2,214 research outputs found
Towards a first estimate of the gluon Sivers function from data in collisions at RHIC
Within a generalized parton model approach, with inclusion of spin and
intrinsic transverse momentum effects, we show how the latest, highly precise,
midrapidity data on the transverse single spin asymmetry measured in
by the PHENIX Collaboration at RHIC [1], can be used to get a
first estimate on the still poorly known gluon Sivers distribution. To this end
we also adopt the present information on the quark Sivers functions, as
extracted from semi-inclusive deeply inelastic scattering data. This analysis
updates a previous study by some of us where a first bound on this distribution
was obtained [2].Comment: RevTex4, 10 pages, 7 eps figures. V2: discussion on the process
dependence of the quark Sivers function, with two new plots (Fig. 4), added
in Section II. One reference added. Results unchanged. Matches the published
versio
Transversity and Collins functions from SIDIS and e+e- data
A global analysis of the experimental data on azimuthal asymmetries in
semi-inclusive deep inelastic scattering (SIDIS), from the HERMES and COMPASS
Collaborations, and in e+e- --> h1 h2 X processes, from the BELLE
Collaboration, is performed. It results in the extraction of the Collins
fragmentation function and, for the first time, of the transversity
distribution function for u and d quarks. These turn out to have opposite signs
and to be sizably smaller than their positivity bounds. Predictions for the
azimuthal asymmetry A_{UT}^{sin(phi_h + phi_S)}, as will soon be measured at
JLab and COMPASS operating on a transversely polarized proton target, are then
presented.Comment: Revised version to appear in Phys. Rev. D. Few misprints corrected,
new figure
3D Point Cloud Reconstruction from Single Plenoptic Image
Novel plenoptic cameras sample the light field crossing the main camera lens. The information available in a plenoptic image must be processed, in order to create the depth map of the scene from a single camera shot. In this paper a novel algorithm, for the reconstruction of 3D point cloud of the scene from a single plenoptic image, taken with a consumer plenoptic camera, is proposed. Experimental analysis is conducted on several test images, and results are compared with state of the art methodologies. The results are very promising, as the quality of the 3D point cloud from plenoptic image, is comparable with the quality obtained with current non-plenoptic methodologies, that necessitate more than one image
Investigating the Transverse Momentum Dependent Gluon Sivers Function in Quarkonium Production at pp Colliders
In this contribution, we will present a short overview of the transverse momentum dependent (TMD) approach as a tool for studying the 3-dimensional structure of hadrons in high-energy (un)polarized hadron collisions. We will then summarize the present status of a running research programme that aims at constraining the poorly known transverse momentum dependent gluon Sivers function, through the study of single spin asymmetries in quarkonium (mainly J / ψ), pion, and D-meson production in polarized proton-proton collisions at RHIC. Finally, we will shortly discuss perspectives for this field of research, emphasizing in particular its role in the physics programme of LHC in the fixed-target setup and NICA-SPD at JINR
Weak intrinsic charge transfer complexes: A new route for developing wide spectrum organic photovoltaic cells
Solar emission extends in the near IR and one of the main issues in designing organic solar cells resides in extending the response into the near IR. Here we show that this may be achieved by making intimate interpenetrated networks of C60 and Zn-phthalocyanine (Zn-Pc) in the solid. Various spectroscopic investigations of co-sublimated thin films of C60 and Zn-phthalocyanine give indeed ample evidence of the existence of a weak charge transfer (CT) state at 1.4 eV, which quenches the photoluminescence of both molecules. The films produced by co-sublimation undergo to a spinodal decomposition producing domains prevalently constituted by Zn-Pc in contact with domain prevalently of C60. The domains size depends on the deposition conditions (rate, stoichiometry, and substrate temperature) forming a percolating 3D network. The separation in different domains is confirmed by the observation of two overlapping peaks, in the resonant Raman spectrum, that correspond to the Ag(2) pinch mode (C=C double bond stretching) for pristine C60 and for a partially (~0.25e) doped one. This indicates that only those donor molecules at the grain boundary, which are in contact with C60, give rise to a renormalized new CT ground state. Photocurrent measurements of interpenetrated networks of C60 and Zn-Pc show a linear dependence with respect to the incident light as a consequence of direct absorption within the CT state. The CT state favors the charge separation between the two components, when it is inserted as interface in the organic photovoltaic p - n junction thus increasing the efficiency of the device
The Sivers Function from SIDIS Data
We study the Sivers effect in transverse single spin asymmetries (SSA) for
pion and kaon production in Semi-Inclusive Deep Inelastic Scattering (SIDIS)
processes. We perform a fit of A^{sin(phi_h-phi_S)}_UT taking into account the
recent data from HERMES and COMPASS Collaborations, which allow a new
determination of the Sivers distribution functions for quark and anti-quark
with u, d and also s flavours. Estimates for forthcoming SIDIS experiments at
COMPASS and JLab are given.Comment: 4 pages, 1 figure. To appear in the proceedings of the XVI
International Workshop on Deep-Inelastic Scattering and Related Subjects, DIS
2008, London, U.K., 7-11 April 200
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