A
bstract
A
Z
2
symmetry that extends the weak interaction, SU(2)
L
→ SU(2)
L
×SU(2)
′
, and the Higgs sector,
H
(2) →
H
(2
,
1) +
H
′
(1
,
2), yields a Standard Model quartic coupling that vanishes ...at scale
v
′
= 〈
H
′
〉 ≫ 〈
H
〉. Near
v
′
, theories either have a “prime” sector, or possess “Left-Right” (LR) symmetry with SU(2)
′
= SU(2)
R
. If the
Z
2
symmetry incorporates spacetime parity, these theories can solve the strong CP problem. The LR theories have all quark and lepton masses arising from operators of dimension 5 or more, requiring Froggatt-Nielsen structures. Two-loop contributions to
θ
¯
are estimated and typically lead to a neutron electric dipole moment of order 10
−27
e cm that can be observed in future experiments. Minimal models, with gauge group SU(3) × SU(2)
L
× SU(2)
L
× U(1)
B
−
L
, have precise gauge coupling unification for
v
′
= 10
10±1
GeV, successfully correlating gauge unification with the observed Higgs mass of 125 GeV. With SU(3) × U(1)
B
−
L
embedded in SU(4), the central value of the unification scale is reduced from 10
16−17
GeV to below 10
16
GeV, improving the likelihood of proton decay discovery. Unified theories based on SO(10) ×
CP
are constructed that have
H
+
H
′
in a
16
or
144
and generate higher-dimensional flavor operators, while maintaining perturbative gauge couplings.
Minimal mirror twin Higgs Barbieri, Riccardo; Hall, Lawrence J.; Harigaya, Keisuke
The journal of high energy physics,
11/2016, Letnik:
2016, Številka:
11
Journal Article
Recenzirano
Odprti dostop
A
bstract
In a Mirror Twin World with a maximally symmetric Higgs sector the little hierarchy of the Standard Model can be significantly mitigated, perhaps displacing the cutoff scale above the LHC ...reach. We show that consistency with observations requires that the
Z
2
parity exchanging the Standard Model with its mirror be broken in the Yukawa couplings. A minimal such effective field theory, with this sole
Z
2
breaking, can generate the
Z
2
breaking in the Higgs sector necessary for the Twin Higgs mechanism. The theory has constrained and correlated signals in Higgs decays, direct Dark Matter Detection and Dark Radiation, all within reach of foreseen experiments, over a region of parameter space where the fine-tuning for the electroweak scale is 10-50%. For dark matter, both mirror neutrons and a variety of self-interacting mirror atoms are considered. Neutrino mass signals and the effects of a possible additional
Z
2
breaking from the vacuum expectation values of
B
−
L
breaking fields are also discussed.
In the conventional misalignment mechanism, the axion field has a constant initial field value in the early Universe and later begins to oscillate. We present an alternative scenario where the axion ...field has a nonzero initial velocity, allowing an axion decay constant much below the conventional prediction from axion dark matter. This axion velocity can be generated from explicit breaking of the axion shift symmetry in the early Universe, which may occur as this symmetry is approximate.
A
bstract
Adding an axion-like particle (ALP) to the Standard Model, with a field velocity in the early universe, simultaneously explains the observed baryon and dark matter densities. This requires ...one or more couplings between the ALP and photons, nucleons, and/or electrons that are predicted as functions of the ALP mass. These predictions arise because the ratio of dark matter to baryon densities is independent of the ALP field velocity, allowing a correlation between the ALP mass,
m
a
, and decay constant,
f
a
. The predicted couplings are orders of magnitude larger than those for the QCD axion and for dark matter from the conventional ALP misalignment mechanism. As a result, this scheme, ALP cogenesis, is within reach of future experimental ALP searches from the lab and stellar objects, and for dark matter.
Higgs Parity grand unification Hall, Lawrence J.; Harigaya, Keisuke
The journal of high energy physics,
11/2019, Letnik:
2019, Številka:
11
Journal Article
Recenzirano
Odprti dostop
A
bstract
The vanishing of the Higgs quartic coupling of the Standard Model at high energies may be explained by spontaneous breaking of Higgs Parity. Taking Higgs Parity to originate from the ...Left-Right symmetry of the SO(10) gauge group, leads to a new scheme for precision gauge coupling unification that is consistent with proton decay. We compute the relevant running of couplings and threshold corrections to allow a precise correlation among Standard Model parameters. The scheme has a built-in solution for obtaining a realistic value for
m
b
/m
τ
, which further improves the precision from gauge coupling unification, allowing the QCD coupling constant to be predicted to the level of 1% or, alternatively, the top quark mass to 0.2%. Future measurements of these parameters may significantly constrain the detailed structure of the theory. We also study an SO(10) embedding of quark and lepton masses, showing how large neutrino mixing is compatible with small quark mixing, and predict a normal neutrino mass hierarchy. The strong CP problem may be explained by combining Higgs Parity with space-time parity.
A
bstract
We consider two copies of the Standard Model, interchanged by an exact parity symmetry,
P
. The observed fermion mass hierarchy is described by suppression factors
ϵ
n
i
for charged fermion
...i
, as can arise in Froggatt-Nielsen and extra-dimensional theories of flavor. The corresponding flavor factors in the mirror sector are
ϵ
′
n
i
, so that spontaneous breaking of the parity
P
arises from a single parameter ϵ′/ϵ, yielding a tightly constrained version of Minimal Mirror Twin Higgs, introduced in our previous paper. Models are studied for simple values of
n
i
, including in particular one with SU(5)-compatibility, that describe the observed fermion mass hierarchy. The entire mirror quark and charged lepton spectrum is broadly predicted in terms of ϵ′/ϵ, as are the mirror QCD scale and the decoupling temperature between the two sectors. Helium-, hydrogen- and neutron-like mirror dark matter candidates are constrained by self-scattering and relic ionization. In each case, the allowed parameter space can be fully probed by proposed direct detection experiments. Correlated predictions are made as well for the Higgs signal strength and the amount of dark radiation.
The QCD axion is a good dark matter candidate. The observed dark matter abundance can arise from misalignment or defect mechanisms, which generically require an axion decay constant f_{a}∼O(10^{11}) ...GeV (or higher). We introduce a new cosmological origin for axion dark matter, parametric resonance from oscillations of the Peccei-Quinn symmetry breaking field, that requires f_{a}∼(10^{8}-10^{11}) GeV. The axions may be warm enough to give deviations from cold dark matter in large scale structure.
An exact parity replicates the Standard Model giving a Mirror Standard Model, SM
↔
SM
′
. This “Higgs Parity” and the mirror electroweak symmetry are spontaneously broken by the mirror Higgs, 〈
H
′
〉 ...=
v
′
≫ 〈
H
〉, yielding the Standard Model Higgs as a Pseudo-Nambu-Goldstone Boson of an approximate SU (4) symmetry, with a quartic coupling
λ
SM
(
v
′
)
∼
10
−
3
. Mirror electromagnetism is unbroken and dark matter is composed of
e
′
and
e
¯
′
. Direct detection may be possible via the kinetic mixing portal, and in unified theories this rate is correlated with the proton decay rate. With a high reheat temperature after inflation, the
e
t
dark matter abundance is determined by freeze-out followed by dilution from decays of mirror neutrinos,
ν
′
→ ℓH
. Remarkably, this requires
v
′
∼
(10
8
–10
10
) GeV, predicting a Higgs mass of 123
±
3 GeV at 1
σ
and a Standard Model neutrino mass of (10
−
2
–10
−
1
) eV, consistent with observed neutrino masses. The mirror QCD sector exhibits a first order phase transition producing gravitational waves that may be detected by future observations. Mirror glueballs decay to mirror photons giving dark radiation with ∆
N
eff
∼
0
.
03–0
.
4. With a low reheat temperature after inflation, the
e
′
dark matter abundance is determined by freeze-in from the SM sector by either the Higgs or kinetic mixing portal.
A
bstract
Rotations of an axion field in field space provide a natural origin for an era of kination domination, where the energy density is dominated by the kinetic term of the axion field, preceded ...by an early era of matter domination. Remarkably, no entropy is produced at the end of matter domination and hence these eras of matter and kination domination may occur even after Big Bang Nucleosynthesis. We derive constraints on these eras from both the cosmic microwave background and Big Bang Nucleosynthesis. We investigate how this cosmological scenario affects the spectrum of possible primordial gravitational waves and find that the spectrum features a triangular peak. We discuss how future observations of gravitational waves can probe the viable parameter space, including regions that produce axion dark matter by the kinetic misalignment mechanism or the baryon asymmetry by axiogenesis. For QCD axion dark matter produced by the kinetic misalignment mechanism, a modification to the inflationary gravitational wave spectrum occurs above 0.01 Hz and, for high values of the energy scale of inflation, the prospects for discovery are good. We briefly comment on implications for structure formation of the universe.
Higgs Parity, strong CP and dark matter Dunsky, David; Hall, Lawrence J.; Harigaya, Keisuke
The journal of high energy physics,
07/2019, Letnik:
2019, Številka:
7
Journal Article
Recenzirano
Odprti dostop
A
bstract
An exact spacetime parity replicates the SU(2) × U(1) electroweak interaction, the Higgs boson
H
, and the matter of the Standard Model. This “Higgs Parity” and the mirror electroweak ...symmetry are spontaneously broken at scale
v
′ = 〈
H
′ 〉 ≫ 〈
H
〉, yielding the Standard Model below
v
′ with a quartic coupling that essentially vanishes at
v
′:
λ
SM
(
v
′) ∼ 10
−3
. The strong CP problem is solved as Higgs parity forces the masses of mirror quarks and ordinary quarks to have opposite phases. Dark matter is composed of mirror electrons,
e
′, stabilized by unbroken mirror electromagnetism. These interact with Standard Model particles via kinetic mixing between the photon and the mirror photon, which arises at four-loop level and is a firm prediction of the theory. Physics below
v
′, including the mass and interaction of
e
′ dark matter, is described by
one fewer parameter
than in the Standard Model. The allowed range of
m
e
′
is determined by uncertainties in (
α
s
, m
t
, m
h
), so that future precision measurements of these will be correlated with the direct detection rate of
e
′ dark matter, which, together with the neutron electric dipole moment, will probe the entire parameter space.
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