2,565 research outputs found
Hadronic Production of Thermal Photons
We study the thermal emission of photons from hot and dense strongly
interacting hadronic matter at temperatures close to the expected phase
transition to the Quark-Gluon Plasma (QGP). Earlier calculations of photon
radiation from ensembles of interacting mesons are re-examined with additional
constraints, including new production channels as well as an assessment of
hadronic form factor effects. Whereas strangeness-induced photon yields turn
out to be moderate, the hitherto not considered t-channel exchange of omega
mesons is found to contribute appreciably for photon energies above ~1.5 GeV.
The role of baryonic effects is assessed using existing many-body calculations
of lepton pair production. We argue that our combined results constitute a
rather realistic emission rate, appropriate for applications in relativistic
heavy-ion collisions. Supplemented with recent evaluations of QGP emission, and
an estimate for primordial (hard) production, we compute photon spectra at SPS,
RHIC and LHC energies.Comment: 19 pages, 13 figures, 1 appendix. Discussion added, improved
parameterisation
On Hadronic Production of the Meson
Two of the approaches to the hadronic productions of the double heavy mesons
and are investigated. Comparison in various aspects on the
results obtained by the approaches is made and shown in figures and a table.
Some trial understanding of the approaches themselves and the achieved results
is presented. The results may be used as some references for discovering the
mesons at Tevatron and LHC.Comment: 18 pages, the revised version of hep-ph/940824
Hadronic Production of Gamma Rays and Starburst Galaxies
The Milky Way has been estabished to emit gamma rays. These gamma rays are
presumably dominated by decays of neutral pions, although inverse Compton
scatterings and bremsstrahlung also contribute. It is plausible that other
galaxies can be diffuse sources of gamma rays in a similar manner. Starburst
galaxies are particularly interesting to study as they are expected to have
much higher cosmic-ray fluxes and interstellar matter densities. The neutral
pions are created in cosmic-ray interactions with interstellar matter.
Presented here is an overview of the recent work by Karlsson and co-workers on
proton-proton interactions and the resulting secondary particle inclusive cross
sections and angular distributions. This model can be used to calculated the
component of the gamma-ray yield and spectrum from a starburst
galaxy. The yield is expected to increase significantly (30% to 50%) and the
spectrum to be harder than the incident proton spectrum.Comment: 4 pages, 4 figures, submitted for the Proceedings of the 4th
Heidelberg International Symposium on High Energy Gamma-Ray Astronomy, July
7-11, 2008, in Heidelberg, German
Hadronic production of squark-squark pairs: The electroweak contributions
We compute the electroweak (EW) contributions to squark--squark pair
production processes at the LHC within the framework of the Minimal
Supersymmetric Standard Model (MSSM). Both tree-level EW contributions, of
O(alpha_s alpha + alpha^2), and next-to-leading order (NLO) EW corrections, of
O(alpha_s^2 alpha), are calculated. Depending on the flavor and chirality of
the produced quarks, many interferences between EW-mediated and QCD-mediated
diagrams give non-zero contributions at tree-level and NLO. We discuss the
computational techniques and present an extensive numerical analysis for
inclusive squark--squark production as well as for subsets and single
processes. While the tree-level EW contributions to the integrated cross
sections can reach the 20% level, the NLO EW corrections typically lower the LO
prediction by a few percent.Comment: 36 pages, 18 figure
Hadronic production of bottom-squark pairs with electroweak contributions
We present the complete computation of the tree-level and the next-to-leading
order electroweak contributions to bottom-squark pair production at the LHC.
The computation is performed within the minimal supersymmetric extension of the
Standard Model. We discuss the numerical impact of these contributions in
several supersymmetric scenarios.Comment: 33 pages, v2: preprint numbers correcte
Hadronic Production of the Doubly Charmed Baryon with Intrinsic Charm
The effects of the intrinsic charm on the hadronic production of
are studied. By taking reasonable intrinsic charm component into account, the
change of the theoretical prediction on the production of for LHC
and Tevatron is small, but in contrast it may enhance significantly for SELEX.
The reason is that the collision energy at LHC and Tevatron is so large that
the gluon-gluon fusion sub-process, which is irrelevant to intrinsic charm,
becomes dominant. But the situation for SELEX is quite different. Our numerical
results for SELEX show that by considering all the contributions from various
sub-processes, the predicted cross-section may be enhanced by a factor so big
as due to a modulating intrinsic charm being taken into account.
Therefore, the hadronic production of at SELEX may be sensitive
enough in observing the intrinsic charm inside the incident hadrons.Comment: 18 pages, 8 figures. More discussions are adde
Towards W b bbar + j at NLO with an automatized approach to one-loop computations
We present results for the O(alpha_s) virtual corrections to q g -> W b bbar
q' obtained with a new automatized approach to the evaluation of one-loop
amplitudes in terms of Feynman diagrams. Together with the O(alpha_s)
corrections to q q' -> W b bbar g, which can be obtained from our results by
crossing symmetry, this represents the bulk of the next-to-leading order
virtual QCD corrections to W b bbar + j and W b + j hadronic production,
calculated in a fixed-flavor scheme with four light flavors. Furthermore, these
corrections represent a well defined and independent subset of the 1-loop
amplitudes needed for the NNLO calculation of W b bbar. Our approach was tested
against several existing results for NLO amplitudes including selected
O(alpha_s) one-loop corrections to W + 3 j hadronic production. We discuss the
efficiency of our method both with respect to evaluation time and numerical
stability.Comment: 14 pages, 3 figure
Hadronic Production of Colored SUSY Particles with Electroweak NLO Contributions
We consider the production of squarks and gluinos at hadronic colliders. An
overview over the class of processes is given. We investigate in detail the
tree-level and higher order EW contributions to the cross sections. Special
care has to be taken to obtain infrared finite observables. We study
numerically stop--anti-stop and squark--gluino production at the LHC.Comment: 3 pages, 2 figures; To appear in the proceedings of 16th
International Conference on Supersymmetry and the Unification of Fundamental
Interactions (SUSY08), Seoul, Korea, 16-21 Jun 200
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