1,163 research outputs found
Collinear Subtractions in Hadroproduction of Heavy Quarks
We present a detailed discussion of the collinear subtraction terms needed to
establish a massive variable-flavour-number scheme for the one-particle
inclusive production of heavy quarks in hadronic collisions. The subtraction
terms are computed by convoluting appropriate partonic cross sections with
perturbative parton distribution and fragmentation functions relying on the
method of mass factorization. We find (with one minor exception) complete
agreement with the subtraction terms obtained in a previous publication by
comparing the zero-mass limit of a fixed-order calculation with the genuine
massles results in the MSbar scheme. This presentation will be useful for
extending the massive variable-flavour-number scheme to other processes.Comment: 29 pages, 17 figures include
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
Prospects of Open Charm Production at GSI-FAIR and J-PARC
We present a detailed phenomenological study of the prospects of open charm
physics at the future and facilities GSI-FAIR and J-PARC,
respectively. In particular, we concentrate on differential cross sections and
the charge and longitudinal double-spin asymmetries at next-to-leading order
accuracy. Theoretical uncertainties for the proposed observables are estimated
by varying the charm quark mass and the renormalization and factorization
scales.Comment: 11 pages, 13 figure
The Distance of the First Overtone RR Lyrae Variables in the MACHO LMC Database: A New Method to Correct for the Effects of Crowding
Previous studies have indicated that many of the RR Lyrae variables in the
LMC have properties similar to the ones in the Galactic globular cluster M3.
Assuming that the M3 RR Lyrae variables follow the same relationships among
period, temperature, amplitude and Fourier phase parameter phi31 as their LMC
counterparts, we have used the M3 phi31-logP relation to identify the M3-like
unevolved first overtone RR Lyrae variables in 16 fields near the LMC bar. The
temperatures of these variables were calculated from the M3 logP-logTe relation
so that the extinction could be derived for each star separately. Since blended
stars have lower amplitudes for a given period, the period amplitude relation
should be a useful tool for identifying which stars are affected by crowding.
We find that the low amplitude stars are brighter. We remove them from the
sample and derive an LMC distance modulus 18.49+/-0.11.Comment: 30 pages, 7 figures, accepted for publication in the Astronomical
Journa
Discrimination of soil texture and contour recognitions during archaeological excavation using Machine Learning
Measurement of Jets and Jet Suppression in sqrt(s_NN)=2.76 TeV Lead-Lead Collisions with the ATLAS detector at the LHC
The first results of single jet observables in Pb+Pb collisions at
sqrt(s_NN)=2.76 TeV measured with the ATLAS detector at the LHC are presented.
Full jets are reconstructed with the anti-kt algorithm with R= 0.2 and 0.4,
using an event-by-event subtraction procedure to correct for the effects of the
underlying event including elliptic flow. The geometrically-scaled ratio of jet
yields in central and peripheral events,Rcp, indicates a clear suppression of
jets with ET >100 GeV. The transverse and longitudinal distributions of jet
fragments is also presented. We find little no substantial change to the
fragmentation properties and no significant change in the level of suppression
when moving to the larger jet definition.Comment: 5 pages, 6 figures, proceedings for Quark Matter 2011, Annecy,
France, May 23-28, 201
Synergy of multispectral and multisensors satellite observations to evaluate desert aerosol transport and impact of dust deposition on inland waters: study case of Lake Garda
The capabilities of different Earth Observation multispectral satellites are employed for detecting and tracking of desert dust coming from North Africa toward the Northern Italy area and for evaluating the impact of Saharan dust deposition in inland waters, such as those of Lake Garda. Absorbing and scattering spectral optical properties of desert aerosol in the atmospheric windows in the ultraviolet, visible-near-infrared, and infrared spectral ranges are exploited in the dust retrieval performed by OMI/Aura, MODIS/Terra-Aqua, and SEVIRI/MSG satellite sensors. Therefore, the direct link between dust deposition and increase in phytoplankton abundance has been assessed retrieving MERIS-based chlorophyll-a (chl-a) concentration for the desert dust events. Estimates of the increased chl-a in the lake have been derived with values in concentration from 30% to 170%. AERONET sun-photometer measurements, gravimetric particulate matter samplings
Two possible interpretations of the near-field anomaly in microwave propagation
Abstract Microwave propagation experiments, over a short range, demonstrated that the ratio b = c / v of the light velocity c to the observed one v resulted to be less than unity. The various results are here interpreted and compared with the theoretical predictions according to a classical electromagnetic model and to an alternative model based on the assumption of a broken local Lorentz invariance. In any case, the observed superluminal behavior is found to be peculiar to near field
Diffractive charm photoproduction at HERA ep-collider
The cross section of the -meson diffractive photoproduction at the HERA
collider has been calculated in the framework of perturbatively motivated model
for the different kinematic regions. The camparison between the different
Pomeron models has been performed.Comment: 9 pages, 3 figure
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