Spin Dependent Drell Yan in QCD to O(αs2)O(\alpha_s^2) (I). (The Non-Singlet Sector)

A study of the order $\alpha_s^2$ corrections to the Drell Yan (non-singlet) cross section for incoming states of arbitrary longitudinal helicities is presented. The study is performed in the case of the transverse momentum distributions, $(q_T)$, of the lepton pair and extends the calculation of Ellis Martinelli and Petronzio (EMP) to the polarized case. We use the $\bar{MS}$ scheme and the t'Hooft-Veltman regularization for the helicity projectors. From our results one can obtain the bulk of the totally inclusive NNLO cross section for the production of a Drell Yan pair in the non-singlet sector by a simple integration over the heavy photon momentum. We show that in the $\bar{MS}$ helicity is not conserved, unless a finite renormalization is done to reenter into a physical scheme ($\bar{MS}_p$). This aspect of the calculation follows the same trend as in polarized production of single and double photon to $O(\alpha_s^2)$. In the unpolarized limit we reproduce all the results of EMP.Comment: 39 pages, 7 figures (included

Development of virus resistant transgenic papayas expressing the coat protein gene from a Brazilian isolate of Papaya ringspot virus.

Translatable and nontranslatable versions of the coat protein (cp) gene of a Papaya ringspot virus (PRSV) isolate collected in the state of Bahia, Brazil, were engineered for expression in Sunrise and Sunset Solo varieties of papaya (Carica papaya). The biolistic system was used to transform secondary somatic embryo cultures derived from immature zygotic embryos. Fifty-four transgenic lines, 26 translatable and 28 nontranslatable gene versions, were regenerated, with a transformation efficiency of 2.7%. Inoculation of cloned RO plants with PRSV BR, PRSV HA or PRSV TH, Brazilian, Hawaiian and Thai isolates, respectively, revealed !ines with mono-, double-, and triple-resistance. After molecular analysis and a pre!iminary agronomic evaluation, 13 RI and R2 populations were incorporated into the papaya-breeding program at Embrapa Cassava and Tropical Fruits, in Cruz das Almas, Bahia, Brazil. Additional keywords: Carica papaya, potyvirus, resistance, breeding, virus. Desenvolvimento de mamoeiros transgênicos resistentes a vírus expressando o gene da capa protéica de um isolado brasileiro de Papaya ringspot vírus Versões traduzíveis e não traduzíveis do gene da capa protéica (cp) de um isolado de Papaya ringspot virus (PRSV) coletado no Estado da Bahia, Brasil, foram produzidas para expressão nas variedades Sunrise e Sunset Solo de mamoeiro (Carica papaya). O sistema de biobalística foi utilizado para transformar embriões somáticos secundários derivados de embriões zigóticos imaturos. Cinqüenta e quatro linhas transgênicas, sendo 26 contendo versões traduzíveis e 28 contendo versões não traduzíveis do gene cp foram regeneradas, o que resultou em 2,7% de eficiência de transformação, quando considerado o número de linhas transgênicas obtidas por embrião zigótico imaturo excisado. Desafios de plantas RO com PRSV BR, PRSV HA ou PRSV TH, respectivamente isolado brasileiro, havaiano e tailandês, revelaram linhas com resistência a um, dois e três isolados de PRSV. Após análises moleculares e avaliação agronômica preliminar, 13 populações RI e R2 de mamoeiros transgênicos foram incorporadas ao programa de melhoramento genético da Embrapa Mandioca e Fruticultura, em Cruz das Almas, Bahia, Brasil. Palavras-chave adicionais: Carica papaya, potyvirus, resistência, melhoramento, PRSV

Using differential equations to compute two-loop box integrals

The calculation of exclusive observables beyond the one-loop level requires elaborate techniques for the computation of multi-leg two-loop integrals. We discuss how the large number of different integrals appearing in actual two-loop calculations can be reduced to a small number of master integrals. An efficient method to compute these master integrals is to derive and solve differential equations in the external invariants for them. As an application of the differential equation method, we compute the ${\cal O}(\epsilon)$-term of a particular combination of on-shell massless planar double box integrals, which appears in the tensor reduction of $2 \to 2$ scattering amplitudes at two loops.Comment: 5 pages, LaTeX, uses espcrc2.sty; presented at Loops and Legs in Quantum Field Theory, April 2000, Bastei, German

Absolute calibration of GafChromic film for very high flux laser driven ion beams.

We report on the calibration of GafChromic HD-v2 radiochromic film in the extremely high dose regime up to 100 kGy together with very high dose rates up to 7 × 1011 Gy/s. The absolute calibration was done with nanosecond ion bunches at the Neutralized Drift Compression Experiment II particle accelerator at Lawrence Berkeley National Laboratory (LBNL) and covers a broad dose dynamic range over three orders of magnitude. We then applied the resulting calibration curve to calibrate a laser driven ion experiment performed on the BELLA petawatt laser facility at LBNL. Here, we reconstructed the spatial and energy resolved distributions of the laser-accelerated proton beams. The resulting proton distribution is in fair agreement with the spectrum that was measured with a Thomson spectrometer in combination with a microchannel plate detector

Research for policy influence : a history of IDRC intent

Part of the collection of government and miscellaneous documents relating to the history of IDRC.This paper tells the story of how the Centre's intent on linking research and policy processes has evolved over the years. There has been a persistent concern with the use of research over three decades of IDRC’s history. The task of refining a corporate strategy to foster research for policy change, and especially of putting it into practice, remains a work in progress. This study is based on analysis of IDRC planning documents, reports, internal papers, evaluations and reviews, as well as selected Board minutes. External documents were also consulted to help provide context

Spin Dependent Drell-Yan beyond Leading Order: Non-Singlet Virtual corrections to O(αs2)O(\alpha_s^2)

We present parton-level analytical results for the next-to-leading order non-singlet virtual and real corrections to the Drell-Yan differential cross-section. The dependence of the differential cross section on the helicity of the initial state partons is shown explicitly (the spins of the final state partons are summed). The calculation is implemented in dimensional regularization within the $\bar{MS}$ scheme and with the t'Hooft Veltman prescriptions for the n-dimensional $\gamma_5$. Both the polarized initial state and the unpolarized cross sections can be obtained from our result. Our unpolarized cross section agrees with the previous result of Ellis, Martinelli and Petronzio in the non-singlet sector.Comment: 12 pages, 7 figures, one chapter added, change in figure

The tensor reduction and master integrals of the two-loop massless crossed box with light-like legs

The class of the two-loop massless crossed boxes, with light-like external legs, is the final unresolved issue in the program of computing the scattering amplitudes of 2 --> 2 massless particles at next-to-next-to-leading order. In this paper, we describe an algorithm for the tensor reduction of such diagrams. After connecting tensor integrals to scalar ones with arbitrary powers of propagators in higher dimensions, we derive recurrence relations from integration-by-parts and Lorentz-invariance identities, that allow us to write the scalar integrals as a combination of two master crossed boxes plus simpler-topology diagrams. We derive the system of differential equations that the two master integrals satisfy using two different methods, and we use one of these equations to express the second master integral as a function of the first one, already known in the literature. We then give the analytic expansion of the second master integral as a function of epsilon=(4-D)/2, where D is the space-time dimension, up to order O(epsilon^0).Comment: 30 pages, 5 figure

Using story-based methodologies to explore physics identities:How do moments add up to a life in physics?

[This paper is part of the Focused Collection on Qualitative Methods in PER: A Critical Examination.] This article details methodologies employed to enable sharing and coconstructing the stories of three women’s lives in physics. The first case explores the usefulness of timeline interviewing, where participants narrate episodes that are coconstructed with the researcher as meaningful over time. We illustrate this method in the case of a mature student in Sweden from a working-class background who shared moments that added up to a life outside of physics and then a sharp turn into physics later in life. The second case explores life-history interviewing using a narrative-inquiry approach and deep relationship building which enabled the coconstruction of stories of experiences over time. These moments are coconstructed with the researcher and analyzed using an intersectionality lens to yield a story depicting the transnational experiences of a woman of color moving across various European contexts into the North American physics context. The final case is of a first-generation Canadian woman of color who shared her navigations of in and out of school physics via a method known as the “Rivers of Life.” Using this method, the participant narrates their experiences with physics as a river, using metaphorical tools like rafts, rocks, rapids, tributaries to discuss various moments described as twists and turns over time that together amount to a life in physics. We discuss the value of different approaches to coconstructing narratives with participants and, in particular, the need for this kind of research in physics contexts

An easy way to solve two-loop vertex integrals

Negative dimensional integration is a step further dimensional regularization ideas. In this approach, based on the principle of analytic continuation, Feynman integrals are polynomial ones and for this reason very simple to handle, contrary to the usual parametric ones. The result of the integral worked out in $D<0$ must be analytically continued again --- of course --- to real physical world, $D>0$, and this step presents no difficulties. We consider four two-loop three-point vertex diagrams with arbitrary exponents of propagators and dimension. These original results give the correct well-known particular cases where the exponents of propagators are equal to unity.Comment: 13 pages, LaTeX, 4 figures, misprints correcte