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S. Marrone

Publications and source records attributed to S. Marrone.

25 records · Page 2Linked to original sources
arXiv2009

Cross sections and Rosenbluth separations in 1H(e, e'K+)Lambda up to Q2=2.35 GeV2

The kaon electroproduction reaction 1H(e,e'K+)Lambda was studied as a function of the virtual-photon four-momentum, Q2, total energy, W, and momentum transfer, t, for different values of the virtual- photon polarization parameter. Data were taken at electron beam energies ranging from 3.40 to 5.75 GeV. The center of mass cross section was determined for 21 kinematics corresponding to Q2 of 1.90 and 2.35 GeV2 and the longitudinal, sigmaL, and transverse, sigmaT, cross sections were separated using the Rosenbluth technique at fixed W and t. The separated cross sections reveal a flat energy dependence at forward kaon angles not satisfactorily described by existing electroproduction models. Influence of the kaon pole on the cross sections was investigated by adopting an off-shell form factor in the Regge model which better describes the observed energy dependence of sigmaT and sigmaL.

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arXiv2009

High Resolution Spectroscopy of 16N_Lambda by Electroproduction

An experimental study of the 16O(e,e'K^+)16N_Lambda reaction has been performed at Jefferson Lab. A thin film of falling water was used as a target. This permitted a simultaneous measurement of the p(e,e'K^+)Lambda,Sigma_0 exclusive reactions and a precise calibration of the energy scale. A ground-state binding energy of 13.76 +/- 0.16 MeV was obtained for 16N_Lambda with better precision than previous measurements on the mirror hypernucleus 16O_Lambda. Precise energies have been determined for peaks arising from a Lambda in s and p orbits coupled to the p_{1/2} and p_{3/2} hole states of the 15N core nucleus.

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arXiv2009

Probing Cold Dense Nuclear Matter

The protons and neutrons in a nucleus can form strongly correlated nucleon pairs. Scattering experiments, where a proton is knocked-out of the nucleus with high momentum transfer and high missing momentum, show that in 12C the neutron-proton pairs are nearly twenty times as prevalent as proton-proton pairs and, by inference, neutron-neutron pairs. This difference between the types of pairs is due to the nature of the strong force and has implications for understanding cold dense nuclear systems such as neutron stars.

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arXiv2008

Performance of the Two Aerogel Cherenkov Detectors of the JLab Hall A Hadron Spectrometer

We report on the design and commissioning of two silica aerogel Cherenkov detectors with different refractive indices. In particular, extraordinary performance in terms of the number of detected photoelectrons was achieved through an appropriate choice of PMT type and reflector, along with some design considerations. After four years of operation, the number of detected photoelectrons was found to be noticeably reduced in both detectors as a result of contamination, yellowing, of the aerogel material. Along with the details of the set-up, we illustrate the characteristics of the detectors during different time periods and the probable causes of the contamination. In particular we show that the replacement of the contaminated aerogel and parts of the reflecting material has almost restored the initial performance of the detectors.

physics.ins-det↗
arXiv2008

Chemical Analyses of Silicon Aerogel Samples

After five years of operating, two Aerogel counters: A1 and A2, taking data in Hall A at Jefferson Lab, suffered a loss of performance. In this note possible causes of degradation have been studied. In particular, various chemical and physical analyses have been carried out on several Aerogel tiles and on adhesive tape in order to reveal the presence of contaminants.

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arXiv2007

High Resolution Spectroscopy of 12B_Lambda by 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 $Λ$ peak and the 11 MeV {\it p}-wave $Λ$ peak.

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