اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدImproved search for muon-neutrino to electron-neutrino oscillations in MINOS
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We report the results of a search for $ u_{e}$ appearance in a $ u_{mu}$ beam in the MINOS long-baseline neutrino experiment. With an improved analysis and an increased exposure of $8.2times10^{20}$ protons on the NuMI target at Fermilab, we find that $2sin^2(theta_{23})sin^2(2theta_{13})<0.12 (0.20)$ at 90% confidence level for $deltamathord{=}0$ and the normal (inverted) neutrino mass hierarchy, with a best fit of $2sin^2(theta_{23})sin^2(2theta_{13}),mathord{=},0.041^{+0.047}_{-0.031} (0.079^{+0.071}_{-0.053})$. The $theta_{13}mathord{=}0$ hypothesis is disfavored by the MINOS data at the 89% confidence level.
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The MINOS experiment ran from 2003 until 2012 and collected a data sample including 10.71x10^20 protons-on-target (POT) of beam neutrinos, 3.36x10^20 POT of beam antineutrinos and an atmospheric neutrino exposure of 37.88 kt-yrs. The final measuremen
t of the atmospheric neutrino oscillation parameters, dm^2_32 and theta_23, came from a full three flavour oscillation analysis of the combined CC nu_mu and CC anti-nu_mu beam and atmospheric samples and the CC nu_e and CC anti-nu_e appearance samples. This analysis yielded the most precise measurement of the atmospheric mass splitting dm^2_32 performed to date. The results are |dm^2_32|=[2.28 - 2.46]x10^-3 eV^2 (68%) and sin^{2}theta_23=0.35-0.65$ (90%) in the normal hierarchy, and |dm^2_32|=[2.32 - 2.53]x10^-3 eV^2 (68%) and sin^{2}theta_23=0.34-0.67 (90%) in the inverted hierarchy. The successor to MINOS in the NOvA era at FNAL, MINOS+, is now collecting data mostly in the 3-10 GeV region, and an analysis of nu_mu disappearance using the first 2.99x10^20 POT of data produced results very consistent with those from MINOS. Future data will further test the standard neutrino oscillation paradigm and allow for improved searches for exotic phenomena including sterile neutrinos, large extra dimensions and non-standard interactions.
Data from the MINOS experiment has been used to search for mixing between muon neutrinos and muon antineutrinos using a time-independent Lorentz-violating formalism derived from the Standard-Model Extension (SME). MINOS is uniquely capable of searchi
ng for muon neutrino-antineutrino mixing given its long baseline and ability to distinguish between neutrinos and antineutrinos on an event-by-event basis. Neutrino and antineutrino interactions were observed in the MINOS Near and Far Detectors from an exposure of 10.56$times10^{20}$ protons-on-target from the NuMI neutrino-optimized beam. No evidence was found for such transitions and new, highly stringent limits were placed on the SME coefficients governing them. We place the first limits on the SME parameters $(c_{L})^{TT}_{mumu} $ and $(c_{L})^{TT}_{tautau}$ at $-8.4times10^{-23} < (c_{L})^{TT}_{mumu} < 8.0times10^{-23}$ and $-8.0times10^{-23} < (c_{L})^{TT}_{tautau} < 8.4times10^{-23}$, and the worlds best limits on the $tilde{g}^{ZT}_{muoverline{mu}}$ and $tilde{g}^{ZT}_{tauoverline{tau}}$ parameters at $|tilde{g}^{ZT}_{muoverline{mu}}| < 3.3times 10^{-23}$ and $|tilde{g}^{ZT}_{tauoverline{tau}}| < 3.3times 10^{-23}$, all limits quoted at $3sigma$.
The MINOS/MINOS+ experiment has recently reported stringent limits on $ u_mu$ disappearance that appear to rule out the 3+1 sterile neutrino model. However, in this paper we wish to point out problems associated with the MINOS/MINOS+ analysis. In par
ticular, we find that MINOS/MINOS+ has either underestimated their systematic errors and/or has obtained evidence for physics beyond the 3-neutrino paradigm. Either case would invalidate the limits on $ u_mu$ disappearance.
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