Search for nucleon decay into lepton + K0 final states using Soudan-2

A search for nucleon decay into two-body final states containing K^0 mesons has been conducted using the 963 metric ton Soudan 2 iron tracking calorimeter. The topologies, ionizations, and kinematics of contained events recorded in a 5.52 kiloton-year total exposure (4.41 kton-year fiducial volume exposure) are examined for compatibility with nucleon decays in an iron medium. For proton decay into the fully visible final states \mu^+K^0_s and e^+K^0_s, zero and one event candidates are observed respectively. The lifetime lower limits (\tau /B) thus implied are 1.5 \times 10^{32} years and 1.2 \times 10^{32} years, respectively. Lifetime lower limits are also reported for proton decay into l^+K^0_l, and for neutron decay into \nu K^0_s.Comment: 51 pages, including 5 tables and 14 figures; updated text and tables; accepted for publication in Physical Review

Observation of a shadow of the Moon in the underground muon flux in the Soudan 2 detector

A shadow of the Moon, with a statistical significance of 5 σ, has been observed in the underground muon flux at a depth of 2090 mwe using the Soudan 2 detector. The angular resolution of the detector is well described by a Gaussian with a sigma ≤0.3°. The position of the shadow confirms that the alignment of the detector is known to better than 0.15° and has remained stable during ten years of data taking. ©2000 The American Physical Society

Search for nucleon decay into lepton+K-0 final states using Soudan 2

A search for nucleon decay into two-body final states containing K0 mesons has been conducted using the 963 metric ton Soudan 2 iron tracking calorimeter. The topologies, ionizations, and kinematics of contained events recorded in a 5.52 kiloton-year total exposure (4.41 kton-year fiducial volume exposure) are examined for compatibility with nucleon decays in an iron medium. For proton decay into the fully visible final states μ+KS0 and e+KS0, zero and one event candidates are observed respectively. The lifetime lower limits (τ/B) thus implied are 1.5×1032 yr and 1.2×1032 yr, respectively. Lifetime lower limits are also reported for proton decay into l+K10, and for neutron decay into vKS0. ©2000 The American Physical Society

Search for the proton decay mode p ->nu K+ in Soudan 2

We have searched for the proton decay mode p → ν K+ using the one-kiloton Soudan 2 high resolution calorimeter. Contained events obtained from a 3.56 kiloton-year fiducial exposure through June 1997 are examined for occurrence of a visible K+ track which decays at rest into μ+ ν or π+ π0. We found one candidate event consistent with background, yielding a limit, τ/B(p → ν K+) > 4.3 × 1031 years at 90% CL with no background subtraction. © 1998 Published by Elsevier Science B.V. All rights reserved