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.

Italy

Marco Ciuchini

Germany

Marco Fedele

Enrico Franco

United States

Ayan Paul

Luca Silvestrini

Mauro Valli

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

Revealing the Higgs pair production process is the next big challenge in high energy physics. In this work, we explore the use of interpretable machine learning and cooperative game theory for extraction of the trilinear Higgs self-coupling in Higgs pair production. In particular, we show how a topological decomposition of the gluon-gluon fusion Higgs pair production process can be used to simplify the machine learning analysis flow. Furthermore, we extend the analysis to include   <math> <mi>q</mi> <mover> <mi>q</mi> <mo>¯</mo> </mover> </math>  $$ q\overline{q} $$  → hh production, which is strongly suppressed in the Standard Model, to extract the trilinear Higgs coupling and to bound large deviations of the light-quark Yukawa couplings from the Standard Model values. The constraints on the rescaling of the trilinear Higgs self-coupling, κ  λ , and the rescaling of light-quark Yukawa couplings, κ  u  and κ  d , at HL-LHC (FCC-hh) from single parameter fits are:  <math> <mtable> <mtr> <mtd> <msub> <mi>κ</mi> <mi>λ</mi> </msub> <mo>=</mo> <mfenced> <mn>0.53</mn> <mn>1.7</mn> </mfenced> <mspace width="0.25em"></mspace> <mfenced> <mfenced> <mn>0.97</mn> <mn>1.03</mn> </mfenced> </mfenced> </mtd> </mtr> <mtr> <mtd> <msub> <mi>κ</mi> <mi>u</mi> </msub> <mo>=</mo> <mfenced> <mrow> <mo>−</mo> <mn>470</mn> </mrow> <mn>430</mn> </mfenced> <mspace width="0.25em"></mspace> <mfenced> <mfenced> <mrow> <mo>−</mo> <mn>58</mn> </mrow> <mn>55</mn> </mfenced> </mfenced> </mtd> </mtr> <mtr> <mtd> <msub> <mi>κ</mi> <mi>d</mi> </msub> <mo>=</mo> <mfenced> <mrow> <mo>−</mo> <mn>360</mn> </mrow> <mn>360</mn> </mfenced> <mspace width="0.25em"></mspace> <mfenced> <mfenced> <mrow> <mo>−</mo> <mn>26</mn> </mrow> <mn>28</mn> </mfenced> </mfenced> </mtd> </mtr> </mtable> </math>  $$ {\displaystyle \begin{array}{c}{\kappa}_{\lambda }=\left[0.53,1.7\right]\ \left(\left[0.97,1.03\right]\right)\\ {}{\kappa}_u=\left[-470,430\right]\ \left(\left[-58,55\right]\right)\\ {}{\kappa}_d=\left[-360,360\right]\ \left(\left[-26,28\right]\right)\end{array}} $$

Lina Alasfar

Ramona Gröber

Christophe Grojean

China

Zhuoni Qian

Machine learning the trilinear and light-quark Yukawa couplings from Higgs pair kinematic shapes

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

We study axion effective field theories (EFTs), with a focus on axion couplings to massive chiral gauge fields. We investigate the EFT interactions that participate in processes with an axion and two gauge bosons, and we show that, when massive chiral gauge fields are present, such interactions do not entirely originate from the usual anomalous EFT terms. We illustrate this both at the EFT level and by matching to UV-complete theories. In order to assess the consistency of the Peccei-Quinn (PQ) anomaly matching, it is useful to introduce an auxiliary, non-dynamical gauge field associated to the PQ symmetry. When applied to the case of the Standard Model (SM) electroweak sector, our results imply that anomaly-based sum rules between EFT interactions are violated when chiral matter is integrated out, which constitutes a smoking gun of the latter. As an illustration, we study a UV-complete chiral extension of the SM, containing an axion arising from an extended Higgs sector and heavy fermionic matter that obtains most of its mass by coupling to the Higgs doublets. We assess the viability of such a SM extension through electroweak precision tests, bounds on Higgs rates and direct searches for heavy charged matter. At energies below the mass of the new chiral fermions, the model matches onto an EFT where the electroweak gauge symmetry is non-linearly realised.

Quentin Bonnefoy

Luca Luzio

Alejo Rossia

The anomalous case of axion EFTs and massive chiral gauge fields

We study whether higher-dimensional operators in effective field theories, in particular in the Standard Model Effective Field Theory (SMEFT), can source gauge anomalies via the modification of the interactions involved in triangle diagrams. We find no evidence of such gauge anomalies at the level of dimension-6 operators that can therefore be chosen independently to each others without spoiling the consistency of SMEFT, at variance with recent claims. The underlying reason is that gauge-invariant combinations of Goldstone bosons and massive gauge fields are allowed to couple to matter currents which are not conserved. We show this in a toy model by computing the relevant triangle diagrams, as well as by working out Wess-Zumino terms in the bosonic EFT below all fermion masses. The same approach applies directly to the Standard Model both at the renormalisable level, providing a convenient and unusual way to check that the SM is anomaly free, as well as at the non-renormalisable level in SMEFT.

Comments on gauge anomalies at dimension-six in the Standard Model Effective Field Theory

The associated production of a   <math> <mi>b</mi> <mover> <mi>b</mi> <mo>¯</mo> </mover> </math>  $$ b\overline{b} $$  pair with a Higgs boson could provide an important probe to both the size and the phase of the bottom-quark Yukawa coupling, y  b . However, the signal is shrouded by several background processes including the irreducible Zh, Z →   <math> <mi>b</mi> <mover> <mi>b</mi> <mo>¯</mo> </mover> </math>  $$ b\overline{b} $$  background. We show that the analysis of kinematic shapes provides us with a concrete prescription for separating the y  b -sensitive production modes from both the irreducible and the QCD-QED backgrounds using the   <math> <mi>b</mi> <mover> <mi>b</mi> <mo>¯</mo> </mover> <mi>γγ</mi> </math>  $$ b\overline{b}\gamma \gamma $$  final state. We draw a page from game theory and use Shapley values to make Boosted Decision Trees interpretable in terms of kinematic measurables and provide physics insights into the variances in the kinematic shapes of the different channels that help us complete this feat. Adding interpretability to the machine learning algorithm opens up the black-box and allows us to cherry-pick only those kinematic variables that matter most in the analysis. We resurrect the hope of constraining the size and, possibly, the phase of y  b  using kinematic shape studies of   <math> <mi>b</mi> <mover> <mi>b</mi> <mo>¯</mo> </mover> <mi>h</mi> </math>  $$ b\overline{b}h $$  production with the full HL-LHC data and at FCC-hh.

Resurrecting   <math> <mi>b</mi> <mover> <mi>b</mi> <mo>¯</mo> </mover> <mi>h</mi> </math>  $$ b\overline{b}h $$  with kinematic shapes

We perform an analysis within the Standard Model of <math><msup><mi>B</mi><mrow><mn>0</mn><mo>,</mo><mo>+</mo></mrow></msup><mo>→</mo><msup><mi>K</mi><mrow><mo>*</mo><mn>0</mn><mo>,</mo><mo>+</mo></mrow></msup><msup><mi>μ</mi><mo>+</mo></msup><msup><mi>μ</mi><mo>−</mo></msup></math> decays in light of the recent measurements from the LHCb experiment, showing that new data strengthen the need for sizable hadronic contributions and correlations among them. We then extend our analysis to new physics via the Standard Model effective theory, and carry out a state-of-the-art fit of available <math><mi>b</mi><mo>→</mo><mi>s</mi><msup><mo>ℓ</mo><mo>+</mo></msup><msup><mo>ℓ</mo><mo>−</mo></msup></math> data, including possible hadronic contributions. We find the case of a fully left-handed operator standing out as the simplest scenario with a significance of almost <math><mn>6</mn><mi>σ</mi></math>.

Lessons from the <math><mrow><msup><mrow><mi>B</mi></mrow><mrow><mn>0</mn><mo>,</mo><mo>+</mo></mrow></msup><mo>→</mo><msup><mrow><mi>K</mi></mrow><mrow><mo>*</mo><mn>0</mn><mo>,</mo><mo>+</mo></mrow></msup><msup><mrow><mi>μ</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>μ</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math> angular analyses

The measurements carried out at LEP and SLC projected us into the precision era of electroweak physics. This has also been relevant in the theoretical interpretation of LHCb and Belle measurements of rare B semileptonic decays, paving the road for new physics with the inference of lepton universality violation in   <math> <msub> <mi>R</mi> <msup> <mi>K</mi> <mfenced> <mo>∗</mo> </mfenced> </msup> </msub> </math>  $$ {R}_{K^{\left(\ast \right)}} $$  ratios. The simplest explanation of these flavour anomalies — sizeable one-loop contributions respecting Minimal Flavour Violation — is currently disfavoured by electroweak precision data. In this work, we discuss how to completely relieve the present tension between electroweak constraints and one-loop minimal flavour violating solutions to   <math> <msub> <mi>R</mi> <msup> <mi>K</mi> <mfenced> <mo>∗</mo> </mfenced> </msup> </msub> </math>  $$ {R}_{K^{\left(\ast \right)}} $$ . We determine the correlations in the Standard Model Effective Field Theory that highlight the existence of such a possibility. Then, we consider minimal extensions of the Standard Model where our effective-field-theory picture can be realized. We discuss how these solutions to b → sℓℓ anomalies, respecting electroweak precision and without any new source of flavour violation, may point to the existence of a Z′ boson at around the TeV scale, within the discovery potential of LHC, or to leptoquark scenarios.

Aleksandr Azatov

United Kingdom

Jorge Blas

B anomalies under the lens of electroweak precision

LEP precision on electroweak measurements was sufficient not to hamper the extraction of Higgs couplings at the LHC. But the foreseen permille-level Higgs measure- ments at future lepton colliders might suffer from parametric electroweak uncertainties in the absence of a dedicated electroweak program. We perform a joint, complete and consis- tent effective-field-theory analysis of Higgs and electroweak processes. The full electroweak- sector dependence of the e + e  −  → WW production process is notably accounted for, us- ing statistically optimal observables. Up-to-date HL-LHC projections are combined with CEPC, FCC-ee, ILC and CLIC ones. For circular colliders, our results demonstrate the importance of a new Z -pole program for the robust extraction of Higgs couplings. At linear colliders, we show how exploiting multiple polarizations and centre-of-mass energies is crucial to mitigate contaminations from electroweak parameter uncertainties on the Higgs physics program. We also investigate the potential of alternative electroweak measurements to compensate for the lack of direct Z -pole run, considering for instance radiative return to these energies. Conversely, we find that Higgs measurements at linear colliders could improve our knowledge of the Z couplings to electrons.