The charge ratio of muons at sea level in the range 5–600 GeV/c

109

We collect and combine all published data on the vertical atmospheric muon flux and the muon charge ratio for muon momenta above 10 GeV. At sea level the world average of the momentum spectra agrees with the flux calculated by E.V. Bugaev et al. within 15 %. The observed shape of the differential flux versus momentum is slightly flatter than predicted in this calculation. The experimental accuracy varies from 7% at 10 GeV to 17% at 1 TeV. The ratio of fluxes of positive to negative muons is found to be constant, at a value of 1.268, with relative uncertainties increasing from approximately 1% at low momenta to about 6% at 300 GeV.

Section: The Shape Of the Muon Spectrummentioning

confidence: 90%

Section: The Shape Of the Muon Spectrummentioning

confidence: 99%

A compilation of high energy atmospheric muon data at sea level

Hebbeker

Timmermans

2002

109

“…Experiments with data points with relatively large error bars have not been included in this analysis since they are not useful for the precise studies in this paper. Experiments with charge ratio data values at energies above 100 GeV, with all data points having quoted errors greater than +-0.1, have not been included in our analysis; thus Hayman and Wolfendale [12], Appleton et al [13], Nandi et al [14], and Kremer et al [15] are not included. Specifically, Burnett et al [16] was not included in our study due to the absence of any published estimates of systematic error on their ratio values.…”

Section: Compilation Of Measurements Of the Atmospheric Muon Charge Rmentioning

confidence: 99%

“…The agreement between the parametrization and the data is excellent. Using the f values from this fit, we plot Equation 14 for an extended range of muon energy in Figure 9. The critical energies discussed above for pion and kaons are indicated by the arrows.…”

Section: Model Of Pion and Kaon Contributions To The Charge Ratiomentioning

confidence: 99%

Interpretation of the underground muon charge ratio

Schreiner¹,

Reichenbacher²,

Goodman³

2009

Keywords:Underground cosmic ray muons Muon charge ratio Meson charge ratio a b s t r a c tThe MINOS experiment has observed a rise in the underground muon charge ratio r l ¼ l þ =l À . This ratio can be related to the atmospheric production ratios of p þ =p À and K þ =K À . Our analysis indicates that the relevant variable for studying the charge ratio is E surface l cos h, rather than E surface l . 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 dE/dx in rock, and the energy dependence of heavy primaries on the derived K þ =K À ratio.Published by Elsevier B.V. Importance of charge ratio measurementsAtmospheric muons come dominantly from the decay of ps andKs produced in hadronic showers when cosmic rays interact in the earth's atmosphere. These muons have been studied with energies ranging from hundreds of MeV to well over a TeV. A quantitative understanding of cosmic ray muons has value for a number of diverse topics, from atmospheric neutrinos to the chemical composition of the highest energy cosmic rays. The charge ratio of cosmic ray muons has been previously measured over three orders of magnitude in energy. Recently the MINOS experiment [1,2] presented data that for the first time showed a rise in the measured charge ratiofrom previous measurements at high values of E l or more specifically, high values of E surface l cos h. In this paper, we discuss some of the issues involved in the measurement and interpretation of the muon charge ratio. In particular, we develop a simplified model where the rise in the charge ratio can be understood from the properties of p and K mesons, and the observation of the rise can be used to determine the p þ =p À and K þ =K À ratios. We also address several other issues related to the measurement of the charge ratio, including the role of muon energy loss, a detector's Maximum Detectable Momentum (MDM), and the effect of possible differences in the spectral index of cosmic ray Hydrogen and Helium on the interpretation.Since the primary cosmic rays are mostly positively charged protons, more secondary p þ are expected than p À . The quark content of the protons and of the atmosphere has been used to estimate the p þ =p À ratio to be near 1.27 [3]. The charge ratio for kaons is even higher due to the phenomenon of associated production. Strange particle production starts with the creation of an s quark and an s quark. An s quark which ends up in a nucleus is associated with an s quark in a K þ ð suÞ. The s quark will not be in a baryon. There is also K þ K À pair production. Phase space favors hadronic production of K þ K over K þ K À pairs at all energies, so large K þ =K À ratios are expected. A standard parametrization of the atmospheric muon energy spectrum is given by Gaisser [4]:

“…Fig. 9 shows ratios of positive and negative muons together with the previous measurements [33][34][35][36][37], and the results are summarized in Table. 3 and in Table. 4. It was seen that the charge ratio obtained in Tsukuba decreased be- The systematic error due to proton contamination was less than 2 %, therefore the muon charge ratio observed in Lynn Lake had very small systematic errors.…”

Section: Resultsmentioning

confidence: 87%

Precise measurements of atmospheric muon fluxes with the BESS spectrometer

Motoki

Sanuki

Orito

et al. 2003

The vertical absolute fluxes of atmospheric muons and muon charge ratio have been measured precisely at different geomagnetic locations by using the BESS spectrometer. The observations had been performed at sea level (30 m above sea level) in Tsukuba, Japan, and at 360 m above sea level in Lynn Lake, Canada. The vertical cutoff rigidities in Tsukuba (36.2 • N ,140.1 • E) and in Lynn Lake (56.5 • N ,101.0 • W ) are 11.4 GV and 0.4 GV, respectively. We have obtained vertical fluxes of positive and negative muons in a momentum range from 0.6 to 20 GeV/c with systematic errors less than 3 % in both measurements. By comparing the data collected at two different geomagnetic latitudes, we have seen an effect of cutoff rigidity. The dependence on the atmospheric pressure and temperature, and the solar modulation effect have been also clearly observed. We also clearly observed the decrease of charge ratio of muons at low momentum side with at higher cutoff rigidity region.