Partonic Energy Loss and the Drell-Yan Process

We examine the current status of the extraction of the rate of partonic energy loss in nuclei from A dependent data. The advantages and difficulties of using the Drell-Yan process to measure the energy loss of a parton traversing a cold nuclear medium are discussed. The prospects of using relatively low energy proton beams for a definitive measurement of partonic energy loss are presented.Comment: 12 pages, 2 figure

Using non-participant observation to uncover mechanisms: insights from a realist evaluation

This article outlines how a realist evaluation of dementia care in hospitals used non-participant observation to support the refinement and testing of mechanisms likely to lead to the use of person-centred care. We found that comments and explanations of their actions from hospital staff during observation periods provided insights into the reasoning that generated their actions for care in real time. This informed subsequent data collection and analysis. Two worked examples of mechanisms first identified during non-participant observation demonstrate (1) how they were uncovered, and (2) how this informed research activities for theory refinement. Early, iterative engagement with the analytic process, primarily involving reflection and debate with the research team, maximised the potential of observation data to support surfacing underlying mechanisms, linking them to specific contexts and outcomes.Peer reviewedFinal Accepted Versio

"Does anyone even notice us?" COVID-19’s impact on academics’ well-being in a developing country

In March 2020, the President of South African announced that the nation would go into full lockdown in the wake of an increase in COVID-19 infections. Academics had, in some instances, only one day to prepare for “emergency remote teaching”. Few academics had taught online before, as South Africa’s internet connectivity is not guaranteed in underprivileged areas, where 80 per cent of the population reside. The online move thus necessitated an entirely novel pedagogy for most academics, with high potential for an escalation of work-related stress and related illness, outcomes we have related in the wider sphere of workplace readjustment during COVID-19, to a state of “pandemia”. In this article, we report on an institutional case study where we surveyed n=136 academics from a university in the Western Cape, South Africa to learn more about impacts of COVID-19 on their work. The data analysis adopts Ryff’s (1995) theory of well-being. Findings indicate that the enforced lockdown due to COVID-19 and the subsequent move to online teaching has had a negative impact on academics’ sense of well-being. However, the emergence of positive, caring relationships between colleagues is reported as a significant outcome of the COVID-19 enforced move to online teaching

Resummation of nuclear enhanced higher twist in the Drell Yan process

We investigate higher twist contributions to the transverse momentum broadening of Drell Yan pairs in proton nucleus collisions. We revisit the contribution of matrix elements of twist-4 and generalize this to matrix elements of arbitrary twist. An estimate of the maximal nuclear broadening effect is derived. A model for nuclear enhanced matrix elements of arbitrary twist allows us to give the result of a resummation of all twists in closed form. Subleading corrections to the maximal broadening are discussed qualitatively.Comment: 10 pages, 5 figures; v2: minor changes in text, acknowledgement added; v3: mistake in fig. 1 correcte

HT2009-88029 THERMAL CONDUCTIVITY OF WATER/CARBON NANOTUBE COMPOSITE SYSTEMS: INSIGHTS FROM MOLECULAR DYNAMICS SIMULATIONS

ABSTRACT The INTRODUCTION Due to their high thermal conductivities, graphene sheets and carbon nanotubes (CNT) are ideal candidates for nextgeneration thermal management device

PhD from the University of South Carolina. He has published research in the

Abstract: The worldwide elderly population continues to grow, in terms of raw numbers as well as their use of computers and the internet. These facts notwithstanding, it appears that vendors of information technology products, both hardware and software, have largely ignored seniors. Research has shown that these 'silver surfers' are one of that fastest-growing user groups online and, furthermore, have more disposable income than any other segment of modern society. This paper investigates elderly computer and internet usage by incorporating the results of three separate research streams that have reported on this topic. Implications for both practice and research are presented

Energy loss of fast quarks in nuclei

We report an analysis of the nuclear dependence of the yield of Drell-Yan dimuons from the 800 GeV/c proton bombardment of $^2H$, C, Ca, Fe, and W targets. Employing a new formulation of the Drell-Yan process in the rest frame of the nucleus, this analysis examines the effect of initial-state energy loss and shadowing on the nuclear-dependence ratios versus the incident proton's momentum fraction and dimuon effective mass. The resulting energy loss per unit path length is $-dE/dz = 2.32 \pm 0.52\pm 0.5$ GeV/fm. This is the first observation of a nonzero energy loss of partons traveling in nuclear environment.Comment: 5 pages, including 4 figure

Open and Hidden Charm Production in Heavy Ion Collisions at Ultrarelativistic Energies

We consider the production of the open charm and J/psi mesons in heavy ion collisions at BNL RHIC. We discuss several recently developed pictures for J/psi production and argue that a measurement at RHIC energies is crucial for disentangling these different descriptions.Comment: 19 pages, Latex, 5 PS-figures. v3: Fig.6 is adde

Role of the nonperturbative input in QCD resummed Drell-Yan QTQ_T-distributions

We analyze the role of the nonperturbative input in the Collins, Soper, and Sterman (CSS)'s $b$-space QCD resummation formalism for Drell-Yan transverse momentum ($Q_T$) distributions, and investigate the predictive power of the CSS formalism. We find that the predictive power of the CSS formalism has a strong dependence on the collision energy $\sqrt{S}$ in addition to its well-known $Q^2$ dependence, and the $\sqrt{S}$ dependence improves the predictive power at collider energies. We show that a reliable extrapolation from perturbatively resummed $b$-space distributions to the nonperturbative large $b$ region is necessary to ensure the correct $Q_T$ distributions. By adding power corrections to the renormalization group equations in the CSS formalism, we derive a new extrapolation formalism. We demonstrate that at collider energies, the CSS resummation formalism plus our extrapolation has an excellent predictive power for $W$ and $Z$ production at all transverse momenta $Q_T\le Q$. We also show that the $b$-space resummed $Q_T$ distributions provide a good description of Drell-Yan data at fixed target energies.Comment: Latex, 43 pages including 15 figures; typos were correcte

Rapidity Distributions of Dileptons from a Hadronizing Quark-Gluon Plasma

It has been predicted that dilepton production may be used as a quark-gluon plasma probe. We calculate the rapidity distributions of thermal dileptons produced by an evolving quark-gluon plasma assuming a longitudinal scaling expansion with initial conditions locally determined from the hadronic rapidity density. These distributions are compared with Drell-Yan production and semileptonic charm decays at invariant mass $M = 2$, 4, and 6 GeV.Comment: 17 pages (standard LaTeX), 6 figures (available as topdraw files or printed versions upon request), GSI-93-6