550 10 Particle Physics – II
(a)π^0 π^0
(b)π+π+
(c)π+π−
(d)Λπ^0
(e)Σ^0 π^0
(f)π−π−?10.2.3 Quarks...........................................
10.44 Describe the phenomena when a quark is struck by a high energy electron
with a high enough momentum transfer.
10.45 The B−meson is the lightest particle consisting of a b quark anduantiquark.
Which type of interaction causes its decay. Describe with explanation its
decay chain.
10.46 The 3γdecay of positronium (the bound state ofe+e−) has a width that in
QED is predicted to beΓ(3γ)=2(π^2 −9)α^6 mec^2 / 9 π, whereαis the fine
structure constant.
(a) If the hadronic decay of the ccbound state J/ψ(3,100) proceeds via an
analogous mechanism, but involving three gluons, use the experimental
hadronic width (fragmentation into hadrons occurring with probability
unity)Γ(3g)=80 keV to estimate the effective strong interaction cou-
pling constantαs.
(b) Determineαsfrom the radiative widthΓ(ggγ) = 0 .16 keV of the bb
bound stateγ(9,460)
10.47 Calculate the ratioRof the cross section fore+e−→QQ→hadrons to that
for the reactione+e−→μ+μ−as a function of increasing CMS energy up
to 400 GeV. Assume the quark masses in GeV/c^2 up or down 0.31, strange
0.5, charm 1.6, bottom 4.6 and top 175.
10.48 Show that the quark model predicts the following cross-section relation
σ(Σ−n)=σ(pp)+σ(K−p)−σ(π−p)10.49 Using the additive quark model the total interaction cross-section is assumed
to result from the sum of the cross-sections of various pairs. Assuming that
σ(qq)=σ(qq) prove the relationσ(Λp)=σ(pp)+σ(K−n)−σ(π+p)
10.50 The coulomb self- energy of a hadron with charge+eor−eis about 1 MeV.
The quark content and rest energies (in MeV)of some hadrons are
n(udd)940,p(uud)938,Σ−(dds)1197,Σ^0 (uds)1192,Σ+(uus)1189,
K^0 (ds)498,K+(us)494
Theuanddquarks make different contribution to the rest energy. Estimate
this difference.