Siting the Superconducting Super Collider in Illinois : an overview and predictive model of cultural and paleobiological resources in the SSC study area, northern Illinois /

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Transmedia storytelling e a construção de um universo participativo: estudo de caso do projeto “collider”

Dissertação apresentada à Escola Superior de Comunicação Social como parte dos requisitos para obtenção de grau de mestre em Audiovisual e Multimédia.

Os efeitos nucleares em processos de produ¸c˜ao de quarkonium no Relativistic Heavy Ion Collider (RHIC) e no Large Hadron Collider (LHC)

Neste trabalho de disserta¸c˜ao, investigamos os efeitos nucleares em processos de produ¸c˜ao de quarkonium no Relativistic Heavy Ion Collider (RHIC) e no Large Hadron Collider (LHC). Para tanto, consideramos o Modelo de Evapora¸c˜ao de Cor (CEM), baseado em processos partˆonicos calculados mediante a QCD perturbativa e em intera¸c˜oes n˜ao perturbativas via troca de gl´uons suaves para a forma¸c˜ao do quarkonium. Supress˜ao de quarkonium ´e um dos sinais de forma¸c˜ao do assim chamado Plasma de Quarks e Gl´uons (QGP) em colis˜oes ultrarelativ´ısticas de ´ıons pesados. No entanto, a supress˜ao n˜ao ´e somente causada em colis˜oes n´ucleo-n´ucleo (AA) devido `a forma¸c˜ao do QGP. De fato, a supress˜ao de quarkonium tamb´em foi observada em colis˜oes pr´oton-n´ucleo (pA). A fim de separar os efeitos da mat´eria quente (devidos ao QGP) e fria (efeitos n˜ao devidos ao QGP), pode-se olhar primeiro para colis˜oes pA, onde somente efeitos de mat´eria fria desempenham um papel fundamental, e depois aplicar esses efeitos em colis˜oes AA, uma vez que parte da supress˜ao ´e devido a efeitos de mat´eria fria. No regime de altas energias, a produ¸c˜ao do quarkonium ´e fortemente dependente da distribui¸c˜ao de gl´uons nuclear, o que viabiliza uma oportunidade ´unica de estudar o comportamento de pequeno x dos gl´uons dentro do n´ucleo e, consequentemente, restringir os efeitos nucleares. Estudamos os processos nucleares utilizando distintas parametriza¸c˜oes para as distribui¸c˜oes partˆonicas nucleares. Calculamos a raz˜ao nuclear para processos pA e AA em fun¸c˜ao da vari´avel rapidez para a produ¸c˜ao de quarkonium, o que permite estimar os efeitos nucleares. Al´em disso, apresentamos uma compara¸c˜ao com os dados do RHIC para a produ¸c˜ao do m´eson J/Ψ em colis˜oes pA, demonstrando que a an´alise deste observ´avel ´e uma quest˜ao em aberto na literatura. Adicionalmente, estimamos a produ¸c˜ao de quarks pesados e quarkonium na etapa inicial e durante a fase termal de uma colis˜ao ultrarelativ´ıstica de ´ıons pesados. O objetivo deste estudo ´e estimar as distintas contribui¸c˜oes para a produ¸c˜ao e de alguns efeitos do meio nuclear.

Quality of ALICE SSD modules revealed by electrical tests

ALICE (A Large Ion Collider Experiment) is an experiment at CERN (European Organization for Nuclear Research), where a heavy-ion detector is dedicated to exploit the unique physics potential of nucleus-nucleus interactions at LHC (Large Hadron Collider) energies. In a part of that project, 716 so-called type V4 modules were assembles in Detector Laboratory of Helsinki Institute of Physics during the years 2004 - 2006. Altogether over a million detector strips has made this project the most massive particle detector project in the science history of Finland. One ALICE SSD module consists of a double-sided silicon sensor, two hybrids containing 12 HAL25 front end readout chips and some passive components, such has resistors and capacitors. The components are connected together by TAB (Tape Automated Bonding) microcables. The components of the modules were tested in every assembly phase with comparable electrical tests to ensure the reliable functioning of the detectors and to plot the possible problems. The components were accepted or rejected by the limits confirmed by ALICE collaboration. This study is concentrating on the test results of framed chips, hybrids and modules. The total yield of the framed chips is 90.8%, hybrids 96.1% and modules 86.2%. The individual test results have been investigated in the light of the known error sources that appeared during the project. After solving the problems appearing during the learning-curve of the project, the material problems, such as defected chip cables and sensors, seemed to induce the most of the assembly rejections. The problems were typically seen in tests as too many individual channel failures. Instead, the bonding failures rarely caused the rejections of any component. One sensor type among three different sensor manufacturers has proven to have lower quality than the others. The sensors of this manufacturer are very noisy and their depletion voltage are usually outside of the specification given to the manufacturers. Reaching 95% assembling yield during the module production demonstrates that the assembly process has been highly successful.

Search for a Light Higgs Boson in Central Exclusive Diffraction: Method and Detectors

By detecting leading protons produced in the Central Exclusive Diffractive process, p+p → p+X+p, one can measure the missing mass, and scan for possible new particle states such as the Higgs boson. This process augments - in a model independent way - the standard methods for new particle searches at the Large Hadron Collider (LHC) and will allow detailed analyses of the produced central system, such as the spin-parity properties of the Higgs boson. The exclusive central diffractive process makes possible precision studies of gluons at the LHC and complements the physics scenarios foreseen at the next e+e− linear collider. This thesis first presents the conclusions of the first systematic analysis of the expected precision measurement of the leading proton momentum and the accuracy of the reconstructed missing mass. In this initial analysis, the scattered protons are tracked along the LHC beam line and the uncertainties expected in beam transport and detection of the scattered leading protons are accounted for. The main focus of the thesis is in developing the necessary radiation hard precision detector technology for coping with the extremely demanding experimental environment of the LHC. This will be achieved by using a 3D silicon detector design, which in addition to the radiation hardness of up to 5×10^15 neutrons/cm2, offers properties such as a high signal-to- noise ratio, fast signal response to radiation and sensitivity close to the very edge of the detector. This work reports on the development of a novel semi-3D detector design that simplifies the 3D fabrication process, but conserves the necessary properties of the 3D detector design required in the LHC and in other imaging applications.

Geant4 Hadronic Cascade Models and CMS Data Analysis : Computational Challenges in the LHC era

This work belongs to the field of computational high-energy physics (HEP). The key methods used in this thesis work to meet the challenges raised by the Large Hadron Collider (LHC) era experiments are object-orientation with software engineering, Monte Carlo simulation, the computer technology of clusters, and artificial neural networks. The first aspect discussed is the development of hadronic cascade models, used for the accurate simulation of medium-energy hadron-nucleus reactions, up to 10 GeV. These models are typically needed in hadronic calorimeter studies and in the estimation of radiation backgrounds. Various applications outside HEP include the medical field (such as hadron treatment simulations), space science (satellite shielding), and nuclear physics (spallation studies). Validation results are presented for several significant improvements released in Geant4 simulation tool, and the significance of the new models for computing in the Large Hadron Collider era is estimated. In particular, we estimate the ability of the Bertini cascade to simulate Compact Muon Solenoid (CMS) hadron calorimeter HCAL. LHC test beam activity has a tightly coupled cycle of simulation-to-data analysis. Typically, a Geant4 computer experiment is used to understand test beam measurements. Thus an another aspect of this thesis is a description of studies related to developing new CMS H2 test beam data analysis tools and performing data analysis on the basis of CMS Monte Carlo events. These events have been simulated in detail using Geant4 physics models, full CMS detector description, and event reconstruction. Using the ROOT data analysis framework we have developed an offline ANN-based approach to tag b-jets associated with heavy neutral Higgs particles, and we show that this kind of NN methodology can be successfully used to separate the Higgs signal from the background in the CMS experiment.

Identification of Hadronically Decaying Tau Leptons in Searches for Heavy MSSM Higgs Bosons with the CMS Detector at the CERN LHC

This thesis describes methods for the reliable identification of hadronically decaying tau leptons in the search for heavy Higgs bosons of the minimal supersymmetric standard model of particle physics (MSSM). The identification of the hadronic tau lepton decays, i.e. tau-jets, is applied to the gg->bbH, H->tautau and gg->tbH+, H+->taunu processes to be searched for in the CMS experiment at the CERN Large Hadron Collider. Of all the event selections applied in these final states, the tau-jet identification is the single most important event selection criterion to separate the tiny Higgs boson signal from a large number of background events. The tau-jet identification is studied with methods based on a signature of a low charged track multiplicity, the containment of the decay products within a narrow cone, an isolated electromagnetic energy deposition, a non-zero tau lepton flight path, the absence of electrons, muons, and neutral hadrons in the decay signature, and a relatively small tau lepton mass compared to the mass of most hadrons. Furthermore, in the H+->taunu channel, helicity correlations are exploited to separate the signal tau jets from those originating from the W->taunu decays. Since many of these identification methods rely on the reconstruction of charged particle tracks, the systematic uncertainties resulting from the mechanical tolerances of the tracking sensor positions are estimated with care. The tau-jet identification and other standard selection methods are applied to the search for the heavy neutral and charged Higgs bosons in the H->tautau and H+->taunu decay channels. For the H+->taunu channel, the tau-jet identification is redone and optimized with a recent and more detailed event simulation than previously in the CMS experiment. Both decay channels are found to be very promising for the discovery of the heavy MSSM Higgs bosons. The Higgs boson(s), whose existence has not yet been experimentally verified, are a part of the standard model and its most popular extensions. They are a manifestation of a mechanism which breaks the electroweak symmetry and generates masses for particles. Since the H->tautau and H+->taunu decay channels are important for the discovery of the Higgs bosons in a large region of the permitted parameter space, the analysis described in this thesis serves as a probe for finding out properties of the microcosm of particles and their interactions in the energy scales beyond the standard model of particle physics.

From the LHC to future colliders

Discoveries at the LHC will soon set the physics agenda for future colliders. This report of a CERN Theory Institute includes the summaries of Working Groups that reviewed the physics goals and prospects of LHC running with 10 to 300 fb(-1) of integrated luminosity, of the proposed sLHC luminosity upgrade, of the ILC, of CLIC, of the LHeC and of a muon collider. The four Working Groups considered possible scenarios for the first 10 fb(-1) of data at the LHC in which (i) a state with properties that are compatible with a Higgs boson is discovered, (ii) no such state is discovered either because the Higgs properties are such that it is difficult to detect or because no Higgs boson exists, (iii) a missing-energy signal beyond the Standard Model is discovered as in some supersymmetric models, and (iv) some other exotic signature of new physics is discovered. In the contexts of these scenarios, the Working Groups reviewed the capabilities of the future colliders to study in more detail whatever new physics may be discovered by the LHC. Their reports provide the particle physics community with some tools for reviewing the scientific priorities for future colliders after the LHC produces its first harvest of new physics from multi-TeV collisions.

Production of psi(2S) Mesons in ppbar Collisions at 1.96 TeV

We have measured the differential cross section for the inclusive production of psi(2S) mesons decaying to mu^{+} mu^{-1} that were produced in prompt or B-decay processes from ppbar collisions at 1.96 TeV. These measurements have been made using a data set from an integrated luminosity of 1.1 fb^{-1} collected by the CDF II detector at Fermilab. For events with transverse momentum p_{T} (psi(2S)) > 2 GeV/c and rapidity |y(psi(2S))| psi(2S)X) Br(psi(2S) -> mu^{+} mu^{-}) to be 3.29 +- 0.04(stat.) +- 0.32(syst.) nb.

Search for exclusive Z boson production and observation of high mass ppbar->gammagamma->p+ll+pbar events in ppbar collisions at sqrt(s) = 1.96 TeV

We present a search for exclusive Z boson production in proton-antiproton collisions at sqrt(s) = 1.96 TeV, using the CDF II detector at Fermilab. We observe no exclusive Z->ll candidates and place the first upper limit on the exclusive Z cross section in hadron collisions, sigma(exclu) gammagamma->p+ll+pbar, and measure the cross section for M(ll) > 40 GeV/c2 and |eta(l)|

SiD Letter of Intent

Letter of intent describing SiD (Silicon Detector) for consideration by the International Linear Collider IDAG panel. This detector concept is founded on the use of silicon detectors for vertexing, tracking, and electromagnetic calorimetry. The detector has been cost-optimized as a general-purpose detector for a 500 GeV electron-positron linear collider.

First Measurement of the b-Jet Cross Section in Events with a W Boson in pp̅ Collisions at √s=1.96 TeV

The cross section for jets from b quarks produced with a W boson has been measured in ppbar collision data from 1.9/fb of integrated luminosity recorded by the CDF II detector at the Tevatron. The W+b-jets process poses a significant background in measurements of top quark production and prominent searches for the Higgs boson. We measure a b-jet cross section of 2.74 +- 0.27(stat.) +- 0.42(syst.) pb in association with a single flavor of leptonic W boson decay over a limited kinematic phase space. This measured result cannot be accommodated in several available theoretical predictions.

Search for R-Parity Violating Decays of Sneutrinos to eμ, μτ, and eτ Pairs in pp̅ Collisions at √s=1.96 TeV

We present a search for tau sneutrino production using the Tevatron ppbar collision data collected with the CDF II detector and corresponding to an integrated luminosity of 1 fb^-1. We focus on the scenarios predicted by the R-parity violating (RPV) supersymmetric models in which tau sneutrinos decay to two charged leptons of different flavor. With the data consistent with the standard model expectations, we set the upper limits on sigma(ppbar -> tau sneutrino)*BR(tau sneutrino ->emu,mutau,etau) and use these results to constrain the RPV couplings as a function of tau sneutrino mass.

Search for New Bottomlike Quark Pair Decays QQ̅ →(tW∓)(t̅ W±) in Same-Charge Dilepton Events

We report the most restrictive direct limits on masses of fourth-generation down-type quarks b′, and quarklike composite fermions (B or T5/3), decaying promptly to tW∓. We search for a significant excess of events with two same-charge leptons (e, μ), several hadronic jets, and missing transverse energy. An analysis of data from pp̅ collisions with an integrated luminosity of 2.7  fb-1 collected with the CDF II detector at Fermilab yields no evidence for such a signal, setting mass limits mb′, mB>338  GeV/c2 and mT5/3>365  GeV/c2 at 95% confidence level.

Search for WW and WZ Resonances Decaying to Electron, Missing ET, and Two Jets in pp̅ Collisions at √s=1.96 TeV.

Using data from 2.9  fb-1 of integrated luminosity collected with the CDF II detector at the Tevatron, we search for resonances decaying into a pair of on-shell gauge bosons, WW or WZ, where one W decays into an electron and a neutrino, and the other boson decays into two jets. We observed no statistically significant excess above the expected standard model background, and we set cross section limits at 95% confidence level on G* (Randall-Sundrum graviton), Z′, and W′ bosons. By comparing these limits to theoretical cross sections, mass exclusion regions for the three particles are derived. The mass exclusion regions for Z′ and W′ are further evaluated as a function of their gauge coupling strength.