2,287 research outputs found
The Global Patch Collider
Abstract This paper proposes a novel extremely efficient, fullyparallelizable, task-specific algorithm for the computation of global point-wise correspondences in images and videos. Our algorithm, the Global Patch Collider, is based on detecting unique collisions between image points using a collection of learned tree structures that act as conditional hash functions. In contrast to conventional approaches that rely on pairwise distance computation, our algorithm isolates distinctive pixel pairs that hit the same leaf during traversal through multiple learned tree structures. The split functions stored at the intermediate nodes of the trees are trained to ensure that only visually similar patches or their geometric or photometric transformed versions fall into the same leaf node. The matching process involves passing all pixel positions in the images under analysis through the tree structures. We then compute matches by isolating points that uniquely collide with each other ie. fell in the same empty leaf in multiple trees. Our algorithm is linear in the number of pixels but can be made constant time on a parallel computation architecture as the tree traversal for individual image points is decoupled. We demonstrate the efficacy of our method by using it to perform optical flow matching and stereo matching on some challenging benchmarks. Experimental results show that not only is our method extremely computationally efficient, but it is also able to match or outperform state of the art methods that are much more complex
Constraining Quark Transversity through Collins Asymmetry Measurements at STAR
The quark transversity distributions are accessible via measurements of the
azimuthal distribution of charged pions inside jets produced in collisions of
transversely polarized protons. The STAR Detector at the Relativistic Heavy Ion
Collider is capable of full jet reconstruction and charged pion identification
in the mid-rapidity region. This proceeding presents the first results of the
Collins moment of leading charged pions in jets reconstructed from 2.2 pb-1 of
root(s) = 200 GeV transversely polarized (58%) proton data.Comment: 5 pages, 7 figures, 19th Particles and Nuclei International
Conference (PANIC 2011
Recent results of the STAR high-energy polarized proton-proton program at RHIC at BNL
The STAR experiment at the Relativistic Heavy-Ion Collider (RHIC) at
Brookhaven National Laboratory (BNL) is carrying out a spin physics program
colliding transverse or longitudinal polarized proton beams at
GeV to gain a deeper insight into the spin structure and
dynamics of the proton. These studies provide fundamental tests of Quantum
Chromodynamics (QCD).
One of the main objectives of the STAR spin physics program is the
determination of the polarized gluon distribution function through a
measurement of the longitudinal double-spin asymmetry, , for various
processes. Recent results will be shown on the measurement of for
inclusive jet production, neutral pion production and charged pion production
at GeV. In addition to these measurements involving longitudinal
polarized proton beams, the STAR collaboration has performed several important
measurements employing transverse polarized proton beams. New results on the
measurement of the transverse single-spin asymmetry, , for forward
neutral pion production and the first measurement of for mid-rapidity
di-jet production will be discussed.Comment: 8 pages, 5 figures, Invited talk given at the 17th International Spin
Physics Symposium (SPIN 2006), October 2006, Kyoto, Japa
WIMP Dark Matter in a Well-Tempered Regime: A case study on Singlet-Doublets Fermionic WIMP
Serious searches for the weakly interacting massive particle (WIMP) have now
begun. In this context, the most important questions that need to be addressed
are: "To what extent can we constrain the WIMP models in the future?" and "What
will then be the remaining unexplored regions in the WIMP parameter space for
each of these models?" In our quest to answer these questions, we classify WIMP
in terms of quantum number and study each case adopting minimality as a guiding
principle. As a first step, we study one of the simple cases of the minimal
composition in the well-tempered fermionic WIMP regime, namely the
singlet-doublets WIMP model. We consider all available constraints from direct
and indirect searches and also the predicted constraints coming from the near
future and the future experiments. We thus obtain the current status, the near
future prospects and the future prospects of this model in all its generality.
We find that in the future, this model will be constrained almost solely by the
future direct dark matter detection experiments (as compared to the weaker
indirect and collider constraints) and the cosmological (relic density)
constraints and will hence be gradually pushed to the corner of the
coannihilation region, if no WIMP signal is detected. Future lepton colliders
will then be useful in exploring this region not constrained by any other
experiments.Comment: 34 pages, 6 figures; v2: minor corrections, published versio
Angular ordering and parton showers for non-global QCD observables
We study the mismatch between a full calculation of non-global
single-logarithms in the large-N_c limit and an approximation based on free
azimuthal averaging, and the consequent angular-ordered pattern of soft gluon
radiation in QCD. We compare the results obtained in either case to those
obtained from the parton showers in the Monte Carlo event generators HERWIG and
PYTHIA, with the aim of assessing the accuracy of the parton showers with
regard to such observables where angular ordering is merely an approximation
even at leading-logarithmic accuracy and which are commonly employed for the
tuning of event generators to data.Comment: 20 pages, 8 figure
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