684 research outputs found

    The DNDN, πΣc\pi \Sigma_c interaction in finite volume and the Λc(2595)\Lambda_c(2595) resonance

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    In this work the interaction of the coupled channels DNDN and πΣc\pi \Sigma_c in an SU(4) extrapolation of the chiral unitary theory, where the Λc(2595)\Lambda_c(2595) resonance appears as dynamically generated from that interaction, is extended to produce results in finite volume. Energy levels in the finite box are evaluated and, assuming that they would correspond to lattice results, the inverse problem of determining the phase shifts in the infinite volume from the lattice results is solved. We observe that it is possible to obtain accurate πΣc\pi \Sigma_c phase shifts and the position of the Λc(2595)\Lambda_c(2595) resonance, but it requires the explicit consideration of the two coupled channels. We also observe that some of the energy levels in the box are attached to the closed DNDN channel, such that their use to induce the πΣc\pi \Sigma_c phase shifts via L\"uscher's formula leads to incorrect results.Comment: 10 pages, 13 figures, accepted for publication in Eur. Phys. J.

    Magnetic moments of the low-lying JP=1/2J^P=\,1/2^-, 3/23/2^- Λ\Lambda resonances within the framework of the chiral quark model

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    The magnetic moments of the low-lying spin-parity JP=J^P= 1/21/2^-, 3/23/2^- Λ\Lambda resonances, like, for example, Λ(1405)\Lambda(1405) 1/21/2^-, Λ(1520)\Lambda(1520) 3/23/2^-, as well as their transition magnetic moments, are calculated using the chiral quark model. The results found are compared with those obtained from the nonrelativistic quark model and those of unitary chiral theories, where some of these states are generated through the dynamics of two hadron coupled channels and their unitarization

    Photo- and Electron-Production of Mesons on Nucleons and Nuclei

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    In these lectures I will show some results obtained with the chiral unitary approach applied to the photo and electroproduction of mesons. The results for photoproduction of ηπ0p\eta \pi^0 p and K0π0Σ+K^0 \pi^0 \Sigma^+, together with related reactions will be shown, having with common denominator the excitation of the Δ(1700)\Delta(1700) resonance which is one of those dynamically generated in the chiral unitary approach. Then I will show results obtained for the e+eϕf0(980)e^+ e^- \to \phi f_0(980) reaction which reproduce the bulk of the data except for a pronounced peak, giving support to a new mesonic resonance, X(2175). Results will also be shown for the electromagnetic form factors of the N(1535)N^*(1535) resonance, also dynamically generated in this approach. Finally, I will show some results on the photoproduction of the ω\omega in nuclei, showing that present experimental results claiming a shift of the ω\omega mass in the medium are tied to a particular choice of background and are not conclusive. One the other hand, the same experimental results show unambiguously a huge increase of the ω\omega width in the nuclear medium.Comment: Lecture at the "International School of Nuclear Physics", 29th Course Quarks in Hadrons and Nuclei, Erice, Italy, September 2007. Note added in Proofs concerning the mixed events technique and other comments on omega productio

    Meeting Report: Hackathon-Workshop on Darwin Core and MIxS Standards Alignment

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    The Global Biodiversity Information Facility and the Genomic Standards Consortium convened a joint workshop at the University of Oxford, 27–29 February 2012, with a small group of experts from Europe, USA, China and Japan, to continue the alignment of the Darwin Core with the MIxS and related genomics standards. Several reference mappings were produced as well as test expressions of MIxS in RDF. The use and management of controlled vocabulary terms was considered in relation to both GBIF and the GSC, and tools for working with terms were reviewed. Extensions for publishing genomic biodiversity data to the GBIF network via a Darwin Core Archive were prototyped and work begun on preparing translations of the Darwin Core to Japanese and Chinese. Five genomic repositories were identified for engagement to begin the process of testing the publishing of genomic data to the GBIF network commencing with the SILVA rRNA database

    Dynamically generated resonances

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    In this talk I report on recent work related to the dynamical generation of baryonic resonances, some made up from pseudoscalar meson-baryon, others from vector meson-baryon and a third type from two meson-one baryon systems. We can establish a correspondence with known baryonic resonances, reinforcing conclusions previously drawn and bringing new light on the nature of some baryonic resonances of higher mass.Comment: Talk given at the Workshop on physics of the excited nucleon-NSTAR 2009, Beijing, april 200

    The pd --> ^3He eta pi0 reaction at T_p = 1450 MeV

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    The cross section for the pd --> ^3He eta pi0 reaction has been measured at a beam energy of 1450 MeV using the WASA detector at the CELSIUS storage ring and detecting one ^3He and four photons from the decays of the two photons. The data indicate that the production mechanism involves the formation of the Delta(1232) isobar. Although the beam energy does not allow the full peak of this resonance to be seen, the invariant masses of all three pairs of final state particles are well reproduced by a phase space Monte Carlo simulation weighted with the p-wave factor of the square of the pi^0 momentum in the ^3Hepi^0 system.Comment: 10 pages, 5 figure

    Quantum Histories and Quantum Gravity

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    This paper reviews the histories approach to quantum mechanics. This discussion is then applied to theories of quantum gravity. It is argued that some of the quantum histories must approximate (in a suitable sense) to classical histories, if the correct classical regime is to be recovered. This observation has significance for the formulation of new theories (such as quantum gravity theories) as it puts a constraint on the kinematics, if the quantum/classical correspondence principle is to be preserved. Consequences for quantum gravity, particularly for Lorentz symmetry and the idea of "emergent geometry", are discussed.Comment: 35 pages (29 pages main body), two figure
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