Effect of nuclear transparency from the (p,2p) measurements on 6Li and 12C at 1 GeV

We studied the production of protons to the backward direction in (p,2p) reactions on 6Li and 12C, accompanied by a proton emitted into the forward hemisphere. The momenta of the final two protons were measured in a wide range with the two-arm time-of-flight spectrometer. For each event we reconstructed the mass of the intermediate off-shell particles. We have discovered a strong narrow dip in the mass spectra of intermediate mesons at the mass of the real pion.Comment: 24 pages,11 figure

Properties of the Lambda(1520) Resonance from High-Precision Electroproduction Data

High-resolution spectrometer measurements of the reaction H(e,e'K+)X at small Q2 are used to extract the mass and width of the Lambda(1520). We investigate the influence of various assumptions used in the extraction. The width appears to be more sensitive to the assumptions than the mass. To reach a width uncertainty about 1 MeV or better, one needs to know the structure of the non-resonant background. Based on the new Jefferson Lab Hall A data, our final values for the Breit-Wigner parameters are M = 1520.4 +- 0.6 (stat) +- 1.5 (syst) MeV, Gamma = 18.6 +- 1.9 (stat) +- 1 (syst) MeV. For the first time, we also estimate the pole position for this resonance and find that both the pole mass and width seem to be smaller than the Breit-Wigner values.Comment: 7 pages, 3 figures; corresponds to the published versio

Transactions

ალექსი გორგიძის დაბადებიდან 105 წლისთავისადმი მიძღვნილი შრომათა კრებული. Сборник трудов посвященный к 150 летию со дня рождения Алексея Горгидзе. The collection of works devoted to the 105th anniversary of the birth of the Alexi Gorgidz

High-resolution hypernuclear spectroscopy at Jefferson Lab, Hall A

International audienceThe experiment E94-107 in Hall A at Jefferson Lab started a systematic study of high-resolution hypernuclear spectroscopy in the 0p-shell region of nuclei such as the hypernuclei produced in electroproduction on Be9,C12, and O16 targets. In order to increase counting rates and provide unambiguous kaon identification, two superconducting septum magnets and a ring-imaging Cherenkov detector were added to the Hall A standard equipment. The high-quality beam, the good spectrometers, and the new experimental devices allowed us to obtain very good results. For the first time, measurable strength with sub-MeV energy resolution was observed for the core-excited states of BΛ12. A high-quality NΛ16 hypernuclear spectrum was likewise obtained. A first measurement of the Λ binding energy for NΛ16, calibrated against the elementary reaction on hydrogen, was obtained with high precision, 13.76±0.16 MeV. Similarly, the first LiΛ9 hypernuclear spectrum shows general agreement with theory (distorted-wave impulse approximation with the SLA and BS3 electroproduction models and shell-model wave functions). Some disagreement exists with respect to the relative strength of the states making up the first multiplet. A Λ separation energy of 8.36 MeV was obtained, in agreement with previous results. It has been shown that the electroproduction of hypernuclei can provide information complementary to that obtained with hadronic probes and the γ-ray spectroscopy technique