Resolving gluon fusion loops at current and future hadron colliders

Received: August Resolving gluon fusion loops at current and future hadron colliders Aleksandr Azatov 0 1 4 5 6 7 8 Christophe Grojean 0 1 2 4 6 7 8 Ayan Paul 0 1 4 6 7 8 Ennio Salvioni 0 1 3 4 6 7 8 E-mail: 0 1 4 6 7 8 0 1 4 6 7 8 0 P. le A. Moro 2, I-00185 Rome , Italy 1 Notkestrasse 85 , D-22607 Hamburg , Germany 2 On leave of absence from: ICREA, E-08010 Barcelona , Spain and IFAE , Barcelona Institute of Science 3 Physics Department, University of California 4 Strada Costiera 11 , I-34151 Trieste , Italy 5 Abdus Salam International Centre for Theoretical Physics 6 Open Access , c The Authors 7 and Technology (BIST) Campus UAB , E-08193 Bellaterra , Spain 8 Davis , One Shields Avenue, CA 95616 , U.S.A Inclusive Higgs measurements at the LHC have limited resolution on the gluon fusion loops, being unable to distinguish the long-distance contributions mediated by the top quark from possible short-distance new physics e ects. Using an E ective Field Theory (EFT) approach we compare several proposed methods to lift this degeneracy, including tth and boosted, o -shell and double Higgs production, and perform detailed projections to the High-Luminosity LHC and a future hadron collider. In addition, we revisit o -shell Higgs production. Firstly, we point out its sensitivity to modi cations of the top-Z couplings, and by means of a general analysis we show that the reach is comparable to that of treelevel processes such as ttZ production. Implications for composite Higgs models are also discussed. Secondly, we assess the regime of validity of the EFT, performing an explicit comparison for a simple extension of the Standard Model containing one vector-like quark. hadron; colliders; Beyond Standard Model; E ective eld theories; Higgs Physics; Technicolor 1 Introduction 2 3 4 HL-LHC and FCC prospects E ects of top-Z couplings in o -shell Higgs Toy model with a single vector-like quark O -shell Higgs analysis including top-Z couplings 3.3 Implications for composite Higgs models Comparison to other gluon-fusion processes Validity of the EFT for o -shell Higgs Summary and outlook A.1 14 TeV A.2 100 TeV B.1 14 TeV B.2 100 TeV A O -shell Higgs analysis B Boosted Higgs analysis One of the main goals of the Large Hadron Collider (LHC) is to unveil the origin of the electroweak symmetry breaking (EWSB): is it driven by a solitary and elementary Higgs eld as in the Standard Model (SM), or is there additional dynamics not too far above the weak scale? New physics around the TeV frontier can reveal itself in a direct way, through the discovery of new particle resonances, or indirectly, via modi cations of the interactions Since the discovery of the Higgs boson in 2012, the numerous LHC measurements aimed at testing its properties have revealed an increasingly precise pro le consistent with the SM predictions [1, 2]. Yet, no information can be extracted on the values of the Higgs couplings without assumptions, for instance on the Higgs boson total width. Furthermore, the current measurements, being dominated by inclusive observables, su er from `blind' directions in the exploration of the parameter space of the Higgs couplings. In particular, as emphasized in refs. [3, 4], the current constraints allow for O(1) deviations of the htt coupling if correlated contact interactions between the Higgs boson and gluons and photons are simultaneously present. Far from a mere academic question, this degeneracy is especially relevant in models where the Higgs is a composite pseudo NambuGoldstone boson (pNGB) [5, 6], where the inclusive Higgs rates are typically insensitive to the spectrum of the fermionic resonances [7{11]. An analogous situation can be realized in natural supersymmetry, where the top and stop loops can conspire to leave the inclusive Higgs production SM-like [4]. In these scenarios indirect signs of the top partners, which play a crucial role in addressing Higgs naturalness, can therefore only be seen by accessing individually the htt and hgg couplings in exclusive measurements. The most obvious candidate is Higgs production in association with a top quark pair, see for example refs. [12, 13] for recent studies. However, in the last few years several other proposals have been put forward, including boosted Higgs production [3, 4, 14{19] (see also refs. [20{22] for previous studies where the Higgs transverse momentum distribution was exploited as a handle on new physics), o -shell Higgs production [23{25], and double Higgs production in gluon fusion [26, 27]. In section 2 of this paper we combine existing results for all the above processes, to estimate the future resolution on the Higgs gluon fusion loops at the High-Luminosity LHC (HL-LHC), de ned as a 14 TeV pp collider with 3 ab 1 of integrated luminosity, and at the hadron-hadron Future Circular Collider (FCC-hh, abbreviated to FCC except where confusion is possible with the electron-positron version, FCC-ee), de ned as a 100 TeV pp collider with bench (...truncated)