More Like this

1. Energy-enhanced dimension eight SMEFT effects in VBF Higgs production

   https://doi.org/10.1007/JHEP02(2025)029  

   Assi, Benoît; Martin, Adam (February 2025, Journal of High Energy Physics)

   A<sc>bstract</sc> We study Higgs boson production via vector boson fusion at the LHC, focusing on the processpp→H+jjand capturing the leading energy-enhanced contributions within the Standard Model Effective Field Theory (SMEFT) up to order 1/Λ⁴. Employing energy-scaling arguments, we predict the magnitude of each higher-dimensional operator’s contribution. Utilizing the geometric formulation of SMEFT, our analysis incorporates dimension-eight operators not previously considered. We find that the kinematics of vector boson fusion — characterized by two highly forward jets — tend to suppress contributions from higher-dimensional operators, requiring a lower scale Λ for SMEFT effects to become observable. This suggests that the SMEFT remains valid for lower Λ than expected. Combined with the fact that LEP constrains the dimension-six operators with the most considerable impact on vector boson fusion, a regime exists where dimension-eight operators can have significant effects. In many cases, these dimension-eight operators also influence associated production processes likepp→HV(jj), though differences in analysis cuts and kinematics mean this is not always the case. Our findings provide insights that could refine the search for SMEFT signals in collider experiments. 

   more » « less
2. Drell-Yan production in universal theories beyond dimension-six SMEFT

   https://doi.org/10.1103/cktt-qrmn  

   Corbett, Tyler; Desai, Jay; Éboli, O_J P; Gonzalez-Garcia, M C; Martines, Matheus; Reimitz, Peter (July 2025, Physical Review D)

   We study Drell-Yan production in universal theories consistently including effects beyond dimension six in the Standard Model effective field theory (SMEFT). Within universal SMEFT and with $C$and $P$conservation we find that 11 dimension-eight operators contribute in addition to the six contributing at dimension six. We first work in an operator basis in which operators with higher derivatives of the bosonic fields have been rotated by equations of motion in favor of combinations of operators involving SM fermion currents. We derive the general form of the amplitudes consistently in the expansion to $\mathcal{O}\left({\mathrm{\Lambda }}^{-4}\right)$and identify eight combinations of the 17 Wilson coefficients which are physically distinguishable by studying the invariant mass distribution of the lepton pairs produced. We then introduce an extension of the parametrization of universal effects in terms of oblique parameters obtained by linearly expanding the self-energies of the electroweak gauge bosons to $\mathcal{O}\left(q^6\right)$. It contains 11 oblique parameters of which only eight are generated within SMEFT at dimension eight: $\hat{S}$, $\hat{T}$, $W$, $Y$, $\hat{U}$, $X$, plus two additional which we label $W^{\prime }$and $Y^{\prime }$and show how they match at linear order with the eight identified combinations of operator coefficients. We then perform a combined analysis of a variety of LHC data on the neutral- and charged-current Drell-Yan processes with the aim of constraining the eight combinations. We compare and combine the LHC bounds with those from electroweak precision $W$and $Z$pole observables which can only provide constraints in four directions of the eight-parameter space. We present the results in terms of limits on the eight effective Wilson coefficients as well as on the eight oblique parameters. In each case, we study the dependence of the derived constraints on the order of the expansion considered. 

   more » « less
3. 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. 

   more » « less
4. LHC EFT WG note: Basis for anomalous quartic gauge couplings

   https://doi.org/10.21468/SciPostPhysCommRep.6  

   Durieux, Gauthier; Remmen, Grant; Rodd, Nicholas L; Éboli, Oscar; Gonzalez-Garcia, Maria C; Kondo, Dan; Murayama, Hitoshi; Okabe, Risshin (February 2025, SciPost Physics Community Reports)

   In this note, we give a definitive basis for the dimension-eight operators leading to quartic—but no cubic—interactions among electroweak gauge bosons. These are often called anomalous quartic gauge couplings, or aQGCs. We distinguish in particular the CP-even ones from their CP-odd counterparts. 

   more » « less
5. 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. 

   more » « less