8 research outputs found
Deep exclusive electroproduction off the proton at CLAS
The exclusive electroproduction of above the resonance region was
studied using the Large Acceptance Spectrometer () at
Jefferson Laboratory by scattering a 6 GeV continuous electron beam off a
hydrogen target. The large acceptance and good resolution of ,
together with the high luminosity, allowed us to measure the cross section for
the process in 140 (, , ) bins:
, 1.6 GeV GeV and 0.1 GeV
GeV. For most bins, the statistical accuracy is on the order of a few
percent. Differential cross sections are compared to two theoretical models,
based either on hadronic (Regge phenomenology) or on partonic (handbag diagram)
degrees of freedom. Both can describe the gross features of the data reasonably
well, but differ strongly in their ingredients. If the handbag approach can be
validated in this kinematical region, our data contain the interesting
potential to experimentally access transversity Generalized Parton
Distributions.Comment: 18pages, 21figures,2table
Decay and Fission Hindrance of Two- and Four-Quasiparticle K Isomers in Rf 254
Two isomers decaying by electromagnetic transitions with half-lives of 4.7(1.1) and 247(73)μs have been discovered in the heavy Rf254 nucleus. The observation of the shorter-lived isomer was made possible by a novel application of a digital data acquisition system. The isomers were interpreted as the Kπ=8-, ν2(7/2+[624],9/2-[734]) two-quasineutron and the Kπ=16+, 8-ν2(7/2+[624],9/2-[734])⊗ - 8-π2(7/2-[514],9/2+[624]) four-quasiparticle configurations, respectively. Surprisingly, the lifetime of the two-quasiparticle isomer is more than 4 orders of magnitude shorter than what has been observed for analogous isomers in the lighter N=150 isotones. The four-quasiparticle isomer is longer lived than the Rf254 ground state that decays exclusively by spontaneous fission with a half-life of 23.2(1.1)μs. The absence of sizable fission branches from either of the isomers implies unprecedented fission hindrance relative to the ground state
Beam spin asymmetry measurements of deeply virtual π0 production with CLAS12
The new experimental measurements of beam spin asymmetry were performed for the deeply virtual exclusive pi0 production in a wide kinematic region with the photon virtualities Q2 up to 6.6 GeV2 and the Bjorken scaling variable xB in the valence regime. The data were collected by the CEBAF Large Acceptance Spectrometer (CLAS12) at Jefferson Lab with longitudinally polarized 10.6 GeV electrons scattered on an unpolarized liquid-hydrogen target. Sizable asymmetry values indicate a substantial contribution from transverse virtual photon amplitudes to the polarized structure functions. The interpretation of these measurements in terms of the Generalized Parton Distributions (GPDs) demonstrates their sensitivity to the chiral-odd GPD ET, which contains information on quark transverse spin densities in unpolarized and polarized nucleons and provides access to the nucleon's transverse anomalous magnetic moment. Additionally, the data were compared to a theoretical model based on a Regge formalism that was extended to the high photon virtualities
Spontaneous abortions and malformations in the offspring of nurses exposed to anaesthetic gases, cytostatic drugs, and other potential hazards in hospitals, based on registered information of outcome.
Decay and Fission Hindrance of Two- and Four-Quasiparticle K Isomers in 254Rf
Two isomers decaying by electromagnetic transitions with half-lives of 4.7(1.1) and 247ð73Þ μs
have been discovered in the heavy 254Rf nucleus. The observation of the shorter-lived isomer was made
possible by a novel application of a digital data acquisition system. The isomers were interpreted as the
Kπ ¼ 8−, ν2ð7=2þ½624; 9=2−½734Þ two-quasineutron and the Kπ ¼ 16þ, 8−ν2ð7=2þ½624; 9=2−½734Þ ⊗
8−π2ð7=2−½514; 9=2þ½624Þ four-quasiparticle configurations, respectively. Surprisingly, the lifetime of
the two-quasiparticle isomer is more than 4 orders of magnitude shorter than what has been observed for
analogous isomers in the lighter N ¼ 150 isotones. The four-quasiparticle isomer is longer lived than the
254Rf ground state that decays exclusively by spontaneous fission with a half-life of 23.2ð1.1Þ μs. The
absence of sizable fission branches from either of the isomers implies unprecedented fission hindrance
relative to the ground state.peerReviewe