1,139 research outputs found

    Ecosystem-based Management for Protected Species in the North Pacific Fisheries

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    In the North Pacific Ocean, an ecosystem-based fishery management approach has been adopted. A significant objective of this approach is to reduce interactions between fishery-related activities and protected species. We review management measures developed by the North Pacific Fishery Management Council and the National Marine Fisheries Service to reduce effects of the groundfish fisheries off Alaska on marine mammals and seabirds, while continuing to provide economic opportunities for fishery participants. Direct measures have been taken to mitigate known fishery impacts, and precautionary measures have been taken for species with potential (but no documented) interactions with the groundfish fisheries. Area closures limit disturbance to marine mammals at rookeries and haulouts, protect sensitive benthic habitat, and reduce potential competition for prey resources. Temporal and spatial dispersion of catches reduce the localized impact of fishery removals. Seabird avoidance measures have been implemented through collaboration with fishery participants and have been highly successful in reducing seabird bycatch. Finally, a comprehensive observer monitoring program provides data on the location and extent of bycatch of marine mammals and seabirds. These measures provide managers with the flexibility to adapt to changes in the status of protected species and evolving conditions in the fisheries. This review should be useful to fishery managers as an example of an ecosystem-based approach to protected species management that is adaptive and accounts for multiple objectives

    On the Determination of a1a_1 and a2a_2 from Hadronic Two Body BB Decays

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    {}From Class I decays : B^o \ra \pi^+ ( \rho^+ ) + D^- ( {D^*}^- ), we determine a1a_1, and from Class III decays : B^+ \ra \pi^+ ( \rho^+ ) + \ol{D}^o ( {\ol{D}^*}^o ), we determine an allowed domain in the (a1,a2)( a_1, a_2 ) plane. We find that within one standard deviation errors, the allowed band of a1a_1 from Class I decays is at least three standard deviations removed from the allowed domain (a1,a2)( a_1, a_2 ) from Class III decays.If we expand the experimental errors to two standard deviations we do find a small intersection between the a1a_1 band and the allowed (a1,a2)( a_1, a_2 ) domain. The results usually quoted in the literature lie in this intersection. We suggest : (1) an independent measurement of the branching ratio for the Class III decay, B^+ \ra \rho^+ \ol{D}^o , (2) a high-statistics measurement of the branching ratio of the Class I decay, B \ra \ol{D} ( \ol{D}^* ) + D_s ( D_s^* ) in both charged states, and (3) a measurement of the longitudinal polarization fraction in the Class III decay B^+ \ra \rho^+ {\ol{D}^*}^o to shed more light on the questions involved .Comment: 9pages(Latex)+4 figures(PS file appended), PAR/LPTHE/94-2

    Implications of factorization for the determination of hadronic form factors in D_s^+ \ra \phi transition

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    Using factorization we determine the allowed domains of the ratios of form factors, x=A2(0)/A1(0)x = A_2(0)/A_1(0) and y=V(0)/A1(0)y = V(0)/A_1(0), from the experimentally measured ratio R_h \equiv \Gamma(D_s^+ \ra \phi \rho^+)/\Gamma(D_s^+ \ra \phi \pi^+) assuming three different scenarios for the q2q^2-dependence of the form factors. We find that the allowed domains overlap with those obtained by using the experimentally measured ratio R_{s\ell} = \Gamma(D^+_s \ra \phi \ell^+ \nu_{\ell})/\Gamma(D^+_s \ra \phi \pi^+) provided that the phenomenological parameter a1a_1 is 1.231.23. Such a comparison presents a genuine test of factorization. We calculate the longitudinal polarization fraction, \Gamma_L/\Gamma \equiv \Gamma(D_s^+ \ra \phi_L \rho^+_L)/\Gamma(D_s^+ \ra \phi \rho^+), in the three scenarios for the q2q^2-dependence of the form factors and emphasize the importance of measuring ΓL/Γ\Gamma_L/\Gamma . Finally we discuss the q2q^2-distribution of the semileptonic decay and find that it is rather insensitive to the scenarios for the q2q^2-dependence of the form factors, and unless very accurate data can be obtained it is unlikely to discriminate between the different scenarios. Useful information on the value of xx might be obtained by the magnitude of the q2q^2-distribution near q2=0q^2 = 0. However the most precise information on xx and yy would come from the knowledge of the longitudinal and left-right transverse polarizations of the final vector mesons in hadronic and/or semileptonic decays.Comment: Latex 10 pages( 4 figures), PAR/LPTHE/94-3

    Radiative Leptonic Decays of Heavy Mesons

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    We compute the photon spectrum and the rate for the decays B(D)lνlγB(D)\to l\nu_l\gamma These photonic modes constitute a potentially large background for the purely leptonic decays which are used to extract the heavy meson decay constants. While the rate for D\to l\n\g is small, the radiative decay in the BB meson case could be of comparable magnitude or even larger than B\to\m\n. This would affect the determination of fBf_B if the τ\tau channel cannot be identified. We obtain theoretical estimates for the photonic rates and disscuss their possible experimental implications.Comment: 12 pages, RevTex, 3 uuencoded figures include

    Nonfactorization and the decays Ds+ϕπ+,ϕρ+D_s^+ \to \phi \pi^+, \phi \rho^+ and ϕl+νl\phi l^+ \nu_l

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    In six chosen scenarios for the q2q^2 dependence of the form factors involved in Ds+ϕD_s^+ \rightarrow \phi transition, we have determined the allowed domain of x=A2(0)/A1(0)x = A_2(0) / A_1(0) and y=V(0)/A1(0)y = V(0)/A_1(0) from the experimentally measured ratios Rsl=Γ(Ds+ϕl+νl)/Γ(Ds+ϕπ+)R_{sl} = \Gamma(D_s^+ \rightarrow \phi l^+ \nu_l)/\Gamma(D_s^+ \rightarrow \phi \pi^+) and Rh=Γ(Ds+ϕρ+)/Γ(Ds+ϕπ+)R_h = \Gamma(D_s^+ \rightarrow \phi \rho^+)/\Gamma(D_s^+ \rightarrow \phi \pi^+) in a scheme that uses the Nc=3N_c =3 value of the phenomenological parameter a1a_1 and includes nonfactorized contribution. We find that the experimentally measured values of xx and yy from semileptonic decays of Ds+D_s^+ favor solutions which have significant nonfactorized contribution, and, in particular, RslR_{sl} favors solutions in scenarios where A1(q2)A_1(q^2) is either flat or decreasing with q2q^2.Comment: 15 pages, Latex, four figure (available on request)

    Ds+ϕρ+D_s^+ \to \phi \rho^+ Decay

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    Motivated by the experimental measurement of the decay rate, Γ\Gamma, and the longitudinal polarization, PLP_L, in the Cabibbo favored decay Ds+ϕρ+D_s^+\to \phi {\rho}^{+}, we have studied theoretical prediction within the context of factorization approximation invoking several form factors models. We were able to obtain agreement with experiment for both Γ\Gamma and PLP_L by using experimentally measured values of the form factors A1Dsϕ(0)A_1^{D_s\phi}(0), A2Dsϕ(0)A_2^{D_s\phi}(0) and VDsϕ(0)V^{D_s\phi}(0) in the semi-leptonic decay Ds+ϕl+νlD_s^+\to \phi l^{+}\nu_{l}. We have also included in our calculation the effect of the final state interaction (fsifsi) by working with the partial waves amplitudes SS, PP and DD. Numerical calculation shows that the decay amplitude is dominated by SS wave, and that the polarization is sensitive to the interference between SS and DD waves. The range of the phase difference δSD=δSδD\delta_{SD} = \delta_S - \delta_D accommodated by experimental error in PLP_L is large.Comment: 7 pages, LaTe

    Critical Analysis of Theoretical Estimates for BB to Light Meson Form Factors and the BψK(K)B \to \psi K(K^{\ast}) Data

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    We point out that current estimates of form factors fail to explain the non-leptonic decays BψK(K)B \to \psi K(K^{\ast}) and that the combination of data on the semi-leptonic decays DK(K)νD \to K(K^{\ast})\ell \nu and on the non-leptonic decays BψK(K)B \to \psi K(K^{\ast}) (in particular recent po\-la\-ri\-za\-tion data) severely constrain the form (normalization and q2q^2 dependence) of the heavy-to-light meson form factors, if we assume the factorization hypothesis for the latter. From a simultaneous fit to \bpsi and \dk data we find that strict heavy quark limit scaling laws do not hold when going from DD to BB and must have large corrections that make softer the dependence on the masses. We find that A1(q2)A_1(q^2) should increase slower with \qq than A2,V,f+A_2, V, f_+. We propose a simple parametrization of these corrections based on a quark model or on an extension of the \hhs laws to the \hl case, complemented with an approximately constant A1(q2)A_1(q^2). We analyze in the light of these data and theoretical input various theoretical approaches (lattice calculations, QCD sum rules, quark models) and point out the origin of the difficulties encountered by most of these schemes. In particular we check the compatibility of several quark models with the heavy quark scaling relations.Comment: 48 pages, DAPNIA/SPP/94-24, LPTHE-Orsay 94/1
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