1. overview of what is in the MC A.Margiotta 17/05/2011

2. Relevant water properties to our MC absorption length scattering length volume function refraction index : refr_index @ 460 nm n group = 1.3499 (=n phase ) + 0.0298 =1.3797 effective scattering length effective attenuation length

3. absorption length max (@470nm) = 55 m in “OFFICIAL” simulations (dec08 photon tables) : ** RBR v0.1 ** Aart “SoS approach” published value in Astrop. Phys. 23 (2005) 131 ≈ 60 m

4. scattering length scattering coeff. b = 1/λ calculated from Kopelevich param. λ sct = 52.8 m @ 460 nm Model: partic-0.0075 v s =v l = 0.0075 ppm

5. scattering function β (θ) = ηβ Ray (θ) + (1 –η) β part (θ) η = 17 % λ sct = 52.8 m  λ sct eff = 230 m @ 460 nm β Ray molecular scattering β Ray (θ) = 0.06225 * ( 1+0.835 cos(θ)) β par particulate scattering is provided with a table 〈 cosθ 〉 = 0.77

6. attenuation length λ att eff ≈ 44 m @ 460 nm

7. they are used in: Geasim : light from particles in showers NC and CC interactions NO SCATTERING KM3 package (GEN code) : light from muons (track and e.m. showers)  photon table production SCATTERING NO wavelength dependence of n group WORK IN PROGRESS : KM3 v4rx (see Corey’s talk)

8. impact Reliable input values are essential Δ λ abs =+/- 10%  Δreco_tracks around 20% old study on scattering models indicates important effect on zenith angle distribution waiting ……..