3,049 research outputs found

    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

    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

    Implications of Weak-Interaction Space Deformation for Neutrino Mass Measurements

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    The negative values for the squares of both electron and muon neutrino masses obtained in recent experiments are explained as a possible consequence of a change in metric within the weak-interaction volume in the energy-momentum representation. Using a model inspired by a combination of the general theory of relativity and the theory of deformation for continuous media, it is shown that the negative value of the square of the neutrino mass can be obtained without violating allowed physical limits. The consequence is that the negative value is not necessary unphysical.Comment: 12 pages, 5 figures, LaTe

    On Unitarity Based Relations Between Various Lepton Family Violating Processes

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    Simple "unitarity inspired" relations between two- and three-body lepton flavor violating decays are noted and discussed. In the absence of cancellations, the existing strong bounds on Ό→3e\mu \to 3e and Ό→eγγ \mu\to e\gamma\gamma severly constrain two-body lepton flavor violating decays.Comment: 5 pages, 3 figure

    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

    The Extended Chiral Quark Model confronts QCD

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    We discuss the truncation of low energy effective action of QCD below the chiral symmetry breaking (CSB) scale, including all operators of dimensionality less or equal to 6 which can be built with quark and chiral fields. We perform its bosonization in the scalar, pseudoscalar, vector and axial-vector channels in the large-N_c and leading-log approximation. Constraints on the coefficients of the effective lagrangian are derived from the requirement of Chiral Symmetry Restoration (CSR) at energies above the CSB scale in the scalar-pseudoscalar and vector-axial-vector channels, from matching to QCD at intermediate scales, and by fitting some hadronic observables. In this truncation two types of pseudoscalar states (massless pions and massive Pi'-mesons), as well as a scalar, vector and axial-vector one arise as a consequence of dynamical chiral symmetry breaking. Their masses and coupling constants as well as a number of chiral structural constants are derived. A reasonable fit of all parameters supports a relatively heavy scalar meson (quarkonium) with the mass \sim 1 GeV and a small value of axial pion-quark coupling constant g_A \simeq 0.55.Comment: Talk at QCD99, Montpellier, July 1999, 7 pages, Late

    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

    Orbitally Excited Baryons in Large N_c QCD

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    We present a model-independent analysis of the mass spectrum of nonstrange l=1 baryons in large N_c QCD. The 1/N_c expansion is used to select and order a basis of effective operators that spans the nine observables (seven masses and two mixing angles). Comparison to the data provides support for the validity of the 1/N_c expansion, but also reveals that only a few nontrivial operators are strongly preferred. We show that our results have a consistent interpretation in a constituent quark model with pseudoscalar meson exchange interactions.Comment: 4 pages LaTeX. Invited parallel session talk presented at the XVth Particles and Nuclei International Conference (PANIC99), June 10, 1999, Uppsala, Swede

    CPT- and B-Violation: The p-pbar Sector

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    The CPT symmetry of relativistic quantum field theory requires the total lifetimes of particles and antiparticles be equal. Detection of pbar lifetime shorter than tau_p > O(10^32) yr would signal breakdown of CPT invariance, in combination with B-violation. The best current limit on tau_pbar, inferred from cosmic ray measurements, is about one Myr, placing lower limits on CPT-violating scales that depend on the exact mechanism. Paths to CPT breakdown within and outside ordinary quantum mechanics are sketched. Many of the limiting CPT-violating scales in pbar decay lie within the weak-to-Planck range.Comment: 6 pages, LaTeX, .sty file included; based on contribution to CPT98 Conference; minor changes, accepted by Mod. Phys. Lett.

    The Mediating Roles of Attitude Toward COVID-19 Vaccination, Trust in Science and Trust in Government in the Relationship Between Anti-vaccine Conspiracy Beliefs and Vaccination Intention

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    : Since the outbreak of COVID-19, many conspiracy theories have spread widely, which has the potential to reduce adherence to recommended preventive measures. Specifically, anti-vaccine conspiracy beliefs can have a strong negative impact on COVID-19 vaccination attitude and intention. The present study aimed to clarify how such beliefs can reduce vaccination intention, exploring the possible mediating roles of attitude toward vaccination, trust in science, and trust in government, among a sample of 822 unvaccinated Italian adults (Women = 67.4%; M age = 38.1). Path analysis showed that anti-vaccine conspiracy beliefs influenced intention to get vaccinated both directly and indirectly through the mediating effects of attitude, trust in science, and trust in government. In particular, the simple mediating effect of attitude was the strongest one, followed by the serial mediating effect of trust in science and attitude itself. Findings provide insights into the design of interventions aimed at reducing misinformation and subsequent vaccine hesitancy
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