Dispersion Approach to Real and Virtual Compton Scattering PDF Download
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Author: Mikhail Gorchtein
Publisher:
ISBN:
Category :
Languages : en
Pages : 189
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Author: Mikhail Gorchtein
Publisher:
ISBN:
Category :
Languages : en
Pages : 189
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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In recent years, new precision experiments have become possible withthe high luminosity accelerator facilities at MAMIand JLab, supplyingphysicists with precision data sets for different hadronic reactions inthe intermediate energy region, such as pion photo- andelectroproduction and real and virtual Compton scattering. By means of the low energy theorem (LET), the global properties of thenucleon (its mass, charge, and magnetic moment) can be separated fromthe effects of the internal structure of the nucleon, which areeffectively described by polarizabilities. Thepolarizabilities quantify the deformation of the charge andmagnetization densities inside the nucleon in an applied quasistaticelectromagnetic field. The present work is dedicated to develop atool for theextraction of the polarizabilities from these precise Compton data withminimum model dependence, making use of the detailed knowledge of pionphotoproduction by means of dispersion relations (DR). Due to thepresence of t-channel poles, the dispersion integrals for two ofthe six Compton amplitudes diverge. Therefore, we have suggested to subtract the s-channel dispersion integrals at zero photon energy($nu=0$). The subtraction functions at $nu=0$ are calculated through DRin the momentum transfer t at fixed $nu=0$, subtracted at t=0. For this calculation, we use the information about the t-channel process, $gammagammatopipito Nbar{N}$. In this way, four of thepolarizabilities can be predicted using the unsubtracted DR in the $s$-channel. The other two, $alpha-beta$ and $gamma_pi$, are free parameters in ourformalism and can be obtained from a fit to the Compton data. We present the results for unpolarized and polarized RCS observables, %in the kinematics of the most recent experiments, and indicate anenhanced sensitivity to the nucleon polarizabilities in theenergy range between pion production threshold and the $Delta(1232)$-resonance.newlineindentFurthermore, we extend the DR formalism to virtual Compton scatter.
Author: D. Drechsel
Publisher:
ISBN:
Category :
Languages : en
Pages : 107
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Author: Dieter Drechsel
Publisher:
ISBN:
Category :
Languages : en
Pages : 106
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Author:
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Category :
Languages : en
Pages :
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Virtual Compton Scattering is studied at the Thomas Jefferson National Accelerator Facility in the energy domain below pion threshold and in the Delta(1232) resonance region. The data analysis is based on the Dispersion Relation (DR) approach. The electric and magnetic Generalized Polarizabilities (GPs) of the proton and the structure functions Pll-Ptt/epsilon and Plt are determined at four-momentum transfer squared Q2=0.92 and 1.76 GeV2. The DR analysis is consistent with the low-energy expansion analysis. The world data set indicates that neither the electric nor magnetic GP follows a simple dipole form.
Author: Laurent Favart
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Dieter Drechsel
Publisher: World Scientific
ISBN: 9814490040
Category : Baryons
Languages : en
Pages : 528
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The study of N∗s can provide us with critical insights into the nature of QCD in the confinement domain. The keys to progress in this domain are the identification of its important degrees of freedom and the effective forces between them. The nucleon is the simplest system in which the nonabelian character of QCD is manifest. There are Nc quarks in a baryon because there are Nc colors, and as a consequence Gell-Mann and Zweig were forced to introduce the quarks in order to describe the octet and decuplet baryons.This volume gives a status report on the recent experimental and theoretical results in the field of nucleon resonance physics. A wealth of new high precision data was presented from facilities around the world, such as BES, BNL, ELSA, GRAAL, JLab, MAMI, MIT/Bates, SPring8, and Yerevan. Particular emphasis was laid on polarization degrees of freedom and large acceptance detectors as precision tools for studying small but important transition amplitudes, and the helicity (spin) structure of the nucleon. There were new results describing the nucleon resonance structure on the basis of quantum chromodynamics, either directly in terms of quarks and gluons by means of lattice gauge theory, or in terms of hadrons in the framework of chiral field theories. A status report on duality showed the surprising connections between the physics of the low energy nucleon resonance region and the realm of quark structure functions in deep inelastic scattering. Finally, this volume contains a summary report of the BRAG workshop, devoted to the analysis of baryon resonances.
Author: D. Drechsel
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Richard Edwin Prange
Publisher:
ISBN:
Category : Dispersion
Languages : en
Pages : 13
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Author: Hartmut Friedrich-Wilhelm Sadrozinski
Publisher:
ISBN:
Category :
Languages : en
Pages : 152
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