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\title{PROGRESS IN PERTURBATIVE QCD CALCULATIONS FROM LEP TO TEVATRON RUN II AND LHC
$^*$
}
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\author{M. Grazzini}
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\vspace*{-1cm}

\organization{Dipartimento di Fisica, Universit\`a di Firenze\\ and\\
INFN, Sezione di Firenze, Largo Fermi 2, I-50125 Firenze, Italy}

\maketitle

\vspace*{-1cm}

\abstract{I briefly review the progress in perturbative QCD calculations in LEP era and discuss the prospects for the extension of their accuracy to higher orders.}
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\footnotetext[1]{Invited talk given at the XIII italian meeting on high energy physics ``LEPTRE'', Rome April 18-20 2001, to appear in the proceedings.}


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\vskip 1cm

Higher order QCD calculations are essential in order to assess and precisely quantify our confidence in the Standard Model. Perturbative predictions at the Leading Order (LO) in the QCD coupling $\as$ rely
on tree-level matrix elements and
therefore
provide only an approximate description of cross sections and distributions. The unphysical
dependence on
renormalization and factorization scales
turns out to be quite large.

The simplest higher order calculations are those for
fully
inclusive observables. Examples of these quantities are $\sigma({\rm e^+e^-\to hadrons})$, the hadronic branching ratio of the $Z$ and of the $\tau$ lepton. For these quantities infrared (IR) singularities essentially cancel at the integrand level and thus accurate predictions exist up to next-to-next-to-leading order (NNLO) \cite{inclusive}.
Moreover these observables
%have
are affected by
%very
small non perturbative corrections and
thus they are particularly suitable for $\as$ measurements \cite{Dissertori}.
 
The most detailed QCD studies at $e^+e^-$ colliders are based on {\em event shapes} and {\em jet cross sections}.
Event shapes variables are quantities that characterize the structure of the hadronic event. 
Thus, with respect to fully inclusive observables, event shape distributions are useful not only to measure $\as$ but also to perform stringent QCD tests. The price to pay is that non perturbative effects are more important \cite{Banfi} and that the perturbative calculation is more difficult.
Real and virtual contributions have a different number of final state partons and they should be integrated separately in order to cancel IR singularities. This is only possible by combining analytical techniques with numerical (Monte Carlo) integration. In practice one performs analytically only the part of the integration that produces the singularities. There are two methods of this kind: the subtraction method \cite{Ellis:1981wv} and the slicing method \cite{Fabricius:1981sx}\footnote{A complete numerical method was proposed in Ref.\cite{Soper:1998ye}.}.
The NLO calculation for all the relevant $3$-jet observables was performed by using the subtraction method in Ref.\cite{Kunszt:1989km}.

At the beginning of LEP era the standard procedure was the comparison of the data with NLO QCD.
%The peculiar feature of these QCD test is the following:
Far away from the two-jet region the NLO calculation with
the renormalization scale $\mu$ of order of the
center-of-mass
energy $Q$ usually
gives good fits to the data. On the contrary,
very small (and unphysical) values of $\mu$ \cite{Dissertori}
are required in order
to extend the range of the fit.

This is a signal of the fact that close to the boundary of the phase space (two-jet region) large logarithmic corrections of the form $\as \log^2 1/y$ appear that spoil the perturbative expansion
(here $y$ denotes the variable that becomes small in the two-jet region).
These contributions, whose origin is due to the emission of soft and collinear gluons,
have to be resummed to all orders.
The resummation formalism was developed up to next-to-leading-logarithmic (NLL) accuracy for those shape variables that fulfill {\em exponentiation} \cite{shape}. This property
%allows to resum the large logarithmic correction at all orders and
is a consequence of two basic conditions:
$i)$ {\em matrix element factorization}; $ii)$ {\em phase space factorization}.
The first is a {\em dynamical} condition that relies on the general properties of soft and collinear emission. The second is a {\em kinematical} condition that depends on the particular quantity we consider. Both have to be satisfied in order to be able to perform resummation. The NLL resummed calculation is matched with the NLO prediction (NLL+${\cal O}(\as^2)$) to give a result that is everywhere as good as the NLO result and much better in the $y\to 0$ region. 
Extensive studies based on NLL+${\cal O}(\as^2)$ calculations have been carried out over the past years \cite{Dissertori}.
These studies have shown that resummed predictions are less sensitive to
%the choice of
the renormalization scale $\mu$ and in particular
enable us
to avoid the choice
of extremely small (unphysical) $\mu$ in the two-jet region.

A jet is qualitatively defined as a collimated spray of energetic hadrons, and is considered as a typical signal of parton dynamics at short distances. However, in order to perform quantitative studies, one needs a precise definition of jet.
Once a jet definition has been chosen, the $n-$jet cross section is a function that depends only on the resolution parameter $y_{cut}$.
When $y_{cut}$ becomes small jet cross sections develop large $\as\log^2 1/y_{cut}$  corrections
similar to the ones that affect shape distributions in the two-jet region.
%These corrections have to be resummed at all orders.
As it happens for shape variables, the resummation of these corrections is possible if conditions $i)$ and $ii)$ above are satisfied.
The old JADE algorithm \cite{Bartel:1986ua} does not allow to perform the resummation since it
%gives
induces
strong kinematic correlations that spoil $ii)$. The $k_T$ algorithm was introduced to make the resummation in the $y_{cut}\to 0$ region possible \cite{Catani:1991hj}.
NLL+${\cal O}(\as^2)$ predictions exist for jet rates \cite{Catani:1991hj}
and
jet
multiplicities \cite{Catani:1992pm}.

As far as NLO calculations are concerned, there
%was great progress
were important developments
in the last few years. In the first applications both the subtraction
and the slicing methods were used with extensive partial fractioning on the QCD matrix element.
This procedure is intrinsically process dependent.
Later it was understood that both methods can be generalized in a process
independent manner. The key observation is that the IR singularities
can be singled out in a universal manner by using the factorization
properties of soft and collinear emission.
Today we have general algorithms that in principle allow to compute any observable at NLO, both with the subtraction \cite{sub,Catani:1997vz} and with the slicing method \cite{sli}.
As far as LEP physics is concerned new calculations appeared for: $3$-jet observables \cite{Catani:1997vz}\footnote{With respect to the calculation of Ref.\cite{Kunszt:1989km} this one includes the contribution of the $Z$ and allows to study the orientation of the event.}, $3$-jet with mass effects included \cite{threejetm} and $4$-jet \cite{fourjet}.

With this situation one may wonder why we should do an effort to go to NNLO.
There are several reasons to do that. The first one is that since reliable perturbation theory starts at NLO, error estimate should start at NNLO.  As far as LEP is concerned, the NNLO calculation of $3$-jet observables would considerably reduce the error on $\as$ \cite{Dissertori}. Then we should consider that improved experimental techniques and higher luminosities will require a better control on the QCD background. 

A NNLO calculation requires in general three basic ingredients:
$~i)$ NNLO parton distributions;
$~ii)$ two-loop amplitudes;
$~iii)$ knowledge of the IR behaviour of tree-level and one-loop amplitudes at ${\cal O}(\as^2)$.

In the last years enormous progress has been achieved in all these aspects.
For a consistent evaluation of a NNLO cross section at hadron colliders NNLO (three loop) parton distributions are required. Even though their NNLO evolution kernels are
not fully available, some of their Mellin moments have been computed
\cite{vermaseren} and,
from these, approximated kernels have been constructed \cite{vnvogt}.
Recently, the new MRST \cite{mrst2000} set of distributions became
available, including the (approximated) NNLO 
densities, which allows an evaluation of the hadronic
cross section to (almost full) NNLO accuracy.

Until two years ago no two-loop amplitude depending on more than one scale was available.
Thanks to the calculations of important two-loop master diagrams \cite{dbox} and to
the great progress in the reduction of tensor integrals \cite{Anastasiou:2000mf}
the first calculations of two-loop $2\to 2$ amplitudes have recently appeared in QED \cite{Bern:2001ie},
and in QCD \cite{glover}. 
The IR singularities appearing in these amplitudes are in agreement with the general
prediction in  Ref.\cite{Catani:1998bh}.
These results will be relevant for the calculation of Bhabha scattering
and two-jet cross sections in hadron collisions at NNLO.

To perform a NNLO calculation one has to combine the two-loop amplitude with the
one-loop correction where one parton is unresolved and with the tree-level contribution
where two partons are unresolved.
The kernels that control soft \cite{Bern:1998sc,Catani:2000pi}
and collinear \cite{Bern:1998sc,Kosower:1999rx}
singularities appearing in one-loop amplitudes have been computed.
The IR singularities appearing in tree-level amplitudes are more complicated because
many soft/collinear limits have to be considered. All these limits have been studied
\cite{Campbell:1998hg,Catani:2000ss}
and the corresponding kernels have been computed \cite{Campbell:1998hg}--\cite{DelDuca:2000ha}.

The step that remains to be performed is to combine all
%these informations
these ingredients
to construct general algorithms to handle and cancel infrared singularities.
This step is more difficult than at NLO since the pattern of IR singularities is much more complicated. Nevertheless some applications where some progress in this direction has been achieved recently appeared \cite{Gehrmann-DeRidder:1998gf,deFlorian:2000pr,Catani:2001ic}.

The results of
Refs.\cite{Bern:1998sc}--\cite{DelDuca:2000ha}
are relevant not only to perform NNLO calculations, but also to extend
the accuracy of resummed calculations at NNLL.
Transverse momentum ($k_T$) distributions of high-mass systems (lepton pairs, vector boson, Higgs...) in hadronic collisions
are affected in the small $k_T$ limit by large logarithmic contributions of the same (infrared) nature of the ones present in
event-shape distributions in the two-jet limit.

In Ref.\cite{deFlorian:2000pr} the structure of these large corrections was studied at ${\cal O}(\as^2)$ up
to NNLL accuracy. This calculation was performed in a general (process independent)
manner by exploiting the universal nature of these corrections.
The results of Refs.\cite{Bern:1998sc}--\cite{Catani:1999nv}
were used
%combined
to construct improved approximations of the relevant matrix elements that allow to control
all the infrared singular regions responsible for the appearance of the logarithmic contributions.
%, avoiding double counting.
This method, even if strongly dependent on the special kinematics of this class of processes, could be extended
in the spirit of Ref.\cite{Catani:1997vz} to more general cases
\footnote{The results of Ref.\cite{deFlorian:2000pr}, combined with the numerical estimate \cite{vnvogt}
of the  coefficient that controls the soft-collinear singularity in the three-loop splitting functions
will allow a (partial) extension of the accuracy
of these resummed calculations at NNLL.}. 

In Ref.\cite{Catani:2001ic} the calculation of the soft and virtual
corrections to Higgs boson production at hadron colliders was presented.
This calculation was done by combining the recent
results \cite{Harlander:2000mg} for the two-loop amplitude $gg\to H$
in the large $m_{top}$ limit with the soft factorization formulae for tree-level
\cite{Campbell:1998hg,Catani:2000ss} and one-loop \cite{Bern:1998sc,Catani:2000pi}
amplitudes
\footnote{The same calculation was independently
performed in Ref.\cite{Harlander:2001is}
%but
by means of the direct evaluation of the relevant
%tree level and one loop
amplitudes in the soft limit.}.
From the theoretical side this calculation is very important since it provides
a check of the cancellation of the IR poles from $1/\ep^4$ to $1/\ep$ between real and
virtual contributions.
From the phenomenological side the results give a first consistent estimate of
the QCD corrections to this important process at NNLO.

Up to a few years ago NNLO calculations, if doable,
were considered very far in the future. With the progress
%registered
%witnessed
achieved
in the recent years we can be more confident that these calculations will be
feasible in the LHC era.

\noindent {\bf Acknowledgments.} I wish to thank Stefano Catani and G\"unther Dissertori for their help in preparing this talk.



\begin{thebibliography}{90}


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S.~G.~Gorishnii, A.~L.~Kataev and S.~A.~Larin,
%``The O (alpha-s**3) corrections to sigma-tot (e+ e- $\to$ hadrons) and Gamma (tau- $\to$ tau-neutrino + hadrons) in QCD,''
Phys.\ Lett.\ B {\bf 259} (1991) 144;
%%CITATION = PHLTA,B259,144;%%
L.~R.~Surguladze and M.~A.~Samuel,
%``Total hadronic cross-section in e+ e- annihilation at the four loop level of perturbative QCD,''
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%%CITATION = PRLTA,66,560;%%


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G. Dissertori, these proceedings.

\bibitem{Banfi}
A. Banfi, these proceedings.

%\cite{Ellis:1981wv}
\bibitem{Ellis:1981wv}
R.~K.~Ellis, D.~A.~Ross and A.~E.~Terrano,
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%%CITATION = NUPHA,B178,421;%%

%\cite{Fabricius:1981sx}
\bibitem{Fabricius:1981sx}
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%%CITATION = ZEPYA,C11,315;%%


%\cite{Soper:1998ye}
\bibitem{Soper:1998ye}
D.~E.~Soper,
%``{QCD} calculations by numerical integration,''
Phys.\ Rev.\ Lett.\ {\bf 81} (1998) 2638.
%.
%%CITATION = ;%%

%\cite{Kunszt:1989km}
\bibitem{Kunszt:1989km}
Z.~Kunszt, P.~Nason, G.~Marchesini and B.~R.~Webber,
in ``Z Physics at LEP 1'', CERN 89-08, vol. 1, p. 373.


\bibitem{shape}
S.~Catani, L.~Trentadue, G.~Turnock and B.~R.~Webber,
%``Resummation of large logarithms in e+ e- event shape distributions,''
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%%CITATION = NUPHA,B407,3;%%

%\cite{Bartel:1986ua}
\bibitem{Bartel:1986ua}
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%``Experimental Studies On Multi - Jet Production In E+ E- Annihilation At Petra Energies,''
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%%CITATION = ZEPYA,C33,23;%%

%\cite{Catani:1991hj}
\bibitem{Catani:1991hj}
S.~Catani, Y.~L.~Dokshitzer, M.~Olsson, G.~Turnock and B.~R.~Webber,
%``New clustering algorithm for multi - jet cross-sections in e+ e- annihilation,''
Phys.\ Lett.\ B {\bf 269} (1991) 432.
%%CITATION = PHLTA,B269,432;%%

%\cite{Catani:1992pm}
\bibitem{Catani:1992pm}
S.~Catani, Y.~L.~Dokshitzer, F.~Fiorani and B.~R.~Webber,
%``Average number of jets in e+ e- annihilation,''
Nucl.\ Phys.\ B {\bf 377} (1992) 445.
%%CITATION = NUPHA,B377,445;%%


\bibitem{sub}
S.~Frixione, Z.~Kunszt and A.~Signer,
%``Three-jet cross sections to next-to-leading order,''
Nucl.\ Phys.\ B {\bf 467} (1996) 399;
%%CITATION = ;%%
Z.~Nagy and Z.~Trocsanyi,
%``Calculation of QCD jet cross sections at next-to-leading order,''
Nucl.\ Phys.\ B {\bf 486} (1997) 189.
%.
%%CITATION = ;%%


%\cite{Catani:1997vz}
\bibitem{Catani:1997vz}
S.~Catani and M.~H.~Seymour,
%``A general algorithm for calculating jet cross sections in NLO QCD,''
Nucl.\ Phys.\ B {\bf 485} (1997) 291
[Erratum-ibid.\ B {\bf 510} (1997) 291].
%.
%%CITATION = ;%%


\bibitem{sli}
W.~T.~Giele and E.~W.~Glover,
Phys.\ Rev.\ D {\bf 46} (1992) 1980;
%%CITATION = PHRVA,D46,1980;%%
W.~T.~Giele, E.~W.~Glover and D.~A.~Kosower,
Nucl.\ Phys.\ B {\bf 403} (1993) 633;
%%CITATION = ;%%
S.~Keller and E.~Laenen,
%``Next-to-leading order cross sections for tagged reactions,''
Phys.\ Rev.\ D {\bf 59} (1999) 114004.
%.
%%CITATION = ;%%


\bibitem{threejetm}
W.~Bernreuther, A.~Brandenburg and P.~Uwer,
%``Next-to-leading order QCD corrections to three-jet cross sections with  massive quarks,''
Phys.\ Rev.\ Lett.\ {\bf 79} (1997) 189;
%%CITATION = ;%%
P.~Nason and C.~Oleari,
%``Next-to-leading-order corrections to the production of heavy-flavour  jets in e+ e- collisions,''
Nucl.\ Phys.\ B {\bf 521} (1998) 237;
%%CITATION = ;%%
G.~Rodrigo, M.~Bilenky and A.~Santamaria,
%``Quark-mass effects for jet production in e+ e- collisions at the  next-to-leading order: Results and applications,''
Nucl.\ Phys.\ B {\bf 554} (1999) 257.
%.
%%CITATION = ;%%


\bibitem{fourjet}
L.~Dixon and A.~Signer,
%``Complete O(alpha(s)**3) results for e+ e- --> (gamma,Z) --> four jets,''
Phys.\ Rev.\ D {\bf 56} (1997) 4031; 
%%CITATION = ;%%
Z.~Nagy and Z.~Trocsanyi,
%``Next-to-leading order calculation of four-jet shape variables,''
Phys.\ Rev.\ Lett.\ {\bf 79} (1997) 3604;
%.
%%CITATION = ;%%
S.~Weinzierl and D.~A.~Kosower,
%``{QCD} corrections to four-jet production and three-jet structure in e+ e-  annihilation,''
Phys.\ Rev.\ D {\bf 60} (1999) 054028.
%%CITATION = ;%%

\bibitem{vermaseren}
%Mellin moments
S. A. Larin, P. Nogueira, T. van Ritbergen and J. A. M. Vermaseren,
Nucl. Phys.\ B {\bf 492} (1997) 338;
%%CITATION = ;%%
A. Retey and J. A. M. Vermaseren, .
%%CITATION = ;%%


\bibitem{vnvogt}
W.~L.~van Neerven and A.~Vogt,
%``NNLO evolution of deep-inelastic structure functions: The non-singlet  case,''
Nucl.\ Phys.\ B {\bf 568} (2000) 263,
%.
%%CITATION = ;%%
%W.~L.~van Neerven and A.~Vogt,
%``NNLO evolution of deep-inelastic structure functions: The singlet case,''
Nucl.\ Phys.\ B {\bf 588} (2000) 345.
%.
%%CITATION = ;%%

\bibitem{mrst2000}
A.~D.~Martin, R.~G.~Roberts, W.~J.~Stirling and R.~S.~Thorne,
%``Estimating the effect of NNLO contributions on global parton analyses,''
Eur.\ Phys.\ J.\ C {\bf 18} (2000) 117.
%.
%%CITATION = ;%%

\bibitem{dbox}
V.~A.~Smirnov,
%``Analytical result for dimensionally regularized massless on-shell  double box,''
Phys.\ Lett.\ B {\bf 460} (1999) 397;
%%CITATION = ;%%
J.~B.~Tausk,
%``Non-planar massless two-loop Feynman diagrams with four on-shell legs,''
Phys.\ Lett.\ B {\bf 469} (1999) 225.
%%CITATION = ;%%

%\cite{Anastasiou:2000mf}
\bibitem{Anastasiou:2000mf}
C.~Anastasiou, T.~Gehrmann, C.~Oleari, E.~Remiddi and J.~B.~Tausk,
%``The tensor reduction and master integrals of the two-loop massless  crossed box with light-like legs,''
Nucl.\ Phys.\ B {\bf 580} (2000) 577.
%%CITATION = ;%%

%\cite{Bern:2001ie}
\bibitem{Bern:2001ie}
Z.~Bern, L.~Dixon and A.~Ghinculov,
%``Two-loop correction to Bhabha scattering,''
Phys.\ Rev.\ D {\bf 63} (2001) 053007.
%.
%%CITATION = ;%%


\bibitem{glover}
C.~Anastasiou, E.~W.~Glover, C.~Oleari and M.~E.~Tejeda-Yeomans,
%``Two-loop QCD corrections to q anti-q --> q' anti-q',''

%%CITATION = ;%%
%C.~Anastasiou, E.~W.~Glover, C.~Oleari and M.~E.~Tejeda-Yeomans,
%``Two-loop QCD corrections to q anti-q --> q anti-q,''

%%CITATION = ;%%
%C.~Anastasiou, E.~W.~Glover, C.~Oleari and M.~E.~Tejeda-Yeomans,
%``Two-loop QCD corrections to massless quark gluon scattering,''
;
%%CITATION = ;%%
E.~W.~Glover, C.~Oleari and M.~E.~Tejeda-Yeomans,
%``Two-loop QCD corrections to gluon gluon scattering,''
.
%%CITATION = ;%%


%\cite{Catani:1998bh}
\bibitem{Catani:1998bh}
S.~Catani,
%``The singular behaviour of {QCD} amplitudes at two-loop order,''
Phys.\ Lett.\ B {\bf 427} (1998) 161.
%.
%%CITATION = ;%%



\bibitem{Bern:1998sc}
Z.~Bern, V.~Del Duca and C.~R.~Schmidt,
%``The infrared behavior of one-loop gluon amplitudes at  
% next-to-next-to-leading order,''
Phys.\ Lett.\ B {\bf 445} (1998) 168;
%.
%%CITATION = ;%%
%\cite{Bern:1999ry}
%\bibitem{Bern:1999ry}
Z.~Bern, V.~Del Duca, W.~B.~Kilgore and C.~R.~Schmidt,
%``The infrared behavior of one-loop {QCD} amplitudes at  next-to-next-to-leading order,''
Phys.\ Rev.\ D {\bf 60} (1999) 116001.
%.
%%CITATION = ;%%

%\cite{Catani:2000pi}
\bibitem{Catani:2000pi}
S.~Catani and M.~Grazzini,
%``The soft-gluon current at one-loop order,''
Nucl.\ Phys.\ B {\bf 591} (2000) 435.
%.
%%CITATION = ;%%


%\cite{Kosower:1999rx}
\bibitem{Kosower:1999rx}
D.~A.~Kosower and P.~Uwer,
%``One-loop splitting amplitudes in gauge theory,''
Nucl.\ Phys.\ B {\bf 563} (1999) 477.
%.
%%CITATION = ;%%


\bibitem{Campbell:1998hg}
J.~M.~Campbell and E.~W.~Glover,
%``Double unresolved approximations to multiparton scattering amplitudes,''
Nucl.\ Phys.\ B {\bf 527} (1998) 264.
%.
%%CITATION = ;%%


%\cite{Catani:2000ss}
\bibitem{Catani:2000ss}
S.~Catani and M.~Grazzini,
%``Infrared factorization of tree level QCD amplitudes at the  next-to-next-to-leading order and beyond,''
Nucl.\ Phys.\ B {\bf 570} (2000) 287.
%.
%%CITATION = ;%%



%\cite{Catani:1999nv}
\bibitem{Catani:1999nv}
S.~Catani and M.~Grazzini,
%``Collinear factorization and splitting functions for  next-to-next-to-leading order {QCD} calculations,''
Phys.\ Lett.\ B {\bf 446} (1999) 143.
%.
%%CITATION = ;%%

%\cite{DelDuca:2000ha}
\bibitem{DelDuca:2000ha}
V.~Del Duca, A.~Frizzo and F.~Maltoni,
%``Factorization of tree QCD amplitudes in the high-energy limit and in  the collinear limit,''
Nucl.\ Phys.\ B {\bf 568} (2000) 211.
%.
%%CITATION = ;%%



%\cite{Gehrmann-DeRidder:1998gf}
\bibitem{Gehrmann-DeRidder:1998gf}
A.~Gehrmann-De Ridder and E.~W.~Glover,
%``A complete O(alpha alpha(s)) calculation of the photon + 1jet rate in  e+ e- annihilation,''
Nucl.\ Phys.\ B {\bf 517} (1998) 269.
%.
%%CITATION = ;%%


%\cite{deFlorian:2000pr}
\bibitem{deFlorian:2000pr}
D.~de Florian and M.~Grazzini,
%``Next-to-next-to-leading logarithmic corrections at small transverse  momentum in hadronic collisions,''
Phys.\ Rev.\ Lett.\ {\bf 85} (2000) 4678.
%.
%%CITATION = ;%%

%\cite{Catani:2001ic}
\bibitem{Catani:2001ic}
S.~Catani, D.~de Florian and M.~Grazzini,
%``Higgs production in hadron collisions: Soft and virtual QCD corrections  at NNLO,''
JHEP {\bf 0105} (2001) 025.
%.
%%CITATION = ;%%


\bibitem{Harlander:2000mg}
R.~V.~Harlander,
%``Virtual corrections to g g $\to$ H to two loops in the heavy top limit,''
Phys.\ Lett.\ B {\bf 492} (2000) 74.
%.
%%CITATION = ;%%

%\cite{Harlander:2001is}
\bibitem{Harlander:2001is}
R.~V.~Harlander and W.~B.~Kilgore,
%``Soft and virtual corrections to p p $\to$ H + X at NNLO,''
.
%%CITATION = ;%%














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