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In the last two years the CMS experiment has commissioned a full end to end data quality monitoring system in tandem with progress in the detector commissioning. We present the data quality monitoring and certification systems in place, from online data taking to delivering certified data sets for physics analyses, release validation and offline re-reconstruction activities at Tier-1s. We discuss the main results and lessons learnt so far in the commissioning and early detector operation. We outline our practical operations arrangements and the key technical implementation aspects.

A Consortium between four LHC Computing Centers (Bari, Milano, Pisa and Trieste) has been formed in 2010 to prototype Analysis-oriented facilities for CMS data analysis, profiting from a grant from the Italian Ministry of Research. The Consortium aims to realize an ad-hoc infrastructure to ease the analysis activities on the huge data set collected at the LHC Collider. While “Tier2” Computing Centres, specialized in organized processing tasks like Monte Carlo simulation, are nowadays a well established concept, with years of running experience, site specialized towards end user chaotic analysis activities do not yet have a defacto standard implementation. In our effort, we focus on all the aspects that can make the analysis tasks easier for a physics user not expert in computing. On the storage side, we are experimenting on storage techniques allowing for remote data access and on storage optimization on the typical analysis access patterns. On the networking side, we are studying the differences between flat and tiered LAN architecture, also using virtual partitioning of the same physical networking for the different use patterns. Finally, on the user side, we are developing tools and instruments to allow for an exhaustive monitoring of their processes at the site, and for an efficient support system in case of problems. We will report about the results of the test executed on different subsystem and give a description of the layout of the infrastructure in place at the site participating to the consortium.

In 2012, 14 Italian institutions participating in LHC Experiments won a grant from the Italian Ministry of Research (MIUR), with the aim of optimising analysis activities, and in general the Tier2 Tier3 infrastructure. We report on the activities being researched upon, on the considerable improvement in the ease of access to resources by physicists, also those with no specific computing interests. We focused on items like distributed storage federations, access to batch-like facilities, provisioning of user interfaces on demand and cloud systems. R&D on next-generation databases, distributed analysis interfaces, and new computing architectures was also carried on. The project, ending in the first months of 2016, will produce a white paper with recommendations on best practices for data-analysis support by computing centers.

The Italian community in CMS has built a geographically distributed network in which all the data stored in the Italian region are available to all the users for their everyday work. This activity involves at different level all the CMS centers: the Tier1 at CNAF, all the four Tier2s (Bari, Rome, Legnaro and Pisa), and few Tier3s (Trieste, Perugia, Torino, Catania, Napoli, ...). The federation uses the new network connections as provided by GARR, our NREN (National Research and Education Network), which provides a minimum of 10 Gbit/s to all the sites via the GARR-X[2] project. The federation is currently based on Xrootd[1] technology, and on a Redirector aimed to seamlessly connect all the sites, giving the logical view of a single entity. A special configuration has been put in place for the Tier1, CNAF, where ad-hoc Xrootd changes have been implemented in order to protect the tape system from excessive stress, by not allowing WAN connections to access tape only files, on a file-by-file basis. In order to improve the overall performance while reading files, both in terms of bandwidth and latency, a hierarchy of xrootd redirectors has been implemented. The solution implemented provides a dedicated Redirector where all the INFN sites are registered, without considering their status (T1, T2, or T3 sites). An interesting use case were able to cover via the federation are disk-less Tier3s. The caching solution allows to operate a local storage with minimal human intervention: transfers are automatically done on a single file basis, and the cache is maintained operational by automatic removal of old files.

In 2012, 14 Italian Institutions participating LHC Experiments (10 in CMS) have won a grant from the Italian Ministry of Research (MIUR), to optimize Analysis activities and in general the Tier2/Tier3 infrastructure. A large range of activities is actively carried on: they cover data distribution over WAN, dynamic provisioning for both scheduled and interactive processing, design and development of tools for distributed data analysis, and tests on the porting of CMS software stack to new highly performing / low power architectures.

We derive model-independent constraints on four-fermion contact interaction-type dynamics from the published preliminary LEP2 experimental data on e+e- annihilation into \\(\\mu^+\\mu^-\\) and \\(\\tau^+\\tau^-\\) pairs, measured at different energies between 130 and 207 GeV. The basic observables are chosen to be the total cross section and the forward-backward asymmetry, and the analysis realistically takes into account data uncertainties and correlations among measurements at the various energies. The combination of data from different energy points plays an important role in the determination of regions allowed for the contact interaction coupling constants. In contrast to the more common one-parameter analyses, we only obtain constraints on pairs of parameters rather than limits on individual ones.

A search for exotic decays of the Higgs boson ($$\\text {H}$$H ) with a mass of 125$$\\,\\text {Ge}\\hspace{-.08em}\\text {V}$$Ge V to a pair of light pseudoscalars$$\\text {a}_{1} $$a 1 is performed in final states where one pseudoscalar decays to two$${\\textrm{b}}$$b quarks and the other to a pair of muons or$$\\tau $$τ leptons. A data sample of proton–proton collisions at$$\\sqrt{s}=13\\,\\text {Te}\\hspace{-.08em}\\text {V} $$s = 13 Te V corresponding to an integrated luminosity of 138$$\\,\\text {fb}^{-1}$$fb - 1 recorded with the CMS detector is analyzed. No statistically significant excess is observed over the standard model backgrounds. Upper limits are set at 95% confidence level ($$\\text {CL}$$CL ) on the Higgs boson branching fraction to$$\\upmu \\upmu \\text{ b } \\text{ b } $$μ μ b b and to$$\\uptau \\uptau \\text{ b } \\text{ b },$$τ τ b b , via a pair of$$\\text {a}_{1} $$a 1 s. The limits depend on the pseudoscalar mass$$m_{\\text {a}_{1}}$$m a 1 and are observed to be in the range (0.17–3.3) $$\\times 10^{-4}$$× 10 - 4 and (1.7–7.7) $$\\times 10^{-2}$$× 10 - 2 in the$$\\upmu \\upmu \\text{ b } \\text{ b } $$μ μ b b and$$\\uptau \\uptau \\text{ b } \\text{ b } $$τ τ b b final states, respectively. In the framework of models with two Higgs doublets and a complex scalar singlet (2HDM+S), the results of the two final states are combined to determine upper limits on the branching fraction$${\\mathcal {B}}(\\text {H} \\rightarrow \\text {a}_{1} \\text {a}_{1} \\rightarrow \\ell \\ell \\text{ b } \\text{ b})$$B ( H → a 1 a 1 → ℓ ℓ b b ) at 95%$$\\text {CL}$$CL , with$$\\ell $$ℓ being a muon or a$$\\uptau $$τ lepton. For different types of 2HDM+S, upper bounds on the branching fraction$${\\mathcal {B}}(\\text {H} \\rightarrow \\text {a}_{1} \\text {a}_{1} )$$B ( H → a 1 a 1 ) are extracted from the combination of the two channels. In most of the Type II 2HDM+S parameter space,$${\\mathcal {B}}(\\text {H} \\rightarrow \\text {a}_{1} \\text {a}_{1} )$$B ( H → a 1 a 1 ) values above 0.23 are excluded at 95%$$\\text {CL}$$CL for$$m_{\\text {a}_{1}}$$m a 1 values between 15 and 60$$\\,\\text {Ge}\\hspace{-.08em}\\text {V}$$Ge V .

The dependence of inclusive jet production in proton-proton collisions with a center-of-mass energy of 13 TeV on the distance parameter R of the anti- k T algorithm is studied using data corresponding to integrated luminosities up to 35.9 fb − 1 collected by the CMS experiment in 2016. The ratios of the inclusive cross sections as functions of transverse momentum p T and rapidity y , for R in the range 0.1 to 1.2 to those using R = 0 . 4 are presented in the region 84 < p T < 1588 GeV and | y | < 2 . 0. The results are compared to calculations at leading and next-to-leading order in the strong coupling constant using different parton shower models. The variation of the ratio of cross sections with R is well described by calculations including a parton shower model, but not by a leading-order quantum chromodynamics calculation including nonperturbative effects. The agreement between the data and the theoretical predictions for the ratios of cross sections is significantly improved when next-to-leading order calculations with nonperturbative effects are used.

A data sample of events from proton-proton collisions with at least two jets, and two isolated same-sign or three or more charged leptons, is studied in a search for signatures of new physics phenomena. The data correspond to an integrated luminosity of 137 \\text fb⁻¹ 137fb-1 at a center-of-mass energy of 13 \\text TeV 13TeV, collected in 2016–2018 by the CMS experiment at the LHC. The search is performed using a total of 168 signal regions defined using several kinematic variables. The properties of the events are found to be consistent with the expectations from standard model processes. Exclusion limits at 95% confidence level are set on cross sections for the pair production of gluinos or squarks for various decay scenarios in the context of supersymmetric models conserving or violating R parity. The observed lower mass limits are as large as 2.1 \\text TeV 2.1TeV for gluinos and 0.9 \\text TeV 0.9TeV for top and bottom squarks. To facilitate reinterpretations, model-independent limits are provided in a set of simplified signal regions.