546 research outputs found

    High energy solar neutrinos and p-wave contributions to ^3He(p,\nue^+)^4He

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    High energy solar neutrinos can come from the hep reaction ^3He(p,\nue^+)^4He with a large end point energy of 18.8 MeV. Understanding the hep reaction may be important for interpreting solar neutrino spectra. We calculate the contribution of the axial charge transition 3P0→1S0^3P_0\to ^1S_0 to the hep thermonuclear S factor using a one-body reaction model involving a nucleon moving in optical potentials. Our result is comparable to or larger than previous calculations of the s-wave Gamow Teller contribution. This indicates that the hep reaction may have p-wave strength leading to an enhancement of the S factor.Comment: 4 pages, 1 ps figure, very minor changes, Phys. Rev. C in pres

    Realistic Calculation of the hep Astrophysical Factor

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    The astrophysical factor for the proton weak capture on 3He is calculated with correlated-hyperspherical-harmonics bound and continuum wave functions corresponding to a realistic Hamiltonian consisting of the Argonne v18 two-nucleon and Urbana-IX three-nucleon interactions. The nuclear weak charge and current operators have vector and axial-vector components, that include one- and many-body terms. All possible multipole transitions connecting any of the p-3He S- and P-wave channels to the 4He bound state are considered. The S-factor at a p-3He center-of-mass energy of 10 keV, close to the Gamow-peak energy, is predicted to be 10.1 10^{-20} keV b, a factor of five larger than the standard-solar-model value. The P-wave transitions are found to be important, contributing about 40 % of the calculated S-factor.Comment: 8 pages RevTex file, submitted to Phys. Rev. Let

    Centrality Dependence of Charged Particle Multiplicity at Mid-Rapidity in Au+Au Collisions at sqrt(s_NN) = 130 GeV

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    We present a measurement of the pseudorapidity density of primary charged particles near mid-rapidity in Au+Au collisions at sqrt(s_NN) = 130 GeV as a function of the number of participating nucleons. These results are compared to models in an attempt to discriminate between competing scenarios of particle production in heavy ion collisions.Comment: 5 pages, 4 figures, revtex (submitted to Phys. Rev. Letters

    Ratios of charged antiparticles to particles near mid-rapidity in Au+Au collisions at sqrt(s_NN) = 130 GeV

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    We have measured the ratios of antiparticles to particles for charged pions, kaons and protons near mid-rapidity in central Au+Au collisions at sqrt(s_NN) = 130 GeV. For protons, we observe pbar/p = 0.60 +/- 0.04 (stat.) +/- 0.06 (syst.) in the transverse momentum range 0.15 < p_T < 1.0 GeV/c. This leads to an estimate of the baryo-chemical potential mu_B of 45 MeV, a factor of 5-6 smaller than in central Pb+Pb collisions at sqrt(s_NN) = 17.2 GeV.Comment: 4 page

    The significance of the fragmentation region in ultrarelativistic heavy ion collisions

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    We present measurements of the pseudorapidity distribution of primary charged particles produced in Au+Au collisions at three energies, sqrt(s_{NN}) = 19.6, 130, and 200 GeV, for a range of collision centralities. The centrality dependence is shown to be non-trivial: the distribution narrows for more central collisions and excess particles are produced at high pseudorapidity in peripheral collisions. For a given centrality, however, the distributions are found to scale with energy according to the "limiting fragmentation" hypothesis. The universal fragmentation region described by this scaling grows in pseudorapidity with increasing collision energy, extending well away from the beam rapidity and covering more than half of the pseudorapidity range over which particles are produced. This approach to a universal limiting curve appears to be a dominant feature of the pseudorapidity distribution and therefore of the total particle production in these collisions.Comment: 5 pages, 4 figure

    Case vignettes for a European comparison of structures and common pathways to formal care

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    Background: People with dementia and their informal carers often do not receive appropriate professional support or it is not received at the right time. Objectives: Description and comparison of common pathways to formal community dementia care in eight European countries as a part of the transnational Actifcare project. Materials and methods: The German team was responsible for creating an individual case scenario as a starting point. The research teams in Ireland, Italy, the Netherlands, Norway, Portugal, Sweden, and the United Kingdom were then asked to describe a common pathway to formal dementia care by writing their own vignette using the provided individual case scenario. Results: A transnational qualitative content analysis was used to identify the following categories as being the most important: involved professionals, dementia-specific and team-based approaches, proactive roles, and financial aspects. General practitioners (GPs) are described as being the most important profession supporting the access to formal care in all the involved countries. In some countries other professionals take over responsibility for the access procedure. Dementia-specific approaches are rarely part of standard care; team-based approaches have differing significances in each of the countries. Informal carers are mainly proactive in seeking formal care. The Nordic countries demonstrate how financial support enhances access to the professional system. Conclusion: Enhanced cooperation between GPs and other professions might optimize access to formal dementia care. Team-based approaches focusing on dementia care should be developed further. Informal carers should be supported and relieved in their role. Financial barriers remain which should be further investigated and reduced.publishersversionpublishe

    Collision geometry scaling of Au+Au pseudorapidity density from sqrt(s_NN) = 19.6 to 200 GeV

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    The centrality dependence of the midrapidity charged particle multiplicity in Au+Au collisions at sqrt(s_NN) = 19.6 and 200 GeV is presented. Within a simple model, the fraction of hard (scaling with number of binary collisions) to soft (scaling with number of participant pairs) interactions is consistent with a value of x = 0.13 +/- 0.01(stat) +/- 0.05(syst) at both energies. The experimental results at both energies, scaled by inelastic p(pbar)+p collision data, agree within systematic errors. The ratio of the data was found not to depend on centrality over the studied range and yields a simple linear scale factor of R_(200/19.6) = 2.03 +/- 0.02(stat) +/- 0.05(syst).Comment: 5 pages, 4 figures, submitted to PRC-R
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