564 research outputs found
On Forward J/\psi Production at Fermilab Tevatron
The D0 Collaboration has recently reported the measurement of J/\psi
production at low angle. We show here that the inclusion of color octet
contributions in any framework is able to reproduce this data.Comment: 1 page, Revtex, uses epsfig.sty, 2 postscript figure
Comment on Decay
We calculate the rate for decay using Chiral
Perturbation Theory. This isospin violating process results from -
mixing, and its amplitude is proportional to . Experimental information on the branching
ratio for can provide insight into the pattern of
violation in radiative decays.Comment: 7 pages with 2 figures not included but available upon request,
CALT-68-191
Testing Color Evaporation in Photon-Photon Production of J/Psi at CERN LEP II
The DELPHI Collaboration has recently reported the measurement of J/Psi
production in photon-photon collisions at LEP II. These newly available data
provide an additional proof of the importance of colored c bar{c} pairs for the
production of charmonium because these data can only be explained by
considering resolved photon processes. We show here that the inclusion of color
octet contributions to the J/Psi production in the framework of the color
evaporation model is able to reproduce this data. In particular, the
transverse-momentum distribution of the J/Psi mesons is well described by this
model.Comment: 10 pages, 5 Figures, Revtex
Open Heavy Flavor Production in QCD -- Conceptual Framework and Implementation Issues
Heavy flavor production is an important QCD process both in its own right and
as a key component of precision global QCD analysis. Apparent disagreements
between fixed-flavor scheme calculations of b-production rate with experimental
measurements in hadro-, lepto-, and photo-production provide new impetus to a
thorough examination of the theory and phenomenology of this process. We review
existing methods of calculation, and place them in the context of the general
PQCD framework of Collins. A distinction is drawn between scheme dependence and
implementation issues related to quark mass effects near threshold. We point
out a so far overlooked kinematic constraint on the threshold behavior, which
greatly simplifies the variable flavor number scheme. It obviates the need for
the elaborate existing prescriptions, and leads to robust predictions. It can
facilitate the study of current issues on heavy flavor production as well as
precision global QCD analysis.Comment: 13 pages, 10 figures, Proceedings of Ringberg Workshop: New Trends in
HERA Physics 2001, Munich, German
Decay constants, semi-leptonic and non-leptonic decays in a Bethe-Salpeter Model
We evaluate the decay constants for the B and mesons and the form factors
for the semileptonic decays of the B meson to and mesons in a
Bethe-Salpeter model. From data we extract from and from decays. The form factors are then used to obtain non-leptonic
decay partial widths for and in the
factorization approximation.Comment: 15 Pages, 3 Postscript figures (available also from [email protected]
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Synergia: an accelerator modeling tool with 3-D space charge
High precision modeling of space-charge effects, together with accurate treatment of single-particle dynamics, is essential for designing future accelerators as well as optimizing the performance of existing machines. We describe Synergia, a high-fidelity parallel beam dynamics simulation package with fully three dimensional space-charge capabilities and a higher order optics implementation. We describe the computational techniques, the advanced human interface, and the parallel performance obtained using large numbers of macroparticles. We also perform code benchmarks comparing to semi-analytic results and other codes. Finally, we present initial results on particle tune spread, beam halo creation, and emittance growth in the Fermilab booster accelerator
Initial bound state studies in light-front QCD
We present the first numerical QCD bound state calculation based on a
renormalization group-improved light-front Hamiltonian formalism. The QCD
Hamiltonian is determined to second order in the coupling, and it includes
two-body confining interactions. We make a momentum expansion, obtaining an
equal-time-like Schrodinger equation. This is solved for quark-antiquark
constituent states, and we obtain a set of self-consistent parameters by
fitting B meson spectra.Comment: 38 pages, latex, 5 latex figures include
Radiative Transitions in Heavy Mesons in a Relativistic Quark Model
The radiative decays of , , and other excited heavy mesons are
analyzed in a relativistic quark model for the light degrees of freedom and in
the limit of heavy quark spin-flavor symmetry. The analysis of strong decays
carried out in the corresponding chiral quark model is used to calculate the
strong decays and determine the branching ratios of the radiative decays.
Consistency with the observed branching ratios requires the inclusion of the
heavy quark component of the electromagnetic current and the introduction of an
anomalous magnetic moment for the light quark. It is observed that not only
, but also meson transitions within a heavy quark spin multiplet are
affected by the presence of the heavy quark current.Comment: 9 pages, RevTeX. Submitted to Physical Review
delta C-13 Analysis of Mars Analog Carbonates Using Evolved Gas Cavity - Ringdown Spectrometry on the 2010 Arctic Mars Analog Svalbard Expedition (AMASE)
The 2010 Arctic Mars Analog Svalbard Expedition (AMASE) investigated two distinct geologic settings on Svalbard, using instrumentation and techniques in development for future Mars missions, such as the Mars Science Laboratory (MSL), ExoMars, and Mars Sample Return (MSR). The Sample Analysis at Mars (SAM) instrument suite, which will fly on MSL, was developed at Goddard Space Flight Center (GSFC), together with several partners. SAM consists of a quadrupole mass spectrometer (QMS), a gas chromatograph CGC), and a tunable laser spectrometer (TLS), which all analyze gases created by evolved gas analysis (EGA). The two sites studied represent "biotic" and "abiotic" analogs; the "biotic" site being the Knorringfjell fossil methane seep, and the "abiotic" site being the basaltic Sigurdfjell vent complex. The data presented here represent experiments to measure the carbon isotopic composition of carbonates from these two analogs using evolved gas analysis coupled with a commercial cavity ringdown CO2 isotopic analyzer (Picarro) as a proxy for the TLS on SAM
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