It's still in the listings. Although they keep changing their minds on the pole mass, and hence changing the name every few years. I would say that in general it is simply ignored; many physicists have simply decided to move on. Personally, I find it to be quite possibly an important factor in my own work. f0(600) may well be a member of a light scalar SU(3) nonet, as opposed to replacing f0(1370) as the lighter isosinglet in the 1(3)P0 multiplet. The possibility of having two scalar multiplets in the ground state is very interesting, and essentially indicates that the scalars occur at two poles. The well established members of the 1(3)P0 nonet in SU(3) are;
I = 0 f0(1370), f0(1710)
I = 1 a0(1450)
I = 1/2 K*0(1430)
The other potential members at this time are;
I = 0 f0(600), f0(980)
I = 1 a0(980)
I = 1/2 k(800)
It is interesting to note several things here:
1) f0(980) and a0(980) represent one of the largest breakings of isospin symmetry ever found (until this latest find of X(3872) out of KEK);
2) by taking the masssquared pole positions of the isospin groups (i.e. f0(600) and f0(1370), f0(980) and f0(1710), a0(980) and a0(1450), k(800) and K*0(1430)), you find mass poles that fit in the standard resonance pattern of the 1P spin triplets, i.e. 1(3)P0 mesons (poles) are lighter than 1(3)P1 mesons, which are lighter than 1(3)P2 mesons, all in appropriate sized steps;
3) with a quick and crude calculation, the poles for the isoscalar members (I=0) occur just above 980 MeV (within about 78 MeV) and just above 1370 MeV (within about 24 MeV), possibly indicating that the f0(980) and f0(1370) are fairly pure states as they are, and placing them as the light and heavy isoscalars respectively of a scalar pole multiplet;
4) f0(980) and a0(980) have been postulated as possible candidates for KKbar bound states in the past, and now with the find of X(3872) as a possible D*Dbar candidate this possibility is all the more realistic.
Alot of the answers to the mystery of the scalars may in fact hinge on the interpretation of f0(600).
