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تسجيل مستخدم جديدSearch for nucleon decay into charged antilepton plus meson in 0.316 megaton$cdot$years exposure of the Super-Kamiokande water Cherenkov detector
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We have searched for proton decays into a charged antilepton ($e^+$, $mu^+$) plus a meson ($eta$, $rho^0$, $omega$) and neutron decays into a charged antilepton ($e^+$, $mu^+$) plus a meson ($pi^-$, $rho^-$) using Super-Kamiokande (SK) I-IV data, corresponding to 0.316 megaton$cdot$years of exposure. This measurement updates the previous published result by using 2.26 times more data and improved analysis methods. No significant evidence for nucleon decay has been observed and lower limits on the partial lifetime of the nucleon are obtained. The limits range from 3$times$10$^{31}$ to 1$times$10$^{34}$ years at 90% confidence level, depending on the decay mode.
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A search for proton decay into three charged leptons has been performed by using 0.37$,$Mton$cdot$years of data collected in Super-Kamiokande. All possible combinations of electrons, muons and their anti-particles consistent with charge conservation
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Searches for a nucleon decay into a charged anti-lepton (e^+ or {mu}^+) plus a light meson ({pi}^0, {pi}^-, {eta}, {rho}^0, {rho}^-, {omega}) were performed using the Super-Kamiokande I and II data. Twelve nucleon decay modes were searched for. The t
otal exposure is 140.9 kiloton cdot years, which includes a 91.7 kiloton cdot year exposure (1489.2 live days) of Super-Kamiokande-I and a 49.2 kiloton cdot year exposure (798.6 live days) of Super-Kamiokande-II. The number of candidate events in the data was consistent with the atmospheric neutrino background expectation. No significant evidence for a nucleon decay was observed in the data. Thus, lower limits on the nucleon partial lifetime at 90% confidence level were obtained. The limits range from 3.6 times 10^31 to 8.2 times 10^33 years, depending on the decay modes.
As a baryon number violating process with $Delta B=2$, neutron-antineutron oscillation ($ntobar n$) provides a unique test of baryon number conservation. We have performed a search for $ntobar n$ oscillation with bound neutrons in Super-Kamiokande, w
ith the full data set from its first four run periods, representing an exposure of 0.37~Mton-years. The search used a multivariate analysis trained on simulated $ntobar n$ events and atmospheric neutrino backgrounds and resulted in 11 candidate events with an expected background of 9.3 events. In the absence of statistically significant excess, we derived a lower limit on $bar n$ appearance lifetime in $^{16}$O nuclei of $3.6times{10}^{32}$ years and on the neutron-antineutron oscillation time of $tau_{ntobar n} > 4.7times10^{8}$~s at 90% C.L..
We have searched for proton into muon plus neutral kaon using data from a 91.7 kiloton-year exposure of Super-Kamiokande-I, a 49.2 kiloton-year exposure of Super-Kamiokande-II, and a 31.9 kiloton-year exposure of Super-Kamiokande-III. The number of c
andidate events in the data was consistent with the atmospheric neutrino background expectation and no evidence for proton decay in this mode was found. We set a partial lifetime lower limit of 1.6x10^33 years at the 90% confidence level.
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