131 research outputs found

    Jets in Deep-Inelastic Scattering at HERA and determinations of αs\alpha_s

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    Several methods to extract the strong coupling constant αs\alpha_s by means of highly energetic jets in Deep-Inelastic Scattering are presented. The results from the various methods agree with one another and with the world average. The errors are competetive to those achieved in αs\alpha_s determinations in other processes such as proton--anti-proton scattering.Comment: Proceedings of talk given at Lake Louise Winter Institute 2004, Alberta, Canad

    Studying Low-x Dynamics using the Hadronic Final State in DIS at HERA

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    This article describes different approaches to investigate the behavior of parton evolution in the proton by exploiting various aspects of the hadronic final state produced in Deep Inelastic Scattering Events at HERA.Comment: 3 Pages, 5 Figures. To appear in the proceedings of International Europhysics Conference on High-Energy Physics (HEP 2003), Aachen, Germany, 17-23 Jul 200

    Coherent noise source identification in multi channel analysis

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    The evaluation of coherent noise can provide useful information in the study of detectors. The identification of coherent noise sources is also relevant for uncertainty calculations in analyse where several channels are combined. The study of the covariance matrix give information about coherent noises. Since covariance matrix of high dimension data could be difficult to analyse, the development of analysis tools is needed. Principal Component Analysis (PCA) is a powerful tool for such analysis. It has been shown that we can use PCA to find coherent noises in ATLAS calorimeter or the CALICE Si-W electromagnetic calorimeter physics prototype. However, if several coherent noise sources are combined, the interpretation of the PCA may become complicated. In this paper, we present another method based on the study of the covariance matrix to identify noise sources. This method has been developed for the study of front end ASICs dedicated to CALICE calorimeters. These calorimeters are designed and studied for experiments at the ILC. We also study the reliability of the method with simulations. Although this method has been developped for a specific application, it can be used for any multi channel analysis.Comment: Public version of the CALICE Internal Note CIN-02

    CP-violating top quark couplings at future linear e+ee^+e^- colliders

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    We study the potential of future lepton colliders to probe violation of the CP symmetry in the top quark sector. In certain extensions of the Standard Model, such as the two-Higgs-doublet model (2HDM), sizeable anomalous top quark dipole moments can arise, that may be revealed by a precise measurement of top quark pair production. We present results from detailed Monte Carlo studies for the ILC at 500~\GeV{} and CLIC at 380~\gev{} and use parton-level simulations to explore the potential of high-energy operation. We find that precise measurements in e+ettˉe^+e^- \rightarrow t\bar{t} production with subsequent decay to lepton plus jets final states can provide sufficient sensitivity to detect Higgs-boson-induced CP violation in a viable two-Higgs-doublet model. The potential of a linear e+ee^+e^- collider to detect CP-violating electric and weak dipole form factors of the top quark exceeds the prospects of the HL-LHC by over an order of magnitude

    Physics Case for the International Linear Collider

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    We summarize the physics case for the International Linear Collider (ILC). We review the key motivations for the ILC presented in the literature, updating the projected measurement uncertainties for the ILC experiments in accord with the expected schedule of operation of the accelerator and the results of the most recent simulation studies.Comment: 37 pages, 12 figures, 2 tables; v2 - updates of reference

    Report of the Topical Group on Electroweak Precision Physics and Constraining New Physics for Snowmass 2021

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    The precise measurement of physics observables and the test of their consistency within the standard model (SM) are an invaluable approach, complemented by direct searches for new particles, to determine the existence of physics beyond the standard model (BSM). Studies of massive electroweak gauge bosons (W and Z bosons) are a promising target for indirect BSM searches, since the interactions of photons and gluons are strongly constrained by the unbroken gauge symmetries. They can be divided into two categories: (a) Fermion scattering processes mediated by s- or t-channel W/Z bosons, also known as electroweak precision measurements; and (b) multi-boson processes, which include production of two or more vector bosons in fermion-antifermion annihilation, as well as vector boson scattering (VBS) processes. The latter categories can test modifications of gauge-boson self-interactions, and the sensitivity is typically improved with increased collision energy. This report evaluates the achievable precision of a range of future experiments, which depend on the statistics of the collected data sample, the experimental and theoretical systematic uncertainties, and their correlations. In addition it presents a combined interpretation of these results, together with similar studies in the Higgs and top sector, in the Standard Model effective field theory (SMEFT) framework. This framework provides a model-independent prescription to put generic constraints on new physics and to study and combine large sets of experimental observables, assuming that the new physics scales are significantly higher than the EW scale.Comment: 55 pages; Report of the EF04 topical group for Snowmass 202
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