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‣ Wh plus missing-E-T signature from gaugino pair production at the LHC

Baer, Howard; Barger, Vernon; Lessa, Andre; Sreethawong, Warintorn; Tata, Xerxes
Fonte: AMER PHYSICAL SOC; COLLEGE PK Publicador: AMER PHYSICAL SOC; COLLEGE PK
Tipo: Artigo de Revista Científica
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In SUSY models with heavy squarks and gaugino mass unification, the gaugino pair production reaction pp -> (W) over tilde (+/-)(1)(Z) over tilde (2) dominates gluino pair production for m (g) over tilde less than or similar to 1 TeV at LHC with root s = 14 TeV (LHC14). For this mass range, the two-body decays (W) over tilde (1) -> W (Z) over tilde (1) and (Z) over tilde (2) -> h (Z) over tilde (1) are expected to dominate the chargino and neutralino branching fractions. By searching for lb (b) over tilde + is not an element of(T) events from (W) over tilde (+/-)(1)Z(2) production, we show that LHC14 with 100 fb(-1) of integrated luminosity becomes sensitive to chargino masses in the range m((W) over tilde1) similar to 450-550 GeV corresponding to m (g) over tilde similar to 1.5-2 TeV in models with gaugino mass unification. For 10(3) fb(-1), LHC14 is sensitive to the Wh channel for m((W) over tilde1) similar to 300-800 GeV, corresponding to m (g) over tilde similar to 1-2.8 TeV, which is comparable to the reach for gluino pair production followed by cascade decays. The Wh + is not an element of(T) search channel opens up a new complementary avenue for SUSY searches at LHC, and serves to point to SUSYas the origin of any new physics discovered via multijet and multilepton + is not an element of(T) channels.; U.S. Department of Energy [DE-FG02-04ER41305...

‣ LHC luminosity measurement with the ATLAS-MPX detectors

Asbah, Nedaa
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
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En opération depuis 2008, l’expérience ATLAS est la plus grande de toutes les expériences au LHC. Les détecteurs ATLAS- MPX (MPX) installés dans ATLAS sont basés sur le détecteur au silicium à pixels Medipix2 qui a été développé par la collaboration Medipix au CERN pour faire de l’imagerie en temps réel. Les détecteurs MPX peuvent être utilisés pour mesurer la luminosité. Ils ont été installés à seize différents endroits dans les zones expérimentale et technique d’ATLAS en 2008. Le réseau MPX a recueilli avec succès des données indépendamment de la chaîne d’enregistrement des données ATLAS de 2008 à 2013. Chaque détecteur MPX fournit des mesures de la luminosité intégrée du LHC. Ce mémoire décrit la méthode d’étalonnage de la luminosité absolue mesurée avec les détectors MPX et la performance des détecteurs MPX pour les données de luminosité en 2012. Une constante d’étalonnage de la luminosité a été déterminée. L’étalonnage est basé sur technique de van der Meer (vdM). Cette technique permet la mesure de la taille des deux faisceaux en recouvrement dans le plan vertical et horizontal au point d’interaction d’ATLAS (IP1). La détermination de la luminosité absolue nécessite la connaissance précise de l’intensité des faisceaux et du nombre de trains de particules. Les trois balayages d’étalonnage ont été analysés et les résultats obtenus par les détecteurs MPX ont été comparés aux autres détecteurs d’ATLAS dédiés spécifiquement à la mesure de la luminosité. La luminosité obtenue à partir des balayages vdM a été comparée à la luminosité des collisions proton- proton avant et après les balayages vdM. Le réseau des détecteurs MPX donne des informations fiables pour la détermination de la luminosité de l’expérience ATLAS sur un large intervalle (luminosité de 5 × 10^29 cm−2 s−1 jusqu’à 7 × 10^33 cm−2 s−1 .; In operation since 2008...

‣ Implementación de un sistema automático para la validación de muones y estudio de la identificación y aislamiento de muones con el detector CMS para el Run II del LHC; Development of an automatic muon validation system and muon identificación and isolation studies with the CMS detector for the Run II of the LHC

Castiñeiras de Saa, Juan Ramón
Fonte: Universidade de Cantabria Publicador: Universidade de Cantabria
Tipo: Dissertação de Mestrado
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RESUMEN: El LHC ha tenido un comportamiento extraordinario durante su primer extenso periodo de toma de datos, el Run I, entre 2010 y 2012, destacando el histórico descubrimiento de una partícula compatible con el bosón de Higgs del Modelo Estándar. Estos resultados no hubieran sido posibles sin la excelente eficiencia de los detectores. En particular, CMS destaca por su capacidad para detectar muones, proporcionando una medida precisa de su momento en un amplio rango de energías y en la máxima aceptancia geométrica posible. Este tipo de objetos presentan una signatura muy limpia en el detector, y además están involucrados en los principales procesos físicos explorados en el LHC, no solo en el marco del Modelo Estándar sino también extensiones tales como la Supersimetría. Para que los datos de los muones detectados puedan ser utilizados en los análisis físicos es necesario aportar garantías sobre la calidad de la reconstrucción de los mismos. En este trabajo se exponen los resultados de la implementación de un método automático para la certificación de datos de muones. Se ha elaborado un test estadístico para comparar muestras de datos de muones con respecto a muestras de referencia, a partir de la distribución del

‣ Measuring heavy neutrino couplings at the LHC

Aguilar-Saavedra, Juan Antonio; Joaquim, F. R.
Fonte: American Physical Society Publicador: American Physical Society
Tipo: Pré-impressão
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The existence of heavy neutrinos mediating neutrino masses via a type-I seesaw can be directly probed at the LHC, or indirectly in rare lepton flavor-violating processes. The synergy between these two approaches requires a direct measurement of the heavy neutrino couplings. We discuss a strategy to perform such measurements at the LHC in the context of left-right symmetric models, which is also applicable to other models implementing a type-I or type-III seesaw. We demonstrate that the ambiguities in the determination of the heavy neutrino mixing parameters can be resolved by performing an exclusive analysis of dilepton final states, discriminated by flavor and missing energy.

‣ Lepton number violation and scalar searches at the LHC

??guila Gim??nez, Francisco del; Chala, Mikael; Santamaria, Arcadi; Wudka, Jose
Fonte: Wydawnictwo Uniwersytetu Jagiellonskiego Publicador: Wydawnictwo Uniwersytetu Jagiellonskiego
Tipo: Artigo de Revista Científica
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We review the SM extensions with scalar multiplets including doubly- charged components eventually observable as di-leptonic resonances at the LHC. Special emphasis is paid to the limits on LNV implied by doubly- charged scalar searches at the LHC, and to the characterization of the multiplet doubly-charged scalars belong to if they are observed to decay into same-sign charged lepton pairs.

‣ Asymmetries in tt?? production: LHC versus Tevatron

Aguilar-Saavedra, Juan Antonio; P??rez-Victoria, Manuel
Fonte: American Physical Society Publicador: American Physical Society
Tipo: Artigo de Revista Científica
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The measurement of a charge asymmetry in tt?? production at the LHC constitutes more than an independent confirmation of the forward-backward asymmetry found at the Tevatron. Indeed, both measurements together can be used to identify the source of the asymmetry. This is demonstrated for the case of new Z???, W??? vector bosons and color-sextet and triplet scalars, exchanged in t, u channels, respectively, and a very heavy axigluon in the s channel. In particular, current LHC measurements disfavor Z???, W??? models above the 2?? level.

‣ Event-by-event Hydrodynamics for LHC; Hidrodinâmica Evento-por-evento para o LHC

Machado, Meera Vieira
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 06/08/2015 Português
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We perform an event-by-event hydrodynamic analysis for Pb-Pb collisions at the incident energy of sqrt(sNN) = 2.76TeV, also studying the effects of two equations of state under the same initial conditions and freeze-out scenario: one characterized by a critical point and the other based on Lattice QCD (Quantum Chromodynamics) calculations. The observables of interest are particle spectra in terms of pseudorapidity and transverse momentum, as well as flow harmonics, which are coefficients that carry information on the initial anisotropies of the system throughout its evolution. Those are computed and compared with experimental Large Hadron Collider (LHC) data. There are slight differences in the results for each equation of state, caused by their distinct features. Lastly, the LHC-based calculations are compared with previous works related to the Relativistic Heavy-Ion Collider (RHIC) experimental data. The main techniques of the latter are performed in this work, which results in differences between some aspects in the outcome for each collision type, from initial energy distributions to freeze-out temperatures.; É feita uma análise de hidrodinâmica evento-por-evento para colisões de Pb-Pb à energia incidente de sqrt(sNN) = 2.76TeV. Estudamos os efeitos de duas equações de estado sob as mesmas condições iniciais e desacoplamento: uma é caracterizada por um ponto crítico e a outra é baseada em cálculos de Lattice QCD (Cromodinâmica Quântica). Os observáveis de interesse são os espectros de partículas em termos da pseudo rapidez e momento transversal...

‣ Recherche d'un neutrino lourd avec le détecteur ATLAS au LHC

Bazid, Houriya
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
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Ce mémoire de maîtrise a pour objet une recherche de leptons lourds de quatrième génération avec les données prises par le détecteur ATLAS au LHC dans les collisions pp à $\sqrt{s}$ = 7 TeV et avec une luminosité intégrée de 1.02 fb$^{-1}$. Le processus étudié est la production au singulet de leptons lourds neutres de quatrième génération (N) par la voie du courant chargé suivi de la désintégration du celui-ci en un électron et un boson W : $ pp \to W \to N e \to e W e \to e e \nu_{\ell} \ell $ ($\ell$ = $e$ ou $\mu$), et dépend d'un paramètre de mélange $\xi^{2}$ avec un lepton léger. L'analyse passe par plusieurs étapes, soit l'utilisation de FeynRules pour construire le modèle pour ensuite générer des événements par MadGraph 5.1.2.4. Comme hypothèse de référence, on a choisi une masse de 100 GeV pour le lepton lourd neutre et $\xi_{Ne}^2$ = 0.19, donnant une section efficace de 0.312 pb pour une énergie au centre de masse de 7 TeV. Puisque la génération du signal s'est faite de manière privée à Montréal et non par la collaboration ATLAS, les résultats ne peuvent pas être reconnus officiellement. Sur la base de la simulation, avec des données correspondant à 1 fb$^{-1}$, la limite supérieure attendue à un niveau de confiance de $95\%$ sur la section efficace du signal est de 0.145 pb avec 0.294 pb pour un écart type($\sigma$) et 0.519 pb pour 2$\sigma$. La limite supérieure attendue à un niveau de confiance de $95\%$ sur $\xi_{Ne}^{2}$ de 0.09 pour une masse de 100 GeV.; This M.Sc. thesis describes a search for fourth generation heavy leptons using data from the ATLAS detector at LHC. The total integrated luminosity is 1.02 fb$^{-1}$ in pp collisions at $\sqrt{s}$ = 7 TeV. This analysis study the single production of fourth generation neutral heavy lepton (N) via the charged channel and where W decays leptonically : $ pp \to W \to N e \to e W e \to e e \nu_{\ell} \ell $ ($\ell$ = $e$ ou $\mu$)...

‣ What to expect when you're expecting: femtoscopy at the LHC

Lisa,Mike
Fonte: Sociedade Brasileira de Física Publicador: Sociedade Brasileira de Física
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2007 Português
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A huge systematics of femtoscopic measurements have been used over the past 20 years to characterize the system created in heavy ion collisions. These measurements cover two orders of magnitude in energy, and with LHC beams imminent, this range will be extended by more than another order of magnitude. Here, I discuss theoretical expectations of femtoscopy of A+A and p+p collisions at the LHC, based on Boltzmann and hydrodynamic calculations, as well as on naive extrapolation of existing systematics.

‣ Nueva física en la tercera generación de quarks en el LHC; Search for new physics in the third generation of quarks at the LHC

Sanchez Vietto, Juan Ignacio
Fonte: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires Publicador: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires
Tipo: Tesis Doctoral Formato: text; pdf
Publicado em //2015 04 30 Português
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El quark top es posiblemente, junto al bosón de Higgs, una de las partículas menos estudiada y comprendida del Modelo Estándar. Menos estudiada porque, hasta el reciente anuncio del descubrimiento del tan buscado bosón de Higgs, fue durante mucho tiempo la última partícula descubierta (en el a˜no 1995 por los experimentos CDF y DØ del Tevatron). Además, comparativamente con otras partículas, su masa de 172 GeV la hace muy difícil de producir copiosamente en los colisionadores con el fin de realizar un estudio estadístico detallado de sus propiedades. Así, pese a los esfuerzos realizados, queda mucho por explorar sobre esta partícula. Y menos comprendida porque su masa es varios ordenes de magnitud más grande que la de cualquiera de los otros fermiones del Modelo Estándar. Con la llegada de la era del LHC (Large Hadron Collider) el quark top esta siendo estudiado como nunca antes, produciendo 80 millones de pares top-antitop por a˜no cuando alcance su luminosidad de dise˜no y examinando sus propiedades a una nueva escala de energías. Existen tanto argumentos experimentales como teóricos que impulsan, no sólo a explorar en profundidad las propiedades del quark top, sino también las de su compa˜nero electrodébil...

‣ Handbook of LHC Higgs Cross Sections: 1. Inclusive Observables

LHC Higgs Cross Section Working Group; Dittmaier, S.; Mariotti, C.; Passarino, G.; Tanaka, R.; Baglio, J.; Bolzoni, P.; Boughezal, R.; Brein, O.; Collins-Tooth, C.; Dawson, S.; Dean, S.; Denner, A.; Farrington, S.; Felcini, M.; Flechl, M.; de Florian, D.;
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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This Report summarizes the results of the first 10 months' activities of the LHC Higgs Cross Sections Working Group. The main goal of the working group was to present the status-of-art on Higgs Physics at the LHC integrating all new results that have appeared in the last few years. The Report is more than a mere collection of the proceedings of the general meetings. The subgroups have been working in different directions. An attempt has been made to present the first Report from these subgroups in a complete and homogeneous form. The subgroups' contributions correspondingly comprise the main parts of the Report. A significant amount of work has been performed in providing higher-order corrections to the Higgs-boson cross sections and pinning down the theoretical uncertainty of the Standard Model predictions. This Report comprises explicit numerical results on total cross sections, leaving the issues of event selection cuts and differential distributions to future publications. The subjects for further study are identified.; Comment: 151 pages, 43 figures. Updated the H->4f branching ratios. This is the final version. Working Group web page: https://twiki.cern.ch/twiki/bin/view/LHCPhysics/CrossSections

‣ Physics Interplay of the LHC and the ILC

Group, LHC/LC Study; :; Weiglein, G.; Barklow, T.; Boos, E.; De Roeck, A.; Desch, K.; Gianotti, F.; Godbole, R.; Gunion, J. F.; Haber, H. E.; Heinemeyer, S.; Hewett, J. L.; Kawagoe, K.; Monig, K.; Nojiri, M. M.; Polesello, G.; Richard, F.; Riemann, S.; St
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 27/10/2004 Português
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Physics at the Large Hadron Collider (LHC) and the International e+e- Linear Collider (ILC) will be complementary in many respects, as has been demonstrated at previous generations of hadron and lepton colliders. This report addresses the possible interplay between the LHC and ILC in testing the Standard Model and in discovering and determining the origin of new physics. Mutual benefits for the physics programme at both machines can occur both at the level of a combined interpretation of Hadron Collider and Linear Collider data and at the level of combined analyses of the data, where results obtained at one machine can directly influence the way analyses are carried out at the other machine. Topics under study comprise the physics of weak and strong electroweak symmetry breaking, supersymmetric models, new gauge theories, models with extra dimensions, and electroweak and QCD precision physics. The status of the work that has been carried out within the LHC / LC Study Group so far is summarised in this report. Possible topics for future studies are outlined.; Comment: 472 pages, a version with high-resolution figures can be found at http://www.ippp.dur.ac.uk/~georg/lhclc/lhclcdoc.ps.gz

‣ Handbook of LHC Higgs Cross Sections: 2. Differential Distributions

LHC Higgs Cross Section Working Group; Dittmaier, S.; Mariotti, C.; Passarino, G.; Tanaka, R.; Alekhin, S.; Alwall, J.; Bagnaschi, E. A.; Banfi, A.; Blumlein, J.; Bolognesi, S.; Chanon, N.; Cheng, T.; Cieri, L.; Cooper-Sarkar, A. M.; Cutajar, M.; Dawson,
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 15/01/2012 Português
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This Report summarises the results of the second year's activities of the LHC Higgs Cross Section Working Group. The main goal of the working group was to present the state of the art of Higgs Physics at the LHC, integrating all new results that have appeared in the last few years. The first working group report Handbook of LHC Higgs Cross Sections: 1. Inclusive Observables (CERN-2011-002) focuses on predictions (central values and errors) for total Higgs production cross sections and Higgs branching ratios in the Standard Model and its minimal supersymmetric extension, covering also related issues such as Monte Carlo generators, parton distribution functions, and pseudo-observables. This second Report represents the next natural step towards realistic predictions upon providing results on cross sections with benchmark cuts, differential distributions, details of specific decay channels, and further recent developments.; Comment: 275 pages, 136 figures, to be submitted to CERN Report. Working Group web page: https://twiki.cern.ch/twiki/bin/view/LHCPhysics/CrossSections

‣ Handbook of LHC Higgs Cross Sections: 3. Higgs Properties

The LHC Higgs Cross Section Working Group; Heinemeyer, S.; Mariotti, C.; Passarino, G.; Tanaka, R.; Andersen, J. R.; Artoisenet, P.; Bagnaschi, E. A.; Banfi, A.; Becher, T.; Bernlochner, F. U.; Bolognesi, S.; Bolzoni, P.; Boughezal, R.; Buarque, D.; Campb
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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This Report summarizes the results of the activities in 2012 and the first half of 2013 of the LHC Higgs Cross Section Working Group. The main goal of the working group was to present the state of the art of Higgs Physics at the LHC, integrating all new results that have appeared in the last few years. This report follows the first working group report Handbook of LHC Higgs Cross Sections: 1. Inclusive Observables (CERN-2011-002) and the second working group report Handbook of LHC Higgs Cross Sections: 2. Differential Distributions (CERN-2012-002). After the discovery of a Higgs boson at the LHC in mid-2012 this report focuses on refined prediction of Standard Model (SM) Higgs phenomenology around the experimentally observed value of 125-126 GeV, refined predictions for heavy SM-like Higgs bosons as well as predictions in the Minimal Supersymmetric Standard Model and first steps to go beyond these models. The other main focus is on the extraction of the characteristics and properties of the newly discovered particle such as couplings to SM particles, spin and CP-quantum numbers etc.; Comment: 404 pages, 139 figures, 162 tables. Updated for author names and minor corrections in the figures and tables. Working Group web page: https://twiki.cern.ch/twiki/bin/view/LHCPhysics/CrossSections

‣ Characterization of irradiated detectors fabricated on p-type silicon substrates for super-LHC

Miñano, Mercedes; Campabadal, Francesca; Escobar, Carlos; García García, Carmen; González Sevilla, Sergio; Lacasta Llácer, Carlos; Lozano Fantoba, Manuel; Martí García, Salvador; Pellegrini, Giulio; Rafí, Joan Marc; Ullán Comes, Miguel
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 2373 bytes; text/plain
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4 pages, 5 figures.-- PACS nrs.: 29.40.−n; 29.40.Wk; 81.40.Wx.-- ISI Article Identifier: 000251861100008; Printed version published on Dec 11, 2007.-- Issue title: Proceedings of the 6th International Conference on Radiation Effects on Semiconductor Materials, Detectors and Devices - RESMDD 2006 (Firenze, Oct 10-13, 2006).; An upgrade of the large hadron collider (LHC), the Super-LHC (SLHC), towards higher luminosities is currently being discussed as an extension of the LHC physics program. The goal of the SLHC is to operate at a luminosity of 10(35) cm(-2) s(-1) (10 times larger than that of the LHC one). Thus, the operation of the SLHC implies a need to upgrade the detectors of the LHC experiments. The current tracking system of ATLAS will not cope with that luminosity. New solutions must be investigated to improve the radiation tolerance of the semiconductor detector. p-Type bulk sensors are being considered for the ATLAS tracking system for the SLHC. Microstrip detectors fabricated by CNM-IMB on p-type high-resistivity float zone silicon have been irradiated with neutrons at the TRIGA Mark II reactor in Ljubljana up to a fluence of 10(16) cm(-2) (as expected in the innermost region of the ATLAS upgrade) and have been characterized at IFIC Laboratory. The collected charge...

‣ QCD studies with ATLAS at the LHC

Mitsou, Vasiliki A.; ATLAS Collaboration
Fonte: Elsevier Publicador: Elsevier
Tipo: Comunicación de congreso Formato: 389245 bytes; application/pdf
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8 pages, 11 figures.-- Prepared for 11th International Conference in Quantum ChromoDynamics (QCD 04), Montpellier, France, 5-9 Jul 2004.-- Published in: Nuclear Physics B Proceedings Supplements 152: 306-313 (2006), final full-text version of the paper available at: http://dx.doi.org/10.1016/j.nuclphysbps.2005.08.060.; The study of QCD processes at the LHC will serve two main goals. First, the predictions of Quantum Chromodynamics will be tested and precision measurements will be performed, allowing additional constraints to be established, and providing measurements of the strong coupling constant. Second, QCD processes represent a major part of the background to other Standard Model processes and signals of new physics at the LHC and therefore need to be understood in depth. An overview of various measurements of QCD-related processes to be performed at the LHC is presented, based on final states containing high-pT leptons, photons and jets. Moreover, possible deviations from QCD predictions indicating presence of new physics are discussed.; The author acknowledges support by the EU funding under the RTN contract: HPRN-CT-2002-00292, Probe for New Physics.; Peer reviewed

‣ Prospects for Scalar Leptoquark Discovery at the LHC

Mitsou, Vasiliki A.; Benekos, N. Ch.; Panagoulias, I.; Papadopoulou, Th. D.
Fonte: Springer Publicador: Springer
Tipo: Pre-print Formato: 182261 bytes; application/pdf
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Submitted on 15 Nov 2004 (v1), last revised 2 Nov 2005 (this version, v2, with corrected typos and added content).-- 8 pages, 2 figures.-- PACS numbers: 12.60.-i, 13.85.Rm, 14.80.-j.-- Prepared for Conference on Physics at LHC, Vienna, Austria, 13-17 Jul 2004.-- Published in: Czechoslovak Journal of Physics 55: B659-B666 (2005).; The discovery potential of the ATLAS detector for scalar leptoquark pair production at the LHC is discussed in this paper. The study is performed using a parameterized yet realistic simulation of the ATLAS detector response for the signal and the background. The channel LQLQ -> (lq)(lq), where l=e,μ, is investigated for the first two generations and the decay mode LQLQ -> (v_τ b)(v_τ b) for the third one. In both cases, a preliminary mass reach is found to be ~1.3 TeV for three years of LHC running at low luminosity.; This work has been performed within the ATLAS Collaboration and we thank collaboration members for helpful discussions, and in particular the convenors of the ATLAS Exotics working group, G. Azuelos, S. Ferrag and G. Brooijmans, for their comments and suggestions. The work of V.A.M. is supported by the EU funding under the RTN contract: HPRN-CT-2002-00292, Probe for New Physics.; Peer reviewed

‣ Probing new physics at the LHC: searches for heavy top-like quarks with the ATLAS experiment

Succurro, Antonella; Casado Lechuga, María Pilar
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
Publicado em //2014 Português
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¿Es el Modelo Estándar (Standard Model o SM) de las partículas elementales completo? Al parecer, la respuesta es "no". Un gran número de teorías intentando dar respuestas a preguntas como por ejamplo cuál es la naturaleza de la materia oscura, o cuál es la razón por la que el bosón de Higgs es tan ligero, han sido propuestas. Ahora que el Large Hadron Collider (LHC) en el CERN está en pleno funcionamiento, experimentos como ATLAS son capaces de explorar regímenes de muy alta energía, donde se puede testear la presencia de nueva física. El trabajo presentado en esta tesis consta de dos análisis diseñados para descubrir (o excluir) la existencia de una nueva partícula: un quark similar al quark top (la partícula más pesada del SM), "top-like", pero con una masa mucho más alta. Este nuevo quark exótico podría ser una simple réplica del quark top del SM, sólo mas masivo, es decir, una cuarta generación quiral de up-type quark, o podría tener una naturalez aún más exótica. Esta última hipótesis es particularmente interesante ya que muchas extensiones del SM predicen nuevos quarks llamados "vectoriales". Ambas búsquedas están basadas en el análisis de una muestra parcial de los datos acumulados por el experimento ATLAS en colisiones protón-protón durante el año 2012. Estos resultados están documentados en dos notas públicas (ATLAS-CONF-2013-018 y ATLAS-CONF-2013-060) y en la actualidad se están actualizando con las estadísticas completas. Estos análisis también son parte de un esfuerzo combinado de diferentes equipos de investigación dentro del grupo de trabajo ATLAS Exóticos...

‣ Determining the spin of supersymmetric particles at the LHC using lepton charge asymmetry.

Barr, Alan
Fonte: HEP, Cavendish Laboratory, University of Cambridge Publicador: HEP, Cavendish Laboratory, University of Cambridge
Tipo: Article; not applicable
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If signals suggesting supersymmetry (SUSY) are discovered at the LHC then it will be vital to measure the spins of the new particles to demonstrate that they are indeed the predicted super-partners. A method is discussed by which the spins of some of the SUSY particles can be determined. Angular distributions in sparticle decays lead to charge asymmetry in lepton-jet invariant mass distributions. The size of the asymmetry is proportional to the primary production asymmetry between squarks and anti-squarks. Monte Carlo simulations are performed for a particular mSUGRA model point at the LHC. The resultant asymmetry distributions are consistent with a spin-0 slepton and a spin- 1 2 ? 0 2, but are not consistent with both particles being scalars.

‣ Massive Metastable Charged (S)Particles at the LHC

Raklev, Are R.
Fonte: HEP/DAMTP, University of Cambridge Publicador: HEP/DAMTP, University of Cambridge
Tipo: Article; not applicable
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This brief review deals with recent interest in the prospects of observing a Massive Metastable Charged Particle (MMCP) at the Large Hadron Collider (LHC), and measuring its properties there. We discuss the motivation for scenarios with MMCPs in a phenomenological context, focusing on supersymmetric models that allow us to explore the expected experimental signatures of MMCPs at the LHC. We review current bounds and give estimates of the LHC reach in terms of MMCP masses.