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LHC Higgs Working Group WG3 (BSM) -- Extended Higgs Sector subgroup meeting
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Europe/Zurich
Alexandra Carvalho Antunes De Oliveira
(Peking University (CN)),
Khawla Jaffel
(National Institute of Chemical Physics and Biophysics (EE)),
Lidija Zivkovic
(Institute of physics Belgrade (RS)),
Nikolaos Rompotis
(University of Liverpool (UK)),
Tania Robens
(IRB Zagreb),
Thomas Biekötter
(IFT Madrid)
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14:00
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14:20
An exploration of the NMSSM using deep learning to fit hints of new scalars 20m
In this talk we discuss a recent search over the parameter space of the Next-to-Minimal Supersymmetric Standard Model using deep learning techniques. The particular focus of this search is identifying parameter values that explain hints of excesses around 95 GeV and 650 GeV in Higgs studies, and a discrepancy in Electro-Weakino searches, as well as predicting mono-H and mono-Z signatures of dark matter. For this study we employ a recent scanning tool called DLScanner. This tool uses deep learning techniques to efficiently identify parameter regions that accommodate a number of constraints consistent with current observations as well as the mentioned scalars and Electro-Weakino. Furthermore, we present evidence of parameter values with promising possibilities for phenomenological studies
Speaker: Ramos Raymundo (Korea Inst. Advanced Study, Seoul) -
14:25
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14:45
The cS2HDM as a unified framework for dark matter and electroweak baryogenesis 20m
The discovery of the Higgs boson at the LHC confirms the Standard Model's (SM) mechanism for electroweak symmetry breaking, yet the SM fails to address key cosmological phenomena such as dark matter (DM) and the matter-antimatter asymmetry. Higgs-portal models with extended scalar sectors offer promising frameworks to bridge this gap. Among them, models incorporating a complex singlet scalar field can host pseudo-Nambu-Goldstone (pNG) DM, naturally suppressing direct-detection signals and making them ideal candidates for collider-based DM searches. However, minimal pNG DM models lack ingredients for electroweak baryogenesis. To overcome this, we look at the CP-violating singlet-extended two Higgs doublet model (cS2HDM) which contains both a pNG DM candidate and several sources of CP-violation and could serve as a benchmark for upcoming LHC searches
Speaker: Pedro Gabriel (Lisbon U., CFTC) -
14:50
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15:10
Deconstruction approach to di-Higgs production 20m
The effects of new physics in the process of pair production of Higgs bosons at the LHC can have multiple origins: modifications of SM couplings related to new physics at high scales, resonant propagation of new neutral particles, or non-resonant propagation of coloured particles in loops. All these effects often appear simultaneously and affect the kinematics of the process in non-trivial ways, through the interplay of threshold effects, resonant peaks, and interferences between all contributions. Extracting information about which new physics can determine the shape of kinematical distributions can thus be very challenging, even at the HL-LHC or future colliders. I will describe a model-indepedent framework to deconstruct any new signal contribution in a complete database of simulated samples which can be used to reconstruct any new physics contribution to di-Higgs through weighted sums and the recycling of samples, allowing to precisely assess the role of interferences and width effects, and offering a flexible tool to interpret future experimental data in a wide range of theoretical scenarios. I will describe the framework through its practical application in the case of new physics contributions from neutral scalars and squarks in the context of the NMSSM.
Speaker: Luca Panizzi (Universita' della Calabria) -
15:15
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15:35
The Importance of Interference Effects in Di-Higgs Analyses 20m
The conventional separation of di-Higgs searches into resonant and non-resonant categories has well-known limitations, as discussed in several LHC working group meetings. In this talk, I will motivate a unified treatment of resonant and non-resonant di-Higgs searches as a first step toward more comprehensive analyses of BSM scenarios. Specifically, I will argue that including only the SM-like interference term, while neglecting other interference contributions, provides a well-justified and effective first approximation. I will show that this approach already leads to significant improvements in the applicability of di-Higgs results to UV-complete BSM frameworks. Finally, I will discuss the implementation of existing resonant and non-resonant experimental bounds within the public collider-phenomenology tool HiggsTools, and highlight that, given the powerful potential of di-Higgs searches to probe the BSM parameter space, improving their theoretical and experimental treatment is not only desirable but necessary.
Speaker: Kateryna Radchenko Serdula (DESY) -
16:00
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16:15
Break 15m
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16:20
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16:40
Explaining 95 and 650 GeV Anomalies in the 2-Higgs Doublet Model Type-I 20m
We show how the 2-Higgs Doublet Model (2HDM) Type-I can explain some excesses recently seen at the Large Hadron Collider (LHC) in γγ and τ+τ− final states in turn matching Large Electron Positron (LEP) data in b¯b signatures, all anomalies residing over the 90-100 GeV or so region. The explanation to such anomalous data is found in the aforementioned scenario when in inverted mass hierarchy, in two configurations: i) when the lightest CP-even Higgs state is alone capable of reproducing the excesses; ii) when a combination of such a state and the CP-odd Higgs boson is able to do so. To test further this scenario, we present some Benchmark Points (BPs) of it amenable to phenomenological investigation. [1].
We also propose an interpretation of a rather significant 650 GeV excess emerged at the Large Hadron Collider (LHC) from CMS Collaboration data in the γγb¯b final state, accompanied by further clusters at 125(90-100) GeV in the γγ(b¯b) system, within the 2-Higgs Doublet Model Type-I (2HDM-I) in presence of a softly broken Z2 symmetry. The underlying process that we probe is gg-initiated production of a CP-odd (or pseudoscalar) Higgs Boson A, with mass around 650 GeV, decaying into the Standard Model (SM) like Higgs state H (decaying into γγ) and a Z boson (decaying into b¯b). We configure this theoretical framework so as to also have in the spectrum a light CP-even (or scalar) Higgs state h with mass around 95 GeV, which is included for the purpose of simultaneously explaining additional data anomalies seen in the b¯b, γγ and τ +τ − final states while searching for light Higgs states at the Large Electron-Positron (LEP) collider (the first one) and LHC (the last two). By accounting for both experimental and theoretical constraints, our results show that the 2HDM-I can explain all aforementioned anomalies at a significance level of 2.5σ. [2]
[1] Akshat Khanna, Stefano Moretti, and Agnivo Sarkar. Explaining 95 (or so) GeV Anomalies in the 2-Higgs Doublet Model Type-I. 9 2024.
[2] Akshat Khanna, Stefano Moretti, and Agnivo Sarkar. Explaining 650 GeV and 95 GeV Anomalies in the 2-Higgs Doublet Model Type-I. 9 2025.Speaker: Akshat Khanna (Indian Institute of Technology Gandhinagar) -
16:45
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17:05
Impact of Interference Effects on Higgs-boson Searches in the Di-top Final State at the LHC 20m
The di-top final state is an important search channel for additional Higgs bosons at the LHC. In this channel, large signal--background interference contributions can strongly distort a resonance peak as it would be expected from a pure signal contribution. Moreover, signal--signal interference effects can have a significant impact if more than one additional scalar particle is present. In this work, we perform a comprehensive model-independent analysis of the various interference contributions considering two additional heavy scalars that can mix with each other. We point out the importance of taking into account loop-level mixing between the scalars. A proper treatment of these mixing effects, which has not been previously carried out for the di-top final state, introduces additional relative phases between different parts of the amplitudes entering the interference contributions which we find to have a strong impact on the di-top invariant mass distribution. We study the interference effects both in an idealistic setting as well as taking into account experimental limitations using Monte-Carlo simulations. We demonstrate that the emerging experimental signatures can be unexpected and difficult to interpret. In particular, we point out that an experimental signature manifesting itself as an excess near the tt-bar threshold may actually be caused by new scalar particles with much higher masses. We comment in this context on the recent excess that has been observed by the CMS collaboration near the tt-bar threshold in their searches in the di-top final state. We also highlight how multi-top final-state searches, such as the four-top channel, can provide important complementary information and help pinpoint the underlying new physics
scenario.
Primarily based on: arXiv:2503.02705 (https://doi.org/10.1007/JHEP05(2025)098)
Speaker: Kumar (DESY)
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