Muon Charge Ratio Research Articles

First results of the RPC commissioning at BESIII

The commissioning of the RPC-based muon detector in the BESIII experiment has been carried out. The RPC modules, front-end electronics, online and offline software of the muon system have been studied. The detector performances including efficiency, counting rate, noise ratio, spacial resolution, dark current, and muon charge ratio were obtained by cosmic ray data with and without magnetic field. The new operating high voltage and threshold were chosen after the scan experiment. The long-term stability of the BESIII RPCs made of bakelite without oil treatment was studied.

The muon charge ratio in cosmic ray air showers

The muon charge ratio of the lateral muon density distributions in single EAS is studied by simulations, in context of recent proposals to measure this observable in coincidence with EAS observations. While effects of the hadronic interaction do not lead to significant differences of the total μ+ and μ− content, the differences of the azimuthal variation of the muon densities of opposite charges and the azimuthal variation of the muon charge ratio appear to be very much pronounced, dependent on the direction of EAS incidence. This is due to the influence of the geomagnetic field which induces related effects in radio emission from extended air showers.

MUON CHARGE RATIO OF ULTRAHIGH ENERGY COSMIC RAYS

The muon charge ratio of ultrahigh energy cosmic rays may provide information to detect the composition of the primary cosmic rays. We propose to extract the charge information of high energy muons in very inclined extensive air showers by analyzing their relative lateral positions in the shower transverse plane.

WILLI – a scintillator detector setup for studies of the zenith and azimuth variation of charge ratio and flux of atmospheric muons

The primary and secondary components of the cosmic radiation are influenced by the geomagnetic field. This leads - in addition to the variation with the zenith angle - to an azimuth dependence, in particular of the ratio of positive and negative muons, pronounced as East-West effect of muon charge ratio for low energy muons. The compact scintillator detector arrangement, WILLI, able to register incident muons with different azimuth and zenith angles ( E 1 G e V ), has been used to study the azimuth dependence of the muon charge ratio. Positive and negative muons are discriminated by observing the different lifetimes when being stopped in matter, in the WILLI case by Al absorbers. We are considering the development of a mini array, installed close to the WILLI detector, for triggering the muon charge ratio measurements in extended air shower events.

Cosmic Ray Results from the CosmoALEPH Experiment

CosmoALEPH is an experiment operated in conjunction with the ALEPH detector. The ALEPH experiment took data from 1989 until the year 2000 at the Large Electron Positron Collider (LEP) at CERN. It provides, among others, high resolution tracking and calorimetry. CosmoALEPH used this e + e − detector for cosmic ray studies. In addition, six scintillator telescopes were installed in the ALEPH pit and the LEP tunnel. The whole experiment operated underground at a vertical depth of 320 meter water equivalent. Data from ALEPH and the scintillator telescopes provide informaton on the lateral distribution of energetic cosmic ray muons in extensive air showers. The decoherence curve of these remnant air shower muons is sensitive to the chemical composition of primary cosmic rays and to the interaction characteristics of energetic hadrons in the atmosphere. An attempt is made to extract the various interdependencies in describing the propagation of primary and secondary cosmic rays through the atmosphere and the rock overburden, and comparing the data with results from Monte Carlo (MC) calculations. Results on the multiplicity distributions of remnant air shower muons in ALEPH are also compared with expectations based on MC simulations. Data on the cosmic ray muon spectrum and charge ratio up to momenta of 3 TeV/c as obtained with the time projection chamber in ALEPH's strong magnetic field are presented. The large number of events also allowed to unambiguously observe muon tridents and to estimate the cross section for this process.

Measurement of the atmospheric muon charge ratio at TeV energies with the MINOS detector

The 5.4 kton MINOS far detector has been taking charge-separated cosmic ray muon data since the beginning of August, 2003 at a depth of 2070 meters-water-equivalent in the Soudan Underground Laboratory, Minnesota, USA. The data with both forward and reversed magnetic field running configurations were combined to minimize systematic errors in the determination of the underground muon charge ratio. When averaged, two independent analyses find the charge ratio underground to be 1.374 +/- 0.004 (stat.) +0.012 -0.010(sys.). Using the map of the Soudan rock overburden, the muon momenta as measured underground were projected to the corresponding values at the surface in the energy range 1-7 TeV. Within this range of energies at the surface, the MINOS data are consistent with the charge ratio being energy independent at the two standard deviation level. When the MINOS results are compared with measurements at lower energies, a clear rise in the charge ratio in the energy range 0.3 -- 1.0 TeV is apparent. A qualitative model shows that the rise is consistent with an increasing contribution of kaon decays to the muon charge ratio.

The charge ratio of the atmospheric muons at low energy

From the nature of the muon production processes, it can be seen that the ratio of positive to negative cosmic muons has important information in both ``the atmospheric neutrino problem,'' and ``the hadronic interactions.'' We have carried out an experiment for the measurement of the muon charge ratio in the cosmic ray flux in momentum range $0.112--0.178\text{ }\text{ }\mathrm{GeV}/\mathrm{c}$. The muon charge ratio is found to be $1.21\ifmmode\pm\else\textpm\fi{}0.01$ with a mean zenith angle of $32\ifmmode^\circ\else\textdegree\fi{}\ifmmode\pm\else\textpm\fi{}5\ifmmode^\circ\else\textdegree\fi{}$. From the measurements it has been obtained a zenithal angle distribution of muons as $I(\ensuremath{\theta})=I(0){cos}^{n}\ensuremath{\theta}$ with $n=1.95\ifmmode\pm\else\textpm\fi{}0.13$. An asymmetry has been observed in East-West directions because of the geomagnetic field. Meanwhile, in about the same momentum range, positive and negative muons have been studied on the basis of Monte Carlo simulations of the extensive air shower developement (Cosmic Ray Simulations for Kascade), using the Quark Gluon String model with JETs model as generator.

Cosmic ray studies with the L3-cosmics program at CERN

The L3 detector at the CERN electron-positron collider had a muon spectrometer which was employed during the last years of LEP operation for cosmic ray studies. The results of this program include a precise muon spectrum and charge ratio between 20 GeV and 3 TeV, a limit on TeV primary antiprotons from a study of the Moon’s shadow, the (possible) observation of a are signal from a fixed position in the northern hemisphere through muons, a solar anisotropy of 200 GeV protons, and other results. Negative limits on muons associated with known H.E. gamma sources or gamma bursts, the search for anomalous H.E. interaction or decay events such as reported from the Kolar Gold Fields, and a search for muons correlated with a solar are are also noted.

AN ALTERNATIVE METHOD TO OBTAIN THE MUON CHARGE RATIO AT SEA LEVEL

The vertical muon charge ratio generated from hadron showers in the earth's atmosphere is obtained accurately in the energy range from a few GeV to several TeV. To solve the hadron diffusion equations we apply the analytical method based on depth-like ordered exponential operator. A comparison among our calculations (with and without scaling violation) with the measured ratio and Lipari's analytical calculation is made. Our differential muon fluxes are also compared with data at sea level.

Low energy muons in the cosmic radiation

A review of measurements of the muon energy spectra for different altitudes, height and directions performed with devices placed at various geomagnetic latitudes is presented. The muon spectra and the muon charge ratio, defined as the ratio of positive to negative muon fluxes, are analysed taking into account the geomagnetic field, in view of the East-West effect. Fluxes of both positive and negative muons are analysed.

Experimentally guided Monte Carlo calculations of the atmospheric muon and neutrino flux

The WILLI detector upgraded with the possibility to detect muons from different zenith and azimuthal angles of incidence is used to measure the charge ratio of low energy atmospheric muons, in particular the East -West effect. The results of Monte Carlo simulations with the CORSIKA code can be fairly well understood if the solar modulation, the geomagnetic cut-off and the local magnetic field are taken into account by the simulations. The data can be used to scrutinize the high-energy hadronic interaction models used as generators in the Monte Carlo program CORSIKA, and they shed some light on the models DPMJET, VENUS, UrQMD, currently in vogue. Via this procedure, having refined and calibrated the ingredients of the CORSIKA code, atmospheric muon and neutrino fluxes have been calculated and compared with recent measurements of the atmospheric muon flux and other calculations of the neutrino flux for various sites of different geomagnetic coordinates. Additionally, based on our simulations of the muon flux with CORSIKA, semi-analytical approximations used to calculate the muon flux for different applications, can be checked.

Atmospheric muon measurements using the OKAYAMA telescope

The atmospheric muon spectrum has been measured at sea level using a magnet spectrometer called the OKAYAMA telescope. The OKAYAMA telescope is able to point at any azimuth and zenith angle and to measure the muon energy and charge sign. We report the absolute atmospheric muon differential energy spectrum, charge ratio and azimuthal angular dependences.

Neutrons and antiprotons in ultrahigh-energy cosmic rays

The neutron fraction in the very high energy cosmic rays near the Greisen-Zatsepin-Kuzmin (GZK) cutoff energy is analyzed by taking into account the time dilation effect of the neutron decays and also the pion photoproduction behaviors above the GZK cutoff. We predict a non-trivial neutron fraction above the GZK cutoff and a negligibly small neutron fraction below. However, there should be a large antiproton fraction in the high energy cosmic rays below the GZK cutoff in several existing models for the observed cosmic-ray events above and near the GZK cutoff. Such a large antiproton fraction can manifest itself by the muon charge ratio $\mu^+/\mu^-$ in the collisions of the primary nucleon cosmic rays with the atmosphere, if there is no neutron contribution. We suggest to use the muon charge ratio as one of the information to detect the composition of the primary cosmic rays near or below the GZK cutoff.

Experimental studies of positive and negative atmospheric muons with a cosmic rays telescope

An experiment has been developed for the measurement of the muon charge ratio (ratio of positive to negative muons) in the cosmic ray flux in energy range 0.236–0.242 GeV. The muon charge ratio is found to be 1.35 ± 0.10 with a mean zenith angle of 32° ± 5°. Meanwhile, the distributions of muons in zenith ( θ) and azimuth angles have been studied. A cos n θ distribution with n = 1.95 ± 0.13 has been obtained. An asymmetry has been observed in East–West directions because of geomagnetic field.

Measurement of the Atmospheric Muon Spectrum from 20 to 3000 GeV

The absolute muon flux between 20 and 3000 GeV was measured with the L3 magnetic muon spectrometer for zenith angles ranging from 0 0 to 58 0 . Due to the large exposure of about 150 m 2 sr d and the excellent momentum resolution of the L3 muon chamber system, the muon flux was determined with a precision of 2.3 % at 150 GeV in the vertical direction. The ratio of positive to negative muons was studied between 20 and 500 GeV. The average vertical muon charge ratio is found to be 1.285 ± 0.003 (stat.)± 0.019 (sys.)

New measurement of the altitude dependence of the atmospheric muon intensity

We present a new measurement of atmospheric muons made during an ascent of the High Energy Antimatter Telescope balloon experiment. The muon charge ratio ${\ensuremath{\mu}}^{+}/{\ensuremath{\mu}}^{\ensuremath{-}}$ as a function of atmospheric depth in the momentum interval 0.3--0.9 GeV/c is presented. The differential ${\ensuremath{\mu}}^{\ensuremath{-}}$ intensities in the 0.3--50 GeV/c range and for atmospheric depths between $4--960\text{ }\text{ }\mathrm{g}/{\mathrm{c}\mathrm{m}}^{2}$ are also presented. We compare these results with other measurements and model predictions. We find that our charge ratio is $\ensuremath{\sim}1.1$ for all atmospheric depths and is consistent, within errors, with other measurements and the model predictions. We find that our measured ${\ensuremath{\mu}}^{\ensuremath{-}}$ intensities are also consistent with other measurements, and with the model predictions, except at shallow atmospheric depths.

Measurement of the atmospheric muon spectrum from 20 to 3000 GeV

The absolute muon flux between 20 and 3000 GeV is measured with the L3 magnetic muon spectrometer for zenith angles ranging from 0° to 58°. Due to the large exposure of about 150m2sr d, and the excellent momentum resolution of the L3 muon chambers, a precision of 2.3% at 150 GeV in the vertical direction is achieved. The ratio of positive to negative muons is studied between 20 and 500 GeV, and the average vertical muon charge ratio is found to be 1.285±0.003(stat.)±0.019(syst.).

Measurement of the atmospheric muon spectrum from 20 to 3000 GeV

The absolute muon flux between 20 and 3000 GeV is measured with the L3 magnetic muon spectrometer for zenith angles ranging from 0° to 58°. Due to the large exposure of about 150 m2sr d, and the excellent momentum resolution of the L3 muon chambers, a precision of 2.3% at 150 GeV in the vertical direction is achieved.The ratio of positive to negative muons is studied between 20 and 500 GeV, and the average vertical muon charge ratio is found to be 1.285±0.003(stat.)±0.019(syst.).

The cosmic ray muon spectrum and charge ratio in CosmoALEPH

The ALEPH experiment at the LEP e +e − storage ring at CERN has been used to measure the momentum spectrum of cosmic ray muons. ALEPH is located at a vertical depth of 320 m.w.e. underground close to the Jura mountains. The high resolution of the time projection chamber (TPC) of ALEPH allows to reconstruct muon tracks with momenta up to the TeV region. The measured muon momentum spectrum and the charge ratio in the range from 80 to 2500 GeV are presented. After corrections for energy loss in the overburden the sea level muon spectrum at nearly vertical incidence is obtained. The experimental data are compared to theoretical expectations and results from other experiments.

The East-West effect of the muon charge ratio at energies relevant to the atmospheric neutrino anomaly

The charge ratio of atmospheric muons is rather sensitive to effects of the geomagnetic field and to the hadronic interaction. Experimental information about this quantity is very useful for tuning the ingredients of models used for calculations of atmospheric neutrino fluxes. For experimental observations, and in particular regarding the asymmetry in the charge ratio of muons from the east and West directions (East-West effect) a rotatable device has been installed in NIPNE-HH (National Institute of Physics and Nuclear Engineering — Horia Hulubei) Bucharest (44° 26'N, 26° 04' E, 85 m above sea-level at a vertical cut-off rigidity of 5.6 GV). The detector is mounted in a rotatable frame, consisting of a stack of 16 modules, 90 × 90 cm 2, formed by plastic scintillator layers (3 cm thick) and aluminum support (1.2 cm thick), surrounded by 4 lateral veto counters. The measurements are based on observation of the life time of muons stopped in the absorber layers of the detector. At a mean zenith angle of 35° the East West asymmetry in the ratio has been found to decrease from 0.25 to 0.20, in the momentum range 0.35 – 0.50 GeV/c.