Exclusive electroproduction and off-diagonal parton distributions

Off-diagonal parton distributions occur in several hard exclusive reactions. They extend the study of hadron structure beyond what can be learned from ordinary distributions and have a particularly rich spin structure. The hard scattering subprocesses in electroproduction of mesons and of real photons satisfy helicity selection rules, which provide powerful tools to test leading-twist dominance at a given value of the hard scale.Comment: 7 pages, 3 figures, LaTeX2e. Talk given at the Fourth Workshop on Quantum Chromodynamics, Paris, France, 1-6 June 199

Polarisation in deeply virtual meson production

We discuss two aspects of polarisation in hard exclusive meson production: the leading-twist selection rule for the meson helicity, and the different partial waves of a (pi pi)-pair which may or may not be due to the decay of a rho.Comment: 9 pages, 1 figure. Talk given at the Workshop on Exclusive and Semiexclusive Processes at High Momentum Transfer, Jefferson Lab, May 1999. Remark added on the transition from two gluons to a pion pai

Timelike deeply virtual Compton scattering with a linearly polarized real (or quasi-real) photon beam

We calculate timelike virtual Compton scattering amplitudes in the generalized Bjorken scaling regime and focus on a new polarization asymmetry in the scattering process with a linearly polarized photon beam in the medium energy range, which will be studied intensely at JLab12 experiments. We demonstrate that new observables help us to access the polarized quark and gluon generalized parton distributions $\tilde H(x, \xi, t)$ and $\tilde E(x, \xi, t)$.Comment: To appear in the proceedings XXII. International Workshop on Deep Inelastic Scattering and Related Subjects (DIS 2014), 28 April - 2 May 2014, Warsaw, Polan

D0ˉD0\bar{D^0} D^0-production in ppˉp\bar{p}-collisions within a double handbag approach

We estimate the scattering amplitude of the process $p \bar{p} \,\to\, \bar{D^0} D^0$ within a double-handbag framework where transition distribution amplitudes, calculated through an overlap representation, factorize from a hard subprocess. This process will be measured in the $\bar{\text{P}}\text{ANDA}$ experiment at GSI-FAIR.Comment: Talk given at the 11th International Conference on Low Energy Antiproton Physics (LEAP2013

Double handbag description of proton-antiproton annihilation into a heavy meson pair

We propose to describe the process $p \bar{p} \,\to\, \bar{D^0} D^0$ in a perturbative QCD motivated framework where a double-handbag hard process $u d \bar u \bar d \to \bar{c} c$ factorizes from transition distribution amplitudes, which are quasi forward hadronic matrix elements of $\Psi_q \Psi_q \Psi_c$ operators, where q denotes light quarks and c denotes the heavy quark. We advocate that the charm-quark mass acts as the large scale allowing this factorization. We calculate this process in the simplified framework of the scalar diquark model and present the expected cross sections for the PANDA experiment at GSI-FAIR.Comment: 25 page

Soft-collinear resummation in deeply virtual Compton scattering

We derive an all order resummation formula for the deeply virtual Compton scattering (DVCS) amplitude, which takes into account soft gluon exchanges in the non-singlet quark coefficient function. We identify the ladder diagrams responsible in light-like gauge for [alphaS log^2 (x +/- xi)]^n contributions. The resummed series results in a simple closed expression.Comment: 4 pages, 4 figure

Double logarithms resummation in exclusive processes : the surprising behavior of DVCS

Double logarithms resummation has been much studied in inclusive as well as exclusive processes. The Sudakov mechanism has often be the crucial tool to exponentiate potentially large contributions to amplitudes or cross-sections near phase-space boundaries. We report on a recent work where a very different pattern emerges : the DVCS quark coefficient function C(x,\xi) develops, near the particular point x=\xi, a non-alternate series in \alpha_s^n log^{2n}(x-\xi) which may be resummed in a cosh[K sqrt \alpha_s log(x-\xi)] factor. This result is at odds with the known result for the corresponding coefficient function for the pion transition form factor near the end point C(z) although they are much related through a z -> x/\xi correspondence.Comment: 9 pages, 1 figure, Presented at the Low x workshop, May 30 - June 4 2013, Rehovot and Eilat, Israe

A consistent model for \pi N transition distribution amplitudes and backward pion electroproduction

The extension of the concept of generalized parton distributions leads to the introduction of baryon to meson transition distribution amplitudes (TDAs), non-diagonal matrix elements of the nonlocal three quark operator between a nucleon and a meson state. We present a general framework for modelling nucleon to pion ($\pi N$) TDAs. Our main tool is the spectral representation for \pi N TDAs in terms of quadruple distributions. We propose a factorized Ansatz for quadruple distributions with input from the soft-pion theorem for \pi N TDAs. The spectral representation is complemented with a D-term like contribution from the nucleon exchange in the cross channel. We then study backward pion electroproduction in the QCD collinear factorization approach in which the non-perturbative part of the amplitude involves \pi N TDAs. Within our two component model for \pi N TDAs we update previous leading-twist estimates of the unpolarized cross section. Finally, we compute the transverse target single spin asymmetry as a function of skewness. We find it to be sizable in the valence region and sensitive to the phenomenological input of our \pi N TDA model.Comment: 39 pages, 9 figure

The Rosario dataset: Multisensor data for localization and mapping in agricultural environments

In this paper we present the Rosario dataset, a collection of sensor data for autonomous mobile robotics in agricultural scenes. The dataset is motivated by the lack of realistic sensor readings gathered by a mobile robot in such environments. It consists of six sequences recorded in soybean fields showing real and challenging cases: highly repetitive scenes, reflection, and burned images caused by direct sunlight and rough terrain among others. The dataset was conceived in order to provide a benchmark and contribute to the agricultural simultaneous localization and mapping (SLAM)/odometry and sensor fusion research. It contains synchronized readings of several sensors: wheel odometry, inertial measurement unit (IMU), stereo camera, and a Global Positioning System real-time kinematics (GPS-RTK) system. The dataset is publicly available from http://www.cifasis-conicet.gov.ar/robot/

Deeply Virtual Compton Scattering: How to Test Handbag Dominance?

We propose detailed tests of the handbag approximation in exclusive deeply virtual Compton scattering. Those tests make no use of any prejudice about parton correlations in the proton which are basically unknown objects and beyond the scope of perturbative QCD. Since important information on the proton substructure can be gained in the regime of light cone dominance we consider that such a class of tests is of special relevance