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vs. @xmath2 topologies for sd@xmath3single diffraction , dd@xmath3double diffraction , dpe@xmath3double pomeron exchange , sdd@xmath3sd@xmath4dpe , and exclusive final state production . the hatched areas in the @xmath5-@xmath2 plots represent regions where particle production occurs.,scaledwidth=70.0% ]    the phenomenal success of the standard model is tainted by our inability to analytically calculate `` soft '' processes , where the strong coupling constant is large and perturbative techniques fail . yet , a fundamental understanding of soft processes may help reveal the underlying mechanism of confinement and explain the intricacies of hadron structure . experimentally , diffractive processes may be used as tools for new discoveries , as they provide low background environments for certain production channels , among which most notable is the exclusive production of higgs bosons ( see sec . [ sec : dijets ] ) . the cdf collaboration has reported several results on soft and hard diffraction processes from @xmath6 collisions at the fermilab tevatron using rapidity gaps and  /  or a leading antiproton as a signature for diffraction ( fig .  [ fig : diffraction ] ) . these results have revealed regularities in the data that point to a qcd picture of diffraction as an exchange of a spin zero color - singlet combination of gluons and  /  or quarks carrying the quantum numbers of the vacuum ( see review in @xcite ) . one result that has attracted widespread attention is the observation of a breakdown of qcd factorization in hard diffractive processes , which is expressed as a suppression by a factor of @xmath7(10 ) of the production cross section relative to theoretical expectations . however , of equal importance is the finding of a breakdown of regge factorization in soft diffraction by a factor of the same magnitude  @xcite . combined , these two results strongly support the hypothesis that the breakdown of factorization is due to a saturation of the probability of forming a rapidity gap by an exchange of a color - neutral construct of the underlying parton distribution function ( pdf ) of the proton , which is historically referred to as `` pomeron '' . renormalizing the `` gap probability '' to unity over all @xmath8 phase space corrects for the unphysical effect of overlapping diffractive rapidity gaps and leads to an agreement between theory and experiment ( see  @xcite and references therein ) . the gap probability renormalization model is further supported by the following soft - diffraction results obtained by cdf  @xcite :    * double - diffraction ( central gap ) : same suppression factor as in single - diffraction ; * multi - gap diffraction : double - gap to single - gap ratio non - suppressed ; * energy independence : @xmath9  constant as @xmath10 ; * pomeron intercept and slope : they are related !  @xcite . similar results are found for hard - diffraction .    in this paper , we review the results obtained in run  ii .        the cdf  ii detector is shown schematically in fig . [ fig : detector ] ( from ref . the components of the main detector  @xcite used in the diffractive program are the tracking system , the central ( ccal ) , plug ( pcal ) , and forward ( fcal ) calorimeters , and the erenkov luminosity counters ( clc ) . the diffractive program benefited from dedicated triggers and a system of special forward detectors . the following forward detectors were employed  @xcite :    * rps ( roman pot spectrometer )  -  detects leading @xmath11 s at @xmath12 ; * mpcal ( miniplug calorimeters )  -  measure @xmath13 and @xmath14 at @xmath15 ; * bsc ( beam shower counters )  -  identify rapidity gaps at @xmath16 . there are three classes of results obtained thus far from run  ii data :    * exclusive dilepton and diphoton production ( see talk by m. albrow ) . * rapidity gaps between jets ( see talk by c. mesropian ) . * diffractive / exclusive dijet and w / z production ( this talk ) . diffractive dijet production at the tevatron is suppressed by a factor of @xmath7(10 ) relative to expectations based on the proton pdf extracted from diffractive deep inelastic scattering ( ddis ) at the desy @xmath17 collider hera ( see ref .  @xcite . while no ddis suppression is expected in certain models ( see e.g.  @xcite ) , the primary exchange in ddis is a @xmath18 pair , while dijets are mainly produced by a @xmath19 exchange . the dijet rates at the tevaytron are calculated using a gluon pdf extracted from ddis . a more direct comparison could be made by measuring the dsf in diffractive @xmath20 production at the tevatron , which is dominated by a @xmath18 exchange as in ddis . in run i , only the overall diffractive @xmath20 fraction was measured  @xcite . in run ii , cdf measured both the @xmath20 and @xmath21 diffractive fractions and also lpans to attempt to measure the dsf . production diagrams.,scaledwidth=100.0% ]    figure  [ wz_diagrams ] shows schematic fynman diagrams for diffractive @xmath22 production . in leading order , the @xmath22 is produced by a quark in the pomeron ( left ) , while production by a gluon ( right ) is suppressed by a factor of @xmath23 and can be distinguished from quark production by an associated jet  @xcite . the data analysis is based on events with rps tracking from a data sample of approximately @xmath24  fb@xmath25 . in addition to the @xmath22 selection requirements ( see below ) , a hit in the rps trigger counters and a rps reconstructed track with @xmath26 and @xmath27 are required . a novel feature of the analysis is the determination of the full kinematics of the @xmath28 decay , which is made possible by obtaining the neutrino @xmath29 from the missing @xmath13 , as usual , and @xmath30 from the formula @xmath31 $ ] , where @xmath32 $ ] . mass from the diffractive data sample and a gaussian fit.,scaledwidth=50.0% ]    the cdf @xmath22 selection requirements are @xmath33  gev , @xmath34  gev , @xmath35  gev , and vertex @xmath36-coordinate @xmath37  cm . the @xmath20 mass distribution for events with @xmath38 is shown in fig . [ fig : w - mass ] along with a gaussian fit . the obtained value of @xmath39  gev is in good agreement with the world average @xmath20-mass of @xmath40  gev  @xcite . figure  [ fig : xi_cal ] shows the @xmath41 distributions of the @xmath22 events satisfying different selection requirements . in the @xmath20 case , the requirement of @xmath42 is very effective in removing the overlap events in the region of @xmath43 , while a mass cut of @xmath44  gev has the same effect . in the @xmath21 case , the @xmath41 distribution of all @xmath21 events is used and normalized to the rp - track distribution in the region of @xmath45 ( @xmath46 ) to obtain the nd background in the diffractive region of @xmath43 . accounting for the rps acceptance of @xmath47  % , the trigger counter efficiency of @xmath48  % , the track reconstruction efficiency of @xmath49  % , multiplying by two to include the production by @xmath50 , and correcting the number of nd events for the effect of overlaps due to multiple interactions by multiplying it by a factor of @xmath51  % , allows the calculation of the diffractive fraction of @xmath22 events as    @xmath52 , which yields the results : 1em @xmath53}\%,$ ]    @xmath54}\%.$ ] 1em    the @xmath55 value is consistent with the run  i result of :    @xmath56~\%\;(run~i)$ ] ,    obtained from the measured value of @xmath57\%$ ]  @xcite , which is multiplied by a factor of 0.85 tto account for the reduced ( @xmath58-@xmath59 ) range in run  ii . distribution for various @xmath20 ( left ) and @xmath21 ( right ) event samples.,title="fig:",scaledwidth=40.0% ]    distribution for various @xmath20 ( left ) and @xmath21 ( right ) event samples.,title="fig:",scaledwidth=41.5% ] [ [ diffractive - dijet - production ] ] diffractive dijet production + + + + + + + + + + + + + + + + + + + + + + + + + + + +    preliminary resluts on the @xmath60 , @xmath61 , and @xmath59 dependence of the diffractive structure function from dijet production at @xmath62 gev were reported at `` diffraction-2006 ''  @xcite  . the measured run  ii @xmath60 rates confirm the factorization breakdown observed in run  i. the @xmath61 and @xmath59 dependence results are shown in fig  [ fig : xbjq2 ] . ( momentum fraction of parton in @xmath11 ) for different value s of @xmath63 ; _ ( right ) _ @xmath64 slope vs. @xmath61 . , scaledwidth=51.0% ]     ( momentum fraction of parton in @xmath11 ) for different value s of @xmath63 ; _ ( right ) _ @xmath64 slope vs. @xmath61 . , scaledwidth=49.0% ]    in the range @xmath65  gev@xmath66 , where the inclusive @xmath13 distribution falls by a factor of @xmath67 , the ratio of the sd / nd distribution increases by only a factor of @xmath68 . the above results indicate that the @xmath61 evolution in diffractive interactions is similar to that in nd interactions . * @xmath59-dependence . * the slope parameter @xmath69 of an exponential fit to @xmath59 distributions near @xmath70 shows no @xmath61 dependence in the range @xmath71 . the above results support the picture of a composite pomeron formed from color - singlet combinations of the underlying parton densities of the nucleon  @xcite . [ [ exclusive - dijet - production ] ] exclusive dijet production + + + + + + + + + + + + + + + + + + + + + + + + + +    the process of exclusive dijet production is important for testing and  /  or calibrating models for exclusive higgs production at the lhc . the cdf collaboration has made the first observation of this process and their main result is shown in fig . [ fig : xsec_vs_mjj ] . details can be found in ref . this result favors the model of ref . @xcite , which is implemented in the monte carlo simulation exhume  @xcite . normalized to measured @xmath72 values . the solid curve is the cross section predicted by exhume . , width=302 ] we review cdf  ii results from @xmath0 collisions at @xmath11.96  tev and compare them with theoretical expectations . we concentrate on diffractive w  /  z and dijet production , a comparison of which allows the determination of the quark to gluon ratio of the diffractive exchange . we also discuss the recently published result of exclusive dijet production , which is used to check  /  calibrate theoretical predictions for exclusive higgs boson production at the lhc . results from cdf  ii on rapidity gaps between jets and on exclusive diphoton and dilepton production have also been presented at this conference . combined , these results and the analysis methods used in obtaining them provide a powerful launching board for searches at the lhc aimed at exploiting diffractive and exclusive production to discover new physics . 99 k.  goulianos , `` diffraction and exclusive ( higgs ? ) production from cdf to lhc '' ? in _ les rencontres de physique de la vallee daoste : results and perspectives in particle physics , la thuile , italy , 4 - 10 march 2007 , pp . 177 - 200 _ , frascati physics series , special 44 issuee , edited by mario greco . k.  goulisnos , `` diffraction at cdf , '' in proceedings of _ 12@xmath73 international conference on elastic and diffractive scattering ( blois workshop ) - forward physics and qcd _ , desy , hambyrg , germany 21 - 25 may 2007 , arxiv:0712.3633v2[hep - ph]3 jun 2008 , pp .  137 - 144 , http://arxiv.org/abs/0712.3633 ; ib . _ pomeron intercept and slope : the qcd connection _ , pp .  248 - 253 . t.  aaltonen _ et al . _ ( cdf collaboration ) , phys . d * 77 * , 052004 ( 2008 ) . d.  acosta _ et al . _ ( cdf collaboration ) , phys . d * 71 * , 032001 ( 2005 ) . j. collins , j. phys . g * 28 * , 1069 ( 2002 ) ; arxiv : hep - ph/0107252 . abe et al . ( cdf collaboration ) , phys . lett . * 78 * , 2698 - 2703 ( 1997 ) . yao et al . , journ . g * 33 * , 1 ( 2006 ) and 2007 partial update for 2008 ; http:\pdg.lbl.gov . k. goulianos , proceedings of science , pos(diff2006)016 . v.  a.  khoze , a.  d.  martin , and m.  g.  ryskin , eur . j. c * 19 * , 477 ( 2001 ) [ erratum - ibid . c * 20 * , 599 ( 2001 ) ] . j. monk and a. pilkington , comput . 175 * , 232 ( 2006 ) ; arxiv : hep - ph/0502077 .
results on diffraction from the fermilab tevatron collider obtained by the cdf  ii collaboration using data from @xmath0 collisions at @xmath11.96  tev are reviewed and compared with theoretical expectations . 
 implications for predictions of exclusive higgs boson production rates at the large hadron collider are discussed . 
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