55038482
Scalar suppression on large scales in open inflation
We consider two toy models of open inflation and investigate their ability to give a suppression of scalar power on large scales while also satisfying observational constraints on the spatial curvature of the Universe. Qualitatively we find that both models are indeed capable of fulfilling these two requirements, but we also see that effects of the quantum tunneling must be carefully taken into account if we wish to make quantitative predictions.
55981517
Hawking-Moss instanton in nonlinear massive gravity
As a first step toward understanding a lanscape of vacua in a theory of non-linear massive gravity, we consider a landscape of a single scalar field and study tunneling between a pair of adjacent vacua. We study the Hawking-Moss (HM) instanton that sits at a local maximum of the potential, and evaluate the dependence of the tunneling rate on the parameters of the theory. It is found that provided with the same physical HM Hubble parameter HHM, depending on the values of parameters ?3 and ?4 in the action (2.2), the corresponding tunneling rate can be either enhanced or suppressed when compared to the one in the context of General Relativity (GR). Furthermore, we find the constraint on the ratio of the physical Hubble parameter to the fiducial one, which constrains the form of potential. This result is in sharp contrast to GR where there is no bound on the minimum value of the potential.
67813587
Screening of cosmological constant in non-local cosmology
We consider a model of non-local gravity with a large bare cosmological constant, Λ, and study its cosmological solutions. The model is characterized by a function f(ψ) = f0eαψ, where ψ = □-1R and α is a real dimensionless parameter. In the absence of matter, we find an expanding universe solution a ∝ tn with n αcr ≈ 0.17. This is quite a weak condition. We argue that the solution is stable against the inclusion of matter fields. Thus our solution opens up new possibilities for solution to the cosmological constant problem.
119273109
LHC accessible second Higgs boson in the left-right model
A second Higgs doublet arises naturally as a parity partner of the standard model (SM) Higgs, once SM is extended to its left-right symmetric version (LRSM) to understand the origin of parity violation in weak interactions as well as to accommodate small neutrino masses via the seesaw mechanism. The flavor changing neutral Higgs (FCNH) effects in the minimal version of this model (LRSM), however, push the second Higgs mass to more than 15 TeV making it inaccessible at the LHC. Furthermore since the second Higgs mass is directly linked to the $W_R$ mass, discovery of a "low" mass $W_R$ ($M_{W_R}\leq 5-6$ TeV) at the LHC would require values for some Higgs self couplings larger than one. In this paper we present an extension of LRSM by adding a vector-like $SU(2)_R$ quark doublet which weakens the FCNH constraints allowing the second Higgs mass to be near or below TeV and a third neutral Higgs below 3 TeV for a $W_R$ mass below 5 TeV. It is then possible to search for these heavier Higgs bosons at the LHC, without conflicting with FCNH constraints. A right handed $W_R$ mass in the few TeV range is quite natural in this class of models without having to resort to large scalar coupling parameters. The CKM mixings are intimately linked to the vector-like quark mixings with the known quarks, which is the main reason why the constraints on the second Higgs mass is relaxed. We present a detailed theoretical and phenomenological analysis of this extended LR model and point out some tests as well as its potential for discovery of a second Higgs at the LHC. Two additional features of the model are: (i) a 5/3 charged quark and (ii) a fermionic top partner with masses in the TeV range.
118558798
A possible NN*(1440) quasi-molecular state
Inspired by the recent observation of a narrow resonance-like structure around 2360 MeV in the pn → dπ0π0 cross section, the possibility of forming a NN*(1440) quasi-molecular state is investigated by using a meson exchange model in which the π, σ, ρ and ω exchanges in t- and u-channels are considered. By adopting the coupling constants extracted from the relevant NN scattering and N*(1440) decay data, it is found that a deuteron-like quasi-molecular state of NN*(1440) with a binding energy in the range of 2 ∼ 67 MeV can be formed. Therefore, it is speculated that the observed structure around 2360 MeV might be or may have a large component of the NN*(1440) quasi-molecular state.
119177672
Pair production of heavy quarkonium and B(*)c mesons at hadron colliders
We investigate the pair production of S-wave heavy quarkonium at the LHC in the color-singlet mechanism (CSM) and estimate the contribution from the gluon fragmentation process in the color-octet mechanism (COM) for comparison. With the matrix elements extracted previously in the leading-order calculations, the numerical results show that the production rates are quite large for the pair production processes at the LHC. The p t distribution of double J/ψ production in the CSM is dominant over that in the COM when p t is smaller than about 10 GeV. For the production of double Y, the contribution of the COM is always larger than that in the CSM. The large differences in the theoretical predictions between the CSM and COM for the p t distributions in the large p t region are useful in clarifying the effects of COM on the quarkonium production. We also investigate the pair production of S-wave B c and B* c mesons, and the measurement of these processes is useful to test the CSM and extract the long-distance matrix elements for the B c and B* c mesons. Aside from numerical calculations, analytical expressions for the production differential cross sections of all these processes are also given.
30742433
Yukawa bound states of a large number of fermions
A bstractWe consider the bound state problem for a field theory that contains a Dirac fermion χ that Yukawa couples to a (light) scalar field ϕ. We are interested in bound states with a large number N of χ particles. A Fermi gas model is used to numerically determine the dependence of the radius R of these bound states on N and also the dependence of the binding energy on N. Since scalar interactions with relativistic χ’s are suppressed two regimes emerge. For modest values of N the state is composed of non-relativistic χ particles. In this regime as N increases R decreases. Eventually the core region becomes relativistic and the size of the state starts to increase as N increases. As a result, for fixed Yukawa coupling and χ mass, there is a minimum sized state that occurs roughly at the value of N where the core region first becomes relativistic. We also compute an elastic scattering form factor that can be relevant for direct detection if the dark matter is composed of such χ particles.
119306471
Inert Doublet Dark Matter and Mirror/Extra Families after Xenon100
J. Stefan Institute, Ljubljana, Slovenia(Dated: May 31, 2011)It was shown recently that mirror fermions, naturally present in a number of directions for newphysics, seem to require an inert scalar doublet in order to pass the electroweak precision tests.This provides a further motivation for considering the inert doublet as a dark matter candidate.Moreover, the presence of extra families enhances the Standard Model Higgs-nucleon coupling, whichhas crucial impact on the Higgs and dark matter searches. We study the limits on the inert darkmatter mass in view of recent Xenon100 data. We nd that the mass of the inert dark mattermust lie in a very narrow window 75 1GeV while the Higgs must weigh more than 400GeV. Forthe sake of completeness we discuss the cases with fewer extra families, where the possibility ofa light Higgs boson opens up, enlarging the dark matter mass window to