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the standard model of electroweak interactions ( sm ) so far withstood all experimental challenges and is tested as a quantum field theory at the 0.1% level  @xcite .
however , the mechanism of mass generation in the sm predicts the existence of a higgs boson which , so far , has eluded direct observation .
direct searches at lep2 give a 95% confidence - level lower bound on the mass of the sm higgs boson of @xmath2  gev  @xcite .
indirect information on the mass of the higgs boson can be extracted from the @xmath3 dependence of radiative corrections to the w boson mass . with the present knowledge of the w boson and top quark masses , and the electromagnetic coupling constant , @xmath4 , the sm higgs boson mass can be indirectly constrained to @xmath5  gev  @xcite by a global fit to all electroweak precision data .
future more precise measurements of the w boson and top quark masses are expected to considerably improve the present indirect bound on @xmath3 :  with a precision of 27  mev ( 16  mev ) for the w boson mass , @xmath6 , and 2.7  gev ( 1.4  gev ) for the top quark mass which are target values for run  iia ( run  iib ) of the tevatron  @xcite , @xmath3 can be predicted with an uncertainty of about @xmath7 ( 25% ) .
in addition , the confrontation of a precisely measured w boson mass with the indirect sm prediction from a global fit to all electroweak precision data , @xmath8  gev  @xcite , together with a precise measurement of the w width , @xmath9 , from the high transverse mass tail , will provide a stringent test of the sm .
a detailed discussion of the prospects for the precision measurement of @xmath6 and @xmath9 , and of the ( leptonic ) effective weak mixing angle , @xmath10 , at run  ii and the lhc is given in refs .
@xcite and  @xcite , respectively .
in order to measure @xmath6 with high precision in a hadron collider environment it is necessary to fully control higher order qcd and electroweak radiative corrections to the w and z production processes .
the status of the qcd corrections to w and z boson production at hadron colliders is reviewed in refs .
@xcite . here
we discuss the electroweak @xmath11 corrections to @xmath12 and @xmath13 ( @xmath14 ) as presented in detail in refs .
@xcite and  @xcite , concentrating on photon radiation effects and the impact of non - resonant weak corrections on the w width measurement .
we illustrate the effects caused by photon radiation using z boson production as an example .
the electroweak @xmath11 corrections to neutral - current drell - yan processes naturally decompose into qed and weak contributions , i.e.  they build gauge invariant subsets and thus can be discussed separately .
the radiation of collinear photons off quarks requires the factorization of the arising mass singularities into the pdfs which introduces a dependence on the qed factorization scale , @xmath15 .    in fig .
[ fig : one ] we show the effect of the qed corrections on the invariant mass distribution of the final state lepton pair .
photon radiation strongly affects the shape of the @xmath16 distribution .
this is due to the mass singular terms associated with final state photon radiation , which are proportional to @xmath17 , where @xmath18 is the mass of the final state lepton .
+    at the z pole , the differential cross section is reduced by about 30% in the electron case and by about 20% in the muon case . below the z peak , qed corrections
enhance the cross section by up to a factor  2.7 ( 1.9 ) for electrons ( muons ) .
when lepton identification requirements are taken into account , the large contributions from mass singular logarithms largely cancel in the electron case because electron and photon momenta are combined for small opening angles between the two particles . for muons ,
the energy of a photon which traverses the same calorimeter cell as the muon is required to be @xmath19  gev , and only the momenta of muons and photons with @xmath19  gev are combined . as a result , the mass singular logarithmic terms survive , and the effect of radiative corrections becomes more pronounced , especially at large di - lepton masses .
the distortion of the shape of the breit - wigner resonance curve of the z boson due to final state photon radiation leads to a shift in the z boson mass extracted from data . in the electron channel
, the shift is about 100  mev , whereas for @xmath20 one finds approximately 300  mev .
since the neutrino in w decays is not observed , it is impossible to reconstruct the @xmath21 invariant mass , and the transverse mass ( @xmath22 ) distribution is frequently used to extract the mass and width of the w boson .
final state photon radiation in @xmath23 affects the shape of the @xmath22 distribution in a similar way as the di - lepton invariant mass distribution in @xmath24 .
the ratio of the @xmath25 and lowest order differential cross section as a function of @xmath26 with and without lepton identification requirements taken into account is shown in fig .
[ fig : onea ] .
since neutrinos do not interact with photons , the shift in @xmath6 due to final state photon radiation is about a factor two smaller than in the z case . for more details
we refer the reader to ref .
@xcite .
the virtual radiative corrections to @xmath27 comprise resonant and non - resonant contributions .
the non - resonant contributions , which include those originating from the @xmath28 box diagrams , vanish for @xmath29 , and thus were not included in ref .
@xcite . for precision physics
away from the w pole , however , the non - resonant corrections must be included .
these corrections become important at large values of @xmath22 due to the presence of large sudakov - like electroweak logarithms of the form @xmath30 , which eventually may be resummed  @xcite .    in fig .
[ fig : two ] we show the @xmath22 distribution including the full @xmath11 corrections normalized to the differential cross section in the effective born approximation ( eba ) at the tevatron for electron and muon final states .     +    separation cuts and lepton identification requirements to simulate the detector acceptance as described in ref .
@xcite are taken into account in fig .
[ fig : two ] . for comparison the relative corrections including the resonant @xmath11 electroweak corrections only are also shown ( dashed line ) .
as expected from the presence of large electroweak sudakov - like logarithms , the non - resonant weak corrections strongly increase in magnitude with increasing transverse masses .
both , the resonant and non - resonant electroweak corrections reduce the differential cross section .
the high transverse mass tail can be used for a direct measurement of the width of the w boson , @xmath9 , which in the sm is predicted to be @xmath31  gev . in run
i , @xmath9 has been been measured by cdf and d  with a combined uncertainty of 105  mev from the @xmath22 tail  @xcite . in run
iia , with an integrated luminosity of 2  fb@xmath32 , one expects to achieve a precision of 50  mev per lepton channel and experiment  @xcite . in order to determine how non - resonant electroweak corrections affect the w width extracted from the tail of the transverse mass distribution
, it is useful to consider the ratio of the normalized @xmath22 distribution for an arbitrary w width to the normalized @xmath22 distribution with sm w width , @xmath33\over \left[d\sigma(sm)/dm_t\right]}~{\sigma(sm ) \over\sigma(\gamma_w)}\ ] ] when resonant @xmath11 corrections only are taken into account .
it is easy to show that @xmath34 is proportional to @xmath35 for @xmath36 .
@xmath34 is shown for @xmath37 at the tevatron in fig .
[ fig : three ] .
the dashed , dotted and dash - dotted curves represent the predictions for @xmath38  gev , 2.042  gev and 2.052  gev , respectively .
the solid line shows the result if , instead of a non - standard w width and resonant corrections , the full @xmath11 electroweak corrections with @xmath31  gev are used .
the error bars represent the expected statistical uncertainties for 2  fb@xmath32 .
experimental lepton identification criteria and detector resolution effects are taken into account in fig .
[ fig : three ] .
figure  [ fig : three ] shows that both , non - resonant electroweak corrections and a w width smaller than that predicted in the sm , lead to similar effects in the tail of the @xmath22 distribution .
this effect sets on gradually in case of the non - resonant corrections . for a non - standard w width in contrast
, the ratio drops rapidly above the w pole position , and becomes constant for @xmath39  gev .
since the experimental precision in the tail of the @xmath22 distribution quickly decreases with increasing values of the transverse mass , one concludes that non - resonant electroweak corrections , if ignored in the experimental determination of the w width from the high @xmath22 tail , would shift the extracted value of @xmath9 by about @xmath40  mev .
calculations of the full @xmath11 electroweak corrections to w and z boson production in hadronic collisions are now available .
our results show that , for future precision measurements the full electroweak @xmath11 corrections and probably also multiple photon radiation effects should be taken into account .
the calculation of the non - resonant @xmath11 corrections to w production has recently been completed  @xcite ( see also ref .
@xcite ) . as a first step towards a calculation of the @xmath41 qed corrections , the effects of two - photon radiation in w and z boson production at hadron colliders have been computed in ref .
we would like to thank the organizers of radcor-2002 , for a delightful and inspiring conference experience .
one of us ( u.b . ) is grateful to the fermilab theory group , where part of this work was carried out , for its generous hospitality and for financial support .
this research was supported in part by the national science foundation under grant no .
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we summarize the status of calculations of the electroweak radiative corrections to w and z boson production via the drell - yan mechanism at hadron colliders . to fully exploit the precision physics potential of the high - luminosity environment of the fermilab tevatron @xmath0 ( run  ii ) and the cern lhc @xmath1 colliders , it is crucial that the theoretical predictions are well under control . 
 the envisioned precision physics program includes a precise measurement of the w boson mass and width , and the ( leptonic ) weak mixing angle , as well as probing the standard model ( sm ) of electroweak interactions at the highest accessible center - of - mass energies . 
 some numerical results are presented .    
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