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Person# Stefan Simion

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Related publications (4)

Related research domains (3)

Measurement

Measurement is the quantification of attributes of an object or event, which can be used to compare with other objects or events. In other words, measurement is a process of determining how large or small a physical quantity is as compared to a basic reference quantity of the same kind. The scope and application of measurement are dependent on the context and discipline. In natural sciences and engineering, measurements do not apply to nominal properties of objects or events, which is consistent with the guidelines of the International vocabulary of metrology published by the International Bureau of Weights and Measures.

Higgs boson

The Higgs boson, sometimes called the Higgs particle, is an elementary particle in the Standard Model of particle physics produced by the quantum excitation of the Higgs field, one of the fields in particle physics theory. In the Standard Model, the Higgs particle is a massive scalar boson with zero spin, even (positive) parity, no electric charge, and no colour charge that couples to (interacts with) mass. It is also very unstable, decaying into other particles almost immediately upon generation.

Standard Model

The Standard Model of particle physics is the theory describing three of the four known fundamental forces (electromagnetic, weak and strong interactions – excluding gravity) in the universe and classifying all known elementary particles. It was developed in stages throughout the latter half of the 20th century, through the work of many scientists worldwide, with the current formulation being finalized in the mid-1970s upon experimental confirmation of the existence of quarks.

Jian Wang, Matthias Finger, Lesya Shchutska, Qian Wang, Yiming Li, Matthias Wolf, Varun Sharma, Konstantin Androsov, Jan Steggemann, Leonardo Cristella, Roberto Castello, Alessandro Degano, Xin Chen, James Henderson, Sofia Vallecorsa, Lulu Liu, Yi Jiang, Clement Helsens, Christophe Clément, Snezana Nektarijevic, Valerio Rossetti, Mingkui Wang, Zhirui Xu, Chao Wang, João Miguel das Neves Duarte, Lei Zhang, Tian Cheng, Yixing Chen, Werner Lustermann, Andromachi Tsirou, Alexis Kalogeropoulos, Andrea Rizzi, Ioannis Papadopoulos, Paolo Ronchese, Thomas Muller, Ho Ling Li, Giuseppe Codispoti, Hua Zhang, Siyuan Wang, Peter Hansen, Daniel Gonzalez, Greig Alan Cowan, Tao Huang, Michele Bianco, Sun Hee Kim, Paul Turner, Wei Sun, Preema Rennee Pais, Raffaele Tito D'Agnolo, Maria Elena Stramaglia, Songmei Wu, Tommaso Colombo, Federica Legger, Yu Bai, Géraldine Conti, Dong Liu, John Wilson, Jin Wang, Stefano Rosati, Jun Guo, Andreas Alexander Maier, Lorenzo Massa, Lei Zhou, Nicolas Berger, Stefan Simion, Ruslan Mashinistov, Ourania Sidiropoulou, Peter Lichard, Eduardo Ros, Gino Marceca, Susan Cheatham, Ji Hyun Kim, Donghyun Kim, Dipanwita Dutta, Zheng Wang, Sanjeev Kumar, Wei Li, Yong Yang, Geng Chen, Yi Wang, Ajay Kumar, Ashish Sharma, Georgios Anagnostou, Joao Varela, Csaba Hajdu, Muhammad Ahmad, Ekaterina Kuznetsova, Ioannis Evangelou, Matthias Weber, Milos Dordevic, Vineet Kumar, Vladimir Petrov, Francesco Fiori, Quentin Python, Meng Xiao, Hao Liu, Sourav Sen, Yanlin Liu, Viktor Khristenko, Marco Trovato

Combined ATLAS and CMS measurements of the Higgs boson production and decay rates, as well as constraints on its couplings to vector bosons and fermions, are presented. The combination is based on the analysis of five production processes, namely gluon fusion, vector boson fusion, and associated production with a W or a Z boson or a pair of top quarks, and of the six decay modes H → ZZ, W W , γγ, ττ, bb, and μμ. All results are reported assuming a value of 125.09 GeV for the Higgs boson mass, the result of the combined measurement by the ATLAS and CMS experiments. The analysis uses the CERN LHC proton-proton collision data recorded by the ATLAS and CMS experiments in 2011 and 2012, corresponding to integrated luminosities per experiment of approximately 5 fb$^{−1}$ at $\sqrt{s}=7$ TeV and 20 fb$^{−1}$ at $\sqrt{s}=8$ TeV. The Higgs boson production and decay rates measured by the two experiments are combined within the context of three generic parameterisations: two based on cross sections and branching fractions, and one on ratios of coupling modifiers. Several interpretations of the measurements with more model-dependent parameterisations are also given. The combined signal yield relative to the Standard Model prediction is measured to be 1.09 ± 0.11. The combined measurements lead to observed significances for the vector boson fusion production process and for the H → ττ decay of 5.4 and 5.5 standard deviations, respectively. The data are consistent with the Standard Model predictions for all parameterisations considered.

2016Jian Wang, Matthias Finger, Lesya Shchutska, Qian Wang, Yiming Li, Matthias Wolf, Varun Sharma, Konstantin Androsov, Jan Steggemann, Leonardo Cristella, Xin Chen, Davide Di Croce, Ettore Zaffaroni, Yi Jiang, Clement Helsens, Christophe Clément, Snezana Nektarijevic, Niklaus Lehmann, Mingkui Wang, Zhirui Xu, Chao Wang, João Miguel das Neves Duarte, Tagir Aushev, Lei Zhang, Tian Cheng, Yixing Chen, Werner Lustermann, Andromachi Tsirou, Alexis Kalogeropoulos, Andrea Rizzi, Ioannis Papadopoulos, Paolo Ronchese, Thomas Muller, Ho Ling Li, Giuseppe Codispoti, Hua Zhang, Siyuan Wang, Peter Hansen, Daniel Gonzalez, Greig Alan Cowan, Tao Huang, David Vannerom, Michele Bianco, Kun Shi, Wei Shi, Abhisek Datta, Songmei Wu, Thomas Berger, Federica Legger, Jie Chen, Yang Liu, Wei Wang, John Wilson, Yu Zhang, Jin Wang, Stefano Rosati, Jun Guo, Lorenzo Massa, Mathieu Benoit, Nicolas Berger, Marco Valente, Stefan Simion, Ruslan Mashinistov, Ourania Sidiropoulou, Ke Li, Gino Marceca, Marcos Vinícius Silva Oliveira, Cherifa Sabrina Amrouche, Ji Hyun Kim, Donghyun Kim, Dipanwita Dutta, Zheng Wang, Sanjeev Kumar, Wei Li, Yong Yang, Geng Chen, Yi Wang, Ajay Kumar, Ashish Sharma, Georgios Anagnostou, Joao Varela, Csaba Hajdu, Muhammad Ahmad, Ekaterina Kuznetsova, Ioannis Evangelou, Matthias Weber, Muhammad Shoaib, Milos Dordevic, Vineet Kumar, Vladimir Petrov, Francesco Fiori, Quentin Python, Meng Xiao, Hao Liu, Sourav Sen, Yanlin Liu, Viktor Khristenko, Marco Trovato, Fan Xia, Xiao Wang

This paper presents the combinations of single-top-quark production cross-section measurements by the ATLAS and CMS Collaborations, using data from LHC proton-proton collisions at $\sqrt{s}$ = 7 and 8 TeV corresponding to integrated luminosities of 1.17 to 5.1 fb$^{−1}$ at $\sqrt{s}$ = 7 TeV and 12.2 to 20.3 fb$^{−1}$ at $\sqrt{s}$ = 8 TeV. These combinations are performed per centre-of-mass energy and for each production mode: t-channel, tW, and s-channel. The combined t-channel cross-sections are 67.5 ± 5.7 pb and 87.7 ± 5.8 pb at $\sqrt{s}$ = 7 and 8 TeV respectively. The combined tW cross-sections are 16.3 ± 4.1 pb and 23.1 ± 3.6 pb at $\sqrt{s}$ = 7 and 8 TeV respectively. For the s-channel cross-section, the combination yields 4.9 ± 1.4 pb at $\sqrt{s}$ = 8 TeV. The square of the magnitude of the CKM matrix element V$_{tb}$ multiplied by a form factor f$_{LV}$ is determined for each production mode and centre-of-mass energy, using the ratio of the measured cross-section to its theoretical prediction. It is assumed that the top-quark-related CKM matrix elements obey the relation |V$_{td}$|, |V$_{ts}$| ≪ |V$_{tb}$|. All the |f$_{LV}$V$_{tb}$|$^{2}$ determinations, extracted from individual ratios at $\sqrt{s}$ = 7 and 8 TeV, are combined, resulting in |f$_{LV}$V$_{tb}$| = 1.02 ± 0.04 (meas.) ± 0.02 (theo.). All combined measurements are consistent with their corresponding Standard Model predictions.

Jian Wang, Matthias Finger, Lesya Shchutska, Qian Wang, Yiming Li, Matthias Wolf, Varun Sharma, Konstantin Androsov, Jan Steggemann, Leonardo Cristella, Roberto Castello, Alessandro Degano, Xin Chen, Davide Di Croce, Yi Jiang, Clement Helsens, Christophe Clément, Snezana Nektarijevic, Mingkui Wang, Zhirui Xu, Chao Wang, João Miguel das Neves Duarte, Tagir Aushev, Lei Zhang, Tian Cheng, Yixing Chen, Werner Lustermann, Andromachi Tsirou, Alexis Kalogeropoulos, Andrea Rizzi, Ioannis Papadopoulos, Paolo Ronchese, Thomas Muller, Ho Ling Li, Giuseppe Codispoti, Hua Zhang, Siyuan Wang, Peter Hansen, Daniel Gonzalez, Greig Alan Cowan, Tao Huang, David Vannerom, Michele Bianco, Sun Hee Kim, Kun Shi, Wei Shi, Maria Elena Stramaglia, Songmei Wu, Federica Legger, Jie Chen, Géraldine Conti, Wei Wang, John Wilson, Yu Zhang, Jin Wang, Stefano Rosati, Jun Guo, Lorenzo Massa, Mathieu Benoit, Lei Zhou, Nicolas Berger, Marco Valente, Stefan Simion, Ruslan Mashinistov, Ourania Sidiropoulou, Gino Marceca, Ji Hyun Kim, Donghyun Kim, Dipanwita Dutta, Zheng Wang, Sanjeev Kumar, Wei Li, Yong Yang, Geng Chen, Yi Wang, Ajay Kumar, Ashish Sharma, Georgios Anagnostou, Joao Varela, Csaba Hajdu, Muhammad Ahmad, Ekaterina Kuznetsova, Ioannis Evangelou, Matthias Weber, Muhammad Shoaib, Milos Dordevic, Vineet Kumar, Vladimir Petrov, Francesco Fiori, Quentin Python, Meng Xiao, Hao Liu, Yanlin Liu, Viktor Khristenko, Marco Trovato, Gurpreet Singh, Fan Xia, Kai Yi, Bibhuprasad Mahakud, Jing Li

This paper presents combinations of inclusive and differential measurements of the charge asymmetry (A$_{C}$) in top quark pair $\left(\mathrm{t}\overline{\mathrm{t}}\right)$ events with a lepton+jets signature by the ATLAS and CMS Collaborations, using data from LHC proton-proton collisions at centre-of-mass energies of 7 and 8 TeV. The data correspond to integrated luminosities of about 5 and 20 fb$^{−1}$ for each experiment, respectively. The resulting combined LHC measurements of the inclusive charge asymmetry are A$_{C}^{CHC7}$ = 0.005 ± 0.007 (stat) ± 0.006(syst) at 7 TeV and A$_{C}^{CHC8}$ = 0.0055 ± 0.0023 (stat) ± 0.0025 (syst) at 8 TeV. These values, as well as the combination of A$_{C}$ measurements as a function of the invariant mass of the $\mathrm{t}\overline{\mathrm{t}}$ system at 8 TeV, are consistent with the respective standard model predictions.

2018