Download or read book Measurement of Deeply Virtual Compton Scattering at HERA written by and published by . This book was released on 2003 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measurement of Deeply Virtual Compton Scattering and Its T dependence at HERA written by and published by . This book was released on 2007 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measurement of Deeply Virtual Compton Scattering at HERA written by Rainer Stamen and published by . This book was released on 2001 with total page 99 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measurement of Deeply Virtual Compton Scattering Using the ZEUS Detector at HERA written by Iwona Grabowska-Bold and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Measurement of the Q2 W and T dependences of Deeply Virtual Compton Scattering at HERA written by ZEUS Collaboration and published by . This book was released on 2008 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measurement of Deeply Virtual Compton Scattering Cross Sections with the ZEUS Detector at HERA written by Amir Stern and published by . This book was released on 2017 with total page 123 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Future Measurements of Deeply Virtual Compton Scattering at HERMES written by and published by . This book was released on 2001 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Deeply Virtual Compton Scattering at 6 GeV written by and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors propose a measurement of the Deep Virtual Compton Scattering process (DVCS) ep → ep[gamma] in Hall A at Jefferson Lab with a 6 GeV beam. The authors are able to explore the onset of Q2 scaling, by measuring a beam helicity asymmetry for Q2 ranging from 1.5 to 2.5 GeV2 at x{sub B} ≈ 0.35. At this kinematics, the asymmetry is dominated by the DVCS Bethe-Heitler (BH) interference, which is proportional to the imaginary part of the DVCS amplitude amplified by the full magnitude of the BH amplitude. The imaginary part of the DVCS amplitude is expected to scale early. Indeed, the imaginary part of the forward Compton amplitude measured in deep inelastic scattering (via the optical theorem) scales at Q2 as low as 1 GeV2. If the scaling regime is reached, they make an 8% measurement of the skewed parton distributions (SPD) contributing to the DVCS amplitude. Also, this experiment allows them to separately estimate the size of the higher-twist effects, since they are only suppressed by an additional factor 1/Q compared to the leading-twist term, and have a different angular dependence. They use a polarized electron beam and detect the scattered electron in the HRSe, the real photon in an electromagnetic calorimeter (under construction) and the recoil proton in a shielded scintillator array (to be constructed). This allows them to determine the difference in cross-sections for electrons of opposite helicities. This observable is directly linked to the SPD's. The authors estimate that 25 days of beam (600 hours) are needed to achieve this goal.
Download or read book Deeply Virtual Compton Scattering and Its Beam Charge Asymmetry in E p Collisions at HERA written by and published by . This book was released on 2009 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Future Measurements of Deeply Virtual Compton Scattering written by V. A. Korotkov and published by . This book was released on 2001 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Deeply Virtual Compton Scattering and Its Beam Charge Asymmetry in E p Collisions at HERA written by H1 Collaboration and published by . This book was released on 2009 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Deeply Virtual Compton Scattering at JLab Hall A written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The deeply virtual Compton scattering reaction has been investigated in the Hall A of the Jefferson Laboratory by measuring longitudinally polarized (e, e'gamma) cross sections, in the valence quark region, for protons and neutrons. In the proton channel, experimental results strongly support the factorization of the cross section at Q2 as low as 2 GeV2, opening the path to systematic measurements of generalized parton distributions (GPDs). In the neutron case, preliminary data show sensitivity to the angular momentum of quarks.
Download or read book Deeply Virtual Compton Scattering with CLAS12 written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: An overview is given about the capabilities provided by the JLab 12 GeV Upgrade to measure deeply virtual exclusive processes with high statistics and covering a large kinematics range in the parameters that are needed to allow reconstruction of a spatial image of the nucleon's quark structure. The measurements planned with CLAS12 will cross section asymmetries with polarized beams and with longitudinally and transversely polarized proton targets in the constrained kinematics $x = \pm \xi$. In addition, unpolarized DVCS cross sections, and doubly polarized beam target asymmetries will be measured as well. In this talk only the beam and target asymmetries will be discussed.
Download or read book Deeply Virtual Compton Scattering at Jefferson Laboratory written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The generalized parton distributions (GPDs) have emerged as a universal tool to describe hadrons in terms of their elementary constituents, the quarks and the gluons. Deeply virtual Compton scattering (DVCS) on a proton or neutron ($N$), $e N \rightarrow e' N' \gamma$, is the process more directly interpretable in terms of GPDs. The amplitudes of DVCS and Bethe-Heitler, the process where a photon is emitted by either the incident or scattered electron, can be accessed via cross-section measurements or exploiting their interference which gives rise to spin asymmetries. Spin asymmetries, cross sections and cross-section differences can be connected to different combinations of the four leading-twist GPDs (${H}$, ${E}$, ${\tilde{H}}$, ${\tilde{E}}$) for each quark flavors, depending on the observable and on the type of target. This paper gives an overview of recent experimental results obtained for DVCS at Jefferson Laboratory in the halls A and B. Several experiments have been done extracting DVCS observables over large kinematics regions. Multiple measurements with overlapping kinematic regions allow to perform a quasi-model independent extraction of the Compton form factors, which are GPDs integrals, revealing a 3D image of the nucleon.
Download or read book Results on Deeply Virtual Compton Scattering at Jefferson Lab written by Franck Sabatie and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: After about 10 years of growing interest for Generalized Parton Distributions come the first results from dedicated experiments, using the golden Deeply Virtual Compton Scattering process. After a short introduction, we will explain the experimental methodology and show results of the Hall A E00-110 experiment, which aimed at measuring helicity-dependent photon electroproduction cross sections. We will emphasize how this experiment provided the first stringent tests of the scaling property of this process, allowing for the first time a model-independent extraction of a linear combination of Generalized Parton Distributions. We will also describe the Hall B E01-113 experiment which measured the photon electroproduction beam spin asymmetry over a wide kinematical range. The summary will include an outlook on the next generation of experiments which are already planned at Jefferson Lab at 6 GeV, but also after the planned 12 GeV upgrade.
Download or read book Deeply Virtual Compton Scattering at COMPASS written by Johannes Vincenzo Giarra and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Studying hard exclusive reactions in lepton-nulceon scattering like for e.g. hard exclusive photoproduction in Deeply Virtual Compton Scattering (DVCS), allows to study the 3-dimensional nucleon structure in the framework of Generalized Parton Distribution functions (GPDs). From the DVCS cross section, combinations of Compton Form Factors (CFFs) can be extracted, which are used to further constrain the related GPDs. In 2016 and 2017, COMPASS measured DVCS on a 2.5 m long liquid hydrogen target using high energy (160 GeV), positively and negatively charged polarized muon beams provided by the M2 beamline of the SPS at CERN. The scattered muons and the produced real photons were detected by the COMPASS spectrometer, which was supplemented by an additional electromagnetic calorimeter for the detection of large-angle photons. To perform an exclusive measurement of the full final state, the target was surrounded by a barrel-shaped time-of-flight system to detect the recoiling target protons. The exclusive photon event sample is extracted using a dedicated event selection to identify all participating particles. This event selection includes the use of exclusivity conditions like for e.g. restricting the missing mass and is further improved by a kinematic fit under the assumption of the topology of a exclusive photon event. Its quality is used as an additonal selecting criterium. The fit also improves the resolution of the event kinematics, in particular on the square of the four-momentum transfer to the proton |t|. The selected data sample does not only include DVCS events, but also contributions by radiative photons produced in the Bethe-Heitler (BH) process and a background contamination by photons originating from the decay of neutral pions. These contributions are determined using dedicated Monte-Carlo samples and are subtracted from the data sample to obtain the pure DVCS contribution. The DVCS cross section is extracted in bins of |t|, separately for each beam charge and polarization. These cross section values are averaged over both beam charges, which allows to extract the |t|-dependence of the charge spin cross section sum. Studying this dependence allows to extract the slope parameter B by a binned log-likelihood fit using an exponential ansatz of the from: e^-B|t|}. The slope parameter is dominated by the contribution of the imaginary part of CFF H. At the COMPASS kinematics, which covers the x_Bj}-domain of sea quarks, it is related to the transverse extension of the proton due to the quark distributions. In the present analysis about 2/3 of the available data in 2016 are used. The 2017 sample is expected to provide two to three times higher statistics, which will allow to extend the analysis and extract the dependence of the slope parameter on x_Bj}.
Download or read book Unitary Constraints on Deeply Virtual Compton Scattering written by and published by . This book was released on 2007 with total page 52201 pages. Available in PDF, EPUB and Kindle. Book excerpt: At moderately low momentum transfer ($-t$ up to 1 GeV$^2$) the coupling to the vector meson production channels gives the dominant contribution to real Compton and deeply virtual Compton scattering (DVCS). Starting from a Regge Pole approach that successfully describes vector meson production, the singular part of the corresponding box diagrams (where the intermediate vector meson-baryon pair propagates on-shell) is evaluated without any further assumptions (unitarity). Such a treatment explains not only the unexpectedly large DVCS unpolarized cross section that has been recently measured at Jefferson Laboratory (JLab), but also all the beam spin and charge asymmetries that has been measured at JLab and Hermes, without explicit need of Generalized Parton Distributions (GPD). The issue of the relationship between the two approaches is addressed.
