Jets and Prompt Photons in Photoproduction at ZEUS

In the ZEUS experiment at HERA, photoproduction processes have been studied for photon-proton centre-of-mass energies in the range 100 < W_gamma p < 300 GeV and jet transverse energies extending to E_T^jet ~ 70 GeV. The data contribute to our understanding of QCD dynamics, and also provide new constraints on the photon's parton density.Comment: 7 pages, 12 figures, talk given at ICHEP'98, writeup also available at http://ppewww.ph.gla.ac.uk/preprints/98/05

Rapidity Gaps in Hard Photoproduction

Recent results obtained from studies of diffractive processes in hard photoproduction performed by the ZEUS collaboration using data delivered by HERA in 1993 and 1994 are presented. In particular, we have found that $(7 \pm 3)$\% of events with two jets at a pseudorapidity interval of 3.5 to 4 are inconsistent with a non-diffractive production mechanism. These events may be interpreted as arising due to the exchange of a colour singlet object of negative squared invariant mass ($-t$) around 40~GeV$^2$. We have also probed the structure of the exchanged colour singlet object in low--$t$ diffractive scattering. By comparing the results from photoproduction and electroproduction processes we find that between 30\% and 80\% of the momentum of the exchanged colour singlet object which is carried by partons is due to hard gluons.Comment: 13 pages. 13 postscript figures + 1 postscript preprint logo + 1 LaTeX file. Files tarred, gzipped and uuencoded into 1 file. Also available at http://ppewww.ph.gla.ac.uk/preprints/96/03

Colour Coherence in Photon Induced Reactions

Colour coherence in hard photoproduction is considered using the Monte Carlo event generators PYTHIA and HERWIG. Significant effects in the parton shower are found using multijet observables for direct and resolved photon induced reactions. The particle flow in the interjet region of direct processes shows a strong influence of string fragmentation effects.Comment: 6 pages, LaTeX, 6 eps figures included, to appear in the proceedings of the workshop "Future Physics at HERA

Developing Scenarios for Product Longevity and Sufficiency

This paper explores the narrative of peoples’ relationships with products as a window on understanding the types of innovation that may inform a culture of sufficiency. The work forms part of the 'Business as Unusual: Designing Products with Consumers in the Loop' [BaU] project, funded as part of the UK EPSRC-ESRC RECODE network (RECODE, 2016) that aims to explore the potential of re-distributed manufacturing (RdM) in a context of sustainability. This element of the project employed interviews, mapping and workshops as methods to investigate the relationship between people and products across the product lifecycle. A focus on product longevity and specifically the people-product interactions is captured in conversations around product maintenance and repair. In exploring ideas of ‘broken’ we found different characteristics of, and motivations for, repair. Mapping these and other product-people interactions across the product lifecycle indicated where current activity is, who owns such activity (i.e. organisation or individual) and where gaps in interactions occur. These issues were explored further in a workshop which grouped participants to look at products from the perspective of one of four scenarios; each scenario represented either short or long product lifespans and different types of people engagement in the design process. The findings help give shape to new scenarios for designing sufficiency-based social models of material flows

Rapidity Gaps Between Jets

An excess of events with a rapidity gap between jets, over what would be expected from non-diffractive processes, has been observed at HERA. A process based on a perturbative QCD calculation of colour singlet exchange has been added to HERWIG. With this addition, HERWIG is able to describe the number of events with a gap between jets over the number without a gap. This gap fraction is predicted to rise at large rapidity intervals between jets which would only be visible if the detector coverage were increased.Comment: 5 pages including 3 figures. To appear in the conference proceedings of the Workshop "Future Physics at HERA

Simulation of the channelling of ions from MeV C60 in crystalline solids

Simulations were performed describing the motion and breakup of energetic C60 ions interacting with crystalline targets. A hybrid algorithm was used that employs a binary collision model for the scattering of the carbon ions by the atoms of the solid, and molecular dynamics for the Coulomb interactions of the 60 carbon ions with one another. For the case of yttrium iron garnet (YIG), directions such as [1 1 0], [1 0 0], [0 1 0] and [0 0 1] demonstrate channelling for a large fraction of the C ions. For directions such as [1 1 1], [2 1 1] and [7 5 3] the trajectories show no more channelling than for random directions. The effects of tilt, shielding and wake-field interactions were investigated for YIG and α-quartz

A landscape of repair

This paper reports on EPSRC-funded research that explores the role of repair in creating new models of sustainable business. In the lifecycle stage of repair we explore what 'broken' means and uncover the nature of local and dispersed repair activities. This in turn allows us to better understand how the relationship between products and people can help shape new modes of consumption. Therefore, narratives of repair are collected to identify diverse people-product interactions and illustrate the different characteristics of, and motivations for, repair. The paper proposes that mapping the different product-people interactions across the product lifecycle, particularly at the stage of fragile-functionality (performance or function failure, emotional disengagement, superseded technology) is important in understanding the potential for enduring products and their repair. Building a landscape of repair creates new opportunities for manufacture and for slowing resource loops across product lifetimes, which together provide a framework for a sufficiency-based model of production and consumption

Simulations of a Scintillator Compton Gamma Imager for Safety and Security

We are designing an all-scintillator Compton gamma imager for use in security investigations and remediation actions involving radioactive threat material. To satisfy requirements for a rugged and portable instrument, we have chosen solid scintillator for the active volumes of both the scatter and absorber detectors. Using the BEAMnrc/EGSnrc Monte Carlo simulation package, we have constructed models using four different materials for the scatter detector: LaBr_3, NaI, CaF_2 and PVT. We have compared the detector performances using angular resolution, efficiency, and image resolution. We find that while PVT provides worse performance than that of the detectors based entirely on inorganic scintillators, all of the materials investigated for the scatter detector have the potential to provide performance adequate for our purposes.Comment: Revised text and figures, Presented at SORMA West 2008, Published in IEEE Transactions on Nuclear Scienc