Searcharxiv⌕ Search

arXiv subjects

Tania Robens

Publications and source records attributed to Tania Robens.

At least 19 recordsLinked to original sources
arXiv2026

Search for Light Scalars in the Two Real Singlet Model at the LHC

We investigate exotic scalar decays $h_2 \to h_1 h_1$ in the Two Real Singlet Model (TRSM), focusing on light CP-even scalars with $20 \le M_{1} \le 60$~GeV and $20 \le M_{2} \le 120$~GeV. Unlike previous studies focused on gluon--gluon fusion or vector-boson fusion production, we explore associated production with electroweak gauge bosons, $pp \to Vh_2$ {\sl($V = W,Z$)}, as a complementary and experimentally clean probe of light scalar cascades in the TRSM. The subsequent decay $h_1 \to b\bar{b}$ leads to final states containing four $b$-jets accompanied by a charged lepton and missing transverse energy. We evaluate the sensitivity of the $4b+\ell\nu_\ell$ channel at $\sqrt{s}=13.6$~\TeV for the LHC Run~3 and the HL-LHC. For an integrated luminosity of $300~\mathrm{fb}^{-1}$, the $W^+h_2$ channel provides the strongest sensitivity, reaching a significance of approximately $4\sigma$, while the $W^-h_2$ channel reaches approximately $3\sigma$. At the HL-LHC with $3000~\mathrm{fb}^{-1}$, the corresponding significances increase to approximately $12\sigma$ and $8\sigma$, respectively, highlighting the strong discovery potential of associated light-scalar production in the TRSM.

hep-ph↗
arXiv2026

TRSMScans

In this work, we propose a new scan tool that automatically calculates maximal cross section predictions for a new physics scenario with additional scalar states. While the tool is currently optimized for asymmetric production and decay processes in the form of p p -> h3 -> h1 h2, where hi denote CP even neutral scalars, in principle it can be extended to include any production and decay mode. As the code builds largely on the structure of the publicly available code ScannerS, it can in principle be extended to any other model contained within this tool. We here show first applications for a specific model, the Two-Real-Singlet Model (TRSM), and compare to publicly available results from the LHC collaborations from the previous runs. We also in detail discuss the structure of the code, including code installation, usage, as well as underlying algorithms.

hep-ph↗
arXiv2026

Search for Invisibly Decaying Light Scalars at the FCC-ee

We investigate the production of invisibly decaying light scalars in association with hadronically decaying $Z$ bosons at the Future Circular Collider-ee at a centre-of-mass energy $\sqrt{s}=240$ GeV. Several new physics models predict the existence of these low-mass scalar states, while the existing experimental constraints do not yet exclude these states. We study the low-mass scalar based on a simplified extension of the Standard Model, introducing an additional scalar singlet and a scalar dark matter candidate. The analysis is performed for a set of new scalars with mass in the range $(15, 120)$ GeV, by employing a selection-based strategy complemented with Multivariate Analysis techniques to discriminate the signal from background. The expected upper limits on the production cross-section times the branching fraction of the new scalars decaying invisibly are evaluated as a function of the scalar mass. We find that sensitivities of $\sim 10^{-2}$--$10^{-1}$~fb are achievable for scalar masses below the $Z$ boson mass, while sensitivities of $0.1$--$1$~fb are obtained in the mass range 80--120 \GeV. Depending on the mixing angle, novel scalars with masses up to 80 \GeV are within discovery reach.

hep-ph↗
arXiv2026

Kinematic Riffs and Interference Effects in Triple Higgs Production in the N2HDM

We investigate the complex kinematic structure involved in resonant production of three Higgs bosons at the Large Hadron Collider (LHC), within the rich scalar spectra of the Next-to-minimal Two Higgs Doublet Model (N2HDM), which features three CP-even neutral scalar degrees of freedom. Focussing on the resonant topologies, we analyse the invariant mass and transverse momentum distributions to disentangle the underlying production mechanisms. We demonstrate that interference effects and additional kinematically accessible decay channels can significantly alter kinematic observables, highlighting the limitations of simplified approximations and underscoring the importance of fully differential studies for probing extended Higgs sectors.

hep-ph↗
arXiv2026

Low mass scalars at $e^+e^-$ colliders

I briefly discuss the search for low mass scalars at Higgs factories as well as available models that render such scalars feasible, where I focus on new developments since the review presented in arXiv:2205.09687 (see also arXiv:2504.11969 for a recent update).

hep-ph↗
arXiv2026

Search for Light Scalars in the TRSM at the LHC

We study the production of Beyond the Standard Model light scalar states in association with a vector boson ($Vh_2$, with $V = W^\pm, Z$) at the LHC. We consider the scenario where the Standard Model scalar sector is extended by two real scalar singlets, where these additional scalars have mass $ M_i \leq M_{h_{125}}$. In this work, the scalar boson $h_2$ decays via $h_2 \to h_1 h_1 \to 4b$, while the associated vector boson decays either into a pair of oppositely charged leptons or into a single charged lepton and a neutrino. We analyze the signal using LHC detector parameterizations and evaluate its statistical significance at a center-of-mass energy of 13.6~TeV for integrated luminosities of 300~fb$^{-1}$ and 3000~fb$^{-1}$ corresponding to the LHC Run 3 and High Luminosity LHC, respectively. Our preliminary results indicate promising discovery prospects for this channel serving as a complementary probe of extended scalar sectors.\\ RBI-ThPhys-2026-04, COMETA-2026-04

hep-ph↗
arXiv2026

News from Extended Scalar Sectors

In this proceeding contribution, I give a short overview on selected topics regarding extended scalar sector phenomenology. After a short overview on extended scalar sectors with light scalars at Higgs factories, I concentrate on the Inert Doublet model and recent studies exploring its discovery potential at lepton colliders.

hep-ph↗
arXiv2026

Interference effects in new physics searches

Interference effects are an important consequence of a correct description in physics theories within and beyond the Standard Model (SM) of particle physics. However, many current theoretical descriptions as well as experimental searches neglect such effects, which can, among others, lead to an incorrect description of e.g. kinematical distributions, at least within the context of UV-complete models. In this review, I briefly discuss the current status and most common descriptions as well as existing studies of such effects, where I focus on models with extended scalar searches.

hep-ph↗
arXiv2025

Constraining the Inert Doublet Model at the LHC

In this work, we analyze experimental exclusion bounds that have been derived within a specific new physics realization, the two Higgs-doublet model with a pseudoscalar singlet (2HDMa), and their application to a different model, the Inert Doublet Model (IDM), that features the same final state. In this context, we discuss the sensitivity of the ATLAS search for the 2HDMa in final states with leptons and missing energy. We demonstrate that, with cuts optimized for a specific model topology, other new physics scenarios with larger rates might yet escape detection. We also give an update on constraints from vector boson fusion production of the Standard Model-like scalar and subsequent invisible decay from full Run 2 data on the parameter space of the IDM, with a special emphasis on the off-shell region, as well as a search that specifically concentrates on soft lepton final states.

hep-ph↗
arXiv2025

BSM: Extended Scalar Sectors

In particle physics the world is described by a function, the Lagrangian. Each of its sectors characterizes the interactions between the particles of the Standard Model (SM). The addition of hypothetical new particles is done by including new terms in the Lagrangian. The scalar or Higgs sector of the SM is built with only one scalar complex field and it is extended by including new spin zero fields. This can help to solve questions that cannot be answered by the SM alone, like introducing dark matter candidates or new sources of CP-violation required to explain the matter-antimatter asymmetry of the universe. The corresponding theories have to be probed experimentally. For the high energy region, the standard tools are collider experiments such as the Large Hadron Collider, or other possible future facilities. Dark matter experiments scrutinize the connection between the visible and the dark world.

hep-ph↗
arXiv2025

Extended scalar sectors from all angles (in 15 minutes)

In this proceedings contribution, I briefly summarize various aspects that are important in the discussions of new physics searches with novel scalar states, at current and future colliders. In particular, I give a brief glance on the status of two Higgs doublet models, and discuss multi-scalar production as well as interference effects in Di-Higgs searches. I also mention searches of new scalar final states at possible Higgs factories.

hep-ph↗
arXiv2025

Search for additional scalar bosons within the Inert Doublet Model in a final state with two leptons at the FCC-ee

We present a search for new scalar bosons predicted by the Inert Doublet Model at an $e^+e^-$ machine with centre-of-mass energies of 240 and 365 GeV. Within this model, four additional scalar bosons ($H,\, A,\, H^+$ and $H^-$) are predicted. Due to an additional symmetry, the lightest new scalar, here chosen to be $H$, is stable and provides an adequate dark matter candidate. The search for pair production of the new scalars is investigated in final states with two electrons or two muons, in the context of the future circular collider proposal, FCC-ee. Building on previous studies in the context of the CLIC proposal, this analysis extends the search to detector-level objects, using a parametric neural network to enhance the signal contributions over the Standard Model backgrounds, and sets projected exclusion and discovery contours in the $M_A-M_H$ vs. $M_H$ plane. With a total integrated luminosity of 10.8 (2.7) ab$^{-1}$ for $\sqrt{s}=240$ (365) GeV, the discovery reach for the model goes up to $m_H= 108$ (157) GeV for $M_A-M_H=15$ GeV. For exclusion, almost the entire phase-space available in the $M_A-M_H$ vs. $M_H$ plane is expected to be ruled out at 95\% CL, reaching up to $M_H=110$ (165) GeV.

hep-ph↗
arXiv2024

Probing the Inert Doublet Model via Vector-Boson Fusion at a Muon Collider

In this work, we explore the discovery potential of the Inert Doublet Model (IDM) via the vector boson fusion (VBF) channel at a muon collider with centre-of-mass energy of 10 TeV. The Inert Doublet Model is a two-Higgs-doublet model variant with an unbroken discrete $\mathbb{Z}_2$ symmetry, featuring new stable scalar particles that can serve as dark matter candidates. Current dark matter data constrain the phenomenologically viable parameter space of the IDM and render certain collider signatures elusive due to tiny couplings. However, VBF-type processes can still exhibit significant enhancements compared to the Standard Model, presenting a promising avenue to probe the IDM at a high-energy muon collider. We consider as our specific target process $\mu^+\mu^-\to \nu_\mu\bar{\nu}_\mu AA\to \nu_\mu\bar{\nu}_\mu jj \ell\ell HH$, where $H$ and $A$ are the lightest and second-lightest new scalars and $\ell$ can be electrons or muons. We perform both cut-based and machine-learning improved sensitivity analyses for such a signal, finding a population of promising benchmark scenarios. We additionally investigate the impact of the collider energy by comparing sensitivities to the target process at 3 TeV and 10 TeV. Our results provide a clear motivation for a muon collider design capable of reaching a 10 TeV centre-of-mass energy. We furthermore discuss constraints stemming from new-physics corrections to the Higgs to di-photon decay rate as well as the trilinear Higgs coupling in detail, using state-of-the-art higher-order calculations.

hep-ph↗
arXiv2024

Overview on low mass scalars at $e^+e^-$ facilities -- theory

I give a short summary of scenarios with new physics scalars that could be investigated at future $e^+e^-$ colliders. I concentrate on cases where at least one of the additional scalar has a mass below 125 GeV, and discuss models where this could be realized. In general, there are quite a few additional new physics scenarios and signatures that are still allowed by current constraints and should be investigated in more detail at future $e^+e^-$ machines. Most of the material presented here has already been discussed in arXiv:2307.15962, and I therefore try to focus on novel developments since then.

hep-ph↗
arXiv2024

Interference effects in resonant di-Higgs production at the LHC in the Higgs singlet extension

Interference effects are well founded from the quantum mechanical viewpoint and in principle cannot be ignored in realistic studies of New Physics scenarios. In this work, we investigate the size of interference effects between resonant and non-resonant contributions to di-Higgs production in the singlet extension of the Standard Model, where the additional heavy scalar provides a resonant channel. We find these interference contributions to have a non-negligible effect on the cross-sections and differential distributions. In order to allow for a computationally efficient treatment of these effects via reweighting, we introduce a new tool utilising a matrix-element reweighting method: HHReweighter. In addition to the broadly used di-Higgs invariant mass $m_{hh}$, we analyse the sensitivity to the interference terms for other kinematic variables, such as the Higgs boson transverse momentum, and find that these also can be sensitive to interference effects. Furthermore, we provide updates on the latest experimental and theoretical limits on the parameter space of the real singlet extension of the Standard Model Higgs sector.

hep-ph↗
arXiv2024

HHH Whitepaper

We here report on the progress of the HHH Workshop, that took place in Dubrovnik in July 2023. After the discovery of a particle that complies with the properties of the Higgs boson of the Standard Model, all Standard Model (SM) parameters are in principle determined. However, in order to verify or falsify the model, the full form of the potential has to be determined. This includes the measurement of the triple and quartic scalar couplings. We here report on ongoing progress of measurements for multi-scalar final states, with an emphasis on three SM-like scalar bosons at 125 GeV, but also mentioning other options. We discuss both experimental progress and challenges as well as theoretical studies and models that can enhance such rates with respect to the SM predictions

hep-ph↗
arXiv2024

Focus topics for the ECFA study on Higgs / Top / EW factories

In order to stimulate new engagement and trigger some concrete studies in areas where further work would be beneficial towards fully understanding the physics potential of an $e^+e^-$ Higgs / Top / Electroweak factory, we propose to define a set of focus topics. The general reasoning and the proposed topics are described in this document.

hep-ph↗