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High Resolution Hypernuclear Spectroscopy at Jefferson Lab Hall A

Description: The characteristics of the Jefferson Lab electron beam, together with those of the experimental equipment, offer a unique opportunity to study hypernuclear spectroscopy via electromagnetic induced reactions. Experiment 94-107 started a systematic study on 1p-shell targets, $^{12}C$, $^{9}Be$ and $^{16}O$. For $^{12}C$ for the first time measurable strength in the core-excited part of the spectrum between the ground state and the p state was shown in $^{12}_{\Lambda}B$ spectrum. A high-quality $^{16}_{\Lambda}N$ spectrum was produced for the first time with sub-MeV energy resolution. A very precise $\Lambda$ binding energy value for $^{16}_{\Lambda}N$, calibrated against the elementary $(e,e'K^+)$ reaction on hydrogen, has also been obtained. $^{9}_{\Lambda}Li$ spectrum shows some disagreement in strength for the second and third doublet with respect to the theory.
Date: September 1, 2013
Creator: Garibaldi,Franco; Bydzovsky,Petr; Cisbani,Evaristo; Cusanno, Francesco; De Leo, Raffaele; Frullani, Salvatore et al.
Partner: UNT Libraries Government Documents Department

The origins of quark-hadron duality: How does the square of the sum become the sum of the squares?

Description: Bloom-Gilman duality demonstrates empirically that the electroproduction of N*'s at low momentum transfers averages smoothly around the scaling curve measured at large momentum transfers. The latter is proportional to the sum of the squares of the constituent charges whereas the former involves the coherent excitation of resonances and is driven by the square of summed constituent charges. We determine the minimal necessary conditions for this equality to be realized so that duality can occur and consider the implications for a range of processes that may be studied soon at CEBAF.
Date: January 30, 2001
Creator: Close, Frank E. & Isgur, Nathan
Partner: UNT Libraries Government Documents Department

Electroproduction of Photons and of Pawns on the Proton in Quadrimoment of Transfer Q2=1.0GeV2. Measure Cross Sections and Extraction of Polarizabilities Generalities; Electroproduction de Photons et de Pions sur le Proton au Quadrimoment de Transfert Q2=1.0GeV2. Mesure des Sections Efficaces et Extraction des Polarisabilites Generalisees

Description: In hadronic physics, the nucleon structure and the quarks confinement are still topical issues. The neutral pion electroproduction and virtual Compton scattering (VCS) reactions allow us to access new observables that describe this structure. This work is focused on the VCS experiment performed at Jefferson Lab in 1998.
Date: November 6, 2001
Creator: Laveissiere, Geraud
Partner: UNT Libraries Government Documents Department

Electroexcitation of Nucleon Resonances

Description: Recent electroproduction results in the domain of s-channel nucleon resonance excitation are presented, and preliminary data in the search for missing states will be discussed. I also address a new avenue to pursue N* physics using exclusive deeply virtual Compton scattering, recently measured for the first time at JLab and DESY.
Date: March 1, 2002
Creator: Burkert, Volker D.
Partner: UNT Libraries Government Documents Department

Electroproduction of light quark baryons

Description: The status of electromagnetic excitation of light quark (u, d) baryon states is reviewed and confronted with results of calculations within the framework of microscopic models of the baryon structure and the photon - baryon coupling. Prospects for a qualitative improvement of their knowledge in this sector using photon and electron beams at the new, intermediate energy continuous wave (CW) electron machines are discussed.
Date: April 1, 1992
Creator: Burkert, V.
Partner: UNT Libraries Government Documents Department

Dynamical study of {triangle} excitation with N(e,e{prime}{pi}) reaction

Description: The authors report on the results from their investigation of pion electroproduction based on the dynamical model developed in the SL Model. The essential point of SL model is to have a consistent description of the {pi}N scattering and {gamma}N {yields} {pi}N transition. This is important in extracting the {gamma}N {yields} {Delta} form factors since it was found that the nonresonant mechanisms and the final {pi}N interaction can account for about 40% of the M1 strength at Q{sup 2} = 0. The details have been discussed and the talk given by T. Sato in this conference. Here they only present their results for the {gamma}N {yields} {Delta} form factors.
Date: July 7, 2000
Creator: Lee, T.-S. H. & Sato, T.
Partner: UNT Libraries Government Documents Department

Hard exclusive electroproduction of pions

Description: The authors investigate the exclusive electroproduction of {pi}{sup +} mesons from nucleons. To leading twist, leading order {alpha}{sub s} accuracy the corresponding production amplitude can be decomposed into pseudovector and pseudoscalar parts. Both can be expressed in terms of quark double distribution functions of the nucleon. While the pseudovector contribution is connected to ordinary polarized quark distributions, the pseudoscalar part can be related to one pion t-channel exchange. They observe that the pseudovector part of the production amplitude is important at x < 0.1. On the other hand, for 0.1 < x < 0.4 contributions from one pion exchange dominate.
Date: December 1, 1998
Creator: Mankiewicz, L.; Piller, G. & Radyushkin, A.
Partner: UNT Libraries Government Documents Department

How to extract the P{sub 33}(1232) resonance contributions from the amplitudes M{sub 1{sup +}}{sup 3/2},E{sub 1{sup +}}{sup 3/2},S{sub 1{sup +}}{sup 3/2} of pion electroproduction on nucleons

Description: Within the dispersion relation approach, solutions of integral equations for the multipoles M{sub 1{sup +}}{sup 3/2},E{sub 1{sup +}}{sup 3/2},S{sub 1{sup +}}{sup 3/2} are found at 0 < Q{sup 2} < 3 GeV{sup 2}. These solutions should be used as input for the resonance and nonresonance contributions in the analyses of pion electroproduction data in the P{sub 33}(1232) resonance region. It is shown that the traditional identification of the amplitude M{sub 1{sup +}}{sup 3/2} (as well of the amplitudes E{sub 1{sup +}}{sup 3/2},S{sub 1{sup +}}{sup 3/2}) with the P{sub 33}(1232) resonance contribution is not right; there is a contribution in these amplitudes which has a nonresonance nature and is produced by rescattering effects in the diagrams corresponding to the nucleon and pion poles. This contribution is reproduced by the dispersion relations. Taking into account nonresonance contributions in the amplitudes M{sub 1{sup +}}{sup 3/2},E{sub 1{sup +}}{sup 3/2}, the helicity amplitudes A{sub p}{sup 1/2}, A{sub p}{sup 3/2} and the ratio E2/M1 for the {gamma}N {r_arrow} P{sub 33}(1232) transition are extracted from experiment at Q{sup 2}=0. They are in good agreement with quark model predictions.
Date: August 1997
Creator: Aznauryan, I. G.
Partner: UNT Libraries Government Documents Department

Monte Carlo calculations of track structures

Description: In the study of radiation effects in matter, a knowledge of the spatial distribution of secondary products and of energy deposited is important. For charged particles heavier than electrons, energy is deposited along an almost straight track which can be seen in photographic emulsions or cloud chambers. The initial effect of the energy deposition is the production of clouds of collectively excited electrons (``plasmons``), ions and secondary electrons (``delta rays`` which in turn produce plasmons etc.) We describe the spatial pattern of energy deposited and new species produced as the track structure. The discussion presented here is only concerned with the initial track structure; the subsequent fate of the products is discussed in other papers of this conference. 6 refs., 2 figs.
Date: December 31, 1995
Creator: Bichsel, H.
Partner: UNT Libraries Government Documents Department

Exclusive electroproduction of phi mesons at 4.2 GeV

Description: We studied the exclusive reaction ep {yields} e{prime}p{prime}{phi} using the {phi} {yields} K{sup +} K{sup -} decay mode. The data were collected using a 4.2 GeV incident electron beam and the CLAS detector at Jefferson Lab. Our experiment covers the range in Q{sup 2} from 0.7 to 2.2 GeV{sup 2}, and W from 2.0 to 2.6 GeV. Taken together with all previous data, we find a consistent picture of {phi} production on the proton. Our measurement shows the expected decrease of the t-slope with the vector meson formation time c{Delta}{tau} below 2 fm. At c{Delta}{tau}= 0.6 fm, we measure b{sub {phi}} = 2.27 {+-} 0.42 GeV{sup -2}. The cross section dependence on W as W{sup 0.2{+-}0.1} at Q{sup 2} = 1.3 GeV{sup 2} was determined by comparison with {phi} production at HERA after correcting for threshold effects. This is the same dependence as observed in photoproduction.
Date: January 1, 2001
Creator: Lukashin, K.; E.S., Smith. & others], CLAS Collaboration
Partner: UNT Libraries Government Documents Department

On the Q{sup 2} Variation of Spin-Dependent Deep-Inelastic Electron Proton Scattering

Description: We suggest a phenomenological model describing the sum rules for the real and virtual polarized photon absorption on the nucleon. The contribution of the isobar delta-(1232) electroproduction, essential at small Q{sup 2}, has been subtracted quantitatively. The model predictions are compared with the results of the EMC polarized structure function measurements on the photon.
Date: December 10, 1992
Creator: Burkert, Volker D. & Ioffe, B.L.
Partner: UNT Libraries Government Documents Department

QED Radiative Corrections in Processes of Exclusive Pion Electroproduction

Description: Formalism for radiative correction (RC) calculation in exclusive pion electroproduction on the proton is presented. A FORTRAN code EXCLURAD is developed for the RC procedure. The numerical analysis is done in the kinematics of current Jefferson Lab experiments.
Date: March 1, 2002
Creator: Afanasev, Andrei; Akushevich, I.; Burkert, Volker & Joo, K.
Partner: UNT Libraries Government Documents Department

Electroproduction of strangeness above the resonance region

Description: A simple and elegant model, based on Reggeized t-channel exchanges, is successful in reproducing the main features of all existing data of the reactions ep-->e'K{sup +}Sigma{sup 0}. In particular, the original way in which gauge invariance is taken into account is found to be essential to describe the ration between the Coulomb and the transverse cross sections at large Q{sup 2} that has been measured recently at Jefferson Laboratory.
Date: April 1, 1999
Creator: Guidal, Michel; Laget, Jean-Marc & Vanderhaeghen, M.
Partner: UNT Libraries Government Documents Department

Interplay of Hard and Soft Processes at JLAB Energies

Description: Even at moderate energy machines, there is a regime where hard pion electroproduction proceeds by a perturbatively calculable process. The process, we claim, is not the leading twist fragmentation one but a rather higher twist process that produces kinematically isolated pions. Semiexclusive data may teach us more about parton distribution functions of the target and the pion distribution amplitude. In addition, there is a connection to generalized parton distribution calculations of exclusive processes in that the perturbative kernel is the same.
Date: July 1, 2002
Creator: Afanasev, Andrei & Carlson, Carl E.
Partner: UNT Libraries Government Documents Department

Measurement of Beam-Spin Asymmetries for Deep Inelastic pi{sup +} Electroproduction

Description: We report the first evidence for a non-zero beam-spin azimuthal asymmetry in the electroproduction of positive pions in the deep-inelastic region. Data have been obtained using a polarized electron beam of 4.3 GeV and with the CLAS detector at the Thomas Jefferson National Accelerator Facility (JLab). The amplitude of the sin phi modulation increases with the momentum of the pion relative to the virtual photon, z, with an average amplitude of 0.038+/-0.005+/-0.003 for 0.5<z<0.8 range.
Date: December 1, 2002
Creator: Avakian, H.; Burkert, Volker D.; Elouadrhiri, Latifa & al., et.
Partner: UNT Libraries Government Documents Department

Kaon electroproduction on deuterium.

Description: Kaon electroproduction on deuterium and hydrogen targets has been measured at beam energies of 3.245 and 2.445 GeV and momentum transfer Q{sup 2}=0.38 and 0.5 GeV{sup 2}. Associated {Lambda} production off a proton in the deuteron exhibits a quasifree production mechanism. The production of {Sigma}{sup {minus}} off the neutron could be extracted for the first time with reasonable errors.
Date: January 12, 1998
Creator: Reinhold, J.
Partner: UNT Libraries Government Documents Department

Proposal to Study Electroproduction with Coincidence Techniques at High Energies

Description: Using the large aperture spectrometer of proposal 144 and the electron beam with the tagging system removed we propose to study deep inelastic electron scattering at incident electron energies between 50 and 150 GeV, for values of q{sup 2} between 1 and 20 Gev{sup 2}/c and {nu} between 10 and 130 GeV. The spectrometer will detect not only the scattered electron but also most of the secondary particles.
Date: May 1, 1972
Creator: Bird, L.; Halliwell, C.; Morrison, R.; Walters, John; U., /Carleton; Prentice, J.D. et al.
Partner: UNT Libraries Government Documents Department

Radiative effects in the processes of exclusive photon electroproduction from polarized protons

Description: Radiative effects in the electroproduction of photons in polarized ep-scattering are calculated in the leading log approximation and analyzed numerically for kinematical conditions of current measurement at Jefferson Lab. Radiative corrections to the cross sections, their azimuthal distributions and Fourier coefficients are in particular focus. Kinematical regions where the radiative corrections are considerable are identified.
Date: March 1, 2012
Creator: Igor Akushevich, Alexander Ilyichev
Partner: UNT Libraries Government Documents Department

Electroproduction of $Λ$(1405)

Description: The electroproduction of K{sup +} {Lambda}(1405) was studied by analyzing the E1F data set collected in Hall B at Jefferson Lab. The analysis utilized the decay channel {Sigma}{sup +} {pi}{sup -} of the {Lambda}(1405) and p{pi}{sup 0} of the {Sigma}{sup +}. Simulations of background, {Lambda}(1405) and {Lambda}(1520) production according to PDG values were performed by using standard CLAS analysis tools adapted for the E1F run. Fits of the acceptance-corrected simulations were made to the acceptance-corrected data to determine contributions from signal and background processes. The line shape of {Lambda}(1405) varies with the four momentum transfer, Q{sup 2}, and does not match the line shape based on PDG resonance parameters. It corresponds approximately to predictions of a recent two-pole meson-baryon picture of this state.
Date: April 1, 2012
Creator: Haiyun Lu, Reinhard Schumacher, Brian Raue, Marianna Gabrielyan
Partner: UNT Libraries Government Documents Department

Deeply Virtual Exclusive Reactions with CLAS

Description: Deeply virtual exclusive reactions offer an unique opportunity to study the structure of the nucleon at the parton level as one has access to Bjorken x{sub B} and momentum transfer to the nucleon t at the same time. Such processes can reveal much more information about the structure of the nucleon than either inclusive electroproduction or elastic form factors alone. Dedicated experiments to study Deeply Virtual Compton Scattering (DVCS) and Deeply Virtual Meson Production (DVMP) have been carried out in Hall B at Jefferson Lab. DVCS helicity–dependent and helicity–independent cross sections and beam spin asymmetries have been measured with CLAS, as well as cross sections and asymmetries for the {pi}{sup #25;}0, {eta}#17;, {rho}{sup #26;}0, #26;{rho}{sup +}, {omega} and {phi}#30; for exclusive electroproduction. The data were taken in a wide kinematic range in Q{sup 2}=1–4.5 GeV{sup 2}, x{sub B}=0.1–0.5, and {absval t} up to 2 GeV{sup 2}. We will discuss the interpretation of these data in terms of traditional Regge and Generalized Parton Distributions (GPDs) models. The successful description of the recent CLAS pseudoscalar meson exclusive production data by GPD-based model provides a unique opportunity to access the transversity GPDs. We view the work presented in this report as leading into the program of the Jefferson Lab 12 GeV upgrade. The increased energy and luminosity will allow us to acquire data at much higher Q{sup 2} and x{sub B}, and perform Rosenbluth L/T separations of the cross sections.
Date: November 1, 2011
Creator: Kubarovsky, Valery
Partner: UNT Libraries Government Documents Department

Nucleon Resonance Electrocouplings from the CLAS Data on Exclusive Meson Electroproduction off Protons

Description: {gamma}{sub v}NN* transition helicity amplitudes (electrocouplings) of several prominent excited proton states are determined for the first time in independent analyses of {pi}{sup +}n, {pi}{sup 0}p, and {pi}{sup +}{pi}{sup -}p electroproduction off protons. Consistent results on resonance electrocouplings obtained from major meson electroproduction channels offer an evidence for reliable extraction of these fundamental quantities. Analysis of {pi}{sup +}{pi}{sup -}p electroproduction has extended considerably information on electrocouplings of high lying N* states, which decay preferentially to the N{pi}{pi} final states.
Date: December 1, 2011
Creator: Victor I. Mokeev, Inna G. Aznauryan, Volker D. Burkert
Partner: UNT Libraries Government Documents Department

Nucleon Resonances and Nuclei:Experimental Aspects

Description: An overview of the experimental status of nucleon resonance transition form factors is given.Recent photo- and electroproduction experiments from nuclei in the resonance region are discussed, and prospects for measurements at future CW electron accelerators are briefly addressed.
Date: January 1, 1987
Creator: Burkert, Volker
Partner: UNT Libraries Government Documents Department