Dorival Goncalves

Scalar Simplified Models for Dark Matter

We introduce a set of minimal simplified models for dark matter interactions with the Standard Model, connecting the two sectors via either a scalar or pseudoscalar particle. These models have a wider regime of validity for dark matter searches at the LHC than the effective field theory approach, while still allowing straightforward comparison to results from non-collider dark matter detection experiments. Such models also motivate dark matter searches in multiple correlated channels. In this paper, we constrain scalar and pseudoscalar simplified models with direct and indirect detection experiments, as well as from existing LHC searches with missing energy plus tops, bottoms, or jets, using the exact loop-induced coupling with gluons. This calculation significantly affects key differential cross sections at the LHC, and must be properly included. We make connections with the Higgs sector, and conclude with a discussion of future searches at the LHC.

The Higgs legacy of the LHC Run I

A bstractBased on Run I data we present a comprehensive analysis of Higgs couplings. For the first time this SFitter analysis includes independent tests of the Higgs-gluon and top Yukawa couplings, Higgs decays to invisible particles, and off-shell Higgs measurements. The observed Higgs boson is fully consistent with the Standard Model, both in terms of coupling modifications and effective field theory. Based only on Higgs total rates the results using both approaches are essentially equivalent, with the exception of strong correlations in the parameter space induced by effective operators. These correlations can be controlled through additional experimental input, namely kinematic distributions. Including kinematic distributions the typical Run I reach for weakly interacting new physics now reaches 300 to 500 GeV.

Mass effects in the Higgs-gluon coupling: boosted vs. off-shell production

A bstractIn the upcoming LHC run we will be able to probe the structure of the loopinduced Higgs-gluon coupling through kinematics. First, we establish state-of-the-art simulations with up to two jets to next-to-leading order including top mass effects. They allow us to search for deviations from the low-energy limits in boosted Higgs production. In addition, the size of the top mass effects suggests that they should generally be included in Higgs studies at the LHC. Next, we show how off-shell Higgs production with a decay to four leptons is sensitive to the same top mass effects. We compare the potential of both methods based on the same top-Higgs Lagrangian. Finally, we comment on related model assumptions required for a Higgs width measurement.

Resolving the Higgs-gluon coupling with jets

In the Standard Model, the Higgs coupling to gluons is almost entirely induced by top quark loops. We derive the logarithmic structure of Higgs production in association with two jets. Just like in the one-jet case, the transverse momentum distributions exhibit logarithms of the top quark mass and can be used to test the nature of the loop–induced Higgs coupling to gluons. Using Higgs decays to W bosons and to tau leptons, we show how the corresponding analyses hugely benefit from the second jet in the relevant signal rate as well as in the background rejection.

Simplified models for dark matter face their consistent completions

Simplified dark matter models have been recently advocated as a powerful tool to exploit the complementarity between dark matter direct detection, indirect detection and LHC experimental probes. Focusing on pseudoscalar mediators between the dark and visible sectors, we show that the simplified dark matter model phenomenology departs significantly from that of consistent SUð2ÞL × Uð1ÞY gauge invariant completions. We discuss the key physics that simplified models fail to capture, and its impact on LHC searches. Notably, we show that resonant mono-Z searches provide competitive sensitivities to standard mono-jet analyses at 13 TeV LHC.

The shape of spins

After the discovery of a Higgs-like particle at the LHC, the determination of its spin quantum numbers across different channels will be the next step in arriving at a more precise understanding of the new state and its role in electroweak symmetry breaking. Event shape observables have been shown to provide extremely sensitive observables for the discrimination of the scalar Higgs boson’s CP quantum numbers as a consequence of the different radiation patterns of Higgs production via gluon fusion vs weak boson fusion in the pp→X+2j selection. We show that a similar strategy serves to constrain the spin quantum numbers of the discovered particle as a function of the involved couplings. We also discuss the prospects of applying a similar strategy to future discoveries of Higgs-like particles.

Augmenting the diboson excess for the LHC Run II

The ATLAS collaboration recently reported an excess of events in the high invariant mass tail of reconstructed diboson events. We investigate their analysis and point to possible subtleties and improvements in the jet substructure implementation and data-driven background estimates.

Pseudoscalar searches with dileptonic tops and jet substructure

The quest for new heavy states is a critical component of the LHC physics program. In this letter, we study the search for pseudoscalar bosons produced in association with a tt̄ pair. We consider the final state tt̄A→ tt̄bb̄ with di-leptonic top pair signature, and reconstruct the boosted A→ bb̄ candidate with jet substructure techniques, achieving a remarkable sensitivity over a broad range of pseudoscalar masses and Yukawa couplings. We apply this strategy to a Type-I TwoHiggs-Doublet Model, demonstrating its ability to probe a realistic, UV-complete extended Higgs sector. In particular, we find that the 13 TeV LHC with 300 fb−1 of data can constrain the region tanβ > 1.5 at 95% CL for a light pseudoscalar with mA = 50 GeV. Moreover, the whole mass range 20 GeV < mA < 210 GeV can be ruled out for tanβ ≤ 1. Finally, we show that it is also possible to directly probe the CP-structure of the heavy scalar, and hence to distinguish a CP-odd (A) from a CP-even (H) 2HDM resonance.

Higgs-Strahlung: Merging the NLO Drell-Yan and Loop-Induced 0+1 jet Multiplicities

We analyze the production of a Higgs boson in association with a Z boson at hadron colliders in the Standard Model and some simple extensions. We show how multijet merging algorithms at leading and next-to-leading order for the loop-induced gluon fusion and the Drell-Yan-like quark-induced processes, respectively, improve the descriptions for various differential distributions, in particular those that involve the production of additional jets. The phenomenological studies focus on two relevant channels of Higgs boson decays, namely H→invisible and H→bb¯. We find sizable and phenomenologically relevant corrections to the transverse momentum and invariant mass distributions for the Higgs boson candidate. Thanks to the large destructive interference for the top Yukawa terms, this process is very sensitive to the magnitude and sign of a possible nonstandard top-Higgs coupling. We analyze the impact of this anomalous interaction on distributions and estimate constraints from LHC Run II.

Constraining the strength andCPstructure of dark production at the LHC: The associated top-pair channel

We consider the production of dark matter in association with a pair of top quarks, mediated by a scalar or pseudoscalar particle in a generic Simplified Model. We demonstrate that the difference of azimuthal angle between the two leptons