The new experimental measurements of beam spin asymmetry were performed for the deeply virtual exclusive $π$0 production in a wide kinematic region with the photon virtualities $Q$2 up to 8 GeV2 and ...the Bjorken scaling variable $x$$B$ in the valence regime. The data were collected by the CE BAF Large Acceptance Spectrometer (CLAS12) at Jefferson Lab with longitudinally polarized 10.6 GeV electrons scattered on an unpolarized liquid-hydrogen target. Sizable asymmetry values indicate a substantial contribution from transverse virtual photon amplitudes to the polarized structure functions. The interpretation of these measurements in terms of the Generalized Parton Distributions (GPDs) demonstrates their sensitivity to the chiral-odd GPD $\overline{E}$$T$, which contains information on quark transverse spin densities in unpolarized and polarized nucleons and provides access to the proton’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.
We report measurements of π+ and π0 meson photoproduction from longitudinally spin-polarised protons by an energy tagged (0.73-2.3 GeV) and linearly polarised photon beam. A close to complete solid ...angle coverage for the reaction products was provided by the CEBAF Large Acceptance Spectrometer at Jefferson Laboratory. The double-polarisation observable G is extracted from Maximum Likelihood fits to the data, enabling the first accurate determination for the reaction γ→p→→π+n, while also significantly extending the kinematic coverage for γ→p→→π0p. This large data set provides an important constraint on the properties and spectrum of excited nucleon states decaying to Nπ in the mass range from 1.4 to 2.2 GeV, as well as for background (non-resonant) photoproduction processes. The considerable improvement achieved in the description of the observable G within the SAID and Bonn-Gatchina approaches after implementation of our data, illustrates that the partial-wave analyses now significantly extend the knowledge on Nπ photoproduction amplitudes at W>1.8 GeV. A partial-wave analysis using the new high-precision data set has a large impact on the extracted properties of high-spin nucleon excited states.
We report measurements of p+ and p0 meson photoproduction from longitudinally spin-polarised protons by an energy tagged (0.73-2.3 GeV) and linearly polarised photon beam. A close to complete solid ...angle coverage for the reaction products was provided by the CEBAF Large Acceptance Spectrometer at Jefferson Laboratory. The double-polarisation observable G is extracted from Maximum Likelihood fits to the data, enabling the first accurate determination for reaction ~ ~p ! ?+n while also significantly extending the kinematic coverage for ~ ~ ~p ! ?0p. This large data set provides an important constraint on the properties and spectrum of excited nucleon states decaying to Npi in the mass range from 1.4 to 2.2 GeV, as well as for background (non-resonant) photoproduction processes. The considerable improvement achieved in the description of the observable G within the SAID and Bonn-Gatchina approaches after implementation of our data, illustrates that the partial wave analyses now significantly extend the knowledge on Npi photoproduction amplitudes at W > 1:8 GeV. A partial wave analysis using the new high-precision data set have a large impact on the extracted properties of high-spin nucleon excited states.
Deeply virtual Compton scattering (DVCS) allows one to probe Generalized Parton Distributions (GPDs) describing the 3D structure of the nucleon. We report the first measurement of the DVCS beam-spin ...asymmetry using the CLAS12 spectrometer with a 10.2 and 10.6 GeV electron beam scattering from unpolarised protons. The results greatly extend the \(Q^2\) and Bjorken-\(x\) phase space beyond the existing data in the valence region and provide over 2000 new data points measured with unprecedented statistical uncertainty, setting new, tight constraints for future phenomenological studies.
We report the first measurements of deep inelastic scattering spin-dependent azimuthal asymmetries in back-to-back dihadron electroproduction, where two hadrons are produced in opposite hemispheres ...along the z-axis in the center-of-mass frame, with the first hadron produced in the current-fragmentation region and the second in the target-fragmentation region. The data were taken with longitudinally polarized electron beams of 10.2 and 10.6 GeV incident on an unpolarized liquid-hydrogen target using the CLAS12 spectrometer at Jefferson Lab. Observed non-zero \(\sin\Delta\phi\) modulations in \(ep \rightarrow e'p\pi^+X\) events, where \(\Delta\phi\) is the difference of the azimuthal angles of the proton and pion in the virtual photon and target nucleon center-of-mass frame, indicate that correlations between the spin and transverse momenta of hadrons produced in the target- and current-fragmentation regions may be significant. The measured beam-spin asymmetries provide a first access in dihadron production to a previously unobserved leading-twist spin- and transverse-momentum-dependent fracture function. The fracture functions describe the hadronization of the target remnant after the hard scattering of a virtual photon off a quark in the target particle and provide a new avenue for studying nucleonic structure and hadronization.
PANDA Phase One Davì, F; Montalto, L; Krusche, B ...
arXiv.org,
06/2021
Paper, Journal Article
Odprti dostop
The Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, provides unique possibilities for a new generation of hadron-, nuclear- and atomic physics experiments. The future ...antiProton ANnihilations at DArmstadt (PANDA or \(\overline{\rm P}\)ANDA) experiment at FAIR will offer a broad physics programme, covering different aspects of the strong interaction. Understanding the latter in the non-perturbative regime remains one of the greatest challenges in contemporary physics. The antiproton-nucleon interaction studied with PANDA provides crucial tests in this area. Furthermore, the high-intensity, low-energy domain of PANDA allows for searches for physics beyond the Standard Model, e.g. through high precision symmetry tests. This paper takes into account a staged approach for the detector setup and for the delivered luminosity from the accelerator. The available detector setup at the time of the delivery of the first antiproton beams in the HESR storage ring is referred to as the \textit{Phase One} setup. The physics programme that is achievable during Phase One is outlined in this paper.
Novel device to study double-alpha decay at the FRS Ion Catcher Varga, L.; Wilsenach, H.; Hall, O. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2024, Letnik:
1063
Journal Article
Recenzirano
Odprti dostop
A novel system has been developed to detect simultaneous double-alpha emission from purified and weightless sources. The system includes the collection of 224Ra low-energy recoils in purified helium ...buffer gas from the decay of 228Th. The recoil products are thermalized and collected in a cryogenic buffer gas cell and extracted into an RF-ion guide for mass selection. The mass-separated ions are implanted at low kinetic energy into a thin carbon foil placed between two large-area double-sided silicon strip detectors to observe correlated alpha-particle emission. The apparatus is described in detail, including insights into its experimental performance.
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