<p>We investigate the search for doubly charged Higgs bosons in the Georgi-Machacek (GM) model at same-sign lepton colliders. The dominant production mode is vector boson fusion, through which the particle is singly produced and decays into a pair of same-sign <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>W</mi></math> bosons if the triplet vacuum expectation value is sufficiently large, as allowed in the GM model. Considering the leptonic decays of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>W</mi></math> bosons, we discuss the discovery reach of the signal and a method to extract the mass of the doubly charged Higgs boson. It is impossible to construct the transverse mass of the decay product to obtain the mass because of the neutrinos radiated from the initial-state leptons. Alternatively, we propose to make use of the invariant mass of the same-sign leptons. We perform <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>χ</mi><mn>2</mn></msup></math> fitting using the analytical formula for the invariant mass distribution and demonstrate that this approach is effective in extracting the information on the mass. We also compare the process with pair production processes at the opposite-sign lepton colliders.</p>

Taiwan

Cheng-Wei Chiang

Kazuki Enomoto

Min-Yuan Liao

Doubly charged Higgs boson at same-sign lepton colliders

<p>In this work, we study a dark matter scenario where a dark <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi></math> boson possessing mass mixing with the Standard Model (SM) <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi></math> boson couples to the dark matter (DM) candidate and serves as the portal to the SM. The UV origin of the mass mixing in the form of an extra dark Higgs doublet and a scalar dark singlet provides new exotic scalars which can constitute the final state of DM annihilation during freeze-out. We find that existing constraints on the observed Higgs coupling strength, exotic Higgs searches, and dark matter observables complement each other, while future searches for exotic Higgs decays and resonant heavy scalars at HL-LHC will be sensitive to part of the allowed parameter space.</p>

China

Chuan-Ren Chen

Mexico

Leon M.G. de la Vega

Dark <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi></math>-mediated dark matter with verifiable exotic scalars

We discuss the landscape of flavor physics at the Circular Electron-Positron Collider (CEPC), based on the nominal luminosity outlined in its Technical Design Report. The CEPC is designed to operate in multiple modes to address a variety of tasks. At the $\textit{Z}$ pole, the expected production of 4 Tera $\textit{Z}$ bosons will provide unique and highly precise measurements of $\textit{Z}$ boson couplings, while the substantial number of boosted heavy-flavored quarks and leptons produced in clean $\textit{Z}$ decays will facilitate investigations into their flavor physics with unprecedented precision. We investigate the prospects of measuring various physics benchmarks and discuss their implications for particle theories and phenomenological models. Our studies indicate that, with its highlighted advantages and anticipated excellent detector performance, the CEPC can explore beauty and $\textit{τ}$ physics in ways that are superior to or complementary with the Belle II and Large-Hadron-Collider-beauty experiments, potentially enabling the detection of new physics at energy scales of 10 TeV and above. This potential also extends to the observation of yet-to-be-discovered rare and exotic processes, as well as testing fundamental principles such as lepton flavor universality, lepton and baryon number conservation, etc., making the CEPC a vibrant platform for flavor physics research. The $\textit{WW}$ threshold scan, Higgs-factory operation and top-pair productions of the CEPC further enhance its merits in this regard, especially for measuring the Cabibbo-Kobayashi-Maskawa matrix elements, and Flavor-Changing-Neutral-Current physics of Higgs boson and top quarks. We outline the requirements for detector performance and considerations for future development to achieve the anticipated scientific goals. The role of machine learning for innovative detector design and advanced reconstruction algorithms is also stressed. The CEPC flavor physics program not only develops new capabilities for exploring flavor physics beyond existing projects but also enriches the physics opportunities of this machine. It should be remarked that, given the richness of the CEPC flavor physics, this manuscript is not meant to be a comprehensive survey, but rather an investigation of representative cases. Uncovering the full potential of flavor physics at the CEPC will require further dedicated explorations in the future.

Xiaocong Ai

United States

Wolfgang Altmannshofer

Peter Athron

Xiaozhi Bai

Lorenzo Calibbi

Germany

Lu Cao

Yuzhi Che

Chunhui Chen

Ji-Yuan Chen

Long Chen

Mingshui Chen

Shanzhen Chen

Xuan Chen

Shan Cheng

Switzerland

Andreas Crivellin

Hanhua Cui

France

Olivier Deschamps

Sébastien Descotes-Genon

Xiaokang Du

Shuangshi Fang

Yu Gao

Yuanning Gao

Li-Sheng Geng

Pablo Goldenzweig

Jiayin Gu

Feng-Kun Guo

Yuchen Guo

Zhi-Hui Guo

Tao Han

Hong-Jian He

Jibo He

Miao He

Xiaogang He

Yanping Huang

Gino Isidori

Quan Ji

Jianfeng Jiang

Xu-Hui Jiang

Slovenia

Jernej F. Kamenik

Tsz Hong Kwok

Gang Li

Geng Li

Haibo Li

Haitao Li

Hengne Li

Honglei Li

Liang Li

Lingfeng Li

Qiang Li

Shu Li

Xiaomei Li

Xin-Qiang Li

Yiming Li

Yubo Li

Yuji Li

Zhao Li

Hao Liang

Zhijun Liang

Libo Liao

Zoltan Ligeti

Jia Liu

Jianbei Liu

Tao Liu

Yi Liu

Yong Liu

Zhen Liu

Xinchou Lou

Peng-Cheng Lu

Italy

Alberto Lusiani

Hong-Hao Ma

Kai Ma

Farvah Mahmoudi

Yajun Mao

Yaxian Mao

David Marzocca

Juan-Juan Niu

Soeren Prell

Huirong Qi

Sen Qian

Zhuoni Qian

Qin Qin

Ariel Rock

Jonathan L. Rosner

Manqi Ruan

Dingyu Shao

Chengping Shen

Xiaoyan Shen

Haoyu Shi

United Kingdom

Liaoshan Shi

Zong-Guo Si

Cristian Sierra

Huayang Song

Shufang Su

Wei Su

Zhijia Sun

Michele Tammaro

Dayong Wang

En Wang

Flavor physics at the CEPC: a general perspective * We acknowledge financial support from the National Natural Science Foundation of China (NSFC) (12125507, 12047503, 12035008, 2211530479, 12475094, 12135006, 12075097, 12375086, 2022YFA1601903, 12061141007, 12375091, 12342502, 12235018, 12335003, 12105100, 12475106, 11961141015, 12188102, 12175245, 12205171, 12321005, tsqn202312052, 2024HWYQ-005, 12405121, 12447167, 12061141006, 12405102, 12125503,12305115, 12075213, 12335005, 12235008); the Chinese Academy of Sciences (YSBR-101, XDB34030000); the National Key R&D Program of China (2022YFE0116900, 2023YFA1606703, 2022YFA1601901); the National Key Research and Development Program of China (2023YFA1606300); the Excellent Postdoctoral Program of Jiangsu Province (2023ZB891); the Shenzhen Science and Technology Program (202206193000001, 20220816094256002); the Natural Science Foundation for Distinguished Young Scholars of Henan Province (242300421046); the Beijing Municipal Natural Science Foundation (JQ22002); the Area of Excellence (AoE/P-404/18-3) and the General Research Fund (16304321) (both grants are issued by the Research Grants Council of Hong Kong S.A.R); the MOST National Key R&D Program (2023YFA1606303); the Shanghai Key Laboratory for Particle Physics and Cosmology, Key Laboratory for Particle Astrophysics and Cosmology (Ministry of Education), Shanghai Jiao Tong University

Weak supervision combines the advantages of training on real data with the ability to exploit signal properties. However, training a neural network using weak supervision often requires an excessive amount of signal data, which severely limits its practical applicability. In this study, we propose addressing this limitation through data augmentation, increasing the training data’s size and diversity. Specifically, we focus on physics-inspired data augmentation methods, such as $\textit{p}$ smearing and jet rotation. Our results demonstrate that data augmentation can significantly enhance the performance of weak supervision, enabling neural networks to learn efficiently from substantially less data.

Zong-En Chen

Feng-Yang Hsieh

Improving the performance of weak supervision searches using data augmentation

Right-handed neutrinos $\textit{ν}$ play a crucial role in flavor-changing neutral-current processes with missing energy, such as and , where Belle-II reports unexpectedly large branching fraction in $$ B\to K\nu \overline{\nu} $$ decays. Assuming $\textit{ν}$ is the partner of the active neutrino $\textit{ν}$ in the standard model, a Dirac-type neutrino framework emerges. We investigate a scenario of radiative Dirac neutrino mass generation in a scalar leptoquark (LQ) model with a global U(1) symmetry to suppress Majorana mass, tree-level Dirac mass, and diquark couplings. The simplest LQ realization consists of two $\textit{S}$ = (3$\textit{,}$ 1$\textit{,}$ −1$\textit{/}$3) LQs with distinct U(1) charges. A non-Casas-Ibarra parametrization is proposed to match neutrino data with fewer model parameters. Imposing current experimental constraints from meson mixing and lepton flavor-violating processes, we find that right-handed neutrino effects can significantly enhance $$ B\to {K}^{\left(\ast \right)}\nu \overline{\nu} $$ and $$ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $$ . Additionally, the model predicts excesses in $\textit{R}$ from $$ B\to D\tau \overline{\nu} $$ that remain within 1$\textit{σ}$ of current experimental data.

Chuan-Hung Chen

Leon Vega

Leptoquark-mediated Dirac neutrino mass and its impact on $$ B\to K\nu \overline{\nu} $$ and $$ K\to \pi \nu \overline{\nu} $$ decays

Certain models of inert multiplets allow for semi-annihilation processes, in which two dark matter candidates annihilate to a dark matter particle and a non-dark matter particle. The existence of these processes can alleviate certain constraints and substantially modify the indirect detection signal. In this paper, we study current indirect detection constraints on the semi-annihilation of inert scalar multiplets. We show that there exist gauge numbers for which dark matter can be thermally produced and be compatible with indirect detection constraints even for very cuspy galactic dark matter density profiles.

Hugues Beauchesne

Indirect detection constraints on semi-annihilation of inert scalar multiplets

The internal structure of the light scalar meson <math><msub><mi>a</mi><mn>0</mn></msub><mo>(</mo><mn>980</mn><mo>)</mo></math> is explored in the three-body <math><mi>D</mi></math> decays of <math><mi>D</mi><mo>→</mo><msub><mi>a</mi><mn>0</mn></msub><mo>(</mo><mn>980</mn><mo>)</mo><mi>P</mi><mo>→</mo><msub><mi>P</mi><mn>1</mn></msub><msub><mi>P</mi><mn>2</mn></msub><mi>P</mi></math> through the intermediate state <math><msub><mi>a</mi><mn>0</mn></msub><mo>(</mo><mn>980</mn><mo>)</mo></math>, where <math><mi>P</mi></math> denotes a pseudoscalar meson. The quasi-two-body <math><mi>D</mi><mo>→</mo><msub><mi>a</mi><mn>0</mn></msub><mo>(</mo><mn>980</mn><msup><mo>)</mo><mo>+</mo></msup><mi>P</mi></math> decays are governed by the external <math><mi>W</mi></math>-emission diagram in which <math><msub><mi>a</mi><mn>0</mn></msub><mo>(</mo><mn>980</mn><msup><mo>)</mo><mo>+</mo></msup></math> is emitted. The predicted branching fractions in the <math><mi>q</mi><mover><mi>q</mi><mo>¯</mo></mover></math> model of <math><msub><mi>a</mi><mn>0</mn></msub><mo>(</mo><mn>980</mn><mo>)</mo></math> are too small by one to two orders of magnitude compared to the experiment as the amplitude is suppressed by the smallness of the <math><msub><mi>a</mi><mn>0</mn></msub><mo>(</mo><mn>980</mn><msup><mo>)</mo><mo>+</mo></msup></math> decay constant, while those for <math><msup><mi>D</mi><mo>+</mo></msup><mo>→</mo><msub><mi>a</mi><mn>0</mn></msub><mo>(</mo><mn>980</mn><msup><mo>)</mo><mn>0</mn></msup><mi>P</mi></math> and <math><msup><mi>D</mi><mn>0</mn></msup><mo>→</mo><msub><mi>a</mi><mn>0</mn></msub><mo>(</mo><mn>980</mn><msup><mo>)</mo><mo>−</mo></msup><mi>P</mi></math> are usually too large. These discrepancies can be resolved, provided that <math><msub><mi>a</mi><mn>0</mn></msub><mo>(</mo><mn>980</mn><mo>)</mo></math> is a tetraquark state. In this case, there exist two additional <math><mi>T</mi></math>-like topological amplitudes, denoted by <math><mover><mi>T</mi><mo>¯</mo></mover></math> and <math><mover><mi>T</mi><mo>˜</mo></mover></math>, which readily account for the discrepancies. An important implication of the tetraquark model is that the <math><msubsup><mi>D</mi><mi>s</mi><mo>+</mo></msubsup><mo>→</mo><msub><mi>a</mi><mn>0</mn></msub><mo>(</mo><mn>980</mn><msup><mo>)</mo><mo>+</mo></msup><msup><mi>π</mi><mn>0</mn></msup><mo>+</mo><msub><mi>a</mi><mn>0</mn></msub><mo>(</mo><mn>980</mn><msup><mo>)</mo><mn>0</mn></msup><msup><mi>π</mi><mo>+</mo></msup></math> decay is not a purely <math><mi>W</mi></math>-annihilation process as in the <math><mi>q</mi><mover><mi>q</mi><mo>¯</mo></mover></math> model of <math><msub><mi>a</mi><mn>0</mn></msub><mo>(</mo><mn>980</mn><mo>)</mo></math>; it receives dominant contributions from <math><mover><mi>T</mi><mo>¯</mo></mover></math> newly noticed in this work. Therefore, measurements of <math><mo>(</mo><mi>D</mi><mo>,</mo><msubsup><mi>D</mi><mi>s</mi><mo>+</mo></msubsup><mo>)</mo><mo>→</mo><msub><mi>a</mi><mn>0</mn></msub><mo>(</mo><mn>980</mn><mo>)</mo><mi>P</mi></math> decays lend strong support to the tetraquark picture of <math><msub><mi>a</mi><mn>0</mn></msub><mo>(</mo><mn>980</mn><mo>)</mo></math>.

Hai-Yang Cheng

Fanrong Xu

Tetraquark nature of the <math><mrow><msub><mrow><mi>a</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>(</mo><mn>980</mn><mo>)</mo></mrow></math> meson in hadronic <math><mi>D</mi></math> decays

A scotogenic model can radiatively generate the observed neutrino mass, provide a dark matter candidate, and lead to rare lepton flavor-violating processes. We aim to extend the model to establish a potential connection to the quark flavor-related processes within the framework of scotogenesis, enhancing the unexpectedly large branching ratio (BR) of <math><mrow><msup><mrow><mi>B</mi></mrow><mrow><mo>+</mo></mrow></msup><mo>→</mo><msup><mrow><mi>K</mi></mrow><mrow><mo>+</mo></mrow></msup><mi>ν</mi><mover><mrow><mi>ν</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow></math> observed by the Belle II Collaboration. Meanwhile, the model can address tensions between some experimental measurements and standard model (SM) predictions in flavor physics, such as the muon <math><mi>g</mi><mo>−</mo><mn>2</mn></math> excess and the higher BR of <math><mrow><msub><mrow><mi>B</mi></mrow><mrow><mi>s</mi></mrow></msub><mo>→</mo><msup><mrow><mi>μ</mi></mrow><mrow><mo>−</mo></mrow></msup><msup><mrow><mi>μ</mi></mrow><mrow><mo>+</mo></mrow></msup></mrow></math>. In the model, we introduce the following dark particles: a neutral singlet Dirac-type lepton (<math><mi>N</mi></math>); two inert Higgs doublets (<math><msub><mi>η</mi><mrow><mn>1</mn><mo>,</mo><mn>2</mn></mrow></msub></math>), with one carrying a lepton number; a charged singlet dark scalar <math><mo>(</mo><msup><mi>χ</mi><mo>+</mo></msup><mo>)</mo></math>; and a singlet vectorlike up-type dark quark (<math><mi>T</mi></math>). The first two entities are responsible for the radiative neutrino mass, and <math><msup><mi>χ</mi><mo>+</mo></msup></math> couples to right-handed quarks and leptons and can resolve the tensions existing in muon <math><mi>g</mi><mo>−</mo><mn>2</mn></math> and <math><msub><mi>B</mi><mi>s</mi></msub><mo>→</mo><msup><mi>μ</mi><mo>−</mo></msup><msup><mi>μ</mi><mo>+</mo></msup></math>. Furthermore, the BR of <math><msup><mi>B</mi><mo>+</mo></msup><mo>→</mo><msup><mi>K</mi><mo>+</mo></msup><mi>ν</mi><mover><mi>ν</mi><mo>¯</mo></mover></math> can be enhanced up to a factor of 2 compared to the SM prediction through the mediations of the dark <math><mi>T</mi></math> and the charged scalars. In addition, we also study the impacts on the <math><mi>K</mi><mo>→</mo><mi>π</mi><mi>ν</mi><mover><mi>ν</mi><mo>¯</mo></mover></math> decays.

Rare <math><mi>B</mi></math> and <math><mi>K</mi></math> decays in a scotogenic model

The study of di-Higgs events, both resonant and non-resonant, plays a crucial role in understanding the fundamental interactions of the Higgs boson. In this work we consider di-Higgs events decaying into four b-quarks and propose to improve the experimental sensitivity by utilizing a novel machine learning algorithm known as Symmetry Preserving Attention Network (Spa-Net) — a neural network structure whose architecture is designed to incorporate the inherent symmetries in particle reconstruction tasks. We demonstrate that the Spa-Net can enhance the experimental reach over baseline methods such as the cut-based and the Dense Neural Network-based analyses. At the Large Hadron Collider, with a 14-TeV center-of-mass energy and an integrated luminosity of 300 fb−1, the Spa-Net allows us to establish 95% C.L. upper limits in resonant production cross-sections that are 10% to 45% stronger than baseline methods. For non-resonant di-Higgs production, Spa-Net enables us to constrain the self-coupling that is 9% more stringent than the baseline method.

Shih-Chieh Hsu

Ian Low

Deep learning to improve the sensitivity of Di-Higgs searches in the 4b channel

Many new physics models include secluded sectors that interact little with the Standard Model and whose internal interactions control the dark matter abundance. If these same interactions are responsible for maintaining kinematic equilibrium within the secluded sector, it is possible that the phase-space distributions will differ considerably from their thermal values during freeze-out. This can potentially result in deviations of the dark matter abundance from that computed under the assumption of thermal distributions. In this paper, we revisit dark matter abundance computations for a benchmark secluded sector by numerically tracking the phase-space distributions. Namely, we show that the dark matter abundance can deviate considerably from standard results during the freeze-out process, but that a longer period of annihilation ultimately leaves only a slight excess.

Impact of non-thermal phase-space distributions on dark matter abundance in secluded sectors