FERMILAB-PUB-77-149-E

yor diffraction disscciation events the    "1gX*S    of the
secondary charge parti~nea must satisfy
4i( 4   A1/                            (
where   A  is a nucleus mass nwuber. This condition is    eces-
sary but not sufficient because some part of quasifree proton
nucleon interactions are satisfied to the condition ( 2 ).
Below we described t'e selecting method of coherent disoci-
ation reactions which is exactly the Mae method as we used
2/ and          00     3/
pig.1-shows for example distributions of a gqality
$       s ei  in "clear" and background 3- end 5-proUg
events of the type 0 + 0 +3      and 0 + 0 + 5. he backgouad
sample contains events with the 3    -electrons and events
which hare been "prepared" from stars of type 1 + 0 + As,
0 + 1 e n9   end 0 + 0 + (n+ 1)     (ns 3 or 5) by subtracting
the trock of a recoil proton.
The subtraction of background distributions by a aetbod
~tla the .f ree parameter ~ max   /1,2/ leans to the following
reanIts for reactions ( 1 ) with n, " 3 or 5
-(n  ---   _   ('i) robfflflelrkif
L                         c/ ooh, m         coh,
--      ------ -- -
3  5  10      22 +              9.4  2.7
..~~~~~~~~ ~ ~ ~ ~ ,.  -9 60*5  ._'....:    _   .

fe differasce between angular distributions for "clean"
sad backgonad events,enalogical to that shown in Jig.1.,is
sea. for n a 1 end 7 as well. An sna.ysis (at a a 1 we have
int3tdias the 15% correction due the loss of one-prong ashe-
vact reations at the so-ning end in the "elastic" region
(  <0.o01-) gives te values .   h a 8.6 (1 30%) ab/vasleas
and 6 c      1.6 (  70M) ab/nualsus.
The contribution of coherent reactions ( 1) to the multi-
plialty distribution of quesifree proton-nuleon events in
emulsion is shorn in J1g.2.
ig.3 shows the energy dependences of topological cross
sections in coherent reactions ( 1 ). The data at 20 - 200 Gov
are taken from the review 'article /
One can conclude:
1. The total and topological cross sections of coherent W1ff-
raestive dissociation oft nuclei increase in the range 20 - 400
0evs the total cross section in particular increases front 8
up to '. 25 ab/nuoleus.
8. This growth is the nost fast for anultiprong channels.Tek-
tag into acoount the fact that the cross sections for exclusive
channels in inelastic diffraotion ( for the channel P   P.T+  -
for example ) does not increase with the energ/23,4/, we
conclude that the increase of +opological cross sections is
connected mainly with the ppening channels of higher mrltipli-
oity of neutral secondary particles. In other words, we can
say that the increase of eos. sections happens due to the

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