284 research outputs found
Summary of the Heavy Flavours Working Group
This is a summary of the contributions presented in the Heavy Flavours
Working Group of the DIS2006 Workshop.Comment: 14 pp, 8 figures. To appear in the proceedings of 14th International
Workshop on Deep Inelastic Scattering (DIS 2006), Tsukuba, Japan, 20-24 Apr
200
Prompt photon in association with a heavy-quark jet in Pb-Pb collisions at the LHC
We present a phenomenological study of the associated production of a prompt
photon and a heavy quark jet (charm or bottom) in Pb-Pb collisions at the LHC.
This channel allows for estimating the amount of energy loss experienced by the
charm and bottom quarks propagating in the dense QCD medium produced in those
collisions. Calculations are carried out at next-to-leading order (NLO)
accuracy using the BDMPS-Z heavy-quark quenching weights. The quenching of the
single heavy-quark jet spectrum reflects fairly the hierarchy in the heavy
quark energy loss assumed in the perturbative calculation. On the contrary, the
single photon spectrum in heavy-ion collisions is only modified at low momenta,
for which less heavy-quark jets pass the kinematic cuts. On top of single
particle spectra, the two-particle final state provides a range of observables
(photon-jet pair momentum, jet asymmetry, among others) which are studied in
detail. The comparison of the photon-jet pair momentum, from p-p to Pb-Pb
collisions, is sensitive to the amount of energy lost by the heavy-quarks and
could therefore be used in order to better understand parton energy loss
processes in the heavy quark sector.Comment: 22 pages, 18 figures, gzipped tar file. Minor changes, 2 references
added. Version published in JHE
Single pion electro-- and neutrinoproduction on heavy targets
We present a calculation of single pion electroproduction cross sections on
heavy targets in the kinematic region of the Delta(1232) resonance. Final state
interactions of the pions are taken into account using the pion multiple
scattering model of Adler, Nussinov and Paschos (ANP model). For
electroproduction and neutral current reactions we obtain results for carbon,
oxygen, argon and iron targets and find a significant reduction of the
W-spectra for pi^0 as compared to the free nucleon case. On the other hand, the
charged pion spectra are only little affected by final state interactions.
Measurements of such cross sections with the CLAS detector at JLAB could help
to improve our understanding of pion rescattering effects and serve as
important/valuable input for calculations of single pion neutrinoproduction on
heavy targets relevant for current and future long baseline neutrino
experiments. Two ratios, in Eq. (3.8) and (3.10), will test important
properties of the model.Comment: 21 pages, 8 figure
Reconciling open charm production at the Fermilab Tevatron with QCD
We study the inclusive hadrodroduction of D^0, D^+, D^{*+}, and D_s^+ mesons
at next-to-leading order in the parton model of quantum chromodynamics endowed
with universal non-perturbative fragmentation functions (FFs) fitted to e^+e^-
annihilation data from CERN LEP1. Working in the general-mass
variable-flavor-number scheme, we resum the large logarithms through the
evolution of the FFs and, at the same time, retain the full dependence on the
charm-quark mass without additional theoretical assumptions. In this way, the
cross section distributions in transverse momentum recently measured by the CDF
Collaboration in run II at the Fermilab Tevatron are described within errors.Comment: 9 pages, 8 figure
Delineating the polarized and unpolarized photon distributions of the nucleon in eN collisions
The production rates of lepton-photon and dimuon pairs at the HERA collider
and the HERMES experiment are evaluated in the leading order equivalent photon
approximation. It is shown that the production rates are sufficient to
facilitate the extraction of the polarized and unpolarized equivalent photon
distributions of the proton and neutron in the available kinematical regions.
It is pointed out that these results indicate the possibility of additional,
independent, tests concerning the unpolarized and polarized structure functions
F_{1,2}^N and g_{1,2}^N, respectively, of the nucleon.Comment: Final version, to appear in Eur. Phys.
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