study the $B^{(*)}_s$ hadroproduction under the general-mass variable-flavor-number scheme (GM-VFNS), in which we can consistently deal with the double counting problem from the above two mechanisms. Properties for the $B^{(*)}_s$ hadroproduction are discussed. To be useful reference, a comparative study of FFNS and GM-VFNS is presented. Both of which can provide reasonable estimations for the $B^{(*)}_s$ hadroproduction. At the Tevatron, the difference between these two schemes is small, however such difference is obvious at the LHC. The forthcoming more precise data on LHC shall provide a good chance to check which scheme is more appropriate to deal with the $B^{(*)}_s$-meson production and to further study the heavy quark components in hadrons.Comment: 18 pages, 8 figures, 4 tables. To match the published version. To be published in Eur.Phys.J.