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Pietro Falgari

Publications and source records attributed to Pietro Falgari.

10 recordsLinked to original sources
arXiv2017

Comparison of a modal-decomposition and a grid based field solver for free-electron laser simulations

We present a comparison of the modal-decomposition based field solver MINERVA to the grid-based solver GENESIS. The modal decomposition used employs a set of fixed-width, zero-curvature Gaussian modes, as opposed to the more-commonly used basis of vacuum-diffraction eigenmodes. Besides providing the dynamical equations for the field modal amplitudes, we give first-principle estimates of the number of modes required to achieve completeness in terms of field and source modal representation as a function of the electron-current and mode size. As a practical application of this new framework, we present steady-state numerical results for several configurations. The numerical results show a good agreement between the modal expansion and the grid-based solver, not only in terms of the total energy produced, but also in terms of the transverse radiation profile.

physics.acc-ph↗
arXiv2013

SM single-top production at hadron colliders

We give an overview of the status of theoretical predictions for single-top production in the Standard Model. We focus in particular on recent developments, including calculations of off-shell effects at next-to-leading order beyond the narrow-width approximation, all-order resummation of soft corrections and matching of next-to-leading order parton-level results to Monte Carlo parton showers.

hep-ph↗
arXiv2012

Finite-width effects on threshold corrections to squark and gluino production

We study the implication of finite squark and gluino decay widths for threshold resummation of squark and gluino production cross sections at the LHC. We find that for a moderate decay width (Gamma/m < 5%) higher-order soft and Coulomb corrections are appropriately described by NLL calculations in the zero-width limit including the contribution from bound-state resonances below threshold, with the remaining uncertainties due to finite-width effects of a similar order as the ambiguities of threshold-resummed higher-order calculations.

hep-ph↗
arXiv2010

Threshold resummation for pair production of coloured heavy (s)particles at hadron colliders

We derive a factorization formula for the production of pairs of heavy coloured particles in hadronic collisions near the production threshold that establishes factorization of soft and Coulomb effects. This forms the basis for a combined resummation of Coulomb and soft corrections, including the non-trivial interference of the two effects. We develop a resummation formalism valid at NNLL accuracy using the momentum-space approach to soft gluon resummation. We present numerical results for the NLL resummed squark-antisquark production cross section at the LHC and Tevatron, including also the contribution of squark-antisquark bound states below threshold. The total correction on top of the next-to-leading order approximation is found to be sizeable, and amounts to (4-20)% in the squark mass region 200 GeV-3 TeV at the 14 TeV LHC. The scale dependence of the total cross section is also reduced.

hep-ph↗
arXiv2010

Production-decay interferences at NLO in QCD for t-channel single-top production

We present a calculation of O(α_s) contributions to the process of t-channel single-top production and decay, which include virtual and real corrections arising from interference of the production and decay subprocesses. The calculation is organized as a simultaneous expansion of the matrix elements in the couplings α_{ew},α_s and the virtuality of the intermediate top quark, (p_t^2-m_t^2)/m_t^2 ~ Γ_t/m_t, and extends earlier results beyond the narrow-width approximation.

hep-ph↗
arXiv2010

Resonant particle production at hadron colliders

We present a method to compute off-shell effects for processes involving resonant particles at hadron colliders with the possibility to include realistic cuts on the decay products. The method is based on an effective theory approach to unstable particle production and, as an example, is applied to t-channel single top production at the LHC.

hep-ph↗
arXiv2009

Colour structure in threshold resummation and squark-antisquark production at NLL

We consider the resummation of soft and Coulomb gluons for pair-production processes of heavy coloured particles at hadron colliders, and discuss recent results on the construction of a basis in colour space that diagonalizes the soft function to all orders in perturbation theory and the determination of the two-loop soft anomalous dimension needed for NNLL resummations. We present results for the combined NLL resummation of soft gluon and Coulomb-gluon effects for squark-antisquark production at the LHC.

hep-ph↗
arXiv2007

Four-fermion production near the W pair production threshold

We perform a dedicated study of the four-fermion production process e- e+ -> mu- nubar_mu u dbar X near the W pair-production threshold in view of the importance of this process for a precise measurement of the W boson mass. Accurate theoretical predictions for this process require a systematic treatment of finite-width effects. We use unstable-particle effective field theory (EFT) to perform an expansion in the coupling constants, GammaW/MW, and the non-relativistic velocity v of the W boson up to next-to-leading order in GammaW/MW ~ alpha_ew ~ v^2. We find that the dominant theoretical uncertainty in MW is currently due to an incomplete treatment of initial-state radiation. The remaining uncertainty of the NLO EFT calculation translates into delta MW ~ 10-15 MeV, and to about 5 MeV with additional input from the NLO four-fermion calculation in the full theory.

hep-ph↗
arXiv2007

BFKL at Next-to-Next-to-Leading Order

We determine an approximate expression for the O(alpha_s^3) contribution chi_2 to the kernel of the BFKL equation, which includes all collinear and anticollinear singular contributions. This is derived using recent results on the relation between the GLAP and BFKL kernels (including running-coupling effects to all orders) and on small-x factorization schemes. We present the result in various schemes, relevant both for applications to the BFKL equation and to small-x evolution of parton distributions.

hep-ph↗