11 research outputs found
Photon-pair jet production via gluon fusion at the LHC
Photon-pair direct or jet-associated productions are important for relevant
standard model measurement, Higgs and new physics searches at the LHC. The
loop-induced gluon-fusion process gg -> \gamma\gamma g, which although formally
contributes only at the next-to-next-to-leading order to \gamma\gamma j
productions, may get enhanced by the large gluon flux at the LHC. We have
checked and confirmed previous results on gg -> \gamma\gamma, \gamma\gamma g at
one loop, using now the traditional Feynman diagram based approach and taking
into account the quark mass effects, and further updated them for the 7 and 14
TeV LHC with new inputs and settings. We provide the details and results of the
calculations, which involves manipulation of rank-5 pentagon integrals. Our
results show that the gluon-fusion process can contribute about 10% of the Born
result, especially at small M_{\gamma\gamma} and PT_{\gamma\gamma}, and
increase further the overall scale uncertainty. Top quark loop effects are
examined in detail, which shows importance near or above the threshold
M_{\gamma\gamma} \gsim 2m_t.Comment: 10 pages, 5 figure
Hard Interactions of Quarks and Gluons: a Primer for LHC Physics
In this review article, we develop the perturbative framework for the
calculation of hard scattering processes. We undertake to provide both a
reasonably rigorous development of the formalism of hard scattering of quarks
and gluons as well as an intuitive understanding of the physics behind the
scattering. We emphasize the importance of logarithmic corrections as well as
power counting of the strong coupling constant in order to understand the
behavior of hard scattering processes. We include "rules of thumb" as well as
"official recommendations", and where possible seek to dispel some myths.
Experiences that have been gained at the Fermilab Tevatron are recounted and,
where appropriate, extrapolated to the LHC.Comment: 118 pages, 107 figures; to be published in Reports on Progress in
Physic
HERA and the LHC - A workshop on the implications of HERA for LHC physics: Proceedings Part A
The HERA electron--proton collider has collected 100 pb of data since
its start-up in 1992, and recently moved into a high-luminosity operation mode,
with upgraded detectors, aiming to increase the total integrated luminosity per
experiment to more than 500 pb. HERA has been a machine of excellence
for the study of QCD and the structure of the proton. The Large Hadron Collider
(LHC), which will collide protons with a centre-of-mass energy of 14 TeV, will
be completed at CERN in 2007. The main mission of the LHC is to discover and
study the mechanisms of electroweak symmetry breaking, possibly via the
discovery of the Higgs particle, and search for new physics in the TeV energy
scale, such as supersymmetry or extra dimensions. Besides these goals, the LHC
will also make a substantial number of precision measurements and will offer a
new regime to study the strong force via perturbative QCD processes and
diffraction. For the full LHC physics programme a good understanding of QCD
phenomena and the structure function of the proton is essential. Therefore, in
March 2004, a one-year-long workshop started to study the implications of HERA
on LHC physics. This included proposing new measurements to be made at HERA,
extracting the maximum information from the available data, and
developing/improving the theoretical and experimental tools. This report
summarizes the results achieved during this workshop.Comment: Part A: plenary presentations, WG1: parton density functions, WG2:
Multi-Jet final states and energy flows. 326 pages Part B: WG3: Heavy Quarks
(Charm and Beauty), WG4: Diffraction, WG5: Monte Carlo Tools, 330 page