Hard photon next-to-leading corrections to two-fermion production in $e^+ e^-$ collisions above the $Z^0$ peak

Montagna, G.; Nicrosini, O.; Piccinini, F.

doi:10.1007/s002880050525

Cited by 3 publications

(4 citation statements)

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“…However, if the Z 0 radiative return is cut away, the above theoretical error is limited to 0.3% relative deviation for the cross section and 3 × 10 −3 absolute deviation for the forward-backward asymmetry, that are acceptable in the light of the LEP2 experimental precision [237]. The second example of hard-photon contributions damped at LEP1 but no longer negligible at LEP2 comes from the IS second-order non-leading corrections and thirdorder LL contributions.…”

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confidence: 96%

“…Since these corrections are strongly affected by the imposed experimental cuts and can be very difficultly cast in a fully analytic form, one can evaluate their size by performing an exact O(α) perturbative calculation, integrating it numerically and depurating the final result of the universal LL as well as of the non-leading (process dependent) soft+virtual corrections [237]. This procedure allows to isolate and quantify in a clean way the effect of hard-photon contributions in O(α) ISR.…”

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confidence: 99%

“…The results of such an analysis can be found in ref. [237] for typical event selections (ES's) adopted by the LEP Collaborations, namely…”

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confidence: 99%

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Precision physics at LEP

Montagna

Nicrosini

Piccinini

1998

Rivista Nuovo Cimento

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confidence: 96%

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confidence: 99%

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Precision physics at LEP

Montagna

Nicrosini

Piccinini

1998

Rivista Nuovo Cimento

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“…Initial-state next-to-leading O (α) QED corrections are treated exactly for an s ′ cut, in the soft photon approximation otherwise. This means that for center of mass energies sensibly above the Z 0 peak (typically in the LEP 1.5 -LEP 2 regime), the theoretical accuracy of the C branch is under control (theoretical error ≤ 0.3%) when excluding the Z radiative return, whereas including it the theoretical error can grow up to some % depending on the final state selected [15]. In the same energy range, large angle Bhabha scattering becomes a t-channel dominated process: since all the QED corrections implemented are strictly valid for s-channel processes, this means that large angle Bhabha scattering off the Z resonance is treated at the leading logarithmic level.…”

Section: Tbasic(ntstfvecmsiflag)mentioning

confidence: 99%

TOPAZ0 4.0 — A new version of a computer program for evaluation of deconvoluted and realistic observables at LEP 1 and LEP 2

Montagna

Nicrosini

Piccinini

et al. 1999

Computer Physics Communications

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The program TOPAZ0 was developed for computing a variety of physical observables which are related to the e + e − annihilation into fermion pairs and to the large angle Bhabha scattering around the Z resonance. Among them, the Z parameters or pseudo-observables, the de-convoluted cross sections and those dressed with QED radiation, and finally the forward-backward asymmetries. The calculations are performed both for a completely inclusive experimental set-up and for a realistic one, i.e. a set-up with cuts on the acollinearity angle, on the energy of the outgoing fermions or on their invariant mass and angular acceptance. The new version, 4.0, includes several innovative features. First of all, the most important new capabilities since previous versions are recently computed electroweak and QCD correction factors that are relevant at the Z resonance in the light of the present experimental accuracy. Among them, the effect of the next-to-leading O α 2 m 2 t corrections and those radiative corrections to the hadronic decay of the Z which provide complete corrections of O (αα s ) to Γ(Z → qq) with q = u, d, s, c and b. Secondly, the program has been upgraded to cover two-fermion final states at LEP 2 energies, where some of the assumptions made for earlier versions are no longer valid. In particular, to this aim all the electroweak radiative corrections that are negligible at the Z peak, but relevant far from it, have been added for s-channel processes, e.g. purely weak boxes, next-to-leading O α 2 and leading O α 3 QED corrections. Keywords: e + e − annihilation, Bhabha scattering, LEP, Z resonance, electroweak, extrapolated and realistic experimental set-up, QCD corrections, QED corrections, pure weak corrections, radiative corrections, Minimal Standard Model, de-convoluted and realistic observables. 1 NEW VERSION SUMMARY2 Nature of physical problem An accurate theoretical description of e + e − annihilation processes and of Bhabha scattering for centre of mass energies at the Z resonance (LEP 1) and above (LEP 2) is necessary in order to compare theoretical cross sections and asymmetries with the experimental ones as measured by the LEP collaborations (realistic observables). In particular a realistic theoretical description, i.e. a description in which the effects of experimental cuts, such as maximum acollinearity, energy or invariant mass and angular acceptance of the outgoing fermions, are taken into account, allows the comparison of the Minimal Standard Model predictions with experimental raw data, i.e. data corrected for detector efficiency but not for acceptance. The program takes into account all the corrections, pure weak, QED and QCD, which allow for such a realistic theoretical description. The program offers also the possibility of computing the Z parameters (pseudo-observables) including the state-of-the-art of radiative corrections, which is important for the indirect determination of the fundamental Standard Model parameters. Method of solution Summary of revisions• In 1995 the CERN Repor...

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Large-angle Bhabha scattering at LEP1

Beenakker¹,

Passarino

1998

Physics Letters B

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A critical assessment is given of the theoretical uncertainty in the predicted cross-sections for large-angle Bhabha scattering at LEP 1, with or without t-channel subtraction. To this end a detailed comparison is presented of the results obtained with the programs ALIBABA and TOPAZ0. Differences in the implementation of the radiative corrections and the effect of missing higher-order terms are critically discussed. § Research supported by a fellowship of the Royal Dutch Academy of Arts and Sciences.

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Hard photon next-to-leading corrections to two-fermion production in $e^+ e^-$ collisions above the $Z^0$ peak

Cited by 3 publications

References 14 publications

Precision physics at LEP

Precision physics at LEP

TOPAZ0 4.0 — A new version of a computer program for evaluation of deconvoluted and realistic observables at LEP 1 and LEP 2

Large-angle Bhabha scattering at LEP1

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