Dear collaborators,

I am posting the final version of my Ph.D. thesis.  The title and
abstract are given below.


Regards,

Hosai Nakada
University of Tsukuba


   Measurement of the Diffractive Structure Function
   of the Antiproton in 1.8-TeV Proton-Antiproton Collisions

We present the measurement of the diffractive structure function
of the antiproton in proton-antiproton collisions at the center-of-mass energy
of 1.8 TeV. The data were collected during the 1995-1996 Tevatron
collider run using the Collider Detector at Fermilab~(CDF).
Diffractive events are characterized by the recoil $\bar{p}$
and the forward rapidity gap in the fnal state.
In order to tag the recoil $\bar{p}$, we installed a Roman-pot type
antiproton spectrometer~(RPS), and using the forward calorimeter and
the beam-beam counter, we identify the rapidity gap.
In order to identify a hard collision, we require the presence of two
or more jets.
In this analysis, we calculate the hard scale in the interaction~($Q^2$),
the momentum fraction of antiproton carried by struck parton~($\xpb$), and
the fractional momentum of the struck parton in the exchanged object~($\beta$).

We obtained the diffractive structure function
as a function of $\beta$ and $Q^2$ in the kinematic region of
$0.035\leq\xi\leq 0.095$ and $|t|\leq 1$ GeV${}^2$.
We observe no $Q^2$ dependence
in the diffractive structure function of the antiproton
in the $Q^2$ region measured in this study.
This is consistent with the H1 result at HERA $ep$ collider experiment.
The absolute value of the diffractive structure function measured at CDF
is smaller than that of the H1 result by, approximately, a factor of 1/7.
The discrepancy is also observed in other results at CDF such as
the diffractive W and b-quark production where the cross section
is about 20\% of the prediction using the Donnachie-Landshoff pomeron flux.
These results suggest that the diffractive cross section is not described
by using the universal diffractive structure function of the antiproton.






Posted to /cdf/pub/thesis/cdf5589_sd_struct_thesis.ps
    http://www-cdf.fnal.gov/thesis/cdf5589_sd_struct_thesis.ps

Posted by hosai@cdfsga