In a talk at an IHEP-Beijing symposium celebrating the 50th anniversary of the discovery of the <math altimg='si3.svg'><mrow><mi>J</mi><mo linebreak='goodbreak'>/</mo><mi>&#968;</mi></mrow></math>, I reminisced about some of the interesting phenomena that were observed in <math altimg='si3.svg'><mrow><mi>J</mi><mo linebreak='goodbreak'>/</mo><mi>&#968;</mi></mrow></math> decays in the BES, BESII, and BESIII detectors during the 35 year long BES experimental program. The three order of magnitude increase in the <math altimg='si3.svg'><mrow><mi>J</mi><mo linebreak='goodbreak'>/</mo><mi>&#968;</mi></mrow></math> event samples and the improved detector capabilities that occurred during this time led to a persistent series of interesting discoveries and new insights. As more <math altimg='si3.svg'><mrow><mi>J</mi><mo linebreak='goodbreak'>/</mo><mi>&#968;</mi></mrow></math> events were collected, the scientific interest in them increased and the breadth of physics topics that are addressed by them expanded. In addition, I speculated on what might happen if, in the next few decades, the magnitude of <math altimg='si3.svg'><mrow><mi>J</mi><mo linebreak='goodbreak'>/</mo><mi>&#968;</mi></mrow></math> data samples and the detector capabilities continued to increase at similar paces. In particular, I emphasize the possibilities of searches for <math altimg='si111.svg'><mi mathvariant='script'>C</mi></math> <math altimg='si112.svg'><mi mathvariant='script'>P</mi></math> violation in strange hyperon decays and testing the <math altimg='si111.svg'><mi mathvariant='script'>C</mi></math> <math altimg='si112.svg'><mi mathvariant='script'>P</mi></math> <math altimg='si113.svg'><mi mathvariant='script'>T</mi></math> theorem with strangeness-tagged neutral kaon decays.

China

South Korea

Stephen Lars Olsen

You never have enough <math altimg='si3.svg'><mrow><mi>J</mi><mo linebreak='goodbreak'>/</mo><mi>&#968;</mi></mrow></math> events - The case for a <math altimg='si3.svg'><mrow><mi>J</mi><mo linebreak='goodbreak'>/</mo><mi>&#968;</mi></mrow></math> factory

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

<p>Single Higgs production at FCC-ee probes the Higgs self-coupling at next-to-leading order (NLO). Extracting a bound requires a global analysis accounting for other possible new physics contributions up to NLO. We determine the FCC-ee sensitivity to Higgs self-coupling modifications <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>δ</mi><msub><mi>κ</mi><mi>λ</mi></msub></math> within the standard model effective field theory framework, including for the first time flavor, LEP, LHC, and FCC-ee observables in a global analysis with all leading NLO effects via one-loop renormalization group evolution, as well as incorporating finite NLO contributions to electroweak precision and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi><mi>H</mi></math> observables. The global sensitivity to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>δ</mi><msub><mi>κ</mi><mi>λ</mi></msub></math> is estimated by marginalizing over the effects of all other operators, bringing flavor considerations to the fore. We find that, under reasonable assumptions, FCC-ee sensitivity to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>δ</mi><msub><mi>κ</mi><mi>λ</mi></msub></math> can exceed that of the HL-LHC.</p>

Ben A. Stefanek

Higgs Self-Coupling at the Future Circular <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math> Collider

Linear Standard Model (SM) extensions, defined as new particles that can couple linearly to SM fields, form a motivated and finite set of simplified models for exploring phenomenology Beyond the SM (BSM). Heavy BSM particles may be integrated out to obtain their low-energy effects in the SM Effective Field Theory (SMEFT) parametrised by the Wilson coefficients of higher-dimensional operators. We compute and map the dimension-6 SMEFT operator structure of all scalar and fermion linear SM extensions up to one-loop order, thus extending the existing tree-level dictionary of results. Explicit analytic matching expressions for the Wilson coefficients are provided as both Python and Mathematica code in a GitHub repository accessible through links embedded in our main table for each coefficient and within a Python package. We apply our map to highlight the sensitivity to heavy new physics of a $\textit{Z}$-pole run at a future Tera-$\textit{Z}$ factory; at one loop, with unit couplings, all linear SM extensions can be indirectly probed by electroweak precision measurements up to $$ \mathcal{O}(10) $$ TeV.

Australia

John Gargalionis

France

Jérémie Quevillon

Germany

Pham Vuong

Linear Standard Model extensions in the SMEFT at one loop and Tera-$\textit{Z}$

Self-organised criticality, realised through cosmological dynamics in the early universe, is an alternative paradigm for addressing the electroweak hierarchy problem. In this scenario, an unnaturally light Higgs boson is the result of dynamics driving the electroweak vacuum towards a near-critical metastable point where the Higgs mass is bounded from above by the vacuum instability scale. To lower the vacuum instability scale close to the weak scale, previous realisations of this mechanism introduced new vector-like fermions coupled to the Higgs. Here we show that an Axion-Like Particle (ALP) coupling to the Higgs is an alternative possibility for achieving criticality with another well-motivated and naturally light candidate for new physics, thus leading to an entirely different set of testable phenomenological signatures. Our Axion-Higgs criticality model predicts an ALP in the MeV to $$ \mathcal{O} $$ (10) GeV range. The entire natural region of parameter space can be thoroughly explored by a combination of future colliders, flavour experiments, and cosmological observatories.

Maximilian Detering

Vacuum metastability from Axion-Higgs criticality

Heavy vector boson dark matter at the TeV scale or higher may be produced non-thermally in a first-order phase transition taking place at a lower energy scale. While the production of vector dark matter has previously been studied for bubble wall collisions, here we calculate production by bubble wall expansion in a plasma, which can be the dominant production mechanism. We compute the results numerically and provide an analytical fit for the vector dark matter density. The numerical fit is also validated for scalar dark matter production, obtaining results in agreement with past literature. We find that vector pair production leads to bubble wall friction with a novel boost factor scaling behaviour compared to transition radiation emission of a single vector. We conclude that TeV-scale WIMP vector dark matter can be efficiently produced non-thermally by first-order phase transitions in a wide region of parameter space where thermal freeze-out is inefficient. In this scenario, the phase transition scale is predicted to be in the sub-GeV to $$ \mathcal{O} $$ (10) TeV range and could therefore be accessible to future gravitational wave detectors.

Wen-Yuan Ai

Malcolm Fairbairn

Ken Mimasu

Non-thermal production of heavy vector dark matter from relativistic bubble walls

For the Laplacian of an n-Riemannian manifold X, the Weyl law states that the k-th eigenvalue is asymptotically proportional to (k/V)2/n , where V is the volume of X. We show that this result can be derived via physical considerations by demanding that the gravitational potential for a compactification on X behaves in the expected (4+n)-dimensional way at short distances. In simple product compactifications, when particle motion on X is ergodic, for large k the eigenfunctions oscillate around a constant, and the argument is relatively straightforward. The Weyl law thus allows to reconstruct the four-dimensional Planck mass from the asymptotics of the masses of the spin 2 Kaluza-Klein modes. For warped compactifications, a puzzle appears: the Weyl law still depends on the ordinary volume V, while the Planck mass famously depends on a weighted volume obtained as an integral of the warping function. We resolve this tension by arguing that in the ergodic case the eigenfunctions oscillate now around a power of the warping function rather than around a constant, a property that we call weighted quantum ergodicity. This has implications for the problem of gravity localization, which we discuss. We show that for spaces with Dp-brane singularities the spectrum is discrete only for p = 6, 7, 8, and for these cases we rigorously prove the Weyl law by applying modern techniques from RCD theory.

United States

G. Luca

Italy

Nicolò Ponti

Andrea Mondino

Alessandro Tomasiello

Can you hear the Planck mass?

Machine learning-based jet classifiers are able to achieve impressive tagging performance in a variety of applications in high-energy and nuclear physics. However, it remains unclear in many cases which aspects of jets give rise to this discriminating power, and whether jet observables that are tractable in perturbative QCD such as those obeying infrared-collinear (IRC) safety serve as sufficient inputs. In this article, we introduce a new classifier, Jet Flow Networks (JFNs), in an effort to address the question of whether IRC unsafe information provides additional discriminating power in jet classification. JFNs are permutation-invariant neural networks (deep sets) that take as input the kinematic information of reconstructed subjets. The subjet radius and a cut on the subjet’s transverse momenta serve as tunable hyperparameters enabling a controllable sensitivity to soft emissions and nonperturbative effects. We demonstrate the performance of JFNs for quark vs. gluon and Z vs. QCD jet tagging. For small subjet radii and transverse momentum cuts, the performance of JFNs is equivalent to the IRC-unsafe Particle Flow Networks (PFNs), demonstrating that infrared-collinear unsafe information is not necessary to achieve strong discrimination for both cases. As the subjet radius is increased, the performance of the JFNs remains essentially unchanged until physical thresholds that we identify are crossed. For relatively large subjet radii, we show that the JFNs may offer an increased model independence with a modest tradeoff in performance compared to classifiers that use the full particle information of the jet. These results shed new light on how machines learn patterns in high-energy physics data.

Dimitrios Athanasakos

Andrew Larkoski

James Mulligan

Mateusz Płoskoń

Felix Ringer

Is infrared-collinear safe information all you need for jet classification?

Axions and dark photons are common in many extensions of the Standard Model. The dark axion portal — an axion coupling to the dark photon and photon — can significantly modify their phenomenology. We study the cosmological constraints on the dark axion portal from Cosmic Microwave Background (CMB) bounds on the energy density of dark radiation, ∆N eff. By computing the axion-photon-dark photon collision terms and solving the Boltzmann equations including their effects, we find that light axions are generally more constrained by ∆N eff than from supernova cooling or collider experiments. However, with dark photons at the MeV scale, a window of parameter space is opened up above the supernova limits and below the experimental exclusion, allowing for axion decay constants as low as f  a  ~ 104 GeV. This region also modifies indirectly the neutrino energy density, thus relaxing the cosmological upper bound on the sum of neutrino masses. Future CMB measurements could detect a signal or close this open window on the dark axion portal.

Heejoung Hong

Ui Min

Minho Son

A cosmic window on the dark axion portal

We point out that an unnatural hierarchy between certain higher-dimensional operator coefficients in a low-energy effective field theory (EFT) would automatically imply that the Higgs’ vacuum expectation value is hierarchically smaller than the EFT cutoff, assuming the EFT emerged from a unitary, causal and local UV completion. Future colliders may have the sensitivity to infer such a pattern of coefficients for a little hierarchy with an EFT cutoff up to <math><mi>O</mi><mo>(</mo><mn>10</mn><mo>)</mo><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math>.

Switzerland

Joe Davighi

Scott Melville

Positivity and the electroweak hierarchy