634 research outputs found
Quantum corrections to the spin-independent cross section of the inert doublet dark matter
The inert Higgs doublet model contains a stable neutral boson as a candidate
of dark matter. We calculate cross section for spin-independent scattering of
the dark matter on nucleon. We take into account electroweak and scalar quartic
interactions, and evaluate effects of scattering with quarks at one-loop level
and with gluon at two-loop level. These contributions give an important effect
for the dark matter mass to be around m_h/2, because a coupling with the
standard model Higgs boson which gives the leading order contribution should be
suppressed to reproduce the correct amount of the thermal relic abundance in
this mass region. In particular, we show that the dark matter self coupling
changes the value of the spin-independent cross section significantly.Comment: 38 pages, 18 figure
Muon specific two-Higgs-doublet model
We investigate a new type of a two-Higgs-doublet model as a solution of the
muon anomaly. We impose a softly-broken symmetry to forbid tree
level flavor changing neutral currents in a natural way. This symmetry
restricts the structure of Yukawa couplings. As a result, extra Higgs boson
couplings to muons are enhanced by a factor of , while their
couplings to all the other standard model fermions are suppressed by
. Thanks to this coupling property, we can avoid the constraint from
leptonic decays in contrast to the lepton specific two-Higgs-doublet
model, which can explain the muon within the 2 level but cannot
within the level due to this constraint. We find that the model can
explain the muon within the 1 level satisfying constraints from
perturbative unitarity, vacuum stability, electroweak precision measurements,
and current LHC data.Comment: 24 pages, 3 figure
Chiral phase transition of bulk Abelian gauge theories in the Randall-Sundrum brane world
The chiral phase transition of strong-coupling Abelian gauge theories is
investigated in the brane world. It is assumed that gauge boson propagates in
an extra dimension, i.e. bulk gauge theories. The phase structure is
analytically evaluated by using the low-energy effective theories. We also
numerically solve the ladder Schwinger-Dyson equation for the full fermion
propagator including Kaluza-Klein (KK) excitation modes of the gauge field. It
is found that the chiral phase transition is of the second order, and the
critical value of the coupling constant is obtained. The extra dimension has a
large influence on the chiral phase transition for the Randall-Sundrum (RS)
brane world. It is studied how the number of KK modes affect the chiral phase
transition.Comment: 18 pages, 7 figures, REVTe
Dynamical Fermion Masses Under the Influence of Kaluza-Klein Fermions in Randall-Sundrum Background
The dynamical fermion mass generation on the D3-brane in the Randall-Sundrum
space-time is discussed in a model with bulk fermions in interaction with
fermions on the branes. It is found that the dynamical fermion masses are
generated at the natural (R.-S.) radius of the compactified extra space and may
be made small compared with masses of the Kaluza-Klein modes which is of order
of TeV.Comment: 10 pages, 4 figures, REVTeX; footnote added in section 4, new
references adde
Model independent evaluation of the Wilson coefficient of the Weinberg operator in QCD
We derive a Wilson coefficient of a CP-violating purely gluonic dimension-6
operator called the Weinberg operator () generated by a scalar and
two fermions at the two-loop level. We do not specify the representation of
SU(3) for the scalar and the fermions, and thus our result can be applied
to a variety of models beyond the standard model. We estimate the nucleon EDMs
induced by the Weinberg operator in some examples and discuss the importance of
measuring EDMs. It is found that future measurements of the EDMs can probe
physics at higher energy scale beyond the reach of collider experiments.Comment: 22 pages, 7 figures; v2: version accepted by JHEP; v3: Eq. (4.2) is
added, Table 1 is extende
Loop corrections to dark matter direct detection in a pseudoscalar mediator dark matter model
If dark matter (DM) is a fermion and its interactions with the standard model
particles are mediated by pseudoscalar particles, the tree-level amplitude for
the DM-nucleon elastic scattering is suppressed by the momentum transfer in the
non-relativistic limit. At the loop level, on the other hand, the
spin-independent contribution to the cross section appears without such
suppression. Thus, the loop corrections are essential to discuss the
sensitivities of the direct detection experiments for the model prediction. The
one-loop corrections were investigated in the previous works. However, the
two-loop diagrams give the leading order contribution to the DM-gluon effective
operator () and have not been
correctly evaluated yet. Moreover, some interaction terms which affect the
scattering cross section were overlooked. In this paper, we show the cross
section obtained by the improved analysis and discuss the region where the
cross section becomes large.Comment: 34 pages, 11 figures, 6 tables, the version published in JHE
Prospects for Spin-1 Resonance Search at 13 TeV LHC and the ATLAS Diboson Excess
Motivated by ATLAS diboson excess around 2 TeV, we investigate a
phenomenology of spin-1 resonances in a model where electroweak sector in the
SM is weakly coupled to strong dynamics. The spin-1 resonances, W' and Z', are
introduced as effective degrees of freedom of the dynamical sector. We explore
several theoretical constraints by investigating the scalar potential of the
model as well as the current bounds from the LHC and precision measurements. It
is found that the main decay modes are V' -> VV and V' -> Vh, and the V' width
is narrow enough so that the ATLAS diboson excess can be explained. In order to
investigate future prospects, we also perform collider simulations at the 13
TeV LHC, and obtain a model independent expected exclusion limit for the
process pp -> W' -> WZ -> JJ. We find a parameter space where the diboson
excess can be explained, and are within a reach of the LHC at the integrated
luminosity of 10 fb-1 and 13 TeV.Comment: 38 pages, 19 figures, 1 table; minor changes, references added,
version published in JHE
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