2,541 research outputs found
Heavy top limit and double-logarithmic contributions to Higgs production at m_H^2 / s << 1
Next-to-next-to-leading order (NNLO) QCD corrections to Higgs boson
hadroproduction have recently been calculated in the heavy top-quark limit m_t
-> \infty. The m_t -> \infty limit introduces double-logarithmic corrections in
ln x, with x = m_H^2 / s. We identify these corrections order by order in
alpha_s. As an application, we derive an analytic expression for the dominant x
<< 1 part of the NNLO coefficient.Comment: 7 page
Landslide detection by deep learning of non-nadiral and crowdsourced optical images
The recent development of mobile surveying platforms and crowdsourced geoinformation has produced a huge amount of non-validated data that are now available for research and application. In the field of risk analysis, with particular reference to landslide hazard, images generated by autonomous platforms (such as UAVs, ground-based acquisition systems, satellite sensors) and pictures obtained from web data mining are easily gathered and contribute to the fast surge in the amount of non-organized information that may engulf data storage facilities. Therefore, the high potential impact of such methods is severely reduced by the need of a massive amount of human intelligence tasks (HITs), which is necessary to filter and classify the data, whatever the final purpose. In this work, we present a new set of convolutional neural networks (CNNs) specifically designed for the automated recognition of landslides and mass movements in non-standard pictures that can be used in automated image classification, in supporting UAV autonomous guidance and in the filtering of data-mined information. Computer vision can be of great help in fostering the autonomous capability of intelligent systems to complement, or completely substitute, HITs. Image and object recognition are at the forefront of this research field. The deep learning procedure has been accomplished by applying transfer learning to some of the top-performer CNNs available in the literature. Results show that the deep learning machines, calibrated on a relevant dataset of validated images of landforms, may supply reliable predictions with computational time and resource requirements compatible with most of the UAV platforms and web data mining applications in landslide hazard studies. Average accuracy achieved by the proposed methods ranges between 87 and 90% and is consistently higher than that obtained by general-purpose state-of-the-art image recognition convolutional neural networks. The method can be applied to early warning, vulnerability assessment, residual risk estimation, model parameterisation and landslide mapping. Specific advantages will be the reduction of the present limitations in the intelligent guidance of landslide mapping drones, the classification of fake news, the validation of post-disaster information and the correct interpretation of an impending change in the environment
High-Energy Factorization and Small-X Deep Inelastic Scattering Beyond Leading Order
High-energy factorization in QCD is investigated beyond leading order and its
relationship to the factorization theorem of mass singularities is established
to any collinear accuracy. Flavour non-singlet observables are shown to be
regular at small x order by order in perturbation theory. In the singlet
sector, we derive the relevant master equations for the space-like evolution of
gluons and quarks. Their solution enables us to sum next-to-leading corrections
to the small-x behaviour of quark anomalous dimensions and deep inelastic
scattering coefficient functions. We present results in both MSbar and DIS
factorization schemes.Comment: 46 pages (+ 7 figures not included, available from the authors),
Latex, Cavendish-HEP-94/0
Association of ultracold double-species bosonic molecules
We report on the creation of heterospecies bosonic molecules, associated from
an ultracold Bose-Bose mixture of 41K and 87Rb, by using a resonantly modulated
magnetic field close to two Feshbach resonances. We measure the binding energy
of the weakly bound molecular states versus the Feshbach field and compare our
results to theoretical predictions. We observe the broadening and asymmetry of
the association spectrum due to thermal distribution of the atoms, and a
frequency shift occurring when the binding energy depends nonlinearly on the
Feshbach field. A simple model is developed to quantitatively describe the
association process. Our work marks an important step forward in the
experimental route towards Bose-Einstein condensates of dipolar molecules.Comment: 5 pages, 4 figure
Z\gamma\gamma production with leptonic decays and triple photon production at NLO QCD
We present a calculation of the O(alpha_s) QCD corrections to the production
of a Z boson in association with two photons and to triple photon production at
hadron colliders. All final-state photons are taken as real. For the Z boson,
we consider the decays both into charged leptons and into neutrinos including
all off-shell effects. Numerical results are obtained via a Monte Carlo program
based on the structure of the VBFNLO program package. This allows us to
implement general cuts and distributions of the final-state particles. We find
that the NLO QCD corrections are sizable and significantly exceed the
expectations from a scale variation of the leading-order result. In addition,
differential distributions of important observables change considerably. The
prediction of two-photon-associated Z production with Z decays into neutrinos
from the charged-lepton rate works well, once we use an additional cut on the
invariant mass of the charged-lepton pair.Comment: 14 pages, 10 figures, 2 table
Intense slow beams of bosonic potassium isotopes
We report on an experimental realization of a two-dimensional magneto-optical
trap (2D-MOT) that allows the generation of cold atomic beams of 39K and 41K
bosonic potassium isotopes. The high measured fluxes up to 1.0x10^11 atoms/s
and low atomic velocities around 33 m/s are well suited for a fast and reliable
3D-MOT loading, a basilar feature for new generation experiments on
Bose-Einstein condensation of dilute atomic samples. We also present a simple
multilevel theoretical model for the calculation of the light-induced force
acting on an atom moving in a MOT. The model gives a good agreement between
predicted and measured flux and velocity values for our 2D-MOT.Comment: Updated references, 1 figure added, 10 pages, 9 figure
Collisional properties of sympathetically cooled K
We report the experimental evidence of the sympathetic cooling of K
with Rb down to 1 K, obtained in a novel tight confining magnetic
trap. This allowed us to perform the first direct measurement of the elastic
cross section of K below 50 K. The result obtained for the triplet
scattering length, Bohr radii, agrees with previous results
derived from photoassociation spectra and from Feshbach spectroscopy of
K.Comment: 7 pages, 4 figures, submitted to Phys. Rev.
Double species condensate with tunable interspecies interactions
We produce Bose-Einstein condensates of two different species, Rb and
K, in an optical dipole trap in proximity of interspecies Feshbach
resonances. We discover and characterize two Feshbach resonances, located
around 35 and 79 G, by observing the three-body losses and the elastic
cross-section. The narrower resonance is exploited to create a double species
condensate with tunable interactions. Our system opens the way to the
exploration of double species Mott insulators and, more in general, of the
quantum phase diagram of the two species Bose-Hubbard model.Comment: 4 pages, 4 figure
Surprises from Quarkonium Decay into Photons
The perturbative QCD approach to quarkonium decay into a photon and hadrons
is reconsidered. It is shown that a consistent treatment within perturbative
QCD calls for the introduction of a fragmentation contribution which has been
neglected so far. The ensuing phenomenological implications are discussed, and,
in particular, the possibility of measuring the gluon fragmentation function of
the photon is addressed.
*To appear in the proceedings of the workshop QCD94, Montpellier, July '94.Comment: 4 pages + 3 figures, uuencoded postscript, Cambridge preprint
Cavendish-HEP-94/0
QCD Theory
Quantum Chromodynamics is an established part of the Standard Model and an
essential part of the toolkit for searching for new physics at high-energy
colliders. I present a status report on the theory of QCD and review some of
the important developments in the past year.Comment: 10 pages, 11 figures, plenary talk presented at ICHEP04, Beijing,
China, August 200
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