40,954 research outputs found
Singlet Model Interference Effects with High Scale UV Physics
One of the simplest extensions of the Standard Model (SM) is the addition of
a scalar gauge singlet, S. If S is not forbidden by a symmetry from mixing with
the Standard Model Higgs boson, the mixing will generate non-SM rates for Higgs
production and decays. In general, there could also be unknown high energy
physics that generates additional effective low energy interactions. We show
that interference effects between the scalar resonance of the singlet model and
the effective field theory (EFT) operators can have significant effects in the
Higgs sector. We examine a non- symmetric scalar singlet model and
demonstrate that a fit to the 125 GeV Higgs boson couplings and to limits on
high mass resonances, S, exhibit an interesting structure and possible large
cancellations of effects between the resonance contribution and the new EFT
interactions, that invalidate conclusions based on the renormalizable singlet
model alone.Comment: 18 pages, 7 figures; revised to emphasize the points of general
interest for heavy resonance searches at the LH
Exploring Resonant di-Higgs production in the Higgs Singlet Model
We study the enhancement of the di-Higgs production cross section resulting
from the resonant decay of a heavy Higgs boson at hadron colliders in a model
with a Higgs singlet. This enhancement of the double Higgs production rate is
crucial in understanding the structure of the scalar potential and we determine
the maximum allowed enhancement such that the electroweak minimum is a global
minimum. The di-Higgs production enhancement can be as large as a factor of ~
18 (13) for the mass of the heavy Higgs around 270 (420) GeV relative to the
Standard Model rate at 14 TeV for parameters corresponding to a global
electroweak minimum.Comment: 25 pages, 14 figures. Version approved for publication. Discussion of
Z2 symmetric limit improved and references adde
Top Partners and Higgs Boson Production
The Higgs boson is produced at the LHC through gluon fusion at roughly the
Standard Model rate. New colored fermions, which can contribute to
, must have vector-like interactions in order not to be in
conflict with the experimentally measured rate. We examine the size of the
corrections to single and double Higgs production from heavy vector-like
fermions in singlets and doublets and search for regions of parameter
space where double Higgs production is enhanced relative to the Standard Model
prediction. We compare production rates and distributions for double Higgs
production from gluon fusion using an exact calculation, the low energy theorem
(LET), where the top quark and the heavy vector-like fermions are taken to be
infinitely massive, and an effective theory (EFT) where top mass effects are
included exactly and the effects of the heavy fermions are included to . Unlike the LET, the EFT gives an extremely accurate description
of the kinematic distributions for double Higgs production.Comment: 37 pages, 11 figures. Minor changes to Figs. 8-1
Position and Momentum Uncertainties of the Normal and Inverted Harmonic Oscillators under the Minimal Length Uncertainty Relation
We analyze the position and momentum uncertainties of the energy eigenstates
of the harmonic oscillator in the context of a deformed quantum mechanics,
namely, that in which the commutator between the position and momentum
operators is given by [x,p]=i\hbar(1+\beta p^2). This deformed commutation
relation leads to the minimal length uncertainty relation \Delta x >
(\hbar/2)(1/\Delta p +\beta\Delta p), which implies that \Delta x ~ 1/\Delta p
at small \Delta p while \Delta x ~ \Delta p at large \Delta p. We find that the
uncertainties of the energy eigenstates of the normal harmonic oscillator
(m>0), derived in Ref. [1], only populate the \Delta x ~ 1/\Delta p branch. The
other branch, \Delta x ~ \Delta p, is found to be populated by the energy
eigenstates of the `inverted' harmonic oscillator (m<0). The Hilbert space in
the 'inverted' case admits an infinite ladder of positive energy eigenstates
provided that \Delta x_{min} = \hbar\sqrt{\beta} > \sqrt{2}
[\hbar^2/k|m|]^{1/4}. Correspondence with the classical limit is also
discussed.Comment: 16 pages, 31 eps figure
Lensed CMB power spectra from all-sky correlation functions
Weak lensing of the CMB changes the unlensed temperature anisotropy and
polarization power spectra. Accounting for the lensing effect will be crucial
to obtain accurate parameter constraints from sensitive CMB observations.
Methods for computing the lensed power spectra using a low-order perturbative
expansion are not good enough for percent-level accuracy. Non-perturbative
flat-sky methods are more accurate, but curvature effects change the spectra at
the 0.3-1% level. We describe a new, accurate and fast, full-sky
correlation-function method for computing the lensing effect on CMB power
spectra to better than 0.1% at l<2500 (within the approximation that the
lensing potential is linear and Gaussian). We also discuss the effect of
non-linear evolution of the gravitational potential on the lensed power
spectra. Our fast numerical code is publicly available.Comment: 16 pages, 4 figures. Changes to match PRD version including new
section on non-linear corrections. CAMB code available at http://camb.info
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