A precise determination of the CKM angle $\textit{γ}$ from $$ {B}_s^0 $$ oscillations in $$ {B}_s^0\to {D}_s^{\mp }{K}^{\pm } $$ decays offers a critical test of the Standard Model and probes for new physics. We present a comprehensive study on the prospects of measuring $\textit{γ}$ at a future Tera-$\textit{Z}$ factory, utilizing the baseline detector concept of the Circular Electron Positron Collider (CEPC). A two-dimensional simultaneous fit framework, incorporating flavor tagging, decay time resolution modeling, and acceptance corrections, is developed using full Monte Carlo simulations of $$ {B}_s^0\to {D}_s^{\mp}\left(\to {K}^{\mp }{K}^{\pm }{\pi}^{\mp}\right){K}^{\pm } $$ decays and inclusive background processes. The effective flavor tagging power reaches 23.6%, while the decay time resolution is determined to be 26 fs. Projecting to full statistics of signal events across three dominant $$ {D}_s^{-} $$ decay channels, we estimate a statistical precision of $\textit{σ}$($\textit{γ}$) = 0$\textit{.}$69 , which corresponds to 4.1 Tera-$\textit{Z}$ boson equivalent data. This study has established the feasibility of sub-degree level $\textit{γ}$ measurements at a $\textit{Z}$ factory, highlighting its unique advantages in time-dependent $\textit{CP}$ violation studies through ultra-precise vertexing and background suppression capabilities.

China

Ji Peng

Mingrui Zhao

Xiaolin Wang

Manqi Ruan

Hengne Li

Shanzhen Chen

Prospect for measurement of $\textit{CP}$-violating observables in $$ {B}_s^0\to {D}_s^{\mp }{K}^{\pm } $$ decays at a future $\textit{Z}$ factory

The Circular Electron Positron Collider (CEPC) is a large-scale particle accelerator designed to collide electrons and positrons at high energies. One of its primary goals is to achieve high-precision measurements of the properties of the Higgs boson and is facilitated by the large number of Higgs bosons that are produced with significantly low contamination. The measurements of Higgs boson branching fractions into $b\overline{b} /c\overline{c} /gg$ and $\tau\overline{\tau} /WW^{*} /ZZ^{*} $ , where the $\textit{W}$ or $\textit{Z}$ bosons decay hadronically, are presented in the context of the CEPC experiment, assuming a scenario with 5600 fb$^{−1}$ of collision data at a center-of-mass energy of 240 GeV. In this study the Higgs bosons are produced in association with a $\textit{Z}$ boson, with the $\textit{Z}$ boson decaying into a pair of muons $(\mu^{+}\mu^{-})$ , which have high efficiency and resolution. To separate all decay channels simultaneously with high accuracy, the Particle Flow Network (PFN), a graph-based machine learning model, is considered. The precise classification provided by the PFN is employed in measuring the branching fractions using the migration matrix method, which accurately corrects for detector effects in each decay channel. The statistical uncertainty of the measured branching ratio is estimated to be 0.55% in the $H\to b\overline{b}$ final state and approximately 1.5% − 16% in the $H\to c\overline{c} /gg/\tau\overline{\tau}/WW^{*} /ZZ^{*} $ final states. In addition, the main sources of systematic uncertainties in the measurement of the branching fractions are discussed.

Xiaotian Ma

Zuofei Wu

Jinfei Wu

Yanping Huang

Gang Li

Fábio L. Alves

Shan Jin

Ligang Shao

Measurements of decay branching fractions of the Higgs boson to hadronic final states at the CEPC * Supported in part by the National Key R&D Program of China (2022YFE0116900) and the Basic Science Center Program (12188102) by National Natural Science Foundation of China

<p>The prospected sensitivity in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>α</mi><mi mathvariant="normal">S</mi></msub></math> determination using an event shape observable and ratio of energy correlators at future electron-positron colliders is presented. The study focuses on the collinear region which has suffered from large theoretical and hadronization uncertainty in the past. The ratio effectively reduces the impacts of the uncertainties. With the amount of data that future electron-positron colliders could produce in 1 minute (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>40</mn><mtext> </mtext><mtext> </mtext><msup><mrow><mi>pb</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math>), a 1–2% precision of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>α</mi><mi mathvariant="normal">S</mi></msub></math> could be reached depending on the hadronization uncertainty considered.</p>

Zhen Lin

Meng Xiao

Zhen Xu

Extracting <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>α</mi><mi>s</mi></mrow></math> at 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> Higgs factory with energy correlators

In this study, we employed the heavy quark expansion model with the kinetic scheme to evaluate   $ \alpha_S(m_c^2) $  , the strong coupling constant at the charm quark mass   $ \alpha_S(m_c^2) $  , using data on inclusive semileptonic decays of charmed mesons. Using the experimental values of the semileptonic decay widths of the   $ \alpha_S(m_c^2) $   and the   $ \alpha_S(m_c^2) $  , the value of   $ \alpha_S(m_c^2) $   was determined to be   $ \alpha_S(m_c^2) $  , where the first uncertainty is experimental and the second is systematic. This value of   $ \alpha_S(m_c^2) $   is in good agreement with the value of   $ \alpha_S(m_c^2) $   which calculated by running   $ \alpha_S(m_c^2) $   at the   $ \alpha_S(m_c^2) $   boson mass   $ \alpha_S(m_c^2) $   with the renormalization group evolution equation. In addition, the values of   $ \alpha_S(m_c^2) $   obtained individually from each of the   $ \alpha_S(m_c^2) $  ,   $ \alpha_S(m_c^2) $  , and   $ \alpha_S(m_c^2) $   mesons were consistent, as they were of the same origin.

United States

Xinchou Lou

Yuzhi Che

Jingbo Ye

Strong coupling from inclusive semileptonic decay of charmed mesons  

This study investigates the precision measurement of the CKM matrix element |V  cb | through semileptonic WW events at future Higgs factories, i.e., FCC-ee, ILC, C3, and CEPC. We use full detector simulation to generate the WW → ℓνcb signal events and various backgrounds at   <math> <msqrt> <mi>s</mi> </msqrt> </math>  $$ \sqrt{s} $$  = 240 GeV with unpolarized beams. The relative statistical uncertainties of |V  cb | are projected to be 0.91% for the muon channel and 1.2% for the electron channel, assuming a baseline integrated luminosity of 5 ab−1. The sensitivities at other Higgs factory scenarios are also projected. Possible contributors to systematic uncertainties are discussed, with the most prominent one being the systematics of flavor-tagging and mistagging rates. Combining with WW threshold runs, the relative systematic uncertainty can be further reduced.

Hao Liang

LingFeng Li

Yongfeng Zhu

Xiaoyan Shen

Measurement of CKM element |V  cb | from W boson decays at the future Higgs factories

The CP-violating phase  $$\phi _s$$  <math> <msub> <mi>ϕ</mi> <mi>s</mi> </msub> </math>  , the  $$B_{s}$$  <math> <msub> <mi>B</mi> <mi>s</mi> </msub> </math>   decay width ( $$\varGamma _s$$  <math> <msub> <mi>Γ</mi> <mi>s</mi> </msub> </math>  ), and the  $$B_{s}$$  <math> <msub> <mi>B</mi> <mi>s</mi> </msub> </math>   decay width difference ( $$\varDelta \varGamma _s$$  <math> <mrow> <mi>Δ</mi> <msub> <mi>Γ</mi> <mi>s</mi> </msub> </mrow> </math>  ) are sensitive probes to new physics and can constrain the heavy quark expansion theory. The potential for the measurement at future Z factories is studied in this manuscript. It is found that operating at Tera-Z mode, the expected precision can reach:  $$\sigma (\phi _s) = 4.6~\textrm{mrad}$$  <math> <mrow> <mi>σ</mi> <mo>(</mo> <msub> <mi>ϕ</mi> <mi>s</mi> </msub> <mo>)</mo> <mo>=</mo> <mn>4.6</mn> <mspace width="3.33333pt"></mspace> <mtext>mrad</mtext> </mrow> </math>  ,  $$\sigma (\varDelta \varGamma _s) = 2.4~\mathrm {ns^{-1}}$$  <math> <mrow> <mi>σ</mi> <mrow> <mo>(</mo> <mi>Δ</mi> <msub> <mi>Γ</mi> <mi>s</mi> </msub> <mo>)</mo> </mrow> <mo>=</mo> <mn>2.4</mn> <mspace width="3.33333pt"></mspace> <msup> <mi>ns</mi> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msup> </mrow> </math>   and  $$\sigma (\varGamma _s) = 0.72~\mathrm {ns^{-1}}$$  <math> <mrow> <mi>σ</mi> <mrow> <mo>(</mo> <msub> <mi>Γ</mi> <mi>s</mi> </msub> <mo>)</mo> </mrow> <mo>=</mo> <mn>0.72</mn> <mspace width="3.33333pt"></mspace> <msup> <mi>ns</mi> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msup> </mrow> </math>  . The precision of  $$\phi _s $$  <math> <msub> <mi>ϕ</mi> <mi>s</mi> </msub> </math>   is 40% larger than the expected precision with the LHCb experiment at HL-LHC. If operating at 10-Tera-Z mode, the precision of  $$\phi _s $$  <math> <msub> <mi>ϕ</mi> <mi>s</mi> </msub> </math>   can be measured at 45% of the precision obtained from the LHCb experiment at HL-LHC. However, the measurement of  $$\varGamma _s$$  <math> <msub> <mi>Γ</mi> <mi>s</mi> </msub> </math>   and  $$\varDelta \varGamma _s$$  <math> <mrow> <mi>Δ</mi> <msub> <mi>Γ</mi> <mi>s</mi> </msub> </mrow> </math>   cannot benefit from the excellent time resolution and tagging power of the future Z-factories. Only operating at 10-Tera-Z mode can the  $$\varGamma _s$$  <math> <msub> <mi>Γ</mi> <mi>s</mi> </msub> </math>   and  $$\varDelta \varGamma _s$$  <math> <mrow> <mi>Δ</mi> <msub> <mi>Γ</mi> <mi>s</mi> </msub> </mrow> </math>   reach an 18% larger precision than the precision expected to be obtained from LHCb at HL-LHC. The control of penguin contamination at the future Z-factories is also discussed.

Xiaomei Li

Denmark

Prospect for measurement of the CP-violating phase  $$\phi _s$$  <math> <msub> <mi>ϕ</mi> <mi>s</mi> </msub> </math>   in the  $$B_{s}\rightarrow J/\psi \phi $$  <math> <mrow> <msub> <mi>B</mi> <mi>s</mi> </msub> <mo>→</mo> <mi>J</mi> <mo>/</mo> <mi>ψ</mi> <mi>ϕ</mi> </mrow> </math>   channel at a future Z factory

Hanhua Cui

Yuexin Wang

Erratum to: Jet charge identification in the   <math> <msup> <mi>e</mi> <mo>+</mo> </msup> <msup> <mi>e</mi> <mo>−</mo> </msup> <mo>→</mo> <mi>Z</mi> <mo>→</mo> <mi>q</mi> <mover> <mi>q</mi> <mo>¯</mo> </mover> </math>  $$ {e}^{+}{e}^{-}\to Z\to q\overline{q} $$  process at Z pole

A correction to this paper has been published: https://doi.org/10.1007/JHEP05(2024)210

Erratum to: Jet charge identification in the e+e −  → Z →   <math> <mi>q</mi> <mover> <mi>q</mi> <mo>¯</mo> </mover> </math>  $$ \textrm{q}\overline{\textrm{q}} $$  process at Z pole

To enhance the scientific discovery power of high-energy collider experiments, we propose and realize the concept of jet-origin identification that categorizes jets into five quark species <math><mo>(</mo><mi>b</mi><mo>,</mo><mi>c</mi><mo>,</mo><mi>s</mi><mo>,</mo><mi>u</mi><mo>,</mo><mi>d</mi><mo>)</mo></math>, five antiquarks <math><mo>(</mo><mover><mi>b</mi><mo>¯</mo></mover><mo>,</mo><mover><mi>c</mi><mo>¯</mo></mover><mo>,</mo><mover><mi>s</mi><mo>¯</mo></mover><mo>,</mo><mover><mi>u</mi><mo>¯</mo></mover><mo>,</mo><mover><mi>d</mi><mo>¯</mo></mover><mo>)</mo></math>, and the gluon. Using state-of-the-art algorithms and simulated <math><mi>ν</mi><mover><mi>ν</mi><mo>¯</mo></mover><mi>H</mi><mo>,</mo><mi>H</mi><mo>→</mo><mi>j</mi><mi>j</mi></math> events at 240 GeV center-of-mass energy at the electron-positron Higgs factory, the jet-origin identification simultaneously reaches jet flavor tagging efficiencies ranging from 67% to 92% for bottom, charm, and strange quarks and jet charge flip rates of 7%–24% for all quark species. We apply the jet-origin identification to Higgs rare and exotic decay measurements at the nominal luminosity of the Circular Electron Positron Collider and conclude that the upper limits on the branching ratios of <math><mrow><mi>H</mi><mo>→</mo><mi>s</mi><mover><mrow><mi>s</mi></mrow><mrow><mo>¯</mo></mrow></mover><mo>,</mo><mi>u</mi><mover><mrow><mi>u</mi></mrow><mrow><mo>¯</mo></mrow></mover><mo>,</mo><mi>d</mi><mover><mrow><mi>d</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow></math> and <math><mi>H</mi><mo>→</mo><mi>s</mi><mi>b</mi><mo>,</mo><mi>d</mi><mi>b</mi><mo>,</mo><mi>u</mi><mi>c</mi><mo>,</mo><mi>d</mi><mi>s</mi></math> can be determined to <math><mn>2</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>4</mn></mrow></msup></math> to <math><mn>1</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>3</mn></mrow></msup></math> at 95% confidence level. The derived upper limit for <math><mi>H</mi><mo>→</mo><mi>s</mi><mover><mi>s</mi><mo>¯</mo></mover></math> decay is approximately 3 times the prediction of the standard model.

Chen Zhou

CERN

Huilin Qu

Jet-Origin Identification and Its Application at an Electron-Positron Higgs Factory

Accurate jet charge identification is essential for precise electroweak and flavor measurements at the high-energy frontier. We propose a novel method called the Leading Particle Jet Charge method (LPJC) to determine the jet charge based on information of the leading charged particle. Tested on Z →   <math> <mi>b</mi> <mover> <mi>b</mi> <mo>¯</mo> </mover> </math>  $$ b\overline{b} $$  and Z →   <math> <mi>c</mi> <mover> <mi>c</mi> <mo>¯</mo> </mover> </math>  $$ c\overline{c} $$  samples at center-of-mass energy of 91.2 GeV, the LPJC achieves an effective tagging power ϵ eff of 20%/9% for c/b jet, respectively. In combination with the Weighted Jet Charge method (WJC), we develop a Heavy Flavor Jet Charge method (HFJC), which achieves an effective tagging power ϵ eff of 39%/20% for c/b jet, respectively. This paper also discusses the dependencies between jet charge identification performance and the fragmentation process of heavy flavor jets, as well as critical detector performances.

Jet charge identification in the e+e− → Z →   <math> <mi>q</mi> <mover> <mi>q</mi> <mo>¯</mo> </mover> </math>  $$ \textrm{q}\overline{\textrm{q}} $$  process at Z pole