Axion-like particles (ALPs) are well-motivated extensions of the Standard Model (SM) that appear in many new physics scenarios, with masses spanning a broad range. In this work, we systematically study the production and detection prospects of light ALPs at future lepton colliders, including electron-positron and multi-TeV muon colliders. At lepton colliders, light ALPs can be produced in association with a photon or a $\textit{Z}$ boson. For very light ALPs ($\textit{m}$ < 1 MeV), the ALPs are typically long-lived and escape detection, leading to a mono-$\textit{V}$ ($\textit{V}$ = $\textit{γ}$, $\textit{Z}$) signature. In the long-lived limit, we find that the mono-photon channel at the Tera-$\textit{Z}$ stage of future electron-positron colliders provides the strongest constraints on ALP couplings to SM gauge bosons, $\textit{g}$ , thanks to the high luminosity, low background, and resonant enhancement from on-shell $\textit{Z}$ bosons. At higher energies, the mono-photon cross section becomes nearly energy-independent, and the sensitivity is governed by luminosity and background. At multi-TeV muon colliders, the mono-$\textit{Z}$ channel can yield complementary constraints. For heavier ALPs ($\textit{m}$ > 100 MeV) that decay promptly, mono-$\textit{V}$ signatures are no longer valid. In this case, ALPs can be probed via non-resonant vector boson scattering (VBS) processes, where the ALP is exchanged off-shell, leading to kinematic deviations from SM expectations. We analyze constraints from both light-by-light scattering and electroweak VBS, the latter only accessible at TeV-scale colliders. While generally weaker, these constraints are robust and model-independent. Our combined analysis shows that mono-$\textit{V}$ and non-resonant VBS channels provide powerful and complementary probes of ALP-gauge boson interactions.

China

Shou-shan Bao

Belgium

Yang Ma

Yongcheng Wu

United States

Keping Xie

Hong Zhang

Light axion-like particles at future lepton colliders

A high-energy $\textit{μ}$ $\textit{μ}$ collider provides a wide variety of mechanisms for the production of new heavy particles. While the reach for such particles via the direct annihilation of $\textit{μ}$ $\textit{μ}$ will approach the center-of-mass energy of the collider, the partonic fusions from gauge bosons, quarks, and gluons, originating from the incoming muon beams will open new channels for single production and pair production of particles with different quantum numbers. We present the production rates for a wide variety of colored states including color-triplets, color-sextets, color-octets, leptoquarks, and leptogluons. We find that pair production from the direct annihilation of $\textit{μ}$ $\textit{μ}$ generally has a cross section of 0.1 – 1 fb once above the production threshold. On the other hand, pair production through the quark and gluon content of the muon leads to a cross section of roughly 10 fb at the same particle mass. We perform simple estimations of the mass reach for each particle and find that a 10 TeV muon collider can extend the reach for color-triplets beyond what is possible at the high luminosity run of the Large Hadron Collider. Leptoquarks and leptogluons, with sensitivity driven by single production, can also be probed to higher masses at a muon collider than what the Large Hadron Collider can reach. A final example where a muon collider has superior reach is for color-octet scalars and vectors. Together, these cases illustrate the point that a muon collider is a competitive machine for searching for colored heavy particles, thus strengthening the motivation for such lepton colliders in the energy frontier. Although our study is focused on a muon collider, our results are largely applicable to high-energy $\textit{e}$ $\textit{e}$ collisions as well.

Tao Han

Matthew Low

Tong Wu

Colorful particle production at high-energy muon colliders

<p>In this study, we investigate the impact of new Large Hadron Collider (LHC) inclusive jet and dijet measurements on parton distribution functions (PDFs) that describe the proton structure, with a particular focus on the gluon distribution at large momentum fraction, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>x</mi></math>, and the corresponding partonic luminosities. We assess constraints from these datasets using next-to-next-to-leading-order (NNLO) theoretical predictions, accounting for a range of uncertainties from scale dependence and numerical integration. From the scale choices available for the calculations, our analysis shows that the central predictions for inclusive jet production show a smaller scale dependence than dijet production. We examine the relative constraints on the gluon distribution provided by the inclusive jet and dijet distributions, and also explore the phenomenological implications for inclusive <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>H</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>t</mi><mover accent="true"><mi>t</mi><mo stretchy="false">¯</mo></mover></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>t</mi><mover accent="true"><mi>t</mi><mo stretchy="false">¯</mo></mover><mi>H</mi></math> production at the LHC at 14 TeV.</p>

Alim Ablat

Sayipjamal Dulat

Tie-Jiun Hou

Joey Huston

Pavel Nadolsky

Ibrahim Sitiwaldi

C.P. Yuan

Impact of LHC precision measurements of inclusive jet and dijet production on the CTEQ-TEA global PDF fit

We present a methodology to streamline implementation of massive-quark radiative contributions in calculations with a variable number of active partons in proton-proton collisions. The methodology introduces subtraction and residual heavy-quark parton distribution functions (PDFs) to implement calculations in the Aivazis–Collins–Olness–Tung (ACOT) factorization scheme and its simplified realization in various processes up to the next-to-the-next-to-leading order in the QCD coupling strength. Interpolation tables for bottom-quark subtraction and residual distributions for CT18 NLO and NNLO PDF ensembles are provided in the common LHAPDF6 format. A numerical calculation of <math><mi>Z</mi></math>-boson production with at least one <math><mi>b</mi></math> jet at the Large Hadron Collider beyond the lowest order in QCD is considered for illustration purposes.

Marco Guzzi

Laura Reina

Doreen Wackeroth

General mass variable flavor number scheme for <math><mi>Z</mi></math> boson production in association with a heavy quark at hadron colliders

Neutrino trident production of dilepton pairs is well recognized as a sensitive probe of both electroweak physics and physics beyond the Standard Model. Although a rare process, it could be significantly boosted by such new physics, and it also allows the electroweak theory to be tested in a new regime. We demonstrate that the forward neutrino physics program at the Large Hadron Collider offers a promising opportunity to measure for the first time, dimuon neutrino tridents with a statistical significance exceeding <math><mn>5</mn><mi>σ</mi></math>, improving on the previous claims at the <math><mo>∼</mo><mn>3</mn><mi>σ</mi></math> level by the CHARM-II and CCFR collaborations while accounting for additional backgrounds later identified by the NuTeV collaboration. We present predictions for various proposed experiments and outline a specific experimental strategy to identify the signal and mitigate backgrounds, based on “reverse tracking” dimuon pairs in the <math><mrow><mi>FASER</mi><mi>ν</mi><mn>2</mn></mrow></math> detector. We also discuss prospects for constraining beyond Standard Model contributions to neutrino trident rates at high energies.

Wolfgang Altmannshofer

Poland

Toni Mäkelä

United Kingdom

Subir Sarkar

Sebastian Trojanowski

Bei Zhou

Discovering neutrino tridents at the Large Hadron Collider

We study the capabilities of a muon collider, at 3 and 10 TeV center-of-mass energy, of probing the interactions of the Higgs boson with the muon. We consider all the possible processes involving the direct production of EW bosons (W, Z and H) with up to five particles in the final state. We study these processes both in the HEFT and SMEFT frameworks, assuming that the dominant BSM effects originate from the muon Yukawa sector. Our study shows that a Muon Collider has sensitivity beyond the high-luminosity LHC, especially as it does not rely on the Higgs-decay branching fraction to muons. A 10 TeV muon collider provides a unique sensitivity on muon and (multi-) Higgs interactions, significantly better than the 3 TeV option. Particularly, we find searches based purely on multi-Higgs production to be particularly effective in probing these couplings.

Italy

Eugenia Celada

Germany

Wolfgang Kilian

Nils Kreher

Fabio Maltoni

Davide Pagani

Jürgen Reuter

Tobias Striegl

Probing Higgs-muon interactions at a multi-TeV muon collider

We present a state-of-the-art prediction for cross sections of neutrino deep inelastic scattering (DIS) from nucleon at high neutrino energies, <math><mrow><msub><mrow><mi>E</mi></mrow><mrow><mi>ν</mi></mrow></msub></mrow></math>, up to 1000 EeV (<math><msup><mn>10</mn><mn>12</mn></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>). Our calculations are based on the latest CT18 NNLO parton distribution functions (PDFs) and their associated uncertainties. To make predictions for the highest energies, we extrapolate the PDFs to small <math><mi>x</mi></math> according to several procedures and assumptions, thus affecting the uncertainties at ultrahigh <math><msub><mi>E</mi><mi>ν</mi></msub></math>; we quantify the uncertainties corresponding to these choices. Similarly, we quantify the uncertainties introduced by the nuclear corrections that are required to evaluate neutrino-nuclear cross sections for the neutrino observatories. These results can be applied to currently running astrophysical neutrino observatories, such as IceCube and KM3NeT, as well as various future experiments that have been proposed.

Jun Gao

T. J. Hobbs

Daniel R. Stump

High-energy neutrino deep inelastic scattering cross sections

In this work, we complete our CT18qed study with the neutron’s photon parton distribution function (PDF), which is essential for the nucleus scattering phenomenology. Two methods, CT18lux and CT18qed, based on the LUXqed formalism and the DGLAP evolution, respectively, to determine the neutron’s photon PDF have been presented. Various low-Q 2 non-perturbative variations have been carefully examined, which are treated as additional uncertainties on top of those induced by quark and gluon PDFs. The impacts of the momentum sum rule as well as isospin symmetry violation have been explored and turned out to be negligible. A detailed comparison with other neutron’s photon PDF sets has been performed, which shows a great improvement in the precision and a reasonable uncertainty estimation. Finally, two phenomenological implications are demonstrated with photon-initiated processes: neutrino-nucleus W-boson production, which is important for the near-future TeV–PeV neutrino observations, and the axion-like particle production at a high-energy muon beam-dump experiment.

T. Hobbs

The photon content of the neutron

The impact of recent LHC top-quark pair production single differential cross section measurements at 13 TeV collision energy on the structure of the proton is explored. In particular, the impact of these high-precision data on the gluon and other parton distribution functions (PDFs) of the proton at intermediate and large partonic momentum fraction <math><mi>x</mi></math> is analyzed. This study extends the CT18 global analysis framework to include these new data. The interplay between top-quark pair and inclusive jet production as well as other processes at the LHC, is studied. In addition, a study of the impact of scale choice on the theory description of the new 13 TeV <math><mi>t</mi><mover><mi>t</mi><mo>¯</mo></mover></math> measurements is performed.

Exploring the impact of high-precision top-quark pair production data on the structure of the proton at the LHC