118,431 research outputs found
Threshold Resummation in B ---> X(c) l nu(l) Decays
No full textWe compute the QCD form factor resumming threshold logarithms in B → Xc + l + νl decays to next-to-leading logarithmic approximation.
We present an interpolation formula including soft as well as collinear effects softened by the non-vanishing charm mass.
The function A(ρ;αS) describes soft radiation collinearly enhanced off the charm quark and reduces to the standard double-logarithmic function A(αS) in the massless limit ρ →0. The function B(αS) describes hard collinear emission off the charm quark, being the standard jet function. D(αS) and Δ(αS) describe soft radiation not collinearly enhanced off the beauty and the charm quark respectively
Perturbative QCD at the LHC
No full textIn this brief overview, we discuss selected topics of perturbative QCD at the Large Hadron Collider (LHC). In particular we presents some recent results on parton densities, higher-order calculations, Sudakov resummation and parton showers
THRESHOLD RESUMMED SPECTRA IN B ---> X(U) L NU DECAYS IN NLO. I
No full textWe evaluate threshold resummed spectra in B -> Xu l nu decays in next-to-leading order. We present results for the distribution in the hadronic variables EX and m2X=E2X, for the distribution in EX and for the distribution in EX and El, where EX and mX are the total energy and the invariant mass of the final hadronic state Xu respectively and El is the energy of the charged lepton. We explicitly show that all these spectra (where there is no integration over the hadronic energy) can be directly related to the photon spectrum in B -> Xs gamma via short-distance coefficient function
Resummed mass distribution for jets initiated by massive quarks
No full textWe resum the invariant mass distribution of jets initiated by massive quarks in next-to-leading logarithmic approximation and beyond in heuristic way. We find that the inclusion of mass terms, in the N-moment space, results in the universal factor delta(N) (Q(2); m(2)) = exp [integral(1)(0) dz z(Q2/m2 (N-1))-1/1-z {- integral(m2(1-z))(m2(1-z)2) dk(perpendicular to)(2)/k(perpendicular to)(2) A[alpha(S)(k(perpendicular to)(2))] - B[alpha(S)(m(2)(1-z))] + D[alpha(S)(m(2)(1-z)(2))]}], taking into account dead-cone effects and soft radiation characteristic of massive charges. This factor multiplies the massless jet distribution function J(N) (Q(2)). In the above equation the variable N is rescaled by the mass correction parameter m(2)/Q(2) c/v decay spectra or the inclusion of beauty mass effects in t -> bW decays, are briefly sketched. (c) 2007 Elsevier B.V. All rights reserved
Comment on resummation of mass distribution for jets initiated by massive quarks
No full textWe compute in the heavy quark effective theory the soft coefficient D(2) entering the resummation of next-to-next-to-leading threshold logarithms for jets initiated by a quark with a small mass compared to the hard scale of the process. We find complete agreement with a previous computation in full QCD. Contrary to our previous guess, this coefficient turns out to be different from that one entering heavy flavor decay or heavy flavor fragmentation. (C) 2008 Elsevier B.V. All rights reserved
From a guaranteed Labour Makret to the « Flexible Worker » Model? The Transformation of Italian Unemployment Policy in the ‘90s
No full textThe Italian welfare state has often been described as a clear example of the Continentalwelfare state regime (Esping-Andersen, 1990 and 1999 and Pierson, 2001) and also, adoptingother conceptual lenses, an important member of the Southern European welfare state family(Ferrera, 1996). From the end of World War II, the institutions and policies adopted in Italyhave been clearly marked on the one hand by the predominance of a male bread-winnerlabour market model and on the other by the strong protection of workers (insiders) and weak(if existent) protection of the so called ‘outsiders’. The article is particularly focused on labour market regulation in Italy, trying to emphasise some key quantitative elements regarding the employment and unemployment dataover the years (§ 1), then the basic traits of the evolution of Italian labour market will bepresented (§ 2), the endogenous and exogenous pressures for change and the dynamics ofinstitutional change (§ 3) will be explored, whereas a discussion on the possible newinstitutional configuration with particular reference to a new Law (the so called Biagi2 Law,that might introduce further elements of change) will follow (§ 4). Some final remarks (§ 5)regarding the current debates in Italy will conclude the presentation of the Italian case.Italy; Europeanization; unemployment; employment policy; social policy
Mending nets in the South: Anti-poverty policies in Greece, Italy, Portugal and Spain
No full textThe marginal role of social assistance and the absence of minimum income programmes have long been thought to constitute defining characteristics of the southern European model of welfare. Nevertheless; over the 1990s significant innovations in this field have taken place. The paper aims to contribute to the analysis of recent developments by critically examining the experience of anti-poverty policies in Greece, Italy, Portugal and Spain. It is argued that the "patchiness" of safety nets in southern Europe is due to a unique set of constraints, the most relevant of which are the role of families and the "softness" of state institutions. A review of national profiles reveals that new policies introduced in all four countries mark progress towards redressing some of the historical imbalances of that weyare model. In particular, fully fledged mi. ni. mum i. ncome schemes now operate in Portugal and in certain Spanish regions, white an experiment involving a number of Italian municipalities is still in progress. In spite of this, the paper concludes that social safety nets in southern Europe remain frail in terms of institutional design as well as political support and legitimacy
100 Gbps PON L-band downstream transmission using IQ-MZM CD digital pre-compensation and DD ONU receiver
No full textWe propose a downstream direct-detection 100G-PON solution aided by chromatic dispersion digital pre-compensation using an IQ-MZM, allowing L-band operation and 29 dB power budget with low ONU complexity and without requiring single-sideband modulation
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