3,789 research outputs found

    Classifying Reported and "Missing" Resonances According to Their P and C Properties

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    The Hilbert space H^3q of the three quarks with one excited quark is decomposed into Lorentz group representations. It is shown that the quantum numbers of the reported and ``missing'' resonances fall apart and populate distinct representations that differ by their parity or/and charge conjugation properties. In this way, reported and ``missing'' resonances become distinguishable. For example, resonances from the full listing reported by the Particle Data Group are accommodated by Rarita-Schwinger (RS) type representations (k/2,k/2)*[(1/2,0)+(0,1/2)] with k=1,3, and 5, the highest spin states being J=3/2^-, 7/2^+, and 11/2^+, respectively. In contrast to this, most of the ``missing'' resonances fall into the opposite parity RS fields of highest-spins 5/2^-, 5/2^+, and 9/2^+, respectively. Rarita-Schwinger fields with physical resonances as lower-spin components can be treated as a whole without imposing auxiliary conditions on them. Such fields do not suffer the Velo-Zwanziger problem but propagate causally in the presence of electromagnetic fields. The pathologies associated with RS fields arise basically because of the attempt to use them to describe isolated spin-J=k+1/ 2 states, rather than multispin-parity clusters. The positions of the observed RS clusters and their spacing are well explained trough the interplay between the rotational-like (k/2)(k/2 +1)-rule and a Balmer-like -(k+1)^{-2}-behavior

    Predictions for the unitarity triangle angles in a new parametrization

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    A new approach to the parametrization of the CKM matrix, VV, is considered in which VV is written as a linear combination of the unit matrix II and a non-diagonal matrix UU which causes intergenerational-mixing, that is V=cos⁥ΞI+isin⁥ΞUV=\cos\theta I+i\sin\theta U. Such a VV depends on 3 real parameters including the parameter Ξ\theta. It is interesting that a value of Ξ=π/4\theta=\pi/4 is required to fit the available data on the CKM-matrix including CP-violation. Predictions of this fit for the angles α\alpha, ÎČ\beta and Îł\gamma for the unitarity triangle corresponding to V11V13∗+V21V23∗+V31V33∗=0V_{11}V^*_{13} + V_{21} V^*_{23} +V_{31}V^*_{33} =0, are given. For Ξ\theta=π/4\pi/4, we obtain α=88.46∘\alpha=88.46^\circ, ÎČ=45.046∘\beta=45.046^\circ and Îł=46.5∘\gamma=46.5^\circ. These values are just about in agreement, within errors, with the present data. It is very interesting that the unitarity triangle is expected to be approximately a right-angled, isosceles triangle. Our prediction sin⁥2ÎČ=1\sin 2\beta = 1 is in excellent agreement with the value 0.99±0.15±0.050.99\pm 0.15\pm 0.05 reported by the Belle collaboration at the Lepton-Photon 2001 meeting.Comment: 11 pages, latex, no figure

    B Mixing

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    The neutral BB mesons, B0B^0 and BsB_s, can oscillate between their particle and antiparticle states owing to flavor-changing weak interactions. In recent years, techniques to detect these oscillations as a function of the meson's decay time have been developed. In this article the physics of flavor oscillations is reviewed and theoretical predictions are summarized. The many observations that demonstrate the time-dependence of B^0-\B0bar oscillations are presented along with a combined measurement of its frequency, Ύmd\delta m_d. The attempts to measure the BsB_s oscillation frequency, both directly and indirectly, are then summarized. Finally, values for the CKM elements ∣Vtd∣|V_{td}| and ∣Vts/Vtd∣|V_{ts}/V_{td}| are extracted

    Correcting the Minimization Bias in Searches for Small Signals

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    We discuss a method for correcting the bias in the limits for small signals if those limits were found based on cuts that were chosen by minimizing a criterion such as sensitivity. Such a bias is commonly present when a "minimization" and an "evaluation" are done at the same time. We propose to use a variant of the bootstrap to adjust the limits. A Monte Carlo study shows that these new limits have correct coverage.Comment: 14 pages, 5 figue

    Semileptonic and rare B meson decays into a light pseudoscalar meson

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    In the framework of a QCD relativistic potential model we evaluate the form factors describing the exclusive decays B => \pi l nu and B => K l+ l-. The present calculation extends a previous analysis of B meson decays into light vector mesons. We find results in agreement with the data, when available, and with the theoretical constraints imposed by the Callan-Treiman relation and the infinite heavy quark mass limit.Comment: 11 pages LaTeX + 2 figure

    A priori mixing of mesons and the |Delta I|=1/2 rule in K\to\pi\pi

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    We consider the hypothesis of a priori mixings in the mass eigenstates of mesons to obtain the |Delta I|=1/2 rule in K\to\pi\pi. The Hamiltonian responsible for the transition is the strong interacting one. The experimental data are described using the isospin symmetry relations between the strong coupling constants

    Glueball Spin

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    The spin of a glueball is usually taken as coming from the spin (and possibly the orbital angular momentum) of its constituent gluons. In light of the difficulties in accounting for the spin of the proton from its constituent quarks, the spin of glueballs is reexamined. The starting point is the fundamental QCD field angular momentum operator written in terms of the chromoelectric and chromomagnetic fields. First, we look at the restrictions placed on the structure of glueballs from the requirement that the QCD field angular momentum operator should satisfy the standard commutation relationships. This can be compared to the electromagnetic charge/monopole system, where the quantization of the field angular momentum places restrictions (i.e. the Dirac condition) on the system. Second, we look at the expectation value of this operator under some simplifying assumptions.Comment: 11 pages, 0 figures; added references and some discussio

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    ΔπN\Delta\pi N coupling constant in light cone QCD sum rules

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    We employ the light cone QCD sum rules to calculate ΔπN\Delta\pi N coupling constant by studying the two point correlation function between the vacuum and the pion state. Our result is consistent with the traditional QCD sum rules calculations and it is in agreement with the experimental value.Comment: 8 pages, latex, 2 figure

    Correlational study and randomised controlled trial for understanding and changing red meat consumption: The role of eating identities

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    Rationale: The present studies aimed to contribute to the literature on psychological variables involved in reducing red meat consumption (RMC). Objective: Study 1 investigated whether the theory of planned behaviour (TPB), plus healthy-eating and meat-eating identities, could explain intentions to reduce RMC. Study 2 evaluated the effectiveness of an SMS text message intervention on self-monitoring to reduce RMC. Methods: In Study 1, data were collected daily using online food diaries for one week and a TPB questionnaire. Study 2 was a randomised controlled trial assessing pre– and post–RMC and TPB constructs by online food diaries and questionnaires over a one-week period. Participants were Italian undergraduates in each study (Study 1: N = 405; Study 2: N = 244). In Study 2, participants were randomly allocated to control and message condition groups. Participants in the message condition group received a daily SMS, which reminded them to monitor RMC, while participants in the control group did not receive any message. Only students who completed all measures were considered in the analyses (Study 1: N = 342; Study 2: N = 228). Results: Study 1 showed that affective and instrumental attitudes, perceived behavioural control, and meat-eating identity explained intentions to reduce RMC, while subjective norm, past behaviour, and healthy-eating identity did not. Study 2 showed that an SMS intervention was effective in increasing intentions and reducing RMC. Mediation analyses indicated partial serial mediation through healthy-eating and meat-eating identities and intentions. Conclusion: The present studies provide support for the predictive validity of TPB in explaining intentions to reduce RMC and for the efficacy of an SMS intervention targeting self-monitoring in reducing RMC. Findings confirmed the important role of eating identities in explaining intentions to reduce RMC and in changing this behaviour
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