Software Challenges For HL-LHC Data Analysis

The high energy physics community is discussing where investment is needed to prepare software for the HL-LHC and its unprecedented challenges. The ROOT project is one of the central software players in high energy physics since decades. From its experience and expectations, the ROOT team has distilled a comprehensive set of areas that should see research and development in the context of data analysis software, for making best use of HL-LHC's physics potential. This work shows what these areas could be, why the ROOT team believes investing in them is needed, which gains are expected, and where related work is ongoing. It can serve as an indication for future research proposals and cooperations

ROOT - A C++ Framework for Petabyte Data Storage, Statistical Analysis and Visualization

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

HistFitter software framework for statistical data analysis

We present a software framework for statistical data analysis, called HistFitter, that has been used extensively by the ATLAS Collaboration to analyze big datasets originating from proton-proton collisions at the Large Hadron Collider at CERN. Since 2012 HistFitter has been the standard statistical tool in searches for supersymmetric particles performed by ATLAS. HistFitter is a programmable and flexible framework to build, book-keep, fit, interpret and present results of data models of nearly arbitrary complexity. Starting from an object-oriented configuration, defined by users, the framework builds probability density functions that are automatically fitted to data and interpreted with statistical tests. A key innovation of HistFitter is its design, which is rooted in core analysis strategies of particle physics. The concepts of control, signal and validation regions are woven into its very fabric. These are progressively treated with statistically rigorous built-in methods. Being capable of working with multiple data models at once, HistFitter introduces an additional level of abstraction that allows for easy bookkeeping, manipulation and testing of large collections of signal hypotheses. Finally, HistFitter provides a collection of tools to present results with publication-quality style through a simple command-line interface.Comment: 35 pages (excluding appendix) and 10 figures. Code publicly available at: http://cern.ch/histfitte

Towards Real-World Applications of ServiceX, an Analysis Data Transformation System

One of the biggest challenges in the High-Luminosity LHC (HL- LHC) era will be the significantly increased data size to be recorded and analyzed from the collisions at the ATLAS and CMS experiments. ServiceX is a software R&D project in the area of Data Organization, Management and Access of the IRIS- HEP to investigate new computational models for the HL- LHC era. ServiceX is an experiment-agnostic service to enable on-demand data delivery specifically tailored for nearly-interactive vectorized analyses. It is capable of retrieving data from grid sites, on-the-fly data transformation, and delivering user-selected data in a variety of different formats. New features will be presented that make the service ready for public use. An ongoing effort to integrate ServiceX with a popular statistical analysis framework in ATLAS will be described with an emphasis of a practical implementation of ServiceX into the physics analysis pipeline.Comment: 8 pages, 3 figures, 2 listings, 1 table, submitted to the 25th International Conference on Computing in High Energy & Nuclear Physic

PHYSTAT-LHC Workshop on Statistical Issues for LHC Physics

A PHYSTAT workshop on the topic of Statistical issues for LHC physics was held at CERN. The workshop focused on issues related to discovery that we hope will be relevant to the LHC. These proceedings contain written versions of nearly all the talks, several of which were given by professional statisticians. The talks varied from general overviews, to those describing searches for specific particles. The treatment of background uncertainties figured prominently. Many of the talks describing search strategies for new effects should be of interest not only to particle physicists but also to scientists in other fields

Study of the Higgs boson and the Top quark properties by using the ttH production

RESUMEN: En el presente documento presentamos la media de la sección eficaz de la producción de tt, Higgs del modelo standard, tt+bb y el proceso recientemente observado ttH usando datos tomados de colisiones pp a sqrt(s) = 13TeV en 2017 por el detector CMS del LHC. Eventos con un único leptón (e o µ) y al menos dos jets son seleccionados. Regiones de señal para todos los procesos son definidas con base al numero de jets y b jets. Las medidas, que se han hecho con dos métodos distintos, son comparadas con las predicciones del modelo standard, encontrando que son compatibles entre ellos.ABSTRACT: The cross sections for the production of tt pairs, standard model Higgs boson, tt+bb, and the recently observed ttH process are measured using data collected in pp collisions at sqrt(s) = 13 TeV in 2017 by the CMS experiment at the LHC. Events with one lepton (e or µ) and at least two reconstructed jets in the final state are selected. Signal regions for all the signatures are defined based on the number of jets and b jets. The measurements, performed with two different approaches, are compared with the standard model expectations and they are found to be compatible.Máster en Física de Partículas y del Cosmo

Study of beauty baryons decaying to D0pK and the amplitudes of Λb0→D0pK in the Dalitz plane with the LHCb experiment

The study of the decays Λb0 / Ξb0→D0pK is presented using data of the LHCb experiment. Both decays can be used to measure charge parity (CP) violation. The measured CP asymmetries are in agreement with zero. The decays branching fractions are determined to B(Λb0→D0pK) = (4.61 ± 0.17stat ± 0.08syst ± 0.52ext) × 10-5 and fΞ⋅B(Ξb0→D0pK) = (2.18 ± 0.08stat ± 0.05syst ± 0.39ext) × 10-6, being one and a half times precise than the current best measurements. An amplitude analysis of the Λb0→D0pK phase space with D0→K-π+ yields a large fraction of a Λc+(2950) resonance and multiple Λ* resonances