oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2020 ( 5 )

2019 ( 406 )

2018 ( 520 )

2017 ( 535 )

Custom range...

Search Results: 1 - 10 of 325443 matches for " S. Bertolini "
All listed articles are free for downloading (OA Articles)
Page 1 /325443
Display every page Item
A New Estimate of $\varepsilon '/\varepsilon$
S. Bertolini
Physics , 1996,
Abstract: We discuss a new estimate of $\varepsilon '/\varepsilon$ in the kaon system. The present approach is based on the evaluation of the hadronic matrix elements of the \mbox{$\Delta S =1$} effective quark lagrangian by means of the chiral quark model, with the inclusion of meson one-loop renormalization and NLO Wilson coefficients. The estimate here reviewed is fully consistent with the $\Delta I =1/2$ selection rule in $K\to \pi\pi$ decays, which is well reproduced within the same framework.
Estimating epsilon'/epsilon in the Standard Model
S. Bertolini
Physics , 1999,
Abstract: I discuss the comparison of the current theoretical calculations of epsilon'/epsilon with the experimental data. Lacking reliable ``first principle'' calculations, phenomenological approaches may help in understanding correlations among different contributions and available experimental data. In particular, in the chiral quark model approach the same dynamics which underlies the Delta I = 1/2 selection rule in kaon decays appears to enhance the K -> pi pi matrix element of the Q_6 gluonic penguin, thus driving epsilon'/epsilon in the range of the recent experimental measurements.
On soft breaking and CP phases in the supersymmetric standard model
S. Bertolini,F. Vissani
Physics , 1993, DOI: 10.1016/0370-2693(94)90403-0
Abstract: We consider a class of N=1 supersymmetric extensions of the Standard Model in which the soft breaking sector is CP conserving at the GUT scale. We study the question of whether the presence of explicit CP violation in the Yukawa sector of the theory induces through renormalization effects CP violating phases in the soft terms, which could lead to observable effects. A clear pattern appears in the structure of phases in the soft sector. In particular, the inclusion of intergenerational mixing induces large phases in the flavour mixing entries of the trilinear soft breaking terms, whereas the diagonal entries remain real. A mechanism is proposed for generating through chargino exchange a contribution to the neutron electric dipole moment which can be a few orders of magnitude larger that that of the Standard Model, although still out of reach of experimental tests. We comment on the possible relevance of these phases for baryogenesis at the weak scale in minimal supersymetric scenarios, recently considered in the literature.
The $b\to sγγ$ transition in softly broken supersymmetry
S. Bertolini,J. Matias
Physics , 1997, DOI: 10.1103/PhysRevD.57.4197
Abstract: We study the effect of supersymmetric contributions to the effective quark transition $b\to s\gamma\gamma$, including leading order QCD effects. We apply the discussion to the decay $B_s\to\gamma\gamma$. Even though one-particle irreducible contributions could play a role, numerical cancelations make the amplitude for the two-photon emission strongly correlated to the $b\to s\gamma$ amplitude which is sharply constrained by experiment. A quite general statement follows: as long as non-standard physics effects appear only in the matching of the Wilson coefficients of the standard effective operator basis, the deviations from the standard model expectations of the decay rates induced by $b\to s\gamma\gamma$ are bound to follow closely the corresponding deviations on $b\to s\gamma$. Effects of new physics are therefore bound to be small.
The Relevance of the Dipole Penguin Operators in $ε'/ε$
S. Bertolini,M. Fabbrichesi,E. Gabrielli
Physics , 1993, DOI: 10.1016/0370-2693(94)91541-5
Abstract: The standard model contribution to $\epsilon'/\epsilon$ of the magnetic- and electric-dipole penguin operators $Q_{11} = \frac{g_s}{16\pi^2} \, m_s \: \bar{s}\, \sigma_{\mu\nu} t^a G^{\mu\nu}_a (1-\gamma_5 )\, d $ and $Q_{12} = \frac{eQ_d}{16\pi^2}\, m_s \: \bar{s}\, \sigma_{\mu\nu} F^{\mu\nu} (1-\gamma_5 )\, d $ is discussed. While the electromagnetic penguin $Q_{12}$ seems to have a vanishingly small matrix element, we find that the gluonic dipole operator $Q_{11}$ may give a contribution to $\epsilon'/\epsilon$ comparable to that of other operators so far considered, and should therefore be consistently included in the analysis.
Studying $\varepsilon '/\varepsilon$ in the Chiral Quark Model: $γ_5$-Scheme Independence and NLO Hadronic Matrix Elements
S. Bertolini,J. O. Eeg,M. Fabbrichesi
Physics , 1994, DOI: 10.1016/0550-3213(95)00274-V
Abstract: We study the $CP$-violating, $|\Delta S| =1$ parameter $\varepsilon '/\varepsilon$ by computing the hadronic matrix elements in the chiral quark model. We estimate the coefficients of the next-to-leading order terms in the chiral expansion that correspond to the operators $Q_6$ and $Q_{11}$. We consider the impact of these corrections on the value of $\varepsilon '/\varepsilon$. We also investigate the possibility that the chiral quark model might drastically reduce the dimensional regularization $\gamma_5$-scheme dependence of current evaluations of $\varepsilon '/\varepsilon$.
A New Estimate of $\varepsilon '/\varepsilon$
S. Bertolini,J. O. Eeg,M. Fabbrichesi
Physics , 1995, DOI: 10.1016/0550-3213(96)00335-5
Abstract: We discuss direct $CP$ violation in the standard model by giving a new estimate of $\varepsilon'/\varepsilon$ in kaon decays. Our analysis is based on the evaluation of the hadronic matrix elements of the \mbox{$\Delta S =1$} effective quark lagrangian by means of the chiral quark model, with the inclusion of meson one-loop renormalization and NLO Wilson coefficients. Our estimate is fully consistent with the $\Delta I =1/2$ selection rule in $K\to \pi\pi$ decays which is well reproduced within the same framework. By varying all parameters in the allowed ranges and, in particular, taking the quark condensate---which is the major source of uncertainty---between $(-200\ {\rm MeV})^3$ and $(-280\ {\rm MeV})^3$ we find $$ -5.0 \times 10^{-3}\ <\varepsilon'/\varepsilon <\ 1.4 \times 10^{-3}\ .$$ Assuming for the quark condensate the improved PCAC result \mbox{$\vev{\bar qq} = -(221\: \pm 17\ {\rm MeV})^3$} and fixing $\Lambda_{\rm QCD}^{(4)}$ to its central value, we find the more restrictive prediction $$\varepsilon '/\varepsilon = ( 4 \pm 5 ) \,\times \,10^{-4}\ , $$ where the central value is defined as the average over the allowed values of Im $\lambda_t$ in the first and second quadrants. In these estimates the relevant mixing parameter Im $\lambda_t$ is self-consistently obtained from $\varepsilon$ and we take $m_t^{\rm pole} = 180 \pm 12$ GeV. Our result is, to a very good approximation, renormalization-scale and $\gamma_5$-scheme independent.
Estimating epsilon'/epsilon. A Review
S. Bertolini,J. O. Eeg,M. Fabbrichesi
Physics , 1998, DOI: 10.1103/RevModPhys.72.65
Abstract: The real part of epsilon'/epsilon measures direct CP violation in the decays of the neutral kaons in two pions. It is a fundamental quantity which has justly attracted a great deal of theoretical as well as experimental work. Its determination may answer the question of whether CP violation is present only in the mass matrix of neutral kaons (the superweak scenario) or also at work directly in the decays. After a brief historical summary, we discuss the present and expected experimental sensitivities. In the light of these, we come to the problem of estimating epsilon'/epsilon in the standard model. We review the present (circa 1998) status of the theoretical predictions of epsilon'/epsilon. The short-distance part of the computation is now known to the next-to-leading order in QCD and QED and therefore well under control. On the other hand, the evaluation of the hadronic matrix element of the relevant operators is where most of the theoretical uncertainty still resides. We analyze the results of the currently most developed calculations. The values of the B_i parameters in the various approaches are discussed, together with the allowed range of the relevant combination of the Cabibbo-Kobayashi-Maskawa entries Im V_{td}V^*_{ts}. We conclude by summarizing and comparing all up-to-date predictions of epsilon'/epsilon. Because of the intrinsic uncertainties of the long-distance computations, values ranging from 10^{-4} to a few times 10^{-3} can be accounted for in the standard model. Since this range covers most of the present experimental uncertainty, it is unlikely that new physics effects can be disentangled from the standard model prediction. For updates on the review and additional material see http://www.he.sissa.it/review/.
Nitrous oxide emissions from soil of an African rain forest in Ghana
S. Castaldi,T. Bertolini,A. Valente,T. Chiti
Biogeosciences Discussions , 2012, DOI: 10.5194/bgd-9-16565-2012
Abstract: Most recently atmospheric studies have evidenced the imprint of large N2O sources in tropical/subtropical lands. This source might be attributed to agricultural areas as well as to natural humid ecosystems. The uncertainty related to both sources is very high, due to the paucity of data and small frequency of sampling in tropical studies. This is particularly relevant for the African continent. The principal objective of this work was to quantify the annual budget of N2O emissions in an African tropical rain forest. Soil N2O emissions were measured over 19 months in Ghana, National Park of Ankasa, in upland and lowland areas, for a total of 119 days of observation. The calculated annual average emission was 2.33 ± 0.20 kg N-N2O ha 1yr 1, taking into account the proportion of upland vs. lowland, as the two areas showed significantly different fluxes, the lowland being characterized by lower N2O emissions. N2O fluxes peaked between June and August and were significantly correlated with soil respiration on a daily and monthly basis. No clear correlation was found in the upland areas between N2O fluxes and soil water content or rain whereas in the lowland soil water content concurred with soil respiration in determining N2O flux variability. The N2O source strength calculated in this study, very close to those reported for the other two available studies in African rain forests and to the estimated mean derived from worldwide studies in humid tropical forests (2.96 ± 2.0 kg N-N2O ha 1 yr 1), supports the concept that tropical humid forests represent the strongest natural source of N2O emissions, most probably the strongest source of N2O in the African continent.
Estudo da capacidade funcional ventilatória dos profissionais cabeleireiros da cidade de Maringá, Estado do Paraná, no ano de 2005 = Hairdressers′ ventilatory functional capacity study in the city of Maringá, State of Paraná, in 2005
Amanda Bespalhok Beloto,S?nia Maria Marques Gomes Bertolini
Acta Scientiarum : Health Sciences , 2006,
Abstract: Este estudo teve como objetivo verificar a capacidade funcional ventilatória dos profissionais cabeleireiros da cidade de Maringá, Estado do Paraná, no ano de 2005, bem como a prevalência dos distúrbios ventilatórios. A amostra da pesquisa foi constituída por100 profissionais cabeleireiros e 30 secretários. Os primeiros foram submetidos a uma entrevista e avalia o do aparelho respiratório, seguido da espirometria; já o segundo grupo foi questionado quanto aos hábitos pessoais e submetido à espirometria. Com a metodologiautilizada, constatou-se que, dos 100 profissionais da área avaliados, 17% apresentaram algum distúrbio ventilatório, sendo 14% distúrbios ventilatórios obstrutivos e 3% distúrbios ventilatórios restritivos, ambos classificados como leve. No grupo dos secretários, 100%exibiram valores espirométricos normais, porém, 40% apresentaram implica o para a ocorrência de obstru o. Conclui-se que é alta a prevalência de distúrbios ventilatórios em cabeleireiros; contudo, sugere-se a realiza o de estudos longitudinais para investiga o dascondi es de trabalho desses profissionais. This research aimed to verify the hairdressers′ ventilatory functional capacity in Maringá, State of Paraná, city in 2005 and the prevalence of the ventilatory disorders. The sample of the research was constituted by 100 hairdressers and 30 secretaries. The former was submitted to an interview and to an evaluation of the respiratory system, followed by the spirometry; the second group was interviewed about personal habits, and they were submitted to the spirometry. Results pointed that 17% of the hairdressers had some ventilatory disorder, and 14% of these were obstructive ventilatory disorder and 3% were restrictive ventilatory disorder, and both were classified as light disorders. In the secretaries group, 100% showed spirometric values into the normality standard. Based in these results it can be concluded that the ventilatory disorder happens among the hairdressers, however, new studies must be done to investigate the work conditions of these professionals.
Page 1 /325443
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.