Phenomenology of the minimal supersymmetric U(1)B−L×U(1)RU(1)_{B-L}\times U(1)_R extension of the standard model

We discuss the minimal supersymmetric $U(1)_{B-L}\times U(1)_R$ extension of the standard model. Gauge couplings unify as in the MSSM, even if the scale of $U(1)_{B-L}\times U(1)_R$ breaking is as low as order TeV and the model can be embedded into an SO(10) grand unified theory. The phenomenology of the model differs in some important aspects from the MSSM, leading potentially to rich phenomenology at the LHC. It predicts more light Higgs states and the mostly left CP-even Higgs has a mass reaching easily 125 GeV, with no constraints on the SUSY spectrum. Right sneutrinos can be the lightest supersymmetric particle, changing all dark matter constraints on SUSY parameter space. The model has seven neutralinos and squark/gluino decay chains involve more complicated cascades than in the MSSM. We also discuss briefly low-energy and accelerator constraints on the model, where the most important limits come from recent $Z'$ searches at the LHC and upper limits on lepton flavour violation.Comment: 46 pages, 11 figure

Structure of dimension-six derivative interactions in pseudo Nambu-Goldstone N Higgs doublet models

We derive the general structure of dimension-six derivative interactions in the N Higgs doublet models, where Higgs fields arise as pseudo Nambu-Goldstone modes of a strongly interacting sector. We show that there are several relations among the dimension-six operators, and therefore the number of independent operators decreases compared with models on which only SU(2)_L x U(1)_Y invariance is imposed. As an explicit example, we derive scattering amplitudes of longitudinal gauge bosons and Higgs bosons at high energy on models involving two Higgs doublets, and compare them with the amplitudes in the case of one Higgs doublet.Comment: 49 pages, 10 figure

Standard Model Higgs boson searches with the ATLAS detector at the Large Hadron Collider

The investigation of the mechanism responsible for electroweak symmetry breaking is one of the most important tasks of the scientific program of the Large Hadron Collider. The experimental results on the search of the Standard Model Higgs boson with 1 to 2 fb^-1 of proton proton collision data at sqrt s=7 TeV recorded by the ATLAS detector are presented and discussed. No significant excess of events is found with respect to the expectations from Standard Model processes, and the production of a Higgs boson is excluded at 95% Confidence Level for the mass regions 144-232, 256-282 and 296-466 GeV.Comment: Proceedings of the Lepton Photon 2011 Conference, to appear in "Pramana - journal of phsyics". 11 pages, 13 figure

Measurement of the Superparticle Mass Spectrum in the Long-Lived Stau Scenario at the LHC

In supersymmetric scenarios with a long-lived stau, the LHC experiments provide us with a great environment for precise mass measurements of superparticles. We study a case in which the mass differences between the lightest stau and other sleptons are about 10 GeV or larger, so that the decay products of heavier sleptons are hard enough to be detected. We demonstrate that the masses of neutralinos, sleptons, and squarks can be measured with a good accuracy.Comment: 20 pages, 6 figure

Interactions of Heavy Hadrons using Regge Phenomenology and the Quark Gluon String Model

The search for stable heavy exotic hadrons is a promising way to observe new physics processes at collider experiments. The discovery potential for such particles can be enhanced or suppressed by their interactions with detector material. This paper describes a model for the interactions in matter of stable hadrons containing an exotic quark of charges $\pm {1/3}e$ or $\pm {2/3}e$ using Regge phenomenology and the Quark Gluon String Model. The influence of such interactions on searches at the LHC is also discussed

Ageing test of the ATLAS RPCs at X5-GIF

An ageing test of three ATLAS production RPC stations is in course at X5-GIF, the CERN irradiation facility. The chamber efficiencies are monitored using cosmic rays triggered by a scintillator hodoscope. Higher statistics measurements are made when the X5 muon beam is available. We report here the measurements of the efficiency versus operating voltage at different source intensities, up to a maximum counting rate of about 700Hz/cm^2. We describe the performance of the chambers during the test up to an overall ageing of 4 ATLAS equivalent years corresponding to an integrated charge of 0.12C/cm^2, including a safety factor of 5.Comment: 4 pages. Presented at the VII Workshop on Resistive Plate Chambers and Related Detectors; Clermont-Ferrand October 20th-22nd, 200

Proceedings of the Workshop on Monte Carlo's, Physics and Simulations at the LHC PART II

These proceedings collect the presentations given at the first three meetings of the INFN "Workshop on Monte Carlo's, Physics and Simulations at the LHC", held at the Frascati National Laboratories in 2006. The first part of these proceedings contains pedagogical introductions to several basic topics of both theoretical and experimental high pT LHC physics. The second part collects more specialised presentations.Comment: 157 pages, 136 figures; contribution by M. Grazzini has been adde

Stau Kinks at the LHC

The kink signature of charged tracks is predicted in some SUSY models, and it is very characteristic signal at collider experiments. We study the kink signature at LHC using two models, SUSY models with a gravitino LSP and a stau NLSP, and R-parity violating SUSY models with a stau (N)LSP. We find that a large number of kink events can be discovered in a wide range of the SUSY parameters, when the decay length is O(10-10^5)mm. Model discrimination by identifying the daughter particles of the kink tracks is also discussed.Comment: 19 pages, 4 figures; Version published in JHEP; abstract refined, reference added and several minor corrections in tex

The first level muon trigger in the central toroid of the ATLAS experiment

We present the design of the first level muon trigger in the central toroid of the ATLAS experiment at the Large Hadron Collider (LHC). A trigger is foreseen based on fast, finely segmented gaseous detectors, Resistive Plate Chambers (RPC), to unambiguously identify the interaction bunch crossing. We describe the detectors and the logic scheme of the trigger. © 1995