Fourth Family Neutrinos and the Higgs Boson

We evaluate the LHC discovery potential for the fourth family Standard Model neutrinos in the process $pp\to Z/h\to\nu_{4}{\bar{\nu}_{4}}\to W\mu W\mu$. We show that, depending on their masses, the simultaneous discovery of both the Higgs boson and the heavy neutrinos is probable at early stages of LHC operation. Results are presented for both Majorana and Dirac type fourth family neutrinos.Comment: 12 pages, uses axodraw.sty, v2: includes typo fixes, improved analysis, v4: minor modifications in response to the JHEP refere

The single production of the lightest E6 isosinglet quark at the LHC

We study the jet associated production of the new quarks predicted by the $E_{6}$ GUT model at the LHC. Generator level considerations are made for different mass values of the lightest of the new quarks to investigate its discovery potential and the prospects for obtaining its mixing angle to the Standard Model quarks. We find that after 100 fb$^{-1}$ of data taking, it is possible to discover the new quark with a significance more than 5$\sigma$ up to a mass of 1500 GeV. If no discovery is made, it is possible to constrain the mass vs quark mixing angle plane.Comment: uses axodraw.st

Parallel Computing Studies for the Alignment of the ATLAS Silicon Tracker

The silicon system of the ATLAS Inner Detector consists of about 6000 modules in its Semiconductor Tracker and Pixel Detector. Therefore, the offline global fit alignment algorithm has to deal with solving a problem of up to 36000 degrees of freedom.32-bit single-CPU platforms were foreseen to be unable to handle such large-size operations needed by the algorithm. The proposed solution is to utilize a Beowulfcluster with a 64-bit architecture. We have performed the initial studies on performance of such a system using SCARF RAL cluster, compared with earlier predictions, obtained the first promising results on parallel computing for the ATLAS tracker alignment. After a brief introduction with the motivation, we will describe the hardware and software used and present the results of the studies, using also examples from the ATLAS simulated data

Four Statements about the Fourth Generation

This summary of the Workshop "Beyond the 3-generation SM in the LHC era" presents a brief discussion of the following four statements about the fourth generation: 1) It is not excluded by EW precision data; 2) It addresses some of the currently open questions; 3) It can accommodate emerging possible hints of new physics; 4) LHC has the potential to discover or fully exclude it.Comment: Summary of the "Beyond the 3-generation SM in the LHC era" Workshop, CERN, September 4-5, 2008; 7 pages. V2: updated bibliography and minor typos fixed. To appear in PMC Physics

Study of a twisted ATLAS SCT Barrel deformation as revealed by a photogrammetric survey

A photogrammetry survey on the SCT barrels was performed as an engineering check on the structure of the ATLAS Semiconductor Tracker (SCT) shortly after construction. Analysis of the data obtained revealed small scale elliptical deformation as well as a twist of the structure. The results of the survey are presented as well as interpolation of the measured targets to the module positions and a comparison with track based alignment measurements

Emission of polarized photons from unpolarized electrons moving in crystals

Radiation emitted by unpolarized high-energy electrons penetrating crystals may be linearly polarized. This occurs when the particle velocity makes an angle, with respect to some major crystal axis, being sufficiently larger than the axial-channelling angle. For such orientation, a complete description of spectral and polarization characteristics of the radiation is derived. At planar channelling, a non-perturbative contribution to the probability of the process appears caused by the plane field, and we must solve exactly a one~-~dimensional mechanical problem. For that, the approximate form of the actual plane potential is suggested which provides a precise fit for any crystal plane and an analytical solution to the motion problem. In a practical case, we must consider electron-photon showers developing in sufficiently thick crystals. For the first time, this development is described taking into account the polarization of photons. We discuss qualitative features of the phenomenon, present results of numerical calculations for thin and thick crystals, and evaluate the possibility of the use of differently oriented crystals in a polarized hard photon source.Comment: 16 pages, 7 PostScript figure