A. Ruiz-Jimeno

The Compact Linear Collider (CLIC) is an option for a future e+e- collider operating at centre-of-mass energies up to 3 TeV, providing sensitivity to a wide range of new physics phenomena and precision physics measurements at the energy frontier. This paper is the first comprehensive presentation of the Higgs physics reach of CLIC operating at three energy stages: sqrt(s) = 350 GeV, 1.4 TeV and 3 TeV. The initial stage of operation allows the study of Higgs boson production in Higgsstrahlung (e+e- -> ZH) and WW-fusion (e+e- -> Hnunu), resulting in precise measurements of the production cross sections, the Higgs total decay width Gamma_H, and model-independent determinations of the Higgs couplings. Operation at sqrt(s) > 1 TeV provides high-statistics samples of Higgs bosons produced through WW-fusion, enabling tight constraints on the Higgs boson couplings. Studies of the rarer processes e+e- -> ttH and e+e- -> HHnunu allow measurements of the top Yukawa coupling and the Higgs boson self-coupling. This paper presents detailed studies of the precision achievable with Higgs measurements at CLIC and describes the interpretation of these measurements in a global fit.

A bstract The Compact Linear Collider (CLIC) is a proposed future high-luminosity linear electron-positron collider operating at three energy stages, with nominal centre-of-mass energies $$ \sqrt{s} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math> = 380 GeV, 1 . 5 TeV, and 3 TeV. Its aim is to explore the energy frontier, providing sensitivity to physics beyond the Standard Model (BSM) and precision measurements of Standard Model processes with an emphasis on Higgs boson and top-quark physics. The opportunities for top-quark physics at CLIC are discussed in this paper. The initial stage of operation focuses on top-quark pair production measurements, as well as the search for rare flavour-changing neutral current (FCNC) top-quark decays. It also includes a top-quark pair production threshold scan around 350 GeV which provides a precise measurement of the top-quark mass in a well-defined theoretical framework. At the higher-energy stages, studies are made of top-quark pairs produced in association with other particles. A study of t ̄ tH production including the extraction of the top Yukawa coupling is presented as well as a study of vector boson fusion (VBF) production, which gives direct access to high-energy electroweak interactions. Operation above 1 TeV leads to more highly collimated jet environments where dedicated methods are used to analyse the jet constituents. These techniques enable studies of the top-quark pair production, and hence the sensitivity to BSM physics, to be extended to higher energies. This paper also includes phenomenological interpretations that may be performed using the results from the extensive top-quark physics programme at CLIC.

This paper summarizes the physics potential of the CLIC high-energy e+e- linear collider. It provides input to the Snowmass 2013 process for the energy-frontier working groups on The Higgs Boson (HE1), Precision Study of Electroweak Interactions (HE2), Fully Understanding the Top Quark (HE3), as well as The Path Beyond the Standard Model -- New Particles, Forces, and Dimensions (HE4). It is accompanied by a paper describing the CLIC accelerator study, submitted to the Frontier Capabilities group of the Snowmass process.

Drell-Yan lepton pairs are produced in the process $p\bar{p} \rightarrow \mu^+\mu^- + X$ through an intermediate $\gamma^*/Z$ boson. The forward-backward asymmetry in the polar-angle distribution of the $\mu^-$ as a function of the invariant mass of the $\mu^+\mu^-$ pair is used to obtain the effective leptonic determination $\sin^2 \theta^{lept}_{eff}$ of the electroweak-mixing parameter $\sin^2 \theta_W$, from which the value of $\sin^2 \theta_W$ is derived assuming the standard model. The measurement sample, recorded by the Collider Detector at Fermilab (CDF), corresponds to 9.2 fb-1 of integrated luminosity from $p\bar{p}$ collisions at a center-of-momentum energy of 1.96 TeV, and is the full CDF Run II data set. The value of $\sin^2 \theta^{lept}_{eff}$ is found to be 0.2315 +- 0.0010, where statistical and systematic uncertainties are combined in quadrature. When interpreted within the context of the standard model using the on-shell renormalization scheme, where $\sin^2 \theta_W = 1 - M_W^2/M_Z^2$, the measurement yields $\sin^2 \theta_W$ = 0.2233 +- 0.0009, or equivalently a W-boson mass of 80.365 +- 0.047 GeV/c^2. The value of the W-boson mass is in agreement with previous determinations in electron-positron collisions and at the Tevatron collider.

We present the second in a series of studies into the forward tracking system for a future linear e+e− collider with a center-of-mass energy in the range from 250 GeV to 3 TeV. In this note a number of specific challenges are investigated, which have caused a degradation of the tracking and vertexing performance in the forward region in previous experiments. We perform a quantitative analysis of the dependence of the tracking performance on detector design parameters and identify several ways to mitigate the performance loss for charged particles emitted at shallow angle.

In a series of notes we explore the detector requirements of the forward tracking region for a future e+e− collider with a center-of-mass energy in the range from 500 GeV to 3 TeV. In this first part we investigate the relevance of the forward region for a range of physics processes that are likely to be relevant in such a machine. We find that many examples can be found where excellent performance of the forward detector system may lead to a considerable increase of the physics output of the experiment. A particularly clear physics case can be made for the reconstruction of electrons at small polar angle.

The Compact Linear Collider (CLIC) is a high-energy high-luminosity linear electron-positron collider under development. It is foreseen to be built and operated in three stages, at centre-of-mass energies of 380 GeV, 1.5 TeV and 3 TeV, respectively. It offers a rich physics program including direct searches as well as the probing of new physics through a broad set of precision measurements of Standard Model processes, particularly in the Higgs-boson and top-quark sectors. The precision required for such measurements and the specific conditions imposed by the beam dimensions and time structure put strict requirements on the detector design and technology. This includes low-mass vertexing and tracking systems with small cells, highly granular imaging calorimeters, as well as a precise hit-time resolution and power-pulsed operation for all subsystems. A conceptual design for the CLIC detector system was published in 2012. Since then, ambitious R&amp;D programmes for silicon vertex and tracking detectors, as well as for calorimeters have been pursued within the CLICdp, CALICE and FCAL collaborations, addressing the challenging detector requirements with innovative technologies. This report introduces the experimental environment and detector requirements at CLIC and reviews the current status and future plans for detector technology R&amp;D.

An overview of the present activities and long-term R&amp;D plans of the Spanish network for future linear accelerators aiming to design and construct the Forward Tracker Detector (FTD) system of ILD, is shown

An overview of some progress and R&amp;D activities of the Spanish network for future accelerators concerning the forward tracker detector of the International Large Detector is shown.

A search for rare decays of Bd,s→μ+μ−, e+e−, e+μ− and D0→μ+μ− in pp̄ collisions at s = 1.96 TeV collected by the CDF detector at Fermilab Tevatron Collider is reported, using 0.36–3.7 fb−1 of integrated luminosity. As no significant excess is observed we present the upper limits obtained.

An overview of the present and foreseen R&amp;D activities of the Spanish network for future accelerators aiming to participate in the design and construction of the forward tracker and vertex detectors of the Future Linear Colliders, is shown.

El desarrollo de este texto es, en gran parte, subjetivo y alimentado por la experiencia del autor, tras casi cincuenta años ligado a la Universidad de Cantabria y el Instituto de Física, centro mixto del CSIC y la UC. También recoge opiniones y comentarios de otros miembros de la Facultad de Ciencias, en torno a la estrategia ligada a la internacionalización. La experiencia del autor, como formador de nuevos investigadores y participante activo de la asociación europea de universidades (EUA) y del foro doctoral de dicha asociación EUA-CDE, se refleja en la exposición sobre la internacionalización y su relación con otros aspectos importantes de la construcción del Espacio Europeo de Educación Superior y del Espacio Europeo de Investigación. Se destaca el buen hacer de la UC por su potenciación de la internacionalización, así como las trabas burocráticas y administrativas del entorno para atraer y retener estudiantes e investigadores de otros países. Los temas tratados en el texto se refieren a aspectos de movilidad y formación, globalización de la actividad científica, infraestructuras y soporte industrial e institucional, comunicación y oportunidades culturales, trabajo en equipo, cultura, diversidad, cooperación internacional y desarrollo sostenible, problemas globales y actividades relacionadas, así como evolución desde los inicios, relaciones entre ciencias y humanidades, futuro… Todos ellos, desde el prisma de la experiencia del autor, incluyendo ejemplos concretos, fundamentalmente, en el contexto de las Ciencias.

Abstract

A FFNN has been used to classify the 1-prong (tau) decays. The net is able to separate hadronic decays from leptonic with 90% efficiency and 93% purity. Applied to the data taken by the DELPHI detector at LEP collider during 1992, the (tau) inclusive 1-prong hadronic branching ratio has been measured to be B_1h equals 0.5050 +/- 0.0032_-0.0031^+0.0046.