Planar Antennas

This article reviews the state of the art in broadband antennas for emerging UWB applications and addresses the important issues of the broadband antenna design for UWB applications. First, a variety of planar monopoles with finite ground planes are reviewed. Next, the roll antennas with enhanced radiation performance are outlined. After that, the planar antennas printed on PCBs are described. A directional antipodal Vivaldi antenna is also presented for UWB applications. Last, a UWB antenna for wearable applications is exemplifie

A model realizing the Harrison-Perkins-Scott lepton mixing matrix

We present a supersymmetric model in which the lepton mixing matrix $U$ obeys, at the seesaw scale, the Harrison--Perkins--Scott \textit{Ansatz}--vanishing $U_{e3}$, maximal atmospheric neutrino mixing, and $\sin^2{\theta_\odot} = 1/3$ ($\theta_\odot$ is the solar mixing angle). The model features a permutation symmetry $S_3$ among the three lepton multiplets of each type--left-handed doublets, right-handed charged leptons, and right-handed neutrinos--and among three Higgs doublets and three zero-hypercharge scalar singlets; a fourth right-handed neutrino, a fourth Higgs doublet, and a fourth scalar singlet are invariant under $S_3$. In addition, the model has seven \mathbbm{Z}_2 symmetries, out of which six do not commute with $S_3$. Supersymmetry is needed in order to eliminate some quartic terms from the scalar potential, quartic terms which would make impossible to obtain the required vacuum expectation values of the three Higgs doublets and three scalar singlets. The Yukawa couplings to the charged leptons are flavour diagonal, so that flavour-changing neutral Yukawa interactions only arise at loop level.Comment: 16 pages, plain LaTeX, no figures; some clarifying remarks in the conclusions and references added, version accepted for publication in JHE

Remarks on 't Hooft's Brick Wall Model

A semi-classical reasoning leads to the non-commutativity of the space and time coordinates near the horizon of Schwarzschild black hole. This non-commutativity in turn provides a mechanism to interpret the brick wall thickness hypothesis in 't Hooft's brick wall model as well as the boundary condition imposed for the field considered. For concreteness, we consider a noncommutative scalar field model near the horizon and derive the effective metric via the equation of motion of noncommutative scalar field. This metric displays a new horizon in addition to the original one associated with the Schwarzschild black hole. The infinite red-shifting of the scalar field on the new horizon determines the range of the noncommutativ space and explains the relevant boundary condition for the field. This range enables us to calculate the entropy of black hole as proportional to the area of its original horizon along the same line as in 't Hooft's model, and the thickness of the brick wall is found to be proportional to the thermal average of the noncommutative space-time range. The Hawking temperature has been derived in this formalism. The study here represents an attempt to reveal some physics beyond the brick wall model.Comment: RevTeX, 5 pages, no figure

Supersymmetry discovery potential of the LHC at s=\sqrt{s}=10 and 14 TeV without and with missing ETE_T

We examine the supersymmetry (SUSY) reach of the CERN LHC operating at $\sqrt{s}=10$ and 14 TeV within the framework of the minimal supergravity model. We improve upon previous reach projections by incorporating updated background calculations including a variety of $2\to n$ Standard Model (SM) processes. We show that SUSY discovery is possible even before the detectors are understood well enough to utilize either $E_T^{\rm miss}$ or electrons in the signal. We evaluate the early SUSY reach of the LHC at $\sqrt{s}=10$ TeV by examining multi-muon plus $\ge4$ jets and also dijet events with {\it no} missing $E_T$ cuts and show that the greatest reach in terms of $m_{1/2}$ occurs in the dijet channel. The reach in multi-muons is slightly smaller in $m_{1/2}$, but extends to higher values of $m_0$. We find that an observable multi-muon signal will first appear in the opposite-sign dimuon channel, but as the integrated luminosity increases the relatively background-free but rate-limited same-sign dimuon, and ultimately the trimuon channel yield the highest reach. We show characteristic distributions in these channels that serve to distinguish the signal from the SM background, and also help to corroborate its SUSY origin. We then evaluate the LHC reach in various no-lepton and multi-lepton plus jets channels {\it including} missing $E_T$ cuts for $\sqrt{s}=10$ and 14 TeV, and plot the reach for integrated luminosities ranging up to 3000 fb$^{-1}$ at the SLHC. For $\sqrt{s}=10$ TeV, the LHC reach extends to $m_{gluino}=1.9, 2.3, 2.8$ and 2.9 TeV for $m_{squark}\sim m_{gluino}$ and integrated luminosities of 10, 100, 1000 and 3000 fb$^{-1}$, respectively. For $\sqrt{s}=14$ TeV, the LHC reach for the same integrated luminosities is to m_{gluino}=2.4,\3.1, 3.7 and 4.0 TeV.Comment: 34 pages, 25 figures. Revised projections for the SUSY reach for ab^-1 integrated luminosities, with minor corrections of references and text. 2 figures added. To appear in JHE

Measuring the Higgs Sector

If we find a light Higgs boson at the LHC, there should be many observable channels which we can exploit to measure the relevant parameters in the Higgs sector. We use the SFitter framework to map these measurements on the parameter space of a general weak-scale effective theory with a light Higgs state of mass 120 GeV. Our analysis benefits from the parameter determination tools and the error treatment used in new--physics searches, to study individual parameters and their error bars as well as parameter correlations.Comment: 45 pages, Journal version with comments from refere

Seesaw mechanism in the sneutrino sector and its consequences

The seesaw-extended MSSM provides a framework in which the observed light neutrino masses and mixing angles can be generated in the context of a natural theory for the TeV-scale. Sneutrino-mixing phenomena provide valuable tools for connecting the physics of neutrinos and supersymmetry. We examine the theoretical structure of the seesaw-extended MSSM, retaining the full complexity of three generations of neutrinos and sneutrinos. In this general framework, new flavor-changing and CP-violating sneutrino processes are allowed, and are parameterized in terms of two $3\times 3$ matrices that respectively preserve and violate lepton number. The elements of these matrices can be bounded by analyzing the rate for rare flavor-changing decays of charged leptons and the one-loop contribution to neutrino masses. In the former case, new contributions arise in the seesaw extended model which are not present in the ordinary MSSM. In the latter case, sneutrino--antisneutrino mixing generates the leading correction at one-loop to neutrino masses, and could provide the origin of the observed texture of the light neutrino mass matrix. Finally, we derive general formulae for sneutrino--antisneutrino oscillations and sneutrino flavor-oscillations. Unfortunately, neither oscillation phenomena is likely to be observable at future colliders.Comment: 69 pages, 5 figures, uses axodraw.sty. Version accepted for publication in JHEP: some comments and one more Appendix with additional discussion added, references update

de Sitter String Vacua from Supersymmetric D-terms

We propose a new mechanism for obtaining de Sitter vacua in type IIB string theory compactified on (orientifolded) Calabi-Yau manifolds similar to those recently studied by Kachru, Kallosh, Linde and Trivedi (KKLT). dS vacuum appears in KKLT model after uplifting an AdS vacuum by adding an anti-D3-brane, which explicitly breaks supersymmetry. We accomplish the same goal by adding fluxes of gauge fields within the D7-branes, which induce a D-term potential in the effective 4D action. In this way we obtain dS space as a spontaneously broken vacuum from a purely supersymmetric 4D action. We argue that our approach can be directly extended to heterotic string vacua, with the dilaton potential obtained from a combination of gaugino condensation and the D-terms generated by anomalous U(1) gauge groups.Comment: 17 pages, 1 figur

Non-Minimal Sneutrino Inflation, Peccei-Quinn Phase Transition and non-Thermal Leptogenesis

We consider a phenomenological extension of the minimal supersymmetric standard model which incorporates non-minimal chaotic inflation, driven by a quartic potential associated with the lightest right-handed sneutrino. Inflation is followed by a Peccei-Quinn phase transition based on renormalizable superpotential terms, which resolves the strong CP and mu problems of the minimal supersymmetric standard model provided that one related parameter of the superpotential is somewhat small. Baryogenesis occurs via non-thermal leptogenesis, which is realized by the inflaton decay. Confronting our scenario with the current observational data on the inflationary observables, the baryon assymetry of the universe, the gravitino limit on the reheating temperature and the upper bound on the light neutrino masses, we constrain the effective Yukawa coupling involved in the decay of the inflaton to relatively small values and the inflaton mass to values lower than 10^12 GeV.Comment: 21 pages including 3 figures; Final versio

Neutrino masses: From fantasy to facts

Theory suggests the existence of neutrino masses, but little more. Facts are coming close to reveal our fantasy: solar and atmospheric neutrino data strongly indicate the need for neutrino conversions, while LSND provides an intriguing hint. The simplest ways to reconcile these data in terms of neutrino oscillations invoke a light sterile neutrino in addition to the three active ones. Out of the four neutrinos, two are maximally-mixed and lie at the LSND scale, while the others are at the solar mass scale. These schemes can be distinguished at neutral-current-sensitive solar & atmospheric neutrino experiments. I discuss the simplest theoretical scenarios, where the lightness of the sterile neutrino, the nearly maximal atmospheric neutrino mixing, and the generation of $\Delta {m^2}_\odot$ & $\Delta {m^2}_{atm}$ all follow naturally from the assumed lepton-number symmetry and its breaking. Although the most likely interpretation of the present data is in terms of neutrino-mass-induced oscillations, one still has room for alternative explanations, such as flavour changing neutrino interactions, with no need for neutrino mass or mixing. Such flavour violating transitions arise in theories with strictly massless neutrinos, and may lead to other sizeable flavour non-conservation effects, such as $\mu \to e + \gamma$, $\mu-e$ conversion in nuclei, unaccompanied by neutrino-less double beta decay.Comment: 33 pages, latex, 16 figures. Invited Talk at Ioannina Conference, Symmetries in Intermediate High Energy Physics and its Applications, Oct. 1998, to be published by Springer Tracts in Modern Physics. Festschrift in Honour of John Vergados' 60th Birthda

Improved median survival for glioblastoma multiforme following introduction of adjuvant temozolomide chemotherapy

Annals of the Academy of Medicine Singapore365338-342AAMS