We compute the complete two-loop unrenormalized electroweak corrections to the Higgsstrahlung process <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>H</mi><mi>Z</mi></math> at future Higgs factories. Our result for a given center-of-mass energy is expressed as a piecewise function defined by several deeply expanded power series, which has high precision and can be further manipulated efficiently. We find that the finite part of the unrenormalized two-loop electroweak corrections can contribute a few thousandths, which might indicate their importance to match the precision of future Higgs factories. This work represents the first complete calculation of the unrenormalized two-loop electroweak corrections for processes with four external particles.

China

Xiang Chen

Xin Guan

Chuan-Qi He

Zhao Li

United Kingdom

Xiao Liu

Yan-Qing Ma

Complete two-loop unrenormalized electroweak corrections to <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>H</mi><mi>Z</mi></math>

In this study, the process <italic>&#947;&#947;</italic>&#8239;&#8594;&#8239; <italic>&#947;&#947;</italic> is investigated to establish constraints on anomalous Higgs boson couplings at <italic>H&#947;&#947;</italic> vertex within the framework of the Standard Model Effective Field Theory (SMEFT). The study is performed for a future muon collider operating at CoM energies of 10 and 30 TeV with integrated luminosities of 10 and 90 ab <math altimg='si9.svg'><msup><mrow /><mrow><mo>&#8722;</mo><mn>1</mn></mrow></msup></math>, respectively, where the incoming photons are modeled using the Weizs&#228;cker-Williams approximation. Signal and background events are simulated using MadGraph, with the SMEFT Lagrangian implemented via FeynRules and UFO frameworks. Parton showering is evaluated with PYTHIA 8, and detector effects are accounted for using Delphes. Limits on the Wilson coefficients <math altimg='si5.svg'><msub><mover accent='true'><mi>c</mi><mo>&#175;</mo></mover><mi>&#947;</mi></msub></math> and <math altimg='si1.svg'><msub><mover accent='true'><mi>c</mi><mo>&#732;</mo></mover><mi>&#947;</mi></msub></math> of the dim-6 operators without and with systematic uncertainties of 5% and 10% are reported at the 95% confidence level, demonstrating the potential of a high-energy muon collider to provide precise constraints on these couplings and presenting a significant improvement over experimental and related phenomenological results.

Türkiye

Serdar Spor

Emre Gurkanli

Analysis of anomalous <italic>H&#947;&#947;</italic> coupling in light-by-light collision at future muon collider

Using a data sample of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>427.9</mn><mtext> </mtext><mtext> </mtext><msup><mrow><mi>fb</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math> collected by the Belle II detector at or near the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">ϒ</mi><mo stretchy="false">(</mo><mn>4</mn><mi>S</mi><mo stretchy="false">)</mo></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">ϒ</mi><mo stretchy="false">(</mo><mn>10753</mn><mo stretchy="false">)</mo></math> resonances, the cross sections for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup><mo stretchy="false">→</mo><msup><mrow><mi>h</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>h</mi></mrow><mrow><mo>−</mo></mrow></msup><mi>J</mi><mo>/</mo><mi>ψ</mi><mo stretchy="false">(</mo><mi>h</mi><mo>=</mo><mi>π</mi><mo>/</mo><mi>K</mi><mo>/</mo><mi>p</mi><mo stretchy="false">)</mo></mrow></math> at center-of-mass energies ranging from 3.8 GeV or the production threshold to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mrow><mn>5.5</mn><mo>/</mo><mn>6.0</mn></mrow><mo>/</mo><mn>7.0</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math> have been measured via initial-state radiation. The cross sections for the processes <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>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup><mi>J</mi><mo>/</mo><mi>ψ</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup><mo stretchy="false">→</mo><msup><mrow><mi>K</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>K</mi></mrow><mrow><mo>−</mo></mrow></msup><mi>J</mi><mo>/</mo><mi>ψ</mi></mrow></math> are consistent with previously published results. The cross sections for these channels obtained by combining with previous Belle results are also given. The process <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>p</mi><mover accent="true"><mi>p</mi><mo stretchy="false">¯</mo></mover><mi>J</mi><mo>/</mo><mi>ψ</mi></math> is investigated for the first time. The yields are small and no significant structure is observed in the cross section versus energy. Searches for vector charmoniumlike states in the <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>J</mi><mo>/</mo><mi>ψ</mi></math> systems, and for associated intermediate states in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>h</mi><mo>±</mo></msup><mi>J</mi><mo>/</mo><mi>ψ</mi></math> systems, are also presented.

M. Abumusabh

I. Adachi

A. Aggarwal

L. Aggarwal

H. Ahmed

Y. Ahn

H. Aihara

N. Akopov

S. Alghamdi

M. Alhakami

A. Aloisio

N. Althubiti

K. Amos

N. Anh Ky

C. Antonioli

D.M. Asner

H. Atmacan

T. Aushev

R. Ayad

V. Babu

H. Bae

N.K. Baghel

S. Bahinipati

P. Bambade

Sw. Banerjee

M. Barrett

M. Bartl

J. Baudot

A. Baur

A. Beaubien

F. Becherer

J. Becker

J.V. Bennett

F.U. Bernlochner

V. Bertacchi

M. Bertemes

E. Bertholet

M. Bessner

S. Bettarini

V. Bhardwaj

F. Bianchi

T. Bilka

D. Biswas

A. Bobrov

D. Bodrov

A. Bondar

G. Bonvicini

J. Borah

A. Boschetti

A. Bozek

M. Bračko

P. Branchini

R.A. Briere

T.E. Browder

A. Budano

S. Bussino

Q. Campagna

M. Campajola

G. Casarosa

C. Cecchi

M.C. Chang

P. Chang

P. Cheema

C. Chen

L. Chen

B.G. Cheon

C. Cheshta

H. Chetri

K. Chilikin

J. Chin

K. Chirapatpimol

H.E. Cho

K. Cho

S.J. Cho

S.K. Choi

S. Choudhury

S. Chutia

J. Cochran

J.A. Colorado-Caicedo

I. Consigny

L. Corona

J.X. Cui

E. De La Cruz-Burelo

S.A. De La Motte

G. De Nardo

G. De Pietro

R. de Sangro

M. Destefanis

S. Dey

R. Dhayal

A. Di Canto

J. Dingfelder

Z. Doležal

I. Domínguez Jiménez

T.V. Dong

X. Dong

M. Dorigo

G. Dujany

P. Ecker

D. Epifanov

Study of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup><mo stretchy="false">→</mo><msup><mrow><mi>h</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>h</mi></mrow><mrow><mo>−</mo></mrow></msup><mi>J</mi><mo>/</mo><mi>ψ</mi></mrow></math> (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>h</mi><mo>=</mo><mi>π</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>K</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>p</mi></math>) via initial-state radiation at Belle II

The determination of the Higgs boson trilinear self-coupling <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>λ</mi><mrow><mn>3</mn><mi>H</mi></mrow></msub></math> is a key goal of the LHC physics program. Its precise measurement will provide unique insight into the scalar potential and the mechanism of electroweak symmetry breaking. Higgs boson pair production in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>g</mi><mi>g</mi><mo stretchy="false">→</mo><mi>H</mi><mi>H</mi></math> process, and particularly in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>H</mi><mi>H</mi><mo stretchy="false">→</mo><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover><mi>γ</mi><mi>γ</mi></math> final state, offers direct sensitivity to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>λ</mi><mrow><mn>3</mn><mi>H</mi></mrow></msub></math>. We present the first implementation of the matrix element method (MEM) at next-to-leading order (NLO) for this process, which is publicly available. The MEM is a statistically optimal approach that maximizes information extraction from collision events. Extending it to NLO represents a major methodological challenge, which we address with a new formalism integrated into the momemta framework. Results with simulated pseudoexperiments demonstrate, in a proof-of-principle study, the strong discriminating power of the method and its ability to extract the coupling modifier <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>κ</mi><mi>λ</mi></msub><mo>=</mo><msub><mi>λ</mi><mrow><mn>3</mn><mi>H</mi></mrow></msub><mo>/</mo><msubsup><mi>λ</mi><mrow><mn>3</mn><mi>H</mi></mrow><mi>SM</mi></msubsup></math> with high precision.

France

Matthias Tartarin

Jan Stark

Novel implementation of the matrix element method at next-to-leading order for the measurement of the Higgs self-coupling <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>λ</mi><mrow><mn>3</mn><mi>H</mi></mrow></msub></math>

This paper presents the first dedicated study of the boosted <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>H</mi><mi>H</mi><mo stretchy="false">→</mo><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover><mi>γ</mi><mi>γ</mi></math> topology as a key probe of physics beyond the Standard Model (SM) in the high-energy double-Higgs boson regime. The analysis presented in this paper focuses on two classes of new-physics scenarios: nonresonant deviations of the quartic gauge-Higgs interaction, parametrized by the coupling modifier <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>κ</mi><mrow><mn>2</mn><mi>V</mi></mrow></msub></math>, and resonant enhancement arising from the decay of a heavy scalar state, modeled within a two-Higgs-doublet framework. We demonstrate that the boosted reconstruction category enhances sensitivity to beyond SM effects that populate the high-<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><mrow><mi>H</mi><mi>H</mi></mrow></msub></math> tail, yielding improved constraints on <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>κ</mi><mrow><mn>2</mn><mi>V</mi></mrow></msub></math> and extending the discovery reach for heavy resonances.

United Arab Emirates

Mohamed Belfkir

Probing new physics in the boosted <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>H</mi><mi>H</mi><mo stretchy="false">→</mo><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover><mi>γ</mi><mi>γ</mi></math> channel at the LHC

We study the Higgs boson decays $$h \rightarrow Z\gamma $$ and $$h \rightarrow m_VZ$$ in a model with vectorlike fermions and $$U(1)_X$$ symmetry ( $$U(1)_X$$ VLFM), where $$m_V$$ is a vector meson ( $$\rho ,\ \omega ,\ \phi ,\ J/\psi ,\ \Upsilon $$ ). The exotic Yukawa interactions in this model generate mixing between Standard Model (SM) fermions and vectorlike fermions, and this mixing affects the Higgs boson mass and Higgs couplings. The corrections to the CP-even and CP-odd $$h\gamma Z$$ couplings come from loop diagrams that involve the new particles, and these corrections have a clear impact on the decay rates of $$h\rightarrow Z\gamma $$ and $$h\rightarrow m_VZ$$ . In suitable regions of the parameter space, the model can produce non-negligible deviations in $$\Gamma _\textrm{NP}(h\rightarrow Z\gamma )/\Gamma _\textrm{SM}(h\rightarrow Z\gamma )$$ and $$\Gamma _\textrm{NP}(h\rightarrow m_VZ)/\Gamma _\textrm{SM}(h\rightarrow m_V Z)$$ , providing possible signals of new physics (NP) beyond the SM.

Rong-Zhi Sun

Shu-Min Zhao

Yue-Tong Liu

Portugal

Xing-Xing Dong

Higgs boson decays $$h\rightarrow Z \gamma $$ and $$h\rightarrow m_V Z$$ in the $$U(1)_X$$ VLFM

In this work, we perform a comprehensive phenomenological analysis of the exotic hadronic states <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>Z</mi><mi>c</mi></msub><mo stretchy="false">(</mo><mn>3900</mn><mo stretchy="false">)</mo></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>Z</mi><mi>c</mi></msub><mo stretchy="false">(</mo><mn>4020</mn><mo stretchy="false">)</mo></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>Z</mi><mi>b</mi></msub><mo stretchy="false">(</mo><mn>10610</mn><mo stretchy="false">)</mo></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>Z</mi><mi>b</mi></msub><mo stretchy="false">(</mo><mn>10650</mn><mo stretchy="false">)</mo></math> within the framework of heavy quark spin symmetry (HQSS) and its violation. By constructing <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi></math>-wave contact interactions between elastic (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><msup><mover accent="true"><mi>D</mi><mo stretchy="false">¯</mo></mover><mo>*</mo></msup><mo>/</mo><msup><mi>D</mi><mo>*</mo></msup><msup><mover accent="true"><mi>D</mi><mo stretchy="false">¯</mo></mover><mo>*</mo></msup></math> or <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>B</mi><msup><mover accent="true"><mi>B</mi><mo stretchy="false">¯</mo></mover><mo>*</mo></msup><mo>/</mo><msup><mi>B</mi><mo>*</mo></msup><msup><mover accent="true"><mi>B</mi><mo stretchy="false">¯</mo></mover><mo>*</mo></msup></math>) and inelastic (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi><mi>π</mi><mo>,</mo><msub><mi>h</mi><mi>c</mi></msub><mi>π</mi></math> or <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">ϒ</mi><mi>π</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>h</mi><mi>b</mi></msub><mi>π</mi></math>) channels, we solve the Lippmann-Schwinger equation to obtain physical production amplitudes and perform a global fit to experimental invariant-mass spectra. Our results demonstrate a striking difference between the charm and bottom sectors: HQSS violation is negligible in the bottom system, leading to comparable peak structures for both <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>Z</mi><mi>b</mi></msub></math> states in all hidden-bottom decay channels. In contrast, significant HQSS breaking is required to describe the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>Z</mi><mi>c</mi></msub></math> system, where the violation is predominantly concentrated in the elastic interactions. This explains the observed selectivity: <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>Z</mi><mi>c</mi></msub><mo stretchy="false">(</mo><mn>3900</mn><mo stretchy="false">)</mo></math> appears prominently only in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi><mi>π</mi></math>, while <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>Z</mi><mi>c</mi></msub><mo stretchy="false">(</mo><mn>4020</mn><mo stretchy="false">)</mo></math> appears only in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>h</mi><mi>c</mi></msub><mi>π</mi></math>. Regardless of whether HQSS violation is taken into account, both the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>Z</mi><mi>b</mi></msub><mo stretchy="false">(</mo><mn>10610</mn><mo stretchy="false">)</mo></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>Z</mi><mi>b</mi></msub><mo stretchy="false">(</mo><mn>10650</mn><mo stretchy="false">)</mo></math> poles can appear near the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>B</mi><msup><mover accent="true"><mi>B</mi><mo stretchy="false">¯</mo></mover><mo>*</mo></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>B</mi><mo>*</mo></msup><msup><mover accent="true"><mi>B</mi><mo stretchy="false">¯</mo></mover><mo>*</mo></msup></math> thresholds, respectively. In the hidden charm sector, however, only the framework that includes HQSS violation can successfully describe the experimental data, leading to a single pole around the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><msup><mover accent="true"><mi>D</mi><mo stretchy="false">¯</mo></mover><mo>*</mo></msup></math> threshold, which is identified as the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>Z</mi><mi>c</mi></msub><mo stretchy="false">(</mo><mn>3900</mn><mo stretchy="false">)</mo></math>. Meanwhile, the structure associated with the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>Z</mi><mi>c</mi></msub><mo stretchy="false">(</mo><mn>4020</mn><mo stretchy="false">)</mo></math> is interpreted as a cusp effect. The robustness of our model is verified against variations of the form factor and cutoff, showing stable results.

Quanxing Ye

Ying Zhang

Peng-Yu Niu

Japan

Qian Wang

Why is the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>Z</mi><mi>c</mi></msub><mo stretchy="false">(</mo><mn>3900</mn><mo stretchy="false">)</mo></math> absent in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>h</mi><mi>c</mi></msub><mi>π</mi></math> final state?

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.

India

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 investigate the dynamically generated <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>h</mi><mn>1</mn></msub></math> state with spin-parity <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>J</mi><mi>P</mi></msup><mo>=</mo><msup><mn>1</mn><mo>+</mo></msup></math> and a mass around 1790 MeV, arising from the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>K</mi><mo>*</mo></msup><msup><mover accent="true"><mi>K</mi><mo stretchy="false">¯</mo></mover><mo>*</mo></msup></math> interaction within the chiral unitary approach. The partial decay widths into the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>K</mi><mn>1</mn></msub><mo stretchy="false">(</mo><mn>1270</mn><mo stretchy="false">)</mo><mover accent="true"><mi>K</mi><mo stretchy="false">¯</mo></mover></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>b</mi><mn>1</mn></msub><mo stretchy="false">(</mo><mn>1235</mn><mo stretchy="false">)</mo><mi>π</mi></math> channels are calculated via a triangular-loop mechanism. In this mechanism, the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>h</mi><mn>1</mn></msub></math> state couples to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>K</mi><mo>*</mo></msup><msup><mover accent="true"><mi>K</mi><mo stretchy="false">¯</mo></mover><mo>*</mo></msup></math>, and final-state interactions between <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>K</mi><mo>*</mo></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mover accent="true"><mi>K</mi><mo stretchy="false">¯</mo></mover><mo>*</mo></msup></math> proceed through pseudoscalar-meson exchange, leading to the final states <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mover accent="true"><mi>K</mi><mo stretchy="false">¯</mo></mover></math> (or <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>π</mi></math>) and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>K</mi><mn>1</mn></msub><mo stretchy="false">(</mo><mn>1270</mn><mo stretchy="false">)</mo></math> [or <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>b</mi><mn>1</mn></msub><mo stretchy="false">(</mo><mn>1235</mn><mo stretchy="false">)</mo></math>]. We also present the invariant-mass distributions of a vector meson and a pseudoscalar meson originating from the decays of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>K</mi><mn>1</mn></msub><mo stretchy="false">(</mo><mn>1270</mn><mo stretchy="false">)</mo></math> or <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>b</mi><mn>1</mn></msub><mo stretchy="false">(</mo><mn>1235</mn><mo stretchy="false">)</mo></math>, along with the corresponding decay widths. Our results show that these decay widths are all of the order of a few MeV. We hope that future experiments can test the predictions presented here, thereby helping to identify this <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>h</mi><mn>1</mn></msub></math> state.

Qing-Hua Shen

Li-Sheng Geng

Xiang Liu

Ju-Jun Xie

Dynamically generated <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>h</mi><mn>1</mn></msub></math> state by the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>K</mi><mo>*</mo></msup><msup><mover accent="true"><mi>K</mi><mo stretchy="false">¯</mo></mover><mo>*</mo></msup></math> interaction and its <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>K</mi><mn>1</mn></msub><mo stretchy="false">(</mo><mn>1270</mn><mo stretchy="false">)</mo><mover accent="true"><mi>K</mi><mo stretchy="false">¯</mo></mover></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>b</mi><mn>1</mn></msub><mo stretchy="false">(</mo><mn>1235</mn><mo stretchy="false">)</mo><mi>π</mi></math> decays

We study Higgs-boson production in association with a top-quark pair ( $$ t\overline{t}H $$ ) at hadron colliders and present the first matching of next-to-next-to-leading order (NNLO) QCD corrections to parton showers using the M NNLO method. For the two-loop amplitude, we employ two established approximations, based on the soft Higgs-boson and high-energy limits, respectively. For the first time, we also construct the latter in full colour and propose a pointwise combination of the two approximations across phase space. By assigning a conservative uncertainty estimate, which remains well below the perturbative uncertainties, we ensure robust and reliable differential predictions, explicitly validated at the one-loop level. Apart from the two-loop amplitude, all remaining ingredients of the M NNLO calculation are included exactly. After thorough validation, we present a series of phenomenological results illustrating the impact of NNLO corrections and parton-shower effects. We consider fiducial predictions for the Higgs-boson decay into photons and include off-shell top-quark decays with tree-level spin correlations in both the dilepton and semileptonic channels.

Switzerland

Christian Biello

Germany

Chiara Savoini

Chiara Signorile-Signorile

Marius Wiesemann

Next-to-next-to-leading order event generation for $$ t\overline{t}H $$ production with approximate two-loop amplitude