Measurements of jets in heavy ion collisions

The Quark-Gluon Plasma (QGP) is created in high energy heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). This medium is transparent to electromagnetic probes but nearly opaque to colored probes. Hard partons produced early in the collision fragment and hadronize into a collimated spray of particles called a jet. The partons lose energy as they traverse the medium, a process called jet quenching. Most of the lost energy is still correlated with the parent parton, contributing to particle production at larger angles and lower momenta relative to the parent parton than in proton-proton collisions. This partonic energy loss can be measured through several observables, each of which give different insights into the degree and mechanism of energy loss. The measurements to date are summarized and the path forward is discussed.Comment: Talk presented CIPANP201

Unemployment and AIDS: The Social-Democratic Challenge for South Africa

There are two major economic and social security challenges facing South Africa: addressing large-scale unemployment and the AIDS pandemic. As of 2003, an estimated 14% of all South Africans were HIV-positive, with over a thousand people dying each day of AIDS. According to the government household and labour-force surveys conducted from the mid-1990s onwards, about a third of the labour force is without work (Nattrass, 2000a). This amounts to about 4.7 million people and it is, without question, a socio-economic crisis of major proportions. The life-chances and living-standards of entire households are compromised when working-age adults cannot find employment (Seekings, 2003b). Households burdened by AIDS are in an especially difficult position (Desmond et al 2000, Steinberg et al 2002a, 2002b; Booysen, 2002; Booysen et al, 2002). Addressing AIDS and unemployment poses major challenges for social solidarity in South Africa. Over the past decade, the labour-market and industrial-policy environment has benefited relatively high-productivity firms and sectors (Nattrass, 2001). Business thus had strong incentives to reduce dependence on unskilled labour, and once the price of highly active antiretroviral therapy (HAART) started to fall from 2001 onwards, to supply it, either directly or indirectly through medical aids, to their increasingly skilled workforce (Nattrass, 2003). Those without jobs had neither access to earned income nor life-prolonging medication.

Unemployment, Employment and Labour-Force Participation in Khayelitsha/Mitchell's Plain

This paper provides a rough guide to the labour force in Khayelitsha/Mitchell's Plain with a particular focus on unemployment. The task is partly conceptual (a discussion is provided on statistical norms for measuring unemployment) and partly empirical. Data is drawn from the 2000/2001 Khayelitsha Mitchell's Plain (KMP) survey, which was designed mainly to explore various dimensions of labour market attachment amongst African and coloured people in Cape Town. This survey covered the magisterial district of Mitchell's Plain which includes the African townships of Khayelitsha, Gugulethu and Langa; it is not a representative sample of the Cape Town metropolitan area but rather of working class (predominantly African and coloured) Cape Town. In the discussion that follows, reference is made to the questionnaire. The Stata 'do file's (which generated the results) are available on request. Part 1 of the paper outlines the standard labour force approach to labour statistics and points to areas where standard definitions can usefully be extended or supplemented. Part 2 continues the discussion, but with reference to employment and unemployment in KMP. A distinction is drawn between the strict and broad definitions of unemployment and an intermediate definition of unemployment (which includes active job seekers and those seeking jobs exclusively through social networks) is introduced. Part 3 examines the nonlabour- force participants. Part 4 expands the scope of the labour force by adjusting some of the statistical requirements used in earlier approaches. Using this expanded approach, Part 5 continues the exploration of different dimensions of unemployment.

Income inequality after apartheid

This paper investigates changes in and patterns of income inequality in South Africa during the post-apartheid period 1994 to 2004. While findings show a rapidly growing high-income African population (a trend that began before 1994 and continued thereafter) as well as rising real wages for workers in formal employment, overall levels of income inequality have not been declining This is due to rising unemployment and a small informal sector that have therefore left unchanged South Africa's high level of income inequality. If anything, overall inequality has worsened. Inter-racial inequality has decreased while intra-racial inequality has increased. Opportunities have improved for some African people in South Africa, but not for all: a lack of human and social capital leaves many with little chance of rising out of poverty; AIDS-related mortality and morbidity are likely to exacerbate stratification and further increase inequality.

Model studies of fluctuations in the background for jets in heavy ion collisions

Jets produced in high energy heavy ion collisions are quenched by the production of the quark gluon plasma. Measurements of these jets are influenced by the methods used to suppress and subtract the large, fluctuating background and the assumptions inherent in these methods. We compare the measurements of the background in Pb+Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV by the ALICE collaboration to calculations in TennGen (a data-driven random background generator) and PYTHIA Angantyr. The standard deviation of the energy in random cones in TennGen is approximately in agreement with the form predicted in the ALICE paper, with deviations of 1-6 $\%$. The standard deviation of energy in random cones in Angantyr exceeds the same predictions by approximately 40 $\%$. Deviations in both models can be explained by the assumption that the single particle $d^2N/dydp_T$ is a Gamma distribution in the derivation of the prediction. This indicates that model comparisons are potentially sensitive to the treatment of the background

The quest for healing in South Africa's age of AIDS

Highly Active Antiretroviral Therapy (HAART) is the most effective means of extending the lives of people living with AIDS – yet only 25% of those in South Africa estimated to need it are receiving HAART. Those who cannot access HAART (or choose not to take it) may opt to use ‘traditional’ healing instead. Some people will do both. This article reviews the emerging South African literature exploring the interface between biomedical and traditional healing in this age of AIDS. It includes a discussion of recent relevant biographies and books. Particular attention is paid to the contrasting experiences of Edwin Cameron who took HAART and continues to live a productive life, and Fana Khaba, who rejected HAART in favour of untested substances. The paper notes how the diagnosis of AIDS as being caused by witchcraft may have psychological benefits (it shifts blame and responsibility to others) it can also exacerbate social tensions and undermine the health of those living with AIDS. It is argued that the state has an obligation to provide information to AIDS patients about the best scientifically tested medications

Di-hadron correlations at RHIC

Di-hadron correlations have been used to study jets at RHIC and have yielded rich insight into the properties of the medium. Studies show that the near-side peak of high-pT triggered correlations can be decomposed into two parts, a jet-like correlation and the ridge. The jet-like correlation is narrow in both azimuth and pseudorapidity and has properties consistent with vacuum fragmentation, while the ridge is narrow in azimuth but broad in pseudorapidity and roughly independent of pseudorapidity. The energy, system, and particle composition of the jet-like correlation and the ridge are discussed. Data indicate that the jet-like correlation is dominantly produced by vacuum fragmentation. Attempts have been made to explain the production of the ridge component as coming from recombination, momentum kicks, and QCD magnetic fields. However, few models have attempted to quantitatively calculate the characteristics of the ridge. The wealth of data should help distinguish models for the production mechanism of the ridge. Implications for studies of the jet-like correlation and the ridge at the LHC are discussed.Comment: 8 figures, proceedings from the 2010 International Workshop on the Interplay between soft and hard interactions, submitted to Il Nuovo Cimento