We present results from a global fit of Standard Model parameters and dimension-6 SMEFT Wilson coefficients that includes electroweak, Drell-Yan, Higgs-boson, top-quark, and flavour observables. Fits obtained by floating individual coefficients are also discussed. The leading-order scale dependence of the SMEFT Wilson coefficients is consistently included in the evolution from the UV scale to the electroweak scale and the low-energy scale of flavour observables. In defining the SMEFT set of active operators we consider both the U(3) and the U(2) flavour symmetric limits. All fits are obtained within the HEPfit framework and are based on the most recent experimental results and state-of-the-art theoretical predictions for all the observables considered.

Spain

Jorge Blas

United States

Angelica Goncalves

United Kingdom

Víctor Miralles

Laura Reina

Italy

Luca Silvestrini

Mauro Valli

Constraining new physics effective interactions via a global fit of electroweak, Drell-Yan, Higgs, top, and flavour observables

The coupling of the Higgs boson to first and second generation fermions has yet to be measured experimentally. There still could be very large deviations in these couplings, as the origin of flavor is completely unknown. Nevertheless, if Yukawa couplings are modified, especially for light generations, there are generically strong constraints from flavor-changing neutral currents (FCNCs). Therefore, it is imperative to understand whether there exists viable UV physics consistent with current data that motivates future Higgs coupling probes. In particular, the charm-quark Yukawa is the next quark coupling that could be measured at the LHC $\textit{if}$ it is a few times larger than the SM and compatible with flavor data. This is difficult to achieve in the context of standard ansatz such as Minimal Flavor Violation. In this paper we show that within the framework of Spontaneous Flavor Violation (SFV), using a Two Higgs Doublet Model as an example, the Higgs can be sufficiently charming that new LHC probes are relevant. In this charming region, we show that new Higgs states near the EW scale with large couplings to quarks are required, providing complementary observables or new constraints on the SM Yukawa couplings. The down-type SFV mechanism enabling the suppression of FCNCs also allows for independent modifications to the up-quark Yukawa coupling, which we explore in detail as well.

Artemis Giannakopoulou

Patrick Meade

How charming can the Higgs be?

We compare the quantum chromodynamics (QCD) axion phase-space distribution from unitarized next-to-leading order chiral perturbation theory with the one extracted from pion-scattering data. We derive a robust bound by confronting momentum-dependent Boltzmann equations against up-to-date observations of the cosmic microwave background, of the baryonic acoustic oscillations and of primordial abundances. These datasets imply <math><msub><mi>m</mi><mi>a</mi></msub><mo>≤</mo><mn>0.16</mn><mtext> </mtext><mtext> </mtext><mi>eV</mi></math> for the 95% credible interval, i.e., <math><mo>∼</mo><mn>30</mn><mo>%</mo></math> stronger bound than what previously found. We present forecasts using dedicated likelihoods for future cosmological surveys and the sphaleron rate from unquenched lattice QCD.

Federico Bianchini

Giovanni Grilli di Cortona

QCD axion: Some like it hot

In this work we present PRyMordial: A package dedicated to efficient computations of observables in the Early Universe with the focus on the cosmological era of Big Bang Nucleosynthesis (BBN). The code offers fast and precise evaluation of BBN light-element abundances together with the effective number of relativistic degrees of freedom, including non-instantaneous decoupling effects. PRyMordial is suitable for state-of-the-art analyses in the Standard Model as well as for general investigations into New Physics active during BBN. After reviewing the physics implemented in PRyMordial, we provide a short guide on how to use the code for applications in the Standard Model and beyond. The package is written in Python, but more advanced users can optionally take advantage of the open-source community for Julia. PRyMordial is publicly available on GitHub.

Anne-Katherine Burns

Tim Tait

PRyMordial: the first three minutes, within and beyond the standard model

The recent measurement of helium-4 from the near-infrared spectroscopy of extremely metal-poor galaxies by the Subaru Survey may point to a new puzzle in the early Universe. We exploit this new helium measurement together with the percent-level determination of primordial deuterium, to assess indications for a nonvanishing lepton asymmetry during the big bang nucleosynthesis era, paying particular attention to the role of uncertainties in the nuclear reaction network. A cutting-edge Bayesian analysis focused on the role of the newly measured extremely metal-poor galaxies, jointly with information from the cosmic microwave background, suggests the existence of a nonzero lepton asymmetry at around the <math><mn>2</mn><mi>σ</mi></math> level, providing a hint for cosmology beyond lambda cold dark matter. We discuss conditions for a large total lepton asymmetry to be consistently realized in the early Universe.

Tim M. P. Tait

Indications for a Nonzero Lepton Asymmetry from Extremely Metal-Poor Galaxies

The LHCb Collaboration has recently released a new study of <math><msup><mi>B</mi><mo>+</mo></msup><mo>→</mo><msup><mi>K</mi><mo>+</mo></msup><msup><mo>ℓ</mo><mo>+</mo></msup><msup><mo>ℓ</mo><mo>−</mo></msup></math> and <math><mi>B</mi><mo>→</mo><msup><mi>K</mi><mrow><mo>*</mo><mn>0</mn></mrow></msup><msup><mo>ℓ</mo><mo>+</mo></msup><msup><mo>ℓ</mo><mo>−</mo></msup></math> (<math><mo>ℓ</mo><mo>=</mo><mi>e</mi></math>, <math><mrow><mi>μ</mi></mrow></math>) decays, testing lepton universality with unprecedented accuracy using the whole Run 1 and 2 dataset. In addition, the CMS Collaboration has reported an improved analysis of the branching ratios <math><msub><mi>B</mi><mrow><mo>(</mo><mi>d</mi><mo>,</mo><mi>s</mi><mo>)</mo></mrow></msub><mo>→</mo><msup><mi>μ</mi><mo>+</mo></msup><msup><mi>μ</mi><mo>−</mo></msup></math>. While these measurements offer, per se, a powerful probe of new physics, global analyses of <math><mi>b</mi><mo>→</mo><mi>s</mi><msup><mo>ℓ</mo><mo>+</mo></msup><msup><mo>ℓ</mo><mo>−</mo></msup></math> transitions also rely on the assumptions about nonperturbative contributions to the decay matrix elements. In this work, we perform a global Bayesian analysis of new physics in (semi)leptonic rare <math><mi>B</mi></math> decays, paying attention to the role of charming penguins which are difficult to evaluate from first principles. We find data to be consistent with the Standard Model once rescattering from intermediate hadronic states is included. Consequently, we derive stringent bounds on lepton universality violation in <math><mo>|</mo><mi>Δ</mi><mi>B</mi><mo>|</mo><mo>=</mo><mo>|</mo><mi>Δ</mi><mi>S</mi><mo>|</mo><mo>=</mo><mn>1</mn></math> (semi)leptonic processes.

Marco Ciuchini

Germany

Marco Fedele

Enrico Franco

Ayan Paul

Constraints on lepton universality violation from rare <math><mi>B</mi></math> decays

The LHCb experiment has recently presented new results on Lepton Universality Violation (LUV) in  $$B \rightarrow K^{(*)} \ell ^+ \ell ^-$$  <math> <mrow> <mi>B</mi> <mo>→</mo> <msup> <mi>K</mi> <mrow> <mo>(</mo> <mrow></mrow> <mo>∗</mo> <mo>)</mo> </mrow> </msup> <msup> <mi>ℓ</mi> <mo>+</mo> </msup> <msup> <mi>ℓ</mi> <mo>-</mo> </msup> </mrow> </math>   decays involving  $$K_S$$  <math> <msub> <mi>K</mi> <mi>S</mi> </msub> </math>   in the final state, which strengthen the recent evidence of LUV obtained in  $$B^+ \rightarrow K^{+} \ell ^+ \ell ^-$$  <math> <mrow> <msup> <mi>B</mi> <mo>+</mo> </msup> <mo>→</mo> <msup> <mi>K</mi> <mo>+</mo> </msup> <msup> <mi>ℓ</mi> <mo>+</mo> </msup> <msup> <mi>ℓ</mi> <mo>-</mo> </msup> </mrow> </math>   decays and the previous measurements of  $$B \rightarrow K^{*0} \ell ^+ \ell ^-$$  <math> <mrow> <mi>B</mi> <mo>→</mo> <msup> <mi>K</mi> <mrow> <mrow></mrow> <mo>∗</mo> <mn>0</mn> </mrow> </msup> <msup> <mi>ℓ</mi> <mo>+</mo> </msup> <msup> <mi>ℓ</mi> <mo>-</mo> </msup> </mrow> </math>  . While LUV observables in the Standard Model are theoretically clean, their predictions in New Physics scenarios are sensitive to the details of the hadronic dynamics, and in particular of the charming penguin contribution. In this work, we show how a conservative treatment of hadronic uncertainties is crucial not only to assess the significance of deviations from the Standard Model but also to obtain a conservative picture of the New Physics responsible for LUV. Adopting a very general parameterization of charming penguins, we find that: (i) current data hint at a sizable  $$q^2$$  <math> <msup> <mi>q</mi> <mn>2</mn> </msup> </math>   and helicity dependence of charm loop amplitudes; (ii) conservative NP solutions to B anomalies favour a left-handed or an axial lepton coupling rather than a vector one.

Charming penguins and lepton universality violation in  $$\varvec{b \rightarrow s \ell ^+ \ell ^-}$$  <math> <mrow> <mi>b</mi> <mo>→</mo> <mi>s</mi> <msup> <mi>ℓ</mi> <mo>+</mo> </msup> <msup> <mi>ℓ</mi> <mo>-</mo> </msup> </mrow> </math>   decays

The new measurement of the <math><mi>W</mi></math>-boson mass from the CDF Collaboration shows a significant tension with the Standard Model prediction. We quantify this discrepancy within a state-of-the-art analysis of electroweak precision data and scrutinize the leading deformations of the Standard Model effective field theory arising at dimension six. We find evidence for a nonzero value of the <math><mi>T</mi></math> parameter, i.e., for a novel source of violation of custodial symmetry, pointing to physics beyond the Standard Model at the <math><mrow><mn>4.5</mn><mi>σ</mi></mrow></math> level. We contextualize the implications of our findings in light of other present anomalies in particle physics.

Violation of custodial symmetry from <math><mi>W</mi></math>-boson mass measurements

The gamma factory is a proposal to back-scatter laser photons off a beam of partially-stripped ions at the LHC, producing a beam of <math><mrow><mo>∼</mo><mn>10</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi></mrow></math> to 1 GeV photons with intensities of <math><msup><mn>10</mn><mn>16</mn></msup></math> to <math><mrow><msup><mrow><mn>10</mn></mrow><mrow><mn>18</mn></mrow></msup><mtext> </mtext><mtext> </mtext><msup><mrow><mi>s</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math>. This implies <math><mo>∼</mo><msup><mn>10</mn><mn>23</mn></msup></math> to <math><msup><mn>10</mn><mn>25</mn></msup></math> photons on target per year, many orders of magnitude greater than existing accelerator light sources and also far greater than all current and planned electron and proton fixed target experiments. We determine the gamma factory’s discovery potential through “dark Compton scattering,” <math><mi>γ</mi><mi>e</mi><mo>→</mo><mi>e</mi><mi>X</mi></math>, where <math><mi>X</mi></math> is a new, weakly-interacting particle. For dark photons and other new gauge bosons with masses in the 1 to 100 MeV range, the gamma factory has the potential to discover extremely weakly-interacting particles with just a few hours of data and will probe couplings as low as <math><mo>∼</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>9</mn></mrow></msup></math> with a year of running. The gamma factory therefore may probe couplings lower than all other terrestrial experiments and is highly complementary to astrophysical probes. We outline the requirements of an experiment to realize this potential and determine the sensitivity reach for various experimental configurations.

India

Sreemanti Chakraborti

Jonathan L. Feng

Japan

James K. Koga

Gamma factory searches for extremely weakly interacting particles

The flavour problem of the Standard Model can be addressed through the Froggatt-Nielsen (FN) mechanism. In this work, we develop an approach to the study of FN textures building a direct link between FN-charge assignments and the measured masses and mixing angles via unitary transformations in flavour space. We specifically focus on the quark sector to identify the most economic FN models able to provide a dynamical and natural understanding of the flavour puzzle. Remarkably, we find viable FN textures, involving charges under the horizontal symmetry that do not exceed one in absolute value (in units of the flavon charge). Within our approach, we also explore the degree of tuning of FN models in solving the flavour problem via a measure analogous to the Barbieri-Giudice one. We find that most of the solutions do not involve peculiar cancellations in flavour space.