No abstract

We study the constraints that can be placed on anomalous τ -lepton couplings at the LHC. We use an effective Lagrangian description for physics beyond the standard model which contains the τ -lepton anomalous magnetic moment, electric dipole moment and weak dipole moments in two operators of dimension six. We include in our study two additional operators of dimension eight that directly couple the τ -leptons to gluons and are therefore enhanced at the LHC. We consider the two main effects from these couplings: modifications to the Drell-Yan cross-section and to the τ -lepton pair production in association with a Higgs boson. We find that a measurement of the former at the 14% level can produce constraints comparable to existing ones for the anomalous dipole couplings; and that a bound on the latter at a sensitivity level of 500 σ SM or better would produce the best constraint on the τ -gluonic couplings.

We extract constraints on the parameter space of the MW model by comparing the cross-sections for dijet, top-pair, dijet-pair, tttt and bbbb productions at the LHC with the strongest available experimental limits from ATLAS or CMS at 8 or 13 TeV. Overall we find mass limits around 1 TeV in the most sensitive regions of parameter space, and lower elsewhere. This is at odds with generic limits for color octet scalars often quoted in the literature where much larger production cross-sections are assumed. The constraints that can be placed on coupling constants are typically weaker than those from existing theoretical considerations, with the exception of the parameter η D .

Physics beyond the standard model (SM) can be parameterized with an effective Lagrangian that respects the symmetries of the standard model and contains many operators of dimension six. We consider the subset of these operators that is responsible for flavor diagonal anomalous color magnetic (CMDM) and electric (CEDM) dipole couplings between quarks and gluons. Invariance of these operators under the SM implies that they contribute to Higgs boson production at the LHC and we study the corresponding constraints that can be placed on them. For the case of the top-quark we first review constraints from top-quark pair production and decay, and then compare them to what can be achieved by studying tth production. We also constrain the corresponding couplings for b-quarks and light quarks by studying pp → bbh and pp → hX respectively.

The operators that break supersymmetry can be holomorphic or non-holomorphic in structure. The latter do not pose any problem for gauge hierarchy and are soft provided that the particle spectrum does not contain any gauge singlets. In minimal supersymmetric model (MSSM) we discuss the impact of non-holomorphic soft-breaking terms on the Higgs sector. We find that non-holomorphic operators can cause significant changes as are best exhibited by the correlation between the masses of the charginos and Higgs boson