<p>We analyze the excesses at 95 GeV in the light Higgs-boson searches in the diphoton decay channel reported by CMS and ATLAS, which combined are at the level of three standard deviations and are compatible with the excess in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover></math> final state observed at Large Electron-Positron Collider, together with an excess in the diphoton channel at around 152 GeV reported based on a sideband analysis. We demonstrate that these excesses can be well described in a minimally extended Georgi-Machacek (meGM) model. This is enabled by four key features of the meGM model: (1) a natural prediction for scalar boson masses of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>≲</mo><mn>200</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> arising from the condition to describe both the Higgs boson signal at 125 GeV and the excesses at 95 GeV, (2) the prediction for a doubly charged Higgs boson that can potentially enhance the diphoton decay rates, (3) asymmetric <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>W</mi><mi>W</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi><mi>Z</mi></math> couplings to neutral scalar bosons that are induced by mild custodial symmetry breaking, and (4) the approximate preservation of the electroweak <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ρ</mi></math> parameter to be 1 at tree level. We show in our numerical analysis that the meGM model naturally improves the fit to the LHC data around 152 GeV when describing the excesses at 95 GeV. At the same time, the model also predicts additional light <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math>-odd and charged scalar bosons that can be potentially probed in future experiments, which motivates dedicated searches in the upcoming LHC runs. We also present the results of sensitivity studies for the 95 and 125 GeV Higgs-boson couplings at the HL-LHC and future <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></math> colliders, which demonstrate very interesting prospects for probing the meGM model at future colliders.</p>

United States

Ting-Kuo Chen

China

Cheng-Wei Chiang

Spain

Sven Heinemeyer

Germany

Georg Weiglein

Interpretation of LHC excesses at 95 GeV and 152 GeV in an extended Georgi-Machacek model

We investigate di-Higgs production at the (HL-)LHC and possible high-energy future $$e^+e^-$$ colliders within the real Higgs singlet extension of the Standard Model (SM), the RxSM. This model has two CP-even Higgs bosons, $\textit{h}$ and $\textit{H}$, for which we assume $$m_h\sim 125 \;\text {GeV} < m_H$$ . We analyse the effect of one-loop corrections to the two trilinear scalar couplings relevant for di-Higgs production, $$\lambda _{hhh}$$ and $$\lambda _{hhH}$$ , by performing an extensive parameter scan within the RxSM. We find that the one-loop corrections have a strong impact on the total production cross-sections, as well as on the differential cross-sections with respect to the invariant di-Higgs mass, $$m_{hh}$$ . We evaluate the sensitivity of the HL-LHC and a high-energy $$e^+e^-$$ collider with $$\sqrt{s} = 1 \;\text {TeV} $$ , the ILC1000, to probe BSM physics effects in these processes. We demonstrate that the RxSM can be distinguished from the SM for large parts of the sampled parameter space. The resonant $\textit{H}$ structure in the $$m_{hh}$$ distribution, on the other hand, can be observed only if the corresponding couplings, in particular $$\lambda _{hhH}$$ , are sufficiently large. Here the ILC1000 yields a substantially better sensitivity than the HL-LHC.

Johannes Braathen

Andrea Parra Arnay

Alain Verduras Schaeidt

Impact of one-loop corrections to trilinear scalar couplings on di-Higgs production in the RxSM

We present an analysis of the sensitivity of current and future LHC searches for new spin-0 particles in top–anti-top-quark $$ \left(t\overline{t}\right) $$ final states, focusing on generic axion-like particles (ALPs) that are coupled to top quarks and gluons. As a first step, we derive new limits on the effective ALP Lagrangian in terms of the Wilson coefficients and $$ {c}_{\overset{\sim }{G}} $$ based on the results of the CMS search using 35 9 fb 1 of data, collected at $$ \sqrt{s} $$ = 13 TeV. We then investigate how the production of an ALP with generic couplings to gluons and top quarks can be distinguished from the production of a pseudoscalar which couples to gluons exclusively via a top-quark loop. To this end, we make use of the invariant $$ t\overline{t} $$ mass distribution and angular correlations that are sensitive to the $$ t\overline{t} $$ spin correlation. Using a mass of 400 GeV as an example, we find that already the data collected during Run 2 and Run 3 of the LHC provides an interesting sensitivity to the underlying nature of a possible new particle. We also analyze the prospects for data anticipated to be collected during the high-luminosity phase of the LHC. Finally, we compare the limits obtained from the $$ t\overline{t} $$ searches to existing experimental bounds from LHC searches for narrow di-photon resonances, from measurements of the production of four top quarks, and from global analyses of ALP–SMEFT interference effects.

Afiq Anuar

Anke Biekötter

Thomas Biekötter

Alexander Grohsjean

Laurids Jeppe

Christian Schwanenberger

ALP-ine quests at the LHC: hunting axion-like particles via peaks and dips in

The quest for supersymmetric (SUSY) particles is among the main search channels currently pursued at the LHC. Particularly, electroweak (EW) particles with masses as low as a few hundred GeV are still viable. Recent searches for the “golden channel”,  $$pp \rightarrow \tilde{\chi }_{2}^0 \tilde{\chi }_{1}^\pm \rightarrow \tilde{\chi }_{1}^0 Z^{(*)} \, \tilde{\chi }_{1}^0 W^{\pm (*)}$$  <math> <mrow> <mi>p</mi> <mi>p</mi> <mo>→</mo> <msubsup> <mover> <mi>χ</mi> <mo>~</mo> </mover> <mrow> <mn>2</mn> </mrow> <mn>0</mn> </msubsup> <msubsup> <mover> <mi>χ</mi> <mo>~</mo> </mover> <mrow> <mn>1</mn> </mrow> <mo>±</mo> </msubsup> <mo>→</mo> <msubsup> <mover> <mi>χ</mi> <mo>~</mo> </mover> <mrow> <mn>1</mn> </mrow> <mn>0</mn> </msubsup> <mmultiscripts> <mi>Z</mi> <mrow></mrow> <mrow> <mo>(</mo> <mrow></mrow> <mo>∗</mo> <mo>)</mo> </mrow> </mmultiscripts> <mspace width="0.166667em"></mspace> <msubsup> <mover> <mi>χ</mi> <mo>~</mo> </mover> <mrow> <mn>1</mn> </mrow> <mn>0</mn> </msubsup> <mmultiscripts> <mi>W</mi> <mrow></mrow> <mrow> <mo>±</mo> <mo>(</mo> <mrow></mrow> <mo>∗</mo> <mo>)</mo> </mrow> </mmultiscripts> </mrow> </math>   show consistent excesses between ATLAS and CMS in the 2 lepton, 3-lepton and mono-jet searches, assuming      and  $$\Delta m:= m_{\tilde{\chi }_{2}^0} - m_{\tilde{\chi }_{1}^0} \approx 20 \,\, \textrm{GeV}$$  <math> <mrow> <mi>Δ</mi> <mi>m</mi> <mo>:</mo> <mo>=</mo> <msub> <mi>m</mi> <msubsup> <mover> <mi>χ</mi> <mo>~</mo> </mover> <mrow> <mn>2</mn> </mrow> <mn>0</mn> </msubsup> </msub> <mo>-</mo> <msub> <mi>m</mi> <msubsup> <mover> <mi>χ</mi> <mo>~</mo> </mover> <mrow> <mn>1</mn> </mrow> <mn>0</mn> </msubsup> </msub> <mo>≈</mo> <mn>20</mn> <mspace width="0.166667em"></mspace> <mspace width="0.166667em"></mspace> <mtext>GeV</mtext> </mrow> </math>  . This mass configuration arises naturally in SUSY scenarios with wino/bino Dark Matter (DM) or higgsino DM. In these scenarios the lightest supersymmetric particle (LSP), assumed to be the lightest neutralino,  $$\tilde{\chi }_{1}^0$$  <math> <msubsup> <mover> <mi>χ</mi> <mo>~</mo> </mover> <mrow> <mn>1</mn> </mrow> <mn>0</mn> </msubsup> </math>  , as a DM candidate is in good agreement with the observed limits on the DM content of the universe, as well as with negative results from Direct Detection (DD) experiments. We analyze these two scenarios with respect to the observed excesses, taking into account all relevant experimental constraints. We show that in particular wino/bino DM with different signs of the SU(2) and U(1) soft SUSY-breaking parameters can describe well the experimental excesses, while being in agreement with all other constraints.

United Kingdom

Manimala Chakraborti

India

Ipsita Saha

Consistent excesses in the search for  $$\varvec{\tilde{\chi }_{2}^0\tilde{\chi }_{1}^\pm :}$$  <math> <mrow> <msubsup> <mover> <mi>χ</mi> <mo>~</mo> </mover> <mrow> <mn>2</mn> </mrow> <mn>0</mn> </msubsup> <msubsup> <mover> <mi>χ</mi> <mo>~</mo> </mover> <mrow> <mn>1</mn> </mrow> <mo>±</mo> </msubsup> <mo>:</mo> </mrow> </math>   wino/bino vs. Higgsino dark matter

CMS and ATLAS have reported small excesses in the search for low-mass Higgs bosons in the diphoton decay channel at exactly the same mass, 95.4 GeV. These searches rely on improved analysis techniques, enhancing in particular the discrimination against the <math><mrow><mi>Z</mi><mo>→</mo><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math> background. In models beyond the Standard Model (SM) that extend the Higgs sector with triplets, doubly charged Higgs bosons are predicted which can contribute substantially to the diphoton decay rate of a light Higgs boson. The Georgi-Machacek (GM) Model is of particular interest in this context, since despite containing Higgs triplets it preserves the electroweak <math><mi>ρ</mi></math>-parameter to be 1 at the tree level. We show that within the GM model, a Higgs boson with a mass of <math><mo>∼</mo><mn>95</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> with a diphoton decay rate as observed by CMS and ATLAS can be well-described. We discuss the diphoton excess in conjunction with an excess in the <math><mi>b</mi><mover><mi>b</mi><mo>¯</mo></mover></math> final state observed at LEP and an excess observed by CMS in the ditau final state, which have been found at comparable masses with local significances of about <math><mn>2</mn><mi>σ</mi></math> and <math><mn>3</mn><mi>σ</mi></math>, respectively. The presence of a Higgs boson at about 95 GeV within the GM model would imply good prospects of the searches for additional light Higgs bosons. In particular, the observed excess in the diphoton channel would be expected to be correlated in the GM model with a light doubly charged Higgs boson in the mass range between 100 and 200 GeV, which motivates dedicated searches in upcoming LHC Runs.

95 GeV Higgs boson in the Georgi-Machacek model

Slepton coannihilation is one of the most promising scenarios that can bring the predicted Dark Matter (DM) abundance in the the Minimal Supersymmetric Standard Model (MSSM) into agreement with the experimental observation. In this scenario, the lightest supersymmetric particle (LSP), usually assumed to be the lightest neutralino,  $$\tilde{\chi }_{1}^0$$  <math> <msubsup> <mover> <mi>χ</mi> <mo>~</mo> </mover> <mrow> <mn>1</mn> </mrow> <mn>0</mn> </msubsup> </math>   can serve as a Dark Matter (DM) candidate while the sleptons as the next-to-LSPs (NLSPs) lie close in mass. In our previous studies analyzing the electroweak sector of MSSM, a degeneracy between the three generations of sleptons was assumed for the sake of simplicity. In case of slepton coannihilation this directly links the smuons involved in the explanation for  $$(g-2)_\mu $$  <math> <msub> <mrow> <mo>(</mo> <mi>g</mi> <mo>-</mo> <mn>2</mn> <mo>)</mo> </mrow> <mi>μ</mi> </msub> </math>   to the coannihilating NLSPs required to explain the DM content of the universe. On the other hand, in well-motivated top-down models such degeneracy do not hold, and often the lighter stau turns out to be the NLSP at the electroweak (EW) scale, with the smuons (and selectrons) somewhat heavier. In this paper we analyze such a scenario at the EW scale assuming non-universal slepton masses where the first two generations of sleptons are taken to be mass-degenerate and heavier than the staus, enforcing stau coannihilation. We analyze the parameter space of the electroweak MSSM in the light of a variety of experimental data namely, the DM relic density and direct detection limits, LHC data and especially, the discrepancy between the experimental result for the anomalous magnetic moment of the muon,  $$(g-2)_\mu $$  <math> <msub> <mrow> <mo>(</mo> <mi>g</mi> <mo>-</mo> <mn>2</mn> <mo>)</mo> </mrow> <mi>μ</mi> </msub> </math>  , and its Standard Model (SM) prediction. We find an upper limit on the lightest neutralino mass, the lighter stau mass and the mass of the tau sneutrino of about  $$\sim 550 \,\, {\textrm{GeV}}$$  <math> <mrow> <mo>∼</mo> <mn>550</mn> <mspace width="0.166667em"></mspace> <mspace width="0.166667em"></mspace> <mtext>GeV</mtext> </mrow> </math>  . In contrast to the scenario with full degeneracy among the three families of sleptons, the upper limit on the light smuon/selectron mass moves up by  $$\sim 200 \,\, {\textrm{GeV}}$$  <math> <mrow> <mo>∼</mo> <mn>200</mn> <mspace width="0.166667em"></mspace> <mspace width="0.166667em"></mspace> <mtext>GeV</mtext> </mrow> </math>  . We analyze the DD prospects as well as the physics potential of the HL-LHC and a future high-energy  $$e^+e^-$$  <math> <mrow> <msup> <mi>e</mi> <mo>+</mo> </msup> <msup> <mi>e</mi> <mo>-</mo> </msup> </mrow> </math>   collider to investigate this scenario further. We find that the combination DD experiments and  $$e^+e^-$$  <math> <mrow> <msup> <mi>e</mi> <mo>+</mo> </msup> <msup> <mi>e</mi> <mo>-</mo> </msup> </mrow> </math>   collider searches with center of mass energies up to  $$\sqrt{s} \sim 1100 \,\, {\textrm{GeV}}$$  <math> <mrow> <msqrt> <mi>s</mi> </msqrt> <mo>∼</mo> <mn>1100</mn> <mspace width="0.166667em"></mspace> <mspace width="0.166667em"></mspace> <mtext>GeV</mtext> </mrow> </math>   can fully cover this scenario.

$$(g-2)_\mu $$  <math> <msub> <mrow> <mo>(</mo> <mi>g</mi> <mo>-</mo> <mn>2</mn> <mo>)</mo> </mrow> <mi>μ</mi> </msub> </math>   and stau coannihilation: dark matter and collider analysis

The ATLAS Collaboration has recently reported the results of a low-mass Higgs-boson search in the diphoton final state based on the full Run 2 dataset. The results are based on an improved analysis with respect to the previous analysis, which included a part of the Run 2 data, with a substantially better sensitivity. The “model-dependent” search carried out by ATLAS shows an excess of events at a mass of about 95.4 GeV with a local significance of <math><mn>1.7</mn><mi>σ</mi></math>. The results are compatible with a previously reported excess at the same mass, but with somewhat higher significance of <math><mn>2.9</mn><mi>σ</mi></math>, from the CMS collaboration, also based on the full Run 2 dataset. Combining the two results (neglecting possible correlations), we find a signal strength of <math><msubsup><mi>μ</mi><mrow><mi>γ</mi><mi>γ</mi></mrow><mrow><mi>ATLAS</mi><mo>+</mo><mi>CMS</mi></mrow></msubsup><mo>=</mo><msubsup><mn>0.24</mn><mrow><mo>−</mo><mn>0.08</mn></mrow><mrow><mo>+</mo><mn>0.09</mn></mrow></msubsup></math>, corresponding to an excess of <math><mn>3.1</mn><mi>σ</mi></math>. In this work, we investigate the implications of this result, updating a previous analysis based solely on the CMS Run 2 data. We demonstrate that the ATLAS/CMS combined diphoton excess can be interpreted as the lightest Higgs boson in a Two-Higgs doublet model that is extended by a complex singlet (S2HDM) of Yukawa types II and IV, while being in agreement with all other experimental and theoretical constraints.

95.4 GeV diphoton excess at ATLAS and CMS

Recently the ATLAS collaboration has reported the first results of searches for heavy scalar resonances decaying into a Z boson and a lighter new scalar resonance, where the Z boson decays leptonically and the lighter scalar decays into a top-quark pair, giving rise to   <math> <msup> <mi>ℓ</mi> <mo>+</mo> </msup> <msup> <mi>ℓ</mi> <mo>−</mo> </msup> <mi>t</mi> <mover> <mi>t</mi> <mo>¯</mo> </mover> </math>  $$ {\ell}^{+}{\ell}^{-}t\overline{t} $$  final states. This had previously been identified as a smoking-gun signature at the LHC for a first-order electroweak phase transition (FOEWPT) within the framework of two Higgs doublet models (2HDMs). In addition, ATLAS also presented new limits where the Z boson decays into pairs of neutrinos and the lighter scalar resonance into bottom-quark pairs, giving rise to the   <math> <mi>ννb</mi> <mover> <mi>b</mi> <mo>¯</mo> </mover> </math>  $$ \nu \nu b\overline{b} $$  final state. We analyze the impact of these new searches on the 2HDM parameter space, with emphasis on their capability to probe currently allowed 2HDM regions featuring a strong FOEWPT. We also study the complementarity of these new searches with other LHC probes that could target the FOEWPT region of the 2HDM. Remarkably, the ATLAS search in the   <math> <msup> <mi>ℓ</mi> <mo>+</mo> </msup> <msup> <mi>ℓ</mi> <mo>−</mo> </msup> <mi>t</mi> <mover> <mi>t</mi> <mo>¯</mo> </mover> </math>  $$ {\ell}^{+}{\ell}^{-}t\overline{t} $$  final state shows a local 2.85 σ excess (for masses of about 650 GeV and 450 GeV for the heavy and light resonance) in the 2HDM parameter region that would yield a FOEWPT in the early universe, which could constitute the first experimental hint of baryogenesis at the electroweak scale. We analyze the implications of this excess, and discuss the detectability prospects for the associated gravitational wave signal from the FOEWPT. Furthermore, we project the sensitivity reach of the   <math> <msup> <mi>ℓ</mi> <mo>+</mo> </msup> <msup> <mi>ℓ</mi> <mo>−</mo> </msup> <mi>t</mi> <mover> <mi>t</mi> <mo>¯</mo> </mover> </math>  $$ {\ell}^{+}{\ell}^{-}t\overline{t} $$  signature for the upcoming runs of the LHC. Finally, we introduce the python package thdmTools, a state-of-art tool for the exploration of the 2HDM.

Jose No

Kateryna Radchenko

France

María Olea Romacho

First shot of the smoking gun: probing the electroweak phase transition in the 2HDM with novel searches for A → ZH in   <math> <msup> <mi>ℓ</mi> <mo>+</mo> </msup> <msup> <mi>ℓ</mi> <mo>−</mo> </msup> <mi>t</mi> <mover> <mi>t</mi> <mo>¯</mo> </mover> </math>  $$ {\ell}^{+}{\ell}^{-}t\overline{t} $$  and   <math> <mi>ννb</mi> <mover> <mi>b</mi> <mo>¯</mo> </mover> </math>  $$ \nu \nu b\overline{b} $$  final states

The CMS collaboration has recently reported the results of a low-mass Higgs-boson search in the di-photon final state based on the full Run 2 data set with refined analysis techniques. The new results show an excess of events at a mass of about 95 GeV with a local significance of <math><mn>2.9</mn><mspace width="0.2em"></mspace><mi>σ</mi></math>, confirming a previously reported excess at about the same mass and similar significance based on the first-year Run 2 plus Run 1 data. The observed excess is compatible with the limits obtained in the corresponding ATLAS searches. In this work, we discuss the di-photon excess and show that it can be interpreted as the lightest Higgs boson in the Two-Higgs doublet model that is extended by a complex singlet (S2HDM) of Yukawa types II and IV. We show that the second-lightest Higgs boson is in good agreement with the current LHC Higgs-boson measurements of the state at 125 GeV, and that the full scalar sector is compatible with all theoretical and experimental constraints. Furthermore, we discuss the di-photon excess in conjunction with an excess in the <math><mi>b</mi><mover><mrow><mi>b</mi></mrow><mrow><mo>¯</mo></mrow></mover></math> final state observed at LEP and an excess observed by CMS in the di-tau final state, which were found at comparable masses with local significances of about 2σ and 3σ, respectively. We find that the <math><mi>b</mi><mover><mrow><mi>b</mi></mrow><mrow><mo>¯</mo></mrow></mover></math> excess can be well described together with the di-photon excess in both types of the S2HDM. However, the di-tau excess can only be accommodated at the level of 1σ in type IV. We also comment on the compatibility with supersymmetric scenarios and other extended Higgs sectors, and we discuss how the potential signal can be further analyzed at the LHC and at future <math><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup></math> colliders.

The CMS di-photon excess at 95 GeV in view of the LHC Run 2 results

$${\mathcal {C}}{\mathcal {P}}$$  <math> <mrow> <mi>C</mi> <mi>P</mi> </mrow> </math>   violation in the Higgs couplings to fermions is an intriguing, but not yet extensively explored possibility. We use inclusive and differential LHC Higgs boson measurements to fit the  $${\mathcal {C}}{\mathcal {P}}$$  <math> <mrow> <mi>C</mi> <mi>P</mi> </mrow> </math>   structure of the Higgs Yukawa couplings. Starting with simple effective models featuring  $${\mathcal {C}}{\mathcal {P}}$$  <math> <mrow> <mi>C</mi> <mi>P</mi> </mrow> </math>   violation in a single Higgs–fermion coupling, we probe well-motivated models with up to nine free parameters. We also investigate the complementarity of LHC constraints with the electron electric dipole moment bound, taking into account the possibility of a modified electron Yukawa coupling, and assess to which extent  $${\mathcal {C}}{\mathcal {P}}$$  <math> <mrow> <mi>C</mi> <mi>P</mi> </mrow> </math>   violation in the Higgs–fermion couplings can contribute to the observed baryon asymmetry of the universe. Even after including the recent analysis of angular correlations in  $$H\rightarrow \tau ^+\tau ^-$$  <math> <mrow> <mi>H</mi> <mo>→</mo> <msup> <mi>τ</mi> <mo>+</mo> </msup> <msup> <mi>τ</mi> <mo>-</mo> </msup> </mrow> </math>   decays, we find that a complex tau Yukawa coupling alone may be able to account for the observed baryon asymmetry, but with large uncertainties in the baryogenesis calculation. A combination of complex top and bottom quark Yukawa couplings yields a result four times larger than the sum of their separate contributions, but remains insufficient to account for the observed baryon asymmetry.

Henning Bahl

CERN

Elina Fuchs

Judith Katzy

Marco Menen

Krisztian Peters

Matthias Saimpert

Constraining the  $${\mathcal {C}}{\mathcal {P}}$$  <math> <mrow> <mi>C</mi> <mi>P</mi> </mrow> </math>   structure of Higgs-fermion couplings with a global LHC fit, the electron EDM and baryogenesis