Higgs boson production at large transverse momentum within the SMEFT: analytical results

The European Physical Journal C, Oct 2018

We consider Higgs boson production through gluon fusion at large transverse momentum in hadronic collisions. We present the analytic expressions of the relevant one-loop QCD amplitudes including the effects of the complete set of dimension-six operators. The latter correspond to modifications of the top and bottom Yukawa couplings, to an effective point-like Higgs coupling to gluons and to the chromomagnetic operator of the top quark. The quantitative impact of the chromomagnetic operator is also studied. Our results confirm previous findings that the effect of the chromomagnetic operator at high \(p_T\) can be large and should not be neglected.

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Higgs boson production at large transverse momentum within the SMEFT: analytical results

The European Physical Journal C October 2018, 78:808 | Cite as Higgs boson production at large transverse momentum within the SMEFT: analytical results AuthorsAuthors and affiliations Massimiliano GrazziniAgnieszka IlnickaMichael Spira Open Access Regular Article - Theoretical Physics First Online: 04 October 2018 73 Downloads Abstract We consider Higgs boson production through gluon fusion at large transverse momentum in hadronic collisions. We present the analytic expressions of the relevant one-loop QCD amplitudes including the effects of the complete set of dimension-six operators. The latter correspond to modifications of the top and bottom Yukawa couplings, to an effective point-like Higgs coupling to gluons and to the chromomagnetic operator of the top quark. The quantitative impact of the chromomagnetic operator is also studied. Our results confirm previous findings that the effect of the chromomagnetic operator at high \(p_T\) can be large and should not be neglected. 1 Introduction After the discovery of the scalar resonance of mass 125 GeV [1, 2] the measurement of its properties is one of the main activities of the LHC program. The Run I measurements [3] showed that the new resonance is compatible with the Standard Model Higgs boson. There is, however, still the possibility that more precise measurements will uncover small deviations from the Standard Model (SM) predictions. These might be the long lasting legacy of the LHC, which will encompass the searches for New Physics. The need of a consistent framework to capture small deviations from the SM is reflected in the wide discussions in Refs. [4, 5, 6]. The Standard Model Effective Field Theory (SMEFT) is a promising and theory motivated approach, in which the deviations from the SM are parametrised with higher-dimension operators, in the first approximation dimension six [7, 8]. Next to the inclusive quantities, differential Higgs observables were measured in Run I [9, 10, 11, 12, 13, 14, 15] and with a partial data set of Run II [16, 17, 18], although still with relatively large uncertainties. With the increasing amount of collected data, the statistical accuracy will improve, thereby allowing us to put stringent constraints on the SMEFT parameters. One of the observables which is able to shed light on the structure of the Higgs sector is the transverse momentum spectrum (\(p_T\)) of the Higgs particle. For example, a measurement of the \(p_T\) spectrum could give insight on the nature of the Higgs boson coupling to gluons (see e.g. Refs. [19, 20]). Recent years have seen considerable progress in the theoretical control of the \(p_T\) spectrum in the SM [21, 22, 23, 24, 25, 26, 27]. In particular, the NLO QCD corrections are now available including the exact dependence on the top-quark mass [28]. Dedicated calculations and tools are needed to enable the experimental analyses to set bounds on the SMEFT operators. Approximate results for the total gluon fusion Higgs production cross section including modified top and bottom Yukawa couplings and an additional direct Hgg interaction have been obtained at NNLO in QCD perturbation theory in Ref. [29] and at N\(^3\)LO in Refs. [30, 31]. As far as gluon fusion is concerned, the inclusion of dimension-six and dimension-eight operators in the Higgs \(p_T\)-spectrum also has been considered in Refs. [32, 33, 34] and [35, 36], respectively. Strategies for extracting information on the Higgs-gluon couplings from the measurements were studied in Ref. [34], and the study the low-\(p_T\) range therein was made possible by using Monte Carlo Parton Shower. Also in Ref. [20] the prospects of the determination of the Wilson coefficients in the high-luminosity LHC and future colliders were considered. The mentioned studies usually omitted the effects of the chromomagnetic operator, but a dedicated work analysed its effect on the LO Higgs production [37]. This was followed by a LO study [38] on the interplay of the SMEFT operators entering top-induced Higgs production channels, with the chromomagnetic operator treated in the heavy-top limit (HTL). Recently, the program of the SMEFT at NLO QCD was started by the MadGraph5_aMC@NLO group [39] and led to the calculation of \(t\bar{t}H, tH\) [40] and recently also of Higgs production through gluon fusion [41]. In this work we recall the results for the LO Higgs production via gluon fusion and we extend our study [42] of the Higgs \(p_T\) spectrum to include the effects of the chromomagnetic operator. More precisely, we present the analytic expressions of the relevant one-loop QCD amplitudes including the effects of the complete set of dimension-six operators and we shortly illustrate the impact of the chromomagnetic operator on the high-\(p_T\) tail of the spectrum. Note that, due to the automated character of the calculations in the MadGraph5_aMC@NLO framework [40, 41], they can be considered complementary to the analytic calculations pr (...truncated)


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Massimiliano Grazzini, Agnieszka Ilnicka, Michael Spira. Higgs boson production at large transverse momentum within the SMEFT: analytical results, The European Physical Journal C, 2018, pp. 808, Volume 78, Issue 10, DOI: 10.1140/epjc/s10052-018-6261-7