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Register a new userA new analysis of the MiniBooNE low-energy excess
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We present the results of a new analysis of the data of the MiniBooNE experiment taking into account the additional background of photons from $Delta^{+/0}$ decay proposed in arXiv:1909.08571 and additional contributions due to coherent photon emission, incoherent production of higher mass resonances, and incoherent non-resonant nucleon production. We show that the new background can explain part of the MiniBooNE low-energy excess and the statistical significance of the MiniBooNE indication in favor of short-baseline neutrino oscillation decreases from $5.1sigma$ to $3.6sigma$. We also consider the implications for short-baseline neutrino oscillations in the 3+1 active-sterile neutrino mixing framework. We show that the new analysis of the MiniBooNE data indicates smaller active-sterile neutrino mixing and may lead us towards a solution of the appearance-disappearance tension in the global fit of short-baseline neutrino oscillation data.
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The MiniBooNE experiment is a $ u_muto u_e$ and $bar u_mutobar u_e$ appearance neutrino oscillation experiment at Fermilab. The neutrino mode oscillation analysis shows an excess of $ u_e$ candidate events in the low-energy region. These events are analyzed under the SME formalism, utilizing the short baseline approximation. The preliminary result shows the time independent solution is favored. The relationship with the SME parameters extracted from the LSND experiment is discussed. The systematic error analysis and antineutrino mode analysis are outlined.
Using a cleanly tagged data sample of $ u_mu$ charged current events, it is demonstrated that the rate at which such events are mis-identified as $ u_e$s is accurately simulated in the MiniBooNE $ u_mu to u_e$ analysis. Such mis-identification, which could arise from muon internal bremsstrahlung, is decisively ruled out as a source of the low energy electron-like events reported in the MiniBooNE search for $ u_mu to u_e$ oscillations. This refutes the conclusions of a recent paper which postulates that hard bremsstrahlung could form a substantial background to the MiniBooNE $ u_e$ sample.
A sensitive search for anomalous LSND-like nu_mu to nu_e oscillations has been performed by the ICARUS Collaboration exposing the T600 LAr-TPC to the CERN to Gran Sasso (CNGS) neutrino beam. The result is compatible with the absence of additional anomalous contributions giving a limit to oscillation probability of 3.4E-3 and 7.6E-3 at 90% and 99% confidence levels respectively showing a tension between these new limits and the low-energy event excess (200 < E_nu QE < 475 MeV) reported by MiniBooNE Collaboration. A more detailed comparison of the ICARUS data with the MiniBooNE low-energy excess has been performed, including the energy resolution as obtained from the official MiniBooNE data release. As a result the previously reported tension is confirmed at 90% C.L., suggesting an unexplained nature or an otherwise instrumental effect for the MiniBooNE low energy event excess
We revisit a discussion on the impact-parameter dependence of proton-proton elastic scattering amplitude with improved uncertainty calculation. This analysis allows to reveal the asymptotic properties of hadron interactions. New data indicates that the impact-parameter elastic scattering amplitude is slightly above the black disk limit at 13~TeV c.m.s. energy of the LHC reaching a value of $mathrm{Im},H(s,0) = 0.512pm 0.001 text{(sys+stat)} pm 0.004 text{(norm)}$ confirming that black disk limit is violated at current collision energy, however it was not exceeded at 7~TeV. The growth trend of the impact-parameter amplitude imaginary part, extrapolated from previous and new data, indicates that it is unlikely that the amplitude is close to saturation. New analysis is consistent with smooth energy evolution of the elastic scattering amplitude and supersedes the earlier conclusion on the black disk limit excess observed at 7~TeV.
We study the dependence of neutral current (NC) neutrino-induced $pi^0$/photon production ($ u_mu + A to u_mu +1pi^0 / gamma + X$) on the atomic number of the target nucleus, A, at 4-momentum transfers relevant to the MiniBooNE experiment: $Delta$ resonance mass region. Our conclusion is based on experimental data for photon-nucleus interactions from the A2 collaboration at the Mainz MAMI accelerator. We work in the approximation that decays of $Delta$ resonance unaffected by its production channel, via photon or Z boson. $1pi^0+X$ production scales as A$^{2/3}$, the surface area of the nucleus. Meanwhile the photons created in $Delta$ decays will leave the nucleus, and that cross section will be proportional to the atomic number of the nucleus. Thus the ratio of photon production to $pi^0$ production is proportional to A$^{1/3}$. For carbon $^{12}$C this factor is $approx$2.3. MiniBooNE normalises the rate of photon production to the measured $pi^0$ production rate. The reduced neutral pion production rate would yield at least twice as many photons as previously expected, thus significantly lowering the number of unexplained electron-like events.
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