Charge symmetry violation: An NNLO study of partonic observables

Self Cite

The correct description of Double Parton Scattering (DPS), which represents a background in several channels for the search of new Physics at the LHC, requires the knowledge of double parton distribution functions (dPDFs). These quantities represent also a novel tool for the study of the three-dimensional nucleon structure, complementary to the possibilities offered by electromagnetic probes. In this paper we analyze dPDFs using Poincaré covariant predictions obtained by using a Light-Front constituent quark model proposed in a recent paper, and QCD evolution. We study to what extent factorized expressions for dPDFs, which neglect, at least in part, two-parton correlations, can be used. We show that they fail in reproducing the calculated dPDFs, in particular in the valence region. Actually measurable processes at existing facilities occur at low longitudinal momenta of the interacting partons; to have contact with these processes we have analyzed correlations between pairs of partons of different kind, finding that, in some cases, they are strongly suppressed at low longitudinal momenta, while for other distributions they can be sizeable. For example, the effect of gluon-gluon correlations can be as large as 20 %. We have shown that these behaviors can be understood in terms of a delicate interference of non-perturbative correlations, generated by the dynamics of the model, and perturbative ones, generated by the model independent evolution procedure. Our analysis shows that at LHC kinematics two-parton correlations can be relevant in DPS, and therefore we address the possibility to study them experimentally.

Section: Calculating Double Parton Distribution Functionsmentioning

confidence: 99%

Section: Adding Sea Quarks and Gluons At A Low Energy Scalementioning

confidence: 99%

Correlations in double parton distributions: perturbative and non-perturbative effects

Rinaldi

Scopetta

Traini

et al. 2016

Self Cite

“…For the Weinberg angle we use the value measured in the hadronic processes to make sure that it is free of the non-unitarity corrections. The values of gL and gR are taken from the NuTeV results after including a recent NNLO analysis [43,65].…”

Section: Observablesmentioning

confidence: 99%

Improving electro-weak fits with TeV-scale sterile neutrinos

Akhmedov

Kartavtsev

Lindner

et al. 2013

106

170

We study the impact of TeV-scale sterile neutrinos on electro-weak precision observables and lepton number and flavour violating decays in the framework of a type-I see-saw extension of the Standard Model. At tree level sterile neutrinos manifest themselves via non-unitarity of the PMNS matrix and at one-loop level they modify the oblique radiative corrections. We derive explicit formulae for the S, T, U parameters in terms of the neutrino masses and mixings and perform a numerical fit to the electro-weak observables. We find regions of parameter space with a sizable active-sterile mixing which provide a better over-all fit compared to the case where the mixing is negligible. Specifically we find improvements of the invisible Z-decay width, the charged-to-neutralcurrent ratio for neutrino scattering experiments and of the deviation of the W boson mass from the theoretical expectation.

“…This is obtained within a relativistic, fully Poincaré covariant Light-Front approach (for comprehensive reports see, e.g., [47,48]). In this framework, successfully applied in Hadronic Physics in general (see, e.g., [49]) and for the calculation of parton distributions in particular (see, e.g., [50][51][52][53][54][55][56]), the active particles are on-shell and the "bad-support" problem does not arise. As it will be shown, this fact helps to recover the symmetries of the results, expected on general grounds, and to properly evaluate Mellin moments of the obtained distributions, for a formally correct pQCD evolution of the results.…”

Section: Contents 1 Introductionmentioning

confidence: 99%

Double parton correlations and constituent quark models: a light front approach to the valence sector

Rinaldi

Scopetta

Traini

et al. 2014

135

An explicit evaluation of the double parton distribution functions (dPDFs), within a relativistic Light-Front approach to constituent quark models, is presented. dPDFs encode information on the correlations between two partons inside a target and represent the non-perturbative QCD ingredient for the description of double parton scattering in proton-proton collisions, a crucial issue in the search of new Physics at the LHC. Valence dPDFs are evaluated at the low scale of the model and the perturbative scale of the experiments is reached by means of QCD evolution. The present results show that the strong correlation effects present at the scale of the model are still sizable, in the valence region, at the experimental scale. At the low values of x presently studied at the LHC the correlations become less relevant, although they are still important for the spin-dependent contributions to unpolarized proton scattering.