6,403 research outputs found
Constraints on the parameters of the CKM matrix by End 1998
A review of the current status of the Cabibbo-Kobayashi-Maskawa matrix (CKM)
is presented. This paper is an update of the results published in [1]. The
experimental constraints imposed by the measurements of \epsilon_K,
V_{ub}/V_{cb}, \Delta m_d and from the limit on \Delta m_d are used. Values of
the constraints and of the parameters entering into the constraints, which
restrict the range of the \bar{\rho} and \bar{\eta} parameters, include recent
measurements presented at 1998 Summer Conferences and progress obtained by
lattice QCD collaborations. The results are: \bar{\rho}=0.202
^{+0.053}_{-0.059},\bar{\eta}=0.340 \pm 0.035, from which the angles \alpha,
\beta and \gamma of the unitarity triangle are inferred : \sin 2 \alpha = -0.26
^{+ 0.29}_{-0.28} ,\sin 2 \beta = 0.725 ^{+0.050}_{-0.060} ,\gamma=
(59.5^{+8.5}_{-7.5})^{\circ}. Without using the constraint from \epsilon_K,
\sin 2 \beta has been obtained: \sin 2 \beta = 0.72 ^{+0.07}_{-0.11}. Several
external measurements or theoretical inputs have been removed, in turn, from
the constraints and their respective probability density functions have been
obtained. Central values and uncertainties on these quantities have been
compared with actual measurements or theoretical evaluations. In this way it is
possible to quantify the importance of the different measurements and the
coherence of the Standard Model scenario for CP violation. An important result
is that \Delta m_s is expected to be between [12.0-17.6] ps^{-1} with 68% C.L.
and <20 ps^{-1} at 95% C.L. Finally relations between the CKM parameters and
the quark masses are examined within a given model.Comment: 26 page
Unitarity Triangle Analysis in the Standard Model and Sensitivity to New Physics
By using the most recent determinations of the several theoretical and
experimental input parameters, we update the Unitarity Triangle analysis in the
Standard Model and discuss the sensitivity to New Physics effects. We
investigate the interest of measuring with a better precision the various
physical quantities entering the Unitarity Triangle analysis and study in a
model independent way whether, despite the undoubted success of the CKM
mechanism in the Standard Model, the Unitarity Triangle analysis still allows
the presence of New Physics.Comment: Invited talk at the Workshop on the CKM Unitarity Triangle, IPPP
Durham, April 2003 (eConf C0304052). 9 pages LaTeX, 15 eps figures. Misprint
corrected and references adde
Dealing with uncertainty: turbulent parameterizations and grid-spacing effects in numerical modelling of deep moist convective processes
Abstract. Computer power has grown to the point that very-fine-mesh mesoscale modelling is now possible. Going down through scales is clumsily supposed to reduce uncertainty and to improve the predictive ability of the models. This work provides a contribution to understand how the uncertainty in the numerical weather prediction (NWP) of severe weather events is affected by increasing the model grid resolution and by choosing a parameterization which is able to represent turbulent processes at such finer scales. A deep moist convective scenario, a supercell, in a simplified atmospheric setting is studied by mean of high resolution numerical simulations with COSMO-Model. Different turbulent closures are used and their impacts on the space-time properties of convective fields are discussed. The convective-resolving solutions adopting Large Eddy Simulation (LES) turbulent closure converge with respect to the overall flow field structure when grid spacing is properly reduced. By comparing the rainfall fields produced by the model on larger scales with those at the convergence scales it's possible to size up the uncertainty introduced by the modelling itself on the predicted ground effects in such simplified scenario
Constraints on the parameters of the matrix at the end of 1997
A review of the current status of the Cabibbo-Kobayashi-Maskawa matrix V_CKM
is presented. This paper contains an update of the results published in
hep-ph/9711261. Values of the parameters entering into the constraints, which
restrict the range for rho and eta parameters, include recent measurements
given at 1997 Summer Conferences and progress obtained by lattice QCD
collaborations.Experimental constraints imposed by the measurements of
epsilon_k,V_ub/V_cb, Delta m_d and by the limit on Delta m_s, are compatible
and do not show evidence for New Physics inside measurements errors. Values for
the angles alpha, beta and gamma of the C.K.M. triangle have been also
obtained: rho=0.156 +- 0.090, eta=0.328 +- 0.054 sin 2alpha = -0.10+-0.40, sin
2beta = 0.68 +- 0.10, gamma= 64+-12 Angles theta,theta_u,theta_d and phi
proposed in the parametrisation (Phys. Lett. B5353 (1995) 114.) of the C.K.M.
matrix have been also determined. Finally, as there are more constraints than
the fitted rho and eta parameters, several external measurements or theoretical
inputs have been removed, in turn, from the constraints and their respective
values have been fitted simultaneously with rho and eta.Central values and
uncertainties on these quantities have been compared with actual measurements
or theoretical evaluations. In this way it is possible to quantify the
importance of the different measurements and the coherence of the Standard
Model scenario for CP violation.Comment: 29 page
Commentary on: "Pityriasis Rosea Recurrence is Much Higher than Previously Known: A Prospective Study".
Abstract is missing (Correspondence
Determination of the CKM unitarity triangle parameters by end 1999
Within the Standard Model, a review of the current determination of the CKM
unitarity triangle parameters is presented, using experimental constraints from
the measurements of |epsilon_K|, V_ub/V_cb, Delta m_d and from the limit on
Delta m_s, available by end 1999.Comment: Talk given by A. Stocchi at the Third International Conference on B
physics and CP violation, National Taiwan Univ., Taipei, Tawain, December
3-7, 199
2000 CKM-Triangle Analysis A Critical Review with Updated Experimental Inputs and Theoretical Parameters
Within the Standard Model, a review of the current determination of the sides
and angles of the CKM unitarity triangle is presented, using experimental
constraints from the measurements of |\epsilon_K|, |V_{ub}/V_{cb}|, \Delta m_d
and from the limit on \Delta m_s, available in September 2000. Results from the
experimental search for {B}^0_s-\bar{B}^0_s oscillations are introduced in the
present analysis using the likelihood. Special attention is devoted to the
determination of the theoretical uncertainties. The purpose of the analysis is
to infer regions where the parameters of interest lie with given probabilities.
The BaBar "95 %, C.L. scanning" method is also commented.Comment: 44 pages (revised version
Assessing uncertainty in radar measurements on simplified meteorological scenarios
A three-dimensional radar simulator model (RSM) developed by Haase (1998) is coupled with the nonhydrostatic mesoscale weather forecast model Lokal-Modell (LM). The radar simulator is able to model reflectivity measurements by using the following meteorological fields, generated by Lokal Modell, as inputs: temperature, pressure, water vapour content, cloud water content, cloud ice content, rain sedimentation flux and snow sedimentation flux. This work focuses on the assessment of some uncertainty sources associated with radar measurements: </p><ol> <li>absorption by the atmospheric gases, e.g., molecular oxygen, water vapour, and nitrogen; </li> <li>attenuation due to the presence of a highly reflecting structure between the radar and a "target structure". </li> </ol> RSM results for a simplified meteorological scenario, consisting of a humid updraft on a flat surface and four cells placed around it, are presented
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