4,049 research outputs found

    B -> X_u l nu decay distributions to order alpha_s

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    An analytic result for the O(alpha_s corrections to the triple differential B -> X_u l nu decay rate is presented, to leading order in the heavy-quark expansion. This is relevant for computing partially integrated decay distributions with arbitrary cuts on kinematic variables. Several double and single differential distributions are derived, most of which generalize known results. In particular, an analytic result for the O(alpha_s) corrections to the hadronic invariant mass spectrum is presented. The effects of Fermi motion, which are important for the description of decay spectra close to infrared sensitive regions, are included. The behaviour of perturbation theory in the region of time-like momenta is also investigatedComment: 24 pages, 11 figures, 1 typo in eq.(5.4) corrected; version published in JHEP06(1999)01

    Radiative ϕ\phi-meson decays and η\eta-η\eta^\prime mixing: a QCD sum rule analysis

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    The radiative transitions ϕηγ\phi \to \eta \gamma and ϕηγ\phi \to \eta^\prime \gamma are analysed using QCD sum-rules. The results we obtain for B(ϕηγ)=(1.15±0.2)102{\cal B}(\phi \to \eta \gamma)=(1.15 \pm 0.2) 10^{-2} and B(ϕηγ)=(1.18±0.4)104{\cal B}(\phi \to \eta^\prime \gamma)=(1.18 \pm 0.4) 10^{-4} are in very good agreement with existing experimental data. The related issue of ηη\eta-\eta^\prime mixing is discussed and we give predictions for the η\eta and η\eta^\prime decay constants in the framework of a mixing scheme in the quark-flavour basis.Comment: Latex, 15 pages, 3figures. Some typos correcte

    Effects of Errors of Commission on Student Performance During Discrete Trial Tasks

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    The extent to which interventions are implemented as intended is called treatment integrity (TI). Given that it is unreasonable to expect 100% TI in applied settings, a through understand of TI is essential to appropriately train teachers. This understanding must include the types of TI errors that may be committed and how these effect student learning. It is essential to study TI errors because of the real-world implications for students, including eligibility decisions for special education services, which are based upon students’ responses to inventions. It is not possible to make educational decisions on intervention effectiveness unless it is clear that evidence-based practices have been implemented accurately. If TI is low, it is impossible to determine which services and interventions a student requires. Further, measuring the fidelity with which interventions are applied allows for a more thorough and accurate understanding of which components of an intervention are effective, necessary, and feasible. A broader understanding of which TI errors are most significant, as well as measuring the necessary levels of TI, will lead to more accurate information about how to implement evidence-based practices. The purpose of this study is to gain a more nuanced understanding of TI failures in the form of errors of commission and the role commission errors have on participant responsiveness (Power, 2005). This study extends the results of DiGennaro Reed et al. (2011) by including an intermediate (80%) level of TI which may more accurately represent an attainable level of TI in applied settings. For two of four students, more errors of commission were related to lower skill acquisition. For the other two students, idiosyncratic patterns of responding emerged

    Identifying DsJ(2700)D_{sJ}(2700) through its decay modes

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    We study how to assign the recently observed DsJ(2700)D_{sJ}(2700) meson to an appropriate level of the csˉc \bar s spectrum by the analysis of its decay modes in final states comprising a light pseudoscalar meson. We use an effective lagrangian approach with heavy quark and chiral symmetries, obtaining that the measurement of the DKD^* K decay width would allow to distinguish between two possible assignments.Comment: RevTex, 6 pages - references adde

    Microstructure and chemical composition of Roman orichalcum coins emitted after the monetary reform of Augustus (23 B.C.)

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    A collection of ancient Roman orichalcum coins, i.e., a copper-zinc alloy, minted under the reigns from Caesar to Domitianus, have been characterised using scanning electron microscopy (SEM-EDS) and electron microprobe analysis (EMPA). We studied, for the first time, coins emitted by Romans after the reforms of Augustus (23 B.C.) and Nero (63-64 A.D). These coins, consisting of asses, sestertii, dupondii and semisses, were analysed using non- and invasive analyses, aiming to explore microstructure, corrosive process and to acquire quantitative chemical analysis. The results revealed that the coins are characterized by porous external layers, which are affected by dezincification and decuprification processes. As pictured by the X-ray maps, the elemental distribution of Cu and Zn shows patterns of depletion that in some cases penetrate in deep up to 1 mm. The composition of the un-corroded nucleus is a Cu-Zn alloy containing up to 30% of Zn, typical of coins produced via cementation process

    Radiative transitions of DsJ(2317)D^*_{sJ}(2317) and DsJ(2460)D_{sJ}(2460)

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    We study radiative decays of DsJ(2317)D^*_{sJ}(2317) and DsJ(2460)D_{sJ}(2460) using light-cone QCD sum rules. In particular, we consider the decay modes DsJ(2317)DsγD^*_{sJ}(2317)\to D_s^* \gamma and DsJ(2460)Ds()γ,DsJ(2317)γD_{sJ}(2460)\to D_s^{(*)} \gamma, D^*_{sJ}(2317) \gamma and evaluate the hadronic parameters in the transition amplitudes analyzing correlation functions of scalar, pseudoscalar, vector and axial-vector quark currents. In the case of DsJ(2317)DsγD^*_{sJ}(2317)\to D_s^* \gamma we also consider determinations based on two different correlation functions in HQET. The decay widths turn out to be different than previous estimates obtained by other methods; the results favour the interpretation of DsJ(2317)D^*_{sJ}(2317) and DsJ(2460)D_{sJ}(2460) as ordinary cˉs\bar c s mesons.Comment: RevTex, 23 pages, 9 eps figure

    Semileptonic and Rare BB-meson transitions in a QCD relativistic potential model

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    Using a QCD relativistic potential model, previously applied to the calculation of the heavy meson leptonic constants, we evaluate the form factors governing the exclusive decays BρνB\to\rho\ell\nu, BKγB\to K^*\gamma and BK+B\to K^*\ell^+\ell^-. In our approach the heavy meson is described as a QqˉQ\bar q bound state, whose wave function is solution of the relativistic Salpeter equation, with an instantaneous potential displaying Coulombic behaviour at small distances and linear behaviour at large distances. The light vector meson is described by using a vector current interpolating field, according to the Vector Meson Dominance assumption. A Pauli-Villars regularized propagator is assumed for the quarks not constituting the heavy meson. Our procedure allows to avoid the description of the light meson in terms of wave function and constituent quarks, and consequently the problem of boosting the light meson wave function. Assuming as an input the experimental results on BKγB\to K^*\gamma, we evaluate all the form factors describing the Bρ,KB\to \rho, K^* semileptonic and rare transitions. The overall comparison with the data, whenever available, is satisfactory.Comment: Latex, 19 pages, 3 figure

    Th.o.m.a.s.: An exploratory assessment of Theory of Mind in schizophrenic subjects

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    A large body of literature agrees that persons with schizophrenia suffer from a Theory of Mind (ToM) deficit. However, most empirical studies have focused on third-person, egocentric ToM, underestimating other facets of this complex cognitive skill. Aim of this research is to examine the ToM of schizophrenic persons considering its various aspects (first vs. second order, first vs. third person, egocentric vs. allocentric, beliefs vs. desires vs. positive emotions vs. negative emotions and how each of these mental state types may be dealt with), to determine whether some components are more impaired than others. We developed a Theory of Mind Assessment Scale (Th.o.m.a.s.) and administered it to 22 persons with a DSM-IV diagnosis of schizophrenia and a matching control group. Th.o.m.a.s. is a semi-structured interview which allows a multi-component measurement of ToM. Both groups were also administered a few existing ToM tasks and the schizophrenic subjects were administered the Positive and Negative Symptoms Scale and the WAIS-R. The schizophrenic persons performed worse than control at all the ToM measurements; however, these deficits appeared to be differently distributed among different components of ToM. Our conclusion is that ToM deficits are not unitary in schizophrenia, which also testifies to the importance of a complete and articulated investigation of ToM
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