Hemidactylus mabouia

Number of Pages: 11Integrative BiologyGeological Science

The specificity of searches for W′W^{\prime}, Z′Z^{\prime} and γ′\gamma^{\prime} coming from extra dimensions

We discuss the specificity of searches for hypothetical $W^{\prime}$, $Z^{\prime}$ and $\gamma^{\prime}$ bosons at hadron colliders in single top quark and $\mu^{+}\nu_{\mu}$ production and Drell-Yan processes assuming these particles to be the Kaluza-Klein excitations of the gauge bosons of the Standard Model. In this case any process mediated by $W$ is also mediated by the whole KK tower of its excitations, whereas to the processes mediated by $Z$ and $\gamma$ there is not only a contribution from their KK towers, but also from that of the graviton. The contributions of the towers above $W^{\prime}$, $Z^{\prime}$ and $\gamma^{\prime}$ and above the first excitation of the graviton are included with the help of effective four-fermion Lagrangians. We compute the cross-sections of these processes taking into account the contributions of the Standard Model gauge bosons, of their first KK modes and of the corresponding KK towers and discuss the impact of the interference between them. For pp-collisions at the LHC with the center of mass energy 14 TeV we found specific changes of the distribution tails due to the interference effects. Such a modification of distribution tails is characteristic for the processes mediated by particles coming from extra dimensions and should always be taken into account when looking for them.Comment: 14 pages, 12 figures, LaTeX. References added, figures added, text enlarge

The decay b -> s g at NLL in the Standard Model

I present the Standard Model calculation of the decay rate for b -> s g (g denotes a gluon) at next-to-leading logarithms (NLL). In order to get a meaningful physical result, the decay b -> s g g and certain contributions of b -> s \bar{f} f (where f are the light quark flavours u, d and s) have to be included as well. Numerically we get BR^(NLL) = (5.0 +/- 1.0) * 10^{-3} which is more than a factor 2 larger than the leading logarithmic result BR^(LL) = (2.2 +/- 0.8) * 10^{-3}. Further, I consider the impact of this contribution on the charmless hadronic branching ratio BRc, which could be used to extract the CKM-ratio |V_(ub)/V_(cb)| with more accuracy. Finally, I have a short look at BRc in scenarios where the Wilson coefficient C_8 is enhanced by new physics.Comment: 7 pages including 5 postscript figures; uses epsfi

Is there the radion in the RS2 model ?

We analyse the physical boundary conditions at infinity for metric fluctuations and gauge functions in the RS2 model with matter on the brane. We argue that due to these boundary conditions the radion field cannot be gauged out in this case. Thus, it represents a physical degree of freedom of the model.Comment: 9 page

Third Neighbor Correlators of Spin-1/2 Heisenberg Antiferromagnet

We exactly evaluate the third neighbor correlator and all the possible non-zero correlators <S^{alpha}_j S^{beta}_{j+1} S^{gamma}_{j+2} S^{delta}_{j+3}> of the spin-1/2 Heisenberg $XXX$ antiferromagnet in the ground state without magnetic field. All the correlators are expressed in terms of certain combinations of logarithm ln2, the Riemann zeta function zeta(3), zeta(5) with rational coefficients. The results accurately coincide with the numerical ones obtained by the density-matrix renormalization group method and the numerical diagonalization.Comment: 4 page

Self-consistent nonperturbative anomalous dimensions

A self-consistent treatment of two and three point functions in models with trilinear interactions forces them to have opposite anomalous dimensions. We indicate how the anomalous dimension can be extracted nonperturbatively by solving and suitably truncating the topologies of the full set of Dyson-Schwinger equations. The first step requires a sensible ansatz for the full vertex part which conforms to first order perturbation theory at least. We model this vertex to obtain typical transcendental equations between anomalous dimension and coupling constant $g$ which coincide with know results to order $g^4$.Comment: 15 pages LaTeX, no figures. Requires iopart.cl

Effective Lagrangians for physical degrees of freedom in the Randall-Sundrum model

We derive the second variation Lagrangian of the Randall-Sundrum model with two branes, study its gauge invariance and diagonalize it in the unitary gauge. We also show that the effective four-dimensional theory looks different on different branes and calculate the observable mass spectra and the couplings of the physical degrees of freedom of 5-dimensional gravity to matter.Comment: 22 pages, LaTeX, typos correcte

Ultimate parameters of the photon collider at the ILC

At linear colliders, the e+e- luminosity is limited by beam-collision effects, which determine the required emittances of beams in damping rings (DRs). While in gamma-gamma collisions at the photon collider, these effects are absent, and so smaller emittances are desirable. In present damping rings designs, nominal DR parameters correspond to those required for e+e- collisions. In this note, I would like to stress once again that as soon as we plan the photon-collider mode of ILC operation, the damping-ring emittances are dictated by the photon-collider requirements--namely, they should be as small as possible. This can be achieved by adding more wigglers to the DRs; the incremental cost is easily justified by a considerable potential improvement of the gamma-gamma luminosity. No expert analysis exists as of yet, but it seems realistic to obtain a factor five increase of the gamma-gamma luminosity compared to the ``nominal'' DR design.Comment: Talk at LCWS06, Bangalore, India, March 2006, to be published in Indian Journal of Physics, 5 pp, Latex, 1 .eps figur

Search for the intermediate Mass Higgs Signal at TeV eγe\gamma colliders

The intermediate mass Higgs (IMH) can be abundantly produced through the process $e^-\gamma \rightarrow W^-H\nu$ at TeV $e^-\gamma$ colliders, which are realized by the laser back-scattering method. We search for the signature of $W^-H \rightarrow (jj)(b\bar b)$ plus missing transverse momentum, with and without considering the $b$-tagging. We also analyse all the potential backgrounds from $e^-\gamma \rightarrow W^-Z\nu,\,W^-W^+e^-,\,ZZe^-,\, \bar t b\nu$ and $t\bar t e^-$. With our selective acceptance cuts these backgrounds are reduced to a manageable level. We find that for the entire intermediate mass range 60 -- 150~GeV the Higgs discovery should be viable. We also present detail formulas for the helicity amplitudes of these processes.Comment: Latex(Revtex), 30 pages, 8 figures in postscript format (uuencoded), NUHEP-TH-93-