Electroweak corrections and anomalous triple gauge-boson couplings in WW and WZ production at the LHC

We have analysed the production of WW and WZ vector-boson pairs at the LHC. These processes give rise to four-fermion final states, and are particularly sensitive to possible non-standard trilinear gauge-boson couplings. We have studied the interplay between the influence of these anomalous couplings and the effect of the complete logarithmic electroweak O(\alpha) corrections. Radiative corrections to the Standard Model processes in double-pole approximation and non-standard terms due to trilinear couplings are implemented into a Monte Carlo program for p p -> 4f (+\gamma) with final states involving four or two charged leptons. We numerically investigate purely leptonic final states and find that electroweak corrections can fake new-physics signals, modifying the observables by the same amount and shape, in kinematical regions of statistical significance.Comment: 19 pages, LaTex, 12 eps figure

Precision predictions for W-pair production at LEP2

Theoretical calculations for the W-pair production process at LEP2 in terms of Monte Carlo event generators RacoonWW and KorlaW&YFSWW3 are reviewed. The discussion concentrates on precision predictions for the main LEP2 WW observables. The theoretical precision of the above programs is estimated to be ~0.5% for the total WW cross section sigma_{WW}, ~5MeV for the W-boson mass M_W, and ~0.005 for the triple-gauge-boson coupling lambda = lambda_{gamma} = lambda_Z, which is sufficient for the final LEP2 data analyses.Comment: 9 pages, LaTe

Four-fermion production with RACOONWW

RACOONWW is an event generator for e+e- --> WW --> 4fermions(+gamma) that includes full tree-level predictions for e+e- --> 4f and e+e- --> 4f+gamma as well as O(alpha) corrections to e+e- --> 4f in the so-called double-pole approximation. We briefly sketch the concept of the calculation on which this generator is based and present some numerical results.Comment: 9 pages, latex, 6 postscript files, to appear in the proceedings of the UK Phenomenology Workshop on Collider Physics, Durham, UK, 19-24 September, 199

Electroweak-correction effects in gauge-boson pair production at the LHC

We have studied the effect of one-loop logarithmic electroweak radiative corrections on WZ and $W\gamma$ production processes at the LHC. We present analytical results for the leading-logarithmic electroweak corrections to the corresponding partonic processes du -> WZ, Wgamma. Using the leading-pole approximation we implement these corrections into Monte Carlo programs for $pp\to l\nu_l l'\bar l', l\nu_l\gamma$. We find that electroweak corrections lower the predictions by 5-20% in the physically interesting region of large transverse momentum and small rapidity separation of the gauge bosons.Comment: 28 pages, LaTex, 13 eps figures included; references added and corrected typo

Weak radiative corrections to the Drell-Yan process for large invariant mass of a dilepton pair

The weak radiative corrections to the Drell-Yan process above the Z-peak have been studied. The compact asymptotic expression for the two heavy boson exchange - one of the significant contributions to the investigated process - has been obtained, the results expand in the powers of the Sudakov electroweak logarithms. At the quark level we compare the weak radiative corrections to the total cross section and forward-backward asymmetry with the existing results and achieve a rather good coincidence at \sqrt{s}>= 0.5 TeV. The numerical analysis has been performed in the high energy region corresponding to the future experiments at the CERN Large Hadron Collider (LHC). To simulate the detector acceptance we used the standard CMS detector cuts. It was shown that double Sudakov logarithms of the WW boxes are the dominant contributions in hadronic cross section. The considered radiative corrections are significant at high dilepton mass M and change the dilepton mass distribution up to ~+3(-12)% at the LHC energies and M=1(5) TeV.Comment: Changed content; 13 pp, 4 fig, 1 tabl

Near-threshold boson pair production in the model of smeared-mass unstable particles

Near-threshold production of boson pairs is considered within the framework of the model of unstable particles with smeared mass. We describe the principal aspects of the model and consider the strategy of calculations including the radiative corrections. The results of calculations are in good agreement with LEP II data and Monte-Carlo simulations. Suggested approach significantly simplifies calculations with respect to the standard perturbative one.Comment: 15 pages, 6 figures, minor corrections, references adde

Hysteresis of Backflow Imprinted in Collimated Jets

We report two different types of backflow from jets by performing 2D special relativistic hydrodynamical simulations. One is anti-parallel and quasi-straight to the main jet (quasi-straight backflow), and the other is bent path of the backflow (bent backflow). We find that the former appears when the head advance speed is comparable to or higher than the local sound speed at the hotspot while the latter appears when the head advance speed is slower than the sound speed bat the hotspot. Bent backflow collides with the unshocked jet and laterally squeezes the jet. At the same time, a pair of new oblique shocks are formed at the tip of the jet and new bent fast backflows are generated via these oblique shocks. The hysteresis of backflow collisions is thus imprinted in the jet as a node and anti-node structure. This process also promotes broadening of the jet cross sectional area and it also causes a decrease in the head advance velocity. This hydrodynamic process may be tested by observations of compact young jets.Comment: 9 pages, 5 figures, accepted for publication in ApJ

Charged Higgs Production in the 1 TeV Domain as a Probe of Supersymmetric Models

We consider the production, at future lepton colliders, of charged Higgs pairs in supersymmetric models. Assuming a relatively light SUSY scenario, and working in the MSSM, we show that, for c.m. energies in the one TeV range, a one-loop logarithmic Sudakov expansion that includes an "effective" next-to subleading order term is adequate to the expected level of experimental accuracy. We consider then the coefficient of the linear (subleading) SUSY Sudakov logarithm and the SUSY next to subleading term of the expansion and show that their dependence on the supersymmetric parameters of the model is drastically different. In particular the coefficient of the SUSY logarithm is only dependent on $\tan\beta$ while the next to subleading term depends on a larger set of SUSY parameters. This would allow to extract from the data separate informations and tests of the model.Comment: 18 pages and 13 figures e-mail: [email protected]

Top Quark Production at TeV Energies as a Potential SUSY Detector

We consider the process of top-antitop production from electron-positron annihilation, for c. m. energies in the few TeV regime, in the MSSM theoretical framework. We show that, at the one loop level, the \underline{slopes} of a number of observable quantities in an energy region around 3 TeV are only dependent on $\tan\beta$. Under optimal experimental conditions, a combined measurement of slopes might identify $\tan\beta$ values in a range $\tan\beta< 2$, $\tan\beta>20$ with acceptable precision.Comment: 14 pages, 6 Encapsulated PostScript figure

Electroweak effects in top-quark pair production at Hadron Colliders

Top-quark physics plays an important role at hadron colliders such as the Tevatron collider at Fermilab or the upcoming Large Hadron Collider (LHC) at CERN. Given the planned experimental precision, detailed theoretical predictions are mandatory. In this article we present analytic results for the complete electroweak corrections to gluon induced top-quark pair production, completing our earlier results for the quark-induced reaction. As an application we discuss top-quark pair production at Tevatron and at LHC. In particular we show that, although small for inclusive quantities, weak corrections can be sizeable for differential distribution