A natural SUSY Higgs near 125 GeV Hall, Lawrence J.; Pinner, David; Ruderman, Joshua T.
The journal of high energy physics,
04/2012, Letnik:
2012, Številka:
4
Journal Article
Recenzirano
Odprti dostop
A
bstract
The naturalness of a Higgs boson with a mass near 125 GeV is explored in a variety of weak-scale supersymmetric models. A Higgs mass of this size strongly points towards a non-minimal ...implementation of supersymmetry. The Minimal Supersymmetric Standard Model now requires large
A
-terms to avoid multi-TeV stops. The fine-tuning is at least 1 % for low messenger scales, and an order of magnitude worse for high messenger scales. Naturalness is significantly improved in theories with a singlet superfield
S
coupled to the Higgs superfields via λ
SH
u
H
d
. If λ is perturbative up to unified scales, a fine-tuning of about 10 % is possible with a low mediation scale. Larger values of λ, implying new strong interactions below unified scales, allow for a highly natural 125 GeV Higgs boson over a wide range of parameters. Even for λ as large as 2, where a heavier Higgs might be expected, a light Higgs boson naturally results from singlet-doublet scalar mixing. Although the Higgs is light, naturalness allows for stops as heavy as 1.5 TeV and a gluino as heavy as 3 TeV. Non-decoupling effects among the Higgs doublets can significantly suppress the coupling of the light Higgs to
b
quarks in theories with a large λ, enhancing the γγ and
W W
signal rates at the LHC by an order one factor relative to the Standard Model Higgs.
CHAMP cosmic rays Dunsky, David; Hall, Lawrence J.; Harigaya, Keisuke
Journal of cosmology and astroparticle physics,
07/2019, Letnik:
2019, Številka:
7
Journal Article
Recenzirano
Odprti dostop
We study interactions of cosmological relics, X, of mass m and electric charge qe in the galaxy, including thermalization with the interstellar medium, diffusion through inhomogeneous magnetic fields ...and Fermi acceleration by supernova shock waves. We find that for m≲1010q GeV, there is a large flux of accelerated X in the disk today, with a momentum distribution ∝1/p2.5 extending to (βp)max∼5×104q GeV. Even though acceleration in supernova shocks is efficient, ejecting X from the galaxy, X are continually replenished by diffusion into the disk from the halo or confinement region. For m≳1010q GeV, X cannot be accelerated above the escape velocity within the lifetime of the shock. The accelerated X form a component of cosmic rays that can easily reach underground detectors, as well as deposit energies above thresholds, enhancing signals in various experiments. We find that nuclear/electron recoil experiments place very stringent bounds on X at low q; for example, X as dark matter is excluded for q>10−9 and m<105 GeV. For larger q or m, stringent bounds on the fraction of dark matter that can be X are set by Cherenkov and ionization detectors. Nevertheless, very small q is highly motivated by the kinetic mixing portal, and we identify regions of (m,q) that can be probed by future experiments.
Spread Supersymmetry Hall, Lawrence J.; Nomura, Yasunori
The journal of high energy physics,
01/2012, Letnik:
2012, Številka:
1
Journal Article
Recenzirano
Odprti dostop
A
bstract
In the multiverse the scale of supersymmetry breaking,
∗
, may scan and environmental constraints on the dark matter density may exclude a large range of
m
from the reheating temperature ...after inflation down to values that yield a lightest supersymmetric particle (LSP) mass of order a TeV. After selection effects, for example from the cosmological constant, the distribution for
in the region that gives a TeV LSP may prefer larger values. A single environmental constraint from dark matter can then lead to multi-component dark matter, including both axions and the LSP, giving a TeV-scale LSP somewhat lighter than the corresponding value for single-component LSP dark matter.
If supersymmetry breaking is mediated to the Standard Model sector at order
X
†
X
and higher, only squarks, sleptons and one Higgs doublet acquire masses of order
. The gravitino mass is lighter by a factor of
M
∗
/M
Pl
and the gaugino masses are suppressed by a further loop factor. This Spread Supersymmetry spectrum has two versions, one with Higgsino masses arising from supergravity effects of order the gravitino mass giving a wino LSP, and another with the Higgsino masses generated radiatively from gaugino masses giving a Higgsino LSP. The environmental restriction on dark matter fixes the LSP mass to the TeV domain, so that the squark and slepton masses are order 10
3
TeV and 10
6
TeV in these two schemes. We study the spectrum, dark matter and collider signals of these two versions of Spread Supersymmetry. The Higgs boson is Standard Model-like and predicted to lie in the range 110-145 GeV; monochromatic photons in cosmic rays arise from dark matter annihilations in the halo; exotic short charged tracks occur at the LHC, at least for the wino LSP; and there are the eventual possibilities of direct detection of dark matter and detailed exploration of the TeV-scale states at a future linear collider. Gauge coupling unification is at least as precise as in minimal supersymmetric theories.
If supersymmetry breaking is also mediated at order
X
, a much less hierarchical spectrum results. The spectrum in this case is similar to that of the Minimal Supersymmetric Standard Model, but with the superpartner masses 1-2 orders of magnitude larger than those expected in natural theories.
A
bstract
The standard model Higgs quartic coupling vanishes at (10
9
− 10
13
) GeV. We study SU(2)
L
×
SU(2)
R
×
U(1)
B−L
theories that incorporate the Higgs Parity mechanism, where this becomes the ...scale of Left-Right symmetry breaking,
v
R
. Furthermore, these theories solve the strong CP problem and predict three right-handed neutrinos. We introduce cosmologies where SU(2)
R
×
U(1)
B−L
gauge interactions produce right-handed neutrinos via the freeze-out or freeze-in mechanisms. In both cases, we find the parameter space where the lightest right-handed neutrino is dark matter and the decay of a heavier one creates the baryon asymmetry of the universe via leptogenesis. A theory of flavor is constructed that naturally accounts for the lightness and stability of the right-handed neutrino dark matter, while maintaining sufficient baryon asymmetry. The dark matter abundance and successful natural leptogenesis require
v
R
to be in the range (10
10
−
10
13
) GeV for freeze-out, in remarkable agreement with the scale where the Higgs quartic coupling vanishes, whereas freeze-in requires
v
R
≳ 10
9
GeV. The allowed parameter space can be probed by the warmness of dark matter, precise determinations of the top quark mass and QCD coupling by future colliders and lattice computations, and measurement of the neutrino mass hierarchy.
A
bstract
The strong CP problem is solved in Parity symmetric theories, with the electroweak gauge group containing SU(2)
L
× SU(2)
R
broken by the minimal set of Higgs fields. Neutrino masses may be ...explained by adding the same number of gauge singlet fermions as the number of generations. The neutrino masses vanish at tree-level and are only radiatively generated, leading to larger couplings of right-handed neutrinos to Standard Model particles than with the tree-level seesaw mechanism. We compute these radiative corrections and the mixing angles between left- and right-handed neutrinos. We discuss sensitivities to these right-handed neutrinos from a variety of future experiments that search for heavy neutral leptons with masses from tens of MeV to the multi-TeV scale.
A
bstract
SU(2)
L
×
SU(2)
R
gauge symmetry requires three right-handed neutrinos (
N
i
), one of which,
N
1
, can be sufficiently stable to be dark matter. In the early universe,
W
R
exchange with ...the Standard Model thermal bath keeps the right-handed neutrinos in thermal equilibrium at high temperatures.
N
1
can make up all of dark matter if they freeze-out while relativistic and are mildly diluted by subsequent decays of a long-lived and heavier right-handed neutrino,
N
2
. We systematically study this parameter space, constraining the symmetry breaking scale of SU(2)
R
and the mass of
N
1
to a triangle in the (
v
R
, M
1
) plane, with
v
R
= (10
6
−
3
×
10
12
) GeV and
M
1
= (2 keV–1 MeV). Much of this triangle can be probed by signals of warm dark matter, especially if leptogenesis from
N
2
decay yields the observed baryon asymmetry. The minimal value of
v
R
is increased to 10
8
GeV for doublet breaking of SU(2)
R
, and further to 10
9
GeV if leptogenesis occurs via
N
2
decay, while the upper bound on
M
1
is reduced to 100 keV. In addition, there is a component of hot
N
1
dark matter resulting from the late decay of
N
2
→ N
1
ℓ
+
ℓ
−
that can be probed by future cosmic microwave background observations. Interestingly, the range of
v
R
allows both precision gauge coupling unification and the Higgs Parity understanding of the vanishing of the Standard Model Higgs quartic at scale
v
R
. Finally, we study freeze-in production of
N
1
dark matter via the
W
R
interaction, which allows a much wider range of (
v
R
,
M
1
).
A
bstract
Using a simplified model framework, we assess observational limits and discovery prospects for neutralino dark matter, taken here to be a general admixture of bino, wino, and Higgsino. ...Experimental constraints can be weakened or even nullified in regions of parameter space near 1) purity limits, where the dark matter is mostly bino, wino, or Higgsino, or 2) blind spots, where the relevant couplings of dark matter to the
Z
or Higgs bosons vanish identically. We analytically identify all blind spots relevant to spin-independent and spin-dependent scattering and show that they arise for diverse choices of relative signs among
M
1
,
M
2
, and
μ
. At present, XENON100 and IceCube still permit large swaths of viable parameter space, including the well-tempered neutralino. On the other hand, upcoming experiments should have sufficient reach to discover dark matter in much of the remaining parameter space. Our results are broadly applicable, and account for a variety of thermal and non-thermal cosmological histories, including scenarios in which neutralinos are just a component of the observed dark matter today. Because this analysis is indifferent to the fine-tuning of electroweak symmetry breaking, our findings also hold for many models of neutralino dark matter in the MSSM, NMSSM, and Split Supersymmetry. We have identified parameter regions at low tan
β
which sit in a double blind spot for both spin-independent and spin-dependent scattering. Interestingly, these low tan
β
regions are independently favored in the NMSSM and models of Split Supersymmetry which accommodate a Higgs mass near 125 GeV.
Freeze-in production of FIMP dark matter Hall, Lawrence J.; Jedamzik, Karsten; March-Russell, John ...
The journal of high energy physics,
03/2010, Letnik:
2010, Številka:
3
Journal Article
Recenzirano
Odprti dostop
We propose an alternate, calculable mechanism of dark matter genesis, “thermal freeze-in”, involving a Feebly Interacting Massive Particle (FIMP) interacting so feebly with the thermal bath that it ...never attains thermal equilibrium. As with the conventional “thermal freeze-out” production mechanism, the relic abundance reflects a combination of initial thermal distributions together with particle masses and couplings that can be measured in the laboratory or astrophysically. The freeze-in yield is IR dominated by low temperatures near the FIMP mass and is independent of unknown UV physics, such as the reheat temperature after inflation. Moduli and modulinos of string theory compactifications that receive mass from weak-scale supersymmetry breaking provide implementations of the freeze-in mechanism, as do models that employ Dirac neutrino masses or GUT-scale-suppressed interactions. Experimental signals of freeze-in and FIMPs can be spectacular, including the production of new metastable coloured or charged particles at the LHC as well as the alteration of big bang nucleosynthesis.
Lepto-axiogenesis Co, Raymond T.; Fernandez, Nicolas; Ghalsasi, Akshay ...
The journal of high energy physics,
1/3, Letnik:
2021, Številka:
3
Journal Article
Recenzirano
Odprti dostop
A
bstract
We propose a baryogenenesis mechanism that uses a rotating condensate of a Peccei-Quinn (PQ) symmetry breaking field and the dimension-five operator that gives Majorana neutrino masses. The ...rotation induces charge asymmetries for the Higgs boson and for lepton chirality through sphaleron processes and Yukawa interactions. The dimension-five interaction transfers these asymmetries to the lepton asymmetry, which in turn is transferred into the baryon asymmetry through the electroweak sphaleron process. QCD axion dark matter can be simultaneously produced by dynamics of the same PQ field via kinetic misalignment or parametric resonance, favoring an axion decay constant
f
a
≲ 10
10
GeV, or by conventional misalignment and contributions from strings and domain walls with
f
a
∼ 10
11
GeV. The size of the baryon asymmetry is tied to the mass of the PQ field. In simple supersymmetric theories, it is independent of UV parameters and predicts the supersymmtry breaking mass scale to be
O
(10
−
10
4
) TeV, depending on the masses of the neutrinos and whether the condensate is thermalized during a radiation or matter dominated era. The high supersymmetry breaking mass scale may be free from cosmological and flavor/CP problems. We also construct a theory where TeV scale supersymmetry is possible. Parametric resonance may give warm axions, and the radial component of the PQ field may give signals in rare kaon decays from mixing with the Higgs and in dark radiation.
Axion cold dark matter from standard misalignment typically requires a decay constant fa≳1011 GeV . Kinetic misalignment and parametric resonance easily allow lower values of fa when the radial ...Peccei-Quinn (PQ) symmetry breaking field takes large initial values. Here, we consider the effects of inflation on kinetic misalignment and parametric resonance. We assume that the initial PQ field value is determined by quantum fluctuations, and is set by the Hubble parameter during inflation, HI, and the PQ field mass. PQ field oscillations begin before or after the completion of reheating after inflation at a temperature TR. We determine the range of fa and the inflationary parameters (HI,TR) consistent with axion dark matter for a quartic potential for the PQ field. We find that 108 GeV <fa<1011 GeV can consistently produce axion dark matter. A significant portion of the allowed parameter space predicts rare kaon decays, KL→(π0+missingenergy), and/or suppression of structure formation on small scales.
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