Search results for "Muon"
showing 10 items of 1376 documents
Magnetic order and local field distribution in the hybrid magnets [FeCp*(2)][MnCr(ox)(3)] and [CoCp*(2)][FeFe(ox)(3)]: a muon spin relaxation study
2016
Zero-field muon spin relaxation (μ+SR) measurements on materials from the series [ZIIICp*2][M IIMIII(ox)3] show precession signals at several frequencies, characteristic of quasistatic magnetic fields at up to three distinct muon sites.
A note on Δn ≠ 0 Stark transitions in hydrogenlike atoms
1992
In a gaseous helium or hydrogen target slow muons or antiprotons are captured into orbits with a high principal quantum number (n = 15 to 50) to form (μ− α)+ ions, (pα)+ ions, or (pp) atoms respectively. In the subsequent deexcitation process Stark mixing of the intermediary states plays an important role. The successful Mainz Cascade Model assumed Δn = 0 for the Stark transitions, although formally no such selection rule exists. This note examines the reasons why Δn ≠ 0 Stark transitions play only a negligible role in the deexcitation cascade.
Highlights from the COMPASS experiment at CERN. Hadron spectroscopy and excitations
2016
The COMPASS experiment at the CERN-SPS studies the spectrum and the structure of hadrons by scattering high energy hadrons and polarised muons off various fixed targets. Recent results for the hadron programme comprise highlights from different topics. A selective overview is given and, among others, the following results are discussed. The precise determination of the pion polarisability, a long standing puzzle that has been solved now, is presented as well as measurements of radiative widths. The observation of a new narrow axial-vector state, the $a_1(1420)$, as well as deeper insights into the exotic $1^{-+}$-wave, which is under study since decades by several experiments, are discussed…
The ATLAS level-1 trigger: Status of the system and experience from commissioning with cosmic ray muons
2007
The detector at CERN's large hadron collider (LHC) was exposed to proton-proton collisions from beams crossing at 40 MHz. A three-level trigger system will select potentially interesting events in order to reduce this rate to 100- 200 Hz. A trigger decision is made by the Level-1 central trigger processor (CTP) reducing the incoming rate to less than 100 kHz. The Level-1 decision is based on calorimeter information and hits in dedicated muon trigger detectors. The final Level-1 trigger system is currently being installed in the experiment with completion expected in autumn 2007. Cosmic ray data are regularly recorded as an increasing fraction of the trigger system comes online. We present a…
The storage ring magnet of the third muon (g-2) experiment at CERN
1978
The third ( g −2) experiment carried out at CERN required a storage ring magnet with a field as uniform as possible and known with an accuracy of a few parts per million over the whole storage region. Here we describe this magnet, which has a useful aperture of 120 mm horizontally and 80 mm vertically and a diameter of ∼14 m. The various field controls necessary are indicated, and the complex procedure adopted for the shimming work is described. The finally reached homogeneity of the field, averaged in azimuth, was 3 ppm. All the various error sources and field map corrections needed are analysed. Finally, the special aspects of the machine developed for the shimming are described.
Measurement of Azimuthal Anisotropy of Muons from Charm and Bottom Hadrons in pp Collisions at s=13 TeV with the ATLAS Detector
2020
The elliptic flow of muons from the decay of charm and bottom hadrons is measured in pp collisions at sqrt[s]=13 TeV using a data sample with an integrated luminosity of 150 pb^{-1} recorded by the ATLAS detector at the LHC. The muons from heavy-flavor decay are separated from light-hadron decay muons using momentum imbalance between the tracking and muon spectrometers. The heavy-flavor decay muons are further separated into those from charm decay and those from bottom decay using the distance-of-closest-approach to the collision vertex. The measurement is performed for muons in the transverse momentum range 4-7 GeV and pseudorapidity range |η|<2.4. A significant nonzero elliptic anisotro…
Theory of the n = 2 levels in muonic helium-3 ions
2017
The present knowledge of Lamb shift, fine-, and hyperfine structure of the 2S and 2P states in muonic helium-3 ions is reviewed in anticipation of the results of a first measurement of several 2S → 2P transition frequencies in the muonic helium-3 ion, μ3He+. This ion is the bound state of a single negative muon μ- and a bare helium-3 nucleus (helion), 3He++. A term-by-term comparison of all available sources, including new, updated, and so far unpublished calculations, reveals reliable values and uncertainties of the QED and nuclear structure-dependent contributions to the Lamb shift and the hyperfine splitting. These values are essential for the determination of the helion rms charge radiu…
Optical response of highly reflective film used in the water Cherenkov muon veto of the XENON1T dark matter experiment
2017
The XENON1T experiment is the most recent stage of the XENON Dark Matter Search, aiming for the direct detection of Weakly Interacting Massive Particles (WIMPs). To reach its projected sensitivity, the background has to be reduced by two orders of magnitude compared to its predecessor XENON100. This requires a water Cherenkov muon veto surrounding the XENON1T TPC, both to shield external backgrounds and to tag muon-induced energetic neutrons through detection of a passing muon or the secondary shower induced by a muon interacting in the surrounding rock. The muon veto is instrumented with $84$ $8"$ PMTs with high quantum efficiency (QE) in the Cherenkov regime and the walls of the watertank…
Performance of the large scale HV-CMOS pixel sensor MuPix8
2019
The Mu3e experiment is searching for the charged lepton flavour violating decay $ ��^+\rightarrow e^+ e^- e^+ $, aiming for an ultimate sensitivity of one in $10^{16}$ decays. In an environment of up to $10^9$ muon decays per second the detector needs to provide precise vertex, time and momentum information to suppress accidental and physics background. The detector consists of cylindrical layers of $50\, ��\text{m}$ thin High Voltage Monolithic Active Pixel Sensors (HV-MAPS) placed in a $1\,\text{T}$ magnetic field. The measurement of the trajectories of the decay particles allows for a precise vertex and momentum reconstruction. Additional layers of fast scintillating fibre and tile detec…
Track reconstruction for theMu3eexperiment based on a novel Multiple Scattering fit
2017
The Mu3e experiment is designed to search for the lepton flavor violating decay μ + → e + e + e − . The aim of the experiment is to reach a branching ratio sensitivity of 10−16 . In a first phase the experiment will be performed at an existing beam line at the Paul-Scherrer Institute (Switzerland) providing 108 muons per second, which will allow to reach a sensitivity of 2 · 10−15 . The muons with a momentum of about 28 MeV/c are stopped and decay at rest on a target. The decay products (positrons and electrons) with energies below 53MeV are measured by a tracking detector consisting of two double layers of 50 μm thin silicon pixel sensors. The high granularity of the pixel detector with a …