1,721,091 research outputs found
Where do we stand with a 3-D picture of the proton?
Full text linkWe are on the way to obtaining multi-dimensional “pictures” of the proton. The field is bursting with activities, both from the theoretical and experimental side. A brief selection of important achievements of the last years and open challenges for the future is presented. They are already well documented in the various reviews of this Topical Issue, but they are gathered here in a more condensed way for convenience, together with some additional remarks. The choice of the items included in this short overview is far from being complete and represents the view of the author
TMDs at work
No full textThe following lecture notes are an introduction to some aspects of transverse-momentum-dependent parton distribution functions (TMDs). Some parts of the present notes were not actually covered during the school, but are given here for reference
Models for Transverse-Momentum Distributions and Transversity
Full text linkI present a short review of models for transverse-momentum distributions and transversity, with a particular attention on general features common to many models. I compare some model results with experimental extractions. I discuss the existence of relations between different functions, their limits of validity, their possible use
Probing the transverse spin of quarks in deep inelastic scattering
Full text linkMulders, P.J.G. [Promotor
Single-spin asymmetries and Qiu-Sterman effect(s)
No full textI discuss the relation between the Qiu-Sterman effects on one hand and the Collins, Sivers and Boer-Mulders effects on the other hand. It was suggested before that some of these effects are in fact the same, thus providing interesting connections between transverse-momentum dependent twist-2 functions and collinear twist-3 functions. Here I propose an alternative way to reach similar conclusions
Evolution of the helicity and transversity Transverse-Momentum-Dependent parton distributions
No full textWe examine the QCD evolution of the helicity and transversity parton distribution functions when including also their dependence on transverse momentum. Using an appropriate definition of these polarized transverse momentum distributions (TMDs), we describe their dependence on the factorization scale and rapidity cutoff, which is essential for phenomenological application
The proton in 3D
No full textProtons and neutrons constitute the building blocks of normal matter, accounting for almost all the mass of our world. We are still far from understanding the intricacies and mysteries of their inner structure. In the course of several decades of successful studies, we dedicated our efforts to delving deeper and deeper into them. A few years ago, thanks to a fruitful synergy of theoretical and experimental progress, we started to collect unprecedented multi-dimensional images of the distribution of quarks and gluons inside protons and neutrons. These pictures of the universe within the nucleon challenge our comprehension of the underlying theory of quark and gluon dynamics (quantum chromo-dynamics—QCD) and at the same time put us face to face with fundamental questions, such as: What is the shape of the nucleon? What is the spin of the nucleon coming from
Transverse-momentum Dependent Functions in Semi-inclusive DIS.
Full text linkThe cross section for semi-inclusive deep inelastic scattering can be decomposed in terms of 18 structure functions. At low transverse momentum of the detected hadron, the structure functions can be expressed in terms of transverse-momentum-dependent parton distribution and fragmentation functions. Here, a few selected examples are illustrated and discussed
Constraining quark angular momentum through semi-inclusive measurements
No full textThe determination of quark angular momentum requires the knowledge of the generalized parton distribution E in the forward limit. We assume a connection between this function and the Sivers transverse-momentum distribution, based on model calculations and theoretical considerations. Using this assumption, we show that it is possible to fit nucleon magnetic moments and semi-inclusive single-spin asymmetries at the same time. This imposes additional constraints on the Sivers function and opens a plausible way to quantifying quark angular momentum
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