  Measurements of diffractive dissociation cross sections in pp collisions at
sqrt(s) = 7 TeV are presented in kinematic regions defined by the masses M[X]
and M[Y] of the two final-state hadronic systems separated by the largest
rapidity gap in the event. Differential cross sections are measured as a
function of xi[X]= M[X]^2/s in the region -5.5 < log[10]xi[X] < -2.5, for
log[10]M[Y] < 0.5, dominated by single dissociation (SD), and 0.5 < log[10]M[Y]
< 1.1, dominated by double dissociation (DD), where M[X] and M[Y] are given in
GeV. The inclusive pp cross section is also measured as a function of the width
of the central pseudorapidity gap Delta eta for Delta eta > 3, log[10]M[X] >
1.1, and log[10]M[Y] > 1.1, a region dominated by DD. The cross sections
integrated over these regions are found to be, respectively, 2.99 +/- 0.02
(stat) +0.32 -0.29 (syst) mb, 1.18 +/- 0.02 (stat) +/- 0.13 (syst) mb, and 0.58
+/- 0.01 (stat) +0.13 -0.11 (syst) mb, and are used to extract total SD and DD
cross sections. In addition, the inclusive differential cross section, d sigma
/d Delta eta[F], for events with a pseudorapidity gap adjacent to the edge of
the detector, is measured over Delta eta[F] = 8.4 units of pseudorapidity. The
results are compared to those of other experiments and to theoretical
predictions, and found compatible with slowly-rising diffractive cross sections
as a function of center-of-mass energy.
