In this work, we present the first computation of the full one-loop electroweak radiative corrections to the process $ \mu^- \mu^+ \to W^\pm W^\mp \to hh $ within the Standard Model (SM). Building upon this, we investigate neutral scalar pair production via vector boson fusion at multi–TeV muon colliders in the framework of the Two-Higgs-Doublet Model (2HDM). In our phenomenological analysis, we introduce an enhancement factor, defined as the ratio of the cross section for SM-like Higgs pair production in the 2HDM to the corresponding SM prediction. This factor is systematically evaluated across the allowed regions of parameter space in both Type-X and Type-Y 2HDMs. Our results indicate that, within the viable Type-X parameter space, this factor can reach a value of 3, whereas it remains between 0.91 and 0.95 across the allowed parameter space of the Type-Y scenario. We observe that the enhancement factor exhibits distinct behaviors in the Type-X and Type-Y 2HDMs. This feature provides a promising opportunity to discriminate between the two scenarios through precision measurements of double Higgs production at future multi–TeV colliders. Furthermore, we perform a detailed scan of the cross sections for both CP-odd and CP-even Higgs pair production over the viable parameter spaces of the Type-X and Type-Y 2HDMs. In the Type-Y scenario, at a center-of-mass (CoM) energy $ \sqrt{s} = 10\; \text{TeV} $ and an integrated luminosity of $ {\cal{L}} = 10000\; \text{fb}^{-1} $ , both CP-odd and CP-even Higgs pair production in the $ t\bar{t}b\bar{b} $ final state, with subsequent top-quark decays into leptons and bottom quarks, can be probed with a statistical significance exceeding the $ 2\sigma $ level at several viable parameter points.

Vietnam

Khiem Hong Phan

Quang Hoang-Minh Pham

Neutral scalar pair production via $\textit{W}$-boson fusion at multi–TeV muon colliders * This work is supported by the Vietnam National Foundation for Science Technology Development (NAFOSTED) (103.01-2023.16)

Constrained by the complexity of theoretical calculations, current research on genuine tripartite nonlocality (GTN) within the relativistic framework concentrates mainly on Greenberger–Horne–Zeilinger-like states, with few studies addressing W states or even general tripartite states. In this paper, we apply numerical methods to investigate how environmental decoherence and spacetime dilaton influence GTN and genuine tripartite entanglement (GTE) of W states. Our results show that GTN in the physically accessible region displays a “sudden death” phenomenon and that sufficiently strong decoherence completely destroys GTN. By contrast, GTE in the physically accessible region initially remains unchanged and then decays only when the dilaton parameter becomes large. Notably, the GTN and GTE in the physically accessible region can be enhanced by adjusting the decoherence parameter. Furthermore, we also find that the GTN in the physically inaccessible region cannot be generated, whereas the GTE will be produced there. This implies that GTE can cross the event horizon of a black hole and realize the redistribution of quantum entanglement. Finally, we further discuss whether the GTN can be transferred to the bipartite subsystem of the system.

China

Chun-yao Liu

Zheng-wen Long

Qi-liang He

Nonlocality and entanglement transfer of an open three-qubit W state in the background of a dilaton black hole

Top-quark decays are sensitive probes of light charged Higgs bosons (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>H</mi></mrow><mrow><mo>±</mo></mrow></msup></mrow></math>) due to the sizable <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>t</mi><mover accent="true"><mi>t</mi><mo stretchy="false">¯</mo></mover></math> production cross section at the LHC in conjunction with their distinct experimental signatures. While dedicated ATLAS and CMS searches considered only <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>H</mi></mrow><mrow><mo>±</mo></mrow></msup></mrow></math> decays into <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>τ</mi><mi>ν</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>c</mi><mi>s</mi></math>, or <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>c</mi><mi>b</mi></math> for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><msup><mi>H</mi><mo>±</mo></msup></msub><mo>&lt;</mo><msub><mi>m</mi><mi>t</mi></msub></math>, the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>W</mi><mi>Z</mi></math> channel remains unexplored, despite being the dominant mode in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi><mi>U</mi><mo stretchy="false">(</mo><mn>2</mn><msub><mo stretchy="false">)</mo><mi>L</mi></msub></math> triplet models. Since top-quark pair production with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>t</mi><mo stretchy="false">→</mo><msup><mi>H</mi><mo>±</mo></msup><mi>b</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>H</mi><mo>±</mo></msup><mo stretchy="false">→</mo><mi>W</mi><mi>Z</mi></math> gives rise to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>t</mi><mover accent="true"><mi>t</mi><mo stretchy="false">¯</mo></mover><mi>Z</mi></math>-like signatures, we recast existing <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>t</mi><mover accent="true"><mi>t</mi><mo stretchy="false">¯</mo></mover><mi>Z</mi></math> analyses to search for signs of charged Higgs bosons and set novel limits on the product of branching fractions <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>Br</mi><mo stretchy="false">(</mo><mi>t</mi><mo stretchy="false">→</mo><msup><mrow><mi>H</mi></mrow><mrow><mo>±</mo></mrow></msup><mi>b</mi><mo stretchy="false">)</mo><mo>×</mo><mi>Br</mi><mo stretchy="false">(</mo><msup><mrow><mi>H</mi></mrow><mrow><mo>±</mo></mrow></msup><mo stretchy="false">→</mo><mi>W</mi><mi>Z</mi><mo stretchy="false">)</mo></mrow></math>. These constraints turn out to be at the sub-permille level, despite the observed <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>2</mn><mi>σ</mi></math> preference for a nonzero value. Interpreted within the hypercharge <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Y</mi><mo>=</mo><mn>0</mn></math> Higgs triplet model, this translates into a stringent constraint on the triplet Higgs vacuum expectation value of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>v</mi><mi mathvariant="normal">Δ</mi></msub><mo>≲</mo><mn>2</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>, which is stronger than those from the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>c</mi><mi>s</mi><mo>,</mo><mi>τ</mi><mi>ν</mi></math> modes and even surpasses electroweak precision constraints from the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ρ</mi></math> parameter. Moreover, the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>2</mn><mi>σ</mi></math> preference for a nonzero cross section further strengthens the cumulative case for a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mo>≈</mo><mn>152</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math> boson as suggested, in particular, by diphoton excesses.

Germany

Saiyad Ashanujjaman

Spain

Andreas Crivellin

South Africa

India

Siddharth P. Maharathy

Bruce Mellado

Searching for a charged Higgs boson in top-quark decays via the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>W</mi><mi>Z</mi></math> mode

In this paper, we present a remarkably simple expression for the exact solution to the $$D = 5,$$ $${\mathscr {N}}= 2$$ supergravity coupled to three vector multiplets with the pre-potential $$\mathscr {V} = STU -W^2U \equiv 1,$$ which represents a five-dimensional static Kaluza–Klein black hole with squashed $$S^3$$ horizons and four independent electric charges. It is asymptotically locally flat and has a spatial infinity $$R \times S^1 \hookrightarrow S^2.$$ We compute its conserved charges via the counterterm method and demonstrate that the thermodynamic quantities satisfy both the first law and Bekenstein–Smarr mass formula, provided the length of the compact extra dimension is treated as a thermodynamic variable. Besides, we have, for the first time, observed a novel black hole splitting phenomenon induced by the extra charge – namely, when the fourth Abelian vector field is added, the black hole solution to the usual $\textit{STU}$ model is split into two different branches in the new $$STU-W^2U$$ model. This fact hints that the solution space of the $$STU-W^2U$$ model has a much richer structure than that of the usual $\textit{STU}$ model. We also demonstrate that the special $$S^2U-W^2U$$ model can be converted into the usual $\textit{STU}$ model which suggests that one should coherently set $$\rho _2 = 0$$ in the general expression of the structure function: $$f(\rho ) = 1 -\rho _1/\rho +\rho _2/\rho ^2.$$

Di Wu

Shuang-Qing Wu

Static four-charge squashed black hole in five-dimensional $$STU-W^2U$$ supergravity and its thermodynamics

Precision measurements of top-quark decays provide powerful probes of physics beyond the Standard Model (SM). While the impact of dimension-six operators in the SM effective field theory (SMEFT) has been extensively studied, the role of dimension-eight contributions remains largely unexplored, despite their potential importance as experimental precision improves. In this work, we present a combined analysis of dimension-six and a representative subset of dimension-eight SMEFT effects using the W-boson helicity fractions in top-quark decays. We compute the leading-order contributions of these operators to the top-quark decay width and helicity fractions, and perform one-parameter and selected two-parameter <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>χ</mi><mn>2</mn></msup></math> fits to the combined ATLAS (A Toroidal LHC ApparatuS) and CMS (Compact Muon Solenoid) measurements at a reference scale <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">Λ</mi><mo>=</mo><mn>1</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></mrow></math>. From the fit results, we find that the inclusion of dimension-eight contributions affects the allowed parameter space of several dimension-six coefficients through nontrivial correlations and degeneracies. Since the leading dimension-eight contributions enter at the same order <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><msup><mrow><mi mathvariant="normal">Λ</mi></mrow><mrow><mo>−</mo><mn>4</mn></mrow></msup><mo stretchy="false">)</mo></mrow></math> as the squared dimension-six terms retained in our analysis, this highlights the importance of a consistent treatment of the EFT expansion when interpreting SMEFT constraints.

Iran

Afsaneh Kianfar

Gholamhossein Haghighat

CERN

Mojtaba Mohammadi Najafabadi

<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>W</mi></mrow></math>-boson helicity fractions in top decay as probes of dimension-six and dimension-eight SMEFT operators

In this paper we make a proposal for the solution to a long-standing problem — the asymptotic expansions of the modular $\textit{S}$-transform of a generalised Gibbs ensemble (GGE) in a theory with $$ {\mathcal{W}}_3 $$ symmetry where the GGE includes the first non-trivial charge. Equivalently, we give a proposal for the modular $\textit{S}$-transform of traces of arbitrary powers of the zero mode $\textit{W}$ . We provide evidence in the form of exact results using Zhu’s recursion, results obtained using conjectured results for Verma modules, and exact results for the particular value $\textit{c}$ = –2. We expect these have generalisations to other symmetry algebras/hierarchies such as the Virasoro algebra/KdV charges, and to GGEs with arbitrary finite sets of charges.

France

Max Downing

United Kingdom

Faisal Karimi

Tanmoy Sengupta

Adarsh Sudhakar

Gérard Watts

Modular properties of $$ {\mathcal{W}}_3 $$ generalised Gibbs ensembles

Loops of portal matter (PM) fields carrying both dark and Standard Model (SM) quantum numbers can lead to the kinetic mixing (KM) of the SM photon and the analogous dark photon (DP) of a phenomenologically interesting magnitude. However, in specific frameworks, different loops of these same PM fields can also lead to other new types of interactions between some of the SM fields and the DP via the generation of “dark moment”-like couplings, even though the SM fields carry a zero dark charge at tree level. In recent work, this possibility has been explored for the case when these SM fields are fermionic. In this paper, we extend this idea to the case of the SM <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>W</mi></math> boson, employing a previously examined model wherein PM consists of a complex scalar triplet plus a complex singlet, both of which obtain vacuum expectation values and thus also generate the DP mass. While this setup results in a somewhat stronger interaction between the DP and the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>W</mi></math> than in the familiar KM setup, the rate for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>W</mi><mo>+</mo><mi>DP</mi></mrow></math> production at the LHC is shown to still be rather small and is very difficult to observe due to large SM backgrounds. The direct production of the scalar PM itself, however, is shown to lead to similar new physics signatures but with much larger rates, and are considered here in their own right. The properties of such new PM states may already be constrained by LHC searches in both the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>W</mi><mo>±</mo></msup><mo>+</mo></math> missing transverse energy (MET) and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>W</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>W</mi></mrow><mrow><mo>−</mo></mrow></msup><mo>+</mo><mi>MET</mi></mrow></math> channels.

United States

Thomas G. Rizzo

Model for dark moments of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>W</mi></math> boson

We consider the hypothetical possibility of neutral gauge bosons (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>Z</mi><mo>′</mo></msup></math>) with flavor-specific leptophilic couplings. For such New Physics (NP) interactions, the current experimental constraints are much more relaxed in the heavy mass regime, particularly for masses <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>≥</mo><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><mn>1</mn><mo stretchy="false">)</mo><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math>. However, in the presence of a leptophilic <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>Z</mi><mo>′</mo></msup></math>, leptonic decay modes of the electroweak gauge bosons and Higgs can be corrected at the loop level. Using the existing upper bounds on the corresponding decay widths, we find that one can impose stronger exclusion limits on the interactions of a heavy <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>Z</mi><mo>′</mo></msup></math>. Future updates on the aforesaid decay channels can be used in complementarity with the proposed lepton colliders to probe even weaker leptophilic NP interactions at the TeV scale and beyond.

Bibhabasu De

Amitabha Dey

Constraining the heavy leptophilic neutral gauge bosons through the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>Z</mi><mo stretchy="false">→</mo><msup><mrow><mo>ℓ</mo></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mo>ℓ</mo></mrow><mrow><mo>−</mo></mrow></msup></mrow></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>W</mi></mrow><mrow><mo>±</mo></mrow></msup><mo stretchy="false">→</mo><msup><mrow><mo>ℓ</mo></mrow><mrow><mo>±</mo></mrow></msup><msub><mrow><mi>ν</mi></mrow><mrow><mo>ℓ</mo></mrow></msub></mrow></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>h</mi><mo stretchy="false">→</mo><msup><mo>ℓ</mo><mo>+</mo></msup><msup><mo>ℓ</mo><mo>−</mo></msup></math> decays

We perform a detailed computation of the helicity-dependent next-to-leading power leading logarithms in $\textit{W}$ +$\textit{jet}$ production, originating from next-to-soft gluon radiation and soft (anti-)quark emissions. These contributions are systematically captured via helicity-sensitive spinor shifts and soft quark operators. The resulting expressions exhibit full agreement with a recently proposed universal structure of NLP corrections for processes involving the production of an arbitrary massive colourless final state in association with a jet.

Sourav Pal

Satyajit Seth

NLP threshold corrections to $\textit{W}$ +$\textit{jet}$ production

Recent experimental data from <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>MINER</mi><mi>ν</mi><mi mathvariant="normal">A</mi></mrow></math> on transverse kinematics observables across four different nuclear targets—carbon, oxygen, iron, and lead—have been utilized to refine the modeling of final state interaction effects in the nuwro Monte Carlo neutrino event generator. For this purpose, we have developed an event reweighting tool for future applications to adjust the strength of final-state interactions. This study highlights the requirement for stronger nucleon reinteractions than previously assumed, but it still falls within the uncertainty range observed in a study comparing proton transparency measurements. This conclusion has significant implications for both experimental and theoretical work involving nuwro.

Poland

Hemant Prasad

Jan T. Sobczyk

Rwik Dharmapal Banerjee

J. Luis Bonilla

Krzysztof M. Graczyk

Beata E. Kowal

Artur M. Ankowski

Fine-tuning final state interactions model in the nuwro Monte Carlo event generator