Sterile Neutrino Searches in MiniBooNE and MicroBooNE

Abstract

Tension among recent short baseline neutrino experiments has pointed toward the possible need for the addition of one or more sterile (non-interacting) neutrino states into the existing neutrino oscillation framework. This thesis first presents the motivation for sterile neutrino models by describing the short-baseline anomalies that can be addressed with them. This is followed by a discussion of the phenomenology of these models. The MiniBooNE experiment and results are then described in detail, particularly the most recent antineutrino analysis. This will be followed by a discussion of global fits to world data, including the anomalous data sets. Lastly, future experiments will be addressed, especially focusing on the MicroBooNE experiment and light collection studies. In particular, understanding the degradation source of TPB, designing the TPB-coated plates for MicroBooNE and developing lightguide collection systems will be discussed.We find an excess of events in the MiniBooNE antineutrino mode results consistent with the LSND anomaly, but one that has a different energy dependence than the lowenergy excess reported in neutrino mode. This disagreement creates tension within global fits which include up to three sterile neutrinos. The low-energy excess will be addressed by the MicroBooNE experiment, which is expected to start taking data in early 2015. Tension among existing experiments calls for additional, more decisive future experiments.

Emanation and bulk fluorescence in liquid argon from tetraphenyl butadiene wavelength shifting coatings

“…Over-saturated TPB in polystyrene painted coating on acrylic ("TPB+PS") . This coating resembles the TPB-coated plates of the MicroBooNE experiment, prepared according to the recipe described in [1,24]. To form these coatings a solution of 1 g TPB and 1 g polystyrene is prepared in 50 ml toluene with small addition of ethanol as a surfactant.…”

A model for the Global Quantum Efficiency for a TPB-based wavelength-shifting system used with photomultiplier tubes in liquid argon in MicroBooNE

“…1-σ R Al , 128 nm [13] 0.12 ±0.02 R Stainless , 128 nm [14] 0.35 ±0.05 N LAr , 128 nm [15] 1.45 ±0.07 N LAr , 420 nm [16] 1.23 ±0.002 N Acrylic , 420 nm [16] 1.49 ±0.02 N Glass , 420 nm [17] 1 [20] 0.67 ±0.06 PMT Quantum Efficiency, 87 K [6] 0.153 ±0.008 Table 2: Parameters, with associated uncertainties, considered for the GEANT4 simulation.…”

“…However, the method for coating the plates was not the same -the plates tested were coated evaporatively, while the MicroBooNE plates in our experiments were coated via dipping. A measurement [20] was made to compare the relative efficiencies between the two methods, so we include a factor for this as well.…”

Quasielastic hyperon production in ${{\bar{\nu }}_{\mu }}$-nucleus interactions

“…dσ dQ 2 ) which have large uncertainties due to poor statistics. It is proposed to study these reactions at MINERνA [18], MicroBooNE [19,20] and ArgoNeuT [21,22] experiments. They can also be studied at other neutrino oscillation experiments at SuperK [23], MiniBooNE [24], T2K [25] and NOνA [26].…”

“…Theoretically, these processes have been studied in past for nucleon targets either in quark model [27] or in Cabibbo theory [28] using SU(3)-symmetry of the weak hadronic currents [29][30][31][32][33][34][35][36][37]. No calculation has been made in past to study nuclear medium and final state interactions in these processes and it is only recently that some attempts have been made to study these effects [1,2,8] in view of the ongoing experiments [18][19][20][21][22][23][24][25][26].…”