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1.
Phys Rev Lett ; 103(20): 202501, 2009 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-20365979

RESUMO

An experimental study of the (16)O(e,e'K(+))(Lambda)(16)N 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 (Lambda)(16)N with better precision than previous measurements on the mirror hypernucleus (Lambda)(16)O. 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 (15)N core nucleus.

2.
Appl Radiat Isot ; 69(8): 1118-20, 2011 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-21131207

RESUMO

The "standard" Hall A apparatus at Jefferson Lab (TOF and aerogel threshold Cherenkov detectors) does not provide complete identification for proton, kaon and pion. To this aim, a proximity focusing C(6)F(14)/CsI RICH (Ring Image CHerenkov) detector has been designed, built, tested and operated to separate kaons from pions with a pion contamination of a few percent up to 2.4GeV/c. Two quite different experimental investigations have benefitted of the RICH identification: on one side, the high-resolution hypernuclear spectroscopy series of experiments on carbon, beryllium and oxygen, devoted to the study of the lambda-nucleon potential. On the other side, the measurements of the single spin asymmetries of pion and kaon on a transversely polarized (3)He target are of utmost interest in understanding QCD dynamics in the nucleon. We present the technical features of such a RICH detector and comment on the presently achieved performance in hadron identification.


Assuntos
Elétrons , Partículas Elementares , Mésons , Prótons , Berílio/química , Carbono/química , Interações de Partículas Elementares , Desenho de Equipamento , Método de Monte Carlo , Física Nuclear , Oxigênio/química , Análise Espectral
3.
Appl Radiat Isot ; 69(8): 1125-7, 2011 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-21145242

RESUMO

The ratio of the electromagnetic proton elastic form factors, G(p)(E)/G(p)(M), has been measured at Jefferson Lab up to Q(2) approximately 9(GeV/c)(2), by using the CEBAF 6GeV electron beam, and revealing an unexpected and challenging physical behaviour. The 2014 scheduled 12GeV upgrade will allow the measurement of G(p)(E)/G(p)(M) up to Q(2) approximately 15(GeV/c)(2), by taking advantage of the new large-acceptance forward spectrometer Super BigBite (SBS) in Hall A. Measurements of neutron form factors in the region around 10(GeV/c)(2), where quark confinement plays an important role, are expected to show the behaviour already observed in the proton case.


Assuntos
Partículas Elementares , Prótons , Monitoramento de Radiação/instrumentação , Análise Espectral/instrumentação , Elétrons , Interações de Partículas Elementares , Desenho de Equipamento , Nêutrons
4.
Phys Rev Lett ; 98(18): 182302, 2007 May 04.
Artigo em Inglês | MEDLINE | ID: mdl-17501566

RESUMO

We measured the angular dependence of the three recoil-proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily. Transverse polarizations are not well described, but suggest isovector dominance.

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