General partonic structure for hadronic spin asymmetries

The high energy and large p_T inclusive polarized process, (A, S_A) + (B, S_B) --> C + X, is considered under the assumption of a generalized QCD factorization scheme. For the first time all transverse motions, of partons in hadrons and of hadrons in fragmenting partons, are explicitly taken into account; the elementary interactions are computed at leading order with noncollinear exact kinematics, which introduces many phases in the expressions of their helicity amplitudes. Several new spin and k_T dependent soft functions appear and contribute to the cross sections and to spin asymmetries; we put emphasis on their partonic interpretation, in terms of quark and gluon polarizations inside polarized hadrons. Connections with other notations and further information are given in some Appendices. The formal expressions for single and double spin asymmetries are derived. The transverse single spin asymmetry A_N, for p(transv. polarized) p --> pion + X processes is considered in more detail, and all contributions are evaluated numerically by saturating unknown functions with their upper positivity bounds. It is shown that the integration of the phases arising from the noncollinear kinematics strongly suppresses most contributions to the single spin asymmetry, leaving at work predominantly the Sivers effect and, to a lesser extent, the Collins mechanism.Comment: RevTeX, 46 pages, 5 ps figures. v2: some clarifying comments and appendix on kinematics added, references updated, published versio

On the non-vanishing of the Collins mechanism for single spin asymmetries

The Collins mechanism provides a non-perturbative explanation for the large single spin asymmetries found in hard semi-inclusive reactions involving a transversely polarized nucleon. However, there are seemingly convincing reasons to suspect that the mechanism vanishes, and indeed it does vanish in the naive parton model where a quark is regarded as an essentially 'free' particle. We give an intuitive analysis which highlights the difference between the naive picture and the realistic one, and shows how the Collins mechanism arises when the quark is described as an off-shell particle by a field in interaction. A typographical error is corrected in this version.Comment: 15 pages, 2 figure

Spin Structure of the Nucleon - Status and Recent Results

After the initial discovery of the so-called "spin crisis in the parton model" in the 1980's, a large set of polarization data in deep inelastic lepton-nucleon scattering was collected at labs like SLAC, DESY and CERN. More recently, new high precision data at large x and in the resonance region have come from experiments at Jefferson Lab. These data, in combination with the earlier ones, allow us to study in detail the polarized parton densities, the Q^2 dependence of various moments of spin structure functions, the duality between deep inelastic and resonance data, and the nucleon structure in the valence quark region. Together with complementary data from HERMES, RHIC and COMPASS, we can put new limits on the flavor decomposition and the gluon contribution to the nucleon spin. In this report, we provide an overview of our present knowledge of the nucleon spin structure and give an outlook on future experiments. We focus in particular on the spin structure functions g_1 and g_2 of the nucleon and their moments.Comment: 69 pages, 46 figures. Report to be published in "Progress in Particle and Nuclear Physics". v2 with added references and minor edit

Mutual Shaping of Tele-Healthcare Practice: Exploring Community Perspectives on Telehealth Technologies in Northern and Indigenous Contexts

In Canada, northern and Indigenous communities face well documented challenges to accessing healthcare services prompting the urgent need to adopt alternative and innovative solutions to overcome barriers of limited access due to geographic distance, physician shortages, limited resources, and high cost of service delivery. Telehealth – the means of delivering health care services and information across distance – promises to augment services to address some of these barriers and has been increasingly relied upon to bridge healthcare service gaps. Despite the promise of telehealth, notable utilization barriers and structural constraints remain that challenge long-term sustainability. Little is known about how well these technologies work from community telehealth users’ perspectives. Current work in the area has tended to focus on the increased efficiency and cost effectiveness of telehealth in facilitating healthcare services, with less focus on users’ perspectives obscuring the important roles played by users and technologies. In sum, more work needs to be done to present a complete picture of users’ experiences and community needs – a gap this dissertation aims to tackle. In doing so, this research captures a snapshot of community perspectives from four Northern Saskatchewan communities, drawing attention to users’ experiences in relation to the social and technical factors shaping telehealth use. Working in partnership with the communities of Hatchet Lake Denesuline First Nation, the Northern Villages of Île-à-la-Crosse and Pinehouse Lake, and the Town of La Ronge, and external stakeholders/knowledge users working directly with these communities, this work resulted in valuable insights into the user-technology interface. Emerging from community concerns with accessing healthcare services and education/training, the goal of this project was to better understand strengths and barriers for telehealth use. Methodologically, the personal accounts and lived experiences of telehealth users were explored using qualitative methods grounded in Community-Based Participatory Research (CBPR) and decolonizing methodologies utilizing Constructivist Grounded Theory (CGT) that is drawn from interpretive-constructivist epistemological frameworks. In-depth, semi-structured qualitative interviews/focus groups with 24 telehealth users, field notes and general observations provided the basis for data collection, and NVivo 12 was used to organize, iteratively code and analyze community insights. Thematic analysis and socio-technical mapping explored themes across community contexts and provided understanding of the interrelationship of shared and unique insights whereby community telehealth users’ voices guided interpretations. This dissertation highlights the importance of community collaborations and identifies the strengths and barriers for utilizing telehealth within northern and Indigenous contexts. Using theoretical frameworks drawn from Science and Technology Studies (STS), this dissertation makes the argument that users and technologies play significant roles in shaping tele-healthcare practice – a mutually co-constitutive relationship embedded within larger socio-structural systems that pose varying constraints. Analysis revealed that users and technologies mutually shape tele-healthcare practices and care experiences – i.e. technologies shape patients’ and local/remote providers’ use of the system in enabling/constraining ways and users shape technologies through reconfiguration or “tinkering”. A mutual shaping approach following the relational/performative view of socio-technical agency serves as a pathway for examining socio-cultural factors shaping how technologies are designed, implemented, and used, and alternatively how technologies shape practice and meanings of socio-technical spaces. Further, it is argued that understanding the context in which telehealth technologies are situated and experienced will be increasingly critical as technological systems play greater roles in service delivery

General helicity formalism for Single and Double Spin Asymmetries in p p --> pion + X

We consider within a generalized QCD factorization approach, the high energy inclusive polarized process p p --> pion + X, including all intrinsic partonic motions. Several new spin and k_T-dependent soft functions appear and contribute to cross sections and spin asymmetries. We present here formal expressions for transverse single spin asymmetries and double longitudinal ones. The transverse single spin asymmetry, A_N, is considered in detail, and all contributions are evaluated numerically. It is shown that the azimuthal phase integrations strongly suppress most contributions, leaving at work mainly the Sivers effect.Comment: LaTeX, 5 pages, 1 eps figure, uses epsfig, wrapfig. Talk delivered by S. Melis at the ``XI Workshop on High Energy Spin Physics'', SPIN 05, September 27 - October 1, 2005, Dubna, Russi

Helicity Formalism and Spin Asymmetries in Hadronic Processes

We present a generalized QCD factorization scheme for the high energy inclusive polarized process, (A, S_A) + (B, S_B) -> C + X, including all intrinsic partonic motions. This introduces many non-trivial azimuthal phases and several new spin and k_T dependent soft functions. The formal expressions for single and double spin asymmetries are discussed. Numerical results for A_N[p(transv. polarized) p -> pi + X] are presented.Comment: 8 pages, 4 ps figures, uses ws-procs9x6.cls and rotating_pr.sty (included). Talk delivered by F. Murgia at the "International Workshop on Transverse Polarisation Phenomena in Hard Processes" (TRANSVERSITY 2005), September 7-10 2005, Como, Ital