<p>We investigate the phenomenology of the charged Higgs boson at the International Linear Collider (ILC) within the framework of the type-X Two-Higgs Doublet Model, where a light charged Higgs boson, with a mass around 200 GeV or even smaller than top quark mass, is still being consistent with flavor physics data as well as with collider experimental data. In the theoretically and experimentally allowed parameter space, the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">→</mo><msup><mi>H</mi><mo>±</mo></msup><msup><mi>W</mi><mo>∓</mo></msup><mi>S</mi></math> (with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>S</mi><mo>=</mo><mi>H</mi></mrow></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>A</mi></mrow></math>) production processes can yield signatures with event rates larger than those from <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">→</mo><msup><mi>H</mi><mo>+</mo></msup><msup><mi>H</mi><mo>−</mo></msup></math> and offer sensitivity to the Higgs mixing parameter <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>sin</mi><mo stretchy="false">(</mo><mi>β</mi><mo>−</mo><mi>α</mi><mo stretchy="false">)</mo></math>. We consider the bosonic <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>H</mi><mo>±</mo></msup><mo stretchy="false">→</mo><msup><mi>W</mi><mo>±</mo></msup><mi>S</mi></math> decays, where the neutral scalar <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi></math> further decays into a pair of tau leptons. We show, through a detector-level Monte Carlo analysis, that the resulting <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">[</mo><mi>τ</mi><mi>τ</mi><mo stretchy="false">]</mo><mo stretchy="false">[</mo><mi>τ</mi><mi>τ</mi><mo stretchy="false">]</mo><mi>W</mi><mi>W</mi></math> final state could be seen at the ILC with at least 500 GeV center-of-mass energy and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>500</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math> of luminosity.</p>

Morocco

Brahim Ait Ouazghour

Taiwan

Abdesslam Arhrib

South Korea

Kingman Cheung

Es-said Ghourmin

Mohamed Krab

Larbi Rahili

Searching for charged Higgs bosons via <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">→</mo><msup><mi>H</mi><mo>±</mo></msup><msup><mi>W</mi><mo>∓</mo></msup><mi>S</mi></math> at the ILC

Recent reports from the Large Hadron Collider indicate two excesses: one in the lighter Higgs mass region around 95 GeV, and another in the rare <italic>Z&#947;</italic> final state of the Standard Model (SM) 125 GeV Higgs decay. These anomalies are analyzed within the minimal gauged two-Higgs-doublet model (G2HDM). A viable parameter space in G2HDM is identified that can account for both excesses. Within the viable parameter space, we find a strong correlation between the signal strengths of the SM 125 GeV Higgs decays into <italic>&#947;&#947;</italic> and <italic>Z&#947;</italic> modes. However, this correlation does not extend to the lighter 95 GeV Higgs.

Vietnam

Khiem Hong Phan

China

Van Que Tran

Tzu-Chiang Yuan

When the Standard Model Higgs meets its lighter 95 GeV twin

Our goal is to investigate the charged Higgs phenomenology in the framework of 2HDM at the upcoming <math><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></math> and muon colliders. We are primarily concerned with the associated production processes with a fermion pair: <math><msup><mo>ℓ</mo><mo>+</mo></msup><msup><mo>ℓ</mo><mo>−</mo></msup><mo>→</mo><msup><mi>τ</mi><mo>+</mo></msup><msub><mi>ν</mi><mi>τ</mi></msub><msup><mi>H</mi><mo>−</mo></msup></math> and <math><msup><mo>ℓ</mo><mo>+</mo></msup><msup><mo>ℓ</mo><mo>−</mo></msup><mo>→</mo><mi>t</mi><mover><mi>b</mi><mo>¯</mo></mover><msup><mi>H</mi><mo>−</mo></msup></math>, as well as with the W boson and a neutral Higgs boson: <math><msup><mo>ℓ</mo><mo>+</mo></msup><msup><mo>ℓ</mo><mo>−</mo></msup><mo>→</mo><msup><mi>W</mi><mo>±</mo></msup><msup><mi>H</mi><mo>∓</mo></msup><mi>S</mi></math> (<math><mi>S</mi><mo>=</mo><mi>h</mi></math>, <math><mrow><mi>H</mi></mrow></math>, <math><mrow><mi>A</mi></mrow></math>) and <math><msup><mo>ℓ</mo><mo>+</mo></msup><msup><mo>ℓ</mo><mo>−</mo></msup><mo>→</mo><msup><mi>W</mi><mo>±</mo></msup><msup><mi>H</mi><mo>∓</mo></msup><mi>Z</mi></math>. We first update the results for <math><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo>→</mo><mo>{</mo><msup><mi>τ</mi><mo>+</mo></msup><msub><mi>ν</mi><mi>τ</mi></msub><msup><mi>H</mi><mo>−</mo></msup><mo>,</mo><mi>t</mi><mover><mi>b</mi><mo>¯</mo></mover><msup><mi>H</mi><mo>−</mo></msup><mo>}</mo></math> and then discuss our findings for <math><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo>→</mo><mo>{</mo><msup><mi>W</mi><mo>±</mo></msup><msup><mi>H</mi><mo>∓</mo></msup><mi>S</mi><mo>}</mo></math> for various center-of-mass energies 500 GeV, 1 TeV, 1.5 TeV, and 3 TeV. In the case of muon collider, we show that the new s-channel and t-channel diagrams can increase the cross sections by virtue of their Yukawa couplings. We systematically compare our results for the muon collider with those obtained at the International Linear and Compact Linear colliders. We select benchmark points and conduct signal-background analyses, incorporating detector simulations. For a 3 TeV muon collider, our results show an exclusion region at the <math><mrow><mn>2</mn><mi>σ</mi></mrow></math> level and a discovery region at the <math><mrow><mn>5</mn><mi>σ</mi></mrow></math> level.

Associated charged Higgs boson production within the 2HDM: <math><msup><mi>e</mi><mo>−</mo></msup><msup><mi>e</mi><mo>+</mo></msup></math> versus <math><msup><mi>μ</mi><mo>−</mo></msup><msup><mi>μ</mi><mo>+</mo></msup></math> colliders

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.

Hamza Abouabid

United States

Hannah Arnold

Germany

Duarte Azevedo

Croatia

Vuko Brigljevic

United Kingdom

Maggie Chen

Daniel Diaz

Javier Duarte

Netherlands

Tristan Pree

Jaouad Falaki

Dinko Ferencek

Portugal

Pedro. Ferreira

France

Benjamin Fuks

India

Japan

Sanmay Ganguly

Osama Karkout

Marina Kolosova

Jacobo Konigsberg

Greg Landsberg

Canada

Bingxuan Liu

CERN

Switzerland

Brian Moser

Margarete Mühlleitner

Andreas Papaefstathiou

Sweden

Roman Pasechnik

Tania Robens

Rui Santos

Brian Sheldon

Gregory Soyez

Marko Stamenkovic

Panagiotis Stylianou

Tatjana Susa

Gilberto Tetlalmatzi-Xolocotzi

Georg Weiglein

Giulia Zanderighi

Rui Zhang

HHH whitepaper

We investigate how the Next-Two-Higgs Doublet Model extension (N2HDM) should look if we are to address the naturalness problem using dimensional regularization. In such a model, new Higgs states are predicted, namely: three CP-even  $$h_{1,2,3}$$  <math> <msub> <mi>h</mi> <mrow> <mn>1</mn> <mo>,</mo> <mn>2</mn> <mo>,</mo> <mn>3</mn> </mrow> </msub> </math>  , one CP-odd A, and a pair of charged Higgs boson  $$H^\pm $$  <math> <msup> <mi>H</mi> <mo>±</mo> </msup> </math>  . Our calculations of the overall quadratic divergences have been performed with full consistency with the latest data from the Large Hadron Collider (LHC) concerning the observed 125 GeV Higgs boson, alongside precision electroweak data tests and lower mass limits on charged Higgs boson. It is shown that the quadratically divergent quantum corrections  $$\delta _i$$  <math> <msub> <mi>δ</mi> <mi>i</mi> </msub> </math>   (i=1,2,3) for the three CP-even Higgs bosons are controllably small, though hidden fine-tuning might still be required. This reveals a significant impact on the model parameter space, Higgs spectrum mass and notably the singlet-doublet admixture.

Rachid Benbrik

Souad Semlali

Bassim Taki

Echoes of Veltman criteria on the next-two-Higgs-doublet model

In this study, we aim to see how much the actual measurement of the Z+photon and di-photon signal strength,  $$\mu _{\gamma \gamma }$$  <math> <msub> <mi>μ</mi> <mrow> <mi>γ</mi> <mi>γ</mi> </mrow> </msub> </math>   and  $$\mu _{\gamma Z}$$  <math> <msub> <mi>μ</mi> <mrow> <mi>γ</mi> <mi>Z</mi> </mrow> </msub> </math>  , could influence the allowed parameter space of the Inert Doublet Model (IDM), and to what extent such measurement can be aligned with the latest bound from XenonNT experiment on the spin-independent dark-matter-nucleon scattering cross-section. Also, by considering the new embedded scalars in the IDM (i.e., S, A and  $$H^\pm $$  <math> <msup> <mi>H</mi> <mo>±</mo> </msup> </math>  ), a wide investigation of the one-loop radiative corrections to the trilinear Higgs coupling hhh has been made in the light of the previous measurements.

Ayoub Hmissou

Revisiting inert doublet model parameters

We study the phenomenology of the charged Higgs boson at future muon colliders. We investigate the pair production <math><msup><mi>μ</mi><mo>+</mo></msup><msup><mi>μ</mi><mo>−</mo></msup><mo>→</mo><msup><mi>H</mi><mo>+</mo></msup><msup><mi>H</mi><mo>−</mo></msup></math>, the single production <math><msup><mi>μ</mi><mo>+</mo></msup><msup><mi>μ</mi><mo>−</mo></msup><mo>→</mo><msup><mi>W</mi><mo>±</mo></msup><msup><mi>H</mi><mo>∓</mo></msup></math>, as well as the vector boson fusion (VBF) <math><mo>{</mo><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo>,</mo><msup><mi>μ</mi><mo>+</mo></msup><msup><mi>μ</mi><mo>−</mo></msup><mo>}</mo><mo>→</mo><mi>ν</mi><mover><mi>ν</mi><mo>¯</mo></mover><msup><mi>H</mi><mo>+</mo></msup><msup><mi>H</mi><mo>−</mo></msup></math>. We show that the neutral Higgs exchange diagrams in the muon collider case can lead to a significant boost in the cross sections through their Yukawa couplings. Our results for the muon collider are systematically compared to the corresponding ones at <math><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></math> machines. It is demonstrated that the VBF <math><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo>→</mo><mi>ν</mi><mover><mi>ν</mi><mo>¯</mo></mover><msup><mi>H</mi><mo>+</mo></msup><msup><mi>H</mi><mo>−</mo></msup></math> can compete with the mentioned <math><mn>2</mn><mo>→</mo><mn>2</mn></math> processes. We select benchmark points and perform signal-background analyses, taking into account detector simulations. We demonstrate the discovery region at <math><mn>5</mn><mi>σ</mi></math> and the excluded region at <math><mn>2</mn><mi>σ</mi></math> levels at a 3 TeV muon collider.

Comparison between <math><msup><mi>μ</mi><mo>−</mo></msup><msup><mi>μ</mi><mo>+</mo></msup></math> and <math><msup><mi>e</mi><mo>−</mo></msup><msup><mi>e</mi><mo>+</mo></msup></math> colliders for charged Higgs production in the 2HDM

We compute the full one-loop radiative corrections for charged scalar pair production <math><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo>→</mo><msup><mi>H</mi><mo>+</mo></msup><msup><mi>H</mi><mo>−</mo></msup></math> in the inert doublet model. The on-shell renormalization scheme has been used. We take into account both the weak contributions as well as the soft and hard QED corrections. We compute both the real emission and the one-loop virtual corrections using the Feynman diagrammatic method. The resummed cross section is introduced to cure the Coulomb singularity which occurs in the QED corrections. We have analyzed the parameter space of the inert doublet model in three scenarios after taking into account theoretical constraints, the collider experimental bounds, and dark matter search bounds as well. It is found that the weak interaction dominates the radiative corrections, and its size is determined by the triple Higgs coupling <math><msub><mi>λ</mi><mrow><msup><mi>h</mi><mn>0</mn></msup><msup><mi>H</mi><mo>+</mo></msup><msup><mi>H</mi><mo>−</mo></msup></mrow></msub></math>, which is further connected to the mass of the charged scalar. In the scenario where all the constraints are taken into account, we find that for <math><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>250</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> and <math><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>500</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>, the weak corrections are around <math><mo>−</mo><mn>6</mn><mo>%</mo><mo>∼</mo><mo>−</mo><mn>5</mn><mo>%</mo></math> and <math><mo>−</mo><mn>10</mn><mo>%</mo><mo>∼</mo><mo>−</mo><mn>3</mn><mo>%</mo></math>, respectively. While for <math><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>1000</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>, the weak corrections can reach <math><mo>−</mo><mn>15</mn><mo>%</mo><mo>∼</mo><mo>+</mo><mn>25</mn><mo>%</mo></math>. The new feature is that the weak corrections can be positive near the threshold when the charged scalar is heavier than 470 GeV. Six benchmark points for future collider searches have been proposed.

Jaouad El Falaki

Bin Gong

Wenhai Xie

Qi-Shu Yan

Full one-loop radiative corrections to <math><mrow><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup><mo>→</mo><msup><mrow><mi>H</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>H</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math> in the inert doublet model

We present a comprehensive study on Higgs pair production in various archetypical extended Higgs sectors such as the real and the complex 2-Higgs-Doublet Model, the 2-Higgs-Doublet Model augmented by a real singlet field and the Next-to-Minimal Supersymmetric extension of the Standard Model. We take into account all relevant theoretical and experimental constraints, in particular the experimental limits on non-resonant and resonant Higgs pair production. We present the allowed cross sections for Standard Model (SM)-like Higgs pair production and the ranges of the SM-like Yukawa and trilinear Higgs self-coupling that are still compatible with the applied constraints. Furthermore, we give results for the pair production of a SM-like with a non-SM-like Higgs boson and for the production of a pair of non-SM-like Higgs bosons. We find that di-Higgs production in the models under investigation can exceed the SM rate substantially, not only in the non-resonance region but also due to resonant enhancement. We give several benchmarks with interesting features such as large cross sections, the possibility to test CP violation, Higgs-to-Higgs cascade decays or di-Higgs production beating single Higgs production. In all of our benchmark points, the next-to-leading order QCD corrections are included in the large top-mass limit. For these points, we found that, depending on the model and the Higgs pair final state, the corrections increase the leading order cross section by a factor of 1.79 to 2.24. We also discuss the relation between the description of Higgs pair production in an effective field theory approach and in the specific models investigated here.

Pedro Ferreira

Benchmarking di-Higgs production in various extended Higgs sector models

We compute the full one-loop radiative corrections (including both weak and QED corrections) for two processes e + e  −  → Zh 0 , H 0 A 0 in the Inert Higgs Doublet model (IHDM). Up to O(α  w ) and O(α em) order, we use FeynArts/FormCalc to compute the one-loop virtual corrections and Feynman Diagram Calculation (FDC) to evaluate the real emission, respectively. Being equipped with these computing tools, we investigate radiative corrections of new physics for five scenarios with three typical collision energies of future electron-positron colliders: 250 GeV, 500 GeV, and 1000 GeV. By scanning the parameter space of IHDM, we identify the allowed regions which are consistent with constraints and bounds, from both theoretical and experimental sides. We find that the radiative corrections of the IHDM to e + e  −  → Zh 0 can be sizeable and are within the detection potentials of future Higgs factories. We also find that the new physics of IHDM could also be directly detected by observing the process e + e  −  → H 0 A 0 which could have large enough production rate. We propose six benchmark points and examine their salient features which can serve as physics targets for future electron-positron colliders, such as CEPC/CLIC/FCC-ee/ILC as well as for LHC.

One-loop radiative corrections to e+e −  → Zh0 /H0A0 in the Inert Higgs Doublet Model