Why Studying n-DVCS ?

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Eric Voutier. Why Studying n-DVCS ?. 0 because F 1 (t) is small. 0 because of cancelation of u and d quarks. Sensitivity of the difference of polarized cross sections to the angular momentum of quarks. n-DVCS gives access to the least known and constrained GPD, E. Eric Voutier. - PowerPoint PPT Presentation


  • Why Studying n-DVCS ?n-DVCS gives access to the least known and constrained GPD, E0 because F1(t) is small0 because of cancelation of u and d quarksSensitivity of the difference of polarized cross sections to the angular momentum of quarks

  • How to Measure n-DVCS ?E03-106 experiment in Hall A is an exploratory measurement ofn-DVCS in the valence regionTriple Coincidence Experiment (e,egn)Neutron detection is a very involved matter : in-situ efficiencies and contaminations should be mastered large efficiencies should be achieved

  • E03-106 @ JLab.Hall_AM. Mazouz, Doctorat Thesis, Grenoble (2006)Neutron contributionDeuton contributionTwist-2 (BH.DVCS Interference)Twist-3 (BH.DVCS Interference)Twist-3 (DVCS.DVCS)Twist-2 (BH.DVCS Interference)Twist-3 (BH.DVCS Interference)

  • Experimental ResultsData taking under similar background conditionsInterchange regularly LH2 and LD2 targets (1-2 h)P R E L I M I N A R YPossible observation of 2 contributions of opposite signsBUTResults are dominated by systematics originating from the relative calibration of the calorimeter between LH2 and LD2 dataM. Mazouz, Doctorat Thesis, Grenoble (2006)xB = 0.36Q2 = 1.91 GeV2

  • The mass of the target particle (nucleon or nucleus) is reconstructed taking advantage of the energy/angle correlation of DVCS g. Experimental spectraA calorimeter energy resolution better than 2% would allow to disentangle n-DVCS and d-DVCS in order to access the real partsSimulated shapesCurrent energy resolution allow separation of imaginary parts as long as n-DVCS and d-DVCS signals are opposite signs Going Further ?

  • Going Further ?Kinematical separation

  • Going Further ?Many possible configurations giving access to different GPDs combination.Technical issues regarding the feasibility of polarized 3He cells with thin windowsUnpolarized beam, transverse target polarization Unpolarized beam, perpendicular target polarizationUnpolarized beam, longitudinal target polarizationCombined with similar combinations for protonsa flavor separation can be achieved Target Spin Asymmetry

  • Questions ?Flavor Separation Limits of the quasi-elastic description of the reaction ?Double Coincidence Experimental Method Imaginary parts can be separatedSeparating the real parts is very challengingExistence & magnitude of nuclear corrections ? Measurement of the same observable for proton and neutronyields a combination of GPDs with same flavorSeparating flavor GPDs would require 4 different observables