arXiv subjects

Marco Guzzi

Publications and source records attributed to Marco Guzzi.

82 records · Page 5Linked to original sources

arXiv2006

QCD Studies at Hadron Colliders and in Deeply Virtual Neutrino Scattering

This thesis work summarizes studies in QCD for applications both at hadron colliders and in exclusive processes. In the first part we focus our attention on the study of the initial state scaling violations and the evolution of the unpolarized parton distributions through Next-to-Next to Leading Order (NNLO) in $α_s$, the strong coupling, suitable for precision studies of the parton model at the LHC. Specifically, we analize the methods available to solve the equations and develope the theory of the logarithmic expansions at the same perturbative order. A study of the Higgs total cross section is included. The theoretical analysis is accompanied by the developement of professional software partly documented in this thesis. We also include one study of the evolution of the transverse spin distributions (the Soffer inequality) and a parallel study of the asymmetries for the Drell-Yan process for the proposed Pax experiment at GSI at NLO. In the second part we introduce the extension of Deeply Virtual Compton Scattering to the electroweak sector for neutrino detection at neutrino factories at intermediate energy.

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arXiv2006

Deeply Virtual Neutrino Scattering at Leading Twist

We illustrate the generalization of results concerning exclusive electromagnetic processes in the deeply virtual limit (DVCS) to the case of the weak interactions.We briefly describe the derivation of the differential cross section for neutrino-nucleon reactions mediated by the neutral current and the amplitude for similar reactions mediated by the charged currents.

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arXiv2006

Double Transverse-Spin Asymmetries in Drell-Yan Processes with Antiprotons

We present next-to-leading order predictions for double transverse-spin asymmetries in Drell--Yan dilepton production initiated by proton--antiproton scattering. The kinematic region of the proposed PAX experiment at GSI: $30\lesssim{s}\lesssim200\GeV^2$ and $2\lesssim{M}\lesssim7\GeV$ is examined. The Drell--Yan asymmetries turn out to be large, in the range 20--40%. Measuring these asymmetries would provide the cleanest determination of the quark transversity distributions.

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arXiv2006

NNLO Logarithmic Expansions and Exact Solutions of the DGLAP Equations from x-Space: New Algorithms for Precision Studies at the LHC

A NNLO analysis of certain logarithmic expansions, developed for precision studies of the evolution of the QCD parton distributions (pdf) at the Large Hadron Collider, is presented. We elaborate on their relations to all the solutions of the DGLAP equations that have been hitherto obtained from Mellin space, to which are equivalent. Exact expansions, equivalent to exact solutions of the equations, are constructed in the non-singlet sector. The algorithmic features of our approach are also emphasized, since this method allows to obtain numerical solutions of the evolution equations with the same accuracy of other methods, based on Mellin space, and of brute force methods, which solve the equations by finite differences. The implementation of our analysis allows to compare with existing benchmarks for the evolution of the pdf's, useful for applications at the LHC, and to extend them significantly in a systematic fashion, especially when solutions that retain logarithmic corrections only of a certain accuracy are searched for.

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arXiv2006

Parton Distributions, Logarithmic Expansions and Kinetic Evolution

Aspects of the QCD parton densities are briefly reviewed, drawing some parallels to the density matrix formulation of quantum mechanics, exemplified by Wigner functions. We elaborate on the solution of their evolution equations using logarithmic expansions and overview their kinetic interpretation. We illustrate how a Fokker-Planck equation can be derived using the master formulation of the same equations and its construction in the case of the transverse spin distributions. A simple connection of the leading order DGLAP equation to fractional diffusion using fractional calculus is also briefly outlined.

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arXiv2005

On the Scale Variation of the Total Cross Section for Higgs Production at the LHC and at the Tevatron

We present a detailed study of the total $p p$ cross section for scalar Higgs production to next-to-next-to leading order in $α_s$ at LHC energies, and of the $p\bar p$ cross section at the Tevatron, combining an implementation of the solutions of the parton evolution equations at the 3-loop order with the corresponding hard scatterings, evaluated at the same perturbative order. Our solutions of the DGLAP equations are implemented directly in $x$-space and allow the study of the dependence of the results on the factorization ($μ_F$) and renormalization scales $(μ_R)$ typical of a given process, together with the stability of the perturbative expansion. The input sets for the parton evolutions are those given by Martin, Roberts, Stirling and Thorne and by Alekhin. Results for K-factors are also presented. The NNLO corrections can be quite sizeable at typical collider energies. The stability region of the perturbative expansion is found when $μ_R > m_H\simμ_F$.

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arXiv2005

Deeply Virtual Neutrino Scattering (DVNS)

We introduce the study of neutrino scattering off protons in the deeply virtual kinematics, which describes under a unified formalism elastic and deep inelastic neutrino scattering. A real final state photon and a recoiling nucleon are detected in the few GeV ($|t|\sim 0.2-5$ GeV) region of momentum transfer. This is performed via an extension of the notion of deeply virtual Compton scattering, or DVCS, to the case of a neutral current exchange. The relevance of this process and of other similar exclusive processes for the study of neutrino interactions in neutrino factories for GeV neutrinos is pointed out.

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arXiv2005

Leading Twist Amplitudes for Exclusive Neutrino Interactions in the Deeply Virtual Limit

Neutrino scattering on nucleons in the regime of deeply virtual kinematics is studied both in the charged and the neutral electroweak sectors using a formalism developed by Blumlein, Robaschik, Geyer and Collaborators for the analysis of the Virtual Compton amplitude in the generalized Bjorken region. We discuss the structure of the leading twist amplitudes of the process.

hep-ph↗

arXiv2003

Using and Constraining Nonforward Parton Distributions (Deeply Virtual Neutrino Scattering in Cosmic Rays and Light Dark Matter Searches)

We overview the construction of Nonforward Parton Distributions (NPD) in Deeply Virtual Compton Scattering (DVCS). Then we turn to the analysis of similar constructs in the weak sector (electroweak NPD's). We argue in favour of a possible use of electroweak DVCS (EWDVCS) as a rare process for the study of neutrinos in cosmic rays and for light dark matter detection in underground experiments

hep-ph↗

arXiv2003

An x-Space Analysis of Evolution Equations: Soffer's Inequality and the Non-forward Evolution

We analize the use of algorithms based in x-space for the solution of renormalization group equations of DGLAP-type and test their consistency by studying bounds among partons distributions - in our specific case Soffer's inequality and the perturbative behaviour of the nucleon tensor charge - to next-to-leading order in QCD . A discussion of the perturbative resummation implicit in these expansions using Mellin moments is included. We also comment on the (kinetic) proof of positivity of the evolution of $h_1$, using a kinetic analogy and illustrate the extension of the algorithm to the evolution of generalized parton distributions. We prove positivity of the non-forward evolution in a special case and illustrate a Fokker-Planck approximation to it.

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