Search for lepton flavour violation in the eμ continuum with the ATLAS detector in √s = 7 TeV pp collisions at the LHC

This paper presents a search for the t-channel exchange of an R-parity violating scalar top quark (t) in the e^± μ^∓ continuum using 2.1 fb^(−1) of data collected by the ATLAS detector in √s = 7 TeV pp collisions at the Large Hadron Collider. Data are found to be consistent with the expectation from the Standard Model backgrounds. Limits on R-parity-violating couplings at 95 % C.L. are calculated as a function of the scalar top mass (mt). The upper limits on the production cross section for pp → eμX, through the t-channel exchange of a scalar top quark, ranges from 170 fb for m_t=95 GeV to 30 fb for m_t=1000 GeV

A search for tt resonances with the ATLAS detector in 2.05 fb^(−1) of proton-proton collisions at √s =7 TeV

A search for top quark pair resonances in final states containing at least one electron or muon has been performed with the ATLAS experiment at the CERN Large Hadron Collider. The search uses a data sample corresponding to an integrated luminosity of 2.05 fb^(−1), which was recorded in 2011 at a proton-proton centre-of-mass energy of 7 TeV. No evidence for a resonance is found and limits are set on the production cross-section times branching ratio to tt for narrow and wide resonances. For narrow Z′ bosons, the observed 95 % Bayesian credibility level limits range from 9.3 pb to 0.95 pb for masses in the range of m_(Z′)=500 GeV to m_(Z′)=1300 GeV. The corresponding excluded mass region for a leptophobic topcolour Z′ boson (Kaluza-Klein gluon excitation in the Randall-Sundrum model) is m_(Z′)<880 GeV (m_(gKK)< 1130 GeV)

Measurement of dijet production with a veto on additional central jet activity in pp collisions at √s = 7TeV using the ATLAS detector

A measurement of jet activity in the rapidity interval bounded by a dijet system is presented. Events are vetoed if a jet with transverse momentum greater than 20 GeV is found between the two boundary jets. The fraction of dijet events that survive the jet veto is presented for boundary jets that are separated by up to six units of rapidity and with mean transverse momentum 50 < p_T < 500 GeV. The mean multiplicity of jets above the veto scale in the rapidity interval bounded by the dijet system is also presented as an alternative method for quantifying perturbative QCD emission. The data are compared to a next-to-leading order plus parton shower prediction from the powheg-box, an all-order resummation using the hej calculation and the pythia, herwig++ and alpgen event generators. The measurement was performed using pp collisions at √s=7 TeV using data recorded by the ATLAS detector in 2010

Three resilient megastructures by Pier Luigi Nervi

Resilience, as the ability of a structure to withstand threats and continue to function, it is normally related to durability and performance to accepted standards over time. The resilience of a structure can be threatened by poor design, changes in the public's perception of style, the potential for a change-in-use and structural attack; catastrophic events such as fire, explosion or impact are usually considered the main threats for Resilience. In the contemporary built environment Resilience is considered increasingly important; it has, in fact, become one of the major design issues, especially for large, iconic or public and prominent structures: this has not always been the case. Following the Second World War, building designers faced the necessity to conceive projects within severe financial constraints, hence the proliferation of a low quality and limited life-span structures; buildings which were designed to be replaceable, cheap and perhaps anonymous. This was thought to be an effec-tive answer to quickly accommodate the large number of people moving towards the urban environment partly destroyed by the WWII. These very buildings now constitute the backbone of our urban scenery and although some still function adequately, many are perfect examples of structures which exhibit a lack of re-silience. Fortunately, there were a few designers who refused this post-war tendency and attempted to design lasting structures of quality: most of them were engineers. This is not a coincidence, engineers had less to do with the issue of providing residential accommodations and more with the erection of large structures which necessitated a higher quality control on materials and technologies: Pier Luigi Nervi was one of them. This work considers three large structures designed and built fifty years ago,in 1961, by the Italian engineer. The structures are the Bus Station at the George Washington Bridge in New York (USA); The Burgo Paper Mill in Mantua (Italy); and the Palace of Labour in Turin (Italy). All of these buildings are hybrid structures (concrete and steel), an unusual choice for Nervi that perhaps reects the design climate at the time; These buildings reacted quite differently to the events that have occurred over the past half century. One of the key factors to achieve resilience it is considered to be the quality of the buildings, which includes their ability to perform maintenance. The lack of which for whatever reason, this paper aims to demonstrate, will inevitably result in a weak performance in terms of resilience on the long run

Hosing of a long relativistic particle bunch in plasma

Experimental results show that hosing of a long particle bunch in plasma can be induced by wakefields driven by a short, misaligned preceding bunch. Hosing develops in the plane of misalignment, self-modulation in the perpendicular plane, at frequencies close to the plasma electron frequency, and are reproducible. Development of hosing depends on misalignment direction, its growth on misalignment extent and on proton bunch charge. Results have the main characteristics of a theoretical model, are relevant to other plasma-based accelerators and represent the first characterization of hosing

Measurement of the inclusive jet cross-section in pp collisions at √s = 2.76 TeV and comparison to the inclusive jet cross-section at √s = 7 TeV using the ATLAS detector

The inclusive jet cross-section has been measured in proton–proton collisions at √s = 2.76 TeV in a dataset corresponding to an integrated luminosity of 0.20^(-1) collected with the ATLAS detector at the Large Hadron Collider in 2011. Jets are identified using the anti-k_t algorithm with two radius parameters of 0.4 and 0.6. The inclusive jet double-differential cross-section is presented as a function of the jet transverse momentum p_T and jet rapidity y, covering a range of 20≤p_T<430 GeV and |y|<4.4. The ratio of the cross-section to the inclusive jet cross-section measurement at √s = 7 TeV , published by the ATLAS Collaboration, is calculated as a function of both transverse momentum and the dimensionless quantity x_T =2 p_T/√s, in bins of jet rapidity. The systematic uncertainties on the ratios are significantly reduced due to the cancellation of correlated uncertainties in the two measurements. Results are compared to the prediction from next-to-leading order perturbative QCD calculations corrected for non-perturbative effects, and next-to-leading order Monte Carlo simulation. Furthermore, the ATLAS jet cross-section measurements at √s = 2.76 TeV and √s = 7 TeV are analysed within a framework of next-to-leading order perturbative QCD calculations to determine parton distribution functions of the proton, taking into account the correlations between the measurements

Measurement of the tt production cross section in the tau + jets channel using the ATLAS detector

A measurement of the top quark pair production cross section in the final state with a hadronically decaying tau lepton and jets is presented. The analysis is based on proton–proton collision data recorded by the ATLAS experiment at the LHC, with a centre-of-mass energy of 7 TeV. The data sample corresponds to an integrated luminosity of 1.67 fb^(−1). The cross section is measured to be σ_(tt)=194±18 (stat.)±46 (syst.) pb and is in agreement with other measurements and with the Standard Model prediction

Multi-channel search for squarks and gluinos in √s = 7 TeV pp collisions with the ATLAS detector at the LHC

A search for supersymmetric particles in final states with zero, one, and two leptons, with and without jets identified as originating from b-quarks, in 4.7 fb^(−1) of s√=7 TeV pp collisions produced by the Large Hadron Collider and recorded by the ATLAS detector is presented. The search uses a set of variables carrying information on the event kinematics transverse and parallel to the beam line that are sensitive to several topologies expected in supersymmetry. Mutually exclusive final states are defined, allowing a combination of all channels to increase the search sensitivity. No deviation from the Standard Model expectation is observed. Upper limits at 95 % confidence level on visible cross-sections for the production of new particles are extracted. Results are interpreted in the context of the constrained minimal supersymmetric extension to the Standard Model and in supersymmetry-inspired models with diverse, high-multiplicity final states

Search for a light charged Higgs boson in the decay channel H^+→cs in tt events using pp collisions at s√=7 TeV with the ATLAS detector

A search for a charged Higgs boson (H^+) in tt decays is presented, where one of the top quarks decays via t→H^+ b, followed by H^+→ two jets (cs). The other top quark decays to Wb, where the W boson then decays into a lepton (e/μ) and a neutrino. The data were recorded in pp collisions at s√=7 TeV by the ATLAS detector at the LHC in 2011, and correspond to an integrated luminosity of 4.7 fb^(−1). With no observation of a signal, 95 % confidence level (CL) upper limits are set on the decay branching ratio of top quarks to charged Higgs bosons varying between 5 % and 1 % for H^+ masses between 90 GeV and 150 GeV, assuming B(H^+→cs)=100%

The megalithic building of S.Erasmo di Cesi: architecture, astronomy, and landscape

Abstract. One of the most enigmatic megalithic buildings of Italy is the structure which lies on the S. Erasmo hill near Cesi, in Umbria, a huge complex encompassing an area of around 8000 square meters and enclosed by refined cyclopean walls. Although its date is uncertain, suggested dates comprise the Iron Age and archaic period, down to the third century B.C. The building’s function is also uncertain. Usually identified as a fortified structure, in fact there is a megalithic platform at the southern end of the enclosure which could have served as foundation of a temple or palace and, from the top of Monte Torre Maggiore, a complex of temples dating from the fourth century B.C. overlooks the hill. Similar combinations of megalithic buildings resting half-way to temples placed on high peaks are known to exist. In order to clarify the function of this structure and its position in relation to the surrounding landscape, with particular attention to its visibility and to the directions of visibility from the complex, as well as to the possible astronomical alignments, we present a multi-disciplinary approach to the study of the S. Erasmo complex, which includes the mapping of the sky at the various possible epochs of construction, the creation of a digital model of the landscape in forms of digital maps using Geographic Information System technologies, and a 3D model using various 3D software packages