y(4260), z(3900), x(3872)

 https://blog.sina.com.cn/s/blog_486d3cd80101awxe.html (2013-04-17 23:15:28)  

the recent discovery of bes at bepc can be understood by using 4-quark states:   

y(4260) is composed of (cs, c-bar s-bar);

z(3900) is (cq, c-bar q-bar), where q stands for up or down quark, qq-bar forms an isospin triplet;

then x(3872) is (cq, c-bar q-bar), where qq-bar forms an isospin singlet. 

mass differences:

m(y4260) - m(z3900) = 2 m_s, (so m_s =180),

m(z3900) - m(x3872) = 30, which is just the isospin triplet-singlet splitting. 

being an isospin triplet, z(3900) can decay into j/psi and a pion. 

it is predicted there exist states (4080), charmonia with strangeness:

(4080) is (cq, c-bar s-bar) or (cs, c-bar q-bar),

it will decay into j/psi and a kaon.  is it the recent discovered y(4140)? 

for bottom systems, by taking m_b - m_c = 3400, we predict

(bs, b-bar s-bar), mass is 11060;

(bq, b-bar s-bar), mass is 10880;

(bq, b-bar q-bar) w/ isospin triplet, mass is 10700,

it should be the experimentally z_b(10650);

(bq, b-bar q-bar) w/ isospin singlet, mass is 10672,

the real value maybe lower, like 10620 or lower. 

 a theory point: 

in a four-quark system, there exists the heavy quark spin symmetry.  QQ-bar is expected to have spin-1.   

further predictions,

y(4260) mainly decays to j/psi + eta, it can also decay to d_s + d_s* mesons;

x(3872) can decay to j/psi + eta;

if i call the above discovered states j/psi-like (namely QQ-bar spin-1), there maybe eta_c-like 4 quark states (QQ-bar spin-0), which are almost degenerate to the one j/psi-like.  

oringinally i thought x(3872) is a molecular state, now this seems unnecessary， as a molecular state, it is hard to understand its production rate, as k.t. always worried. 

it is really fun to do kindergarden physics! let me know my mistakes so i will make corrections.