First observations of separated atmospheric nu_mu and bar{nu-mu} events in the MINOS detector

Falk Harris, I. E., Harris, Philip, Thomson, Matthew Geoffrey and Symes, P. A. (2006) First observations of separated atmospheric nu_mu and bar{nu-mu} events in the MINOS detector. Physical Review D, D73. ISSN 1550-7998

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Abstract

The complete 5.4 kton MINOS far detector has been taking data since the beginning of August 2003 at a depth of 2070 meters water-equivalent in the Soudan mine, Minnesota. This paper presents the first MINOS observations of nuµ and [overline nu ]µ charged-current atmospheric neutrino interactions based on an exposure of 418 days. The ratio of upward- to downward-going events in the data is compared to the Monte Carlo expectation in the absence of neutrino oscillations, giving Rup/downdata/Rup/downMC=0.62-0.14+0.19(stat.)±0.02(sys.). An extended maximum likelihood analysis of the observed L/E distributions excludes the null hypothesis of no neutrino oscillations at the 98% confidence level. Using the curvature of the observed muons in the 1.3 T MINOS magnetic field nuµ and [overline nu ]µ interactions are separated. The ratio of [overline nu ]µ to nuµ events in the data is compared to the Monte Carlo expectation assuming neutrinos and antineutrinos oscillate in the same manner, giving R[overline nu ][sub mu]/nu[sub mu]data/R[overline nu ][sub mu]/nu[sub mu]MC=0.96-0.27+0.38(stat.)±0.15(sys.), where the errors are the statistical and systematic uncertainties. Although the statistics are limited, this is the first direct observation of atmospheric neutrino interactions separately for nuµ and [overline nu ]µ.

Item Type: Article
Keywords: Neutrino interactions, Charged currents, Neutrino oscillations, Cosmic ray interactions, Cosmic ray muons, Cosmic ray neutrinos
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Subjects: Q Science > QC Physics
Depositing User: Gemma Farrell
Date Deposited: 23 Nov 2007
Last Modified: 01 Oct 2019 11:30
URI: http://sro.sussex.ac.uk/id/eprint/1611
Google Scholar:0 Citations

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