Charged Lepton Flavor Physics and Extra Dimensions

We estimate the charged lepton electric dipole moments and the branching ratios of radiative lepton flavor violating decays in the framework of the two Higgs doublet model with the inclusion two extra dimensions. Here, we consider that the new Higgs doublet is accessible to one of the extra dimensions with a Gaussian profile and the fermions are accessible to the other extra dimension with uniform zero mode profile. We observe that the numerical values of the physical quantities studied enhance with the additional effects due to the extra dimensions and they are sensitive to the new Higgs localization.Comment: 23 pages, 13 page

Spin properties of dense near-surface ensembles of nitrogen-vacancy centres in diamond

We present a study of the spin properties of dense layers of near-surface nitrogen-vacancy (NV) centres in diamond created by nitrogen ion implantation. The optically detected magnetic resonance contrast and linewidth, spin coherence time, and spin relaxation time, are measured as a function of implantation energy, dose, annealing temperature and surface treatment. To track the presence of damage and surface-related spin defects, we perform in situ electron spin resonance spectroscopy through both double electron-electron resonance and cross-relaxation spectroscopy on the NV centres. We find that, for the energy ($4-30$~keV) and dose ($5\times10^{11}-10^{13}$~ions/cm$^2$) ranges considered, the NV spin properties are mainly governed by the dose via residual implantation-induced paramagnetic defects, but that the resulting magnetic sensitivity is essentially independent of both dose and energy. We then show that the magnetic sensitivity is significantly improved by high-temperature annealing at $\geq1100^\circ$C. Moreover, the spin properties are not significantly affected by oxygen annealing, apart from the spin relaxation time, which is dramatically decreased. Finally, the average NV depth is determined by nuclear magnetic resonance measurements, giving $\approx10$-17~nm at 4-6 keV implantation energy. This study sheds light on the optimal conditions to create dense layers of near-surface NV centres for high-sensitivity sensing and imaging applications.Comment: 12 pages, 7 figure

Observing Ultra High Energy Cosmic Particles from Space: SEUSO, the Super Extreme Universe Space Observatory Mission

The experimental search for ultra high energy cosmic messengers, from $E\sim 10^{19}$ eV to beyond $E\sim 10^{20}$ eV, at the very end of the known energy spectrum, constitutes an extraordinary opportunity to explore a largely unknown aspect of our universe. Key scientific goals are the identification of the sources of ultra high energy particles, the measurement of their spectra and the study of galactic and local intergalactic magnetic fields. Ultra high energy particles might, also, carry evidence of unknown physics or of exotic particles relics of the early universe. To meet this challenge a significant increase in the integrated exposure is required. This implies a new class of experiments with larger acceptances and good understanding of the systematic uncertainties. Space based observatories can reach the instantaneous aperture and the integrated exposure necessary to systematically explore the ultra high energy universe. In this paper, after briefly summarising the science case of the mission, we describe the scientific goals and requirements of the SEUSO concept. We then introduce the SEUSO observational approach and describe the main instrument and mission features. We conclude discussing the expected performance of the mission

The radiative lepton flavor violating decays in the split fermion scenario in the two Higgs doublet model

We study the branching ratios of the lepton flavor violating processes \mu -> e \gamma, \tau -> e \gamma and \tau -> \mu\gamma in the split fermion scenario, in the framework of the two Higgs doublet model. We observe that the branching ratios are relatively more sensitive to the compactification scale and the Gaussian widths of the leptons in the extra dimensions, for two extra dimensions and especially for the \tau -> \mu \gamma decay.Comment: 19 pages, 7 Figure

Low-scale warped extra dimension and its predilection for multiple top quarks

Within warped extra dimension models that explain flavor through geometry, flavor changing neutral current constraints generally force the Kaluza-Klein scale to be above many TeV. This creates tension with a natural electroweak scale. On the other hand, a much lower scale compatible with precision electroweak and flavor changing neutral current constraints is allowed if we decouple the Kaluza-Klein states of Standard Model gauge bosons from light fermions $c_{\rm light}\simeq c_b\simeq 0.5$ bulk mass parameters). The main signature for this approach is four top quark production via the Kaluza-Klein excitations' strong coupling to top quarks. We study single lepton, like-sign dilepton, and trilepton observables of four-top events at the Large Hadron Collider. The like-sign dilepton signature typically has the largest discovery potential for a strongly coupled right-handed top case (M_{KK} \sim 2-2.5 \TeV), while single lepton is the better when the left-handed top couples most strongly (M_{KK} \sim 2 \TeV). We also describe challenging lepton-jet collimation issues in the like-sign dilepton and trilepton channels. An alternative single lepton observable is considered which takes advantage of the many bottom quarks in the final state. Although searches of other particles may compete, we find that four top production via Kaluza-Klein gluons is most promising in a large region of this parameter space.Comment: 35 pages, 8 figures. discussions improved, references adde

New Higgs Production Mechanism in Composite Higgs Models

Composite Higgs models are only now starting to be probed at the Large Hadron Collider by Higgs searches. We point out that new resonances, abundant in these models, can mediate new production mechanisms for the composite Higgs. The new channels involve the exchange of a massive color octet and single production of new fermion resonances with subsequent decays into the Higgs and a Standard Model quark. The sizable cross section and very distinctive kinematics allow for a very clean extraction of the signal over the background with high statistical significance. Heavy gluon masses up to 2.8 TeV can be probed with data collected during 2012 and up to 5 TeV after the energy upgrade to $\sqrt{s}=14$ TeV.Comment: 27 pages, 22 figures. V2: typos corrected, matches published versio

Theories for the Fermi Scale

I give a short review of our present understanding of new theories of the electroweak scale, with emphasis on recent progress. Plenary talk at the EPS 2007 Conference at Manchester.Comment: 14 pages, EPS 2007 Conferenc

The Discovery Potential of a Super B Factory

The Proceedings of the 2003 SLAC Workshops on flavor physics with a high luminosity asymmetric e+e- collider. The sensitivity of flavor physics to physics beyond the Standard Model is addressed in detail, in the context of the improvement of experimental measurements and theoretical calculations.Comment: 476 pages. Printed copies may be obtained by request to [email protected] . arXiv admin note: v2 appears to be identical to v

Top Quark Physics at the LHC: A Review of the First Two Years

This review summarizes the highlights in the area of top quark physics obtained with the two general purpose detectors ATLAS and CMS during the first two years of operation of the Large Hadron Collider LHC. It covers the 2010 and 2011 data taking periods, where the LHC provided pp collisions at a center-of-mass energy of sqrt(s)=7 TeV. Measurements are presented of the total and differential top quark pair production cross section in many different channels, the top quark mass and various other properties of the top quark and its interactions, for instance the charge asymmetry. Measurements of single top quark production and various searches for new physics involving top quarks are also discussed. The already very precise experimental data are in good agreement with the standard model.Comment: 107 pages, invited review for Int. J. Mod. Phys. A, v2 is identical to v1 except for the addition of the table of content