2156470
Performance reach of the "phase 1" LHC collimation system
State-of-the-art tracking tools have been developed for detailed LHC collimation and beam loss studies. This includes full chromatic treatment of both beam lines and error models. This paper reviews the main results on the performance reach of the multi-stage LHC collimation system that is being installed in the LHC. Limitations on the allowed proton loss rates and the stored intensity can be derived from the comparison of local losses with estimated quench limits for the superconducting magnets. The origins of the cleaning-related performance limitations are presented and possible improvements are discussed.
55312556
Performance test of a micro-pattern stereo detector with two gas electron multipliers
Abstract We report on the performance of a large micro-pattern detector with two gas electron multiplier foils and a two-layer readout structure at ground potential. The two readout layers each have a 406 μm pitch and cross at an effective angle of 6.7°. This structure allows for two orthogonal coordinates to be determined. Using a muon beam at CERN together with a silicon tracking system, the position resolutions of the two coordinates are measured to be 50 μm and 1 mm respectively (1 standard deviation). The muon detection efficiency for the two-dimensional space points reaches 96%. The detector was found to be well operational over a wide range in the settings of the different electrical fields.
32656642
Beam loss response measurements with a LHC prototype collimator in the SPS
Beam tests with a large hadron collider (LHC) prototype collimator were performed at the super proton synchrotron (SPS) in autumn 2006. Applying a new collimator control system many new beam measurements were performed. This contribution presents results on collimator- induced beam loss measurements and their applications to beam-based alignment of collimators and measurements of the beam size and position. Interesting features of the recorded beam loss signals are illustrated and possible impacts for LHC operation are discussed.
55572949
CRITICAL HALO LOSS LOCATIONS IN THE LHC
Results of simulations with all movable elements of the LHC collimation system [1] are discussed for various operation modes. Compared to previous results, the placing of additional collimators reduced the beam losses by a factor 10 in the ideal machine case, i.e. nominal collimators settings for both 450 GeV and 7 TeV beam energies. First results for Beam 2 are also reviewed. The sensitivity of the system to free orbit oscillations is addressed. These results show that it is sufficient to use a limited number of beam loss monitors (BLMs) for the setup and optimization of the LHC Collimation System.
53997166
Robustness test of a system of MSGC+GEM detectors at the cyclotron facility of the Paul Scherrer Institute
Abstract A system of detector modules consisting of a large size Gas Electron Multiplier (GEM), coupled to Micro Strip Gas Counters (MSGC), has been exposed to a pion beam at the Paul Scherrer Institute Cyclotron facility. As part of a CMS tracker milestone, the aim of this test was to investigate the robustness of such detectors when exposed to experimental conditions close to what is expected at the Large Hadron Collider (LHC) of CERN. Eighteen detector modules have been operated at voltage settings corresponding to 98% detection efficiency for Minimum Ionizing Particles during a period of 5 weeks. Sparking rates and strip losses have been monitored throughout the exposure. An operation margin of at least a factor of three with respect to the required gas gain has been demonstrated.
116150310
Dips in the UHE cosmic ray neutrino spectrum from absorption by dark matter
111279673
Beam-loss-induced electrical stress test on CMS Silicon Strip Modules
Abstract Based on simulated LHC beam loss scenarios, fully depleted CMS silicon tracker modules and sensors were exposed to 42 ns -long beam spills of approximately 1011 protons per spill at the PS at CERN. The ionisation dose was sufficient to short circuit the silicon sensors. The dynamic behaviour of bias voltage, leakage currents and voltages over coupling capacitors were monitored during the impact. Results of pre- and post-qualification as well as the dynamic behaviour are shown.
122276548
COSMIC NEUTRINO PHYSICS AND ASTROPHYSICS
Over the next decade or two, neutrino telescopes will map out the neutrino sky, analogous to the way the electromagnetic sky has been mapped for centuries. Like light and unlike cosmic-rays, the neutrinos will point back to their sources. Unlike light, the neutrinos are not attenuated at high energies and so will allow us to see farther into space, and deeper into sources. We illustrate with specific examples the promise which neutrino astronomy at energies from a TeV to a ZeV holds to study astrophysics and particle physics.
120897439
Production and decay of minimal SUSY Higgs bosons at LEP/SLC and beyond
Abstract We present the rates for tree-level production and decay of Higgs bosons in the pure Higgs and gauge-Higgs sectors in the minimal N = 1 supergravity models. Two Higgs masses are sufficient to determine the SUSY parameters in these processes. With appropriate variables defined in terms of the two Higgs masses and relevant center-of-mass energies, we are able to explore the supersymmetric parameter space available to each process by plotting iso-rate contours on a bounded square. Recent limits from LEP are incorporated into our analysis. These limits exclude regions inside or outside particular contours, and impact on the reach of present and future higher-energy accelerators. A single positive experimental result for any one process would in principle determine the point for the square of every other process, which may or may not be physical.
15588683
GENERALIZED NEUTRINO MIXING FROM THE ATMOSPHERIC ANOMALY
Abstract We determine the neutrino mixing and mass parameters that are allowed by the Super-Kamiokande atmospheric neutrino data in a three-neutrino model with one mass-squared difference contributing to the oscillations. We find that although ν μ → ν τ oscillations are favored, ν μ → ν e oscillations with amplitude as large as 0.18 are allowed even after accounting for the limit from the CHOOZ reactor experiment. The range of allowed parameters permit observable ν μ ↔ ν e and ν e → ν τ oscillations in future long-baseline experiments.