398 research outputs found
Genuine and simulated suicide notes: An analysis of content
No full textThe present study examined genuine and simulated suicide notes aiming to identify the measures of content that best differentiate between the two. Thirty-three genuine and thirty-three simulated suicide notes were content-analysed and data subjected to smallest space analysis (SSA), a Multidimensional Scaling Procedure. The core of all suicide notes was discovered to be constructed with the use of three variables: expressions of love, positive construction of partner and apologies. Furthermore, four different genuine suicide note themes (‘planned escape’, ‘negative affect and self-mitigation’, ‘positive affect and failed relationship’, ‘lack of self-acceptance’) and three simulated suicide note themes (‘escape’, ‘positive affect and self-blame’, ‘purposeless life’) were identified revealing that authentic suicide note themes were more internally consistent and clearer to interpret
Studies of light charged particle emission from fission and ER reactions in the system 344 MeV 28Si + 121Sb -> 149Tb (E* = 240 MeV)
No full textLight charged particles (LCP) have been measured for the reaction 344 MeV 28Si+121Sb in singles and in coincidence with evaporation residues (ER), fusion–fission fragments (FF), and other LCP. A major feature of this experiment was the use of a gas-filled magnetic spectrometer in the forward direction to separate ER from the much more abundant yield of elastically scattered projectiles and projectile-like fragments. The dominant sources of evaporative 1H and 4He emission are the ER (approximately 75%), with the remainder being largely associated with fission reactions. For these latter reactions, most of the 1H and 4He can be well accounted for by evaporation from the composite system prior to fission and by evaporation from the postfission fragments. LCP emission cross sections were determined for each identified source, and a comparison has been made to previous studies. From this comparison, indications were found for significant entrance channel effects, with the more asymmetric channels exhibiting much larger LCP cross sections. Statistical model predictions for ER emissions are in good agreement with observed LCP energy spectra, angular distributions, and integrated inclusive and exclusive cross sections, with all calculations using the same unique set of model parameters. This result contrasts strongly with recent reports for light mass systems, where model calculations were unable to simultaneously reproduce all observables
Beam Spin Asymmetries in Deeply Virtual Compton Scattering (DVCS) with CLAS at 4.8 GeV
No full textWe 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 \u3c Q2 \u3c 2.8 (GeV/c)2, 0.12 \u3c xB \u3c 0.48, and 0.1 \u3c −t \u3c 0.8 (GeV/c)2, using the reaction ep → e\u27 p X. The number of H(e, e\u27 γ p) and H(e, e\u27π0p) events are separated in each (Q2, xB, t) bin by a fit to the line shape of the H(e, e\u27 p)X M2x 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 π0 events can reliably be done with less than 5% uncertainty. Also, the Q2 and t dependences of the sin φ moments of the asymmetry are extracted and compared with theoretical calculations
First Results on Nucleon Resonance Photocouplings from the γp → π+π−p reaction
No full textWe report the first experimental measurements of the nine 1-fold differential cross sections for the γp → π+π−p reaction, obtained with the CLAS detector at Jefferson Laboratory. The measurements cover the invariant mass range of the final state hadrons from 1.6 GeV \u3c W \u3c 2.0 GeV. For the first time the photocouplings of all prominent nucleon resonances in this mass range have been extracted from this exclusive channel. Photoproduction of two charged pions is of particular importance for the evaluation of the photocouplings for the ∆1620)1/2- , ∆(1700)3/2- , N(1720)3/2+, and ∆(1905)5/2+ resonances, which have dominant decays into the ππN final states rather than the more extensively studied single meson decay channels. (C) 2018 The Author. Published by Elsevier B.V
Partial wave analysis of the reaction gamma p ---> p omega and the search for nucleon resonances
No full textAn event-based partial wave analysis (PWA) of the reaction gamma p -> p omega has been performed on a high-statistics dataset obtained using the CLAS at Jefferson Lab for center-of-mass energies from threshold up to 2.4 GeV. This analysis benefits from access to the world's first high-precision spin-density matrix element measurements, available to the event-based PWA through the decay distribution of omega ->pi(+)pi(-)pi(0). The data confirm the dominance of the t-channel pi(0) exchange amplitude in the forward direction. The dominant resonance contributions are consistent with the previously identified states F(15)(1680) and D(13)(1700) near threshold, as well as the G(17)(2190) at higher energies. Suggestive evidence for the presence of a J(P)=5/2(+) state around 2 GeV, a "missing" state, has also been found. Evidence for other states is inconclusive
Double Polarisation Observable G for Single Pion Photoproduction from the Proton.
No full textWe report measurements of π + and π 0 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 (gamma) over right arrow(rho) over right arrow -\u3e pi(+)n, while also significantly extending the kinematic coverage for (gamma) over right arrow(rho) over right arrow -\u3e pi(0)p. 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 \u3e 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
Precise measurements of beam spin asymmetries in semi-inclusive pi(0) production
No full textWe present studies of single-spin asymmetries for neutral pion electroproduction in semi-inclusive deep-inelastic scattering of 5.776 GeV polarized electrons from an unpolarized hydrogen target, using the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. A substantial sin phi(h) amplitude has been measured in the distribution of the cross section asymmetry as a function of the azimuthal angle phi(h) of the produced neutral pion. The dependence of this amplitude on Bjorken x and on the pion transverse momentum is extracted with significantly higher precision than previous data and is compared to model calculations. (C) 2011 Elsevier B.V. All rights reserved.</p
First CLAS12 Measurement of Deeply Virtual Compton Scattering Beam-Spin Asymmetries in the Extended Valence Region
No full textDeeply virtual Compton scattering (DVCS) allows one to probe generalized parton distributions 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 unpolarized protons. The results greatly extend the 2 and Bjorken- phase space beyond the existing data in the valence region and provide 1600 new data points measured with unprecedented statistical uncertainty, setting new, tight constraints for future phenomenological studies
Electroexcitation of Nucleon Resonances from CLAS Data on Single Pion Electroproduction
No full textWe present results on the electroexcitation of the low mass resonances ∆(1232)P33, N(1440)P11, N(1520)D13, and N(1535)S11 in a wide range of Q2. The results were obtained in the comprehensive analysis of data from the Continuous Electron Beam Accelerator Facility (CEBAF) large acceptance spectrometer (CLAS) detector at the Thomas Jefferson National Accelerator Facility (JLab) on differential cross sections, longitudinally polarized beam asymmetries, and longitudinal target and beam-target asymmetries for π electroproduction off the proton. The data were analyzed using two conceptually different approaches—fixed-t dispersion relations and a unitary isobar model—allowing us to draw conclusions on the model sensitivity of the obtained electrocoupling amplitudes. The amplitudes for the ∆(1232)P33 show the importance of a meson-cloud contribution to quantitatively explain the magnetic dipole strength, as well as the electric and scalar quadrupole transitions. They do not show any tendency of approaching the pQCD regime for Q2 ≤ 6 GeV2. For the Roper resonance, N(1440)P11, the data provide strong evidence that this state is a predominantly radial excitation of a three-quark (3q) ground state. Measured in pion electroproduction, the transverse helicity amplitude for the N(1535)S11 allowed us to obtain the branching ratios of this state to the πN and ηN channels via comparison with the results extracted from η electroproduction. The extensive CLAS data also enabled the extraction of the γ*p → N(1520)D13 and N(1535)S11 longitudinal helicity amplitudes with good precision. For the N(1535)S11, these results became a challenge for quark models and may be indicative of large meson-cloud contributions or of representations of this state that differ from a 3q excitation. The transverse amplitudes for the N(1520)D13 clearly show the rapid changeover from helicity-3/2 dominance at the real photon point to helicity-1/2 dominance at Q2 \u3e 1 GeV2, confirming a long-standing prediction of the constituent quark model
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