The search for signatures of supersymmetric models remains one of the main item on the BSM search program at the LHC, with EW SUSY partners still allowed with masses as low as a few hundred GeV. Over the last years, searches for the “golden channel”, $$pp \rightarrow \tilde{\chi }_{2}^0 \tilde{\chi }_{1}^\pm \rightarrow \tilde{\chi }_{1}^0 Z^{(*)} \, \tilde{\chi }_{1}^0 W^{\pm (*)}$$ show consistent excesses between ATLAS and CMS in the 2 soft-lepton and 3 soft-lepton plus $$E_T\hspace{-4.5mm}/$$ searches, assuming and $$\Delta m_{21}{:=} m_{\tilde{\chi }_{2}^0} - m_{\tilde{\chi }_{1}^0} \approx 20 \,\, \textrm{GeV}$$ . We interpret these excesses in the framework of the Next-to-Minimal Supersymmetric Standard Model (NMSSM). We assume a singlino dominated lightest neutralino, $$\tilde{\chi }_{1}^0$$ , as a Dark Matter (DM) candidate. The second and third lightest neutralinos, $$\tilde{\chi }_{2,3}^0$$ are higgsino like, with the higgsino mixing parameter $$\mu $$ being smaller than the soft SUSY-breaking bino and wino masses, $$M_1$$ and $$M_2$$ . We furthermore assume the approximate GUT relations $$M_1 \sim M_2/2 \sim M_3/6$$ , with the implication for our scenario of a gluino mass . Scalar fermion masses are assumed to be heavy and do not play a role in our analysis. We find that this scenario is in agreement with all relevant experimental constraints, comprising the LHC searches for SUSY particles and additional Higgs bosons, the LHC Higgs-boson rate measurements, the DM direct detection limits and the upper limit on the DM relic density. We demonstrate that this scenario gives an excellent description of the observed excesses in the search for 2 and 3 soft-leptons plus $$E_T\hspace{-4.5mm}/$$ , with $$m_{\tilde{\chi }_{2}^0} \sim m_{\tilde{\chi }_{3}^0} \sim m_{\tilde{\chi }_{1}^\pm }$$ and $$\Delta m_{21} \sim 20 \,\, \textrm{GeV}$$ . This constitutes the first explanation of the soft-lepton excesses in a model with GUT relations among the soft SUSY-breaking parameters.

Italy

Emanuele Bagnaschi

United Kingdom

Manimala Chakraborti

Spain

Sven Heinemeyer

India

Ipsita Saha

Consistent excesses in the LHC electroweak SUSY searches: GUT-based Singlino/Higgsino interpretation in the NMSSM

The shape of the Higgs potential is modified by the presence of additional scalar fields, as predicted in many Beyond-Standard-Model (BSM) scenarios. In such cases, deviations in the Higgs self-interactions — in particular the trilinear Higgs couplings — could serve to disentangle the physics beyond the Standard Model (SM). While the SM predicts only one trilinear Higgs coupling, extended scalar sectors allow for additional self-interactions that can manifest themselves in Higgs pair production, via the $\textit{s}$-channel contribution of a heavy 𝒞𝒫-even scalar $\textit{H}$. We present the first sensitivity study to such a BSM trilinear scalar coupling using machine learning. Specifically, we train a neural network on the invariant mass distributions of Higgs pair production at the HL-LHC to extract $$ {\xi}_H^t\times {\lambda}_{hhH} $$ , i.e. the product of the resonant $\textit{H}$ top-Yukawa coupling and the trilinear coupling of $\textit{H}$ to the two SM-like Higgses in the final state, $\textit{hh}$. Assuming a hypothetical $\textit{H}$ mass of 450 GeV, we show that, depending on future experimental efficiencies and uncertainties, a determination of $$ {\xi}_H^t\times {\lambda}_{hhH} $$ at the 10–20% level may be achievable by the end of the HL-LHC. We present a simple and more efficient alternative to classical statistical methods, proving the efficiency of neural networks for both hypothesis testing and parameter estimation, which outperforms conventional maximum likelihood methods in this context.

Markus Frank

Germany

Margarete Mühlleitner

Kateryna Radchenko

Experimental determination of BSM triple Higgs couplings at the HL-LHC with neural networks

The real singlet extension of the Standard Model (SM), RxSM, is one of the simplest Beyond-the-Standard Model (BSM) theories that can accommodate a strong first-order electroweak phase transition (SFOEWPT). We survey the possible thermal histories of the early Universe in the RxSM, and find that a SFOEWPT can occur in this model as single- or two-step phase transitions. We investigate complementary approaches to probe such scenarios experimentally: either via searches for a stochastic background of gravitational waves (GWs) or via searches for di-Higgs production processes at future collider experiments: the HL-LHC, or a possible high-energy $\textit{e}$ $\textit{e}$ collider. For these analyses we consistently include one-loop corrections to the trilinear Higgs couplings. We find that entirely different phenomenological signals are possible, depending on how the SFOEWPT occurs. In scenarios where such a transition is driven by the Higgs doublet direction in field space, BSM deviations in properties of the detected Higgs boson, particularly in the trilinear scalar coupling, typically lead to observable signals at colliders, while the regions of parameter space with detectable GW signals are very narrow. On the other hand, if the SFOEWPT is triggered by the singlet field direction, the detected Higgs boson is very SM-like and no signs of BSM physics would appear in di-Higgs production processes. However, strong GW signals could be produced for significant parts of the RxSM parameter space with singlet-driven SFOEWPT. This work highlights the crucial importance of exploiting complementary experimental directions to determine the dynamics of the electroweak phase transition and access the shape of the Higgs potential realised in Nature.

Johannes Braathen

South Korea

Carlos Pulido Boatella

Alain Verduras Schaeidt

Complementarity of gravitational wave analyses and di-Higgs production in the exploration of the electroweak phase transition dynamics in the RxSM

<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

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.

Andrea Parra Arnay

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.

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.