2759886
Construction and Performance of a Micro-Pattern Stereo Detector with Two Gas Electron Multipliers
Abstract The construction of a micro-pattern gas detector of dimensions 40×10 cm 2 is described. Two gas electron multiplier foils (GEM) provide the internal amplification stages. A two-layer readout structure was used, manufactured using the same technology as the GEM foils. The strips of each layer cross at an effective crossing angle of 6.7° and have a 406 μm pitch. The performance of the detector has been evaluated in a muon beam at CERN using a silicon telescope as reference system. The position resolutions of two orthogonal coordinates are measured to be 50 μm and 1 mm , respectively. The muon detection efficiency for two-dimensional space points reaches 96%.
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.
2362172
LHC collimation system hardware commissioning
The stored energy and intensity of the LHC beam exceed the damage level of the machine and the quench level of the magnets by far. Therefore a robust and reliable collimation system is required which prevents the quenching of the magnets during regular operation and protects the accelerator components from damage in the event of beam loss. To assure that the installed collimators will protect the machine and permit the required performance of the collider, an appropriate hardware commissioning has to be implemented. In this contribution we describe the procedures for the hardware commissioning of the LHC collimation system. These procedures will establish the required precision and reliability of collimator movements and settings before the start of beam operation.
27473327
Transverse impendance of LHC collimators
The transverse impedance in the LHC is expected to be dominated by the numerous collimators, most of which are made of Fibre-Reinforced-Carbon to withstand the impacts of high intensity proton beams in case of failures, and which will be moved very close to the beam, with full gaps of few millimetres, in order to protect surrounding super-conducting equipments. We present an estimate of the transverse resistive-wall impedance of the LHC collimators, the total impedance in the LHC at injection and top energy, the induced coupled-bunch growth rates and tune shifts, and finally the result of the comparison of the theoretical predictions with measurements performed in 2004 and 2006 on a prototype collimator installed in the SPS.
45080627
COLLIMATEUR INTEGRATION AND INSTALLATION EXAMPLE OF ONE OBJECT TO BE INSTALLED IN THE LHC
The collimation system is a vital part of the LHC project, protecting the accelerator against unavoidable regular and irregular beam loss. About 80 collimators will be installed in the machine before the first run. Two insertion regions are dedicated to collimation and these regions will be among the most radioactive in the LHC. The space available in the collimation regions is very restricted, it was therefore important to ensure that the 3-D integration of these areas of the LHC tunnel would allow straightforward installation of collimators and also exchange of collimators under the remote handling constraints imposed by high radiation levels. The paper describes the 3D integration studies and verifications of the collimation regions combining the restricted space available, the dimensions of the different types of collimators and the space needed for transport and handling. The paper explains how installation has been planned and carried out taking into account the handling
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.
119955498
A model of lasing axion clusters
Abstract If axions make up the majority of the dark matter, then most are nonthermal and likely to be clustered in gravitational potential wells. For a range of cluster mass M, cluster radius R, and axion mass m a , photons from spontaneous axion decay can trigger exponential growth of photon number via stimulated decay. We derive (i) constraints on these parameters for lasing to occur, and (ii) the lasing rate equations for a general axion distribution. A simple axion cluster model with a flat momentum distribution is studied in analytical and numerical detail.
123670423
A single solution to the atmospheric and solar neutrino anomalies
Abstract We reconsider ν e - ν μ mixing as a solution for the low energy atmospheric neutrino anomaly, with δm 2 in the range (0.5−1.4)× 10 −2 eV 2 and sin 2 (2 θ ) near 0.8, and point out that it may provide a solution to the solar neutrino problem as well. This two-family vacuum oscillation solution is the simplest viable explanation of both phenomena. We consider the theoretical and experimental implications of this scenario, and another simple scenario involving three flavor mixing, and note that the new round of neutrino experiments will test these hypotheses.
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.
16600942
Indirect Detection of Dark Matter WIMPs in a Liquid Argon TPC
We assess the prospects for indirect detection of Weakly Interacting Massive Particles using a large Liquid Argon TPC detector. Signal events will consist of energetic electron (anti)neutrinos coming from the decay of τ leptons and b quarks produced in WIMP annihilation in the core of the Sun. Background contamination from atmospheric neutrinos is expected to be low, thanks to the superb angular resolution and particle identification capabilities provided by the considered experimental set-up. We evaluate the event rates predicted for an annihilating WIMP as a function of its elastic scattering cross section with nucleons. This technique is particularly useful for WIMPs lighter than ∼ 100 GeV.
124595157
AN OVERVIEW OF THE HIGGS SECTOR WITH SPECULATION