Muon Charge Research Articles

WILLI - EAS - a detection system for investigating the muon charge ratio in Extensive Air Showers

A concept of an experiment for investigating the muon charge ratio in EAS has been proposed based on the existing WILLI detector designed for measurements of the atmospheric muon charge ratio. A mini-array surrounding WILLI for measuring EAS is presently under construction. This array will serve as a core-finder system consisting of 12 stations of 1 m2, each unit containing 4 plastic scintillator sheets ( 50 × 50 × 3 ) cm 3 , seen by wave length shifters and 2 photomultipliers. Using CORSIKA and GEANT codes, simulation studies have been performed for H and Fe generated showers (1014–1015) eV to optimize the configuration of the WILLI-EAS arrangement. By this device, measurements of the charge ratio can be performed for both in parallel, inclusive muons and EAS muons.

The OPERA experiment at Gran Sasso

OPERA (Oscillation Project with Emulsion tRacking Apparatus) is a long baseline neutrino experiment aiming to detect for the first time the appearance of tau neutrinos in a pure muon neutrino beam. The OPERA detector is exposed to the CNGS beam (CERN Neutrinos to Gran Sasso), a high-intensity and high-energy beam of muon neutrinos produced at the CERN SPS and directed toward the Gran Sasso underground laboratory (LNGS), 730 km away. The LNGS laboratory is situated under an average depth of 3800 meters water equivalent, making OPERA the deepest experiment able to measure cosmic ray muons with a magnetized detector, e.g. the cosmic ray muon charge ratio. Cosmic ray events were observed, together with the first neutrino beam events, during the 2007 and 2008 CNGS runs. This paper reviews the experimental apparatus, presents the first results for neutrino data and describes the analysis of cosmic ray data.

Investigation of cosmic ray muons with the WILLI detector compared with the predictions of theoretical models and with semi-analytical formulae

The WILLI detector, built in IFIN-HH, Bucharest, is used to measure the muon flux and the muon charge ratio at low energy (

The muon charge ratio in cosmic ray air showers

The muon charge ratio of the lateral muon density distributions in single Extended Air Showers (EAS) is studied on the basis of Monte Carlo simulations, in view of proposals to measure this observable in coincidence with EAS observations. 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 the EAS incidence and the position of the observer in respect to the Earth's magnetic vector. The influence of the geomagnetic field, which induces comparable effects in radio emission from EAS, is obviously of great interest for understanding the shower development.

Interpretation of the underground muon charge ratio

The MINOS experiment has observed a rise in the underground muon charge ratio r μ = μ + / μ - . This ratio can be related to the atmospheric production ratios of π + / π - and K + / K - . Our analysis indicates that the relevant variable for studying the charge ratio is E μ surface cos θ , rather than E μ surface . We compare a simple energy dependent parameterization of the rise in the charge ratio with more detailed previously published Monte Carlo simulations and an analytical calculation. We also estimate the size of two previously neglected effects in this context: the charge sign dependency of the d E/d x in rock, and the energy dependence of heavy primaries on the derived K + / K - ratio.

Penetration depth, multiband superconductivity, and absence of muon-induced perturbation in superconductingPrOs4Sb12

Transverse-field muon spin rotation $(\text{TF-}\ensuremath{\mu}\text{SR})$ experiments in the heavy-fermion superconductor ${\text{PrOs}}_{4}{\text{Sb}}_{12}({T}_{c}=1.85\text{ }\text{K})$ suggest that the superconducting penetration depth $\ensuremath{\lambda}(T)$ is temperature independent at low temperatures, consistent with a gapped quasiparticle excitation spectrum. In contrast, radio frequency inductive measurements yield a stronger temperature dependence of $\ensuremath{\lambda}(T)$, indicative of point nodes in the gap. Muon Knight-shift measurements in the normal state of ${\text{PrOs}}_{4}{\text{Sb}}_{12}$ suggest that the perturbing effect of the muon charge on the neighboring ${\text{Pr}}^{3+}$ crystalline electric field is negligibly small and therefore is unlikely to cause the difference between the $\text{TF-}\ensuremath{\mu}\text{SR}$ and rf results. The discrepancy appears to be related to multiband superconductivity in ${\text{PrOs}}_{4}{\text{Sb}}_{12}$.

Did the 2000 July 14 solar flare accelerate protons to ⩾40 GeV?

It has been reported that a 4.2 σ directional muon excess coincident with the 2000 July 14 solar flare was registered by the L3 precision muon spectrometer [The L3 collaboration, P. Achard et al., A&A, 456 (2006) 351]. Using similar analysis method and optimized criteria for event selection we have obtained a 5.7 σ muon excess in the same sky region and a time duration which well coincides with the peak increase of solar protons observed at lower energies and the hard X-ray and γ -ray. Furthermore, the momenta of those enhanced muons is investigated. From the counts of μ + and μ - a low muon charge ratio of μ + μ - is obtained as about 1.1 during this event. A Monte Carlo simulation was carried out for this primary proton beam to produce those secondary muons in this sky region, including extensive air shower simulation starting at the top of the atmosphere and L3+C muon chamber simulation underground. The simulation result indicates that the enhanced muons are produced by primary protons over 40 GeV with a most probable energy of ∼82 GeV. Based on this simulation, a flux upper limit of such a solar proton beam has been estimated as 2.5 × 10 - 3 ( cm - 2 s - 1 sr - 1 ) . These high energy protons were accelerated in the impulsive phase of the flare, at about 2 min late of start of the hard X-ray and γ -ray.

The RPC system of the OPERA experiment

The OPERA experiment is designed to study the ν μ → ν τ oscillation observing the ν τ appearance in a pure ν μ beam over a base line of 732 km from CERN to Gran Sasso Laboratory. The apparatus consists of a lead/emulsion-film target complemented by electronic detectors and muon spectrometers for muon charge and momentum measurements. The tracking inside the magnets is provide by Bakelite RPC chambers in a large scale application. The commissioning of the RPC system ended in August 2006. The paper present the layout of the RPC system and its performances.

High energy and prompt neutrino production in the atmosphere

The AMANDA neutrino telescope has measured the spectrum of atmospheric neutrinos up to 100 TeV and IceCube, which has about 100 times higher acceptance, is expected to collect unprecedented statistics at even higher energies in the near future. IceCube, with 22 strings, has measured about 1.4 kHz of muon rate at trigger level and about 20 neutrino events per day at cut levels suitable for reducing the atmospheric muon content at the level of less than 10%. At energies of about 100 TeV we expect about 1 event per day for atmospheric muons with zenith angle larger than 70 degrees. With these numbers an amount of interesting physics items can be covered, such as investigations of hadronic models in region not covered by colliders, with particular attention to kaon and charm meson and barion physics. In the poster we have shown some of the MC tests we have been performing. As a summary here we show 2 preliminary plots: the one on the left shows what we obtain for CORSIKA using two different hadronic models (SIBYLL and 2 versions of QGSJET) as the fraction of pions and kaons contributing to the production of muons and neutrinos as a function of energy (integrated over all angles); the other shows how these models compare to the muon charge ratio measured by MINOS (P. Adamson et al., Phys. Rev D 76 (2007) 052003) and L3 COSMIC (M. Aglietta et al., Phys. Rev. D 58 (1998) 092005). Other results concerning the introduction of DPMJET with charm production in CORSIKA have been published in Berghaus et al., JCAP06 (2008) 003.

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.

Measurement of the muon charge asymmetry fromWboson decays

We present a measurement of the muon charge asymmetry from W boson decays using 0.3 fb−1 of data collected at s=1.96 GeV between 2002 and 2004 with the D0 detector at the Fermilab Tevatron pp¯ Collider. We compare our findings with expectations from next-to-leading-order calculations performed using the CTEQ6.1M and MRST04 NLO parton distribution functions. Our findings can be used to constrain future parton distribution function fits.Received 27 September 2007DOI:https://doi.org/10.1103/PhysRevD.77.011106©2008 American Physical Society

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.

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.

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.

Determination of the neutrino mass hierarchy in the regime of small matter effect

We point out a synergy between T-conjugated oscillation channels in the determination of the neutrino mass hierarchy with oscillation experiments with relatively short baselines (L < 700 km), where the matter effect is small. If information from all four oscillation channels $\nu_\mu\to\nu_e$, $\bar\nu_\mu\to\bar\nu_e$, $\nu_e\to\nu_\mu$ and $\bar\nu_e\to\bar\nu_\mu$ is available, a matter effect of few percent suffices to break the sign-degeneracy and allows to determine the neutrino mass hierarchy. The effect is discussed by analytical considerations of the relevant oscillation probabilities, and illustrated with numerical simulations of realistic experimental setups. Possible configurations where this method could be applied are the combination of a super beam experiment with a beta beam or a neutrino factory, or a (low energy) neutrino factory using a detector with muon and electron charge identification.

Formula omitted] studies of hydrogen-bonded ferroelectrics and antiferroelectrics

We have performed measurements on crystals of KH 2 PO 4 (KDP, ferroelectric (FE) transition at T FE = 123 K ), NH 4 H 2 PO 4 (ADP, antiferroelectric (AFE) transition at T AFE = 148 K ) and deuterated ADP (DADP, ND 4 D 2 PO 4 , antiferroelectric transition at T AFE = 242 K ). Compounds of this family are covalently bonded molecular PO 4 units linked by a network of hydrogen O–H–O bonds. At any temperature between 2 and 310 K, a substantial fraction of the muons implanted into the crystal appears as muonium. At low temperatures (below ∼ 140 K ), this fraction reaches about one half. The onset of the ferroelectric or antiferroelectic phase transition seems to differently affect the muon charge state. Longitudinal field decoupling measurements show only weak dynamics in the diamagnetic fraction with decoupling already at fields of about 1.5 mT. In the antiferroelectric ADP, the temperature dependence of the static Kubo–Toyabe width obtained from LF global fits exhibits a pronounced increase at the transition temperature.

Muon charge information from geomagnetic deviation in inclined extensive air showers

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. We calculate the muon lateral deviation under the geomagnetic field and compare it to dispersive deviations from other causes. By our criterion of resolvability, positive and negative muons with energies above 10 4 GeV will be clearly separated into two lobes if the shower zenith angle is larger than 70°. Thus we suggest a possible approach to measure the μ +/ μ − ratio for high energy muons.

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.