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.
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
55454565
THE FINAL COLLIMATION SYSTEM FOR THE LHC
The LHC collimation system has been re-designed over in order to address the unprecedented challenges that are faced with the 360 MJ beams at 7 TeV. The layout of the LHC has now been frozen and a final approach for collimation and cleaning has been adopted. In total 132 pure collimator locations have been reserved in the two LHC rings and can be installed in a phased approach. Up to 88 collimators of five different types will be available for initial beam operation. The system has been fully optimized for avoiding beam-induced quenches of superconducting magnets and for sufficient survival of beamline components against radioactive dose. The phased approach for LHC collimation is described, the various collimators and their functionalities are explained, and the expected system performance is summarized. Large Hadron Collider Project
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.
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%.
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.
17439400
JEM-EUSO Science Objectives
JEM-EUSO, on board of the Japanese Exploration Module of the International Space Station, is being proposed as the first space observatory devoted to UHECR. Its privileged position at 430 km above the Earth surface, combined with a large field of view, innovative optics and a high efficiency focal surface, results in an unprecedented exposure which significantly surpasses that of the largest ground observatories. The large number of events expected above the GZK threshold for photo-pion production by protons will allow the directional identification of individual sources and the determination of their spectra, i.e., doing astronomy and astrophysics through the particle channel. Similar goals can be achieved in the case of light UHECR nuclei. Furthermore, the atmospheric target volume ($\sim 10^{12}$ ton) makes the possibility of neutrino observation a highlight of the mission. Other exploratory objectives include the detection of extreme energy gammas and the study of Galactic magnetic fields as well as global observations of the earth's atmosphere, including clouds, night-glows, plasma discharges, and meteors. In this contribution we will describe the scientific objectives of JEM-EUSO.
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.
42363617
Neutrinos as a diagnostic of cosmic ray galactic-extragalactic transition
Motivated by a recent change in viewing the onset of the extragalactic component in the cosmic ray spectrum, we have fitted the observed data down to ${10}^{8.6}\text{ }\text{ }\mathrm{GeV}$ and have obtained the corresponding power emissivity. This transition energy is well below the threshold for resonant $p\ensuremath{\gamma}$ absorption on the cosmic microwave background, and thus source evolution is an essential ingredient in the fitting procedure. Two-parameter fits in the spectral and redshift evolution indices show that a standard Fermi ${E}_{i}^{\ensuremath{-}2}$ source spectrum is excluded at larger than 95% confidence level (CL). Armed with the primordial emissivity, we follow Waxman and Bahcall to derive the associated neutrino flux on the basis of optically thin sources. For $pp$ interactions as the generating mechanism, the neutrino flux exceeds the AMANDA-B10 90% CL upper limits. In the case of $p\ensuremath{\gamma}$ dominance, the flux is consistent with AMANDA-B10 data. In the new scenario the source neutrino flux is considerably enhanced, especially below ${10}^{9}\text{ }\text{ }\mathrm{GeV}$. Should data from AMANDA-II prove consistent with the model, we show that IceCube can measure the characteristic power law of the neutrino spectrum, and thus provide a window on the source dynamics.
17009567
Fate of the sterile neutrino
Abstract In light of recent Super-Kamiokande data and global fits that seem to exclude both pure ν μ → ν s oscillations of atmospheric neutrinos and pure ν e → ν s oscillations of solar neutrinos (where ν s is a sterile neutrino), we reconsider four-neutrino models to explain the LSND, atmospheric, and solar neutrino oscillation indications. We argue that the solar data, with the exception of the 37 Cl results, are suggestive of ν e → ν s oscillations that average to a probability of approximately 1 2 . In this interpretation, with two pairs of nearly degenerate mass eigenstates separated by order 1 eV, the day-night asymmetry, seasonal dependence, and energy dependence for 8 B neutrinos should be small. Alternatively, we find that four-neutrino models with one mass eigenstate widely separated from the others (and with small sterile mixings to active neutrinos) may now be acceptable in light of recently updated LSND results; the 37 Cl data can be accommodated in this model. For each scenario, we present simple four-neutrino mixing matrices that fit the stated criterion and discuss future tests.
119113030
Searching for the Layered Structure of Space at the LHC
Alignment of the main energy fluxes along a straight line in a target plane has been observed in families of cosmic ray particles detected in the Pamir mountains. The fraction of events with alignment is statistically significant for families with superhigh energies and large numbers of hadrons. This can be interpreted as evidence for coplanar hard scattering of secondary hadrons produced in the early stages of the atmospheric cascade development. This phenomenon can be described within the recently proposed 'crystal world,' with latticized and anisotropic spatial dimensions. Planar events are expected to dominate particle collisions at a hard-scattering energy exceeding the scale {Lambda}{sub 3} at which space transitions from 3D{r_equilibrium}2D. We study specific collider signatures that will test this hypothesis. We show that the energy spectrum of Drell-Yan (DY) scattering is significantly modified in this framework. At the LHC, two jet and three jet events are necessarily planar, but four jet events can test the hypothesis. Accordingly, we study in a model-independent way the 5{sigma} discovery reach of the ATLAS and CMS experiments for identifying four jets coplanarities. For the extreme scenario in which all pp {yields} 4 jet scattering processes become coplanar above {Lambda}{sub 3}, we show that withmore » an integrated luminosity of 10(100) fb{sup -1} the LHC experiments have the potential to discover correlations between jets if {Lambda}{sub 3} {approx}< 1.25(1.6) TeV.« less