No Arabic abstract
We study the prospect for discovering the $cgto bH^+to b A W^+$ process at the LHC. Induced by the top-flavor changing neutral Higgs coupling $rho_{tc}$, the process may emerge if $m_{H^+} > m_A + m_{W^+}$, where $H^+$ and $A$ are charged and $CP$-odd Higgs bosons in the general two Higgs Doublet Model (g2HDM). We show that the $cgto bH^+to b A W^+$ process can be discovered at LHC Run 3, while the full Run 2 data at hand can constrain the parameter space significantly by searching for the same-sign dilepton final state. The process has unique implications on the hint of $ggto A to t bar t$ excess at $m_Aapprox 400$ GeV reported by CMS. When combined with other existing constraints, the $cgto bH^+to b A W^+$ process can essentially rule out the g2HDM explanation of such an excess.
Precision studies of the production of a high-transverse momentum lepton in association with missing energy at hadron colliders require that electroweak and QCD higher-order contributions are simultaneously taken into account in theoretical predictions and data analysis. Here we present a detailed phenomenological study of the impact of electroweak and strong contributions, as well as of their combination, to all the observables relevant for the various facets of the $psmartpap to {rm lepton} + X$ physics programme at hadron colliders, including luminosity monitoring and Parton Distribution Functions constraint, $W$ precision physics and search for new physics signals. We provide a theoretical recipe to carefully combine electroweak and strong corrections, that are mandatory in view of the challenging experimental accuracy already reached at the Fermilab Tevatron and aimed at the CERN LHC, and discuss the uncertainty inherent the combination. We conclude that the theoretical accuracy of our calculation can be conservatively estimated to be about 2% for standard event selections at the Tevatron and the LHC, and about 5% in the very high $W$ transverse mass/lepton transverse momentum tails. We also provide arguments for a more aggressive error estimate (about 1% and 3%, respectively) and conclude that in order to attain a one per cent accuracy: 1) exact mixed ${cal O}(alpha alpha_s)$ corrections should be computed in addition to the already available NNLO QCD contributions and two-loop electroweak Sudakov logarithms; 2) QCD and electroweak corrections should be coherently included into a single event generator.
We present hadron-level predictions from the Monte Carlo generator Cascade and numerical level calculations of beauty quark and inclusive b-jet production in the framework of the kT -factorization QCD approach for CERN LHC energies. The unintegrated gluon densities in a proton are determined using the CCFM evolution equation and the Kimber- Martin-Ryskin (KMR) prescription. We study the theoretical uncertainties of our calcula- tions and investigate the effects coming from parton showers in initial and final states. Our predictions are compared with the recent data taken by the CMS collaboration.
We calculate the production of a W boson and a single b jet to next-to-leading order in QCD at the Fermilab Tevatron and the CERN Large Hadron Collider. Both exclusive and inclusive cross sections are presented. We separately consider the cross section for jets containing a single b quark and jets containing a b-anti b pair. There are a wide variety of processes that contribute, and it is necessary to include them all in order to have a complete description at both colliders.
We study the impact of anomalous gauge boson and fermion couplings on the production of $W^+W^-$ pairs at potential future LHC upgrades and estimate the sensitivity at $sqrt{S}=14$ TeV with $3~ab^{-1}$ and $sqrt{S}=27$ TeV with $15~ab^{-1}$. A general technique for including NLO QCD effects in effective field theory (EFT) fits to kinematic distributions is presented, and numerical results are given for $sqrt{S}=13$ TeV $W^+W^-$ production. Our method allows fits to anomalous couplings at NLO accuracy in any EFT basis and has been implemented in a publicly available version of the POWHEG-BOX. Analytic expressions for the $K$-factors relevant for $13$ TeV total cross sections are given for the HISZ and Warsaw EFT bases and differential $K$-factors can be obtained using the supplemental material. Our study demonstrates the necessity of including anomalous $Z$- fermion couplings in the extraction of limits on anomalous 3-gauge-boson couplings.
We investigate the impact of parton distribution functions (PDFs) uncertainties on W/Z production at the LHC, concentrating on the strange quark PDF. Additionally we examine the extent to which precise measurements at the LHC can provide additional information on the proton flavor structure.