With the discovery of a Higgs boson with a mass of 125 gigaelectronvolts (GeV) at the Large Hadron Collider (LHC) at CERN in 2012, the Standard Model (SM) is complete, and despite intensive searches, no new fundamental particle has been observed since then. In fact, a discovery can be challenging without a predictive new physics model because different channels and observables cannot be combined directly and unambiguously. Furthermore, without supporting indirect hints, the signal space to be searched is huge, resulting in diluted significances owing to the look-elsewhere effect. Several LHC processes with multiple leptons in the final state point towards the existence of a new Higgs boson with a mass between 140 GeV to 160 GeV decaying mostly to $\textit{W}$ bosons. While the former strongly reduces the look-elsewhere effect, the latter indicates that it could be a Higgs triplet with zero hypercharge. Within this simple and predictive extension of the SM, we simulate and combine different channels of di-photon production in association with leptons, missing energy, jets, $\textit{etc}$... Using the full run-2 results by ATLAS, including those presented recently at the Moriond conference, an increased significance of 4 standard deviations is obtained for a $\approx$ 152 GeV Higgs. Due to the previously predicted mass range, the look-elsewhere effect is negligible, and this constitutes the highest statistical evidence for a new narrow resonance obtained at the LHC. Furthermore, the model predicts a heavier-than-expected $\textit{W}$ boson, as indicated by the global electroweak fit. If further substantiated, the discovery of a new Higgs would overthrow the SM, provide a compelling case for the construction of future particle colliders, and pave the way to a novel understanding of the known shortcomings of the SM. In particular, the triplet Higgs field can lead to a strong first-order phase transition and could thus be related to the matter anti-matter asymmetry in our Universe.

Switzerland

Andreas Crivellin

China

Saiyad Ashanujjaman

Sumit Banik

Guglielmo Coloretti

India

Siddharth P. Maharathy

South Africa

Bruce Mellado

Growing evidence for a Higgs triplet * The work of Andreas Crivellin is supported by a Professorship Grant from the Swiss National Science Foundation (PP00P21_76884). The work of Saiyad Ashanujjaman is partially supported by the National Natural Science Foundation of China (11835013). Siddharth P. Maharathy acknowledges using the SAMKHYA: High-Performance Computing Facility provided by the Institute of Physics, Bhubaneswar

<p>We examine the correlations between new scalar boson decays to photons and electric dipole moments (EDMs) in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>C</mi><mi>P</mi></mrow></math>-violating flavor-aligned two-Higgs-doublet model (2HDM). It is convenient to work in the Higgs basis <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">{</mo><msub><mi mathvariant="script">H</mi><mn>1</mn></msub><mo>,</mo><msub><mi mathvariant="script">H</mi><mn>2</mn></msub><mo stretchy="false">}</mo></math> where only the first Higgs doublet field <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi mathvariant="script">H</mi><mn>1</mn></msub></math> acquires a vacuum expectation value. In light of the LHC Higgs data, which agree well with Standard Model (SM) predictions, it follows that the parameters of the 2HDM are consistent with the Higgs alignment limit. In this parameter regime, the observed SM-like Higgs boson resides almost entirely in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi mathvariant="script">H</mi><mn>1</mn></msub></math>, and the other two physical neutral scalars, which reside almost entirely in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi mathvariant="script">H</mi><mn>2</mn></msub></math>, are approximate eigenstates of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math> (denoted by the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math>-even <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>H</mi></math> and the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math>-odd <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>A</mi></math>). In the Higgs basis, the scalar potential term <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mover accent="true"><mi>Z</mi><mo stretchy="false">¯</mo></mover><mn>7</mn></msub><msubsup><mi mathvariant="script">H</mi><mn>1</mn><mi>†</mi></msubsup><msub><mi mathvariant="script">H</mi><mn>2</mn></msub><msubsup><mi mathvariant="script">H</mi><mn>2</mn><mi>†</mi></msubsup><msub><mi mathvariant="script">H</mi><mn>2</mn></msub><mo>+</mo><mi mathvariant="normal">H</mi><mo>.</mo><mi mathvariant="normal">c</mi><mo>.</mo></math> governs the charged-Higgs loop contributions to the decay of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>H</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>A</mi></math> to photons. If <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Re</mi><msub><mover accent="true"><mi>Z</mi><mo stretchy="false">¯</mo></mover><mn>7</mn></msub><mi>Im</mi><msub><mover accent="true"><mi>Z</mi><mo stretchy="false">¯</mo></mover><mn>7</mn></msub><mo>≠</mo><mn>0</mn></math>, then <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math>-violating effects are present and allow for an <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>H</mi><mo>+</mo></msup><msup><mi>H</mi><mo>−</mo></msup><mi>A</mi></math> coupling, which can yield a sizable branching ratio for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>A</mi><mo stretchy="false">→</mo><mi>γ</mi><mi>γ</mi></math>. These <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math>-violating effects also generate nonzero EDMs for the electron, the neutron and the proton. We examine these correlations for the cases of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><mi>A</mi></msub><mo>=</mo><mn>95</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><mi>A</mi></msub><mo>=</mo><mn>152</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> where interesting excesses in the diphoton spectrum have been observed at the LHC. These excesses can be explained via the decay of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>A</mi></math> while being consistent with the experimental bound for the electron EDM in regions of parameter space that can be tested with future neutron and proton EDM measurements. This allows for the interesting possibility where the 95 GeV diphoton excess can be identified with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>A</mi></math>, while <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><mi>H</mi></msub><mo>≃</mo><mn>98</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> can account for the best fit to the LEP excess in <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><mi>Z</mi><mi>H</mi></math> with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>H</mi><mo stretchy="false">→</mo><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover></math>.</p>

United States

Howard E. Haber

Correlating <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>A</mi><mo stretchy="false">→</mo><mi>γ</mi><mi>γ</mi></math> with electric dipole moments in the two Higgs doublet model in light of the diphoton excesses at 95 GeV and 152 GeV

In this article, we examine the Standard Model extended by a $\textit{Y}$ = 0 real Higgs triplet, the ∆SM. It contains a $\textit{CP}$-even neutral Higgs (∆ ) and two charged Higgs bosons (∆ ), which are quasi-degenerate in mass. We first study the theoretical constraints from vacuum stability and perturbative unitarity and then calculate the Higgs decays, including the loop-induced modes such as di-photons ($\textit{γγ}$) and $\textit{Zγ}$. In the limit of a small mixing between the SM Higgs and ∆ , the latter decays dominantly to $\textit{WW}$ and can have a sizable branching ratio to di-photon. The model predicts a positive definite shift in the $\textit{W}$ mass, which is compatible with the current global electroweak fit. At the Large Hadron Collider, it leads to a ($\textit{i}$) stau-like signature from $\textit{pp}$ → ∆ ∆ → $$ {\tau}^{+}{\tau}^{-}\nu \overline{\nu} $$ , ($\textit{ii}$) multi-lepton final states from $\textit{pp}$ → $\textit{γ}$ → ∆ ∆ → $\textit{W}$ $\textit{W}$ $\textit{ZZ}$ and $\textit{pp}$ → $\textit{W}$ → ∆ ∆ → $\textit{W}$ $\textit{ZW}$ $\textit{W}$ as well as ($\textit{iii}$) associated di-photon production from $\textit{pp}$ → $\textit{W}$ → ∆ (∆ → $\textit{γγ}$). Concerning ($\textit{i}$), the reinterpretation of the recent supersymmetric tau partner search by ATLAS and CMS excludes $$ {m}_{\Delta ^{\pm }} $$ $\textit{<}$ 110 GeV at 95% CL. From ($\textit{ii}$), some of the signal regions of multi-lepton searches lead to bounds close to the predicted cross-section, but electroweak scale masses are still allowed. For ($\textit{iii}$), the recast of the associated di-photon searches by ATLAS and a combined log-likelihood fit of signal and background to data find that out of the 25 signal regions, 10 provide relevant limits on Br(∆ → $\textit{γγ}$) at the per cent level. Interestingly, 6 signal regions show weaker than expected limits at around 152 GeV, leading to a preference for a non-zero di-photon branching ratio of about (0.7$\textit{±}$0.2)%.

Germany

Siddharth Maharathy

Anatomy of the real Higgs triplet model

The multi-lepton anomalies suggest the existence of a new scalar with a mass between 145 GeV and 155 GeV, which is compatible with indications of the associated production of a narrow resonance with a mass of ≈151 GeV. These anomalies require a sizable branching fraction of the new scalar to <italic>WW</italic>. However, because no <italic>ZZ</italic> signal at this mass has been observed, this implies that the new boson could be the neutral component of an <math altimg='si1.svg'><mi>S</mi><mi>U</mi><msub><mrow><mo stretchy='false'>(</mo><mn>2</mn><mo stretchy='false'>)</mo></mrow><mrow><mi>L</mi></mrow></msub></math> triplet with zero hypercharge. This field leads to a positive definite shift in the <italic>W</italic> mass and is produced via the Drell-Yan process <math altimg='si2.svg'><mi>p</mi><mi>p</mi><mo stretchy='false'>&#8594;</mo><msup><mrow><mi>W</mi></mrow><mrow><mo>&#8270;</mo></mrow></msup><mo stretchy='false'>&#8594;</mo><msup><mrow><mi mathvariant='normal'>&#916;</mi></mrow><mrow><mn>0</mn></mrow></msup><msup><mrow><mi mathvariant='normal'>&#916;</mi></mrow><mrow><mo>&#177;</mo></mrow></msup></math>. We use the side-bands of the ATLAS analysis <cross-ref refid='br0010' id='crf0170'>[1]</cross-ref> of the associated production of the Standard Model Higgs in the di-photon channel to search for this production mode of the triplet. Since the dominant decays of <math altimg='si10.svg'><msup><mrow><mi mathvariant='normal'>&#916;</mi></mrow><mrow><mo>&#177;</mo></mrow></msup></math> depend only on its mass, the effect in the 22 signal categories considered by ATLAS is completely correlated. Combining all channels in a likelihood ratio test, we find that a non-zero Br <math altimg='si4.svg'><mo stretchy='false'>[</mo><msup><mrow><mi mathvariant='normal'>&#916;</mi></mrow><mrow><mn>0</mn></mrow></msup><mo stretchy='false'>&#8594;</mo><mi>&#947;</mi><mi>&#947;</mi><mo stretchy='false'>]</mo></math>, with a best-fit value of 0.66%, is preferred by &#8776;3 <italic>&#963;</italic> for a mass of &#8776;151.5 GeV. While this mass is consistent with the multi-lepton anomalies, there is also an excess at &#8776;127 GeV with a significance of 3.6 <italic>&#963;</italic>. However, the latter is inconsistent with the mass predicted by the multi-lepton anomalies and is in close proximity to the SM Higgs mass, suggesting the possibility of enhanced associated production of the SM Higgs.

Explaining the <italic>&#947;&#947;</italic>&#8239;+&#8239; <italic>X</italic> excesses at &#8776;151.5 GeV via the Drell-Yan production of a Higgs triplet

Statistically significant tensions between the Standard Model (SM) predictions and the measured lepton distributions in differential top cross-sections emerged in LHC Run 1 data and became even more pronounced in Run 2 analyses. Due to the level of sophistication of the SM predictions and the performance of the ATLAS and CMS detectors, this is very remarkable. Therefore, one should seriously consider the possibility that these measurements are contaminated by beyond-the-SM contributions. In this article, we use the differential lepton distributions from the latest ATLAS $$ t\overline{t} $$ analysis to study a new physics benchmark model motivated by existing indications for new Higgses: a new scalar is produced via gluon fusion and decays to (95 GeV) and (152 GeV), which subsequently decay to $$ b\overline{b} $$ and , respectively. In this setup, the total 𝜒 is reduced, compared to the SM, resulting in ∆ = 34 to ∆ = 158, corresponding to a significance of 5.8 to 13 , depending on the SM simulation used. Notably, allowing to vary, the combination of the distributions points towards ≈ 150 GeV, which is consistent with the existing and signals, rendering a mismodelling of the SM unlikely. Averaging the results of the different SM predictions, ( → → ) × Br( → ) × Br( → ) ≈ 9pb is preferred. Assuming that is SM-like, the 95 GeV excess can be explained if decays dominantly to bosons. That latter suggests that is the neutral component of the SU(2) triplet with hypercharge 0.

Uncovering new Higgses in the LHC analyses of differential

Statistically significant excesses exist at around 152 GeV in associated di-photon production (γγ + X) in the sidebands of SM Higgs analyses of ATLAS (using the full run-2 dataset). They are most pronounced in the single-τ, missing-transverse-energy, four-jet and ⩾ 1ℓ+ ⩾ 1b-jet channels (≈ 3σ) and can be explained by the Drell-Yan production of new Higgs bosons, i.e. pp → W *→ H  ±  H 0. We first examine the excesses in a simplified model approach, considering that H  ±  decays to τν, WZ or tb. Both the τν and tb decay modes individually lead to a significance of ⪅ 4σ while for WZ one can obtain at most 3.5σ. This is because the decays of WZ lead to multiple leptons contributing to the two-lepton channel which does not show an excess at 152 GeV. Next, we consider two-Higgs-doublet models where the charged Higgs does not decay to WZ at tree-level, finding a significance of ⪆ 4σ for a branching ratio of the new neutral Higgs to photons of ≈2%. Even though this branching fraction is quite sizable, it can be obtained in composite models or via the Lagrangian term  $${\lambda }_{6}{H}_{1}^{†}{H}_{1}{H}_{2}^{†}{H}_{1}$$  + h.c. breaking the commonly imposed Z 2 symmetry.

Explanation of the excesses in associated di-photon production at 152 GeV in 2HDM

Mellin-Barnes (MB) integrals are a well-known type of integrals appearing in diverse areas of mathematics and physics, such as in the theory of hypergeometric functions, asymptotics, quantum field theory, solid-state physics, etc. Although MB integrals have been studied for more than a century, it is only recently that, due to a remarkable connection found with conic hulls, <math><mrow><mi>N</mi></mrow></math>-fold MB integrals can be computed analytically for <math><mi>N</mi><mo>&gt;</mo><mn>2</mn></math> in a systematic way. In this article, we present an alternative novel technique by unveiling a new connection between triangulations of point configurations and MB integrals, to compute the latter. To make it ready to use, we have implemented our new method in the Mathematica package mbconichulls.wl, an already existing software dedicated to the analytic evaluation of MB integrals using conic hulls. The triangulation method is remarkably faster than the conic hull approach and can thus be used for the calculation of higher-fold MB integrals, as we show here by testing our code on the case of the off-shell massless scalar one-loop <math><mi>N</mi></math>-point Feynman integral up to <math><mi>N</mi><mo>=</mo><mn>15</mn></math>, for which the MB representation has 104 folds. Among other examples of applications, we present new simpler solutions for the off-shell one-loop massless conformal hexagon and two-loop double-box Feynman integrals, as well as for some complicated 8-fold MB integrals contributing to the hard diagram of the two-loop hexagon Wilson loop in general kinematics.

France

Samuel Friot

Multiple Mellin-Barnes integrals and triangulations of point configurations

We explore the possibility that an <math><mrow><mi>S</mi><mi>U</mi><mo>(</mo><mn>2</mn><msub><mrow><mo>)</mo></mrow><mrow><mi>L</mi></mrow></msub></mrow></math> triplet scalar with hypercharge <math><mi>Y</mi><mo>=</mo><mn>0</mn></math> is the origin of the 95 GeV diphoton excess. For a small mixing angle with the Standard Model Higgs, its neutral component has naturally a sizable branching ratio to <math><mi>γ</mi><mi>γ</mi></math> such that its Drell-Yan production via <math><mi>p</mi><mi>p</mi><mo>→</mo><msup><mi>W</mi><mo>*</mo></msup><mo>→</mo><mi>H</mi><msup><mi>H</mi><mo>±</mo></msup></math> is sufficient to obtain the desired signal strength, where <math><msup><mi>H</mi><mo>±</mo></msup></math> is the charged Higgs component of the triplet. The predictions of this setup are (1) The <math><mi>γ</mi><mi>γ</mi></math> signal has a <math><mrow><msub><mrow><mi>p</mi></mrow><mrow><mi>T</mi></mrow></msub></mrow></math> spectrum different from gluon fusion but similar to associated production. (2) Photons are produced in association with tau leptons and jets, but generally do not fall into the vector-boson fusion category. (3) The existence of a charged Higgs with <math><mrow><msub><mrow><mi>m</mi></mrow><mrow><msup><mrow><mi>H</mi></mrow><mrow><mo>±</mo></mrow></msup></mrow></msub><mo>≈</mo><mo>(</mo><mn>95</mn><mo>±</mo><mn>5</mn><mo>)</mo><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math> leading to <math><mrow><mi>σ</mi><mo>(</mo><mi>p</mi><mi>p</mi><mo>→</mo><mi>τ</mi><mi>τ</mi><mi>ν</mi><mi>ν</mi><mo>)</mo><mo>≈</mo><mn>0.4</mn><mtext> </mtext><mtext> </mtext><mi>pb</mi></mrow></math>, which is of the same level as the current limit and can be discovered with Run 3 data. (4) A positive definite shift in the <math><mi>W</mi></math> mass as suggested by the current global electroweak fit.

Anza-Tshilidzi Mulaudzi

<math><mrow><mi>S</mi><mi>U</mi><mo>(</mo><mn>2</mn><msub><mrow><mo>)</mo></mrow><mrow><mi>L</mi></mrow></msub></mrow></math> triplet scalar as the origin of the 95 GeV excess?

Leptoquarks are theoretically well-motivated and have received increasing attention in recent years as they can explain several hints for physics beyond the Standard Model. In this article, we calculate the renormalisation group evolution of models with scalar leptoquarks. We compute the anomalous dimensions for all couplings (gauge, Yukawa, Higgs and leptoquarks interactions) of the most general Lagrangian at the two-loop level and the corresponding threshold corrections at one-loop. The most relevant analytic results are presented in the appendix, while the notebook containing the full expressions can be downloaded at  https://github.com/SumitBanikGit/SLQ-RG  . In our phenomenological analysis, we consider some exemplary cases with focus on gauge and Yukawa coupling unification.

Renormalization group evolution with scalar leptoquarks

The two-Higgs-doublet model with a <math><mrow><mi>U</mi><mo>(</mo><mn>1</mn><msub><mrow><mo>)</mo></mrow><mrow><mi>H</mi></mrow></msub></mrow></math> gauge symmetry (N2HDM-<math><mi>U</mi><mo>(</mo><mn>1</mn><mo>)</mo></math>) has several advantages compared to the “standard” <math><msub><mi>Z</mi><mn>2</mn></msub></math> version (N2HDM-<math><msub><mi>Z</mi><mn>2</mn></msub></math>): It is purely based on gauge symmetries, involves only spontaneous symmetry breaking, and is more predictive because it contains one parameter less in the Higgs potential, which further ensures <math><mi>C</mi><mi>P</mi></math> conservation, i.e., avoiding the stringent bounds from electric dipole moments. After pointing out that a second, so far unknown version of the N2HDM-<math><mi>U</mi><mo>(</mo><mn>1</mn><mo>)</mo></math> exists, we examine the phenomenological consequences for the Large Hadron Collider (LHC) of the differences in the scalar potentials. In particular, we find that while the N2HDM-<math><msub><mi>Z</mi><mn>2</mn></msub></math> predicts suppressed branching ratios for decays into different Higgs bosons for the case of the small scalar mixing (as suggested by Higgs coupling measurements), both versions of the N2HDM-<math><mi>U</mi><mo>(</mo><mn>1</mn><mo>)</mo></math> allow for sizable rates. This is particularly relevant in light of the CMS excess in resonant Higgs-pair production at around 650 GeV of a Standard Model Higgs boson subsequently decaying to photons and a new scalar with a mass of <math><mo>≈</mo><mn>90</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> subsequently decaying to bottom quarks (i.e., compatible with the CMS and ATLAS <math><mi>γ</mi><mi>γ</mi></math> excesses at 95 GeV and <math><mo>≈</mo><mn>670</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>). As we will show, this excess can be addressed within the N2HDM-<math><mi>U</mi><mo>(</mo><mn>1</mn><mo>)</mo></math> in case of a nonminimal Yukawa sector, predicting an interesting and unavoidable <math><mi>Z</mi><mo>+</mo><mi>b</mi><mover><mi>b</mi><mo>¯</mo></mover></math> signal and motivating further asymmetric di-Higgs searches at the LHC.