285 research outputs found
Determination of from Gross-Llewellyn Smith sum rule by accounting for infrared renormalon
We recapitulate the method which resums the truncated perturbation series of
a physical observable in a way which takes into account the structure of the
leading infrared renormalon. We apply the method to the Gross-Llewellyn Smith
(GLS) sum rule. By confronting the obtained result with the experimentally
extracted GLS value, we determine the value of the QCD coupling parameter which
turns out to agree with the present world average.Comment: invited talk by G.C. in WG3 of NuFact02, July 1-6, 2002, London; 4
pages, revte
Charm quark and D^* cross sections in deeply inelastic scattering at DESY HERA
A next-to-leading order Monte Carlo program for the calculation of heavy
quark cross sections in deeply inelastic scattering is described. Concentrating
on charm quark and D^*(2010) production at HERA, several distributions are
presented and their variation with respect to charm quark mass, parton
distribution set, and renormalization-factorization scale is studied.Comment: 15 pages including 8 figures. Uses Latex, Revtex, and psfig.
References added - others updated. Several sentences/words added for clarity.
Results/conclusions unchanged. To appear in Phys. Rev.
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
Next-to-Leading Order Cross Sections for Tagged Reactions
We extend the phase space slicing method of Giele, Glover and Kosower for
performing next-to-leading order jet cross section calculations in two
important ways: we show how to include fragmentation functions and how to
include massive particles. These extensions allow the application of this
method to not just jet cross sections but also to cross sections in which a
particular final state particle, including a or -meson, is tagged.Comment: 36 pages, Latex Small corrections to text. To appear in Phys. Rev.
Heavy Quark Initiated Contributions to Deep Inelastic Structure Functions
We present O(alpha_s^1) corrections to deep inelastic scattering amplitudes
on massive quarks obtained within the scheme of Aivazis, Collins, Olness and
Tung (ACOT). After identifying the correct subtraction term the convergence of
these contributions towards the analogous coefficient functions for massless
quarks, obtained within the modified minimal subtraction scheme (MSbar), is
demonstrated. Furthermore, the quantitative relevance of the contributions to
neutral current (NC) and charged current (CC) structure functions is
investigated for several choices of the factorization scale.Comment: 29 pages, 6 figures; uses epsfig.sty, amssymb.sty, axodraw.sty; minor
changes for publication in Phys. Rev.
A Review of Target Mass Corrections
With recent advances in the precision of inclusive lepton--nuclear scattering
experiments, it has become apparent that comparable improvements are needed in
the accuracy of the theoretical analysis tools. In particular, when extracting
parton distribution functions in the large-x region, it is crucial to correct
the data for effects associated with the nonzero mass of the target. We present
here a comprehensive review of these target mass corrections (TMC) to structure
functions data, summarizing the relevant formulas for TMCs in electromagnetic
and weak processes. We include a full analysis of both hadronic and partonic
masses, and trace how these effects appear in the operator product expansion
and the factorized parton model formalism, as well as their limitations when
applied to data in the x->1 limit. We evaluate the numerical effects of TMCs on
various structure functions, and compare fits to data with and without these
corrections.Comment: 41 pages, 13 figures; minor updates to match published versio
Twist-2 Heavy Flavor Contributions to the Structure Function
The twist--2 heavy flavor contributions to the polarized structure function
are calculated. We show that this part of is related
to the heavy flavor contribution to by the Wandzura--Wilczek
relation to all orders in the strong coupling constant. Numerical results are
presented.Comment: 17 pages LATEX, 1 style files, 4 figure
Heavy Flavours at Colliders
I review some topics in the production and decays of heavy flavours that are
relevant for collider physics. In particular, I discuss the present status and
some recent progress related to masses, parton densities and fragmentation
functions of heavy quarks, as well as threshold resummation, polarized onium
production at high transverse momentum, and a factorization theorem for decays.Comment: 12 pages. Plenary talk given at UK Phenomenology Workshop on Collider
Physics, Durham, England, 19-24 Sep 1999 Comments and references adde
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
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