15426025
Large extra dimension effects on the spin configuration of the top quark pair at e + e − colliders
Large extra dimension effects on the spin configuration of the top quark pair at the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}t\overline{t}$ process are studied. It is shown that the TeV scale quantum gravity effects cause significant deviations from standard model (SM) predictions for the spin configuration in the off-diagonal basis: they lead to substantial cross sections of the like-spin states of the top quark pair, which vanish in the SM; they weaken the pure dominance of the processes, the up-down (down-up) spin states for the left-handed (right-handed) beam. In addition it is shown that the angular cut $\ensuremath{-}0.5l\mathrm{cos}\ensuremath{\theta}l0$ is very effective to determine the sign of the quantum gravity corrections.
16221979
POLARIZATION EFFECTS ON THE E+E- W+W- PROCESS WITH LARGE EXTRA DIMENSIONS
Abstract We study large extra dimension effects on the polarizations of the W pair and electron beam at the e + e − → W + W − process. It is shown that the measurements of the cross section for transversely polarized W pair with the right-handed electron beam remarkably enhance the possibilities to see the low scale quantum gravity effects. Higher Linear Collider bounds on the string scale in this model can be obtained by using the left-handed electron beam.
1136207
Four light neutrinos in the singular seesaw mechanism with Abelian flavor symmetry
The four light neutrino scenario, which explains the atmosphere, solar and LSND neutrino experiments, is studied in the framework of the seesaw mechanism. By taking both the Dirac and Majorana mass matrix of neutrinos to be singular, the four neutrino mass spectrum consisting of two almost degenerate pairs separated by a mass gap $\sim 1$ eV is naturally generated. Moreover the right-handed neutrino Majorana mass can be at $\sim 10^{14}$ GeV scale unlike in the usual singular seesaw mechanism. Abelian flavor symmetry is used to produce the required neutrino mass pattern. A specific example of the flavor charge assignment is provided to show that maximal mixings between the $\nu_\mu-\nu_\tau$ and $\nu_e-\nu_s$ are respectively attributed to the atmosphere and solar neutrino anomalies while small mixing between two pairs to the LSND results. The implication in the other fermion masses is also discussed.
119422313
Spin configuration of top quark pair production with large extra dimensions at photon-photon colliders
Top quark pair production at photon-photon colliders is studied in low scale quantum gravity scenario. From the dependence of the cross sections on the spin configuration of the top quark and anti-quark, we introduce a new observable, top spin asymmetry. It is shown that there exists a special top spin basis where with the polarized parent electron beams the top spin asymmetry vanishes in the standard model but retains substantial values with the large extra dimension effects. We also present lower bounds of the quantum gravity scale $M_S$ from total cross sections with various combinations of the laser, electron beam, and top quark pair polarizations. The measurements of the top spin state $(t_\uparrow\bar{t}_\downarrow)$ with unpolarized initial beams are shown to be most effective, enhancing by about 5% the $M_S$ bounds with respect to totally unpolarized case.
11586065
Scenario of light sterile neutrinos with a heavy tau neutrino in a supersymmetric model
Three light sterile neutrinos (nu (s)(e), nu (s)(mu) and nu (s)(tau)) are introduced to accommodate all the available neutrino data: the atmospheric neutrino anomaly is explained by nu (mu)-nu (s)(mu) oscillation with maximal mixing; the solar one is due to nu (e)-nu (s)(e) oscillation of small angle Mikheyev-Smirnov-Wolfenstein type; the Liquid Scintillation Neutrino Detector data is from v(e)-v(mu) oscillations, so that the neutrinos can be the hot component of the dark matter. The big bang nucleosynthesis constraint is satisfied by taking the tau neutrino to be 10 MeV heavy. The nu (tau) decay is discussed in a model of gauge mediated supersymmetry breaking. The decay mode v(tau) --> (G) over tilde gamma with (G) over tilde being the gravitino is proposed. The nu (tau) has a rather long lifetime similar to 10(3)-10(13) s. Its implication to the gamma-ray burst is discussed. (C) 2001 Elsevier Science B.V. All rights reserved.
11525411
A Model for neutrino warm dark matter and neutrino oscillations
Abstract The muon- and tau-neutrinos with the mass in the keV range, which are allowed in a low reheating temperature cosmology, can compose the warm dark matter of the universe. A model of four light neutrinos including the keV scale ν μ and ν τ is studied, which combines the seesaw mechanism and the Abelian flavor symmetry. The atmospheric neutrino anomaly is due to the ν μ – ν τ oscillation. The solar neutrino problem is answered by the oscillation into the light sterile neutrino, where the SMA, LMA, and LOW–QVO solutions can be accommodated in our scenario.
118574920
The ABCDEFG of instantons and W-algebras
A bstractFor arbitrary gauge groups, we check at the one-instanton level that the Nekrasov partition function of pure $ \mathcal{N} = {2} $ super Yang-Mills is equal to the norm of a certain coherent state of the corresponding W-algebra. For non-simply-laced gauge groups, we confirm in particular that the coherent state is in the twisted sector of a simply-laced W-algebra.
119109178
The Seiberg-Witten Kähler potential as a two-sphere partition function
A bstractRecently it has been shown that the two-sphere partition function of a gauged linear sigma model of a Calabi-Yau manifold yields the exact quantum Kähler potential of the Kähler moduli space of that manifold. Since four-dimensional $\mathcal{N}=2$ gauge theories can be engineered by non-compact Calabi-Yau threefolds, this implies that it is possible to obtain exact gauge theory Kähler potentials from two-sphere partition functions. In this paper, we demonstrate that the Seiberg-Witten Kähler potential can indeed be obtained as a two-sphere partition function. To be precise, we extract the quantum Kähler metric of 4D $\mathcal{N}=2$ SU(2) Super-Yang-Mills theory by taking the field theory limit of the Kähler parameters of the $\mathcal{O}$(−2, −2) bundle over ${{\mathbb{P}}^1}\times {{\mathbb{P}}^1}$. We expect this method of computing the Kähler potential to generalize to other four-dimensional $\mathcal{N}=2$ gauge theories that can be geometrically engineered by toric Calabi-Yau threefolds.
14366436
Superconformal indices for orbifold Chern-Simons theories
We calculate the superconformal indices of recently discovered three-dimensional N = 4,5 Chern-Simons-matter theories and compare them with the corresponding indices of supergravity on AdS4 times orbifolds of S^7 in the large N and large k limit. We find perfect agreement for orbifolds without fixed locus, and argue that the agreement can continue to hold for orbifolds with fixed locus provided that the mass shifts of the twisted sector states are properly taken into account. We also discuss the index for the so-called "dual ABJM" proposal.
14687090
Current Correlators for General Gauge Mediation
In the gauge mediation mechanism, the effects of the hidden sector are characterized by a set of correlation functions of the global symmetry current of the hidden sector. We present methods to compute these correlators in cases with strongly coupled hidden sectors. Several examples are presented to demonstrate the technique explicitly.
1563485
Quiver tails and N=1$$ \mathcal{N}=1 $$ SCFTs from M5-branes
A bstractWe study a class of four-dimensional N=1$$ \mathcal{N}=1 $$ superconformal field theories obtained by wrapping M5-branes on a Riemann surface with punctures. We identify fourdimensional UV descriptions of the SCFTs corresponding to curves with a class of punctures. The quiver tails appearing in these UV descriptions differ significantly from their N=2$$ \mathcal{N}=2 $$ counterpart. We find a new type of object that we call the ‘Fan’. We show how to construct new N=1$$ \mathcal{N}=1 $$ superconformal theories using the Fan. Various dual descriptions for these SCFTs can be identified with different colored pair-of-pants decompositions. For example, we find an N=1$$ \mathcal{N}=1 $$ analog of Argyres-Seiberg duality for the SU(N ) SQCD with 2N flavors. We also compute anomaly coefficients and superconformal indices for these theories and show that they are invariant under dualities.