1,018 research outputs found
A next-to-leading order study of photon-pion and pion pair hadro-production in the light of the Higgs boson search at the LHC
We discuss the production of photon-pion and pion pairs with a large
invariant mass at collider energies. We present a study based on a perturbative
QCD calculation at full next-to-leading order accuracy, implemented in the
computer programme DIPHOX. We give estimations for various observables, which
concern the reducible background to the Higgs boson search in the channel H -->
gamma gamma, in the mass range 80-140 GeV at the LHC. We critically discuss the
reliability of these estimates due to our imperfect knowledge of fragmentation
functions at high z and a subtle interplay between higher order corrections and
realistic experimental cuts. We conclude that, whereas the invariant mass
spectrum of photon-pion pairs is theoretically better under control, in the
dipion case large uncertainties remain.Comment: 26 pages Latex, 14 eps figures, replaced by published versio
Stable One-Dimensional Integral Representations of One-Loop N-Point Functions in the General Massive Case: I - Three Point Functions
In this article we provide representations for the one-loop three point
functions in 4 and 6 dimensions in the general case with complex masses. The
latter are part of the GOLEM library used for the computation of one-loop
multileg amplitudes. These representations are one-dimensional integrals
designed to be free of instabilites induced by inverse powers of Gram
determinants, therefore suitable for stable numerical implementations.Comment: 40 pages, 1 figur
A full Next to Leading Order study of direct photon pair production in hadronic collisions
We discuss the production of photon pairs in hadronic collisions, from fixed
target to LHC energies. The study which follows is based on a QCD calculation
at full next-to-leading order accuracy, including single and double
fragmentation contributions, and implemented in the form of a general purpose
computer program of "partonic event generator" type. To illustrate the
possibilities of this code, we present the comparison with observables measured
by the WA70 and D0 collaborations, and some predictions for the irreducible
background to the search of Higgs bosons at LHC in the channel . We also discuss theoretical scale uncertainties for these predictions,
and examine several infrared sensitive situations which deserve further study.Comment: 45 pages Latex, 16 eps files plus some metafont files; replaced by
the version to appear in Eur. Phys. J.
A critical phenomenological study of inclusive photon production in hadronic collisions
We discuss fixed target and ISR inclusive photon production and attempt a
comparison between theory and experiments. The dependence of the theoretical
predictions on the structure functions, and on the renormalization and
factorization scales is investigated. The main result of this study is that the
data cannot be simultaneously fitted with a single set of scales and structure
functions. On the other hand, there is no need for an additional intrinsic
to force the agreement between QCD predictions and experiments, with
the possible exception of one data set. Since the data cover almost overlapping
kinematical ranges this raises the question of consistency among data sets. A
comparative discussion of some possible sources of experimental uncertainties
is sketched.Comment: 22 pages, 3 tables, 10 figures, Late
Avaliação de cultivares de soja semeadas com e sem microcamalhão em rotação com arroz irrigado.
Influência do manejo de pastagens na produtividade da soja em ILP.
Este trabalho avaliou o impacto que a dessecação e a adubação nitrogenada na pastagem de azevém causaram na cultura da soja.Claudia Cristina Gulias Gomes, editora técnica
Photon - Jet Correlations and Constraints on Fragmentation Functions
We study the production of a large-pT photon in association with a jet in
proton-proton collisions. We examine the sensitivity of the jet rapidity
distribution to the gluon distribution function in the proton. We then assess
the sensitivity of various photon + jet correlation observables to the photon
fragmentation functions. We argue that RHIC data on photon-jet correlations can
be used to constrain the photon fragmentation functions in a region which was
barely accessible in LEP experiments.Comment: 23 pages, 9 figure
Higher dimensional abelian Chern-Simons theories and their link invariants
The role played by Deligne-Beilinson cohomology in establishing the relation
between Chern-Simons theory and link invariants in dimensions higher than three
is investigated. Deligne-Beilinson cohomology classes provide a natural abelian
Chern-Simons action, non trivial only in dimensions , whose parameter
is quantized. The generalized Wilson -loops are observables of the
theory and their charges are quantized. The Chern-Simons action is then used to
compute invariants for links of -loops, first on closed
-manifolds through a novel geometric computation, then on
through an unconventional field theoretic computation.Comment: 40 page
- …