We analyze the Large Hadron Collider potential to study triple couplings of the electroweak gauge bosons using their boosted hadronic decays. Deviations from Standard Model predictions spoil cancelations present in the Standard Model leading to the growth of the electroweak diboson production cross section at high center-of-mass energies. In this kinematical limit, $\textit{W}$’s and $\textit{Z}$’s are highly boosted, and consequently, their hadronic decays give rise to fat jets. Here, we show that the study of boosted hadronically decaying $\textit{W}$ and $\textit{Z}$ leads to limits on triple gauge couplings that are comparable to the ones originating from the leptonic decay channels.

Brazil

O. Éboli

India

Tathagata Ghosh

Matheus Martines

Sujay Shil

Triple gauge coupling analysis using boosted $\textit{W}$’s and $\textit{Z}$’s

A Tera-$\textit{Z}$ factory, such as FCC-ee or CEPC, will have indirect sensitivity to heavy new physics up to the tens of TeV scale through higher-order loop contributions to precision measurements at the $\textit{Z}$ pole. These indirect quantum effects may provide complementary, or even better, sensitivity to potential deviations from the Standard Model that are typically thought to best be constrained at leading order at higher energies above the $\textit{Z}$ pole. We show in the SMEFT framework how accuracy complements energy for operators that modify the Higgs and gauge boson two- and three-point functions, leading to improved projected sensitivities for models such as the real singlet scalar, weakly interacting massive particles, and a custodial weak quadruplet. A thorough Tera-$\textit{Z}$ programme may thus anticipate aspects of physics runs at higher energies and provide a wider scope of quantum exploration of the TeV scale than had previously been appreciated.

United Kingdom

Victor Maura

Spain

Ben Stefanek

Tevong You

Accuracy complements energy: electroweak precision tests at Tera-Z

A future $ e^+e^- $ collider could run at the $\textit{Z}$-pole to perform important electroweak (EW) precision measurements, but such a run may not be viable for a future muon collider. However, this can be compensated for by measuring other EW processes utilizing the high energy and large luminosity of the muon collider. In this paper, we consider the measurements of the vector boson fusion processes of $ WW/WZ/W\gamma $ to a pair of fermions (along with a $ \nu_{\mu}\bar{\nu}_{\mu} $ or $ \nu_{\mu}\mu^+/\bar{\nu}_{\mu}\mu^- $ pair) at a high-energy muon collider and study their potential for probing EW observables. We consider two run scenarios for the muon collider with center-of-mass energies of 10 and 30 TeV, respectively, and focus on the processes involving $ f=b,c,\tau $ and the dimension-6 operators that directly modify the corresponding fermions coupling to the $ Z/W $ bosons. The invariant mass distribution of the $ f\bar{f} $ pair helps to separate the events from the $ Z/W $ and high-energy resonances, whereas the polar angle of the outing fermion provides additional information. Through a chi-squared analysis on the binned distributions and combining the information from the $\textit{WW}$ and $ WZ/W\gamma $ fusion processes, all relevant Wilson coefficients can be constrained simultaneously. The precision surpasses the current EW measurement constraints and is even competitive with future $ e^+e^- $ colliders. Our analysis can be included in a more complete framework that is required to fully determine the potential of muon colliders in EW precision measurements.

China

Hao-Qiao Li

Hai-Ning Yan

Jiayin Gu

Germany

Xiao-Ze Tan

Probing $\textit{Z}$/$\textit{W}$ pole physics at high-energy muon colliders via vector-boson-fusion processes * Supported by the National Natural Science Foundation of China (NSFC) (12035008, 12375091, 12347171), and the Innovation Program for Quantum Science and Technology (2024ZD0300101). Xiao-Ze Tan also acknowledges the support from Helmholtz – OCPC (Office of China Postdoctoral Council) Postdoctoral Fellowship Program

The neutrino floor, a theoretical sensitivity limit for dark matter (DM) direct detection, is being redefined as the boundary of a dynamic ''neutrino fog,'' where neutrino signals become inevitable, obscuring DM detection due to statistical and systematic uncertainties. This study provides the first site-specific analysis of the neutrino floor at China Jinping Underground Laboratory (CJPL), leveraging its unique geographic and environmental characteristics. We quantify how CJPL’s suppressed atmospheric neutrino flux (approximately 30% lower than that of Laboratori Nazionali del Gran Sasso (LNGS)) reshapes the neutrino floor, thereby enabling improved sensitivity to high-mass WIMPs (mass > 10 GeV). Using a gradient-based framework, we derive the CJPL’s neutrino floor and estimate the detection prospects for the PandaX-xT experiment. Our results demonstrate that a 500 tonne-year exposure with PandaX-xT could reach the floor, probing spin independent cross-sections down to $ \sigma_{n}\sim 3\times 10^{-49}\; {\rm{cm}}^2$ at a DM mass of 70 GeV/$\textit{c}$ $^{2}$.

Yingjie Fan

Xuewen Liu

Ning Zhou

Characterizing the CJPL’s site-specific neutrino floor as the neutrino fog boundary * Xuewen Liu is supported by the Project of Shandong Province Higher Educational Science and Technology Program (2022KJ271). Ning Zhou is supported by National Science Foundation of China (12325505)

<p>A theoretical framework based on a spontaneously broken <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>Z</mi><mn>4</mn></msub></math> symmetry is proposed to simultaneously explain neutrino mass generation via the inverse seesaw mechanism and dark matter (DM) production through a freeze-in scenario. This work extends the standard model with right-handed neutrinos <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>N</mi><mi>i</mi></msub></math>, additional fermions <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>χ</mi><mi>i</mi></msub></math>, and a complex scalar <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi></math>. An unbroken <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>Z</mi><mn>2</mn></msub></math> subgroup ensures the stability of the DM candidate, whose relic abundance is dominantly produced via decay and scattering processes involving heavy singlet fermions. Phenomenological analyses show that this relatively minimal construction accommodates the observed neutrino oscillation parameters, consistent with the latest global fit data. Furthermore, the model successfully reproduces the observed DM relic density within the parameter space relevant to neutrino phenomenology, establishing a connection between neutrino properties and DM production.</p>

Ziye Wang

Yakefu Reyimuaji

Nijiati Yalikun

<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>Z</mi></mrow><mrow><mn>4</mn></mrow></msub></mrow></math> symmetric inverse seesaw model for neutrino masses and FIMP dark matter

<p>We consider the production of a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi></math> boson decaying to leptons in association with a bottom-quark pair in hadronic collisions. For the first time, we compute predictions at next-to-next-to-leading order (NNLO) in QCD, and we combine them with the all-order radiative corrections from a parton-shower simulation (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>NNLO</mi><mo>+</mo><mi>PS</mi></mrow></math>). Our method represents the first approach to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>NNLO</mi><mo>+</mo><mi>PS</mi></mrow></math> event generation applicable to processes featuring a color singlet and a heavy-quark pair in the final state. The novel two-loop corrections are computed for massless bottom quarks, and the leading mass corrections are restored through a small-mass expansion. The calculation is carried out in the four-flavor scheme, and we find that the sizable NNLO QCD corrections lift the long-standing tension between lower-order predictions in four- and five-flavor schemes. Our predictions are compared to a CMS measurement for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi></math> boson plus <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi></math>-jet production, achieving an excellent description of the data.</p>

Switzerland

Javier Mazzitelli

Vasily Sotnikov

Marius Wiesemann

Next-to-next-to-leading order event generation for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi></math>-boson production in association with a bottom-quark pair

The Bestest Little Higgs Model (BLHM) has attracted increasing attention in recent years, mainly because it can explain the hierarchy problem without fine-tuning by introducing one-loop corrections to the Higgs boson mass through heavy top quark partners and heavy gauge bosons. In the context of this new model, we exhaustively investigated the impact of the BLHM parameters on the Higgs-strahlung production processes <math altimg='si84.svg'><mrow><msup><mi>&#956;</mi><mo>&#8722;</mo></msup><msup><mi>&#956;</mi><mo>+</mo></msup><mo>&#8594;</mo><msup><mi>Z</mi><mo>&#8242;</mo></msup><msub><mi>h</mi><mn>0</mn></msub></mrow></math> and <math altimg='si85.svg'><mrow><msup><mi>&#956;</mi><mo>&#8722;</mo></msup><msup><mi>&#956;</mi><mo>+</mo></msup><mo>&#8594;</mo><msup><mi>Z</mi><mo>&#8242;</mo></msup><msub><mi>H</mi><mn>0</mn></msub></mrow></math>, where <math altimg='si23.svg'><msup><mi>Z</mi><mo>&#8242;</mo></msup></math> and <math altimg='si22.svg'><msub><mi>H</mi><mn>0</mn></msub></math> represent a new heavy gauge boson and a new heavy Higgs boson, respectively. We consider the integrated luminosities of <math altimg='si86.svg'><mrow><msub><mi mathvariant='script'>L</mi><mtext>int</mtext></msub><mo linebreak='goodbreak'>=</mo><mn>2000</mn><mo>,</mo><mn>20000</mn></mrow></math> <math altimg='si87.svg'><mrow><mrow><mi mathvariant='normal'>f</mi></mrow><msup><mi>b</mi><mrow><mo>&#8722;</mo><mn>1</mn></mrow></msup></mrow></math> and the respective center-of-mass energies of <math altimg='si68.svg'><mrow><msqrt><mi>s</mi></msqrt><mo linebreak='goodbreak'>=</mo><mn>3000</mn><mo>,</mo><mn>10000</mn></mrow></math> GeV projected for a future muon collider to estimate the number of expected Higgs boson production events <math altimg='si88.svg'><msub><mi>h</mi><mn>0</mn></msub></math> or <math altimg='si22.svg'><msub><mi>H</mi><mn>0</mn></msub></math> in association with a new gauge boson <math altimg='si23.svg'><msup><mi>Z</mi><mo>&#8242;</mo></msup></math> at the muon collider. In addition, we derive and present the Feynman rules for scalars ( <math altimg='si89.svg'><mrow><msub><mi>h</mi><mn>0</mn></msub><mo>,</mo><msub><mi>H</mi><mn>0</mn></msub><mo>,</mo><msup><mi>&#981;</mi><mn>0</mn></msup><mo>,</mo><msup><mi>&#951;</mi><mn>0</mn></msup><mo>,</mo><mi>&#963;</mi><mo>,</mo><msup><mi>H</mi><mo>&#177;</mo></msup><mo>,</mo><msup><mi>&#981;</mi><mo>&#177;</mo></msup><mo>,</mo><msup><mi>&#951;</mi><mo>&#177;</mo></msup><mo>,</mo><msub><mi>A</mi><mn>0</mn></msub></mrow></math>) and include the self-interactions of Higgs bosons.

Mexico

A. Gutiérrez-Rodríguez

E. Cruz-Albaro

D. Espinosa-Gómez

T. Cisneros-Pérez

David A. Pérez-Carlos

New physics search with the new gauge boson <math altimg='si23.svg'><msup><mi>Z</mi><mo>&#8242;</mo></msup></math> of the bestest little Higgs model at the muon collider

In this work, we reconstruct the $\textit{H}$($\textit{z}$) based on observational Hubble data with Artificial Neural Network, then estimate the cosmological parameters and the Hubble constant. The training data we used are covariance matrix and mock $\textit{H}$($\textit{z}$), which are generated based on the real OHD data and Gaussian process. The use of the covariance matrix propagates the correlated uncertainties and improves training efficiency. Using the reconstructed H(z) data, we first determine the Hubble constant and compare it with CMB-based measurements. To constrain cosmological parameters, we sample on the reconstructed data and calculate the corresponding posterior distributions with Markov chain Monte Carlo. Through comprehensive statistical comparisons, we demonstrate that the parameter estimation using reconstructed samples achieves comparable statistical accuracy to the result derived from real OHD data.

Jie-feng Chen

Tong-Jie Zhang

Peng He

Tingting Zhang

Jie Zhang

Estimating cosmological parameters and reconstructing Hubble constant with artificial neural networks: a test with covariance matrix and mock H(z)

We consider extending the Standard Model by an anomaly-free and possibly flavour non-universal $\textit{U}$(1) gauge symmetry, whose breaking gives a $\textit{Z′}$ boson that does not affect electroweak precision observables at tree-level or via 1-loop renormalisation group (RG) running. Provided it does not also couple to electrons, such a $\textit{Z′}$ boson would be largely invisible to an electroweak precision machine like FCC-ee or CEPC (up to small finite 1-loop matching contributions that we quantify). We show that, while this class of $\textit{Z′}$ models can also evade tests of quark flavour violation, the constraint of anomaly-cancellation implies that valence quarks, muons, and taus are all charged under $\textit{U}$(1) , with the up quark charge being necessarily large. The conclusion holds even if one augments the SM by three right-handed neutrinos to try and absorb anomalies. This means such $\textit{Z′}$ bosons cannot simultaneously hide below the TeV scale from $\textit{pp}$ → $\textit{ℓℓ}$ Drell–Yan measurements at the LHC and, even if we entertain esoteric models in which the lepton charges are numerically very small, we cannot escape dijet searches at the LHC. For equitable quark and lepton charges, $\textit{pp}$ → $\textit{ℓℓ}$ already excludes such a $\textit{Z′}$ up to $\textit{M/g}$ ≳ 10 TeV, with a reach of 20 TeV expected by the end of the High-Luminosity LHC. The dijet bounds currently sit around 5 TeV, while sensitivity up to 10 TeV could be achieved at HL-LHC. We thus find an excellent complementarity between FCC-ee and HL-LHC in covering all anomaly-free $\textit{Z′}$ bosons up to several TeV.

Joe Davighi

In search of an invisible $\textit{Z′}$

Dark matter particles could be superheavy (mass $$M_X\gtrsim 10^9~$$ GeV) provided that their lifetime $$\tau _X$$ is extremely long, i.e. greater than $$\simeq 10^{22}~$$ yr. Such stringent constraints on $$\tau _X$$ are generally obtained by limiting the prompt emission of ultrahigh energy ( $$\gtrsim 10^9~$$ GeV) gamma rays and neutrinos from the decay processes to below the corresponding flux upper bounds. In this paper, we show that even more severe bounds can be obtained for $$M_X\gtrsim 10^{13}~$$ GeV from the synchrotron radiation of electron decay byproducts in the Galaxy. We illustrate the power of these constraints using generic Higgs-induced $$h\nu $$ and gauge-induced $$Z\nu /W\ell $$ decay channels, motivated by particle-physics setups invoking right-handed neutrinos. As a concrete benchmark, we consider a superheavy dark-matter candidate within an extended type-I seesaw framework and show that the lower bounds on lifetime can be translated into upper bounds on a mass-mixing parameter $$\delta M$$ , which must satisfy approximately $$\delta M\lesssim 2\times 10^{-17}/[M_X/(10^9~\textrm{GeV})]^{0.5}$$ GeV for $$M_X\gtrsim 10^9$$ GeV. Some implications in the context of inflationary cosmologies are discussed.

France

Olivier Deligny

Constraints on superheavy dark matter decaying into $$h\nu $$ , $$Z\nu $$ and $$W\ell $$