The neutron elastic magnetic form factor was extracted from quasielastic electron scattering on deuterium over the range Q2=1.0-4.8 GeV2 with the CLAS detector at Jefferson Lab. High precision was ...achieved with a ratio technique and a simultaneous in situ calibration of the neutron detection efficiency. Neutrons were detected with electromagnetic calorimeters and time-of-flight scintillators at two beam energies. The dipole parametrization gives a good description of the data.
Light vector mesons in the nuclear medium Wood, M. H.; Mosel, U.; Muehlich, P. ...
Physical review. C, Nuclear physics,
07/2008, Letnik:
78, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The light vector mesons ({rho},{omega}, and {phi}) were produced in deuterium, carbon, titanium, and iron targets in a search for possible in-medium modifications to the properties of the {rho} meson ...at normal nuclear densities and zero temperature. The vector mesons were detected with the CEBAF Large Acceptance Spectrometer (CLAS) via their decays to e{sup +}e{sup -}. The rare leptonic decay was chosen to reduce final-state interactions. A combinatorial background was subtracted from the invariant mass spectra using a well-established event-mixing technique. The {rho}-meson mass spectrum was extracted after the {omega} and {phi} signals were removed in a nearly model-independent way. Comparisons were made between the {rho} mass spectra from the heavy targets (A>2) with the mass spectrum extracted from the deuterium target. With respect to the {rho}-meson mass, we obtain a small shift compatible with zero. Also, we measure widths consistent with standard nuclear many-body effects such as collisional broadening and Fermi motion.
We report measurements of the beam spin asymmetry in deeply virtual Compton scattering (DVCS) at an electron beam energy of 4.8 GeV using the CLAS detector at the Thomas Jefferson National ...Accelerator Facility. The DVCS beam spin asymmetry has been measured in a wide range of kinematics, 1.0<Q{sup 2}<2.8 (GeV/c){sup 2}, 0.12<x{sub B}<0.48, and 0.1<-t<0.8 (GeV/c){sup 2}, using the reaction e-vector p{yields}e{sup '}pX. The number of H(e,e{sup '}{gamma}p) and H(e,e{sup '}{pi}{sup 0}p) events are separated in each (Q{sup 2},x{sub B},t) bin by a fit to the line shape of the H(e,e{sup '}p)X M{sub x}{sup 2} distribution. The validity of the method was studied in detail using experimental and simulated data. It was shown that with the achieved missing mass squared resolution and the available statistics, the separation of DVCS-Bethe-Heitler and {pi}{sup 0} events can reliably be done with less than 5% uncertainty. Also, the Q{sup 2} and t dependences of the sin{phi} moments of the asymmetry are extracted and compared with theoretical calculations.
The 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 Be-9, C-12, and O-16 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 B-12(Lambda). A high-quality N-16(Lambda) hypernuclear spectrum was likewise obtained. A first measurement of the Lambda binding energy for N-16(Lambda), calibrated against the elementary reaction on hydrogen, was obtained with high precision, 13.76 +/- 0.16 MeV. Similarly, the first Li-9(Lambda) 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 Lambda 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 gamma-ray spectroscopy technique.
The 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 Be-9, C-12, and O-16 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 B-12(Lambda). A high-quality N-16(Lambda) hypernuclear spectrum was likewise obtained. A first measurement of the Lambda binding energy for N-16(Lambda), calibrated against the elementary reaction on hydrogen, was obtained with high precision, 13.76 +/- 0.16 MeV. Similarly, the first Li-9(Lambda) 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 Lambda 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 gamma-ray spectroscopy technique.
AIM： To establish the extent to which contrast enhancement with SonoVue in combination with quantitative evaluation of contrast-medium dynamics facilitates the detection of hepatic tumors.
METHODS： ...One hundred patients with histologically confirmed malignant or benign hepatic tumor （maximum size 5 cm） were analyzed. Contrast-enhanced ultrasound （bolus injection 2.5 mL SonoVue） was carried out with intermittent breath-holding technique using a multifrequency transducer （2.5-4 MHz）. Native vascularization was analyzed with power Doppler. The contrast-enhanced dynamic ultrasound investigation was carried out with contrast harmonic imaging in true detection mode during the arterial, portal venous and late phases. Mechanical index was set at 0.15. Perfusion analysis was performed by post-processing of the raw data time intensity curve （TIC） analysis. The cutoff of the gray value differences between tumor and normal liver tissue was established using Receiver Operating Characteristic （ROC） analysis 64-line multislice computed tomography served as reference method in all cases. Magnetic resonance tomography was used additionally in 19 cases.
RESULTS： One hundred patients with 59 malignant （43 colon, 5 breast, 2 endocrine metastases, 7 hepatocellular carcinomas and 2 kidney cancers） and 41 benign （15 hemangiomas, 7 focal nodular hyperplasias, 5 complicated cysts, 2 abscesses and 12 circumscribed fatty changes） tumors were included. The late venous phase proved to be the most sensitive for classification of the tumor type. Fifty-eight of the 59 malignant tumors were classified as true positive, and one as false negative. This resulted in a sensitivity of 98.3%. Of the 41 benign tumors, 37 were classified as true negative and 4 as false negative, which corresponds to a specificity of 90.2%. Altogether, 95.0% of the diagnoses were classified as correct on the basis of the histological classification. No investigator-dependency （P = 0.23）was noted.
CONCLUSION： The results show the possibility of accurate prediction of malignancy of hepatic tumors with a positive prognostic value of 93.5% using advanced contrast-enhanced ultrasound. Contrast enhancement with SonoVue in combination with quantitative evaluation of contrast-medium dynamics is a valuable tool to discriminate hepatic tumors.
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