Large angle pair production in colliding beam experiments

Baier, V.N.; Fadin, V.S.

doi:10.1051/jphyscol:1974218

Cited by 3 publications

(5 citation statements)

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“…In this paper, we have presented analytic formulae for the two-loop virtual corrections to the process γ * → q qg, which arise from the interference of the two-loop with the tree amplitude and from the self-interference of the one-loop amplitude. Together with the contribution from the self-interference of the one-loop amplitudes for γ * → ggg [45,46], these form the full O(α 3 s ) corrections to the three-parton subprocess contribution to e + e − → 3 jets at NNLO.…”

Section: Discussionmentioning

confidence: 99%

“…At the same order in α s , one finds also a contribution to three-jet final states from the self-interference of the γ * → ggg amplitude. The matrix element for this process does not contain infrared or ultraviolet divergences; it was computed long ago and can be found in [45,46]. For the remainder of this paper we will set the renormalization scale µ 2 = q 2 .…”

Section: Notationmentioning

confidence: 99%

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The two-loop QCD matrix element for e+e−→3 jets

et al. 2002

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We compute the O(α 3 s ) virtual QCD corrections to the γ * → qqg matrix element arising from the interference of the two-loop with the tree-level amplitude and from the self-interference of the one-loop amplitude. The calculation is performed by reducing all loop integrals appearing in the two-loop amplitude to a small set of known master integrals. Infrared and ultraviolet divergences are both regularized using conventional dimensional regularization, and the ultraviolet renormalization is performed in the MS scheme. The infrared pole structure of the matrix elements agrees with the prediction made by Catani using an infrared factorization formula. The analytic result for the finite terms of both matrix elements is expressed in terms of one-and two-dimensional harmonic polylogarithms.Among jet observables, the three-jet production rate in electron-positron annihilation plays an outstanding role. The initial experimental observation of three-jet events at PETRA [1], in agreement with the theoretical prediction [2], provided first evidence for the gluon, and thus strong support for the theory of Quantum Chromodynamics (QCD). Subsequently the three-jet rate and related event shape observables were used for the precise determination of the QCD coupling constant α s (see [3] for a review). Especially at LEP, three-jet observables were measured to a very high precision and the error on the extraction of α s from these data is dominated by the uncertainty inherent in the theoretical next-to-leading order (NLO) calculation [4][5][6][7][8] of the jet observables. The planned TESLA [9] linear e + e − collider will allow precision QCD studies at even higher energies than at LEP. Given the projected luminosity of TESLA, one again expects the experimental errors to be well below the uncertainty of the NLO calculation.Related to e + e − → 3 jets by crossing symmetry are (2+1)-jet production in deep inelastic ep scattering and vector-boson-plus-jet production at hadron colliders. The experimental data from HERA on ep → (2 + 1) jets and related event shape observables have already reached a level of precision demanding predictions beyond the present NLO accuracy; a further improvement on these data is expected soon from the HERA high luminosity programme. Similarly, vector-boson production at large transverse momentum is a classic test of QCD in hadron-hadron collisions and demands the theoretical prediction to be as precise as possible. In this case, it is also an important background in searches for new physics at the Tevatron and the LHC.Besides its phenomenological importance, the three-jet rate has also served as a theoretical testing ground for the development of new techniques for higher order calculations in QCD: both the subtraction [4] and the phase-space slicing [5] methods for the extraction of infrared singularities from NLO real radiation processes were developed in the context of the first three-jet calculations. The systematic formulation of phase-space slicing [7] as well as the dipole subtraction [8] method w...

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Section: Discussionmentioning

confidence: 99%

Section: Notationmentioning

confidence: 99%

The two-loop QCD matrix element for e+e−→3 jets

et al. 2002

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“…The leadingorder scattering amplitudes for these processes all involve a closed quark loop. The resulting gluon-induced contributions from one-loop squared [1][2][3] processes (that appear only at next-to-next-to-leading order in the formal perturbative expansion of the full process) were evaluated a long time ago [4][5][6][7][8], and typically found to yield a contribution that amounts to 10-20% of the total cross section. Inclusion of these gluon-gluon subprocess contributions often results in an enhanced theoretical uncertainty on the prediction, since the one-loop squared process is effectively Born-level for this combination of partons.…”

Section: Introductionmentioning

confidence: 99%

Two-loop QCD helicity amplitudes for $g\,g \to Z\,g$ and $g\,g \to Z\,γ$

Gehrmann,

Tancredi,

Weihs

2013

Preprint

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“…The next stage is to square the resulting matrix element and make the average over the O ps polarization states [5]. After simple calculations, similar to those performed in the paper of one of us [19], -where the production of tree gluonic jets in electron-positron colliding beams was considered-, we obtain the following contribution to the width 3 :…”

Section: Discussionmentioning

confidence: 99%

“…We write here the explicit expressions for the quantity R(234) entering the tensor G. Accommodation from the results of paper [20] to the annihilation channel was done in the paper [19].…”

Section: B Appendix Bmentioning

confidence: 99%

Some ${\rm O}(\alpha^2)$ annihilation type contributions to the orthopositronium width

et al. 1998

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We consider some radiative corrections to the lowest order annihilation diagram for the orthopositronium decay rate. The insertion of the renormalized vertex correction in the annihilation graph gives 1.6283 (α/π) 2 Γ 0 . We compute also the contribution of the square of the lowest order annihilation amplitude, which turns out to be 0.1702 (α/π) 2 Γ 0 . Finally, we obtain a term α 2 ln α Γ 0 arising from the correction to the light-light scattering block due to the exchange of one coulombic photon, in agreement with earlier computations.

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Large angle pair production in colliding beam experiments

Cited by 3 publications

References 0 publications

The two-loop QCD matrix element for e+e−→3 jets

The two-loop QCD matrix element for e+e−→3 jets

Two-loop QCD helicity amplitudes for $g\,g \to Z\,g$ and $g\,g \to Z\,γ$

Some ${\rm O}(\alpha^2)$ annihilation type contributions to the orthopositronium width

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