Página 1 dos resultados de 3740 itens digitais encontrados em 0.012 segundos

## Measurement of the electroweak production of dijets in association with a Z-boson and distributions sensitive to vector boson fusion in proton-proton collisions at s√= 8 TeV using the ATLAS detector

Onofre, A.; ATLAS Collaboration
Fonte: Springer Berlin Heidelberg Publicador: Springer Berlin Heidelberg
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.31%
Measurements of fiducial cross sections for the electroweak production of two jets in association with a Z-boson are presented. The measurements are performed using 20.3 fb−1 of proton-proton collision data collected at a centre-of-mass energy of s√ = 8 TeV by the ATLAS experiment at the Large Hadron Collider. The electroweak component is extracted by a fit to the dijet invariant mass distribution in a fiducial region chosen to enhance the electroweak contribution over the dominant background in which the jets are produced via the strong interaction. The electroweak cross sections measured in two fiducial regions are in good agreement with the Standard Model expectations and the background-only hypothesis is rejected with significance above the 5σ level. The electroweak process includes the vector boson fusion production of a Z-boson and the data are used to place limits on anomalous triple gauge boson couplings. In addition, measurements of cross sections and differential distributions for inclusive Z-boson-plus-dijet production are performed in five fiducial regions, each with different sensitivity to the electroweak contribution. The results are corrected for detector effects and compared to predictions from the Sherpa and Powheg event generators.

## Measurement of differential production cross-sections for a Z boson in association with b-jets in 7 TeV proton-proton collisions with the ATLAS detector

Onofre, A.; ATLAS Collaboration
Fonte: Springer Berlin Heidelberg Publicador: Springer Berlin Heidelberg
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.33%
Measurements of differential production cross-sections of a Z boson in association with b-jets in pp collisions at √ s = 7 TeV are reported. The data analysed correspond to an integrated luminosity of 4.6 fb−1 recorded with the ATLAS detector at the Large Hadron Collider. Particle-level cross-sections are determined for events with a Z boson decaying into an electron or muon pair, and containing b-jets. For events with at least one b-jet, the cross-section is presented as a function of the Z boson transverse momentum and rapidity, together with the inclusive b-jet cross-section as a function of b-jet transverse momentum, rapidity and angular separations between the b-jet and the Z boson. For events with at least two b-jets, the cross-section is determined as a function of the invariant mass and angular separation of the two highest transverse momentum b-jets, and as a function of the Z boson transverse momentum and rapidity. Results are compared to leading-order and next-to-leading-order perturbative QCD calculations.

## A measurement of the Z forward-backward charge asymmetry in proton-antiproton decaying to electron-positron

Lee, Jedong ; McFarland, Kevin
Fonte: University of Rochester Publicador: University of Rochester
Tipo: Tese de Doutorado Formato: Number of Pages:125
ENG
Relevância na Pesquisa
56.12%
Thesis (Ph. D.)--University of Rochester. Dept. of Physics and Astronomy, 2006.; We present a measurement of the Z boson forward-backward charge asymmetry of the process pp¯ [arrow right] [gamma]*/ Z + X [arrow right] e + e - + X , where the mass of the intermediate [gamma]*/ Z has invariant mass above 30 GeV/c 2 . The measurement uses 0.36 fb -1 of Run II data. The method of matrix inversion is used to correct for the distortion in the measurement caused by the detector resolution and photon radiation in the final state. A search for a new physics based upon the forward-backward asymmetry is also presented.

## Measurement of Z boson production in Pb-Pb collisions at √(s(NN))=2.76 TeV with the ATLAS detector; Measurement of Z boson production in Pb-Pb collisions at root(s(NN))=2.76 TeV with the ATLAS detector

Jackson, P.; Soni, N.; White, M.
Fonte: American Physical Soc Publicador: American Physical Soc
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.31%
The ATLAS experiment has observed 1995 Z boson candidates in data corresponding to 0.15 nb⁻¹ of integrated luminosity obtained in the 2011 LHC Pb+Pb run at √(s(N)(N))= 2.76 TeV. The Z bosons are reconstructed via dielectron and dimuon decay channels, with a background contamination of less than 3%. Results from the two channels are consistent and are combined. Within the statistical and systematic uncertainties, the per-event Z boson yield is proportional to the number of binary collisions estimated by the Glauber model. The elliptic anisotropy of the azimuthal distribution of the Z boson with respect to the event plane is found to be consistent with zero.; G. Aad ... P. Jackson ... et al. (ATLAS Collaboration)

## Medida de la sección eficaz de producción del bosón Z en el experimento CMS del LHC

Iglesias Santamaría, Marta
Tipo: Trabalho de Conclusão de Curso
SPA
Relevância na Pesquisa
46.32%
En este trabajo se presenta el análisis llevado a cabo para la medida del valor de la sección eficaz de producción del bosón Z (σz), boson “gauge” portador de la corriente neutra de la fuerza electrodébil, a una energía de √s=8 TeV (centro de masas). Para ello se ha utilizado una luminosidad integrada de 5.3 fb-1 de datos recogidos por el detector Compact Muon Solenoid (CMS), situado en el colisionador de hadrones LHC del laboratorio CERN (Ginebra, Suiza). Los resultados obtenidos de la sección eficaz de producción del bosón Z para estos dos canales son: σ(z→e+e-)=1.125±0.001(stat)±0.013(sys)±0.050(lumi) nb σ(z→μ+μ-)=1.162±0.001(stat)±0.026(sys)±0.051(lumi) nb los cuales son compatibles con los valores predichos por el ME y con los valores obtenidos de manera oficial por la colaboración CMS.; Grado en Física

## A note on the rare decay of a Higgs boson into photons and a $Z$ boson

Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.36%
We have calculated the width of the rare decay $H\to\gamma\gamma Z$ at one-loop level in the standard model for Higgs boson masses in the range $115 {\rm GeV} \leq m_H \leq 160 {\rm GeV}$ . For this range of Higgs boson masses we find that $Z$ boson is predominantly longitudinally polarized, and the photons have the same helicity. A comparison of the decay width $\Gamma(H\to \gamma\gamma Z)$ to those of $H\to\gamma\gamma$ and $H\to\gamma Z$ shows that, for the Higgs boson mass of $m_H \sim 135 \rm{GeV}$, the ratios of the decay widths are $\Gamma(H\to\gamma\gamma Z) / \Gamma(H\to\gamma\gamma) \sim \Gamma(H\to\gamma\gamma Z) / \Gamma(H\to\gamma Z) \sim 10^{-5}-10^{-6}$.; Comment: 4 pages, 5 figures, RevTeX

## Measurement of the forward $Z$ boson production cross-section in $pp$ collisions at $\sqrt{s}$ = 7 TeV

LHCb collaboration; Aaij, R.; Adeva, B.; Adinolfi, M.; Affolder, A.; Ajaltouni, Z.; Akar, S.; Albrecht, J.; Alessio, F.; Alexander, M.; Ali, S.; Alkhazov, G.; Cartelle, P. Alvarez; Alves Jr, A. A.; Amato, S.; Amerio, S.; Amhis, Y.; An, L.; Anderlini, L.;
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.22%

## Search for the SM Higgs boson in the (W/Z)H channel with H → bb using the ATLAS detector at the LHC

González Parra, Garoé
Fonte: [Barcelona] : Universitat Autònoma de Barcelona, Publicador: [Barcelona] : Universitat Autònoma de Barcelona,
Tipo: Tesis i dissertacions electròniques; info:eu-repo/semantics/doctoralThesis; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Relevância na Pesquisa
46.48%
Esta tesis presenta los últimos resultados de ATLAS en la búsqueda del bosón de Higgs del Modelo Estándar (SM) en su decaimiento a un par de quarks-b. La búsqueda del bosón de Higgs se realiza en los canales de producción asociados con un bosón vectorial W o Z en el estado final. Ésta incluye el decaimiento leptónico (electrón y muón) del bosón vectorial además del canal en el que el bosón Z decae a un par de neutrinos. En particular, este documento se centra en el canal ZH (Z → νν and H → bb). El análisis utiliza todos los datos generados por colisiones de protones en el experimento ATLAS a √s = 7TeV y √s = 8 TeV. El análisis se basa en una compleja caracterización de eventos en función del modo de decaimiento del bosón vectorial, el número de jets y de b-jets en el estado final, y el momento transverso del bosón vectorial. Esto permite hacer un estudio detallado de los principales procesos de fondo. Dos enfoques diferentes se consideran para el análisis: la utilización de la distribución de mbb como variable principal de discriminación o el uso de una técnica multivariante de redes neuronales. El análisis utiliza una compleja estrategia de ajuste de datos y predicciones de fondo en regiones de control y señal que posibilita constreñir los procesos de fondo...

## Estimation of the Z->vv background to New Physics searches in ATLAS

Sandoval, Tanya
Fonte: University of Cambridge; Department of Physics; Wolfson College; CERN; Cavendish Laboratory Publicador: University of Cambridge; Department of Physics; Wolfson College; CERN; Cavendish Laboratory
Tipo: Thesis; doctoral; PhD
EN
Relevância na Pesquisa
56.09%
This thesis describes a series of studies related to searches for new phenomena, beyond the Standard Model of particle physics, in high energy hadron collisions. In such searches, it becomes crucial to identify the Standard Model backgrounds in order to resolve a potential new signal. The thesis presents a method that uses photon events to determine one of such backgrounds, caused by the production of Z boson events. The studies performed to validate the method, both theoretically and experimentally, are presented and the method was shown to be successful as well as to provide reliable results. Theoretically, the method is found to be robust up to a ~10% uncertainty. Experimentally, the method is implemented to estimate the Z(vv) + jets background for the SUSY 0l + E_T^miss + jets search in the ATLAS experiment at the Large Hadron Collider, where this background is one of the most important components for the final sensitivity and is impossible to measure directly. The main experimental results presented are the latest from ATLAS at the time of writing, corresponding to the full dataset of proton-proton collisions delivered by the LHC in 2011 (4.7 fb^-1) at a centre of mass energy of 7 TeV. Given that this method has been mainstream since 2010...

## Measurement of the cross-section for b-jets produced in association with a Z boson at √s = 7 TeV with the ATLAS detector

Aad, G.; Gray, H. M.; Marshall, Z.; Mateos, D. Lopez; Perez, K.
Tipo: Article; PeerReviewed Formato: application/pdf
Relevância na Pesquisa
56.22%
A measurement is presented of the inclusive cross-section for b-jet production in association with a Z boson in pp collisions at a centre-of-mass energy of √s = 7TeV. The analysis uses the data sample collected by the ATLAS experiment in 2010, corresponding to an integrated luminosity of approximately 36 pb^(−1). The event selection requires a Z boson decaying into high p_T electrons or muons, and at least one b-jet, identified by its displaced vertex, with transverse momentum p_T>25 GeV and rapidity |y|<2.1. After subtraction of background processes, the yield is extracted from the vertex mass distribution of the candidate b-jets. The ratio of this cross-section to the inclusive Z cross-section (the average number of b-jets per Z event) is also measured. Both results are found to be in good agreement with perturbative QCD predictions at next-to-leading order.

## Search for Pair Production of a New b' Quark that Decays into a Z Boson and a Bottom Quark with the ATLAS Detector

Aad, G.; Gray, H. M.; Marshall, Z.; Mateos, D. Lopez; Perez, K.
Fonte: American Physical Society Publicador: American Physical Society
Tipo: Article; PeerReviewed Formato: application/pdf