Survey of vector-like fermion extensions of the Standard Model and their phenomenological implications

229

396

Run 2 LHC data show hints of a new resonance in the diphoton distribution at an invariant mass of 750 GeV. We analyse the data in terms of a new boson, extracting information on its properties and exploring theoretical interpretations. Scenarios covered include a narrow resonance and, as preliminary indications suggest, a wider resonance. If the width indications persist, the new particle is likely to belong to a strongly-interacting sector. We also show how compatibility between Run 1 and Run 2 data is improved by postulating the existence of an additional heavy particle, whose decays are possibly related to dark matter.

Section: Weakly Coupled Modelsmentioning

confidence: 99%

What is the γγ resonance at 750 GeV?

Franceschini

Giudice

Kamenik

et al. 2016

229

396

“…(For some earlier studies of such models, see, e.g., refs. [1][2][3][4][5][6][7][8][9][10].) We focus on vector-like fermions that can have Yukawa couplings involving the Higgs field and the SM fermions.…”

Section: Jhep10(2015)027mentioning

confidence: 99%

New vector-like fermions and flavor physics

Ishiwata

Ligeti

Wise

2015

Abstract:We study renormalizable extensions of the standard model that contain vectorlike fermions in a (single) complex representation of the standard model gauge group. There are 11 models where the vector-like fermions Yukawa couple to the standard model fermions via the Higgs field. These models do not introduce additional fine-tunings. They can lead to, and are constrained by, a number of different flavor-changing processes involving leptons and quarks, as well as direct searches. An interesting feature of the models with strongly interacting vector-like fermions is that constraints from neutral meson mixings (apart from CP violation in K 0 −K 0 mixing) are not sensitive to higher scales than other flavor-changing neutral-current processes. We identify order 1/(4πM ) 2 (where M is the vector-like fermion mass) one-loop contributions to the coefficients of the four-quark operators for meson mixing, that are not suppressed by standard model quark masses and/or mixing angles.

“…Both CMS [21] and ATLAS [22] have recently devoted a considerable effort in the analyses apt to setting bounds on this type of new particles. Initially, simplifying assumptions were considered (mixing only with the third generation of SM quark family or specific decay modes) [23][24][25][26][27][28][29][30][31][32][33]. However the most recent analyses, due to larger data samples, allow exploring more general situations with mixing of VL quarks with the first two generation of SM quarks [34][35][36][37][38].…”

Section: Introductionmentioning

confidence: 99%

Interplay of vector-like top partner multiplets in a realistic mixing set-up

Cacciapaglia

Deandrea

Gaur

et al. 2015

The ATLAS and CMS collaborations at the LHC have performed analyses on the existing data sets, studying the case of one vector-like fermion or multiplet coupling to the standard model Yukawa sector. In the near future, with more data available, these experimental collaborations will start to investigate more realistic cases. The presence of more than one extra vector-like multiplet is indeed a common situation in many extensions of the standard model. The interplay of these vector-like multiplet between precision electroweak bounds, flavour and collider phenomenology is a important question in view of establishing bounds or for the discovery of physics beyond the standard model. In this work we study the phenomenological consequences of the presence of two vector-like multiplets. We analyse the constraints on such scenarios from tree-level data and oblique corrections for the case of mixing to each of the SM generations. In the present work, we limit to scenarios with two top-like partners and no mixing in the down-sector.