227 research outputs found
Measurement of the EMC effect in the deuteron
We determined the structure function ratio R-EMC(d) = F-2(d)/(F-2(n) + F-2(p)) from recently published F-2(n)/F-2(d) data taken by the BONuS experiment using CLAS at Jefferson Lab. This ratio deviates from unity, with a slope dR(EMC)(d)/dx=-0.10 +/- 0.05 in the range of Bjorken x from 0.35 to 0.7, for invariant mass W \u3e 1.4 GeV and Q(2) \u3e 1GeV(2). The observed EMC effect for these kinematics is consistent with conventional nuclear physics models that include off-shell corrections, as well as with empirical analyses that find the EMC effect proportional to the probability of short-range nucleon-nucleon correlation
Measurement of the EMC Effect in the Deuteron
We determined the structure function ratio RdEMC=Fd2/(Fn2+Fp2) from recently published Fn2/Fd2 data taken by the BONuS experiment using CLAS at Jefferson Lab. This ratio deviates from unity, with a slope dRdEMC/dx=−0.10 ± 0.05 in the range of Bjorken x from 0.35 to 0.7, for invariant mass W\u3e1.4 GeV and Q2\u3e1 GeV2 . The observed EMC effect for these kinematics is consistent with conventional nuclear physics models that include off-shell corrections, as well as with empirical analyses that find the EMC effect proportional to the probability of short-range nucleon-nucleon correlations
First Measurement of Target And Double Spin Asymmetries for ep → epπ° in the Nucleon Resonance Region Above the Δ (1232)
The exclusive channel polarized proton(polarized e,e\u27 p)π0 was studied in the first and second nucleon resonance regions in the Q2 range from 0.187 to 0.770 GeV2 at Jefferson Lab using the CEBAF Large Acceptance Spectrometer (CLAS). Longitudinal target and beam-target asymmetries were extracted over a large range of center-of-mass angles of the π0 and compared to the unitary isobar model MAID, the dynamic model by Sato and Lee, and the dynamic model DMT. A strong sensitivity to individual models was observed, in particular for the target asymmetry and in the higher invariant mass region. This data set, once included in the global fits of the above models, is expected to place strong constraints on the electrocoupling amplitudes A 1/2 and S 1/2 for the Roper resonance N (1400) P11, and the N(1535)S11 and N(1520)D13 states
Transmission of High-Power Electron Beams Through Small Apertures
Tests were performed to pass a 100 MeV, 430 kWatt c.w. electron beam from the
energy-recovery linac at the Jefferson Laboratory's FEL facility through a set
of small apertures in a 127 mm long aluminum block. Beam transmission losses of
3 p.p.m. through a 2 mm diameter aperture were maintained during a 7 hour
continuous run.Comment: arXiv admin note: text overlap with arXiv:1305.019
Measured Radiation and Background Levels During Transmission of Megawatt Electron Beams Through Millimeter Apertures
We report measurements of photon and neutron radiation levels observed while
transmitting a 0.43 MW electron beam through millimeter-sized apertures and
during beam-off, but accelerating gradient RF-on, operation. These measurements
were conducted at the Free-Electron Laser (FEL) facility of the Jefferson
National Accelerator Laboratory (JLab) using a 100 MeV electron beam from an
energy-recovery linear accelerator. The beam was directed successively through
6 mm, 4 mm, and 2 mm diameter apertures of length 127 mm in aluminum at a
maximum current of 4.3 mA (430 kW beam power). This study was conducted to
characterize radiation levels for experiments that need to operate in this
environment, such as the proposed DarkLight Experiment. We find that sustained
transmission of a 430 kW continuous-wave (CW) beam through a 2 mm aperture is
feasible with manageable beam-related backgrounds. We also find that during
beam-off, RF-on operation, multipactoring inside the niobium cavities of the
accelerator cryomodules is the primary source of ambient radiation when the
machine is tuned for 130 MeV operation.Comment: 9 pages, 11 figures, submitted to Nuclear Instruments and Methods in
Physics Research Section
Measurement of Direct fₒ(980) Photoproduction on the Proton
We report on the results of the first measurement of exclusive f0(980) meson photoproduction on protons for Eγ = 3.0–3.8 GeV and −t = 0.4–1.0 GeV2 . Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. The resonance was detected via its decay in the π+π− channel by performing a partial wave analysis of the reaction γp→pπ+π− . Clear evidence of the f0(980) meson was found in the interference between P and S waves at M π+π− ∼1 GeV. The S -wave differential cross section integrated in the mass range of the f0(980) was found to be a factor of about 50 smaller than the cross section for the ρ meson. This is the first time the f0(980) meson has been measured in a photoproduction experiment
Cascade Production in the Reactions p → K⁺ K⁺(X) and p → K⁺K⁺ π⁻⁻(X)
Photoproduction of the cascade resonances has been investigated in the reactions γp → K + K +(X) and γp → K + K + π −(X). The mass splitting of the ground state (Ξ−,Ξ0) doublet is measured to be 5.4 ± 1.8 MeV/c2, consistent with existing measurements. The differential (total) cross sections for the Ξ− have been determined for photon beam energies from 2.75 to 3.85 (4.75) GeV and are consistent with a production mechanism of Y∗→K+Ξ− through a t-channel process. The reaction γp→K+K+π−[Ξ0] has also been investigated to search of excited cascade resonances. No significant signal of excited cascade states other than the Ξ−(1530) is observed. The cross-section results of the Ξ−(1530) have also been obtained for photon beam energies from 3.35 to 4.75 GeV
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