0000000001206498
AUTHOR
J. Gomez
Comparing proton momentum distributions in A = 2 and 3 nuclei via 2H 3H and 3He (e,e′p) measurements
We report the first measurement of the $(e,e'p)$ reaction cross-section ratios for Helium-3 ($^3$He), Tritium ($^3$H), and Deuterium ($d$). The measurement covered a missing momentum range of $40 \le p_{miss} \le 550$ MeV$/c$, at large momentum transfer ($\langle Q^2 \rangle \approx 1.9$ (GeV$/c$)$^2$) and $x_B>1$, which minimized contributions from non quasi-elastic (QE) reaction mechanisms. The data is compared with plane-wave impulse approximation (PWIA) calculations using realistic spectral functions and momentum distributions. The measured and PWIA-calculated cross-section ratios for $^3$He$/d$ and $^3$H$/d$ extend to just above the typical nucleon Fermi-momentum ($k_F \approx 250$ …
High Resolution Spectroscopy ofBΛ12by Electroproduction
An experiment measuring electroproduction of hypernuclei has been performed in Hall A at Jefferson Lab on a $^{12}$C target. In order to increase counting rates and provide unambiguous kaon identification two superconducting septum magnets and a Ring Imaging CHerenkov detector (RICH) were added to the Hall A standard equipment. An unprecedented energy resolution of less than 700 keV FWHM has been achieved. Thus, the observed \lam{12}{B} spectrum shows for the first time identifiable strength in the core-excited region between the ground-state {\it s}-wave $\Lambda$ peak and the 11 MeV {\it p}-wave $\Lambda$ peak.
Virtual Compton scattering and the generalized polarizabilities of the proton atQ2=0.92and 1.76 GeV2
Virtual Compton Scattering (VCS) on the proton has been studied at Jefferson Lab using the exclusive photon electroproduction reaction (e p --> e p gamma). This paper gives a detailed account of the analysis which has led to the determination of the structure functions P{sub LL}-P{sub TT}/epsilon and P{sub LT}, and the electric and magnetic generalized polarizabilities (GPs) alpha{sub E}(Q{sup 2}) and beta{sub M}(Q{sup 2}) at values of the four-momentum transfer squared Q{sup 2} = 0.92 and 1.76 GeV{sup 2}. These data, together with the results of VCS experiments at lower momenta, help building a coherent picture of the electric and magnetic GPs of the proton over the full measured Q{sup 2}-…
Inductively coupled plasma atomic emission spectrometric determination of arsenic in mussel products
A precise, accurate procedure is proposed for the determination of arsenic in mussel products by inductively coupled plasma atomic emission spectrometry. Organic matter is destroyed by dry ashing. Experimental conditions for the determination of arsenic were selected and an interference study was carried out. The methodology developed has a detection limit of 0.1 μg g−1, a relative standard deviation of 3%, and a recovery percentage of 98±2%. The accuracy of the method was checked by analysis of a certified sample of NIST oyster tissue (certified 14.0±1.2 μg g−1; found 14.1±1.1 μg g−1). The proposed procedure was used to analyze real samples of mussel products.
Rosenbluth Separation of the π^{0} Electroproduction Cross Section.
We present deeply virtual $\pi^0$ electroproduction cross-section measurements at $x_B$=0.36 and three different $Q^2$--values ranging from 1.5 to 2 GeV$^2$, obtained from experiment E07-007 that ran in the Hall A at Jefferson Lab. The Rosenbluth technique was used to separate the longitudinal and transverse responses. Results demonstrate that the cross section is dominated by its transverse component, and thus is far from the asymptotic limit predicted by perturbative Quantum Chromodynamics. An indication of a non-zero longitudinal contribution is provided by the interference term $\sigma_{LT}$ also measured. Results are compared with several models based on the leading twist approach of G…
A glimpse of gluons through deeply virtual compton scattering on the proton
The internal structure of nucleons (protons and neutrons) remains one of the greatest outstanding problems in modern nuclear physics. By scattering high-energy electrons off a proton we are able to resolve its fundamental constituents and probe their momenta and positions. Here we investigate the dynamics of quarks and gluons inside nucleons using deeply virtual Compton scattering (DVCS)—a highly virtual photon scatters off the proton, which subsequently radiates a photon. DVCS interferes with the Bethe-Heitler (BH) process, where the photon is emitted by the electron rather than the proton. We report herein the full determination of the BH-DVCS interference by exploiting the distinct energ…
New Measurements of the Transverse Beam Asymmetry for Elastic Electron Scattering from Selected Nuclei
We have measured the beam-normal single-spin asymmetry $A_n$ in the elastic scattering of 1-3 GeV transversely polarized electrons from $^1$H and for the first time from $^4$He, $^{12}$C, and $^{208}$Pb. For $^1$H, $^4$He and $^{12}$C, the measurements are in agreement with calculations that relate $A_n$ to the imaginary part of the two-photon exchange amplitude including inelastic intermediate states. Surprisingly, the $^{208}$Pb result is significantly smaller than the corresponding prediction using the same formalism. These results suggest that a systematic set of new $A_n$ measurements might emerge as a new and sensitive probe of the structure of heavy nuclei.
Backward electroproduction ofπ0mesons on protons in the region of nucleon resonances at four momentum transfer squaredQ2=1.0GeV2
Exclusive electroproduction of pi{sup 0} mesons on protons in the backward hemisphere has been studied at Q2 = 1.0 GeV2 by detecting protons in the forward direction in coincidence with scattered electrons from the 4 GeV electron beam in Jefferson Lab's Hall A. The data span the range of the total (gamma*p) center-of-mass energy W from the pion production threshold to W = 2.0 GeV. The differential cross sections sigma{sub T} + epsilon sigma{sub L}, sigma{sub TL}, and sigma{sub TT} were separated from the azimuthal distribution and are presented together with the MAID and SAID parameterizations.
Rosenbluth separation of the $\pi^0$ Electroproduction Cross Section off the Neutron
We report the first longitudinal/transverse separation of the deeply virtual exclusive $\pi^0$ electroproduction cross section off the neutron and coherent deuteron. The corresponding four structure functions $d\sigma_L/dt$, $d\sigma_T/dt$, $d\sigma_{LT}/dt$ and $d\sigma_{TT}/dt$ are extracted as a function of the momentum transfer to the recoil system at $Q^2$=1.75 GeV$^2$ and $x_B$=0.36. The $ed \to ed\pi^0$ cross sections are found compatible with the small values expected from theoretical models. The $en \to en\pi^0$ cross sections show a dominance from the response to transversely polarized photons, and are in good agreement with calculations based on the transversity GPDs of the nucle…
Virtual Compton Scattering and Neutral Pion Electroproduction in the Resonance Region up to the Deep Inelastic Region at Backward Angles
We have made the first measurements of the virtual Compton scattering (VCS) process via the H$(e,e'p)\gamma$ exclusive reaction in the nucleon resonance region, at backward angles. Results are presented for the $W$-dependence at fixed $Q^2=1$ GeV$^2$, and for the $Q^2$-dependence at fixed $W$ near 1.5 GeV. The VCS data show resonant structures in the first and second resonance regions. The observed $Q^2$-dependence is smooth. The measured ratio of H$(e,e'p)\gamma$ to H$(e,e'p)\pi^0$ cross sections emphasizes the different sensitivity of these two reactions to the various nucleon resonances. Finally, when compared to Real Compton Scattering (RCS) at high energy and large angles, our VCS data…
Deeply virtual compton scattering off the neutron.
The present experiment exploits the interference between the Deeply Virtual Compton Scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D$({\vec e},e'\gamma)X$ cross section measured at $Q^2$=1.9 GeV$^2$ and $x_B$=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to $E_q$, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced.
The quasielastic 2H(e,e'p)n reaction at high recoil momenta
The 2H(e,e'p)n cross section was measured in Hall A of the Thomas Jefferson National Accelerator Facility (JLab) in quasielastic kinematics (x=0.96) at a four-momentum transfer squared, Q^2=0.67 (GeV/c)^2. The experiment was performed in fixed electron kinematics for recoil momenta from zero to 550 MeV/c. Though the measured cross section deviates by 1-2 sigma from a state-of-the-art calculation at low recoil momenta, it agrees at high recoil momenta where final state interactions (FSI) are predicted to be large.
Assessment of the worldwide burden of critical illness: The Intensive Care Over Nations (ICON) audit
Item does not contain fulltext BACKGROUND: Global epidemiological data regarding outcomes for patients in intensive care units (ICUs) are scarce, but are important in understanding the worldwide burden of critical illness. We, therefore, did an international audit of ICU patients worldwide and assessed variations between hospitals and countries in terms of ICU mortality. METHODS: 730 participating centres in 84 countries prospectively collected data on all adult (>16 years) patients admitted to their ICU between May 8 and May 18, 2012, except those admitted for fewer than 24 h for routine postoperative monitoring. Participation was voluntary. Data were collected daily for a maximum of 28 da…
Spectroscopy ofLiΛ9by electroproduction
Background: In the absence of accurate data on the free two-body hyperon-nucleon interaction, the spectra of hypernuclei provides information on the details of the effective hyperon-nucleon interaction.Purpose: To obtain a high-resolution binding-energy spectrum for the ${}^{9}\mathrm{Be}(e,{e}^{\ensuremath{'}}{K}^{+})_{\ensuremath{\Lambda}}^{9}\mathrm{Li}$ reaction.Method: Electroproduction of the hypernucleus $_{\ensuremath{\Lambda}}^{9}\mathrm{Li}$ has been studied for the first time with sub-MeV energy resolution in Hall A at Jefferson Lab on a $^{9}\mathrm{Be}$ target. In order to increase the counting rate and to provide unambiguous kaon identification, two superconducting septum magn…
Measurement of double-polarization asymmetries in the quasi-elastic Process
We report on a precise measurement of double-polarization asymmetries in electron-induced breakup of He3 proceeding to pd and ppn final states, performed in quasi-elastic kinematics at Q2=0.25(GeV/c)2 for missing momenta up to 250MeV/c. These observables represent highly sensitive tools to investigate the electromagnetic and spin structure of He3 and the relative importance of two- and three-body effects involved in the breakup reaction dynamics. The measured asymmetries cannot be satisfactorily reproduced by state-of-the-art calculations of He3 unless their three-body segment is adjusted, indicating that the spin-dependent part of the nuclear interaction governing the three-body breakup pr…
"Table 28" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity dependent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 36" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity dependent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 17" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity independent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 40" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity independent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 39" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity independent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 9" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity independent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 22" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity dependent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 31" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity independent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 34" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity dependent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 33" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity independent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 6" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity dependent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 11" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity independent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 37" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity independent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 29" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity independent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 1" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity independent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 21" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity independent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 25" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity independent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 2" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity dependent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 32" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity dependent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 5" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity independent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 16" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity dependent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 24" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity dependent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 23" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity independent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 14" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity dependent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 26" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity dependent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 20" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity dependent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 8" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity dependent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 10" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity dependent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 13" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity independent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 27" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity independent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 38" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity independent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 35" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity independent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 15" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity independent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 30" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity dependent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 19" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity independent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 12" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity dependent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 4" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity dependent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 3" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity independent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 18" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity dependent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.
"Table 7" of "A glimpse of gluons through deeply virtual compton scattering on the proton"
Beam helicity independent cross sections. The first systematic uncertainty is the combined correlated systematic uncertainty, the second is the point-to-point systematic uncertainty to add quadratically to the statistical uncertainty.