First observations of separated atmospheric νμ and ν̅ μ events in the MINOS detector

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Adamson, P, Falk Harris, E, Harris, Philip, Symes, P A and MINOS Collaboration, (2006) First observations of separated atmospheric νμ and ν̅ μ events in the MINOS detector. Physical Review D, 73 (7). 072002. 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 muon neutrino and muon anti-neutrino 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: R_data(up/down)/R_MC(up/down) = 0.62^{+0.19}_{-0.14} (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 muon neutrino and muon anti-neutrino interactions are separated. The ratio of muon neutrino to muon anti-neutrino events in the data is compared to the Monte Carlo expectation assuming neutrinos and anti-neutrinos oscillate in same manner giving: R_data(numubar/numu)/R_MC(numubar/numu) = 0.96^{+0.38}_{-0.27} (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 muon neutrinos and muon anti-neutrinos.

Item Type: Article
Additional Information: I am one of two calibration co-ordinators for the entire USD 200 M experiment, with responsibility for the overall energy calibration of the MINOS detectors, a crucial ingredient in the main neutrino oscillation measurement. Authorship of this paper extends to the entire MINOS collaboration.
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Subjects: Q Science > QC Physics
Depositing User: Elisabeth Falk
Date Deposited: 06 Feb 2012 19:50
Last Modified: 07 Mar 2017 05:38
URI: http://srodev.sussex.ac.uk/id/eprint/22477

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