1. Velocity of light in water
Simple Method MC
Data

2. Method (Led run)

3. Method From Led run (time and position for each OM)
Time = Peak (highest bin, bin size=0.5 ns)
Position = nominal OM position
Eliminate not significant peak
(Noise>Peak-5*sqrt(peak))
Time versus distance
Fit y=ax+b

4. Plot MC Take time from bin with maximal hits = Timepeak
Timepeak versus distance
n=v_vacuum/v_measured

5. MC (Led) Run Absorption Scattering Fit range n delta n
Inf

6. MC (Laser) Led and Laser runs slightly dependent from fit range
Run Absorption Scattering Fit range n delta n
Led and Laser runs slightly dependent from fit range
Fit over full range no dependence of absorption and scattering
Led run n =
Laser run n =
Ciro put in the MC:
Led run n =
Laser run n =
Ciro can you please generate MC with n=1.3 and n=1.5 ???

7. MC (different Lines)

8. Thinking about errors Laser (full width 0.8 ns) Led (full width 4 ns)
=> early photon effect maximum 4 ns
Walk effect (is smaller than 4ns)
Binning in histogram 0.5ns
Positioning (possible 20 cm = 1ns)
We measure times of 1000 ns => accuracy of the measurement around 0.5%

9. Data (Do we crosscheck Pacos timing calibration?)

10. Data (different fit range)
Error in t=2 ns, error in position x=1m
Run fit rang[m] n delta n chi/ndf
/38
/19
/17

11. Data (Different Lines) We crosscheck Pacos timing calibration)

12. Data (different Lines)
Run Line n delta n chi/ndf
/38
/49
/47
/39

13. Data (different runs) Run Line n delta n chi/ndf
/38
/38
/36
/38
/35
/43
/41
/39
/42
36063UV /30

14. Is this useful? Only cross check of Pacos work?
Improvement:Take real OM positions
Define fit range (systematic bias)
Method ok?
Have a look to Laser runs