Neutrino Beam MC We propose to adopt ‘jnubeam’ as the official T2K code for flux calculation. –It is well established and almost ready for flux calculation except for some missing geometry. –Fluxes for ND280 and Super-K are already distributed as ‘07a’. Both nu and anti-nu. The beam group will take the responsibility to maintain the code, do necessary upgrades and to distribute the neutrino flux files. It is managed by a CVS server at KEK. This is very convenient for us, so we want to keep the server at KEK. The version is now tagged like ’07a’. We can follow the GANG guideline for gagging if necessary.

Task lists Minimal In addition to mass production and version control, –Geometry update (within ’09?) Striplines are missing. –NA61 inclusion (w/ NA61-T2K group) –Error estimation for flux and/or far-to-near extrapolation. Integration of the Information from NA61, primary beam monitor, alignment of the beamline equipment, MUMON, INGRID is necessary. –Define variables to be attached to each event In future? – Framework update? (C++ w/ GEANT3, Geant4) If there are rational reasons.

Working group Beam MC sub-working group will be made under the beam group. Maybe during the next pre-meeting, we can have a meeting to establish this sub group and make a mailing list to share information.

supplement

T2K Flux 07a A. K. Ichikawa

Main Changes since 04a Decay Volume was shortened from 130m to 110m. Target diameter was reduced from 30mm to 26mm. Realistic geometry of the Target Station He chamber is incorporated.

 Flux at Super-K Ep = 30GeV, Off-Axis 2.5 degree. 5yr = 8.33E21 POT, which corresponds to 5E21 POT at 50GeV.  anti   e anti- e

anti-  Flux at Super-K Ep = 30GeV 5yr = 8.33E21 POT, which corresponds to 5E21 POT at 50GeV. anti-   anti- e e anti-  flux with opposite horn polarity  flux with nominal horn polarity

Comparison with 04a 04a(40GeV) 07a The peak is decreased by 10%. The origin of this decrease was checked and it is found that it dominantly comes from shorter decay volume.