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تسجيل مستخدم جديدConstraints on Oscillation Parameters from $ u_e$ Appearance and $ u_mu$ Disappearance in NOvA
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Results are reported from an improved measurement of $ u_mu rightarrow u_e$ transitions by the NOvA experiment. Using an exposure equivalent to $6.05times10^{20}$ protons-on-target 33 $ u_e$ candidates were observed with a background of $8.2pm0.8$ (syst.). Combined with the latest NOvA $ u_mu$ disappearance data and external constraints from reactor experiments on $sin^22theta_{13}$, the hypothesis of inverted mass hierarchy with $theta_{23}$ in the lower octant is disfavored at greater than $93%$ C.L. for all values of $delta_{CP}$.
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We present updated results from the NOvA experiment for $ u_murightarrow u_mu$ and $ u_murightarrow u_e$ oscillations from an exposure of $8.85times10^{20}$ protons on target, which represents an increase of 46% compared to our previous publication.
The results utilize significant improvements in both the simulations and analysis of the data. A joint fit to the data for $ u_mu$ disappearance and $ u_e$ appearance gives the best fit point as normal mass hierarchy, $Delta m^2_{32} = 2.44times 10^{-3}{{rm eV}^2}/c^4$, $sin^2theta_{23} = 0.56$, and $delta_{CP} = 1.21pi$. The 68.3% confidence intervals in the normal mass hierarchy are $Delta m^2_{32} in [2.37,2.52]times 10^{-3}{{rm eV}^2}/c^4$, $sin^2theta_{23} in [0.43,0.51] cup [0.52,0.60]$, and $delta_{CP} in [0,0.12pi] cup [0.91pi,2pi]$. The inverted mass hierarchy is disfavored at the 95% confidence level for all choices of the other oscillation parameters.
The MiniBooNE experiment at Fermilab reports results from an analysis of the combined $ u_e$ and $bar u_e$ appearance data from $6.46 times 10^{20}$ protons on target in neutrino mode and $11.27 times 10^{20}$ protons on target in antineutrino mode.
A total excess of $240.3 pm 34.5 pm 52.6$ events ($3.8 sigma$) is observed from combining the two data sets in the energy range $200<E_ u^{QE}<1250$ MeV. In a combined fit for CP-conserving $ u_mu rightarrow u_e$ and $bar{ u}_{mu}rightarrowbar{ u}_e$ oscillations via a two-neutrino model, the background-only fit has a $chi^2$-probability of 0.03% relative to the best oscillation fit. The data are consistent with neutrino oscillations in the $0.01 < Delta m^2 < 1.0$ eV$^2$ range and with the evidence for antineutrino oscillations from the Liquid Scintillator Neutrino Detector (LSND).
We performed an improved search for $ u_mu to u_e$ oscillation with the KEK to Kamioka (K2K) long-baseline neutrino oscillation experiment, using the full data sample of $9.2 times 10^{19}$xspace protons on target. No evidence for a $ u_e$ appearanc
e signal was found, and we set bounds on the $ u_mu to u_e$ oscillation parameters. At $Delta m^2$ = $2.8 times 10^{-3} mathrm{eV}^2$, the best fit value of the K2K $ u_mu$ disappearance analysis, we set an upper limit of $sin^2 2theta_{mu e}$ $<$ 0.13 at 90% confidence level.
We report on measurements of neutrino oscillation using data from the T2K long-baseline neutrino experiment collected between 2010 and 2013. In an analysis of muon neutrino disappearance alone, we find the following estimates and 68% confidence inter
vals for the two possible mass hierarchies: Normal Hierarchy: $sin^2theta_{23}=0.514^{+0.055}_{-0.056}$ and $Delta m^2_{32}=(2.51pm0.10)times 10^{-3}$ eV$^2$/c$^4$ Inverted Hierarchy: $sin^2theta_{23}=0.511pm0.055$ and $Delta m^2_{13}=(2.48pm0.10)times 10^{-3}$ eV$^2$/c$^4$ The analysis accounts for multi-nucleon mechanisms in neutrino interactions which were found to introduce negligible bias. We describe our first analyses that combine measurements of muon neutrino disappearance and electron neutrino appearance to estimate four oscillation parameters and the mass hierarchy. Frequentist and Bayesian intervals are presented for combinations of these parameters, with and without including recent reactor measurements. At 90% confidence level and including reactor measurements, we exclude the region: $delta_{CP}=[0.15,0.83]pi$ for normal hierarchy and $delta_{CP}=[-0.08,1.09]pi$ for inverted hierarchy. The T2K and reactor data weakly favor the normal hierarchy with a Bayes Factor of 2.2. The most probable values and 68% 1D credible intervals for the other oscillation parameters, when reactor data are included, are: $sin^2theta_{23}=0.528^{+0.055}_{-0.038}$ and $|Delta m^2_{32}|=(2.51pm0.11)times 10^{-3}$ eV$^2$/c$^4$.
The T2K collaboration reports a precision measurement of muon neutrino disappearance with an off-axis neutrino beam with a peak energy of 0.6 GeV. Near detector measurements are used to constrain the neutrino flux and cross section parameters. The Su
per-Kamiokande far detector, which is 295 km downstream of the neutrino production target, collected data corresponding to $3.01 times 10^{20}$ protons on target. In the absence of neutrino oscillations, $205 pm 17$ (syst.) events are expected to be detected and only 58 muon neutrino event candidates are observed. A fit to the neutrino rate and energy spectrum assuming three neutrino flavors, normal mass hierarchy and $theta_{23}leq pi/4$ yields a best-fit mixing angle $sin^2(2theta_{23})=1.000$ and mass splitting $|Delta m^2_{32}| =2.44 times 10^{-3}$ eV$^2$/c$^4$. If $theta_{23}geq pi/4$ is assumed, the best-fit mixing angle changes to $sin^2(2theta_{23})=0.999$ and the mass splitting remains unchanged.
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