Higher-order QED corrections to single-W production in electron–positron collisions

Montagna, G.; Moretti, M.; Nicrosini, O.; Pallavicini, Andrea; Piccinini, F.

doi:10.1007/s100520100673

Cited by 8 publications

(7 citation statements)

References 27 publications

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“…For small angle Bhabha scattering and multi-peripheral γ γ processes, where exact QED radiative corrections are already known, the full prediction and the result obtained by using SF at the scale |q 2 γ | are in good agreement [31]. In all other cases, where no exact calculation is available, it has been recently shown that a comparison with the soft limit of the O(α) corrections can determine the scales to be used in SF and PS [32,33]. Detailed analysis, concerning the sensitivity of t-channel scatterings to the choice of the energy scale in the presence of ISR, have been performed [15,32,33], leading to a better understanding of the behaviour of the radiation for single W and γ γ processes.…”

Section: Initial State Radiationmentioning

confidence: 52%

“…WPHACT, grc4f [7], KORALW [12] and COMPHEP [13] are based on Feynman diagrams 1 while NEXTCALIBUR [15] and SWAP [16] are based on the Dyson-Schwinger equations, a set of recursive relations among Green functions. Comparisons between the different codes have shown good technical agreement in several benchmark processes, as recently summarized in [17].…”

Section: Introductionmentioning

confidence: 99%

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WPHACT 2.0: A fully massive Monte Carlo generator for four fermion physics at e+e− colliders

Accomando¹,

Ballestrero²,

Maina³

2003

Computer Physics Communications

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WPHACT 2.0 is the new fully massive version of a MC program and unweighted event generator which computes all Standard Model processes with four fermions in the final state at e + e − colliders. The program can now generate unweighted events for any subset of all four fermion final states in a single run, by making use of dedicated pre-samples which can cover the entire phase space. Improvements with respect to WPHACT 1.0 include the Imaginary Fermion Loop gauge restoring scheme, new phase space mappings, a new input system, the possibility to compute subsets of Feynman diagrams and options for including ISR via QEDPS, running α QED , CKM mixing, resonances in qq channels.  2002 Elsevier Science B.V. All rights reserved. PROGRAM SUMMARY Method of solutionFull tree level matrix elements for all processes are computed by means of subroutines which make use of the helicity formalism of Refs. [24,25]. The speed in computing these amplitudes, that the above mentioned method allows, is essential to take exactly into account fermion masses and to obtain high precision in a reasonable amount of CPU time also in regions with large and possibly overlapping enhancements. Reasons for the new versionExtend the code to cover in a reliable way all t-channel dominated processes and low ff invariant mass regions. Introduce the possibility to simultaneously generate unweighted events for all processes or any user-selected subset. Include photon p t and CKM mixing. Summary of revisions Typical running timeThe running time strongly depends on the process considered and on the precision requested. The example reported in the test run took about 90 minutes on a 500 MHz ALPHA computer, which corresponds to effectively generating more than 1500 weighted e − e + µ − µ + events per second.Unusual features of the program STRUCTURE declarations are used.

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Section: Initial State Radiationmentioning

confidence: 52%

Section: Introductionmentioning

confidence: 99%

WPHACT 2.0: A fully massive Monte Carlo generator for four fermion physics at e+e− colliders

Accomando¹,

Ballestrero²,

Maina³

2003

Computer Physics Communications

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“…In the second run, for each event use KoralW in order to calculate the correction weight, the bracketed expression in Eq. (12). Optionally, reject the events according to the correction weight.…”

Section: Merge For Fully Exclusive Distributions (Event Per Event)mentioning

confidence: 99%

“…For example KoralW [1,[4][5][6] can generate all four-fermion final states with the fully massive phase space and the complete Born-level four-fermion massive matrix element generated by the GRACE2 package [7]. Apart from KoralW there exists a number of other MC programs for all four-fermion processes at the Born level [8][9][10][11][12][13][14][15][16][17][18][19]. The complete O(α) corrections to the signal e + e − → W + W − → 4f process are implemented only in two MC programs: YFSWW3 [2,[20][21][22][23] and RacoonWW [24,25].…”

Section: Introductionmentioning

confidence: 99%

The Monte Carlo program KoralW version 1.51 and the concurrent Monte Carlo KoralW&YFSWW3 with all background graphs and first-order corrections to W-pair production

Jadach

Płaczek

Skrzypek

et al. 2001

Computer Physics Communications

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The version 1.51 of the Monte Carlo (MC) program KoralW for all e + e − → f 1f2 f 3f4 processes is presented. The most important change from the previous version 1.42 is the facility for writing MC events on the mass storage device and reprocessing them later on. In the reprocessing parameters of the Standard Model may be modified in order to fit them to experimental data. Another important new feature is the possibility of including complete O(α) corrections to doubleresonant W -pair component-processes in addition to all background (non-W W ) graphs. The inclusion is done with the help of the YFSWW3 MC event generator for fully exclusive differential distributions (event per event). Technically, it is done in such a way that YFSWW3 runs concurrently with KoralW as a separate slave process, reading momenta of the MC event generated by KoralW and returning the correction weight to KoralW. The latter introduces the O(α) correction using this weight, and finishes processing the event (rejection due to total MC weight, hadronization, etc. Nature of the physical problem:The precise study of W -pair production and decay at LEP2 requires both non-doubleresonant and O(α) corrections. So far each of these corrections is available as a separate Monte Carlo program and there is no Monte Carlo that could simulate in a complete way both effects at the same time. Such a MC event generator would be of importance for example for apparatus simulations or Monte Carlo based fits. The previous version of KoralW [1] included all non-double-resonant corrections to all double-resonant fourfermion processes in e + e − annihilation. The present version 1.51 allows, for the first time ever, the inclusion on an event-per-event basis of the respective O(α) corrections generated at the same time by the independently running Monte Carlo program YFSWW3 [2], as well as a reweighting of any earlier generated events with modified parameter sets. Method of solution:The Monte Carlo method used to simulate the all four-fermion final-state processes in the e + e − collisions in the presence of multiphoton initial-state radiation has not changed since version 1.42 [1]. Adding the O(α) corrections generated by YFSWW3 is done at the level of the UNIX/Linux operating system with the help of the FIFO mechanism ("named pipes"). Typical running time:Approximate times on a PC Pentium III @ 800 MHz for cuts as described in this article: 5 minutes per 1000 constant-weight CCall events (KoralW stand-alone) 50 minutes per 1000 constant-weight CCall events with the O(α) correction (the CMC KoralW&YFSWW3, max. weight for rejection increased by a factor 2).

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“…[4] and in ref. [5] More or less, all these attempts amount to start with some sort of naive soft + virtual photon approximation, not the one commonly employed in the Yennie, Frautschi and Suura formalism [6], but rather something as in the following expression:…”

Section: Background Of the Problemmentioning

confidence: 99%

A practical approach for exponentiation of QED corrections in arbitrary processes

Passarino¹

2001

Nuclear Physics B

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It is a well-known fact that, among the electroweak corrections, QED radiation gives the largest contribution and the needed precision requires a re-summation of the large logarithms which show up in perturbation theory. For annihilation processes, e + e − → f f , initial state radiation is a definable, gauge-invariant, concept and one has general tools to deal with it; the structure function approach and also the parton-shower method. However, when one tries to apply the algorithm to four-fermion processes that include non-annihilation channels a problem is faced: is it still possible to include QED corrections by making use of the standard tools? A systematization is attempted of several, recently proposed, algorithms. In particular, it is shown that starting from the exponentiation of soft photons one can still derive a description of QED radiation in terms of structure functions, i.e. the kernel for the hard scattering is convoluted with generalized structure functions where each of them is no longer function of one scale. Each external, charged, fermion leg brings a factor x αA−1 where α is the fine-structure constant, 0 ≤ x ≤ 1 and A is a function which depends on the momenta of the charged particles.

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Higher-order QED corrections to single-W production in electron–positron collisions

Cited by 8 publications

References 27 publications

WPHACT 2.0: A fully massive Monte Carlo generator for four fermion physics at e+e− colliders

WPHACT 2.0: A fully massive Monte Carlo generator for four fermion physics at e+e− colliders

The Monte Carlo program KoralW version 1.51 and the concurrent Monte Carlo KoralW&YFSWW3 with all background graphs and first-order corrections to W-pair production

A practical approach for exponentiation of QED corrections in arbitrary processes

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