calibrate other model parameters to reproduce the measured results. The free parameters were the PMT photocathode radius for Detector A and the beam height relative to the centre of the detector vessel for Detector B. The beam height in the Detector B was estimated to be located at the centre of the tub with an uncertainty of $\pm$ 1 cm. The optimal beam height was found to be 0.69 $\pm$ 0.05 cm above the centre of the vessel. The optimal photocathode radius of 22 $\pm$ 1 mm is in fair agreement with the manufacturer’s specification of $>$23 mm.

### Wavelength Shifting Model

For ordinary liquid scintillator with a scintillation yield of $10^{4}$ photons per MeV, the number of scintillation photons produced per centimeter for a minimum ionising particle experiencing a stopping power of 2 MeV/cm is $2 \times 10^{4}$. This vastly outnumbers the yield of Cherenkov photons, which is $\approx 600$ photons per centimeter in water integrated over the 200-500 nm spectral range. As more than half of these photons fall in the 200 to 300 nm spectral range, the Cherenkov light accounts $<$1.5% of the detectable light from a minimum ionising particle in ordinary liquid scintillator. WbLS has a 