The equivalence theorem and the Bethe-Salpeter equation

We solve the Bethe-Salpeter equation for two-particle scattering in a field-theoretical model using two lagrangians related by a field transformation. The kernel of the equation consists of the sum of all tree-level diagrams for each lagrangian. The solutions differ even if all four external particles are put on the mass shell, which implies that observables calculated by solving the Bethe-Salpeter equation depend on the representation of the theory. We point out that this violation of the equivalence theorem has a simple explanation and should be expected for any Bethe-Salpeter equation with a tree-level kernel. Implications for dynamical models of hadronic interactions are discussed.Comment: 10 pages, 4 figures, using REVTeX. Fig. 2 corrected, results unchanged, to be published in Phys. Lett.

Interference Effects in Relativistic Deuteron Electrodisintegration

We extend the relativistic plane--wave impulse approximation formalism to incorporate a specific class of relativistic interference effects for use in describing inclusive electrodisintegration of $^2$H. The role of these ``exchange'' terms for the various response functions accessible in parity--conserving and --violating inclusive processes is investigated and shown, especially for the latter, to have important consequences for experiment. An extension to a simple quasi--deuteron model is also considered.Comment: 28 pages (latex), 15 figures available upon request, TRI-PP-93-101 and MIT-CTP#224

Reconnecting Downtown to the Riverfront. Springfield, MA. Senior Urban Design Studio,

The work of this urban design studio illustrates visions for the revitalization of Springfield’s downtown riverfront through landscape architecture facing the challenges of a dissecting I-91 highway corridor. Re-Connecting people to the riverfront capi­talizes on the great Connecticut River and will revitalize the city to attract and engage residents and visitors alike. The proposals foster creating spaces in Riverfront Park for multiple activities such as recreation, places for arts and culture, education and enhancement of the River’s ecology. They further promote pedestrian/bicycle arteries to and along the riverfront that are embedded in a livable, mixed-use, diverse neighborhood. The work explores a community service learning strategy within the framework of an urban design studio with the goal of revitalizing the city of Springfield, Massachusetts, through sustainable design, planning, and engagement with the community. This studio produced six tangible visions and are based on three scenarios; 1) Scenario 1keeps the highway I-91 on an elevated level above ground; 2) Scenario 2 lowers I-91 down to an on-ground level; 3) Scenario 3 lowers I-91 underground as a completely or partially covered corridor. All six design visions share the following recommendations and principles to create a livable and sustainable city that engages the riverfront as a place for people and as a landscape that will be crucial for a great future of Springfield’s downtown: Creating spaces in Riverfront Park that are more centered and generous for multiple activities; add floodplains to improve the ecology of the River and educate the public. Creating pedestrian/bicycle arteries from Main Street to the riverfront. Elimination of on- and off- ramps within the core of downtown to prioritize pedestrian movement to the Connecticut River and reduce noise. Eliminate parking structures underneath the highway for visibility of the River. Redesigning East and West Columbus Avenue as pedestrian- and bicycle-friendly corridors through a road diet and speed reduction. Foster mixed-use development along East Columbus Avenue at the edge of the South End Neighborhood. Connect the Connecticut River Walk and Bikeway to Forest Park in the south

Green Infrastructure for Framingham, Massachusetts: Greenway Planning and Cultural Landscape Design

The senior undergraduate, Bachelors of Landscape Architecture studio at the University of Massachusetts, Amherst developed a town-wide greenway plan for the Town of Framingham’s Department of Community and Economic Development. This conceptual plan connects the town’s natural, cultural, and recreational resources through a network of pedestrian and bike trails. This plan also seeks to connect the diverse neighborhoods within the Town to these resources and provide alternative means of local residents to access jobs, schools, and retail centers. The greenway plan builds on Framingham’s Open Space and Recreation Plan (2013), which identified the need for a regional greenway system to link the town to the many local and regional recreational, cultural, ecological, and economic resources. This capstone planning and design studio began with an analysis and assessment of the Town of Framingham’s natural, recreational, cultural, and transportation/land use resources. Teams of students developed alternative greenway plans for the town and region, respectively. These plans were synthesized halfway through the class to produce the composite greenway plan shown in this report. For the second half of the class, individual students developed neighborhood and site specific greenway and park designs for key linkages within the greenway network in the rural northeast section of Framingham, industrial village of Saxonville, historic Framingham Center, the Tech Park, and downtown Framingham. These detailed designs form the body of this report

Virtual-pion and two-photon production in pp scattering

Two-photon production in pp scattering is proposed as a means of studying virtual-pion emission. Such a process is complementary to real-pion emission in pp scattering. The virtual-pion signal is embedded in a background of double-photon bremsstrahlung. We have developed a model to describe this background process and show that in certain parts of phase space the virtual-pion signal gives significant contribution. In addition, through interference with the two-photon bremsstrahlung background, one can determine the relative phase of the virtual-pion process

Induced pseudoscalar coupling of the proton weak interaction

The induced pseudoscalar coupling $g_p$ is the least well known of the weak coupling constants of the proton's charged--current interaction. Its size is dictated by chiral symmetry arguments, and its measurement represents an important test of quantum chromodynamics at low energies. During the past decade a large body of new data relevant to the coupling $g_p$ has been accumulated. This data includes measurements of radiative and non radiative muon capture on targets ranging from hydrogen and few--nucleon systems to complex nuclei. Herein the authors review the theoretical underpinnings of $g_p$, the experimental studies of $g_p$, and the procedures and uncertainties in extracting the coupling from data. Current puzzles are highlighted and future opportunities are discussed.Comment: 58 pages, Latex, Revtex4, prepared for Reviews of Modern Physic

Close-to-threshold Meson Production in Hadronic Interactions

Studies of meson production at threshold in the hadron--hadron interaction began in the fifties when sufficient energies of accelerated protons were available. A strong interdependence between developments in accelerator physics, detector performance and theoretical understanding led to a unique vivid field of physics. Early experiments performed with bubble chambers revealed already typical ingredients of threshold studies, which were superseded by more complete meson production investigations at the nucleon beam facilities TRIUMF, LAMPF, PSI, LEAR and SATURNE. Currently, with the advent of the new cooler rings as IUCF, CELSIUS and COSY the field is entering a new domain of precision and the next step of further progress. The analysis of this new data in the short range limit permits a more fundamental consideration and a quantitative comparison of the production processes for different mesons in the few--body final states. The interpretation of the data take advantage of the fact that production reactions close-to-threshold are characterized by only a few degrees of freedom between a well defined combination of initial and exit channels. Deviations from predictions of phase-space controlled one-meson-exchange models are indications of new and exciting physics. Precision data on differential cross sections, isospin and spin observables -- partly but by no means adequately available -- are presently turning up on the horizon. There is work for the next years and excitement of the physics expected. Here we try to give a brief and at the same time comprehensive overview of this field of hadronic threshold production studies.Comment: 100 pages, Review article to be published in Prog. Part. Nucl. Phys. Vol. 49, issue 1 (2002