We suggest an explanation for and explore the consequences of the excess around 95 GeV in the di-photon and di-tau invariant mass distributions recently reported by the CMS collaboration at the Large Hadron Collider (LHC), together with the discrepancy that has long been observed at the Large Electron-Positron (LEP) collider in the $$ b\overline{b} $$ b b ¯ invariant mass. Interestingly, the most recent findings announced by the ATLAS collaboration do not contradict, or even support, these intriguing observations. Their search in the di-photon final state similarly reveals an excess of events within the same mass range, albeit with a bit lower significance, thereby corroborating and somewhat reinforcing the observations made by CMS. We demonstrate that the lightest CP-even Higgs boson in the general 2-Higgs Doublet Model (2HDM) Type-III can explain simultaneously the observed excesses at approximately 1.3 σ C.L. while satisfying up-to-date theoretical and experimental constraints. Moreover, the 2HDM Type-III predicts an excess in the $$ pp\to t\overline{t}{H}_{\textrm{SM}} $$ pp → t t ¯ H SM production channel of the 125 GeV Higgs boson, H _SM. This effect is caused by a up to 12% enhancement of the H _SM tt Yukawa coupling in comparison to that predicted by the Standard Model. Such an effect can be tested at the High Luminosity LHC (HL-LHC), which can either discover or exclude the scenario we suggest. This unique characteristic of the 2HDM Type-III makes this scenario with the 95 GeV resonance very attractive for further theoretical and experimental investigations at the (HL-)LHC and future colliders.

We study the phenomenology of charged Higgs bosons ($H^{\pm }$) and vectorlike quarks (VLQs), denoted as $T$, the latter possessing a charge identical to the top quark one, within the framework of the two-Higgs-doublet model type II (2HDM-II). Upon examining two scenarios, one featuring a singlet ($T$) [$2\mathrm{HDM}\text{−}\mathrm{II}+(T)$] and another a doublet $(TB)$ [$2\mathrm{HDM}\text{−}\mathrm{II}+(TB)$], we discover that the presence of VLQs has a significant effect on the (pseudo)scalar sector of the 2HDM-II. In particular, this leads to a reduction in the strict constraint on the mass of the charged Higgs boson, which is imposed by $B$-physics observables, specifically $B\to X_s\gamma$. The observed reduction stems from modifications in the charged Higgs couplings to the Standard Model top and bottom quarks. Notably, the degree of this reduction varies distinctly between the singlet 2HDM+($T$) and doublet $2\mathrm{HDM}+(TB)$ scenarios. Additionally, our investigation extends to constraints imposed by the oblique parameters $S$ and $T$ on the VLQ mixing angles. Furthermore, to facilitate efficient exploration of the “$2\mathrm{HDM}\text{−}\mathrm{II}+\mathrm{VLQ}$” parameter space, we present results on pair production of VLQs $T$ ($pp\to T\overline{T}$), followed by $T\to H^{\pm }b$ and $H^{\pm }\to tb$ decays, yielding a distinctive $2t4b$ final state. This investigation thus provides valuable insights guiding the search for extended Higgs and quark sectors at the Large Hadron Collider (LHC) at CERN.

In this work, we present a comprehensive review of the most up-to-date exclusion limits on Vector-Like Quarks (VLQs) derived from ATLAS and CMS data at the Large Hadron Collider (LHC). Our analysis encompasses both pair and single production modes, systematically comparing results from the two collaborations to identify and employ the most stringent bounds at each mass point. We evaluate the excluded parameter space for VLQs under singlet, doublet, and triplet representations. For top-like VLQs (T), the exclusion limits rule out masses up to 1.49 TeV in singlet scenarios, while single production constrains the mixing parameter κ to values below 0.26 at m _T ~ 1.5 TeV and up to 0.42 for m _T ~ 2 TeV. For bottom-like VLQs (B), the strongest exclusion limits from pair production exclude masses up to 1.52 TeV in doublet configurations, with single production constraining κ values between 0.2 and 0.7 depending on the mass. For exotic VLQs, such as X and Y, pair production excludes masses up to 1.46 TeV and 1.7 TeV, respectively. The constraints on κ from these analyses become increasingly restrictive at higher masses, reflecting the enhanced sensitivity of single production channels in this regime. For X, κ is constrained below 0.16 for masses between 0.8 and 1.6 TeV and further tightens to κ < 0.2 as the mass approaches 1.8 TeV. Similarly, for Y, κ values are constrained below 0.26 around m _Y ~ 1.7 TeV, with exclusions gradually relaxing at higher masses. These exclusion regions, derived from the most stringent LHC search results, offer a unified and up-to-date perspective on VLQ phenomenology. The results were computed using VLQBounds, a new Python-based tool specifically developed for this purpose.

We propose an explanation for the observed excesses around 95 GeV in the diphoton and ditau invariant mass distributions, as reported by the CMS collaboration at the Large Hadron Collider. These findings are complemented by a long-standing discrepancy in the b b ¯ invariant mass at the Large Electron-Positron Collider. Additionally, the ATLAS collaboration has reported a corroborative excess in the diphoton final state within the same mass range, albeit with slightly lower significance. Our approach involves the superposition of C P -even and C P -odd Higgs bosons within the type-III two-Higgs doublet model to simultaneously explain these excesses at 1 σ confidence level, while remaining consistent with current theoretical and experimental constraints. Published by the American Physical Society 2024

A comprehensive extension of the ordinary 2-Higgs Doublet Model (2HDM), supplemented by vector-like quarks (VLQs), in the “alignment limit” is presented. In such a scenario, we study the possibility that large hadron collider (LHC) searches for VLQs can profile their nature too, i.e., whether they belong to a singlet, doublet, or triplet representation. To achieve this, we exploit both standard model (SM) decays of VLQs with top-(anti)quark electromagnetic (EM) charge (T), i.e., into b, t quarks and $$W^\pm , Z,h$$ W ± , Z , h bosons (which turn out to be suppressed and hence T states can escape existing limits) as well as their exotic decays, i.e., into b, t (and possibly B) quarks and $$H^\pm , H, A$$ H ± , H , A bosons. We show that quite specific decay patterns emerge in the different VLQ representations so that, depending upon which T signals are accessed at the LHC, one may be able to ascertain the underlying beyond standard model (BSM) structure, especially if mass knowledge of the new fermionic and bosonic sectors can be inferred from (other) data.

The CDF collaboration has released a new measurement of the W boson mass using their complete data set with 8.8 fb⁻¹ in p p ¯ collisions. This result deviates from the Standard Model prediction by around 7σ. We explain how the two Higgs doublet model (2HDM) with vector-like quarks (VLQs) is affected by the recently discovered W boson mass. In our study, we include both theoretical constraints such as perturbative unitarity and vacuum stability as well as a number of experimental constraints. We also look into how the effective mixing angle, measured by the SLD collaboration in addition to the CDF W-boson mass, is used to determine the S and T parameters. In the alignment limit, we investigate the case where the lighter CP-even neutral Higgs boson of the 2HDM is the one found at the LHC and demonstrate how the parameter space of the 2HDM type II in the presence of VLQs is constrained. It is found that in most cases, there is a cancellation between the 2HDM and VLQs contributions, which enlarges the parameter space of both models.