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We estimate the future sensitivity of the high luminosity (HL-) and high energy (HE-) modes of the Large Hadron Collider (LHC) and of a 100 TeV future circular collider (FCC-hh) to leptoquark (LQ) pair production in the muon-plus-jet decay mode of each LQ. Such LQs are motivated by the fact that they provide an explanation for the neutral current B -anomalies. For each future collider, Standard Model (SM) backgrounds and detector effects are simulated. From these, sensitivities of each collider are found. Our measures of sensitivity are based upon a Run II ATLAS search, which we also use for validation. We illustrate with a narrow scalar (‘ S 3 ’) LQ and find that, in our channel, the HL-LHC has exclusion sensitivity to LQ masses up to 1.8 TeV, the HE-LHC up to 4.8 TeV and the FCC-hh up to 13.5 TeV.

A bstract Spontaneously broken, flavour-dependent, gauged U(1) extensions of the Standard Model (SM) have many phenomenological uses. We chart the space of solutions to the gauge anomaly cancellation equations in such extensions, for both the SM chiral fermion content and the SM plus (up to) three right-handed neutrinos (SM ν R ). Methods from Diophantine analysis allow us to efficiently index the solutions arithmetically, and produce the complete solution space in particular cases. In order to solve the general case, we build a computer program which cycles through possible U(1) charge assignments, providing all solutions for charges up to some pre-defined maximum absolute charge. Lists of anomaly-free U(1) charge assignments result, which corroborate the results of our Diophantine analysis. We make these lists, which may be queried for further desirable properties, publicly available. This previously uncharted space of anomaly-free charge assignments has been little explored until now, paving the way for future model building and phenomenological studies.

A bstract Costa et al. [ Phys. Rev. Lett. 123 (2019) 151601] recently gave a general solution to the anomaly equations for n charges in a U(1) gauge theory. ‘Primitive’ solutions of chiral fermion charges were parameterised and it was shown how operations performed upon them (concatenation with other primitive solutions and with vector-like solutions) yield the general solution. We show that the ingenious methods used there have a simple geometric interpretation, corresponding to elementary constructions in number theory. Viewing them in this context allows the fully general solution to be written down directly, without the need for further operations. Our geometric method also allows us to show that the only operation Costa et al. require is permutation. It also gives a variety of other, qualitatively similar, parameterisations of the general solution, as well as a qualitatively different (and arguably simpler) form of the general solution for n even.

We study the LHC phenomenology of the next-to-minimal model of gauge-mediated supersymmetry breaking, both for Run I and Run II. The Higgs phenomenology of the model is consistent with observations: a 125 GeV standard model-like Higgs which mixes with singlet-like state of mass around 90 GeV that provides a 2 σ excess at LEP II. The model possesses regions of parameter space where a longer-lived lightest neutralino decays in the detector into a gravitino and a b -jet pair or a tau pair resulting in potential displaced vertex signatures. We investigate current bounds on sparticle masses and the discovery potential of the model, both via conventional searches and via searches for displaced vertices. The searches based on promptly decaying sparticles currently give a lower limit on the gluino mass 1080 GeV and could be sensitive up to 1900 GeV with 100 fb - 1 , whereas the current displaced vertex searches cannot probe this model due to b -quarks in the final state. We show how the displaced vertex cuts might be relaxed in order to improve signal efficiency, while simultaneously applied prompt cuts reduce background, resulting in a much better sensitivity than either strategy alone and motivating a fully fledged experimental study.

A bstract We examine current collider constraints on some simple Z ′ models that fit neutral current B -anomalies, including constraints coming from measurements of Standard Model (SM) signatures at the LHC. The ‘MDM’ simplified model is not constrained by the SM measurements but is strongly constrained by a 139 fb −1 13 TeV ATLAS di-muon search. Constraints upon the ‘MUM’ simplified model are much weaker. A combination of the current B s mixing constraint and ATLAS’ Z ′ search implies M Z ′ > 1.2 TeV in the Third Family Hypercharge Model example case. LHC SM measurements rule out a portion of the parameter space of the model for M Z ′ > 1.5 TeV.

While it is known that third family hypercharge models can explain the neutral current B-anomalies, it was hitherto unclear whether the Z-Z′ mixing predicted by such models could simultaneously fit electroweak precision observables. Here, we perform global fits of several third family hypercharge models to a combination of electroweak data and those data pertinent to the neutral current B-anomalies. While the Standard Model is in tension with this combined data set with a p-value of .0007, simple versions of the models (fitting two additional parameters each) provide much improved fits. The original Third Family Hypercharge Model, for example, has a p-value of .065, with Δχ2=6.5σ.

A bstract Recent measurements in B → K (*) μ + μ − decays are somewhat discrepant with Standard Model predictions. They may be harbingers of new physics at an energy scale potentially accessible to direct discovery. We estimate the sensitivity of future hadron colliders to the possible new particles that may be responsible for the anomalies at tree-level: leptoquarks or Z ′s. We consider luminosity upgrades for a 14 TeV LHC, a 33 TeV LHC, and a 100 TeV pp collider such as the FCC-hh. In the most conservative and pessimistic models, for narrow particles with perturbative couplings, Z ′ masses up to 20 TeV and leptoquark masses up to 41 TeV may in principle explain the anomalies. Coverage of Z ′ models is excellent: a 33 TeV 1 ab −1 LHC is expected to cover most of the parameter space up to 8 TeV in mass, whereas the 100 TeV FCC-hh with 10 ab −1 will cover all of it. A smaller portion of the leptoquark parameter space is covered by future colliders: for example, in a μ + μ − jj di-leptoquark search, a 100 TeV 10 ab −1 collider has a projected sensitivity up to leptoquark masses of 12 TeV (extendable to 21 TeV with a strong coupling for single leptoquark production).

The Third Family Hypercharge Model predicts a Z′ gauge boson with flavour dependent couplings which has been used to explain anomalies in meson decay processes which involve the b→sμ+μ- transition. The model predicts that a TeV-scale Z′ should decay to particle-antiparticle pairs of muons, taus, top quarks and bottom quarks with appreciable branching ratios. We reinterpret various ATLAS and CMS search limits for Z′ production followed by such decays at the LHC over a parameter space of the model that results from a successful combined fit to the b→sl+l- data and precision electroweak observables. Current exclusions in parameter space and expected sensitivities of the various different channels in the high-luminosity run are compared. We find that the high-luminosity run of the LHC will significantly increase the sensitivity to the model beyond the existing empirical limits, which we find to be surprisingly weak.

A Correction to this paper has been published https://doi.org/10.1140/epjc/s10052-021-08855-w