We discuss models in which vectorlike quarks and a second Higgs doublet are simultaneously present and couple to the third generation of SM quarks. A general feature of these models is that cascade decays of vectorlike fermions into heavy Higgses (or vice versa, depending on their masses) dominate their respective branching ratios. The resulting collider signals involve a large multiplicity of $\textit{b}$-jets and offer formidable experimental challenges. We present a detailed and realistic analysis of the expected sensitivity of dedicated searches at ATLAS and CMS.

United States

Switzerland

Enrico Lunghi

Beni Pazar

Isolating new physics signatures of vectorlike quarks and heavy Higgses over multi $\textit{b}$-jet backgrounds

A correction to this paper has been published: https://doi.org/10.1007/JHEP11(2024)130

Germany

Tobias Huber

Tobias Hurth

Jack Jenkins

China

Qin Qin

Netherlands

K. Vos

Erratum to: Inclusive $$ \overline{B}\to {X}_s{\ell}^{+}{\ell}^{-} $$ at the LHC: theory predictions and new-physics reach

We examine nonrenormalizable Lorentz- and CPT-violating effective operators applied to the quark sector of the Standard Model. Using Drell-Yan events collected by the ATLAS and CMS Collaborations, several constraints are extracted from time-independent modifications of the cross section on the <italic>Z</italic>-boson pole. The sensitivity to time-dependent modifications is also estimated by simulating a sidereal-time analysis. Our results suggest a dedicated search can improve on constraints from deep inelastic scattering by up to three orders in magnitude.

Nathaniel Sherrill

Signals of nonrenormalizable Lorentz and CPT violation at the LHC

We use vector meson dominance to calculate non-perturbative contributions to the branching ratio of the rare decay   <math> <msup> <mi>K</mi> <mo>±</mo> </msup> <mo>→</mo> <msup> <mi>π</mi> <mo>±</mo> </msup> <mi>ν</mi> <mover> <mi>ν</mi> <mo>¯</mo> </mover> </math>  $$ {K}^{\pm}\to {\pi}^{\pm}\nu \overline{\nu} $$  stemming from matrix elements involving up-quark loops. The importance of this observable as well as of K 0 → π 0 l + l  −  and of the direct CP violation parameter   <math> <msubsup> <mi>ϵ</mi> <mi>K</mi> <mo>′</mo> </msubsup> </math>  $$ {\epsilon}_K^{\prime } $$  is then discussed in the context of a Unitarity Triangle sqtudy based on Kaon sector observables only.

CERN

Amarjit Soni

Light quark loops in   <math> <msup> <mi>K</mi> <mo>±</mo> </msup> <mo>→</mo> <msup> <mi>π</mi> <mo>±</mo> </msup> <mi>ν</mi> <mover> <mi>ν</mi> <mo>¯</mo> </mover> </math>  $$ {K}^{\pm}\to {\pi}^{\pm}\nu \overline{\nu} $$  from vector meson dominance and update on the Kaon Unitarity Triangle

We present theoretical predictions for observables in inclusive $$ \overline{B}\to {X}_s{\ell}^{+}{\ell}^{-} $$ suitable for measurements at hadron colliders through a sum-over-exclusive approach. At low $\textit{q}$ we calculate the branching ratio and three angular observables. At high $\textit{q}$ we provide the branching ratio and the ratio of the $$ \overline{B}\to {X}_s{\ell}^{+}{\ell}^{-} $$ rate with respect to the inclusive $$ \overline{B}\to {X}_u\ell \overline{\nu} $$ rate with the same phase-space cut. We compare our predictions to the $\textit{B}$ factory measurements and also to an extraction of the experimental rate through a sum-over-exclusive method using branching ratios of the exclusive $$ \overline{B}\to {K}^{\left(\ast \right)}{\mu}^{+}{\mu}^{-} $$ modes measured at LHCb. We find a consistent picture comparing Standard Model theory and experiment. As such, our analysis does not support a recent claim about a deficit in the inclusive branching ratio in the high-$\textit{q}$ region. Finally, we present current model-independent bounds on new physics and emphasize the potential of complementary analyses of $$ \overline{B}\to {X}_s{\ell}^{+}{\ell}^{-} $$ at Belle II and the LHC.

Inclusive $$ \overline{B}\to {X}_s{\ell}^{+}{\ell}^{-} $$ at the LHC: theory predictions and new-physics reach

A correction to this paper has been published: https://doi.org/10.1007/JHEP04(2021)228

Nathan Sherrill

Adam Szczepaniak

Brazil

Alexandre Vieira

Erratum to: Quark-sector Lorentz violation in Z-boson production

The hadronic mass spectrum of inclusive   <math> <mover> <mi>B</mi> <mo>¯</mo> </mover> <mo>→</mo> <msub> <mi>X</mi> <mi>s</mi> </msub> <msup> <mi>ℓ</mi> <mo>+</mo> </msup> <msup> <mi>ℓ</mi> <mo>−</mo> </msup> </math>  $$ \overline{B}\to {X}_s{\ell}^{+}{\ell}^{-} $$  is investigated at next to leading order in the heavy quark expansion. For mild cuts on the hadronic mass, the expansion, which applies when the cut is released, remains convergent. However, the cuts used at BaBar and Belle to reduce backgrounds from charged current semileptonic processes are too severe for a description in terms of matrix elements of local operators to apply. Strategies for interpolating between the two regions are discussed.

Inclusive   <math> <mover> <mi>B</mi> <mo>¯</mo> </mover> <mo>→</mo> <msub> <mi>X</mi> <mi>s</mi> </msub> <msup> <mi>ℓ</mi> <mo>+</mo> </msup> <msup> <mi>ℓ</mi> <mo>−</mo> </msup> </math>  $$ \overline{B}\to {X}_s{\ell}^{+}{\ell}^{-} $$  with a hadronic mass cut

Motivated by new physics models which lead to final states containing a high multiplicity of bottom and top quarks, we develop a tagging strategy to suppress reducible and non-reducible multi-jet backgrounds. The idea takes advantage of the properties of light parton showers and of the gluon fragmentation into heavy quarks to reject jets that do not originate from a bottom quark.

2b or not 2b: on the rejection of g →   <math> <mi>b</mi> <mover> <mi>b</mi> <mo>¯</mo> </mover> </math>  $$ b\overline{b} $$  jets

We demonstrate the potential of fully leptonic cascade decays of a heavy neutral Higgs boson through vectorlike leptons as a simultaneous probe for extended Higgs sectors and extra matter particles at the LHC. The processes we explore are unique in that their event topologies lead to di-boson-like leptonic final states with a lepton pair which does not reconstruct the mass of a gauge boson. By recasting existing   <math> <mn>2</mn> <mi>ℓ</mi> <mo>+</mo> <msubsup> <mi>E</mi> <mi>R</mi> <mtext>miss</mtext> </msubsup> </math>  $$ 2\ell +{E}_R^{\textrm{miss}} $$  and 3/4ℓ searches channels using run2 data from the LHC we obtain model independent bounds on the masses of heavy scalars and vectorlike leptons and use these results to explore future prospects at the HL-LHC. Our results can be directly applied to any kind of new physics scenarios sharing the final states and the event topology. For concreteness, we apply our results to a benchmark scenario: a two Higgs doublet model type-II augmented with vectorlike leptons. Remarkably, even with current data the sensitivity of our analysis shows a reach for masses of a heavy neutral Higgs and vectorlike leptons up to 2 TeV and 1.5 TeV, respectively. Even for low tan β ≳ 1, the analysis retains sensitivity to heavy Higgs masses slightly above 1 TeV. The future sensitivities at the HL-LHC extend the reach for heavy Higgses and new leptons to 2.7 TeV and 2 TeV, respectively.

Radovan Dermisek

South Korea

Junichiro Kawamura

Canada

Navin McGinnis

Seodong Shin

Leptonic cascade decays of a heavy Higgs boson through vectorlike leptons at the LHC

We study 4b + 2τ and 4b + 1τ signatures of heavy neutral and charged Higgs bosons originating from cascade decays of pair-produced new quarks. Decays of vectorlike quarks through heavy Higgses can easily dominate in the two Higgs doublet model of type-II, and the studied signatures are common to many possible decay chains. We design search strategies for these final states and discuss the mass ranges of heavy Higgs bosons and new quarks that can be explored at the Large Hadron Collider as functions of branching ratios in a model independent way. We further combine the results with a similar study focusing on decays which lead to a 6b final state and interpret the sensitivity to charged and neutral Higgs bosons and vectorlike quarks in the type-II two Higgs doublet model. We find that the LHC reach for their masses extends to well above 2 TeV in the case of an SU(2) doublet quark and to at least 1.8 TeV for a bottom-like SU(2) singlet quark in the whole range of tan β between 1 and 50.