We perform a global analysis of Drell–Yan production of charged leptons and dineutrinos, the latter in missing energy plus jet events, in proton–proton collisions within the Standard Model Effective Field Theory (SMEFT). The combination allows for the removal of flat directions, sharper limits and to probe more couplings than the individual observables, which we show performing a fit to LHC-data. We also find that limits have only mild dependence on lepton flavor patterns; hierarchies in quark flavors are driven by the parton distribution functions. The strongest constraints are on couplings involving the first and second generation quarks, exceeding 10 TeV. Combining flavor and high- $$p_T$$ data, the limits on electroweak and gluon dipole operators can be improved, by up to a factor of three, highlighting once more that a more global approach increases sensitivities significantly. We also estimate the improvements in reach over existing data for the high-luminosity LHC (HL-LHC) by $$\sim 1.5$$ , and future collider options such as the high-energy LHC (HE-LHC) by $$\sim 3$$ and FCC-hh by $$\sim 8$$ . To maximize the new physics reach kinematic cuts and binning needs to be adjusted to each quark-flavor separately.

Germany

Gudrun Hiller

Lara Nollen

Daniel Wendler

Total Drell–Yan in the flavorful SMEFT

We perform a global analysis of |∆c| = |∆u| = 1 transitions using recent data on D 0 → μ + μ  − , D + → π + μ + μ  − , Λ c  → p μ + μ  − , and D 0 → π + π  −  μ + μ  −  decays, and work out constraints on new physics Wilson coefficients   <math> <msubsup> <mi>C</mi> <mrow> <mn>7</mn> <mo>,</mo> <mn>9</mn> <mo>,</mo> <mn>10</mn> </mrow> <mfenced> <mo>′</mo> </mfenced> </msubsup> </math>  $$ {C}_{7,9,10}^{\left(\prime \right)} $$ . While results are consistent with the standard model, we find sizeable room for new physics that can be cleanly signaled with null test observables, not probed with searches in other sectors such as kaon and b-decays. The decay D 0 → π + π  −  μ + μ  −  requires better understanding of hadronic contributions to be competitive in the current fit. Progress can be achieved by precision study of the double differential decay rate in the dipion and dimuon masses, together with improved theory modelling and D → ππ transition form factors. On the other hand, the 4-body decay is an important contributor to the future global analysis due to its angular distributions that probe complementary combinations of Wilson coefficients, and as a QCD laboratory. The decay Λ c  → pℓ + ℓ  −  is the rising star due to the simplicity of a 3-body decay with available form factors from lattice QCD, sensitivity to both 4-fermion and electromagnetic dipole couplings and its null test forward-backward asymmetry.

Italy

Spain

Hector Gisbert

Dominik Suelmann

Effective field theory analysis of rare |∆c| = |∆u| = 1 charm decays

We revisit the stability of the Standard Model vacuum and investigate its quantum effective potential using the highest available orders in perturbation theory and the most accurate determination of input parameters to date. We observe that the stability of the electroweak vacuum centrally depends on the values of the top mass and the strong coupling constant. We estimate that reducing their uncertainties by a factor of 2–3 is sufficient to establish or refute Standard Model vacuum stability at the <math><mn>5</mn><mi>σ</mi></math> level. We further investigate vacuum stability for a variety of singlet scalar field extensions with and without flavor using the Higgs portal mechanism. We identify the beyond Standard Model parameter spaces for stability and find sizable room for new physics. We further study the phenomenology of Planck-safe models at colliders and determine the impact on the Higgs trilinear, the Higgs-to-electroweak-boson, and the Higgs quartic couplings, some of which can be significant. The former two can be probed at the HL-LHC; the latter requires a future collider with sufficient energy and precision such as the FCC-hh.

United Kingdom

Tim Höhne

Daniel F. Litim

Tom Steudtner

Vacuum stability in the Standard Model and beyond

We study the production of dineutrinos in proton-proton collisions, with large missing transverse energy and an energetic jet as the experimental signature. Recasting a search from the ATLAS collaboration we work out constraints on semileptonic four-fermion operators, gluon and electroweak dipole operators and Z-penguins in the SMEFT. All but the Z-penguin operators experience energy-enhancement. Constraints on gluon dipole operators are the strongest, probing new physics up to 14 TeV, and improve over existing ones from collider studies. Limits on FCNC four-fermion operators are competitive with Drell-Yan production of dileptons, and improve on those for tau final states. For left-handed |∆s| = |∆d| = 1 and right-handed |∆c| = |∆u| = 1 transitions these are the best available limits, also considering rare kaon and charm decays. We estimate improvements for the 3000 fb−1 High Luminosity Large Hadron Collider.

Missing energy plus jet in the SMEFT

Rare decays mediated by <math><mi>b</mi><mo>→</mo><mi>s</mi><mi>ν</mi><mover><mi>ν</mi><mo>¯</mo></mover></math> transitions have been reported by the Belle II experiment. The branching ratio of the decay <math><msup><mi>B</mi><mo>+</mo></msup><mo>→</mo><msup><mi>K</mi><mo>+</mo></msup><mi>ν</mi><mover><mi>ν</mi><mo>¯</mo></mover></math> is found to be enhanced with respect to the standard model value. If taken at face value, the implications are profound; either lepton flavor universality is violated at the (multi)-TeV-scale, or light new physics is involved. This holds in general if <math><mi>B</mi><mo>(</mo><msup><mi>B</mi><mo>+</mo></msup><mo>→</mo><msup><mi>K</mi><mo>+</mo></msup><mi>ν</mi><mover><mi>ν</mi><mo>¯</mo></mover><mo>)</mo></math> exceeds <math><mn>1.2</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>5</mn></mrow></msup><mo>(</mo><mn>1.3</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>5</mn></mrow></msup><mo>)</mo></math> at <math><mn>1</mn><mi>σ</mi></math> (<math><mn>2</mn><mi>σ</mi></math>), which tightens with a decreasing upper limit on <math><mi>B</mi><mo>(</mo><mi>B</mi><mo>→</mo><msup><mi>K</mi><mo>*</mo></msup><mi>ν</mi><mover><mi>ν</mi><mo>¯</mo></mover><mo>)</mo></math>, that is in reach of the Belle II experiment. In view of the strong constraints on electron-muon 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> processes, viable explanations are heavy, (5–10)-TeV tree-level new physics mediators that couple only to tau-flavors, or lepton flavor violating ones. In addition, couplings of similar size to both left- and right-handed quarks are generically required, implying nonminimal beyond the standard model sectors which are carefully balanced against flavor constraints. The decay <math><msubsup><mi>B</mi><mi>s</mi><mn>0</mn></msubsup><mo>→</mo><mtext>invisibles</mtext></math> can shed light on whether new physics is light or heavy. In the former case, branching ratios can be as large as <math><msup><mn>10</mn><mrow><mo>−</mo><mn>5</mn></mrow></msup></math>.

Rigo Bause

Implications of an enhanced <math><mrow><mi>B</mi><mo>→</mo><mi>K</mi><mi>ν</mi><mover><mrow><mi>ν</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow></math> branching ratio

We perform a global analysis of Beauty, Top, Z and Drell-Yan measurements in the framework of the Standard Model effective theory (SMEFT). We work within the minimal flavor violation (MFV) hypothesis, which relates different sectors and generations beyond the SU(2) L -link between left-handed top and beauty quarks. We find that the constraints on the SMEFT Wilson coefficients from the combined analysis are stronger than the constraints from a fit to the individual sectors, highlighting synergies in the global approach. We also show that constraints within MFV are strengthened compared to single-generation fits. The strongest bounds are obtained for the semileptonic four-fermion triplet operator   <math> <msubsup> <mi>C</mi> <mi>lq</mi> <mfenced> <mn>3</mn> </mfenced> </msubsup> </math>  $$ {C}_{lq}^{(3)} $$ , probing scales as high as 18 TeV, followed by the gluon dipole operator C  uG  with 7 TeV, and other four-fermion and penguin operators in the multi-TeV range. Operators with left-handed quark bilinears receive order one contributions from higher orders in the MFV expansion induced by the top Yukawa coupling as a result of the FCNC b → sμμ anomalies combined with the other sectors. We predict the 68% credible intervals of the dineutrino branching ratios within MFV as   <math> <mn>4.25</mn> <mo>⋅</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>6</mn> </mrow> </msup> <mo>≤</mo> <mi>B</mi> <mfenced> <mrow> <msup> <mi>B</mi> <mn>0</mn> </msup> <mo>→</mo> <msup> <mi>K</mi> <mrow> <mo>∗</mo> <mn>0</mn> </mrow> </msup> <mi>ν</mi> <mover> <mi>ν</mi> <mo>¯</mo> </mover> </mrow> </mfenced> <mo>≤</mo> <mn>11.13</mn> <mo>⋅</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>6</mn> </mrow> </msup> </math>  $$ 4.25\cdot {10}^{-6}\le \mathcal{B}\left({B}^0\to {K}^{\ast 0}\nu \overline{\nu}\right)\le 11.13\cdot {10}^{-6} $$  and   <math> <mn>2.26</mn> <mo>⋅</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>6</mn> </mrow> </msup> <mo>≤</mo> <mi>B</mi> <mfenced> <mrow> <msup> <mi>B</mi> <mo>+</mo> </msup> <mo>→</mo> <msup> <mi>K</mi> <mo>+</mo> </msup> <mi>ν</mi> <mover> <mi>ν</mi> <mo>¯</mo> </mover> </mrow> </mfenced> <mo>≤</mo> <mn>5.78</mn> <mo>⋅</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>6</mn> </mrow> </msup> </math>  $$ 2.26\cdot {10}^{-6}\le \mathcal{B}\left({B}^{+}\to {K}^{+}\nu \overline{\nu}\right)\le 5.78\cdot {10}^{-6} $$ , which include the respective Standard Model predictions, and are in reach of the Belle II experiment. We show how future measurements of the dineutrino branching ratios can provide insights into the structure of new physics in the global fit.

Cornelius Grunwald

Kevin Kröninger

More synergies from beauty, top, Z and Drell-Yan measurements in SMEFT

The recent measurement of the <math><mi>C</mi><mi>P</mi></math> asymmetry in the decay <math><mi>D</mi><mo>→</mo><msup><mi>K</mi><mo>+</mo></msup><msup><mi>K</mi><mo>−</mo></msup></math> by LHCb, combined with <math><mi>Δ</mi><msub><mi>A</mi><mrow><mi>C</mi><mi>P</mi></mrow></msub></math>, evidences a sizable <math><mi>C</mi><mi>P</mi></math> asymmetry in the decay <math><mi>D</mi><mo>→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup></math>, which requires a dynamical enhancement of standard model higher-order contributions over tree-level ones by a factor of 2. The data furthermore imply huge <math><mi>U</mi></math>-spin breaking, about 4–5 times larger than the nominal standard model one of <math><mo>≲</mo><mn>30</mn><mo>%</mo></math> in charm. Enhanced breakdown of the two approximate symmetries points to models that violate <math><mi>U</mi></math>-spin and <math><mi>C</mi><mi>P</mi></math> and disfavors flavor singlet contributions such as chromomagnetic dipole operators as explanations of the data. We analyze the reach of flavorful <math><msup><mi>Z</mi><mo>′</mo></msup></math> models for charm <math><mi>C</mi><mi>P</mi></math> asymmetries. Models generically feature explicit <math><mi>U</mi></math>-spin and isospin breaking, allowing for correlations with <math><mi>D</mi><mo>→</mo><msup><mi>π</mi><mn>0</mn></msup><msup><mi>π</mi><mn>0</mn></msup></math> and <math><msup><mi>D</mi><mo>+</mo></msup><mo>→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mn>0</mn></msup></math> decays with corresponding <math><mi>C</mi><mi>P</mi></math> asymmetries at similar level and sign as <math><mi>D</mi><mo>→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup></math>, about <math><mi>O</mi><mo>(</mo><mn>1</mn><mo>−</mo><mn>2</mn><mo>)</mo><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>3</mn></mrow></msup></math>. Experimental and theoretical constraints very much narrow down the shape of viable models: Viable, anomaly-free models are leptophobic—or at least electron- and muophobic—with light <math><msup><mi>Z</mi><mo>′</mo></msup></math> below <math><mi>O</mi><mo>(</mo><mn>20</mn><mo>)</mo><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> and can be searched for in low mass dijets at the LHC or in <math><mi>ϒ</mi></math> and charmonium decays, as well as dark photon searches. A <math><msup><mi>Z</mi><mo>′</mo></msup></math> around <math><mo>∼</mo><mn>3</mn></math> or <math><mrow><mo>∼</mo><mo>(</mo><mn>5</mn><mi>–</mi><mn>7</mn><mo>)</mo><mtext> </mtext><mi>GeV</mi></mrow></math> can relieve the tensions in the <math><mi>J</mi><mo>/</mo><mi>ψ</mi><mo>→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup></math> and <math><msup><mi>ψ</mi><mo>′</mo></msup><mo>→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup></math> branching ratios with pion form factor values from fits to BABAR and JLab data and simultaneously explain the charm <math><mi>C</mi><mi>P</mi></math> asymmetries. Models can also feature sizable branching ratios into light right-handed neutrinos or vectorlike dark fermions, which can be searched for in <math><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo>→</mo><mrow><mi>hadrons</mi><mo>+</mo><mi>invisibles</mi></mrow></math> at Belle II and BESIII. Because of the low new physics scale, dark fermions can easily induce an early Landau pole, requiring models to be UV completed near the TeV scale.

<math><mi>U</mi></math>-spin-<math><mi>C</mi><mi>P</mi></math> anomaly in charm

We perform a model-independent analysis of  $$|\Delta b|=|\Delta d|=1$$  <math> <mrow> <mo>|</mo> <mi>Δ</mi> <mi>b</mi> <mo>|</mo> <mo>=</mo> <mo>|</mo> <mi>Δ</mi> <mi>d</mi> <mo>|</mo> <mo>=</mo> <mn>1</mn> </mrow> </math>   processes to test the standard model and probe flavor patterns of new physics. Constraints on Wilson coefficients are obtained from global fits to  $$B^+ \rightarrow \pi ^+ \,\mu ^+\mu ^-$$  <math> <mrow> <msup> <mi>B</mi> <mo>+</mo> </msup> <mo>→</mo> <msup> <mi>π</mi> <mo>+</mo> </msup> <mspace width="0.166667em"></mspace> <msup> <mi>μ</mi> <mo>+</mo> </msup> <msup> <mi>μ</mi> <mo>-</mo> </msup> </mrow> </math>  ,  $$B^0_s\rightarrow \bar{K}^{*0}\, \mu ^+\mu ^-$$  <math> <mrow> <msubsup> <mi>B</mi> <mi>s</mi> <mn>0</mn> </msubsup> <mo>→</mo> <msup> <mrow> <mover> <mrow> <mi>K</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> <mrow> <mrow></mrow> <mo>∗</mo> <mn>0</mn> </mrow> </msup> <mspace width="0.166667em"></mspace> <msup> <mi>μ</mi> <mo>+</mo> </msup> <msup> <mi>μ</mi> <mo>-</mo> </msup> </mrow> </math>  ,  $$B^0\rightarrow \mu ^+\mu ^-$$  <math> <mrow> <msup> <mi>B</mi> <mn>0</mn> </msup> <mo>→</mo> <msup> <mi>μ</mi> <mo>+</mo> </msup> <msup> <mi>μ</mi> <mo>-</mo> </msup> </mrow> </math>  , and radiative  $$B \rightarrow X_d \,\gamma $$  <math> <mrow> <mi>B</mi> <mo>→</mo> <msub> <mi>X</mi> <mi>d</mi> </msub> <mspace width="0.166667em"></mspace> <mi>γ</mi> </mrow> </math>   decays data. The fits are consistent with the standard model but leave sizable room for new physics. Besides higher-statistics measurements and more data in theory-friendly bins of the dilepton mass, further complementary observables such as angular distributions of  $$B_s^0 \rightarrow \bar{K}^{*0}\,\ell ^+ \ell ^-$$  <math> <mrow> <msubsup> <mi>B</mi> <mi>s</mi> <mn>0</mn> </msubsup> <mo>→</mo> <msup> <mrow> <mover> <mrow> <mi>K</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> <mrow> <mrow></mrow> <mo>∗</mo> <mn>0</mn> </mrow> </msup> <mspace width="0.166667em"></mspace> <msup> <mi>ℓ</mi> <mo>+</mo> </msup> <msup> <mi>ℓ</mi> <mo>-</mo> </msup> </mrow> </math>  ,  $$B \rightarrow \rho \,\ell ^+ \ell ^-$$  <math> <mrow> <mi>B</mi> <mo>→</mo> <mi>ρ</mi> <mspace width="0.166667em"></mspace> <msup> <mi>ℓ</mi> <mo>+</mo> </msup> <msup> <mi>ℓ</mi> <mo>-</mo> </msup> </mrow> </math>   or the baryonic modes  $$\Xi _b \rightarrow \Sigma \,\ell ^+ \ell ^-$$  <math> <mrow> <msub> <mi>Ξ</mi> <mi>b</mi> </msub> <mo>→</mo> <mi>Σ</mi> <mspace width="0.166667em"></mspace> <msup> <mi>ℓ</mi> <mo>+</mo> </msup> <msup> <mi>ℓ</mi> <mo>-</mo> </msup> </mrow> </math>  ,  $$\Omega _b^- \rightarrow \Xi ^- \, \ell ^+ \ell ^-$$  <math> <mrow> <msubsup> <mi>Ω</mi> <mi>b</mi> <mo>-</mo> </msubsup> <mo>→</mo> <msup> <mi>Ξ</mi> <mo>-</mo> </msup> <mspace width="0.166667em"></mspace> <msup> <mi>ℓ</mi> <mo>+</mo> </msup> <msup> <mi>ℓ</mi> <mo>-</mo> </msup> </mrow> </math>   are necessary to resolve the significant degeneracy in the fit for the semileptonic four-fermion operators. Assuming minimal quark flavor violation, the  $$b \rightarrow s$$  <math> <mrow> <mi>b</mi> <mo>→</mo> <mi>s</mi> </mrow> </math>   global fit implies tight constraints on the  $$b \rightarrow d$$  <math> <mrow> <mi>b</mi> <mo>→</mo> <mi>d</mi> </mrow> </math>   couplings, and hence allows to test this paradigm with improved data. Another benefit from  $$|\Delta b|=|\Delta d|=1$$  <math> <mrow> <mo>|</mo> <mi>Δ</mi> <mi>b</mi> <mo>|</mo> <mo>=</mo> <mo>|</mo> <mi>Δ</mi> <mi>d</mi> <mo>|</mo> <mo>=</mo> <mn>1</mn> </mrow> </math>   processes is to shed light on the B-anomalies in  $$|\Delta b|=|\Delta s|=1$$  <math> <mrow> <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> </mrow> </math>   modes from a new angle. Specifically, studies of lepton flavor-specific and dineutrino modes are informative on the lepton flavor structure. Rare  $$b \rightarrow d \, \ell \ell , \nu \bar{\nu }$$  <math> <mrow> <mi>b</mi> <mo>→</mo> <mi>d</mi> <mspace width="0.166667em"></mspace> <mi>ℓ</mi> <mi>ℓ</mi> <mo>,</mo> <mi>ν</mi> <mover> <mrow> <mi>ν</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> </math>   decays can be studied at high luminosity flavor facilities LHCb, Belle II, and a future Z-factory.

Marcel Golz

Model-independent analysis of  $$\varvec{b \rightarrow d}$$  <math> <mrow> <mi>b</mi> <mo>→</mo> <mi>d</mi> </mrow> </math>   processes

We address the notorious metastability of the Standard Model (SM) and promote it to a model building task: What are the new ingredients required to stabilize the SM up to the Planck scale without encountering sub-Planckian Landau poles? Using the SM extended by vectorlike fermions, we chart out the corresponding landscape of Higgs stability. We find that the gauge portal mechanism, triggered by new SM charge carriers, opens up sizable room for stability in a minimally invasive manner. We also find models with Higgs criticality and Yukawa portals opening up at stronger coupling. Several models allow for vectorlike fermions in the TeV range, which can be searched for at the LHC. For nontrivial flavor structure, severe flavor-changing neutral current constraints arise that complement those from stability and push lower fermion masses up to <math><mrow><mi>O</mi><mo>(</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>3</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>TeV</mi><mo>)</mo></mrow></math>.

Portals into Higgs vacuum stability

We search for weakly interacting fixed points in extensions of the minimally supersymmetric standard model (MSSM). Necessary conditions lead to three distinct classes of anomaly-free extensions involving either new quark singlets, new quark doublets, or a fourth generation. While interacting fixed points arise prolifically in asymptotically free theories, their existence is significantly constrained as soon as some of the non-abelian gauge sectors are infrared free. Performing a scan over  $$\sim 200$$  <math> <mrow> <mo>∼</mo> <mn>200</mn> </mrow> </math>  k different MSSM extensions using matter field multiplicities and the number of superpotential couplings as free parameters, we find mostly infrared conformal fixed points, and a small subset with ultraviolet ones. All settings predict low-scale supersymmetry-breaking and a violation of R-parity. Despite of residual interactions, the running of couplings out of asymptotically safe fixed points is logarithmic as in asymptotic freedom. Some fixed points can be matched to the Standard Model though the matching scale comes out too low. Prospects for higher matching scales and asymptotic safety beyond the MSSM are indicated.