ABSTRACT This is the abstract of our nice paper that will describe the requirements and design concepts of a detector for the FCC-ee accelerator. To do match the fabulous statistical precision of the FCC-ee extremely good detector performnace is required. The detector features a 2 T solenoidal field, will have a ultralight silicon vertex detetor, a large gas drift volume, and electromagnetic and hadronic calorimeter sections. Details will be given also on the luminosity measurement.

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MOTIVATIONS FOR ANALYSIS PRESERVATION AND REPRODUCIBILITY The reproducibility of published results is one of the cornerstones of the scientific method: if a group of scientists have discovered something genuinely new about the world, another group should be able to follow their methodology and reproduce the result.[1] This fact is generally acknowledged by both individual scientists and funding agencies. Indeed the ability or otherwise of scientists to reproduce each other’s work is itself an active field of research . These considerations apply to High Energy Physics (HEP) as much as to any other field. However, some of the specific features of HEP mean that reproducibility in HEP takes on significantly different forms to reproducibility in many other fields. First of all, the scale, cost, and construction time of HEP experiments means that it is rarely possible for a new group of physicists to build a dedicated experiment simply to reproduce an existing result, however interesting it may be. Secondly, the size of HEP collaborations means that there are generally several quasi-independent[2] groups of scientists working on any given analysis, and as part of this work naturally trying to reproduce and improve upon each other’s work. For these reasons, analysis reproducibility in the HEP context has certain specific features, and addresses several knowledge-transfer problems that occur at very different time-scales. In particular, because the detector and analysis documentation internal to the collaboration can stretch to thousands of pages, it is not possible to fully describe HEP analyses in even the most verbose journal paper in a way which would allow them to be reproduced later. For this reason, analysis reproducibility in HEP is inextricably linked to the _preservation_ of analysis datasets and code, in a way which is not true of many other scientific fields. The problems addressed by analysis preservation and reproducibility in HEP are Collaborative working: The use of an integrated analysis preservation framework allows all members of the analysis team to have access to the full software suite. This encourages continuous development and integration, gaining time by not having to “wait” for other analysts to have finished their contribution. A significant benefit will be that new students will get running examples of analysis code when they join an analysis or continue work from their predecessors. This will improve their learning experience and get them faster into a productive state. Knowledge preservation during review: On several occasions, changes requested by reviewers caused significant problems as part of the analysis procedures have been lost. The delay in the Δmd analysis between the conference note  and the paper  was an example. Knowledge transfer to other analysis teams: When updating an analysis, the first task is to restore the analysis framework of the previous iteration. This should be painless, but often is not. Considerable time was for instance wasted re-implementing Bs → μ+μ− analysis software of Ref.  when preparing for Ref. . The same applies to groups performing similar analyses. Many effort is spent in LHCb re-implementing tools that could be shared. This should be particularly encouraged for analyses where a control (or signal) mode is shared. It is not rare that comparing results that appear inconsistent is more complicated than it should. The comparison of Refs.  and  on B → K+π−μ+μ− decays is a recent example resulting in the need to publish an erratum . Knowledge transfer to “future generations”: While this is the initial motivation of analysis preservation, we have no LHCb experience yet. Yet there are many examples in the past of analyses that were difficult to replicate. In some cases, the use of RECAST  or similar frameworks allowing tests of new models is also desirable. Having introduced the problem, Sec. [sec:preservation] will now define the scope of what we mean by analysis preservation, before Sec. [sec:cernanapresinfra] introduces the CERN infrastructure dedicated to analysis preservation and reproducibility. Section [sec:roadmap] presents a set of best practices for analysis preservation. We also point out the benefits an analysis team gains from the adoption of those practices for their day-to-day business during the development and review of an analysis. Finally Sec.  [sec:techniques] contains recommendations, which technologies and tools should be used to implement the outlined practices. These recommendations are based on an extensive evaluation of different technologies by representatives of the physics working groups and take into account the global CERN strategy for analysis preservation. [1] Here and throughout we are primarily concerned with the reproducibility of experimental results, although there are theoretical domains, particularly those involving large-scale computing like Lattice QCD, where similar considerations may apply. [2] All work within HEP collaborations relies on shared analysis and detector calibration tools, and in this sense analysis groups inside a collaboration can never be truly independent of each other. There is always potential for shared mistaken assumptions to creep in and bias everyone’s work. On the other hand, the international nature of collaborations means that such analysis groups are generally not only fully independent in terms of funding, but have an active interest in finding problems in each other’s work in order to assert their own primacy in front of the outside world.

VISION AND GOALS The vision of PHASE is to enable joint analyses of hadronic processes across multiple experiments and multiple data sets. It provides a forum and infrastructure for joint developments within the hadron physics community and defines best practices. To make progress in the understanding of strong interaction phenomena, it is necessary to combine the information gathered by several experiments across a wide range of energies in a coherent fashion. Due to the complexity of hadron dynamics, this is a non-trivial problem. Current state-of-the-art techniques for extracting hadronic amplitudes from data exhibit model dependencies, which need to be quantified. Amplitude parameterisations have to be made consitent across different experiments. Only then will the envisioned global analyses become possible. One of the main reasons for the difficulties currently experienced is, that in hadronic decays often many processes are coupled together. For a comprehensive treatment, all of them need to be taken into account, while each analysis typically only investigates a single final state. It is at this point that combining data from different experiments will have the biggest impact, as now each channel can be constrained from the experimental data, which is most sensitive to that particular hadronic system. PHASE will bring together expertise and data from both the baryon and meson sectors. To advance further, methods are being developed which will enable the extraction of universal features from the data. In addition, procedures for data handling across experiments are needed, which will allow the transfer of those universal features between different production processes and final states. Theorists have already developed the basic concepts how such universal features can be defined. However, considerable technical challenges have so far prohibited the full implementation of these ideas into the data analysis frameworks of the current generation of experiments. The outstanding challenges and possible angles of attack have been discussed and documented in a series of workshops during the past few years . It is now a consensus in the community that to overcome said challenges, a closer cooperation between phenomenologists and experimentalists is needed. The first and foremost goal of the PHASE network is to facilitate this cooperation. The activities carried out in the project proposed here aim at providing researchers with useful tools for data analysis. They will produce actual software implementations of amplitude models. The focus will be on advanced models that cannot be produced by a single collaboration but need combined expertise from several actors. PHASE puts the software implementation of the physics models into the center of its activities. Its goal is to advance complex analysis projects from the conceptual to the actual.

A future e+e− collider will be capable to show the imprint of composite Higgs scenarios encompassing partial compositeness. Amongst the possible designs of such a machine, a Future Circular Collider of e+e− beams (FCC-ee) has become a frontrunner project in terms of cost effectiveness, precision and search reach . Besides the detailed study of the Higgs boson properties, based upon the analysis of the Bjorken production channel e+e− → ZH at an energy of about 240 GeV, such a machine will have a rich programme also covering top-quark physics (at the energies of 350 to 370 GeV) and revisiting the typical LEP1/SLC and LEP2 energy ranges (from MZ to 2MW) with significantly increased luminosity. Of particular relevance for our purposes is the FCC-ee ability to afford one with a very accurate determination of the top-quark properties, chiefly, its mass, width and couplings to SM objects. This is because the top quark is the natural carrier of New Physics (NP) phenomena associated to the partial compositeness mechanism.

When the measurements from the FCC-ee become available, an improved determination of the standard-model “input” parameters will be needed to fully exploit the new precision data towards either constraining or fitting the parameters of beyond-the-standard-model theories. Among these input parameters is the electromagnetic coupling constant estimated at the Z mass scale, $(m^2_{\rm Z})$. The measurement of the muon forward-backward asymmetry at the FCC-ee, just below and just above the Z pole, can be used to make a direct determination of $(m^2_{\rm Z})$ with an accuracy deemed adequate for an optimal use of the FCC-ee precision data.

INTRODUCTION The design study of the Future Circular Colliders (FCC) in a 100-km ring in the Geneva area has started at CERN at the beginning of 2014, as an option for post-LHC particle accelerators. The study has an emphasis on proton-proton and electron-positron high-energy frontier machines . In the current plans, the first step of the FCC physics programme would exploit a high-luminosity ${\rm e^+e^-}$ collider called FCC-ee, with centre-of-mass energies ranging from below the Z pole to the ${\rm t\bar t}$ threshold and beyond. A first look at the physics case of the FCC-ee can be found in Ref. . In this first look, the focus regarding top-quark physics was on precision measurements of the top-quark mass, width, and Yukawa coupling through a scan of the ${\rm t\bar t}$ production threshold, with $$ comprised between 340 and 350GeV. The expected precision on the top-quark mass was in turn used, together with the outstanding precisions on the Z peak observables and on the W mass, in a global electroweak fit to set constraints on weakly-coupled new physics up to a scale of 100TeV. Although not studied in the first look, measurements of the top-quark electroweak couplings are of interest, as new physics might also show up via significant deviations of these couplings with respect to their standard-model predictions. Theories in which the top quark and the Higgs boson are composite lead to such deviations. The inclusion of a direct measurement of the ttZ coupling in the global electroweak fit is therefore likely to further constrain these theories. It has been claimed that both a centre-of-mass energy well beyond the top-quark pair production threshold and a large longitudinal polarization of the incoming electron and positron beams are crucially needed to independently access the ttγ and the ttZ couplings for both chirality states of the top quark. In Ref. , it is shown that the measurements of the total event rate and the forward-backward asymmetry of the top quark, with 500${\rm fb}^{-1}$ at $=500$GeV and with beam polarizations of ${\cal P} = \pm 0.8$, ${\cal P}^\prime = \mp 0.3$, allow for this distinction. The aforementioned claim is revisited in the present study. The sensitivity to the top-quark electroweak couplings is estimated here with an optimal-observable analysis of the lepton angular and energy distributions of over a million events from ${\rm t\bar t}$ production at the FCC-ee, in the $\ell \nu {\rm q \bar q b \bar b}$ final states (with $\ell = {\rm e}$ or μ), without incoming beam polarization and with a centre-of-mass energy not significantly above the ${\rm t\bar t}$ production threshold. Such a sensitivity can be understood from the fact that the top-quark polarization arising from its coupling to the Z is maximally transferred to the final state particles via the weak top-quark decay ${\rm t \to W b}$ with a 100% branching fraction: the lack of initial polarization is compensated by the presence of substantial final state polarization, and by a larger integrated luminosity. A similar situation was encountered at LEP, where the measurement of the total rate of ${\rm Z} \to \tau^+\tau^-$ events and of the tau polarization was sufficient to determine the tau couplings to the Z, regardless of initial state polarization . This letter is organized as follows. First, the reader is briefly reminded of the theoretical framework. Next, the statistical analysis of the optimal observables is described, and realistic estimates for the top-quark electroweak coupling sensitivities are obtained as a function of the centre-of-mass energy at the FCC-ee. Finally, the results are discussed, and prospects for further improvements are given.

INTRODUCTION The Higgs boson with mass around 125 GeV recently discovered by the ATLAS and CMS experiments  at the LHC is found to have properties compatible with the Standard Model predictions , as shown for example in Fig. [fig:ellis] . Coupled with the absence of any other indication so far for new physics at the LHC, be it either through precision measurements or via direct searches, this fundamental observation seems to push the energy scale of any physics beyond the Standard Model above several hundred GeV. The higher-energy LHC run, which is expected to start in 2015 at $ \sim 13$-14 TeV, will extend the sensitivity to new physics to 1 TeV or more. Fundamental discoveries may therefore be made in this energy range by 2017-2018. Independently of the outcome of this higher-energy run, however, there must be new phenomena, albeit at unknown energy scales, as shown by the evidence for non-baryonic dark matter, the cosmological baryon-antibaryon asymmetry and non-zero neutrino masses, which are all evidence for physics beyond the Standard Model. In addition to the high-luminosity upgrade of the LHC, new particle accelerators will be instrumental to understand the physics underlying these observations.