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A performant and easy-to-use event data model (EDM) is a key component of any HEP software stack. The podio EDM toolkit provides a user friendly way of generating such a performant implementation in C++ from a high level description in yaml format. Finalizing a few important developments, we are in the final stretches for release v1.0 of podio, a stable release with backward compatibility for datafiles written with podio from then on. We present an overview of the podio basics, and go into slighty more technical detail on the most important topics and developments. These include: schema evolution for generated EDMs, multithreading with podio generated EDMs, the implementation of them as well as the basics of I/O. Using EDM4hep, the common and shared EDM of the Key4hep project, we highlight a few of the smaller features in action as well as some lessons learned during the development of EDM4hep and podio. Finally, we show how podio has been integrated into the Gaudi based event processing framework that is used by Key4hep, before we conclude with a brief outlook on potential developments after v1.0., Comment: Submitted to proceedings of CHEP 2023

The podio event data model (EDM) toolkit provides an easy way to generate a performant implementation of an EDM from a high level description in yaml format. We present the most recent developments in podio, most importantly the inclusion of a schema evolution mechanism for generated EDMs as well as the "Frame", a thread safe, generalized event data container. For the former we discuss some of the technical aspects in relation with supporting different I/O backends and leveraging potentially existing schema evolution mechanisms provided by them. Regarding the Frame we introduce the basic concept and highlight some of the functionality as well as important aspects of its implementation. The usage of podio for generating different EDMs for future collider projects (most importantly EDM4hep, the common EDM for the Key4hep project) has inspired new features. We present some of those smaller new features and end with a brief overview on current developments towards a first stable version as well as an outlook on future developments beyond that., Comment: Submitted to proceedings of ACAT 2022

The Key4hep project aims to provide a turnkey software solution for the full experiment lifecycle, based on established community tools. Several future collider communities (CEPC, CLIC, EIC, FCC, and ILC) have joined to develop and adapt their workflows to use the common data model EDM4hep and common framework. Besides sharing of existing experiment workflows, one focus of the Key4hep project is the development and integration of new experiment independent software libraries. Ongoing collaborations with projects such as ACTS, CLUE, PandoraPFA and the OpenDataDector show the potential of Key4hep as an experiment-independent testbed and development platform. In this talk, we present the challenges of an experiment-independent framework along with the lessons learned from discussions of interested communities (such as LUXE) and recent adopters of Key4hep in order to discuss how Key4hep could be of interest to the wider HEP community while staying true to its goal of supporting future collider designs studies., Comment: Submitted to proceedings of ACAT 2022

Detector studies for future experiments rely on advanced software tools to estimate performance and optimize their design and technology choices. The Key4hep project provides a flexible turnkey solution for the full experiment life-cycle based on established community tools such as ROOT, Geant4, DD4hep, Gaudi, podio and spack. Members of the CEPC, CLIC, EIC, FCC, and ILC communities have joined to develop this framework and have merged, or are in the progress of merging, their respective software environments into the Key4hep stack. These proceedings will give an overview over the recent progress in the Key4hep project: covering the developments towards adaptation of state-of-the-art tools for simulation (DD4hep, Gaussino), track and calorimeter reconstruction (ACTS, CLUE), particle flow (PandoraPFA), analysis via RDataFrame, and visualization with Phoenix, as well as tools for testing and validation., Comment: Proceedings of CHEP 2023

The international Future Circular Collider (FCC) study aims at designing pp, e$^+$e$^-$, e$^\pm$p colliders to be built in a new 100 km tunnel in the Geneva region. The electroweak, Higgs and top factory (FCC-ee) is designed to provide collisions at a centre of mass energy range between 90 (Z-pole) and 365 GeV ($\mathrm{t\bar{t}}$) and unprecedented integrated luminosities, producing huge amounts of data which will pose significant challenges to data processing. In this essay we discuss the needs in terms of storage and CPU for the diverse phases of the project, and the possible solutions mostly based on the models developed for HL-LHC., Comment: 8 pages, no figures, Submitted to EPJ+ special issue: A future Higgs and Electroweak factory (FCC): Challenges towards discovery, Focus on FCC-ee

The road map to the FCC Feasibility Study Report, for submission to the next Update of the European Strategy for Particle Physics, will require detailed simulation and advanced reconstruction algorithms to explore and maximise the physics reach of proposed detector solutions. The optimisation process will require maximal flexibility in changing detector geometries, materials and sensitive areas, and efficient tools to quantify the overall performance. To synergise such developments the CEPC, CLIC, FCC, ILC and SCT communities have engaged in the commissioning of a `Turnkey Software Stack' (Key4hep), which would provide all the necessary ingredients, from simulation to analysis, for future experiments. This approach is based on the positive experience of the linear collider projects ILC and CLIC, which have developed and used a common software stack (iLCSoft) over the last decade. Key4hep aims to cover most, if not all, future linear and circular machines colliding leptons (electrons, muons), and hadrons. The common software ecosystem will facilitate writing specific components for experiments ensuring coherency and maximising the re-use of established solutions. Project-specific software frameworks will require adaptation to fully profit from the common software base. In this essay we present the status and plans for re-framing the FCC software framework, FCCSW, around Key4hep and discuss the challenges associated with the transition., Comment: 6 pages, no figures, Submitted to EPJ+ special issue: A future Higgs and Electroweak factory (FCC): Challenges towards discovery, Focus on FCC-ee

Powerful flexible computer codes are essential for the design and optimisation of accelerator and experiments. We briefly review what already exists and what is needed in terms of accelerator codes. For the FCC-ee it will be important to include the effects of beamstrahlung and beam-beam interaction as well as machine imperfections and sources of beam induced backgrounds relevant for the experiments and consider the possibility of beam-polarisation. The experiment software Key4hep, which aims to provide a common software stack for future experiments, is described and the possibility of extending this concept to machine codes is discussed. We analyse how to interface and connect the accelerator and experiment codes in an efficient and flexible way for optimisation of the FCC-ee interaction region design, and discuss the possibility of using shared data formats as an interface., Comment: 8 pages, 2 figures, Submitted to EPJ+ special issue: A future Higgs and Electroweak factory (FCC): Challenges towards discovery, Focus on FCC-ee

This document answers in simple terms many FAQs about FCC-ee, including comparisons with other colliders. It complements the FCC-ee CDR and the FCC Physics CDR by addressing many questions from non-experts and clarifying issues raised during the European Strategy symposium in Granada, with a view to informing discussions in the period between now and the final endorsement by the CERN Council in 2020 of the European Strategy Group recommendations. This document will be regularly updated as more questions appear or new information becomes available., Comment: Contribution to the European Particle Physics Strategy Update 2018-2020. Forty-five pages, six figures

Particle physics has an ambitious and broad experimental programme for the coming decades. This programme requires large investments in detector hardware, either to build new facilities and experiments, or to upgrade existing ones. Similarly, it requires commensurate investment in the R&D of software to acquire, manage, process, and analyse the shear amounts of data to be recorded. In planning for the HL-LHC in particular, it is critical that all of the collaborating stakeholders agree on the software goals and priorities, and that the efforts complement each other. In this spirit, this white paper describes the R&D activities required to prepare for this software upgrade.

Data from High Energy Physics (HEP) experiments are collected with significant financial and human effort and are mostly unique. An inter-experimental study group on HEP data preservation and long-term analysis was convened as a panel of the International Committee for Future Accelerators (ICFA). The group was formed by large collider-based experiments and investigated the technical and organizational aspects of HEP data preservation. An intermediate report was released in November 2009 addressing the general issues of data preservation in HEP and an extended blueprint paper was published in 2012. In July 2014 the DPHEP collaboration was formed as a result of the signature of the Collaboration Agreement by seven large funding agencies (others have since joined or are in the process of acquisition) and in June 2015 the first DPHEP Collaboration Workshop and Collaboration Board meeting took place. This status report of the DPHEP collaboration details the progress during the period from 2013 to 2015 inclusive., Comment: report, 60 pages

ROOT is an object-oriented C++ framework conceived in the high-energy physics (HEP) community, designed for storing and analyzing petabytes of data in an efficient way. Any instance of a C++ class can be stored into a ROOT file in a machine-independent compressed binary format. In ROOT the TTree object container is optimized for statistical data analysis over very large data sets by using vertical data storage techniques. These containers can span a large number of files on local disks, the web, or a number of different shared file systems. In order to analyze this data, the user can chose out of a wide set of mathematical and statistical functions, including linear algebra classes, numerical algorithms such as integration and minimization, and various methods for performing regression analysis (fitting). In particular, ROOT offers packages for complex data modeling and fitting, as well as multivariate classification based on machine learning techniques. A central piece in these analysis tools are the histogram classes which provide binning of one- and multi-dimensional data. Results can be saved in high-quality graphical formats like Postscript and PDF or in bitmap formats like JPG or GIF. The result can also be stored into ROOT macros that allow a full recreation and rework of the graphics. Users typically create their analysis macros step by step, making use of the interactive C++ interpreter CINT, while running over small data samples. Once the development is finished, they can run these macros at full compiled speed over large data sets, using on-the-fly compilation, or by creating a stand-alone batch program. Finally, if processing farms are available, the user can reduce the execution time of intrinsically parallel tasks - e.g. data mining in HEP - by using PROOF, which will take care of optimally distributing the work over the available resources in a transparent way.

Scientific results in high-energy physics and in many other fields often rely on complex software stacks. In order to support reproducibility and scrutiny of the results, it is good practice to use open source software and to cite software packages and versions. With ever-growing complexity of scientific software on one side and with IT life-cycles of only a few years on the other side, however, it turns out that despite source code availability the setup and the validation of a minimal usable analysis environment can easily become prohibitively expensive. We argue that there is a substantial gap between merely having access to versioned source code and the ability to create a data analysis runtime environment. In order to preserve all the different variants of the data analysis runtime environment, we developed a snapshotting file system optimized for software distribution. We report on our experience in preserving the analysis environment for high-energy physics such as the software landscape used to discover the Higgs boson at the Large Hadron Collider.

PROOF, the Parallel ROOT Facility, is a ROOT-based framework which enables interactive parallelism for event-based tasks on a cluster of computing nodes. Although PROOF can be used simply from within a ROOT session with no additional requirements, deploying and configuring a PROOF cluster used to be not as straightforward. Recently great efforts have been spent to make the provisioning of generic PROOF analysis facilities with zero configuration, with the added advantages of positively affecting both stability and scalability, making the deployment operations feasible even for the end user. Since a growing amount of large-scale computing resources are nowadays made available by Cloud providers in a virtualized form, we have developed the Virtual PROOF-based Analysis Facility: a cluster appliance combining the solid CernVM ecosystem and PoD (PROOF on Demand), ready to be deployed on the Cloud and leveraging some peculiar Cloud features such as elasticity. We will show how this approach is effective both for sysadmins, who will have little or no configuration to do to run it on their Clouds, and for the end users, who are ultimately in full control of their PROOF cluster and can even easily restart it by themselves in the unfortunate event of a major failure. We will also show how elasticity leads to a more optimal and uniform usage of Cloud resources., Comment: Talk from Computing in High Energy and Nuclear Physics 2013 (CHEP2013), Amsterdam (NL), October 2013, 7 pages, 4 figures

We present recent results of an extensive aging test, performed at the CERN Gamma Irradiation Facility on two single--gap RPC prototypes, developed for the LHCb Muon System. With a method based on a model describing the behaviour of an RPC under high particle flux conditions, we have periodically measured the electrode resistance R of the two RPC prototypes over three years: we observe a large spontaneous increase of R with time, from the initial value of about 2 MOhm to more than 250 MOhm. A corresponding degradation of the RPC rate capabilities, from more than 3 kHz/cm2 to less than 0.15 kHz/cm2 is also found., Comment: 6 pages, 7 figures, presented at Siena 2002, 8th Topical Seminar on Innovative Particle and Radiation Detectors 21-24 October 2002, Siena, Italy

Recent results of an aging test performed at the CERN Gamma Irradiation Facility on a single--gap RPC prototype developed for the LHCb Muon System are presented. The results are based on an accumulated charge of about 0.45 C/cm$^2$, corresponding to about 4 years of LHCb running at the highest background rate. The performance of the chamber has been studied under several photon flux values exploiting a muon beam. A degradation of the rate capability above 1 kHz/cm$^2$ is observed, which can be correlated to a sizeable increase of resistivity of the chamber plates. An increase of the chamber dark current is also observed. The chamber performance is found to fulfill the LHCb operation requirements., Comment: 6 pages, 9 figures, presented at the International Workshop on Aging Phenomena in Gaseous Detectors'', DESY-Hamburg (Germany), October 2001

The preliminary results of an aging test performed at the CERN Gamma Irradiation Facility on a single--gap RPC prototype developed for the LHCb Muon System are presented. The results are based on an accumulated charge density of 0.42 C/cm^2, corresponding to about 4 years of LHCb running at the highest background rate. We observe a rise in the dark current and noise measured with source off. The current drawn with source on steadily decreased, possibly indicating an increase of resistivity of the chamber plates. The performance of the chamber, studied with a muon beam under several photon flux values, is found to still fulfill the LHCb operation requirements., Comment: 4 pages, 6 figures, presented at RPC2001, VIth Workshop on Resistive Plate Chambers and Related Detectors, November 26-27 2001, Coimbra, Portugal

Extensive searches for new phenomena have been performed at LEP. The principal aspects and results of those not related to Higgs bosons are reviewed here., Comment: 4 pages, 4 figures, presented at "XXXVIIth Rencontres de Moriond on QCD and High Energy Hadronic Interactions", Les Arcs, France, 16-23 March 2002

The negative outcome of searches for supersymmetry performed at LEP have been used to derive indirect constraints on the parameters of the most plausible models for cold dark matter based on supersymmetric extensions of the Standard Model. The main results are summarized., Comment: 3 pages, 1 figure, to be published in the proceedings of the XIII Italian meeting on Physics at LEP, LEPTRE, Rome, April 2001

The negative outcome of searches for supersymmetry performed at LEP have been used to derive indirect constraints on the parameters of the most plausible supersymmetric candidates for cold dark matter, in particular for the lightest neutralino. We review the basic ideas leading to the present lower limit on the lightest neutralino mass of about 37 GeV, with emphasis on the underlying assumptions., Comment: 12 pages, 8 figures, to appear in the proceedings of Vulcano Workshop 2000: Frontier Objects In Astrophysics And Particle Physics, 22-27 May 2000, Vulcano, Italy

We analyze the accelerator constraints on the parameter space of the Minimal Supersymmetric extension of the Standard Model, comparing those now available from LEP II and anticipating the likely sensitivity of Tevatron Run II. The most important limits are those from searches for charginos, neutralinos and Higgs bosons at LEP, and searches for stop squarks, charginos and neutralinos at the Tevatron Collider. We also incorporate the constraints derived from b --> s + gamma decay, and discuss the relevance of charge- and colour-breaking minima in the effective potential. We combine and compare the different constraints on the Higgs-mixing parameter mu, the gaugino-mass parameter m_{1/2} and the scalar-mass parameter m0, incorporating radiative corrections to the physical particle masses. We focus on the resulting limitations on supersymmetric dark matter, assumed to be the lightest neutralino, incorporating coannihilation effects in the calculation of the relic abundance. We find that m_chi > 51 GeV and tan(beta) > 2.2 if all soft supersymmetry-breaking scalar masses are universal, including those of the Higgs bosons, and that these limits weaken to m_chi > 46 GeV and tan(beta) > 1.9 if non-universal scalar masses are allowed. Light neutralino dark matter cannot be primarily Higgsino in composition., Comment: 39 pages in LaTeX, including 44 encapsulated postscript figures

We suggest that supersymmetric dark matter be used to set the energy scale of a linear $e^+ e^-$ collider. Assuming that the lightest supersymmetric particle (LSP) is a stable neutralino $\chi$, as in many incarnations of the MSSM with conserved R parity, previous calculations that include coannihilation effects have delineated the region of the $(m_{1/2}, m_0)$ plane where the LSP cosmological relic density lies in the preferred range $0.1 \la \Omega_{\chi} h^2 \la 0.3$. We evaluate here the total cross section for $e^+ e^- \to$ visible pairs of supersymmetric particles, for different values of $m_{1/2}$ and $m_0$, and investigate how much of the dark matter region can be explored by $e^+ e^-$ colliders with different centre-of-mass energies $E_{CM}$. We find that a collider with $E_{CM} = 500$ GeV or 1 TeV can only explore part of the cosmological region, and that a collider with $E_{CM} = 1.5$ TeV with sufficient luminosity can explore all of the supersymmetric dark matter region., Comment: 14 pages, latex, 4 eps figures

Searches for supersymmetry at LEP allowing for R-parity violation are reviewed. The results are compared with the R-parity conserving scenarios., Comment: 8 pages, 8 figures, to be included in the proceedings of the 29th "International Conference on High Energy Physics", Vancouver, 1998

We analyze the LEP constraints from searches for charginos $\chi^{\pm}$ and neutralinos $\chi_i$, taking into account radiative corrections to the relations between their masses and the underlying Higgs-mixing and gaugino-mass parameters $\mu, m_{1/2}$ and the trilinear mass parameter $A_t$. Whilst radiative corrections do not alter the excluded domain in $m_{\chi^{\pm}}$ as a function of $m_{\chi^{\pm}} - m_{\chi}$, its mapping into the $\mu, m_{1/2}$ plane is altered. We update our previous lower limits on the mass of gaugino dark matter and on tan$\beta$, the ratio of Higgs vacuum expectation values, in the light of the latest LEP data and these radiative corrections. We also discuss the viability of Higgsino dark matter, incorporating co-annihilation effects into the calculation of the Higgsino relic abundance. We find that Higgsino dark matter is viable for only a very limited range of $\mu$ and $m_{1/2}$, which will be explored completely by upcoming LEP runs., Comment: Version to appear in Phys. Rev. D., 21 pages in LateX, including 10 encapsulated postscript figures; uses epsf.sty.; Figures modified (one deleted), conclusions unchanged