119274952
Lepton flavor violation in a nonuniversal gauge interaction model
The flavor-changing neutral currents (FCNC) are derived at tree level if the electroweak gauge group depends on the fermion family, which are absent in the standard model. We study the lepton flavor violation through the FCNC interactions in a nonuniversal gauge interaction model where the third generation fermions are subjected to the separate SU(2){sub L} gauge group.
17539215
Implications of the recent CERN LEP data on nonuniversal interactions with the precision electroweak tests
We explore the nonuniversal interaction effects in terms of the precision variables epsilons with the recent CERN LEP data reported by the Electroweak Working Group. The epsilon variables with the nonuniversal interactions are calculated and constrained by the experimental ellipses in the {epsilon}{sub 1}{endash}{epsilon}{sub b}, {epsilon}{sub 2}{endash}{epsilon}{sub b}, and {epsilon}{sub 3}{endash}{epsilon}{sub b} planes. We find that the new data enable us to make a stringent test on the correction to Z{r_arrow}b{bar b} vertex. The {epsilon}{sub b} variable is sensitive to the Zb{bar b} couplings and thus plays a major role to give constraints on the nonuniversal interaction effects. Upon imposing the new data on {epsilon}{sub b}, we have the allowed range of the model parameter {kappa}{sub L}=0.0063{plus_minus}0.0030 at 1-{sigma} level with m{sub t}=175 GeV. Along with the minimal contact term, we predict the new physics scale {Lambda}{approximately} 1.6 TeV. By combining the experimental results from all planes we obtain the allowed range of {kappa}{sub L}: 0.003{lt}{kappa}{sub L}{lt}0.010 at 95{percent} C.L. {copyright} {ital 1997} {ital The American Physical Society}
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.
14611917
Polarization effects on W boson pair productions with the extra neutral gauge boson at the e^+ e^- Linear Collider
We perform the comprehensive analysis of the polarization effects on the e^+e^- -> W^+W^- process in the presence of the extra neutral gauge boson at the LC energies. Consideration of the polarizations of the produced W bosons and the beam polarizations provides substantial enhancements of the sensitivity to the Z-Z' mixing angles in various models and the asymmetry variables also give the strict constraints on the mixing angles. We find that the \chi-model and the left-right model get the strict constraint from \sigma_{LL}^{unpol} while the \psi-model and the \eta-model from the beam polarization asymmetry.
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.
16963420
Evolution equation for the heavy quark distribution function in the parton model approach
We explore the perturbative QCD corrections to the inclusive semileptonic decays of $B$ mesons. In inclusive $B$ decay processes the parton picture works well and the scaling feature manifests because the mass of $b$ quark is larger than the QCD scale. Due to this property, the decay rate may be expressed by a single structure function describing the light-cone distribution of $b$ quark apart from the kinematic factor. We derive a $q^2$ evolution equation for the distribution function, which violates the scaling property through the Altarelli-Parisi type approach. The evolution equation is numerically solved and its phenomenological implications are also discussed.
119916631
Charge violation by instantons in Chern-Simons theories☆
Abstract We study the effect of magnetic monopole instantons in abelian Chern-Simons gauge theories. An effective interaction induced by instantons is shown to break the global part if U(1) gauge symmetry into a finite cyclic subgroup. We present an understanding of the complex action and solution in euclidean space-time, boundary terms, and linear divergence of the instanton action.
10623913
= 4 Superconformal Chern-Simons theories with hyper and twisted hyper multiplets
We extend the = 4 superconformal Chern-Simons theories of Gaiotto and Witten to those with additional twisted hyper-multiplets. The new theories are generically linear quiver gauge theories with the two types of hyper-multiplets alternating between gauge groups. Our construction includes the Bagger-Lambert model of SO(4) gauge group. A family of abelian theories are identified with those proposed earlier in the context of the M-crystal model for M2-branes probing (2/n)2 orbifolds. Possible extension with non-abelian BF couplings and string/M-theory realization are briefly discussed.
13502490
Dyonic instanton as supertube between D4-branes
We study dyonic instantons in (4+1) dimensional Yang-Mills theory. Especially we consider the most general two instanton solution given by the Jackiw-Nohl-Rebbi ansatz and find its dyonic version. By exploring the zeros of the Higgs field, we rederive the porism structure of triangles in this solution and also find the magnetic monopole string loop. This leads to the identification of dyonic instanton with the supertube inserted between D4-branes.
16407526
The Moduli Space of BPS Monopoles
We review a progress in our understanding of the moduli space for an arbitrary number of BPS monopoles in a gauge theory with a group $G$ of rank $r$ that is maximally broken to $U(1)^r$. The derivation of the moduli space metric has been obtained from studying the low energy dynamics of well-separated dyons.
11027460
Low-energy dynamics for 1/4 BPS dyons
Classical 1/4 BPS configurations consist of 1/2 BPS dyons which are positioned by competing static forces from electromagnetic and Higgs sectors. These forces do not follow the simple inverse square law, but can be encoded in some low energy effective potential between fundamental monopoles of distinct types. In this paper, we find this potential, by comparing the exact 1/4 BPS bound from a Yang-Mills field theory with its counterpart derived from low energy effective dynamics of monopoles. Our method is generalized to arbitrary gauge groups and to arbitrary BPS monopole/dyon configurations. The resulting effective action for 1/4 BPS states is written explicitly, and shown to be determined entirely by the geometry of multi-monopole moduli spaces. We also explore its natural supersymmetric extension.