Hard photon effects inW � andZ 0 decay

Berends, F.A.; Kleiss, R.

doi:10.1007/bf01548639

Cited by 130 publications

(196 citation statements)

References 8 publications

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“…In first-order QED [Ber85] and in some simple QCD toy models [Got86], one may show that the 'correct' choice is the 'ŝ approach'. Here one requires thatŝ = x 1 x 2 s, both at the hard scattering scale and at any lower scale, i.e.ŝ(Q 2 ) = x 1 (Q 2 ) x 2 (Q 2 ) s, where x 1 and x 2 are the x values of the two resolved partons (one from each incoming beam particle) at the given Q 2 scale.…”

Section: Transverse Evolutionmentioning

confidence: 99%

PYTHIA 6.4 physics and manual

Sjöstrand

Mrenna

Skands

2006

J. High Energy Phys.

9,675

10,151

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The Pythia program can be used to generate high-energy-physics 'events', i.e. sets of outgoing particles produced in the interactions between two incoming particles. The objective is to provide as accurate as possible a representation of event properties in a wide range of reactions, with emphasis on those where strong interactions play a rôle, directly or indirectly, and therefore multihadronic final states are produced. The physics is then not understood well enough to give an exact description; instead the program has to be based on a combination of analytical results and various QCDbased models. This physics input is summarized here, for areas such as hard subprocesses, initial-and final-state parton showers, beam remnants and underlying events, fragmentation and decays, and much more. Furthermore, extensive information is provided on all program elements: subroutines and functions, switches and parameters, and particle and process data. This should allow the user to tailor the generation task to the topics of interest.

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Section: Transverse Evolutionmentioning

confidence: 99%

PYTHIA 6.4 physics and manual

Sjöstrand

Mrenna

Skands

2006

J. High Energy Phys.

9,675

10,151

View full text Add to dashboard Cite

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“…The leading initial-state radiation effects due to large logarithms, L = log s/m 2 e , can be included using the structure-function approach [7], (3) with the structure functions up to order O(α 2 L 2 ) * and including soft-photon exponentiation given by [8] …”

Section: Direct Z ′ Productionmentioning

confidence: 99%

“…While it is not possible to directly resolve the resonance line-shape of the Z ′ boson, as pointed out above, it is still possible to determine the mass of the boson accurately if the shape of the beam energy spectrum is precisely known. The effects of initial-state radiation have been calculated theoretically to high orders in perturbation theory [8,9], so that the remaining theoretical uncertainty is negligible. The beamstrahlung effects due to interactions between the two incoming beams can be either obtained from numerical simulations based on theoretical models [12] or directly measured using Bhabha scattering [24].…”

Section: Parameter Determinationmentioning

confidence: 99%

Weakly coupled neutral gauge bosons at future linear colliders

Freitas

2004

Phys. Rev. D

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A weakly coupled new neutral gauge boson forms a narrow resonance that is hard to discover directly in e + e − collisions. However, if the gauge boson mass is below the center-of-mass energy, it can be produced through processes where the effective energy is reduced due to initial-state radiation and beamstrahlung. It is shown that at a high-luminosity linear collider, such a gauge boson can be searched for with very high sensitivity, leading to a substantial improvement compared to existing limits from the Tevatron and also extending beyond the expected reach of the LHC in most models. If a new vector boson is discovered either at the Tevatron Run II, the LHC or the linear collider, its properties can be determined at the linear collider with high precision, thus helping to reveal origin of the new boson.

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“…The calculation proceeds in analogy to the corresponding QED process [7,8]. The interference terms corresponding to real emission ( Fig.…”

mentioning

confidence: 99%

Charge Asymmetry in Hadroproduction of Heavy Quarks

1998

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A sizeable difference in the differential production cross section of top and antitop quarks, respectively, is predicted for hadronically produced heavy quarks. It is of order αs and arises from the interference between charge odd and even amplitudes respectively. For the TEVATRON it amounts up to 15% for the differential distribution in suitable chosen kinematical regions. The resulting integrated forward-backward asymmetry of 4-5% could be measured in the next round of experiments. At the LHC the asymmetry can be studied by selecting appropriately chosen kinematical regions.12.38. Bx, 12.38.Qk, 13.87.Ce, 14.65.Ha Top quark production at hadron colliders has become one of the central issues of theoretical [1] and experimental [2] research. The investigation and understanding of the production mechanism is crucial for the determination of the top quark couplings, its mass and the search for new physics involving the top system. A lot of effort has been invested in the prediction of the total cross section and, more recently, of inclusive transverse momentum distributions [1].In this work we will point to a different aspect of the hadronic production process, which can be studied with a fairly modest sample of quarks. Top quarks produced through light quark-antiquark annihilation will exhibit a sizeable charge asymmetry -an excess of top versus antitop quarks in specific kinematic regions -induced through the interference of the final-state with initial-state radiation (Fig. 1 a, b) and the interference of the box with the lowest-order-diagram ( Fig. 1 c, d). The asymmetry is thus of order α s relative to the dominant production process. In suitable chosen kinematical regions it reaches up to 15%, the integrated forward-backward asymmetry amounts to 4-5%. Top quarks are tagged through their decay t → b W + and can thus be distinguished experimentally from antitop quarks through the sign of the lepton in the semileptonic mode and eventually also through the b-tag. A sample of hundred to two hundred tagged top quarks should in fact be sufficient for a first indication of the effect. Top production at the TEVATRON is dominated by quark-antiquark annihilation, hence the charge asymmetry will be reflected not only in the partonic rest frame but also in the center of mass system of proton and antiproton. The situation is more intricate for proton-proton collisions at the LHC, where no preferred direction is at hand in the laboratory frame. Nevertheless it is also in this case possible to pick kinematical configurations which allow the study of the charge asymmetry.The charge asymmetry has also been investigated in [3] for a top mass of 45 GeV. There, however, only the contribution from real gluon emission was considered requiring the introduction of a physical cutoff on the gluon energy and rapidity to avoid infrared and collinear singularities. Experimentally, however, only inclusive top-antitop 1

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Hard photon effects inW � andZ 0 decay

Cited by 130 publications

References 8 publications

PYTHIA 6.4 physics and manual

PYTHIA 6.4 physics and manual

Weakly coupled neutral gauge bosons at future linear colliders

Charge Asymmetry in Hadroproduction of Heavy Quarks

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