Electroweak radiative corrections in precision LHC measurements of W±/Z0+jets

We calculate the fiducial and differential $W^{\pm}/Z^0+jet(s)$ production cross-sections in the presence of electroweak (EW) corrections through virtual loop contributions to the matrix elements (MEs) of the processes and real partonic cascade emissions. The calculations are carried out for proton-proton collisions at $\sqrt{s} = 13$ TeV, using Herwig 7 general-purpose Monte-Carlo event generator with leading-order or next-to-leading-order MEs that are interfaced with different parton-shower configurations. The results are compared with precision experimental measurements from ATLAS collaboration and with similar predictions within the $k_t$-factorisation framework, providing a test for the validity of the newly-implemented QCD$\oplus$QED$\oplus$EW parton shower in Herwig 7. It is shown that the inclusion of EW radiations in the parton shower simulations improves Herwig 7's predictions in describing the experimental data. Additionally, the inclusion of parton shower-induced real EW emissions can take precedence over the incorporation of virtual EW corrections for the simulation of EW-sensitive events.Comment: 21 pages, 9 figures and 1 tabl

The forward physics facility at the high-luminosity LHC

High energy collisions at the High-Luminosity Large Hadron Collider (LHC) produce a large number of particles along the beam collision axis, outside of the acceptance of existing LHC experiments. The proposed Forward Physics Facility (FPF), to be located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, will host a suite of experiments to probe standard model (SM) processes and search for physics beyond the standard model (BSM). In this report, we review the status of the civil engineering plans and the experiments to explore the diverse physics signals that can be uniquely probed in the forward region. FPF experiments will be sensitive to a broad range of BSM physics through searches for new particle scattering or decay signatures and deviations from SM expectations in high statistics analyses with TeV neutrinos in this low-background environment. High statistics neutrino detection will also provide valuable data for fundamental topics in perturbative and non-perturbative QCD and in weak interactions. Experiments at the FPF will enable synergies between forward particle production at the LHC and astroparticle physics to be exploited. We report here on these physics topics, on infrastructure, detector, and simulation studies, and on future directions to realize the FPF's physics potential

Implementation of angularly ordered electroweak parton shower in Herwig 7

We discuss the necessary steps for implementing an angularly ordered (AO) electroweak (EW) parton shower in Herwig 7 multi-purpose event generator. This includes calculating the helicity-dependent quasi-collinear EW branching functions that correspond to the full range of final-state EW parton shower, in addition to the initial-state EW gauge vector boson radiations. The results are successfully embedded in the AO Herwig 7 shower algorithm and have undergone a set of comprehensive and conclusive performance tests. Furthermore, we have used this EW parton shower algorithm, alongside the existing QCD + QED AO shower, to predict the angular distributions of W± bosons in LHC events with high transverse momentum jets. These results are compared against the explicitly generated underlying events as well as the existing ATLAS data to show the effectiveness of the newly implemented QCD + QED + EW AO parton shower scheme

Higgs-Sector Predictions from Maximally Symmetric multi-Higgs Doublet Models

Maximally Symmetric n-Higgs Doublet Models (MS-nHDMs) define very economic settings that enable sharp Higgs-sector predictions beyond the Standard Model (SM) potentially testable at high-energy colliders. The scalar potential of a MS-nHDM obeys an Sp(2n) symmetry, which is softly broken by bilinear scalar masses and explicitly by hypercharge and Yukawa couplings through renormalisation-group effects. The Sp(2n) also ensures natural SM alignment and allows for quartic coupling unification up to the Planck scale. As typical examples, we consider maximally symmetric realisations of the Type-II 2HDM and the Type-V 3HDM. We show how in terms of a few input parameters, definite predictions for the entire scalar mass spectrum of the MS-2HDM and MS-3HDM are obtained, including the SM-like Higgs-boson couplings to the gauge bosons and fermions.Maximally Symmetric $n$-Higgs Doublet Models (MS-$n$HDMs)define very economic settings that enable sharp Higgs-sector predictions beyond the Standard Model (SM) potentially testable at high-energy colliders. The scalar potential of a MS-$n$HDM obeys an $\mathrm{Sp(2}n)$ symmetry, which is softly broken by bilinear scalar masses and explicitly by hypercharge and Yukawa couplings through renormalisation-group effects. The $\mathrm{Sp(2}n)$ also ensures natural SM alignment and allows for quartic coupling unification up to the Planck scale. As typical examples, we consider maximally symmetric realisations of the Type-II 2HDM and the Type-V 3HDM. We show how in terms of a few input parameters, definite predictions for the entire scalar mass spectrum of the MS-2HDM and MS-3HDM are obtained, including the SM-like Higgs-boson couplings to the gauge bosons and fermions

LHC production of forward-center and forward-forward di-jets in the kt-factorization and transverse dependent unintegrated parton distribution frameworks

The present work is devoted to study the high-energy QCD events, such as the di-jet productions from proton–proton inelastic collisions at the LHC in the forward-center and the forward-forward configurations. This provides us with much valuable case study, since such phenomena can provide a direct glimpse into the partonic behavior of a hadron in a dominant gluonic region. We use the unintegrated parton distribution functions (UPDF) in the kt-factorization framework. The UPDF of Kimber et al. (KMR) and Martin et al. (MRW) are generated in the leading order (LO) and next-to-leading order (NLO), using the Harland-Lang et al. (MMHT2014) PDF libraries. While working in the forward-center and the forward-forward rapidity sectors, one can probe the parton densities at very low longitudinal momentum fractions (x). Such a model computation can provide simpler analytic description of data with respect to existing formalisms such as perturbative QCD. The differential cross-section calculations are performed at the center of mass energy of 7 TeV corresponding to CMS collaboration measurement. It is shown that the gluonic jet productions are dominant and a good description of data as well as other theoretical attempts (i.e. KS-linear, KS-nonlinear and rcBK) is obtained. The uncertainty of the calculations is derived by manipulating the hard scale of the processes by a factor of two. This conclusion is achieved, due to the particular visualization of the angular ordering constraint (AOC), that is incorporated in the definition of these UPDF

Semi-NLO production of Higgs bosons in the framework of kt-factorization using KMR unintegrated parton distributions

The cross-section for the production of the Standard Model Higgs boson has been calculated using a mixture of LO and NLO partonic diagrams and the unintegrated parton distribution functions (UPDF) of the Kimber–Martin–Ryskin (KMR) from the kt-factorization framework. The UPDF are prepared using the phenomenological libraries of Martin–Motylinski–Harland Lang–Thorne (MMHT2014). The results are compared against the existing experimental data from the CMS and the ATLAS collaborations and available pQCD calculation. It is shown that, while the present calculation is in agreement with the experimental data, it is comparable with the pQCD results. It is also concluded that the K-factor approximation is comparable with the semi-NLO kt-factorization predictions