Related papers: Leptoquarks and Contact Interactions at LeHC
The standard model weak interactions can be described by four-fermion V-A operators at low energies. New physics at the TeV scale can, however, generate the other Lorentz structures. In this talk, we review the constraints on such…
We report on a search for the pair production of second generation scalar leptoquarks (LQ) in ppbar collisions at the center of mass energy sqrt(s)=1.96 TeV using a data set corresponding to an integrated luminosity of 1.0 fb-1 collected…
We evaluate the observability of the effects of a scalar singlet leptoquark (LQ) in $\mu$ and $\tau$-pair productions at the $Z$ factory. In the scenario addressing the charged-current anomalies, the LQ contributions to $\mu$-pair final…
The results of a search for direct pair production of heavy top-quark partners in 4.7 fb-1 of integrated luminosity from pp collisions at sqrt(s) = 7 TeV collected by the ATLAS detector at the LHC are reported. Heavy top-quark partners…
We attempt to explain recent anomalies in semileptonic $B$ decays at LHCb via a composite Higgs model, in which both the Higgs and an $SU(2)_L$-triplet leptoquark arise as pseudo-Goldstone bosons of the strong dynamics. Fermion masses are…
The cross sections for the formation of scalar resonances, leptoquarks or squarks, in electron/positron-proton collisions at HERA are presented including next-to-leading order QCD corrections. Depending mildly on the mass of the resonances,…
The recent measurement of atomic parity violation in cesium atoms shows a $2.3\sigma$ deviation from the standard model prediction. We show that such an effect can be explained by four-fermion contact interactions with specific chiralities…
The searches for extra-dimensions, top resonances, 4th generation quarks and leptoquark signatures are presented. The results are based on proton-proton collision data for a center-of mass energy of7 or 8 TeV, corresponding to various…
Dark matter particles that couple primarily to leptons are only weakly constrained by data from direct detection experiments and the LHC. However, models of this kind necessarily generate effective four-lepton contact interactions at the…
The ATLAS and CMS experiments at the Large Hadron Collider (LHC) will soon search for physics phenomena that are not predicted by the Standard Model. Technicolor, Compositeness and GUT-based models are rich in high-pt leptons and could be…
Vector-like top partners with electric charge $+2/3$ are predicted in many extensions of the Standard Model and are actively searched for at the LHC through their electroweak decays $T\to Wb$, $Zt$, and $Ht$. More general scenarios,…
A search is presented for a singly produced third-generation scalar leptoquark decaying to a $\tau$ lepton and a bottom quark. Associated production of a leptoquark and a $\tau$ lepton is considered, leading to a final state with a bottom…
I give an overview of the ability of a high energy $\mu^+\mu^-$ collider to discover new particles and interactions. I start with heavy fermions which will be the most straightforward to produce and observe. I then discuss single leptoquark…
The top quark mass is currently measured to delta m_t^{exp,Tevatron} = 2.9 GeV and will be measured at the LHC to a precision of delta m_t^{exp,LHC} \approx 1-2 GeV. We show that even this impressive precision will not be sufficient for…
Quark partners with non-chiral couplings appear in several extensions of the Standard Model. They may have non-trivial generational structure to their couplings, and may be produced either in pairs via the strong and EM interactions, or…
Leptoquarks (LQs) provide very promising solutions to the tensions between the experimental measurements and the SM predictions of $b\to s\ell^+\ell^-$ and $b\to c\tau\nu$ processes. In this case the LQ masses are in general at the TeV…
Many new physics models, such as the Sequential Standard Model, Grand Unified Theories, models of extra dimensions, or models like leptoquarks or vector-like leptons, predict heavy mediators at the TeV energy scale. We present recent…
Resonant productions of the first generation scalar and vector diquarks at high energy hadron-hadron (pp), lepton-hadron (ep) and lepton-lepton (e+e-) colliders are investigated. Taking into account the hadronic component of the photon,…
We establish constraints on a general four-fermion contact interaction from precise measurements of electroweak parameters. We compute the one-loop contribution for the leptonic $Z$ width, anomalous magnetic, weak-magnetic, electric and…
A sequential fourth generation of quarks and leptons is allowed by precision electroweak constraints if the mass splitting between the heavy quarks is between 50 and 80 GeV. Although heavy quarks can be easily detected at the LHC, it is…