An update of the ALEPH non-strange spectral functions from hadronic
τ
decays is presented. Compared to the 2005 ALEPH publication, the main improvement is related to the use of a new method to unfold ...the measured mass spectra from detector effects. This procedure also corrects a previous problem in the correlations between the unfolded mass bins. Results from QCD studies and for the evaluation of the hadronic vacuum polarisation contribution to the anomalous muon magnetic moment are derived using the new spectral functions. They are found in agreement with published results based on the previous set of spectral functions.
We present an up-to-date profile of the Cabibbo-Kobayashi-Maskawa matrix with emphasis on the interpretation of recent CP-violation results from the B factories. For this purpose, we review all ...relevant experimental and theoretical inputs from the contributing domains of electroweak interaction. We give the “standard” determination of the apex of the Unitarity Triangle, namely the Wolfenstein parameters \(\overline\rho\) and \(\overline\eta\), by means of a global CKM fit. The fit is dominated by the precision measurement of \(\sin 2 \beta\) by the B factories. A detailed numerical and graphical study of the impact of the results is presented. We propose to include \(\sin 2\alpha\) from the recent measurement of the time-dependent CP-violating asymmetries in \(B^0\to\rho^ + \rho^-\), using isospin relations to discriminate the penguin contribution. The constraint from \(\varepsilon^\prime/\varepsilon\) is discussed. We study the impact from the branching fraction measurement of the rare kaon decay \(K^ + \to\pi^ + \nu\overline\nu\), and give an outlook into the reach of a future measurement of \(K^0_L\to\pi^0\nu\overline\nu\). The B system is investigated in detail. We display the constraint on \(2\beta + \gamma\) and \(\gamma\) from \(B^0\to D^{(*)\pm}\pi^\mp\) and \(B^ + \to D^{(*)0}K^ + \) decays, respectively. A significant part of this paper is dedicated to the understanding of the dynamics of B decays into \(\pi\pi\), \(K\pi\), \(\rho\pi\), \(\rho\rho\) and modes related to these by flavor symmetry. Various phenomenological approaches and theoretical frameworks are discussed. We find a remarkable agreement of the \(\pi\pi\) and \(K\pi\) data with the other constraints in the unitarity plane when the hadronic matrix elements are calculated within QCD Factorization, where we apply a conservative treatment of the theoretical uncertainties. A global fit of QCD Factorization to all \(\pi\pi\) and \(K\pi\) data leads to precise predictions of the related observables. However sizable phenomenological power corrections are preferred. Using an isospin-based phenomenological parameterization, we analyze separately the \(B\to K\pi\) decays, and the impact of electroweak penguins in response to recent discussions. We find that the present data are not sufficiently precise to constrain either electroweak parameters or hadronic amplitude ratios. We do not observe any unambiguous sign of New Physics, whereas there is some evidence for potentially large non-perturbative rescattering effects. Finally we use a model-independent description of a large class of New Physics effects in both \(B^0\overline B^0\) mixing and B decays, namely in the \(b\to d\) and \(b\to s\) gluonic penguin amplitudes, to perform a new numerical analysis. Significant non-standard corrections cannot be excluded yet, however Standard Model solutions are favored in most cases. In the appendix to this paper we propose a frequentist method to extract a confidence level on \(\Delta m_s\) from the experimental information on \(B^0_s \overline B_s^0\) oscillation. In addition we describe a novel approach to combine potentially inconsistent measurements. All results reported in this paper have been obtained with the numerical analysis package CKMfitter, featuring the frequentist statistical approach Rfit.
The determination of αS from τ decays revisited Davier, M.; Descotes-Genon, S.; Höcker, A. ...
The European physical journal. C, Particles and fields,
08/2008, Letnik:
56, Številka:
3
Journal Article
Recenzirano
Odprti dostop
We revisit the determination of
α
S
(
m
τ
2
) using a fit to inclusive
τ
hadronic spectral moments in light of (1) the recent calculation of the fourth-order perturbative coefficient
K
4
in the ...expansion of the Adler function, (2) new precision measurements from BABAR of e
+
e
−
annihilation cross sections, which decrease the uncertainty in the separation of vector and axial-vector spectral functions, and (3) improved results from BABAR and Belle on
τ
branching fractions involving kaons. We estimate that the fourth-order perturbative prediction reduces the theoretical uncertainty, introduced by the truncation of the series, by 20% with respect to earlier determinations. We discuss to some detail the perturbative prediction of two different methods: fixed-order perturbation theory (FOPT) and contour-improved perturbative theory (CIPT). The corresponding theoretical uncertainties are studied at the
τ
and
Z
mass scales. The CIPT method is found to be more stable with respect to the missing higher order contributions and to renormalization scale variations. It is also shown that FOPT suffers from convergence problems along the complex integration contour. Nonperturbative contributions extracted from the most inclusive fit are small, in agreement with earlier determinations. Systematic effects from quark-hadron duality violation are estimated with simple models and found to be within the quoted systematic errors. The fit based on CIPT gives
α
S
(
m
τ
2
)=0.344±0.005±0.007, where the first error is experimental and the second theoretical. After evolution to
M
Z
we obtain
α
S
(
M
Z
2
)=0.1212±0.0005±0.0008±0.0005, where the errors are respectively experimental, theoretical and due to the evolution. The result is in agreement with the corresponding N
3
LO value derived from essentially the
Z
width in the global electroweak fit. The
α
S
(
M
Z
2
) determination from
τ
decays is the most precise one to date.
A new approach to a global fit of the CKM matrix Höcker, A.; Lacker, H.; Laplace, S. ...
The European physical journal. C, Particles and fields,
06/2001, Letnik:
21, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We report on a new approach to a global CKM matrix analysis taking into account most recent experimental and theoretical results. The statistical framework (Rfit) developed in this paper advocates ...frequentist statistics. Other approaches, such as Bayesian statistics or the 95% CL scan method are also discussed. We emphasize the distinction of a model testing and a model dependent, metrological phase in which the various parameters of the theory are estimated. Measurements and theoretical parameters entering the global fit are thoroughly discussed, in particular with respect to their theoretical uncertainties. Graphical results for confidence levels are drawn in various one and two-dimensional parameter spaces. Numerical results are provided for all relevant CKM parameterizations, the CKM elements and theoretical input parameters. Predictions for branching ratios of rare K and B meson decays are obtained. A simple, predictive SUSY extension of the Standard Model is discussed.
Although it is widely recognised that people turn to spirituality in times of crises, the interest in exploring the spiritual needs of cancer patients is just beginning to grow. The purpose of this ...study was to conduct a spiritual needs assessment with cancer patients living in a Northern European metropolitan region in order to (a) examine the relevance and nature of spiritual needs; (b) to clarify the role of demographic and clinical characteristics in spiritual needs; and (c) to identify their associations with dimensions of psychological distress. N = 285 outpatients with mixed cancer sites and of all tumour stages were surveyed cross‐sectionally. Instruments included the Spiritual Needs Questionnaire (SpNQ) and measures of anxiety, distress, hopelessness and meaning‐related life attitudes. Almost all patients (94%) reported at least one spiritual need. The needs for Inner Peace and Actively Giving emerged to be of greatest importance. Significant, but weak differences were found for age, gender and being in a partnership. No associations for medical characteristics were observed. Regression analyses revealed anxiety as the strongest predictor for the subscales Existential Needs, Inner Peace and Actively Giving. The results emphasise the relevance of spiritual needs in cancer patients. The call for spiritual assessment and interventions to meet spiritual needs in cancer patients is strengthened.
The toolkit for multivariate analysis, TMVA, provides a large set of advanced multivariate analysis techniques for signal/background classification. In addition, TMVA now also contains regression ...analysis, all embedded in a framework capable of handling the preprocessing of the data and the evaluation of the output, thus allowing a simple and convenient use of multivariate techniques. The analysis techniques implemented in TMVA can be invoked easily and the direct comparison of their performance allows the user to choose the most appropriate for a particular data analysis. This article gives an overview of the TMVA package and presents recently developed features.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) An update of the ALEPH non-strange spectral functions from hadronic ... decays is presented. Compared to the 2005 ALEPH ...publication, the main improvement is related to the use of a new method to unfold the measured mass spectra from detector effects. This procedure also corrects a previous problem in the correlations between the unfolded mass bins. Results from QCD studies and for the evaluation of the hadronic vacuum polarisation contribution to the anomalous muon magnetic moment are derived using the new spectral functions. They are found in agreement with published results based on the previous set of spectral functions.
Quark mass corrections to the \(\tau\) hadronic width play a significant role only for the strange quark. The complete determination of \(\tau\) decays into strange hadronic final states performed by ...ALEPH allows the extraction of the strange spectral function. New results on strange decay modes from other experiments are also incorporated into the present analysis. Using as input moments of the spectral function the analysis leading to the determination of \(m_s\) is conducted using reasonable theoretical constraints on the nonperturbative components. Careful attention is paid to the treatment of the perturbative expansions of the moments which exhibit convergence problems. The result obtained, \(m_s(M_\tau^2)=(120\pm11_{\rm exp}\pm8_{V_{us}}\pm 19_{\rm th}){\rm MeV} = (120^{ +21}_{ -26}){\rm MeV}\), is stable over the scale from \(M_\tau^2\) down to about 2 GeV\(^2\). Its evolution yields \(m_s(1 {\rm GeV}^2) = (160^{ +28}_{ -35}){\rm MeV}\) and \(m_s(4 {\rm GeV}^2) = (116^{ +20}_{ -25}){\rm MeV} \).
The physics of hadronic tau decays Davier, Michel; Höcker, Andreas; Zhang, Zhiqing
Reviews of modern physics,
10/2006, Letnik:
78, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Hadronic tau decays represent a clean laboratory for the precise study of quantum chromodynamics (QCD). Observables (sum rules) based on the spectral functions of hadronic tau decays can be related ...to QCD quark-level calculations to determine fundamental quantities like the strong coupling constant, parameters of the chiral Lagrangian, |V_us|, the mass of the strange quark, and to simultaneously test the concept of quark-hadron duality. Using the best available measurements and a revisited analysis of the theoretical framework, the value alpha_s(m_tau) = 0.345 +- 0.004exp +- 0.009theo is obtained. Taken together with the determination of alpha_s(m_Z) from the global electroweak fit, this result leads to the most accurate test of asymptotic freedom: the value of the logarithmic slope of 1/alpha_s(s) is found to agree with QCD at a precision of 4%. In another approach, the tau spectral functions can be used to determine hadronic quantities that, due to the nonperturbative nature of long-distance QCD, cannot be computed from first principles. An example for this is the contribution from hadronic vacuum polarization to loop-dominated processes like the anomalous magnetic moment of the muon. This article reviews the measurements of nonstrange and strange tau spectral functions and their phenomenological applications.
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