Rotating Band Pion Production Targets for Muon Colliders and Neutrino Factories

An update is presented on a conceptual design for a pion production target station using a rotating cupronickel band and that was originally proposed for use at a muon collider facility with a 4 MW pulsed proton beam. After reviewing the salient design features and motivations for this target, ongoing studies are described that are attempting to benchmark the thermal stresses and radiation damage on the target band using data from the Fermilab antiproton source and other operating targets. Possible parameter optimizations and alternative technologies for the rotating band are surveyed, including discussion on the the various proton beam parameters that might be encountered for rotating band targets at either muon colliders or neutrino factories. Finally, an outline is proposed for a possible R&D path towards capability for the actual construction of rotating band pion production targets.Comment: 14 pages, 4 figures. Submitted to Proc. ICFA/ECFA Workshop on Neutrino Factories Based on Neutrino Storage Rings (NuFACT'99), Lyon, France, 5-9 July, 199

Parameter Sets for 10 TeV and 100 TeV Muon Colliders, and their Study at the HEMC'99 Workshop

A focal point for the HEMC'99 workshop was the evaluation of straw-man parameter sets for the acceleration and collider rings of muon colliders at center of mass energies of 10 TeV and 100 TeV. These self-consistent parameter sets are presented and discussed. The methods and assumptions used in their generation are described and motivations are given for the specific choices of parameter values. The assessment of the parameter sets during the workshop is then reviewed and the implications for the feasibility of many-TeV muon colliders are evaluated. Finally, a preview is given of plans for iterating on the parameter sets and, more generally, for future feasibility studies on many-TeV muon colliders.Comment: 20 pages, 2 figures. Submitted to Proc. HEMC'99 Workshop - Studies on Colliders and Collider Physics at the Highest Energies: Muon Colliders at 10 TeV to 100 TeV; Montauk, NY, September 27-October 1, 199

Mighty MURINEs: Neutrino Physics at Very High Energy Muon Colliders

An overview is given of the potential for neutrino physics studies through parasitic use of the intense high energy neutrino beams that would be produced at future many-TeV muon colliders. Neutrino experiments clearly cannot compete with the collider physics. Except at the very highest energy muon colliders, the main thrust of the neutrino physics program would be to improve on the measurements from preceding neutrino experiments at lower energy muon colliders, particularly in the fields of B physics, quark mixing and CP violation. Muon colliders at the 10 TeV energy scale might already produce of order 10^8 B hadrons per year in a favorable and unique enough experimental environment to have some analytical capabilities beyond any of the currently operating or proposed B factories. The most important of the quark mixing measurements at these energies might well be the improved measurements of the important CKM matrix elements |V_ub| and |V_cb| and, possibly, the first measurements of |V_td| in the process of flavor changing neutral current interactions involving a top quark loop. Muon colliders at the highest center-of-mass energies that have been conjectured, 100--1000 TeV, would produce neutrino beams for neutrino-nucleon interaction experiments with maximum center-of-mass energies from 300--1000 GeV. Such energies are comparable to the 314 GeV center-of-mass energy for electron-proton scattering at the HERA collider, but the luminosity would would be several orders of magnitude larger. This would potentially open up the possibility for high statistics studies of any exotic particles, such as leptoquarks, that might have been previously discovered at these energy scales.Comment: 23 pages, 7 figures. Submitted to Proc. HEMC'99 Workshop - Studies on Colliders and Collider Physics at the Highest Energies: Muon Colliders at 10 TeV to 100 TeV; Montauk, NY, September 27-October 1, 199

Prospects for Colliders and Collider Physics to the 1 PeV Energy Scale

A review is given of the prospects for future colliders and collider physics at the energy frontier. A proof-of-plausibility scenario is presented for maximizing our progress in elementary particle physics by extending the energy reach of hadron and lepton colliders as quickly and economically as might be technically and financially feasible. The scenario comprises 5 colliders beyond the LHC -- one each of e+e- and hadron colliders and three muon colliders -- and is able to hold to the historical rate of progress in the log-energy reach of hadron and lepton colliders, reaching the 1 PeV constituent mass scale by the early 2040's. The technical and fiscal requirements for the feasibility of the scenario are assessed and relevant long-term R&D projects are identified. Considerations of both cost and logistics seem to strongly favor housing most or all of the colliders in the scenario in a new world high energy physics laboratoryComment: 36 pages, 4 figures. Submitted to Proc. HEMC'99 Workshop - Studies on Colliders and Collider Physics at the Highest Energies: Muon Colliders at 10 TeV to 100 TeV; Montauk, NY, September 27-October 1, 199

Neutrino Radiation Challenges and Proposed Solutions for Many-TeV Muon Colliders

Neutrino radiation is expected to impose major design and siting constraints on many-TeV muon colliders. Previous predictions for radiation doses at TeV energy scales are briefly reviewed and then modified for extension to the many-TeV energy regime. The energy-cubed dependence of lower energy colliders is found to soften to an increase of slightly less than quadratic when averaged over the plane of the collider ring and slightly less than linear for the radiation hot spots downstream from straight sections in the collider ring. Despite this, the numerical values are judged to be sufficiently high that any many-TeV muon colliders will likely be constructed on large isolated sites specifically chosen to minimize or eliminate human exposure to the neutrino radiation. It is pointed out that such sites would be of an appropriate size scale to also house future proton-proton and electron-positron colliders at the high energy frontier, which naturally leads to conjecture on the possibilities for a new world laboratory for high energy physics. Radiation dose predictions are also presented for the speculative possibility of linear muon colliders. These have greatly reduced radiation constraints relative to circular muon colliders because radiation is only emitted in two pencil beams directed along the axes of the opposing linacs.Comment: 16 pages, 8 figures. Submitted to Proc. HEMC'99 Workshop - Studies on Colliders and Collider Physics at the Highest Energies: Muon Colliders at 10 TeV to 100 TeV; Montauk, NY, September 27-October 1, 199

Further Studies on the Prospects for Many-TeV Muon Colliders

New self-consistent parameter sets are presented and discussed for muon collider rings at center-of-mass energies of 10, 30 and 100 TeV. All three parameter sets attain luminosities of 3 x 10^35 /cm^2/s. The parameter sets benefit from new insights gained at the HEMC'99 workshop that considered the feasibility of many-TeV muon colliders.Comment: 3 pages, no figures. Submitted to Proc. EPAC 200

Preparation of high purity copper fluoride by fluorinating copper hydroxyfluoride

Copper fluoride containing no more than 50 ppm of any contaminating element was prepared by the fluorination of copper hydroxyfluoride. The impurity content was obtained by spark source mass spectrometry. High purity copper fluoride is needed as a cathode material for high energy density batteries

Copper emissions from a high volume air sampler

High volume air samplers (hi vols) are described which utilize a brush-type electric motor to power the fans used for pulling air through the filter. Anomalously high copper values were attributed to removal of copper from the commutator into the air stream due to arcing of the brushes and recirculation through the filter. Duplicate hi vols were set up under three operating conditions: (1) unmodified; (2) gasketed to prevent internal recirculation; and (3) gasketed and provided with a pipe to transport the motor exhaust some 20 feet away. The results of 5 days' operation demonstrate that hi vols can suddenly start emitting increased amounts of copper with no discernible operational indication, and that recirculation and capture on the filter can take place. Copper levels found with hi vols whose exhaust was discharged at a distance downwind were among the lowest found, and apparently provides a satisfactory solution to copper contamination

Are the causes of bank distress changing? can researchers keep up?

Since 1990, the banking sector has experienced enormous legislative, technological and financial changes, yet research into the causes of bank distress has slowed. One consequence is that current supervisory surveillance models may no longer accurately represent the banking environment. After reviewing the history of these models, we provide empirical evidence that the characteristics of failing banks has changed in the last ten years and argue that the time is right for new research employing new empirical techniques. In particular, dynamic models that utilize forward-looking variables and address various types of bank risk individually are promising lines of inquiry. Supervisory agencies have begun to move in these directions, and we describe several examples of this new generation of early-warning models that are not yet widely known among academic banking economists.Bank failures ; Bank supervision

Importance Tempering

Simulated tempering (ST) is an established Markov chain Monte Carlo (MCMC) method for sampling from a multimodal density $\pi(\theta)$. Typically, ST involves introducing an auxiliary variable $k$ taking values in a finite subset of $[0,1]$ and indexing a set of tempered distributions, say $\pi_k(\theta) \propto \pi(\theta)^k$. In this case, small values of $k$ encourage better mixing, but samples from $\pi$ are only obtained when the joint chain for $(\theta,k)$ reaches $k=1$. However, the entire chain can be used to estimate expectations under $\pi$ of functions of interest, provided that importance sampling (IS) weights are calculated. Unfortunately this method, which we call importance tempering (IT), can disappoint. This is partly because the most immediately obvious implementation is na\"ive and can lead to high variance estimators. We derive a new optimal method for combining multiple IS estimators and prove that the resulting estimator has a highly desirable property related to the notion of effective sample size. We briefly report on the success of the optimal combination in two modelling scenarios requiring reversible-jump MCMC, where the na\"ive approach fails.Comment: 16 pages, 2 tables, significantly shortened from version 4 in response to referee comments, to appear in Statistics and Computin