Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userNext-to-leading-order electroweak corrections to the production of four charged leptons at the LHC
122
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We present a state-of-the-art calculation of the next-to-leading-order electroweak corrections to ZZ production, including the leptonic decays of the Z bosons into $mu^+mu^-mathrm{e}^+mathrm{e}^-$ or $mu^+mu^-mu^+mu^-$ final states. We use complete leading-order and next-to-leading-order matrix elements for four-lepton production, including contributions of virtual photons and all off-shell effects of Z bosons, where the finite Z-boson width is taken into account using the complex-mass scheme. The matrix elements are implemented into Monte Carlo programs allowing for the evaluation of arbitrary differential distributions. We present integrated and differential cross sections for the LHC at 13 TeV both for an inclusive setup where only lepton identification cuts are applied, and for a setup motivated by Higgs-boson analyses in the four-lepton decay channel. The electroweak corrections are divided into photonic and purely weak contributions. The former show the well-known pronounced tails near kinematical thresholds and resonances; the latter are generically at the level of $sim-5%$ and reach several $-10%$ in the high-energy tails of distributions. Comparing the results for $mu^+mu^-mathrm{e}^+mathrm{e}^-$ and $mu^+mu^-mu^+mu^-$ final states, we find significant differences mainly in distributions that are sensitive to the $mu^+mu^-$ pairing in the $mu^+mu^-mu^+mu^-$ final state. Differences between $mu^+mu^-mathrm{e}^+mathrm{e}^-$ and $mu^+mu^-mu^+mu^-$ channels due to interferences of equal-flavour leptons in the final state can reach up to $10%$ in off-shell-sensitive regions. Contributions induced by incoming photons, i.e. photon-photon and quark-photon channels, are included, but turn out to be phenomenologically unimportant.
rate research
Read More
The production of a neutral and a charged vector boson with subsequent decays into three charged leptons and a neutrino is a very important process for precision tests of the Standard Model of elementary particles and in searches for anomalous triple-gauge-boson couplings. In this article, the first computation of next-to-leading-order electroweak corrections to the production of the four-lepton final states $mu^+mu^- e^+ u_e$, $mu^+mu^- e^- bar u_e$, $mu^+mu^- mu^+ u_mu$, and $mu^+mu^- mu^- bar u_mu$ at the Large Hadron Collider is presented. We use the complete matrix elements at leading and next-to-leading order, including all off-shell effects of intermediate massive vector bosons and virtual photons. The relative electroweak corrections to the fiducial cross sections from quark-induced partonic processes vary between $-3%$ and $-6%$, depending significantly on the event selection. At the level of differential distributions, we observe large negative corrections of up to $-30%$ in the high-energy tails of distributions originating from electroweak Sudakov logarithms. Photon-induced contributions at next-to-leading order raise the leading-order fiducial cross section by $+2%$. Interference effects in final states with equal-flavour leptons are at the permille level for the fiducial cross section, but can lead to sizeable effects in off-shell sensitive phase-space regions.
We present an implementation of electroweak Z-boson production in association with two jets at hadron colliders in the POWHEG framework, a method that allows the interfacing of NLO-QCD calculations with parton-shower Monte Carlo programs. We focus on the leptonic decays of the weak gauge boson, and take photonic and non-resonant contributions to the matrix elements fully into account. We provide results for observables of particular importance for the suppression of QCD backgrounds to vector-boson fusion processes by means of central-jet-veto techniques. While parton-shower effects are small for most observables associated with the two hardest jets, they can be more pronounced for distributions that are employed in central-jet-veto studies.
Measuring the polarization of electroweak bosons at the LHC allows for important tests of the electroweak-symmetry-breaking mechanism that is realized in nature. Therefore, precise Standard Model predictions are needed for the production of polarized bosons in the presence of realistic kinematic selections. We formulate a method for the calculation of polarized cross-sections at NLO that relies on the pole approximation and the separation of polarized matrix elements at the amplitude level. In this framework, we compute NLO-accurate cross-sections for the production of two polarized Z bosons at the LHC, including for the first time NLO EW corrections and combining them with NLO QCD corrections and contributions from the gluon-induced process.
The production of WWZ at the LHC is an important process to test the quartic gauge couplings of the Standard Model as well as an important background for new physics searches. A good theoretical understanding at next-to-leading order (NLO) is therefore valuable. In this paper, we present the calculation of the NLO electroweak (EW) correction to this channel with on-shell gauge bosons in the final state. It is then combined with the NLO QCD correction to get the most up-to-date prediction. We study the impact of these corrections on the total cross section and some distributions. The NLO EW correction is small for the total cross section but becomes important in the high energy regime for the gauge boson transverse momentum distributions.
The dominant contribution to $H^- tbar{b}$ production at the LHC is the gluon-gluon fusion parton subprocess. We perform for the case of the complex MSSM a complete calculation of the NLO electroweak contributions to this channel. The other small contributions with quarks or photon in the initial state are calculated at tree level. The results are improved by using the effective bottom-Higgs couplings to resum the leading radiative corrections. We find that, beyond these leading corrections, the NLO electroweak contributions can be still be significant. The effect of the complex phases of the soft-breaking parameters is found to be sizable.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
