119156542
Axion as a CDM component
I discuss the essential features of the QCD axion: the strong CP solution and hence its theoretical necessity. I also review the effects of the QCD axion on astrophysics and cosmology, in particular with emphasis on its role in the dark matter component together with its supersymmetric partner axino. It is pointed out that string theory may or may not give a detectable QCD axion.
18138135
Neutrino masses from discrete gauge symmetries
Abstract We investigate a model with an extra Z 2 gauge symmetry in the Standard Model. The symmetry gives a structure to the mass matrix for the neutrinos. With two extra Higgs singlets and two extra singlet right-handed neutrinos we can build a model that fits the requirements of the MSW solution of the Solar neutrino problem. With a third singlet right-handed neutrino it is also possible to have a 10 eV neutrino.
14574575
Effective Gauss-Bonnet interaction in Randall-Sundrum compactification
The effective gravitational interaction below the Planck scale in the Randall-Sundrum world is shown to be the Gauss-Bonnet term. In this theory we find that there exists another static solution with a positive bulk cosmological constant. Also, there exist solutions for a positive visible sector cosmological constant, which is needed for a later Friedmann-Robertson-Walker universe.
119316975
GMSB at a stable vacuum and MSSM without exotics from heterotic string
Abstract We show that it is possible to introduce the confining hidden sector gauge group SU ( 5 ) ′ with the chiral matter 10 0 ′ plus 5 ¯ 0 ′ , which are neutral under the standard model gauge group, toward a gauge mediated supersymmetry breaking (GMSB) in a Z 12 − I orbifold compactification of E 8 × E 8 ′ heterotic string. Three families of MSSM result without exotics. We also find a desirable matter parity P (or R-parity) assignment. We note that this model contains the spectrum of the Lee–Weinberg model which has a nice solution of the μ problem.
15739165
SO(10)-like Superstring Standard Model with R-parity from the Heterotic String
We construct a supersymmetric standard model in the context of the Z_{12-I} orbifold compactification of the E_8 x E_8' heterotic string theory. The gauge group is SU(3)_c x SU(2)_L x U(1)_Y x U(1)^4 x [SO(10) x U(1)^3]' with sin^2\theta_W = 3/8. We obtain three families of SO(10) spinor-like chiral matter states, and Higgs doublets. All other extra states are exactly vector-like under the standard model gauge symmetry. There are numerous standard model singlets, many of which get VEVs such that only the standard model gauge symmetry survives and desired Yukawa couplings can be generated at lower energies. In particular, all vector-like exotic states achieve superheavy masses and the R-parity can be preserved.
119883211
Conflicts between B-violating phenomena in supergravity models
Abstract We show that there is an incompatibility between matter stability and cosmological baryon production in standard N = 1 supergravity models. This discrepancy emerges from the bound on the reheating temperature T rh ⩽ 10 10 GeV which comes from the restriction on the gravitino decay after inflation. Some weird possibilities to bypass the controversy are also analyzed.
118455901
CMB data constraint on self-annihilation of dark matter particles
Recently, self‐annihilation of dark matter particles is proposed to explain the “WMAP Haze” and excess of energetic positrons and electrons in ATIC and PAMELA results. If self‐annihilation of dark matter occurs around the recombination of cosmic plasma, energy release from self‐annihilation of dark matter delays the recombination, and hence affects CMB anisotropy. By using the recent CMB data, we have investigated the self‐annihilation of dark matter particles. In this investigation, we do not find statistically significant evidence, and impose an upper bound on 〈σν〉/mϰ.The upcoming data from Planck surveyor and the Fermi Gamma‐ray telescope will allow us to break some of parameter degeneracy and improve constraints on self‐annihilation of dark matter particles.
119172488
Light Stop Searches at the LHC in Events with two b-Jets and Missing Energy
We propose a new method to discover light top squarks (stops) in the co-annihilation region at the Large Hadron Collider (LHC). The bino-like neutralino is the lightest supersymmetric particle (LSP) and the lighter stop is the next-to-LSP. Such scenarios can be consistent with electroweak baryogenesis and also with dark matter constraints. We consider the production of two stops in association with two b-quarks, including pure QCD as well as mixed electroweak-QCD contributions. The stops decay into a charm quark and the LSP. For a higgsino-like light chargino, the electroweak contributions can exceed the pure QCD prediction. We show the size of the electroweak contributions as a function of the stop mass and present the LHC discovery reach in the stop-neutralino mass plane.
118343398
Probing Minimal Flavor Violation with Long-Lived Stops and Light Gravitinos at Hadron Colliders
In the framework of minimal flavor violation (MFV), we discuss the decay properties of a supersymmetric scalar top (stop) in the presence of a light gravitino. Given a small mass difference between the lighter stop and lightest neutralino and an otherwise sufficiently decoupled spectrum, the stop may be long-lived and thus can provide support to MFV at hadron colliders. For a bino-like lightest neutralino, we apply bounds from searches in the gamma gamma plus missing transverse energy channel (ATLAS with 1 fb^-1 and D0 with 6.3 fb^-1) and give a 5 fb^-1 projection for the ATLAS search.
118704767
First LHC Constraints on Neutralinos
Abstract The ATLAS and CMS Collaborations have recently reported tantalizing hints of the existence of a 125 GeV Higgs-like particle, whose couplings appear to match well the Standard Model (SM) expectations. In this work, we study implications of this observation for the neutralino sector of supersymmetric models, assuming that the Higgs signal gets confirmed. In general, the Higgs decay into neutralinos can be one of its dominant decay channels. Since a large invisible Higgs decay branching ratio would be in conflict with the data, this possibility is now constrained. In particular, we find that most of the region μ 170 GeV , M 1 70 GeV at tan β ∼ 10 and μ 120 GeV , M 1 70 GeV at tan β ∼ 40 is disfavored.
119212887
Elliptic genus of E-strings
A bstractWe study a family of 2d N=0,4$$ \mathcal{N}=\left(0,\ 4\right) $$ gauge theories which describes at low energy the dynamics of E-strings, the M2-branes suspended between a pair of M5 and M9 branes. The gauge theory is engineered using a duality with type IIA theory, leading to the D2-branes suspended between an NS5-brane and 8 D8-branes on an O8-plane. We compute the elliptic genus of this family of theories, and find agreement with the known results for single and two E-strings. The partition function can in principle be computed for arbitrary number of E-strings, and we compute them explicitly for low numbers. We test our predictions against the partially known results from topological strings, as well as from the instanton calculus of 5d Sp(1) gauge theory. Given the relation to topological strings, our computation provides the all genus partition function of the refined topological strings on the canonical bundle over 12K3$$ \frac{1}{2}K3 $$.