1,155 research outputs found
Partons and Jets at the LHC
I review some issues related to short distance QCD and its relation to the
experimental program of the Large Hadron Collider (LHC) now under construction
in Geneva.Comment: Talk at the conference QCD2002 at IIT Kanpur, India, November 2002.
Ten pages with 12 figure
The structure of fluid trifluoromethane and methylfluoride
We present hard X-ray and neutron diffraction measurements on the polar
fluorocarbons HCF3 and H3CF under supercritical conditions and for a range of
molecular densities spanning about a factor of ten. The Levesque-Weiss-Reatto
inversion scheme has been used to deduce the site-site potentials underlying
the measured partial pair distribution functions. The orientational
correlations between adjacent fluorocarbon molecules -- which are characterized
by quite large dipole moments but no tendency to form hydrogen bonds -- are
small compared to a highly polar system like fluid hydrogen chloride. In fact,
the orientational correlations in HCF3 and H3CF are found to be nearly as small
as those of fluid CF4, a fluorocarbon with no dipole moment.Comment: 11 pages, 9 figure
Make Research Data Public? -- Not Always so Simple: A Dialogue for Statisticians and Science Editors
Putting data into the public domain is not the same thing as making those
data accessible for intelligent analysis. A distinguished group of editors and
experts who were already engaged in one way or another with the issues inherent
in making research data public came together with statisticians to initiate a
dialogue about policies and practicalities of requiring published research to
be accompanied by publication of the research data. This dialogue carried
beyond the broad issues of the advisability, the intellectual integrity, the
scientific exigencies to the relevance of these issues to statistics as a
discipline and the relevance of statistics, from inference to modeling to data
exploration, to science and social science policies on these issues.Comment: Published in at http://dx.doi.org/10.1214/10-STS320 the Statistical
Science (http://www.imstat.org/sts/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Efficiency improvements for the numerical computation of NLO corrections
In this paper we discuss techniques, which lead to a significant improvement
of the efficiency of the Monte Carlo integration, when one-loop QCD amplitudes
are calculated numerically with the help of the subtraction method and contour
deformation. The techniques discussed are: holomorphic and non-holomorphic
division into sub-channels, optimisation of the integration contour,
improvement of the ultraviolet subtraction terms, importance sampling and
antithetic variates in loop momentum space, recurrence relations.Comment: 34 pages, version to be publishe
Color transparency in deeply inelastic diffraction
We suggest a simple physical picture for the diffractive parton distributions
that appear in diffractive deeply inelastic scattering. In this picture,
partons impinging on the proton can have any transverse separation, but only
when the separation is small can they penetrate the proton without breaking it
up. By comparing the predictions from this picture with the diffractive data
from HERA, we determine rough values for the small separations that dominate
the diffraction process.Comment: 10 pages, 2 figures; v2: citations added, two comments revised and
expanded, results unchange
Diffractive jet production in a simple model with applications to HERA
In diffractive jet production, two high energy hadrons A and B collide and
produce high transverse momentum jets, while hadron A is diffractively
scattered. Ingelman and Schlein predicted this phenomenon. In their model, part
of the longitudinal momentum transferred from hadron A is delivered to the jet
system, part is lost. Lossless diffractive jet production, in which all of this
longitudinal momentum is delivered to the jet system, has been discussed by
Collins, Frankfurt, and Strikman. We study the structure of lossless
diffractive jet production in a simple model. The model suggests that the
phenomenon can be probed experimentally at HERA, with A being a proton and B
being a bremsstrahlung photon with virtuality . Lossless events should be
present for small , but not for larger than , where
is a characteristic size of the pomeron.Comment: 23 pages, REVTeX 3.0 with 8 postscript figures compressed with
uufiles, OITS 536 and AZPH-TH/94-0
Accessing transversity with interference fragmentation functions
We discuss in detail the option to access the transversity distribution
function by utilizing the analyzing power of interference
fragmentation functions in two-pion production inside the same current jet. The
transverse polarization of the fragmenting quark is related to the transverse
component of the relative momentum of the hadron pair via a new azimuthal
angle. As a specific example, we spell out thoroughly the way to extract
from a measured single spin asymmetry in two-pion inclusive
lepton-nucleon scattering. To estimate the sizes of observable effects we
employ a spectator model for the fragmentation functions. The resulting
asymmetry of our example is discussed as arising in different scenarios for the
transversity.Comment: 17 pages, 15 figures in .eps format included, typesetted in RevTeX
and epsfig.sty, submitted to Phys. Rev.
Crystal-like high frequency phonons in the amorphous phases of solid water
The high frequency dynamics of low- (LDA) and high-density amorphous-ice
(HDA) and of cubic ice (I_c) has been measured by inelastic X-ray Scattering
(IXS) in the 1-15 nm^{-1} momentum transfer (Q) range. Sharp phonon-like
excitations are observed, and the longitudinal acoustic branch is identified up
to Q = 8nm^{-1} in LDA and I_c and up to 5nm^{-1} in HDA. The narrow width of
these excitations is in sharp contrast with the broad features observed in all
amorphous systems studied so far. The "crystal-like" behavior of amorphous
ices, therefore, implies a considerable reduction in the number of decay
channels available to sound-like excitations which is assimilated to low local
disorder.Comment: 4 pages, 3 figure
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