A simulation study for a Forward Calorimeter upgrade plan in ALICE at LHC

We plan to install a Forward Calorimeter(FoCAL) in $\eta$=1~4 region of the ALICE experiment at LHC. A main subject is the search for signatures of small-x parton saturation effects, which is recently discussed from the point of Color Glass Condensate(CGC). It also enables to study long range hadron correlations like ``Ridge'' found in the AuAu collision at RHIC. The basic measurements are $\pi^{0}$ and direct $\gamma$ spectrums in p+p, p+A, and A+A collisions. Since two $\gamma$ from a high momentum $\pi^{0}$ decays are merged into a same cluster, $\pi^{0}$/$\gamma$ separation at high momentum is a challenging task. The measurement of single electron from heavy quarks and W boson is also possible in p+p,p+A collisions. A SiW Tracking Calorimeter can be the solution to theses requirements. It is a sampling calorimeter which measures a presice lateral and longitudinal shower shape by a set of silicon sensors. A tungsten is a good choice for absorber material because of its short radiation length and excellent ratio of radiation and absorption lengths. A simulation study for possible physics will be presented. And then the conceputual design of FpCal and its performance study by a GEANT simulation and a beamtest of PHENIX Forward Calorimeter protoype will be also presented.