J. Linacre

The goal for CMS computing is to maximise the throughput of simulated event generation while also processing event data generated by the detector as quickly and reliably as possible. To maintain this achievement as the quantity of events increases CMS computing has migrated at the Tier 1 level from its old production framework, ProdAgent, to a new one, WMAgent. The WMAgent framework offers improved processing efficiency and increased resource usage as well as a reduction in operational manpower.

During the first run, CMS collected and processed more than 10B data events and simulated more than 15B events. Up to 100k processor cores were used simultaneously and 100PB of storage was managed. Each month petabytes of data were moved and hundreds of users accessed data samples. In this document we discuss the operational experience from this first run. We present the workflows and data flows that were executed, and we discuss the tools and services developed, and the operations and shift models used to sustain the system. Many techniques were followed from the original computing planning, but some were reactions to difficulties and opportunities. We also address the lessons learned from an operational perspective, and how this is shaping our thoughts for 2015.

A measurement of the mass of the top quark is presented, using top-antitop pair (t$\bar{t}$) candidate events for the lepton+jets decay channel. The measurement makes use of Tevatron p$\bar{p}$ collision data at centre-of-mass energy √s = 1.96 TeV, collected at the CDF detector. The top quark mass is measured by employing an unbinned maximum likelihood method where the event probability density functions are calculated using signal (t$\bar{t}$) and background (W+jets) matrix elements, as well as a set of parameterised jet-to-parton mapping functions. The likelihood function is maximised with respect to the top quark mass, the fraction of signal events, and a correction to the jet energy scale (JES) of the calorimeter jets. The simultaneous measurement of the JES correction (ΔJES) provides an in situ jet energy calibration based on the known mass of the hadronically decaying W boson. Using 578 lepton+jets candidate events corresponding to 3.2 fb -1 of integrated luminosity, the top quark mass is measured to be mt = 172.4± 1.4 (stat+ΔJES) ±1.3 (syst) GeV=c2, one of the most precise single measurements to date.

Binned data frames are a generalisation of multi-dimensional histograms, represented in a tabular format with one category per row containing the labels, bin contents, uncertainties and so on. Pandas is an industry-standard tool, which provides a data frame implementation complete with routines for data frame manipultion, persistency, visualisation, and easy access to “big data” scientific libraries and machine learning tools. FAST (the Faster Analysis Software Taskforce) has developed a generic approach for typical binned HEP analyses, driving the summary of ROOT Trees to multiple binned DataFrames with a yaml-based analysis description. Using Continuous Integration to run subsets of the analysis, we can monitor and test changes to the analysis itself, and deploy documentation automatically. This report describes this approach using examples from a public CMS tutorial and details the benefit over traditional methods.

Measurements of polarisation and spin correlations are presented in events with top quarks produced in pp collisions at the LHC. The data correspond to integrated luminosities of $$5 fb^{-1}$$ at $$\sqrt{s}$$ = 7 TeV and 20 $$fb^{-1}$$ at $$\sqrt{s}$$ = 8 TeV collected with the ATLAS and CMS detectors. The top quark polarization is measured in both single top quark production in the t-channel and $$t\bar{t}$$ pair-production, from the angular distributions of charged leptons in the rest frame of their parent top quark. The spin correlations are measured in $$t\bar{t}$$ events using various angular distributions of the decay products. The measurements are made using both template fitting methods and by unfolding the distributions to the parton-level, where differential measurements with respect to the invariant mass, rapidity, and transverse momentum of the $$t\bar{t}$$ system are also made. The spin correlation measurements are used to search for new physics in the form of a light top squark or an anomalous top quark chromo-magnetic dipole moment. All measurements are found to be in agreement with predictions of the standard model.

Measurements of polarisation and spin correlations are presented in events with top quarks produced in pp collisions at the LHC. The data correspond to integrated luminosities of 5 fb 1 at p s = 7 TeV and 20 fb 1 at p s = 8 TeV collected with the ATLAS and CMS detectors. The top quark polarisation is measured in both single top quark production in the t-channel and t t pair-production, from the angular distributions of charged leptons in the rest frame of their parent top quark. The spin correlations are measured in t t events using various angular distributions of the decay products. The measurements are made using both template fitting methods and by unfolding the distributions to the parton-level, where differential measurements with respect to the invariant mass, rapidity, and transverse momentum of the t t system are also made. The spin correlation measurements are used to search for new physics in the form of a light top squark or an anomalous top quark chromo-magnetic dipole moment. All measurements are found to be in agreement with predictions of the standard model.

We report the results of the measurements of the top quark mass using top pair events corresponding to an integrated luminosity of more than 4 fb -1 from proton-antiproton collisions at the Tevatron, recorded by the CDF II detector.We present different results using various techniques in the lepton+jets, dilepton, and all-jets channels, and describe the current status of the systematic uncertainties.We present also a combination by the TevEWWG (Tevatron electroweak working group) of the best top mass results from CDF and DØ in Run 1 and Run 2 of the Tevatron.This result is the current world average, and offers an uncertainty almost reaching 1 GeV/c 2 .The new mass value has been included in traditional LEP EWWG fits to precision electroweak data, and implications for the Standard Model Higgs have been derived.

Measurements of $\mathrm{t\bar{t}}$ spin correlations are presented in events with top quarks produced in $\mathrm{pp}$ collisions at the LHC. The data correspond to an integrated luminosity of $36\:\mathrm{fb^{-1}}$ at $\sqrt{s}=13\:\mathrm{TeV}$ collected at both the ATLAS and CMS detectors. The spin correlations are measured using the angular distributions of the leptons in dilepton channel $\mathrm{t\bar{t}}$ events. The spin correlations are probed both directly, using distributions measured in the top quark rest frames that depend only on the top quark spin, and indirectly, using distributions measured in the laboratory frame. The distributions are unfolded to the parton level and extrapolated to the full phase space. Some of the laboratory frame distributions are additionally unfolded to the particle level in the fiducial phase space of the ATLAS detector. The spin correlation measurements are used to search for new physics in the form of a light top squark or an anomalous top quark chromo-magnetic dipole moment, and stringent constraints are placed in both cases.

The Faster Analysis Software Taskforce (FAST) is a small, European group of HEP researchers that have been investigating and developing modern software approaches to improve HEP analyses. We present here an overview of the key product of this effort: a set of packages that allows a complete implementation of an analysis using almost exclusively YAML files. Serving as an analysis description language (ADL), this toolset builds on top of the evolving technologies from the Scikit-HEP and IRIS-HEP projects as well as industry-standard libraries such as Pandas and Matplotlib. Data processing starts with event-level data (the trees) and can proceed by adding variables, selecting events, performing complex user-defined operations and binning data, as defined in the YAML description. The resulting outputs (the tables) are stored as Pandas dataframes which can be programmatically manipulated and converted to plots or inputs for fitting frameworks. No longer just a proof-of-principle, these tools are now being used in CMS analyses, the LUX-ZEPLIN experiment, and by students on several other experiments. In this talk we will showcase these tools through examples, highlighting how they address the different experiments’ needs, and compare them to other similar approaches.

Measurements of $\mathrm{t\bar{t}}$ spin correlations are presented in events with top quarks produced in $\mathrm{pp}$ collisions at the LHC. The data correspond to an integrated luminosity of $36\:\mathrm{fb^{-1}}$ at $\sqrt{s}=13\:\mathrm{TeV}$ collected at both the ATLAS and CMS detectors. The spin correlations are measured using the angular distributions of the leptons in dilepton channel $\mathrm{t\bar{t}}$ events. The spin correlations are probed both directly, using distributions measured in the top quark rest frames that depend only on the top quark spin, and indirectly, using distributions measured in the laboratory frame. The distributions are unfolded to the parton level and extrapolated to the full phase space. Some of the laboratory frame distributions are additionally unfolded to the particle level in the fiducial phase space of the ATLAS detector. The spin correlation measurements are used to search for new physics in the form of a light top squark or an anomalous top quark chromo-magnetic dipole moment, and stringent constraints are placed in both cases.