Light top partners for a light composite Higgs

Self Cite

Abstract:We study the phenomenological implications of a large degree of compositeness for the light generation quarks in composite pseudo-Nambu-Goldstone-boson Higgs models. We focus in particular on phenomenologically viable scenarios where the right-handed uptype quarks have a sizable mixing with the strong dynamics. For concreteness we assume the latter to be characterized by an SO(5)/SO(4) symmetry with fermionic resonances in the SO(4) singlet and fourplet representations. Singlet partners dominantly decay to a Higgs boson and jets. Since no dedicated searches are currently looking for these final states, singlet partners can still be rather light. Conversely, some fourplet partner components dominantly decay to an electroweak gauge boson and a jet, a type of signature which has been analysed at the LHC. We have reinterpreted various ATLAS and CMS analyses in order to constrain the parameter space of this class of models. In the limit of first two generation degeneracy, as in minimal flavor violation or U(2)-symmetric flavor models, fourplet partners need to be relatively heavy, with masses above 1.8 TeV, or the level of compositeness needs to be rather small. The situation is significantly different in models which deviate from the first two generation degeneracy paradigm, as charm quark parton distribution functions are suppressed relative to the up quark ones. We find that JHEP02 (2014)055 the right-handed charm quark component can be mostly composite together with their partners being as light as 600 GeV, while the right-handed up quark needs either to be mostly elementary or to have partners as heavy as 2 TeV. Models where right-handed uptype quarks are fully composite fermions are also analysed and yield qualitatively similar conclusions. Finally, we consider the case where both the fourplet and the singlet states are present. We demonstrate that in this case the fourplet bounds could be significantly weaken due to a combination of smaller production rates and the opening of new channels including cascade processes.

Section: Jhep02(2014)055supporting

confidence: 58%

Section: Modeling the Composite Light Quark Flavorsmentioning

confidence: 99%

Light non-degenerate composite partners at the LHC

Delaunay

Flacke

González-Fraile

et al. 2014

Self Cite

“…Partial compositeness gives an economical mechanism to naturally obtain the hierarchy in the fermionic spectrum of the SM (although flavor mixing require some extra ingredients), it also gives rise to a mild separation of scales in the composite sector. Within partial compositeness, the large top mass requires large mixing, simultaneously leading to some top partners with masses parametrically smaller than the composite scale, these are the components of the multiplet that do not mix with the top before EWSB and are usually called custodians [8,9,21]. These states, being usually the lightest new particles, are the leading candidates to direct searches at colliders.…”

Section: Jhep02(2014)010mentioning

confidence: 99%

“…On the other hand, other common prediction in most of these models of EWSB is the presence of partners of the quarks of the third generation which are lighter than the other new particles [6][7][8][9]. In particular, since the top coupling with the Higgs is order 1, the top quark partners need to be light to stabilize the Higgs potential and keep naturalness.…”

Section: Introductionmentioning

confidence: 99%

Single production of an exotic bottom partner at LHC

Álvarez

Rold

Vietto

2014

We study single production and detection at the LHC run II of exotic partners of the bottom quark. For masses larger than 1 TeV single production can dominate over pair production that is suppressed due to phase space. The presence of exotic partners of the bottom is motivated in models aiming to solve the A b F B anomaly measured at LEP and SLC. Minimal models of this type with partial compositeness predict, as the lightest bottom partner, a new fermion V of electric charge −4/3, also called mirror. The relevant coupling for our study is a W V b vertex, which yields a signal that corresponds to a hard W , a hard b-jet and a forward light jet. We design a search strategy for the leptonic decay of the W , which avoids the large QCD multijet background and its large uncertainties. We find that the main backgrounds are W +jets and tt, and the key variables to enhance the signal over them are a hard b-jet and the rapidity of the light jet. We determine the discovery reach for the LHC run II, in particular we predict that, for couplings of order ∼ g/10, this signal could be detected at a 95% confidence level with a mass up to 2.4 TeV using the first 100 fb −1 .

“…1 This interesting framework has some predictive power. It induces modifications in the Higgs couplings to fermions and EW gauge bosons relative to the Standard Model (SM) [13] and it implies the presence of new physics (NP) resonances [14][15][16][17], as well as top fermionic partners [18][19][20][21][22], still awaiting to be discovered. Yet very little is learned a priori about the flavor sector of (and beyond) the SM within the warped/composite framework.…”

Section: Introductionmentioning

confidence: 99%

Up asymmetries from exhilarated composite flavor structures

Rold

Delaunay

Grojean

et al. 2013

We present a class of warped extra dimension (composite Higgs) models which conjointly accommodates the tt forward-backward asymmetry observed at the Tevatron and the direct CP asymmetry in singly Cabibbo suppressed D decays first reported by the LHCb collaboration. We argue that both asymmetries, if arising dominantly from new physics beyond the Standard Model, hint for a flavor paradigm within partial compositeness models in which the right-handed quarks of the first two generations are not elementary fields but rather composite objects. We show that this class of models is consistent with current data on flavor and CP violating physics, electroweak precision observables, dijet and top pair resonance searches at hadron colliders. These models have several predictions which will be tested in forthcoming experiments. The CP asymmetry in D decays is induced through an effective operator of the form (ūc) V +A (ss) V +A at the charm scale, which implies a larger CP asymmetry in the D 0 → K + K − rate relative the D 0 → π + π − channel. This prediction is distinctive from other Standard Model or dipole-based new physics interpretation of the LHCb result. CP violation in D−D mixing as well as an an excess of dijet production of the LHC are also predicted to be observed in a near future. A large top asymmetry originates from the exchange of an axial resonance which dominantly produces left-handed top pairs. As a result a negative contribution to the lepton-based forward-backward asymmetry in tt production, as well as O(10%) forward-backward asymmetry in bb production above m bb ≃ 600 GeV at the Tevatron is expected.