2,410 research outputs found
Anarchy with linear and bilinear interactions
Composite Higgs models with anarchic partial compositeness require a scale of
new physics TeV, with the bounds being dominated by the
dipole moments and . The presence of anarchic bilinear interactions
can change this picture. We show a solution to the SM flavor puzzle where the
electron and the Right-handed quarks of the first generation have negligible
linear interactions, and the bilinear interactions account for most of their
masses, whereas the other chiral fermions follow a similar pattern to anarchic
partial compositeness. We compute the bounds from flavor and CP violation and
show that neutron and electron dipole moments, as well as and
, are compatible with a new physics scale below the TeV.
operators involving Left-handed quarks and operators
with give the most stringent bounds in this scenario. Their Wilson
coefficients have the same origin as in anarchic partial compositeness,
requiring the masses of the new states to be larger than TeV.Comment: 26 page
Minimal Composite Higgs Models at the LHC
We consider composite Higgs models where the Higgs is a pseudo-Nambu
Goldstone boson arising from the spontaneous breaking of an approximate global
symmetry by some underlying strong dynamics. We focus on the SO(5) -> SO(4)
symmetry breaking pattern, assuming the partial compositeness paradigm. We
study the consequences on Higgs physics of the fermionic representations
produced by the strong dynamics, that mix with the Standard Model (SM) degrees
of freedom. We consider models based on the lowest-dimensional representations
of SO(5) that allow for the custodial protection of the Z -> b b coupling, i.e.
the 5, 10 and 14. We find a generic suppression of the gluon fusion process,
while the Higgs branching fractions can be enhanced or suppressed compared to
the SM. Interestingly, a precise measurement of the Higgs boson couplings can
distinguish between different realizations in the fermionic sector, thus
providing crucial information about the nature of the UV dynamics.Comment: 55 pages, 18 figures, References adde
Up Asymmetries From Exhilarated Composite Flavor Structures
We present a class of warped extra dimension (composite Higgs) models which
conjointly accommodates the t\bar t 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
(\bar u c)_{V+A}(\bar s s)_{V+A} at the charm scale, which implies a larger CP
asymmetry in the D^0\to K^+K^- rate relative the D^0\to \pi^+\pi^- channel.
This prediction is distinctive from other Standard Model or dipole-based new
physics interpretation of the LHCb result. CP violation in D-\bar 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 t\bar t production, as well as O(10%) forward-backward asymmetry in b\bar b
production above m_{b\bar b}\simeq 600GeV at the Tevatron is expected.Comment: 35 pages, 7 fig
Vertex Displacements for Acausal Particles: Testing the Lee-Wick Standard Model at the LHC
We propose to search for wrong displaced vertices, where decay products of
the secondary vertex move towards the primary vertex instead of away from it,
as a signature for microscopic violation of causality. We analyze in detail the
leptonic sector of the recently proposed Lee-Wick Standard Model, which
provides a well motivated framework to study acausal effects. We find that,
assuming Minimal Flavor Violation, the Lee-Wick partners of the electron,
{\tilde l}^e and \tilde e, can produce measurable wrong vertices at the LHC,
the most promising channel being q \bar{q} --> \bar{\tilde l}^e {\tilde l}^e
--> e^+ e^- jjjj. A Monte-Carlo simulation using MadGraph/MadEvent suggests
that for M_l < 450 GeV the measurement of these acausal vertex displacements
should be accessible in the LHC era.Comment: 29 pages, 7 figures, minor changes, published versio
Beautiful mirrors for a pNGB Higgs
We consider one of the most significant deviations from the Standard Model:
the forward-backward asymmetry of the b-quark measured at leptonic colliders.
We investigate the possibility to solve this discrepancy by introducing new
physics at the TeV scale. We focus on models where the Higgs is a pseudo
Nambu-Goldstone boson of a new strongly coupled sector with a global SO(5)
symmetry broken spontaneously to SO(4). Besides the usual top partners, we
introduce bottom partners in the representations 16 and 4 of SO(5) and show
that they can improve significantly the fit by correcting the Zbb couplings. We
also estimate the corrections to the couplings at one-loop and obtain that the
tree-level ones dominate and can give a reliable estimation. We find that the
large shift required for Zb_Rb_R leads to light custodians associated to the
b-quark, similar to the top partners, as well as a rich phenomenology involving
neutral interactions in the bottom-sector.Comment: 31 pages, 2 figure
Composite Higgs and leptoquarks from a simple group
We propose a composite grand unified theory to study the anomalies in the
semileptonic decays. We show a simple group containing the custodial and
Standard Model gauge symmetries, that can deliver a set of composite pseudo
Nambu-Goldstone bosons: the Higgs, a colorless SU(2)-fourplet and three
leptoquarks: a triplet and two doublets. We give a description in terms of an
effective theory of resonances. By assuming anarchic partial compositeness of
the Standard Model fermions, we find representations for the composite fermions
that allow to obtain the Higgs Yukawa couplings, as well as leptoquark
interactions explaining the deviations in . We calculate
the one-loop potential, we show that it can trigger electroweak symmetry
breaking and we find a region of the parameter space that can reproduce the
Standard Model spectrum. The model predicts leptoquark masses of order
TeV, corrections to some electroweak observables, with
saturating the current bounds, and a very reach phenomenology at LHC. We also
study the possibility of explaining .Comment: 36 pages, 4 figures, v2: typos corrected, references adde
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