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1. Exact SMEFT formulation and expansion to $$ \mathcal{O} $$(v4/Λ4)

   https://doi.org/10.1007/JHEP11(2020)087  

   Hays, Chris ; Helset, Andreas ; Martin, Adam ; Trott, Michael ( November 2020 , Journal of High Energy Physics)

   null (Ed.)

   A bstract The Standard Model Effective Field Theory (SMEFT) theoretical framework is increasingly used to interpret particle physics measurements and constrain physics beyond the Standard Model. We investigate the truncation of the effective-operator expansion using the geometric formulation of the SMEFT, which allows exact solutions, up to mass-dimension eight. Using this construction, we compare the exact solution to the expansion at $$ \mathcal{O} $$ O ( v 2 / Λ 2 ), partial $$ \mathcal{O} $$ O ( v 4 / Λ 4 ) using a subset of terms with dimension-6 operators, and full $$ \mathcal{O} $$ O ( v 4 / Λ 4 ), where v is the vacuum expectation value and Λ is the scale of new physics. This comparison is performed for general values of the coefficients, and for the specific model of a heavy U(1) gauge field kinetically mixed with the Standard Model. We additionally determine the input-parameter scheme dependence at all orders in v/ Λ, and show that this dependence increases at higher orders in v/ Λ. 

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2. EWPD in the SMEFT to dimension eight

   https://doi.org/10.1007/JHEP06(2021)076  

   Corbett, Tyler ; Helset, Andreas ; Martin, Adam ; Trott, Michael ( June 2021 , Journal of High Energy Physics)

   null (Ed.)

   A bstract We calculate the $$ \mathcal{O}\left({\left\langle {H}^{\dagger }H\right\rangle}^2/{\Lambda}^4\right) $$ O H † H 2 / Λ 4 corrections to LEP electroweak precision data using the geometric formulation of the Standard Model Effective Field Theory (SMEFT). We report our results in simple-to-use interpolation tables that allow the interpretation of this data set to dimension eight for the first time. We demonstrate the impact of these previously unknown terms in the case of a general analysis in the SMEFT, and also in the cases of two distinct models matched to dimension eight. Neglecting such dimension-eight corrections to LEP observables introduces a theoretical error in SMEFT studies. We report some preliminary studies defining such a theory error, explicitly demonstrating the effect of previously unknown dimension-eight SMEFT corrections on LEP observables. 

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3. Charged lepton flavor violation at the EIC

   https://doi.org/10.1007/JHEP03(2021)256  

   Cirigliano, Vincenzo ; Fuyuto, Kaori ; Lee, Christopher ; Mereghetti, Emanuele ; Yan, Bin ( March 2021 , Journal of High Energy Physics)

   null (Ed.)

   A bstract We present a comprehensive analysis of the potential sensitivity of the Electron-Ion Collider (EIC) to charged lepton flavor violation (CLFV) in the channel ep → τX , within the model-independent framework of the Standard Model Effective Field Theory (SMEFT). We compute the relevant cross sections to leading order in QCD and electroweak corrections and perform simulations of signal and SM background events in various τ decay channels, suggesting simple cuts to enhance the associated estimated efficiencies. To assess the discovery potential of the EIC in τ - e transitions, we study the sensitivity of other probes of this physics across a broad range of energy scales, from pp → eτX at the Large Hadron Collider to decays of B mesons and τ leptons, such as τ → eγ , τ → eℓ + ℓ − , and crucially the hadronic modes τ → eY with Y ∈ π, K, ππ, Kπ, …. We find that electroweak dipole and four-fermion semi-leptonic operators involving light quarks are already strongly constrained by τ decays, while operators involving the c and b quarks present more promising discovery potential for the EIC. An analysis of three models of leptoquarks confirms the expectations based on the SMEFT results. We also identify future directions needed to maximize the reach of the EIC in CLFV searches: these include an optimization of the τ tagger in hadronic channels, an exploration of background suppression through tagging b and c jets in the final state, and a global fit by turning on all SMEFT couplings, which will likely reveal new discovery windows for the EIC. 

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4. Search for heavy resonances decaying into a Z or W boson and a Higgs boson in final states with leptons and b-jets in 139 fb−1 of pp collisions at $$ \sqrt{s} $$ = 13 TeV with the ATLAS detector

   https://doi.org/10.1007/JHEP06(2023)016  

   Aad, G. ; Abbott, B. ; Abbott, D. C. ; Abeling, K. ; Abidi, S. H. ; Aboulhorma, A. ; Abramowicz, H. ; Abreu, H. ; Abulaiti, Y. ; Abusleme Hoffman, A. C. ; et al ( June 2023 , Journal of High Energy Physics)

   This article presents a search for new resonances decaying into aZorWboson and a 125 GeV Higgs bosonh, and it targets the$$ \nu \overline{\nu}b\overline{b} $$$\nu \overline{\nu }b\overline{b}$,$$ {\ell}^{+}{\ell}^{-}b\overline{b} $$${\ell }^{+}{\ell }^{-}b\overline{b}$, or$$ {\ell}^{\pm}\nu b\overline{b} $$${\ell }^{\pm }\mathrm{\nu b}\overline{b}$final states, whereℓ=eorμ, in proton-proton collisions at$$ \sqrt{s} $$$\sqrt{s}$= 13 TeV. The data used correspond to a total integrated luminosity of 139 fb⁻¹collected by the ATLAS detector during Run 2 of the LHC at CERN. The search is conducted by examining the reconstructed invariant or transverse mass distributions ofZhorWhcandidates for evidence of a localised excess in the mass range from 220 GeV to 5 TeV. No significant excess is observed and 95% confidence-level upper limits between 1.3 pb and 0.3 fb are placed on the production cross section times branching fraction of neutral and charged spin-1 resonances and CP-odd scalar bosons. These limits are converted into constraints on the parameter space of the Heavy Vector Triplet model and the two-Higgs-doublet model.

    

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5. Observation of a $$ {\varLambda}_b^0 $$ − $$ {\overline{\varLambda}}_b^0 $$ production asymmetry in proton-proton collisions at $$ \sqrt{s} $$ = 7 and 8 TeV

   https://doi.org/10.1007/JHEP10(2021)060  

   Aaij, R. ; Abdelmotteleb, A. S. ; Abellán Beteta, C. ; Ackernley, T. ; Adeva, B. ; Adinolfi, M. ; Afsharnia, H. ; Aidala, C. A. ; Aiola, S. ; Ajaltouni, Z. ; et al ( October 2021 , Journal of High Energy Physics)

   A bstract This article presents differential measurements of the asymmetry between $$ {\varLambda}_b^0 $$ Λ b 0 and $$ {\overline{\varLambda}}_b^0 $$ Λ ¯ b 0 baryon production rates in proton-proton collisions at centre-of-mass energies of $$ \sqrt{s} $$ s = 7 and 8 TeV collected with the LHCb experiment, corresponding to an integrated luminosity of 3 fb − 1 . The $$ {\varLambda}_b^0 $$ Λ b 0 baryons are reconstructed through the inclusive semileptonic decay $$ {\varLambda}_b^0 $$ Λ b 0 → $$ {\varLambda}_c^{+} $$ Λ c + μ − $$ \overline{\nu} $$ ν ¯ μ X . The production asymmetry is measured both in intervals of rapidity in the range 2 . 15 < y < 4 . 10 and transverse momentum in 2 < p T < 27 GeV/ c . The results are found to be incompatible with symmetric production with a significance of 5.8 standard deviations for both $$ \sqrt{s} $$ s = 7 and 8 TeV data, assuming no CP violation in the decay. There is evidence for a trend as a function of rapidity with a significance of 4 standard deviations. Comparisons to predictions from hadronisation models in P ythia and heavy-quark recombination are provided. This result constitutes the first observation of a particle-antiparticle asymmetry in b -hadron production at LHC energies. 

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