Within the nonrelativistic QCD framework, we investigate the associated production of charmonia and bottomonia at the future super <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi></math>-factory and at CEPC and FCC-ee. The color-octet (CO) channels in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>γ</mi><mo>*</mo></msup><mo>/</mo><msup><mi>Z</mi><mn>0</mn></msup></math>-propagated processes are considered in addition to the color-singlet (CS) channels. We find that the contributions from the CO channels are substantial or even dominant for nearly all processes from the production threshold to the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>Z</mi><mn>0</mn></msup></math> pole region. However, estimates of the production rate are highly sensitive to long-distance matrix elements (LDMEs) selections, so different combinations of LDMEs produce markedly different production yields. For this reason, the study of charmonia-bottomonia production at the future super <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi></math>-factory can serve as a viable probe of the CO mechanism, and the comparison between the theoretical results and future experimental data may provide constraints on the CO matrix elements. In addition, we calculate the relativistic corrections to both the CS and CO channels, which decrease the cross sections significantly, yielding a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>K</mi></math> factor of approximately 0.5. The predicted event yields of (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi><mo>+</mo><mi mathvariant="normal">ϒ</mi><mo>,</mo><mi mathvariant="normal">ϒ</mi><mo>+</mo><msub><mi>η</mi><mi>c</mi></msub></math>) production, with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi><mo>,</mo><mi mathvariant="normal">ϒ</mi></math> reconstructed via lepton pairs and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>η</mi><mi>c</mi></msub></math> reconstructed via hadronic decays, are (2, 4) and (18, 35) at the CEPC (2-year) and FCC-ee (4-year), respectively.

China

Xiao-Peng Wang

Yi-Jie Li

Guang-Zhi Xu

Kui-Yong Liu

Associated production of charmonia and bottomonia with color-octet channels at the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi></math> factory, CEPC, and FCC-ee

We study the classical stability of a non-topological $$Z^\prime $$ string in the minimal 331 model, which arises from the maximal symmetry breaking pattern of an $$\textrm{SU}(6)$$ toy model. Two Higgs triplets are introduced according to the emergent global symmetries in the fermionic sector of the $$\textrm{SU}(6)$$ toy model, which will achieve the sequential symmetry breaking of $$\textrm{SU}(3)_c\otimes \textrm{SU}(3)_W \otimes \textrm{U}(1)_X\rightarrow \textrm{SU}(3)_c\otimes \textrm{SU}(2)_W \otimes \textrm{U}(1)_Y$$ . By analyzing small perturbations around the string background and solving the coupled Helmholtz equations numerically, we find that the string is stable only near the semilocal limit of $$\vartheta _S \approx \frac{\pi }{2}$$ , even when Higgs self-couplings are tuned to minimize instabilities. This suggests that such non-topological strings are unlikely to exist in unified theories based on $$\textrm{SU}(N>5)$$ Lie algebras.

Zhengyang Bian

Ning Chen

Mian Guo

Zhanpeng Hou

Haoyang Ji

Junyi Wei

Zhuo Zhang

The non-topological $$Z^{\prime }$$ string in the 331 model and its classical stability

We investigate CP violation in the process $\textit{H}$ → $\textit{W}$ $\textit{Z}$ within the framework of the two-Higgs-Doublet model (2HDM). Amplitudes are expressed transparently in terms of physical couplings. Our analysis qualitatively confirms recent results by Kanemura and Mura, for the interference between one-loop bosonic and fermionic amplitudes. Furthermore, we identify additional sources of CP violation arising from internal interference among the bosonic and also among the fermionic loop amplitudes. In the alignment limit, the asymmetry would vanish in the absence of fermionic loop contributions when the sum of the masses of the additional neutral scalars is higher than the mass of the $\textit{Z}$. Our results allow for generic Yukawa couplings, and cover both explicit and spontaneous CP violation. For inclusive $\textit{W}$ and $\textit{Z}$ decays, the CP violation will only manifest itself as a charge asymmetry.

Palestine

W. Khater

Norway

O. Ogreid

P. Osland

Portugal

M. Rebelo

CP violation in $\textit{H}$ $\textit{±}$ $\textit{→ W}$ $\textit{±}$ $\textit{Z}$: a physical approach for the 2HDM

The precise determination of the $\textit{W}$ boson mass, $$m_W$$ , is a cornerstone of electroweak precision tests and a critical input to global fits of the Standard Model (SM). While most existing measurements of $$m_W$$ are in agreement with SM predictions, the recent result from the CDF collaboration exhibits a significant deviation from the SM prediction but also exceeding $$4\sigma $$ from the global average of all other high precision measurements. This prompts renewed scrutiny of potential sources of systematic bias. In this study, we investigate the modeling of the $\textit{Z}$ boson background, which is particularly relevant in the muon decay channel of the $\textit{W}$ boson, where undetected muons can mimic missing transverse momentum. Using updated theoretical predictions and high-precision simulations, we construct reweighted templates to evaluate the impact of possible mismodeling in the $\textit{Z}$ background. Our analysis suggests that such effects can induce a shift in the extracted $$m_W$$ value of up to 8 MeV in the muon decay channel. While this shift is non-negligible and exceeds the originally quoted uncertainty from this source, it remains insufficient to explain the full discrepancy observed in the CDF measurement.

France

Maarten Boonekamp

Matthias Schott

Germany

Chen Wang

Modeling uncertainties on the Z boson background in the context of high precision W boson mass measurements

We present a reanalysis of archived data from the ALEPH experiment at LEP in the $$ Z\to q\overline{q} $$ final state. We apply modern jet flavour tagging techniques to improve the separation between the different hadronic decay channels of the Z boson, achieving up to one order of magnitude improvement in misidentification rate for b- and c-quark jets compared to the legacy algorithms used for the most recent ALEPH results, for the same identification efficiency. We also present the first implementation of strange quark jet tagging with LEP data, which allows for the selection of a $$ Z\to s\overline{s} $$ enriched event sample. These improvements in the flavour tagging performance are achieved by leveraging the lifetime, particle identification, and secondary vertex information, as well as modern classifiers based on a deep learning approach. We also demonstrate the calibration of the tagger in data using a tag-and-probe method, obtaining good data to simulation agreement for all quark flavours. These results pave the way for improved measurements of electroweak precision observables with LEP archived data, and can serve as a guidance for the development of detectors and algorithms for future electron-positron colliders.

Switzerland

Matteo Defranchis

Jacopo Fanini

Iran

Apranik Fatehi

Gerardo Ganis

United States

Taj Gillin

Loukas Gouskos

Luka Lambrecht

Michele Selvaggi

Birgit Stapf

Modern jet flavour tagging in hadronic Z decays with archived ALEPH data

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.

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>

We explore signatures of lepton number violation (LNV) from decays of the discovered Higgs (<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>Z</mi></math> bosons into a pair of right-handed neutrinos (RHNs). Due to the Majorana nature of RHNs, the final state can be the same-sign dilepton plus jets leading to two units of LNV. As a simple but plausible scenario, we investigate such a signal in models with a new <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>U</mi><mo stretchy="false">(</mo><mn>1</mn><msub><mo stretchy="false">)</mo><mi>X</mi></msub></math> gauge symmetry, which naturally introduces three RHNs for gauge anomaly cancellation and is spontaneously broken down by a vacuum expectation value of an isospin singlet scalar field (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ϕ</mi></math>). In this scenario, <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>Z</mi></math> boson can decay into a pair of RHNs via the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>h</mi><mtext>−</mtext><mi>ϕ</mi></mrow></math> mixing and the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>Z</mi><mtext>−</mtext><msup><mrow><mi>Z</mi></mrow><mrow><mo>′</mo></mrow></msup></mrow></math> mixing with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>Z</mi><mo>′</mo></msup></math> being a new massive gauge boson, respectively. Estimating the LNV signal and corresponding backgrounds for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mo>ℓ</mo><mo>±</mo></msup><msup><mo>ℓ</mo><mo>±</mo></msup><mn>4</mn><mi>j</mi></math> final states, we find bounds on the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>h</mi><mtext>−</mtext><mi>ϕ</mi></mrow></math> mixing and the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>Z</mi><mtext>−</mtext><msup><mrow><mi>Z</mi></mrow><mrow><mo>′</mo></mrow></msup></mrow></math> mixing as a function of a mass of RHNs at Higgs factories, e.g., at the High-Luminosity LHC with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>14</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math>, 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> colliders at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>250</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>, muon colliders at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>125</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>, as well as at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi></math> factories, e.g., CEPC and Future Circular Collider (FCC-ee) at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>91.2</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>. We also discuss limits on the scalar mixing at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>−</mo></msup><msup><mi>μ</mi><mo>+</mo></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>μ</mi><mo>+</mo></msup><msup><mi>μ</mi><mo>+</mo></msup></math> collisions (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>μ</mi><mi>TRISTAN</mi></math>) with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>346</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi><mo>/</mo><mn>775</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> and 2 TeV, respectively.

Japan

Arindam Das

Takaaki Nomura

Kei Yagyu

Lepton number violation from <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Higgs</mi><mo>/</mo><mi>Z</mi></math> decays into a pair of right-handed neutrinos

We develop a systematic classification of asymmetric <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi mathvariant="double-struck">Z</mi><mn>2</mn></msub></math> orbifold actions in Pati-Salam heterotic string vacua constructed in the free fermionic formulation. Starting from symmetric <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi mathvariant="double-struck">Z</mi><mn>2</mn></msub><mo>×</mo><msub><mi mathvariant="double-struck">Z</mi><mn>2</mn></msub></math> orbifold vacua with an <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi><mi>O</mi><mo stretchy="false">(</mo><mn>10</mn><mo stretchy="false">)</mo></math> grand unified theory (GUT), we allow the Pati-Salam breaking vector to act asymmetrically on the internal degrees of freedom. The asymmetric orbifold action freezes geometrical moduli while inducing doublet-triplet splitting in the untwisted sector. Notably, this doublet-triplet splitting operates for any asymmetric action, including pure asymmetric shifts that preserve all geometric moduli, and is therefore independent of moduli stabilization. Classifying the breaking vector according to its twist action, we find six inequivalent classes of geometric moduli spaces characterized by 12, 8, 4 or 0 real untwisted moduli. Through combining these asymmetric twists with all compatible asymmetric shifts, 24 inequivalent cases are identified and characterized by their residual moduli content and internal Narain lattice. For each case we construct representative basis sets admitting three chiral generations, providing the starting point for further classification within each class. We perform explicit GGSO (Generalized Gliozzi–Scherk–Olive) phase enumerations in representative model classes with 12, 8, 4 and 0 moduli, classify the resulting <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">N</mi><mo>=</mo><mn>1</mn></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">N</mi><mo>=</mo><mn>0</mn></math> vacua according to phenomenological criteria and identify exophobic, phenomenologically viable models. We compute the partition function and corresponding one-loop vacuum energy at the free fermionic point in moduli space for each phenomenologically viable model across the four classes. As the number of geometrical moduli decreases, the number of distinct partition functions for these vacua collapses to a small number, reflecting a pronounced degeneracy under GGSO phase variations.

Luke A. Detraux

Alon E. Faraggi

Benjamin Percival

Classification of Pati-Salam asymmetric <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi mathvariant="double-struck">Z</mi><mn>2</mn></msub><mo>×</mo><msub><mi mathvariant="double-struck">Z</mi><mn>2</mn></msub></math> heterotic string orbifolds

We study the sensitivity of the upcoming Electron-Ion Collider to purely electrophilic new physics in the GeV mass range. Within an effective field theory framework, we consider two different scenarios: an axionlike particle (ALP) and a new heavy neutral vector gauge boson <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>Z</mi><mo>′</mo></msup></math>; each couples to electrons only. We analyze electron-proton collisions at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>141</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> with an integrated luminosity of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>100</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math>, focusing primarily on the trielectron final state. Additionally, loop-induced ALP-photon couplings driven by photon final states are also explored. Incorporating realistic detector effects and systematic uncertainties, we obtain projected exclusion limits on the relevant cross sections and couplings. We find that the results from the Electron-Ion Collider can significantly extend the sensitivity to electrophilic axionlike particles and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>Z</mi><mo>′</mo></msup></math> bosons in regions of parameter space that remain weakly constrained by existing experiments.

India

Amit Adhikary

Dilip Kumar Ghosh

Sk Jeesun

Sourov Roy

ALP and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>Z</mi><mo>′</mo></msup></math> boson at the Electron-Ion Collider

The phenomenology of a charged Higgs present in a model with two Higgs SU(2) doublets and a <italic>Z</italic> <inf>3</inf> flavor symmetry is analyzed. It is shown that it is possible to generate an enhancement of its flavor changing coupling to c and b quarks and also to reproduce the ATLAS excess associated to the process <italic>H</italic> &#8239;&#177;&#8239;&#8239;&#8594;&#8239; <italic>bc</italic> for a charge Higgs mass of 130 GeV. Furthermore, by considering the possibility of a search at the future LHeC, the analysis suggests viability for its detection.

Mexico

Alfredo Aranda

J. Hernández-Sánchez

Andrea Montiel

R. Noriega-Papaqui

Charged Higgs decay to bottom and charm quarks from <italic>Z</italic> <inf>3</inf> - Flavored two Higgs doublet models