Search results for "Muon"

EMMA – a new underground cosmic-ray experiment

2008

An experiment observing underground muons originating from cosmic-ray air showers is under preparation in the Pyhasalmi mine, Finland. The aim is to cover an area of about 200-300 m(2), and the detector setup is capable of measuring the muon multiplicity and their lateral distribution. The detector is placed at a depth of about 85 m (corresponding about 240 m w.e.), which gives a threshold energy of muons of about 45 GeV. The detection of the multimuon events is motivated by partly unknown composition of the primary cosmic rays in the energy region of 10(15)-10(16) eV, i.e., the knee region. In addition, by measuring only the higher energy muons of the air shower, the lowest energy muons be…

Physical mechanism of the linear beam-size effect at colliders

1996

We present qualitative but precise description of the linear beam-size effect predicted for the processes in which unstable but long--living particles collide with each other. We derive physically pronounced equation for the events rate which proves that the linear beam-size effect corresponds to the scattering of one beam of particles on the decay products of the other. We compare this linear beam-size effect with the known logarithmic beam-size effect measured in the experiments on a single bremsstrahlung at VEPP-4 and HERA.

Search for muoproduction of X(3872) at COMPASS and indication of a new state X˜(3872)

2018

Abstract We have searched for exclusive production of exotic charmonia in the reaction μ + N → μ + ( J / ψ π + π − ) π ± N ′ using COMPASS data collected with incoming muons of 160 GeV/c and 200 GeV/c momentum. In the J / ψ π + π − mass distribution we observe a signal with a statistical significance of 4.1 σ. Its mass and width are consistent with those of the X ( 3872 ) . The shape of the π + π − mass distribution from the observed decay into J / ψ π + π − shows disagreement with previous observations for X ( 3872 ) . The observed signal may be interpreted as a possible evidence of a new charmonium state. It could be associated with a neutral partner of X ( 3872 ) with C = − 1 predicted b…

Nuclear charge radii of the tin isotopes from muonic atoms.

1990

The muonic atom 2${\mathit{p}}_{1/2}$-1${\mathit{s}}_{1/2}$ and 2${\mathit{p}}_{3/2}$-1${\mathit{s}}_{1/2}$ transition energies were measured with an experimental accuracy of better than 20 ppm for the isotope chain $^{112,114,116,117,118,119,120,122,124}\mathrm{Sn}$. Precise values for the Barrett equivalent nuclear radii ${\mathit{R}}_{\mathit{k}\mathrm{\ensuremath{\alpha}}}$ and their differences as well as root-mean-square radii were deduced. The \ensuremath{\Delta}N=2 isotope shifts between the even Sn isotopes show a subshell effect at the neutron number N=64. Otherwise, there is a nearly linear decrease with increasing N, in accordance with the general systematics of nuclear charge r…

Underground cosmic-ray experiment EMMA

2007

A new cosmic-ray experiment is under construction in the Pyhasalmi mine, Finland. It aims to study the chemical composition of cosmic rays at and above the knee region. The array, called EMMA, will cover approximately 150 m2 of detector area at the depth of 85 metres ( ∼ 240  mwe ). It is capable of measuring the multiplicity and the lateral distribution of underground muons, and the arrival direction of the air shower. The full-size array is expected to be ready by the end of 2007. A partial-size array (one third of the full size) is planned to record data already at the first quarter of 2007. The array is also expected to be capable of measuring such high-multiplicity muon bundles as was …

RECENT RESULTS FROM AMANDA

2001

We present results based on data taken in 1997 with the 302-PMT Antarctic Muon and Neutrino Detector Array-B10 ("AMANDA-B10") array. Atmospheric neutrinos created in the northern hemisphere are observed indirectly through their charged current interactions which produce relativistic, Cherenkov-light-emitting upgoing muons in the South Pole ice cap. The reconstructed angular distribution of these events is in good agreement with expectation and demonstrates the viability of this ice-based device as a neutrino telescope.

Longitudinal double-spin asymmetry A1p and spin-dependent structure function g1p of the proton at small values of x and Q2

2018

Abstract We present a precise measurement of the proton longitudinal double-spin asymmetry A 1 p and the proton spin-dependent structure function g 1 p at photon virtualities 0.006 ( GeV / c ) 2 Q 2 1 ( GeV / c ) 2 in the Bjorken x range of 4 × 10 − 5 x 4 × 10 − 2 . The results are based on data collected by the COMPASS Collaboration at CERN using muon beam energies of 160 GeV and 200 GeV . The statistical precision is more than tenfold better than that of the previous measurement in this region. In the whole range of x , the measured values of A 1 p and g 1 p are found to be positive. It is for the first time that spin effects are found at such low values of x .

Structure functions from the NMC

1992

The New Muon Collaboration has measured deep inelastic muon scattering on hydrogen and deuterium at incident energies of 90 and 280 GeV. From the measured cross section ratios σd/σp the difference of R, the ratio of longitudinally to transversely polarised virtual photon absorption cross sections, was obtained. Covering a range in x from 0.01 to 0.3 at a typical Q2 of 9 GeV2 the results are compatible with zero. The structure functions F2p and F2d were extracted in a wide kinematic range: 0.006 1 GeV2. Extrapolation to small χ of recent parton distributions are shown to disagree with the NMC results.

Muon Knight shift studies of the valence transition in Ce0�74Th0�26

1981

Measurement of the ϒ(1S) production cross-section in pp collisions at s=7 TeV in ATLAS

2011

A measurement of the cross-section for ϒ ( 1 S ) → μ + μ − production in proton–proton collisions at centre of mass energy of 7 TeV is presented. The cross-section is measured as a function of the ϒ ( 1 S ) transverse momentum in two bins of rapidity, | y ϒ ( 1 S ) | 4 GeV and pseudorapidity | η μ | < 2.5 in order to reduce theoretical uncertainties on the acceptance, which depend on the poorly known polarisation. The results are based on an integrated luminosity of 1.13 pb−1, collected with the ATLAS detector at the Large Hadron Collider. The cross-section measurement is compared to theoretical predictions: it agrees to within a factor of two with a prediction based on the NRQCD model incl…