M_E_M_O_R_A_N_D_U_M for meeting on 16/Jan/2006

Participants:
   Fukuda Hanaki Iio Itahashi Iwasaki Ohnishi 
   Okada Outa Sato Suzuki Tatsuno Yim 

>> Conclusion <<
   DAY-1 (28/Apr deadline -> construction be finished in 3.5 yrs.)
   We take care of SPES-II
                   KAMAE
                   NC wall
   DAY-1 + later
   CDS is an option, and we will support the construction.

>> Detailed discussion Log <<

  What do we require for CDS

X Large solid angle + charged particle measurement will yield something?
  Do we need CDS really?
    Maybe. But just as an Option.

  Main background in Kishimoto san's (K-,n) 1/beta < 1.2=(900 MeV/c incident)
    K- -> K0 in material -> dacay to pi0 -> 2 gamma 
           (K0 -> pi0 pi0 in 31 %)             ^-- gamma misidentified as n
           (K0 -> pi+pi- in 69% and if we identify A charged pion, then we
               can get rid of the bk from pi0pi0. actually this does not 
               require magetic field.) 
  Main Signal Reaction
    (K-,n) = production reaction for S+ (q = 500 MeV/c)

    S+ decay channel to be studied = 
                Sigma+ nn
                Sigma- pp
                Sigma0 pn 
                Sigma0 d (depending on isospin) 
                Lambda d 
                Lambda pn
-----------------------------------------------------------
                Sigma+ -> p pi0  52 %
                          n pi+  48 % 
                Sigma- -> n pi- 100 %
                Sigma0 -> Gamma Lambda 100 %
                Lambda (is to be identified by vertex inconsistency)
                Lambda -> n pi0  33% (chargeless -> blind for us) 
		          p pi-  66%
-----------------------------------------------------------
    X Do we need magnetic field?
          x Magnet + vertices reconstruction will enable us
              Lambda invariant mass measurement.
                 <- Mass (1115.7 MeV) resolution ?
                       p,pi- (q = 100 MeV/c)
                       slow pi/fast pi - separation is needed?
              c.f. Sigma (pi+- q = 190 MeV/c)

          x Lambda + d channel, full reconstruction will be difficult

          x Pion charge can be measured <-- DAY-1 goal?
              pi+ -> Sigma+ (proof of Sigma+ in decay channel)

          If we have magnetic field then,
            pi+ in the formation stage of hyperon may be contaminated,
            the pi+'s can be eliminated by magnetic field?

    in case of (K-,p), we do not need CDS maybe. 
    in case of (K-,n), we may need CDS, because we need to measure 1 vertex. 

X (K-,K+) requirement for CDS?
    2 GeV/c class beamline
    We need to catch two Lambda's same as E906 (Fukuda)

X SPES-II 
  x  Do we really need SPES-II?
     We need to turn around the SPES-II.
     Pivots are located on the bottom.
     20 msr acceptance + +-18% momentum acceptance.
           Central p = 830 MeV/c as max.
              <- too low for (K-,K+) -> please go to SKS for this.

  x  Drastically improved resolution for (K,pi) compared to TOF.
     -> YES. We do take care of SPES-II.

  x  if we requre pi as ejectile, we need Cherenkov's also.
     Aerogel Cherenkov costs very much like 20M Yen depending on the volume.
     Water resistant type Aerogel -> 1.03 for pion detection

  x  2.2 MW Power supply. Power supply for 2.2MW SPES-II spectrometer?

X Budget and Human Resources.