Role of nonspectator interactions in charm and bottom decays Page: 3 of 6
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For T(D+)/n(Do) m 10 we find n(F+)(D+) 0.4- 0.5, in good agroe.oent
with present data.
We note that since Ino- ldon diagrams do not contribute to de-
cays to leptons, the semioeptonic branching fractions into electrons
are in the same ratios as the lifetimes in the one-gluon model.
However, if mutiple gluon emission is important, then the semilep-
ronic branching fraction of the F+ could be enhanced by the annihila-
tion interaction cs+ eha + gluons.
(b) Inclusive 0-0 decavs: We now turn to inclusive Cahlhbo
suppressed AS=0 decays; i.e., transitions in which the final state
has the same strangeness as the initial state. In the spectator
model the branching fractions foi these decays are the same for the
D0, D+ and F+, with B(AS- 0) .8%. Including exchange interactons,
ne find that tS=0 branching ratios are slightly increased to 8-10%
for the D, whereas lot the F+ B(AS=0) is constrained to lie in the
range 4-8%.+
For the D, nonspectator interactions contribute only to Cabibbo
suppressed decays, and can lead to a significant enhanc mcn of the
A0= 0 branching fraction, In the one-gluon model with Be(D )- 0.22
and n(D+)T(0O) = 5 and 10, we find B(O+,AS- 0) - 17 and 17% respec-
tivly. There is some indication from the measured B(D- 1K) that
the AS- 0 branching fraction for the D+ is enhanced.
(c) F' aultipion decay modes; In F+ decays the spectator
transition cs+ ssud will give final states with either overt or hid-
den strangeness (e.g., F*+K'K+X+ or F++ nX+). Nonresonant multipion
final states are not expected at a significant level. The situation
is markedly different with the nonspectator transition es+ud+gluon(s),
where states of three or more pions ire anticipated. The branching
fraction for this transition with no s or s quarks originating from
the weak interaction can be estiaated in the one-gluon model. We
ohtnin B(F+ + no a or q) - (25-30)%. Since 5u or dd pair creation in
favored over is, the uag final state will evolve mainly into mults-
pion or plus pions modes. Although we are unable to separate the
relative proportion, phase space considerations suggest that the mul-
ripion states will predominate. In this connection it is interesting
to note that several F-a wm+n-no events have now been observed.
(d) The "color sn1pression" puzzle: The spectator model pre-
dicts B(D+ KOno)/B(DO+K-+)= 0.05, whereas observed rates for these
modes are Boo- 2.0 0.9%, B-+- 2.8 t 0.6%. Nonspectator interaction
offer a way out of this discrepancy. This is because gluon-enhanced
exchange diagrams give amlitudes in which there is no color auppres-
sion factor between, the K eo and K ' modes. Hence adding spectator
and exchange contributions, we are simply left with an isopin trian-
gle inequality on the Ko n branching fraction
Sl(B ) - (Bo+o+ 2 Boo +h +)+ (Bo+ )' +7 02
where To,T+ denote the DO,D+ lifetimes. Using the experimental
values B += 2.8 0.6% and Bo+= 2.1 0.4%, and taking T+ /T5, we
find the numerical bounds
0.5 0.2% s Bn0 s 2.7 0.5% -
These bracket nicely the experimental value Boo- 2.01 0.9%.
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Barger, V.; Leveille, J.P. & Stevenson, P.M. Role of nonspectator interactions in charm and bottom decays, article, August 1, 1980; United States. (https://digital.library.unt.edu/ark:/67531/metadc1057752/m1/3/: accessed April 17, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.