The Phenomenology of Universal Extra Dimensions at Hadron Colliders

Theories with extra dimensions of inverse TeV size (or larger) predict a multitude of signals which can be searched for at present and future colliders. In this paper, we review the different phenomenological signatures of a particular class of models, universal extra dimensions, where all matter fields propagate in the bulk. Such models have interesting features, in particular Kaluza-Klein (KK) number conservation, which makes their phenomenology similar to that of supersymmetric theories. Thus, KK excitations of matter are produced in pairs, and decay to a lightest KK particle (LKP), which is stable and weakly interacting, and therefore will appear as missing energy in the detector (similar to a neutralino LSP). Adding gravitational interactions which can break KK number conservation greatly expands the class of possible signatures. Thus, if gravity is the primary cause for the decay of KK excitations of matter, the experimental signals at hadron colliders will be jets + missing energy, which is typical of supergravity models. If the KK quarks and gluons decay first to the LKP, which then decays gravitationally, the experimental signal will be photons and/or leptons (with some jets), which resembles the phenomenology of gauge mediated supersymmetry breaking models.Comment: review article, 39 pages, 10 figures, uses IJMPA style file

Hybrid Pixel Detector Development for the Linear Collider Vertex Tracker

In order to fully exploit the physics potential of the future high energy e+e- linear collider, a Vertex Tracker able to provide particle track extrapolation with very high resolution is needed. Hybrid Si pixel sensors are an attractive technology due to their fast read-out capabilities and radiation hardness. A novel pixel detector layout with interleaved cells has been developed to improve the single point resolution. Results of the characterisation of the first processed prototypes by electrostatic measurements and charge collection studies are discussed.Comment: 5 pages, 1 figure, to appear in the Proceedings of the 9th Int. Workshop on Vertex Detectors, Lake Michigan MI (USA), September~200

Determination of the muon Yukawa coupling at high energy e+e- linear colliders

The perspectives for the observation of the rare decay H -> mumu decay and the determination of the muon Yukawa coupling at a TeV-class and at a multi-TeV e+e- linear colliders are discussed. The signal for the decay can be obtained at 0.8 TeV and a first estimate of the coupling derived. A linear collider operating at 3 TeV, with high luminosity, is able to improve the accuracy on this couplings to 4% to 11% for 120 GeV < M_H < 150 GeV.Comment: 3 pages, 2 figures, to appear on the proceedings of the Snowmass 2001 Summer Study, Snowmass CO, June-July 200

B2 and G2 Toda systems on compact surfaces: a variational approach

We consider the B2 and G2 Toda systems on compact surfaces. We attack the problem using variational techniques. We get existence and multiplicity of solutions under a topological assumption on the surface and some generic conditions on the parameters. We also extend some of the results to the case of general systems.Comment: 28 pages, accepted on Journal of Mathematical Physic

Observations of a Radio-quiet Solar Preflare

The preflare phase of the flare SOL2011-08-09T03:52 is unique in its long duration, its coverage by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and the Nobeyama Radioheliograph, and the presence of three well-developed soft X-ray (SXR) peaks. No hard X-rays (HXR) are observed in the preflare phase. Here we report that also no associated radio emission at 17 GHz was found despite the higher sensitivity of the radio instrument. The ratio between the SXR peaks and the upper limit of the radio peaks is larger by more than one order of magnitude compared to regular flares. The result suggests that the ratio between acceleration and heating in the preflare phase was different than in regular flares. Acceleration to relativistic energies, if any, occurred with lower efficiency.Comment: 9 pages, 3 figures, accepted by Solar Physic

Light neutralino dark matter in MSSM

Three dark matter direct detection experiments, DAMA, COGENT and CRESST, have reported a possible signal of WIMP interaction corresponding to very light particles, close to the edge of the XENON 100 and CDMS sensitivity. Imposing the latest constraints from colliders, flavour physics, electroweak precision tests and direct and indirect dark matter searches, we show that viable MSSM scenarios with a light neutralino, in agreement with all the present data, are feasible. An analysis of the characteristics of the resulting scenarios will be presented.Comment: 6 pages, 2 figures, contribution to the ICHEP 2012 Conference proceedings, 4-11 July 2012, Melbourne, Australi

Study of e+e- -> H+H- at a 800 GeV Linear Collider

The production and decay of heavy charged Higgs bosons at a 800 GeV e+e- linear collider have been studied. The analysis of the H+H- -> tb tb, expected to be dominant in the MSSM, and H+H- -> W+h0 W-h0 decay modes leading to the same final state consisting of two W bosons and four b quarks, provides with a determination of the boson mass to 1 GeV and of the production cross section with 10% accuracy for 500 fb-1 of data.Comment: 4 pages, 1 figure, to appear in the Proceedings of the 5th Linear Collider Workshop Fermilab, October 200

Implementation of polarization diversity pulse-pair technique using airborne W-band radar

This work describes the implementation of polarization diversity on the National Research Council Canada W-band Doppler radar and presents the first-ever airborne Doppler measurements derived via polarization diversity pulse-pair processing. The polarization diversity pulse-pair measurements are interleaved with standard pulse-pair measurements with staggered pulse repetition frequency, this allows a better understanding of the strengths and drawbacks of polarization diversity, a methodology that has been recently proposed for wind-focused Doppler radar space missions. Polarization diversity has the clear advantage of making possible Doppler observations of very fast decorrelating media (as expected when deploying Doppler radars on fast-moving satellites) and of widening the Nyquist interval, thus enabling the observation of very high Doppler velocities (up to more than 100 m s−1 in the present work). Crosstalk between the two polarizations, mainly caused by depolarization at backscattering, deteriorated the quality of the observations by introducing ghost echoes in the power signals and by increasing the noise level in the Doppler measurements. In the different cases analyzed during the field campaigns, the regions affected by crosstalk were generally associated with highly depolarized surface returns and depolarization of backscatter from hydrometeors located at short ranges from the aircraft. The variance of the Doppler velocity estimates can be well predicted from theory and were also estimated directly from the observed correlation between the H-polarized and V-polarized successive pulses. The study represents a key milestone towards the implementation of polarization diversity in Doppler space-borne radars

Direct Searches of New Physics at CLIC

The multi-TeV e+e- collider CLIC may allow for the direct study of new neutral gauge bosons or Kaluza-Klein states in the TeV range. We discuss some of the experimental aspects for the study of such resonances. Further we discuss briefly the effects of soft branes in scenarios with Large Extra Dimensions, and the production of Black Holes at CLIC.Comment: 9 pages, 4 figures, to appear in the proceedings of the LCWS02 Worksho

Graviton Production at CLIC

Direct production of Kaluza-Klein states in the TeV range is studied for the experimental environment at the multi-TeV $e^+e^-$ collider CLIC. The sensitivity of such data to model parameters is discussed for the Randall-Sundrum(RS) and TeV scale extra dimensional models.Comment: 5 pages, 5 figures, to appear on the Proceedings of the Snowmass 2001 Summer Study, Snowmass CO (USA), July 200