The GPD experimental program at Jefferson Lab

International audienceRecent results on the Generalized Parton Distribution (GPD) program at Jefferson Lab (JLab) will be presented. The emphasis will be in the Hall A program aiming at measuring Q2−dependences of different terms of the Deeply Virtual Compton Scattering (DVCS) cross section. This is a fundamental step before one can extract GPD information from JLab DVCS data. The upcoming program in Hall A, using both a 6 GeV beam (≈ 2010) and a 11 GeV beam (≈ 2015) will also be described

The Generalized Parton Distributions program in Hall A at Jefferson Lab

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Deep exclusive reactions at Jefferson Lab Hall A

International audienceRecent results on the Generalized Parton Distribution (GPD) programat Jefferson Lab (JLab) will be presented. The emphasis will be in the Hall A program aiming at measuring Q2−dependences of different terms of the Deeply Virtual Compton Scattering (DVCS) cross section. This is a fundamental step before one can extract GPD information from JLab DVCS data. The upcoming program in Hall A, using both a 6 GeV beam (2010) and a 11 GeV beam (≈ 2015) will also be described

Exclusive neutral pion electroproduction in the deeply virtual regime

We present measurements of the ep -\u3e ep pi(0) cross section extracted at two values of four-momentum transfer Q(2) = 1.9 GeV(2) and Q(2) = 2.3 GeV(2) at Jefferson Lab Hall A. The kinematic range allows one to study the evolution of the extracted cross section as a function of Q(2) and W. Results are confronted with Regge-inspired calculations and GPD predictions. An intepretation of our data within the framework of semi-inclusive deep inelastic scattering is also discussed

Generalised parton distributions at HERA and prospects for COMPASS

We present a model of generalised parton distributions based on a forward ansatz in the DGLAP region. We discuss some aspects of the parametrisations, as the dependence in t, with factorised and non-factorised approaches, where t is the square of the four-momentum exchanged at the hadron vertex. The predictions of this model are then compared with DVCS cross sections from H1 and ZEUS, and a related observable, the skewing factor, defined as the following ratio imaginary amplitudes : R \equiv {Im {\cal A} (\gamma^*+p \to \gamma +p)\lfrestriction{t=0}} / {Im {\cal A} (\gamma^*+p \to \gamma^* +p)\lfrestriction{t=0}}. It is an interesting quantity including both the non-forward kinematics and the non-diagonal effects. Finally, we discuss the beam charge asymmetry, which is certainly the most sensitive observable to the different hypothesis needed in the GPDs parametrisations. We show that the approximations done for the t dependence lead to significant differences for the predictions in the HERMES kinematic domain and prospects are given for COMPASS.Comment: 8 pages, 5 figures, submitted to Phys. Lett.

Enantioselective simultaneous analysis of selected pharmaceuticals in environmental samples by ultrahigh performance supercritical fluid based chromatography tandem mass spectrometry

In order to assess the true impact of each single enantiomer of pharmacologically active compounds (PACs) in the environment, highly efficient, fast and sensitive analytical methods are needed. For the first time this paper focuses on the use of ultrahigh performance supercritical fluid based chromatography coupled to a triple quadrupole mass spectrometer to develop multi-residue enantioselective methods for chiral PACs in environmental matrices. This technique exploits the advantages of supercritical fluid chromatography, ultrahigh performance liquid chromatography and mass spectrometry. Two coated modified 2.5\ua0μm-polysaccharide-based chiral stationary phases were investigated: an amylose tris-3,5-dimethylphenylcarbamate column and a cellulose tris-3-chloro-4-methylphenylcarbamate column. The effect of different chromatographic variables on chiral recognition is highlighted. This novel approach resulted in the baseline resolution of 13 enantiomers PACs (aminorex, carprofen, chloramphenicol, 3-N-dechloroethylifosfamide, flurbiprofen, 2-hydroxyibuprofen, ifosfamide, imazalil, naproxen, ofloxacin, omeprazole, praziquantel and tetramisole) and partial resolution of 2 enantiomers PACs (ibuprofen and indoprofen) under fast-gradient conditions

Hard exclusive processes with photons

Virtual photons have proven to be very efficient probes of the hadronic structure, mostly through deep inelastic scattering and related processes. The advent of high luminosity lepton beams has allowed to enlarge the studied processes to hard exclusive reactions, such as deeply virtual Compton scattering and the electroproduction of mesons. We discuss theoretical progress which has lately been quite remarkable in this domain and first much encouraging experimental data.Comment: 3 pages, to be published in the proceedings of the International Conference on the Structure and Interactions of the Photon (Photon 2007) Paris, july 200

The distribution of potential West Nile virus vectors, Culex pipiens pipiens and Culex pipiens quinquefasciatus (Diptera: Culicidae), in Mexico City

<p>Abstract</p> <p>Background</p> <p><it>Culex </it>spp. mosquitoes are considered to be the most important vectors of West Nile virus (WNV) detected in at least 34 species of mosquitoes in the United States. In North America, <it>Culex pipiens pipiens, Culex pipiens quinquefasciatus</it>, and <it>Culex tarsalis </it>are all competent vectors of WNV, which is considered to be enzootic in the United States and has also been detected in equines and birds in many states of Mexico and in humans in Nuevo Leon. There is potential for WNV to be introduced into Mexico City by various means including infected mosquitoes on airplanes, migrating birds, ground transportation and infected humans. Little is known of the geographic distribution of <it>Culex pipiens </it>complex mosquitoes and hybrids in Mexico City. <it>Culex pipiens pipiens </it>preferentially feed on avian hosts; <it>Culex pipiens quinquefasciatus </it>have historically been considered to prefer mammalian hosts; and hybrids of these two species could theoretically serve as bridge vectors to transmit WNV from avian hosts to humans and other mammalian hosts. In order to address the potential of WNV being introduced into Mexico City, we have determined the identity and spatial distribution of <it>Culex pipiens </it>complex mosquitoes and their hybrids.</p> <p>Results</p> <p>Mosquito larvae collected from 103 sites throughout Mexico City during 2004-2005 were identified as <it>Culex, Culiseta </it>or <it>Ochlerotatus </it>by morphological analysis. Within the genus <it>Culex</it>, specimens were further identified as <it>Culex tarsalis </it>or as belonging to the <it>Culex pipiens </it>complex. Members of the <it>Culex pipiens </it>complex were separated by measuring the ratio of the dorsal and ventral arms (DV/D ratio) of the male genitalia and also by using diagnostic primers designed for the <it>Ace.2 </it>gene. <it>Culex pipiens quinquefasciatus </it>was the most abundant form collected.</p> <p>Conclusions</p> <p>Important WNV vectors species, <it>Cx. p. pipiens</it>, <it>Cx. p. quinquefasciatus </it>and <it>Cx. tarsalis</it>, are all present in Mexico City. Hybrids of <it>Cx. p. pipiens </it>and <it>Cx. p. quinquefasciatus </it>were also collected and identified. The presence and abundance of these WNV competent vectors is a cause for concern. Understanding the distribution of these vectors can help improve viral surveillance activities and mosquito control efforts in Mexico City.</p

A decomposition algorithm for feedback min-max model predictive control

Abstract-An algorithm for solving feedback min-max model predictive control for discrete time uncertain linear systems with constraints is presented in the paper. The algorithm solves the corresponding multi-stage min-max linear optimization problem. It is based on applying recursively a decomposition technique to solve the min-max problem via a sequence of low complexity linear programs. It is proved that the algorithm converges to the optimal solution in finite time. Simulation results are provided to compare the proposed algorithm with other approaches