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the discovery of asymptotic freedom is an important corner stone of the foundation of quantum chromodynamics ( qcd ) as the theory of the strong interaction . despite the substantial effort in testing the predictions of this theory at e@xmath0e@xmath1 colliders like e.g.petra  @xcite and lep  @xcite ,
qcd is less precisely surveyed than the electroweak sector of the standard model of electroweak and strong interaction .
the precision of the determination of the strong coupling constant , @xmath2 , at centre - of - mass energies of up to @xmath11  gev at lep ii is only at the level of a few percent ( see e.g.  @xcite ) .    to test the details of the running of @xmath2 , which means the asymptotic freedom
, one has to strive for a precision of better than one percent .
this could be achieved by a determination of @xmath2 at a linear collider operating at a centre - of - mass energy of @xmath3 gev or above .
it would provide a long lever arm for the test of the asymptotic freedom .
besides the running of the coupling constant , qcd also predicts the value of the renormalised quark masses to depend on the scale of the interaction process  @xcite .
first investigations of this running of the quark masses were performed by the lep and slc experiments  @xcite , which suffered from large statistical uncertainties .
further experimental manifestation of the effect is , therefore , still required .
this could be achieved at a linear collider due to its high luminosity and by using very high resolution silicon vertex detectors . here
the silicon micro vertex detectors allow to distinguish bottom and charm quark flavours created by the annihilation process from the other lighter quarks .
the identification of the primary quark flavour could furthermore be used to study the properties of quark and gluon jets .
such studies have already be successfully conducted at lep i and slc ( see e.g.  @xcite ) . at the higher energies of lep ii , however , the data statistics is scarce for a significant investigation of the quark and gluon properties .
again , a linear collider would allow such studies because of its high specific luminosity .
apart from the advantage of very high luminosity , qcd studies at a linear collider also gain from the high centre - of - mass energy .
this is because the impact of hadronisation , which blurs the view at the quarks and gluons , diminishes with a reciprocal power of the scale of the process .
hence the distortion due to hadronisation effects at @xmath3  gev is only about @xmath12 of that at the z mass scale  @xcite .
this article presents a scrutiny of the potential of the tesla linear collider to perform a determination of the strong coupling constant at a centre - of - mass energy of @xmath3  gev .
the study is restricted to an investigation based on monte carlo generator simulations using the pythia 5.722 @xcite , herwig 5.9 @xcite , and ariadne 4.8 @xcite programs which , except for herwig , have been tuned by the opal collaboration at lep  @xcite .
these generators are used to simulate the production of quark - antiquark pairs from the annihilation . to account for the substantial production cross - section of massive gauge boson pairs ( see e.g.  @xcite ) , background from hadronic decays of z and w bosons is considered , where in addition also the decay w@xmath13 is included .
all other leptonic decays of these massive bosons can easily be identified and , hence , rejected .
likewise , background contributions from @xmath14 scattering and @xmath15 pair production are not included .
their contribution can be removed very efficiently as is known from the experiments at lep ii ( see e.g.  @xcite ) .
the production of top quarks leads to significant effects .
this is due to its large mass and the appearance of typically three jets of particles from its decay .
top quark events , therefore , appear rather spherically in the detector , thus immitating multijet events .
figure  [ fig - top - distortions ] shows the impact of the pair - produced top quarks on the thrust observable and the jet rates , both of which are usually used to determine the value of the strong coupling constant .
it is therefore indispensable to exclude the contribution from top quarks when performing an @xmath2 determination .
the impact of initial state radiation is accounted for using its next - to - leading order treatment in the pythia generator .
radiative events constitute a large fraction of the hadronic final states , especially radiative returns to the z pole .
most of these can easily be rejected by requiring the reconstructed mass of the whole event to be close to the centre - of - mass energy of the colliding beams .
such a cut on the effective centre - of - mass energy , @xmath16 , is usually applied in the hadronic event selection at lep ii ( e.g.  @xcite ) .
it effectively takes out radiative z return events as can be seen in figure  [ fig - isr+bs ] .
beamstrahlung , which is of relevance at a linear collider only , is simulated using the program circe 1.28  @xcite which has been interfaced to the pythia generator .
when using the parameters proposed for the tesla linear collider , only a negligible fraction of the events is lost due to beamstrahlung ( see figure  [ fig - isr+bs ] ) if the cut @xmath17 is applied which is usually used by the lep experiments .
to study the prospects of a determination of @xmath2 at the tesla linear collider , an integrated luminosity of @xmath18 fb@xmath19 has been simulated .
this corresponds to roughly one year of data taking at the design luminosity of the collider .
.[tab - no - of - events ] approximate number of events for @xmath18  fb@xmath19 and the cross - sections taken from pythia  @xcite . [ cols="<,^,^,^,^,^ " , ]     the error budget of an @xmath2 determination is compiled from different sources . since
a perfect detector has been assumed , the corresponding experimental uncertainties are adopted from measurements at lep ii ( e.g.  @xcite ) .
effects due to the roughly @xmath20 background from boson pairs are neglected .
the statistical uncertainty is estimated by considering a @xmath21 selection efficiency and an expected integrated luminosity of @xmath22 within one year .
this corresponds to about @xmath23 million hadronic events which have been generated using the pythia generator employing the tuned set of parameters .
the simulated events are used to assess the remaining uncertainties due to hadronisation corrections and due to the choice of the hadronisation parameters by fitting the @xmath4-matched second order ( @xmath5 ) and resummed calculations ( nlla ) to distributions of the observables in the hadronic final state .
distributions from the thrust , heavy jetmass , total and wide jet broadening , @xmath24-parameter , and the @xmath25 to @xmath26-jet flip @xmath27 value , @xmath28 , obtained from the durham jet algorithm are used .
hadronisation correction factors are applied to these distributions before fitting the theoretical expressions .
the result of the fits is exemplified for thrust , heavy jetmass , wide jet broadening , and the jet flip in figure  [ fig - evshapes ] . in general good fits
are obtained .
however , for the heavy jetmass and the wide jet broadening an excursion of the fitted curve from the simulated data is visible at small values of these observables .
this could indicate a problem of either the theoretical formulae or of the event generator program .
the fit must , therefore , not go too far into this @xmath25-jet region , which represents the bulk of statistics indeed .
finally , also the impact of a variation of the renormalisation scale factor , @xmath29 , is considered . as has become usual @xmath29 is varied from unity to @xmath23 and @xmath25 , respectively , assigning the change in @xmath30 as the uncertainty due to the choice of the renormalisation scale factor .
table  [ tab - alphas - error - budget ] lists the individual contributions to the total uncertainty of @xmath2 at the z mass scale , @xmath31 . to calculate a total uncertainty ,
the individual error contributions from all six observables are averaged for each systematic variation individually .
the total error is then obtained by adding the individual contributions in quadrature . excluding the uncertainty derived when
choosing the herwig generator to correct for hadronisation effects , because it is not tuned to the lep data yet , the total error becomes @xmath32 .
this error incorporates a significant contribution of about @xmath33 due to the scale uncertainty .
it should be noted that it is of similar size as the typical error obtained by the lep and slc experiments .
the error @xmath34 corresponds to @xmath35 .
a feasibility study of the determination of the strong coupling constant , @xmath2 , at the tesla linear collider has been presented starting from the selection of hadronic events .
neither initial state radiation nor beamstrahlung constitute a substantial problem for such a qcd investigation at this collider .
the major background stems from the pair production of w and z bosons .
both can be easily suppressed by cutting on the hemisphere masses and on the polar angle of the thrust axis .
top quarks significantly distort event shape and jet rate distributions and must , therefore , also be excluded from an @xmath2 determination based on such observables .
it has been found that a cut on the minimum value of the jet broadening effectively removes the contribution from top quarks without affecting the selection efficiency .
the hadronisation corrections and the associated uncertainties are very small at tesla energies .
however , the contribution from different hadronisation models could become a dominating source of error .
fits of the @xmath4-matched second order and resummed calculations to six observables have been performed to assess the systematic uncertainties of the derived value of @xmath2 using data from monte carlo generators only .
exerimental uncertainties have been adopted from the lep ii experiments and are found to be small .
a very significant contribution to the total uncertainty of @xmath36 stems from the choice of the renormalisation scale .
its absolute contribution will shrink with increasing centre - of - mass energy but the relative uncertainty is not diminished . to improve on the scale uncertainty theoretical calculations of third order in @xmath2
are absolutely required .
i would like to thank the organisers of the third ecfa workshop which took place from november 7 - 10 in frascati , italy .
s.  bethke in : proceedings of the _ ivth international symposium on radiative corrections ( radcor98 ) applications of quantum field theory to phenomenology _ , j.  sola ( ed . ) , world scientific , 1999 , 243 - 260 , pitha 98/43 , hep - ex/9812026 , w.  bernreuther , a.  brandenburg , and p.  uwer , _ phys . rev .
* 79 * ( 1997 ) 189 ; + g.  rodrigo , a.  santamaria , and m.  bilenky , _ phys .
lett . _ * 79 * ( 1997 ) 193 ; + p.  nason and c.  oleari , _ nucl .
phys . _ * b521 * ( 1998 ) 237 , hep - ph/9709360 .
l3 collaboration : b.  adeva _
_ , _ phys .
_ * b271 * ( 1991 ) 461 ; + delphi collaboration : p.
abreu _ et  al .
_ , _ phys .
lett . _ * b418 * ( 1998 ) 430 ; + aleph collaboration : d.  buskulic _ et  al .
_ , _ phys .
_ * b335 * ( 1995 ) 381 ; + sld collaboration : k.  abe _ et  al .
_ , _ phys .
* d59 * ( 1999 ) 012002 , hep - ex/9805023 .
delphi collaboration : p.  abreu _ et  al .
_ , _ z. phys . _
* c73 * ( 1997 ) 229 ; + l3 collaboration : m.  acciarri _ et  al .
_ , _ phys .
_ * b371 * ( 1996 ) 137 ; + aleph collaboration : e.  barate _
_ , _ phys .
rep . _ * 294 * ( 1998 ) 1 .
the potential of the tesla linear e@xmath0e@xmath1 collider to determine the strong coupling constant , @xmath2 , at @xmath3  gev is investigated . 
 experimental complications due to background from w- and z - pairs , top - production , initial state photon radiation and from beamstrahlung are considered . 
 the hadronic event selection procedures used by the experiments at lep ii are reviewed for the applicability at tesla . 
 an estimate of the various error contributions to the total uncertainty of an @xmath2 determination is presented . 
 it confirms that hadronisation effects are diminished while the uncertainty from the choice of the renormalisation scale will dominate . 
 fits of the @xmath4-matched second order ( @xmath5 ) and resummed calculation ( nlla ) to six observables are used to estimate the error contributions . 
 this yields the expectation of the precision for @xmath6 of @xmath7 .    to    * determination of @xmath8 at @xmath9  gev + from event shapes and jet rates *    o.  biebel@xmath10    @xmath10    \iii . 
 institut der rwth aachen , d-52056 aachen , germany + now at : max - planck - institut fr physik , d-80805 mnchen , germany + contact e - mail : otmar.biebel@cern.ch