Recently, the experimental values of the muon ( − 2) and of the boson mass have both indicated significant deviations from the SM predictions, motivating the exploration of extensions with extra particles and symmetries. We revisit a lepton portal model with U(1) gauge symmetry where an extra Higgs doublet, a scalar singlet and one SU(2) singlet vector-like fermion are introduced. In this model, ( − 2) can be explained by extra one-loop contributions from the vector-like lepton and the boson, whereas can be increased by a tree-level mixing between the and . Setting the and lepton couplings at low energies to account for the SM anomalies, we perform a Renormalization Group analysis to investigate on the high-energy behaviour of the model, in particular on the issue of vacuum stability. We find that in the alignment limit for the two Higgs doublets, the Landau pole and the scale where perturbativity is lost are of order 10 – 100 TeV, not far from the scales experimentally reached so far, and sensibly lower than the stability scale. We show how the Landau pole can be increased up to ~ 10 GeV in a misaligned scenario where the experimental anomalies are still accommodated and a positive shift of the Higgs quartic coupling to improve stability can be achieved.

South Korea

Italy

Carlo Branchina

Hyun Lee

Japan

Kimiko Yamashita

Standard Model anomalies and vacuum stability for lepton portals with extra U(1) symmetry

We introduce the spin-1 U(1) X  gauged field X with Z 2 odd dark parity to evade the current strong constraints on kinetic mixing. Then, X becomes stable and a candidate for the dark matter. The lowest mass dimension of interaction is six, and the type is the Higgs portal. Two types of dim-6 operators are introduced. We consider the freeze-out dark matter scenario. With the limit of null momentum transfer, a parity odd operator is free from the direct detection constraints. Accordingly, the strong constraints on a parity even operator indicate turning on this parity odd operator to realize the dark matter relic density of the Universe. With the 1 TeV cut-off scale, our dark matter of around 400 GeV mass can explain the dark matter relic density and is allowed from the LUX-ZEPLIN experiment of the direct detection.

Higgs-portal spin-1 dark matter with parity-violating interaction

We consider the relic density and positivity bounds for freeze-in scalar dark matter with general Higgs-portal interactions up to dimension-8 operators. When dimension-4 and dimension-6 Higgs-portal interactions are proportional to mass squares for Higgs or scalar dark matter in certain microscopic models such as massive graviton, radion or general metric couplings with conformal and disformal modes, we can take the dimension-8 derivative Higgs-portal interactions to be dominant for determining the relic density via the 2-to-2 thermal scattering of the Higgs fields after reheating. We discuss the implications of positivity bounds for microscopic models. First, massive graviton or radion mediates attractive forces between Higgs and scalar dark matter and the resultant dimension-8 operators respect the positivity bounds. Second, the disformal couplings in the general metric allow for the subluminal propagation of graviton but violate the positivity bounds. We show that there is a wide parameter space for explaining the correct relic density from the freeze-in mechanism and the positivity bounds can curb out the dimension-8 derivative Higgs-portal interactions nontrivially in the presence of the similar dimension-8 self-interactions for Higgs and dark matter.

Seong-Sik Kim

Positivity bounds on Higgs-portal freeze-in dark matter

We consider the positivity bounds for WIMP scalar dark matter with effective Higgs-portal couplings up to dimension-8 operators. Taking the superposed states for Standard Model Higgs and scalar dark matter, we show that the part of the parameter space for the effective couplings, otherwise unconstrained by phenomenological bounds, is ruled out by the positivity bounds on the dimension-8 derivative operators. We find that dark matter relic density, direct and indirect detection and LHC constraints are complementary to the positivity bounds in constraining the effective Higgs-portal couplings. In the effective theory obtained from massive graviton or radion, there appears a correlation between dimension-8 operators and other effective Higgs-portal couplings for which the strong constraint from direct detection can be evaded. Nailing down the parameter space mainly by relic density, direct detection and positivity bounds, we find that there are observable cosmic ray signals coming from the dark matter annihilations into a pair of Higgs bosons, WW or ZZ.

Positivity bounds on Higgs-Portal dark matter

Moments of the leptonic angular distribution in the Drell-Yan process have recently been shown to be sensitive probes of a specific class of dimension-8, four-fermion operators in the Standard Model Effective Field Theory, involving a pair of quarks and leptons. The same operators are also subject to positivity bounds, when requiring the associated (unknown) UV completion to obey basic principles of quantum field theory. We perform a phenomenological study to quantify the sensitivity of the high-luminosity LHC to this set of operators and, by extension, the positivity bounds. We further extend the angular basis of moments and consider double differential information to improve the ability to disentangle the different operators, leading to a sensitivity to new physics scales up to 3 TeV. We use this information to explore the violation of positivity at the LHC as a way to test the underlying principles of quantum field theory. Finally, we present a case study which combines our results with information from other (current and prospective) experiments, as well as the positivity cone to infer the properties of possible tree-level UV completions. The data lead to robust, model-independent lower bounds on the   <math> <mi>M</mi> <mo>/</mo> <msqrt> <mi>g</mi> </msqrt> </math>  $$ M/\sqrt{g} $$  combination of the particle mass and coupling, for states that couple to right-handed leptons and/or up quarks.

China

Xu Li

United Kingdom

Ken Mimasu

Chengjie Yang

Cen Zhang

Shuang-Yong Zhou

Moments for positivity: using Drell-Yan data to test positivity bounds and reverse-engineer new physics

We consider a simple extension of the Standard Model (SM) with a vector-like lepton and a local  $$U(1)'$$  <math> <mrow> <mi>U</mi> <msup> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> <mo>′</mo> </msup> </mrow> </math>   symmetry, motivated by the recent experimental anomalies in the muon  $$g-2$$  <math> <mrow> <mi>g</mi> <mo>-</mo> <mn>2</mn> </mrow> </math>   and the W boson mass. The  $$U(1)'$$  <math> <mrow> <mi>U</mi> <msup> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> <mo>′</mo> </msup> </mrow> </math>   symmetry is spontaneously broken by the VEVs of the dark Higgs scalar and the second Higgs doublet, giving rise to the mixing between the muon and the vector-like lepton. As a result, we obtain the desirable corrections to the muon  $$g-2$$  <math> <mrow> <mi>g</mi> <mo>-</mo> <mn>2</mn> </mrow> </math>   and the W boson mass simultaneously, dominantly due to the  $$Z'$$  <math> <msup> <mi>Z</mi> <mo>′</mo> </msup> </math>   gauge interactions for the vector-like lepton and the second Higgs doublet, respectively. We also discuss the consistency of the model with the Z boson decay width, the Higgs couplings and the dilepton bounds.

A model of vector-like leptons for the muon  $$g-2$$  <math> <mrow> <mi>g</mi> <mo>-</mo> <mn>2</mn> </mrow> </math>   and the W boson mass

We propose a novel model for lepton flavor and dark matter based on the <math><mi>S</mi><mi>U</mi><mo>(</mo><mn>2</mn><msub><mo>)</mo><mi>D</mi></msub></math> gauge symmetry and vectorlike leptons in its fundamental representations. We introduce a dark <math><mi>S</mi><mi>U</mi><mo>(</mo><mn>2</mn><msub><mo>)</mo><mi>D</mi></msub></math> Higgs doublet and a Higgs bidoublet for the mass mixing between the vectorlike lepton and the lepton. As a result, the seesaw lepton masses are generated and there are sizable one-loop contributions to the muon <math><mi>g</mi><mo>−</mo><mn>2</mn></math> via the <math><mi>S</mi><mi>U</mi><mo>(</mo><mn>2</mn><msub><mo>)</mo><mi>D</mi></msub></math> gauge bosons and the relatively heavy vectorlike lepton, as indicated in Fermilab E989. The tree-level mass mixing between the <math><mi>Z</mi></math> boson and the isospin-neutral gauge boson of <math><mi>S</mi><mi>U</mi><mo>(</mo><mn>2</mn><msub><mo>)</mo><mi>D</mi></msub></math> in our model accounts for the shift in the <math><mi>W</mi></math> boson mass, being consistent with Tevatron CDFII. Finally, we show that the isospin charged gauge boson of <math><mi>S</mi><mi>U</mi><mo>(</mo><mn>2</mn><msub><mo>)</mo><mi>D</mi></msub></math> becomes a plausible candidate for dark matter with a small mass splitting tied up to the modified <math><mi>W</mi></math> boson mass, and there is a viable parameter space where the favored corrections to the muon <math><mi>g</mi><mo>−</mo><mn>2</mn></math> and the <math><mi>W</mi></math> boson mass and the dark matter constraints are simultaneously fulfilled.

Hyun Min Lee

Adriana G. Menkara

<math><mi>S</mi><mi>U</mi><mo>(</mo><mn>2</mn><msub><mo>)</mo><mi>D</mi></msub></math> lepton portals for the muon <math><mi>g</mi><mo>−</mo><mn>2</mn></math>, <math><mi>W</mi></math>-boson mass, and dark matter

We study the post-inflationary dynamics for reheating and freeze-in dark matter in the Higgs-R 2 inflation model. Taking the perturbative approach for reheating, we determine the evolution of the temperature for radiation bath produced during reheating and determine the maximum and reheating temperatures of the Universe. Adopting a singlet scalar dark matter with a conformal non-minimal coupling and a vanishing Higgs-portal coupling, we discuss the freeze-in production of dark matter both from the non-thermal scattering during reheating and the thermal scattering after reheating. We find that thermal scattering is dominant for dark matter production in our model due to the high reheating temperature. The reheating temperature in our model is determined dominantly by the Higgs condensate to be up to about 1014 GeV and dark matter with masses up to about 109 GeV can be produced with a correct relic density.

Shuntaro Aoki

Adriana Menkara

Reheating and dark matter freeze-in in the Higgs-R 2 inflation model

We explore the phenomenology of a model of monopolium based on an electromagnetic dual formulation of Zwanziger and lattice gauge theory. The monopole is assumed to have a finite-sized inner structure based on a 't Hooft-Polyakov like solution, with the magnetic charge uniformly distributed on the surface of a sphere. The monopole and anti-monopole potential becomes linear plus Coulomb outside the sphere, analogous to the Cornell potential utilised in the study of quarkonium states. Discovery of a resonance feature in the diphoton channel as well as in a higher multiplicity photon channel would be a smoking gun for the existence of monopoles within this monopolium construction, with the mass and bound state properties extractable. Utilising the current LHC results in the diphoton channel, constraints on the monopole mass are determined for a wide range of model parameters. These are compared to the most recent MoEDAL results and found to be significantly more stringent in certain parameter regions, providing strong motivation for exploring higher multiplicity photon final state searches.

Neil D. Barrie

Akio Sugamoto

Poland

Matthew Talia

Searching for monopoles via monopolium multiphoton decays

The positivity bounds, derived from the axiomatic principles of quantum field theory (QFT), constrain the signs of Wilson coefficients and their linear combinations in the Standard Model Effective Field Theory (SMEFT). The precise determination of these bounds, however, can become increasingly difficult as more and more SM modes and oper- ators are taken into account. We study two approaches that aim at obtaining the full set of bounds for a given set of SM fields: 1) the traditional elastic positivity approach, which exploits the elastic scattering amplitudes of states with arbitrarily superposed helicities as well as other quantum numbers, and 2) the newly proposed extremal positivity approach, which constructs the allowed coefficient space directly by using the extremal representation of convex cones. Considering the electroweak gauge-bosons as an example, we demonstrate how the best analytical and numerical positivity bounds can be obtained in several ways. We further compare the constraining power and the efficiency of various approaches, as well as their applicability to more complex problems. While the new extremal approach is more constraining by construction, we also find that it is analytically easier to use, nu- merically much faster than the elastic approach, and much more applicable when more SM particle states and operators are taken into account. As a byproduct, we provide the best positivity bounds on the transversal quartic-gauge-boson couplings, required by the axiomatic principles of QFT, and show that they exclude ≈ 99.3% of the parameter space currently being searched at the LHC.