Beam Extinction Monitor Design Optimization And Performance Studies For The Mu2e Experiment

The proposed Mu2e experiment at the future muon campus at the Fermi National Accelerator Laboratory is designed to probe for new physics (in particular, muon to electron conversion) at the intensity frontier. Mu2e is designed to observe and measure charged lepton flavor violation (CLFV) via muon capture (u ̄ + N(Z) [arrow right] e ̄+ N(Z)) at an event sensitivity of approximately 5.4 x 10−17 on a 90% confidence interval. Achieving this level of sensitivity necessitates a beam extinction monitor to detect secondary particles indicative of out of time (OoT) beam protons. If the beam extinction exceeds the design value of 10−10, prompt background levels will not be adequately suppressed to achieve the desired event sensitivity. A series of Monte Carlo simulations were performed to study the extinction monitor's ability to record OoT events as well as its sensitivity to misalignment during the construction of the experiment. Additionally, various extinction monitor geometry changes were implemented within Geant4 to measure and minimize the effects of damaging radiation on crucial detector elements. Independent analysis of these simulations indicate the nominal extinction monitor design meets the Mu2e experiment's requirements. Minimal design changes substantially mitigate the effects of harmful radiation damage and provide for a more robust detector-maximizing the extinction monitor's lifetime with hardware replacement on the order of approximately once a year, while minimizing operational cost and experiment downtime.

The Mu2e Experiment at Fermilab will search for the conversion of a muon to an electron in the field of an atomic nucleus with unprecedented sensitivity. The experiment requires a beam consisting of proton bunches approximately 200ns FW long, separated by 1.7 microseconds, with no out-of-time protons at the 10−10 fractional level. The verification of this level of extinction is very challenging. The proposed technique uses a special purpose spectrometer which will observe particles scattered from the production target of the experiment. The acceptance will be limited such that there will be no saturation effects from the in-time beam. The precise level and profile of the out-of-time beam can then be built up statistically, by integrating over many bunches.

A muon-to-electron conversion experiment at Fermilab, Mu2e, is being designed to probe for new physics beyond the standard model at mass scales up to 104 TeV. For this experiment, the advance in experimental sensitivity will be four orders of magnitude when compared to existing data on charged lepton flavor violation. The muon beam will be produced by delivering a proton beam contained in short 100-ns bunches onto a muon production target, with an inter-bunch separation of about 1700 ns. A critical requirement of the experiment is to ensure a low level of background at the muon detector consistent with the required sensitivity. To meet the sensitivity requirement, protons that reach the target between bunches must be suppressed by an enormous factor, so that an extinction factor, defined as a number of background protons between main bunches per proton in such a bunch, should not exceed 10−9. This paper describes the advanced beam optics and results of numerical modeling with STRUCT and MARS codes for a beam line with a collimation system that allows us to achieve the experimental extinction factor of one per billion.

For future experiments at the intensity frontier, precise and accurate knowledge of beam time structure will be critical to understanding backgrounds. The proposed Mu2e experiment will utilize ≈200 ns (FW) bunches of 3 x 107 protons at 8 GeV with a bunch-to-bunch period of 1695 ns. The out-of-bunch beam must be suppressed by a factor of 10−1° relative to in-bunch beam and continuously monitored. I propose a Cerenkov-based particle telescope to measure secondary production from beam interactions in a several tens of microns thick foil. Correlating timing information with beam passage will allow the determination of relative beam intensity to arbitrary precision given a sufficiently long integration time. The goal is to verify out-of-bunch extinction to the level 10−6 in the span of several seconds. This will allow near real-time monitoring of the initial extinction of the beam resonantly extracted from Fermilabs Debuncher before a system of AC dipoles and collimators, which will provide the final extinction. The effect on beam emittance is minimal, allowing the necessary continuous measurement. I will present the detector design and some concerns about bunch growth during the resonant extraction.

This volume contains the talks given at the above workshop which was devoted to discussing the newest developments in various models of electroweak symmetry breaking forming the basis of modern particle physics. It includes various aspects of Higgs physics and condensate models embodying dynamical symmetry breaking.

After a historical consideration of the types and evolution of accelerators the physics of particle beams is provided in detail. Topics dealt with comprise linear and nonlinear beam dynamics, collective phenomena in beams, and interactions of beams with the surroundings. The design and principles of synchrotrons, circular and linear colliders, and of linear accelerators are discussed next. Also technological aspects of accelerators (magnets, RF cavities, cryogenics, power supply, vacuum, beam instrumentation, injection and extraction) are reviewed, as well as accelerator operation (parameter control, beam feedback system, orbit correction, luminosity optimization). After introducing the largest accelerators and colliders of their times the application of accelerators and storage rings in industry, medicine, basic science, and energy research is discussed, including also synchrotron radiation sources and spallation sources. Finally, cosmic accelerators and an outlook for the future are given.

This volume is a collection of review articles on the most outstanding topics in heavy flavour physics. All the authors have made significant contributions to this field. The book reviews in detail the theoretical structure of heavy flavour physics within the Standard Model and its confrontation with existing experimental data.The physics of the top quark and of the Higgs play an important role in this volume. Beginning with radiative electroweak corrections and their impressive tests at LEP and hadron colliders, the book summarizes the present status of quark mixing, CP violation and rare decays. The dynamics of exclusive D- and B-meson decays, the τ-lepton physics and the newly discovered heavy quark symmetries are discussed in detail. The impact of strong interactions on weak decays is clearly visible in many articles. The physics of heavy flavours at LEP, HERA and hadron colliders constitutes an important part of the book. Another significant topic is the possible role of heavy flavours in the spontaneous symmetry breaking of gauge symmetries. Finally the most recent advances in lattice calculations of the properties of heavy flavours and the lattice studies of the dynamics of heavy flavours are presented.