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Publication# Measurements of the Higgs boson production and decay rates and constraints on its couplings from a combined ATLAS and CMS analysis of the LHC pp collision data at $ \sqrt{s}=7 $ and 8 TeV

Muhammad Ahmad, Benjamin William Allen, Georgios Anagnostou, Konstantin Androsov, Spyridon Argyropoulos, Alexandre Aubin, Nicolas Berger, Michele Bianco, Alexey Boldyrev, Simone Campana, João Carvalho, Roberto Castello, Juan Ramon Castiñeiras De Saa, Matevz Cerv, Susan Cheatham, Yixing Chen, Xin Chen, Chunhui Chen, Tian Cheng, Davide Cieri, Christophe Clément, Giuseppe Codispoti, Tommaso Colombo, Géraldine Conti, Greig Alan Cowan, Alessandro Degano, Sergey Denisov, Charles Dietz, Milos Dordevic, Dipanwita Dutta, Matthias Finger, Francesco Fiori, Julia Fischer, Daniel Gonzalez, Jun Guo, Yifei Guo, Ruchi Gupta, Seungkyu Ha, Csaba Hajdu, Peter Hansen, Ali Harb, James Henderson, Haoshuang Ji, Yi Jiang, Shan Jin, Alexis Kalogeropoulos, Viktor Khristenko, Donghyun Kim, Sun Hee Kim, Ji Hyun Kim, Vineet Kumar, Ajay Kumar, Sanjeev Kumar, Ekaterina Kuznetsova, Federica Legger, Ho Ling Li, Qi Li, Lei Li, Bing Li, Xuan Li, Yiming Li, Wei Li, Peter Lichard, Hao Liu, Bo Liu, Jian Liu, Kun Liu, Zhen Liu, Lulu Liu, Dong Liu, Shuai Liu, Werner Lustermann, Alexander Madsen, Bibhuprasad Mahakud, Andreas Alexander Maier, Gino Marceca, Ruslan Mashinistov, Lorenzo Massa, Maren Tabea Meinhard, Jean-Pierre Meyer, Thomas Muller, Snezana Nektarijevic, Marzio Nessi, Konstantinos Nikolopoulos, Preema Rennee Pais, Ioannis Papadopoulos, Vladimir Petrov, Quentin Python, Yang Qin, Robert Richter, Andrea Rizzi, Paolo Ronchese, Manfredi Ronzani, Eduardo Ros, Stefano Rosati, Edoardo Rossi, Daniela Salvatore, Sourav Sen, Ashish Sharma, Varun Sharma

2016

Journal paper

2016

Journal paper

Abstract

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.

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Muhammad Ahmad, Georgios Anagnostou, Konstantin Androsov, Giovanni Bianchi, Roberto Castello, Jie Chen, Yixing Chen, Tian Cheng, Giuseppe Codispoti, Alessandro Degano, Charles Dietz, Dipanwita Dutta, Matthias Finger, Francesco Fiori, Yu Fu, Yifei Guo, Ruchi Gupta, Csaba Hajdu, Alexis Kalogeropoulos, Ji Hyun Kim, Donghyun Kim, Vineet Kumar, Ajay Kumar, Sanjeev Kumar, Ekaterina Kuznetsova, Ho Ling Li, Wei Li, Hao Liu, Shuai Liu, Werner Lustermann, Matteo Marone, Thomas Muller, Ioannis Papadopoulos, Vladimir Petrov, Quentin Python, Andrea Rizzi, Paolo Ronchese, Sourav Sen, Ashish Sharma, Varun Sharma, Lesya Shchutska, Muhammad Shoaib, Michal Simon, Gurpreet Singh, Jan Steggemann, Wei Sun, Andromachi Tsirou, Paul Turner, Joao Varela, Jian Wang, Xiao Wang, Mingkui Wang, Qian Wang, Zheng Wang, Matthias Weber, Matthias Wolf, Wenjing Wu, Fan Yang, Yong Yang, Kai Yi, Lei Zhang, Yu Zheng

The discovery of a new boson with a mass of approximately 125 GeV in 2012 at the LHC has heralded a new era in understanding the nature of electroweak symmetry breaking and possibly completing the standard model of particle physics. Since the first observation in decays to gamma gamma, WW, and ZZ boson pairs, an extensive set of measurements of the mass and couplings to W and Z bosons, as well as multiple tests of the spin-parity quantum numbers, have revealed that the properties of the new boson are consistent with those of the long-sought agent responsible for electroweak symmetry breaking. An important open question is whether the new particle also couples to fermions, and in particular to down-type fermions, since the current measurements mainly constrain the couplings to the up-type top quark. Determination of the couplings to down-type fermions requires direct measurement of the corresponding Higgs boson decays, as recently reported by the CMS experiment in the study of Higgs decays to bottom quarks and tau leptons. In this paper we report the combination of these two channels which results, for the first time, in strong evidence for the direct coupling of the 125 GeV Higgs boson to down-type fermions, with an observed significance of 3.8 standard deviations, when 4.4 are expected.

2014Muhammad Ahmad, Georgios Anagnostou, Konstantin Androsov, Alexandre Aubin, Giovanni Bianchi, Roberto Castello, Yixing Chen, Tian Cheng, Giuseppe Codispoti, Alessandro Degano, Charles Dietz, Milos Dordevic, Dipanwita Dutta, Matthias Finger, Francesco Fiori, Yifei Guo, Ruchi Gupta, Csaba Hajdu, Alexis Kalogeropoulos, Ji Hyun Kim, Donghyun Kim, Vineet Kumar, Ajay Kumar, Sanjeev Kumar, Ekaterina Kuznetsova, Wei Li, Ho Ling Li, Shuai Liu, Hao Liu, Werner Lustermann, Matteo Marone, Thomas Muller, Ioannis Papadopoulos, Vladimir Petrov, Quentin Python, Andrea Rizzi, Paolo Ronchese, Sourav Sen, Ashish Sharma, Varun Sharma, Lesya Shchutska, Muhammad Shoaib, Michal Simon, Gurpreet Singh, Jan Steggemann, Wei Sun, Andromachi Tsirou, Paul Turner, Joao Varela, Rui Wang, Zheng Wang, Xiao Wang, Jian Wang, Qian Wang, Matthias Weber, Matthias Wolf, Fan Yang, Yong Yang, Kai Yi, Lei Zhang, Yu Zheng

A measurement of the cross section for the production of top quark–antiquark pairs ( ${\mathrm {t}}\overline{{\mathrm {t}}}$ ) in association with a vector boson V (W or Z) in proton-proton collisions at $\sqrt{s} = 8$ $\,\text {TeV}$ is presented. The results are based on a dataset corresponding to an integrated luminosity of 19.5 fb$^{-1}$ recorded with the CMS detector at the LHC. The measurement is performed in three leptonic (e and $\mu$) channels: a same-sign dilepton analysis targeting ${\mathrm {t}}\overline{{\mathrm {t}}} \mathrm {W}$ events, and trilepton and four-lepton analyses designed for ${\mathrm {t}}\overline{{\mathrm {t}}} {\mathrm {Z}}$ events. In the same-sign dilepton channel, the ${\mathrm {t}}\overline{{\mathrm {t}}} \mathrm {W}$ cross section is measured as $\sigma _{{\mathrm {t}}\overline{{\mathrm {t}}} \mathrm {W}} = 170 ^{+90-80}\,\text {(stat)} \pm 70\,\text {(syst)} \, \text {fb}$ , corresponding to a significance of 1.6 standard deviations over the background-only hypothesis. Combining the trilepton and four-lepton channels, a direct measurement of the ${\mathrm {t}}\overline{{\mathrm {t}}} {\mathrm {Z}}$ cross section, $\sigma _{{\mathrm {t}}\overline{{\mathrm {t}}} {\mathrm {Z}}} = 200 ^{+80-70}\,\text {(stat)} ^{+40-30}\,\text {(syst)} \mathrm{fb}^{-1}$ , is obtained with a significance of 3.1 standard deviations. The measured cross sections are compatible with standard model predictions within their experimental uncertainties. The inclusive ${\mathrm {t}}\overline{{\mathrm {t}}} {\mathrm {V}}$ process is observed with a significance of 3.7 standard deviations from the combination of all three leptonic channels.

2014Muhammad Ahmad, Benjamin William Allen, Georgios Anagnostou, Konstantin Androsov, Tagir Aushev, Michele Bianco, Yixing Chen, Xin Chen, Tian Cheng, Davide Cieri, Giuseppe Codispoti, Pratyush Das, Abhisek Datta, Milos Dordevic, Dipanwita Dutta, Matthias Finger, Francesco Fiori, Daniel Gonzalez, Ruchi Gupta, Seungkyu Ha, Csaba Hajdu, Peter Hansen, Ali Harb, Miao Hu, Alexis Kalogeropoulos, Viktor Khristenko, Ji Hyun Kim, Donghyun Kim, Vineet Kumar, Sanjeev Kumar, Ajay Kumar, Ekaterina Kuznetsova, Wei Li, Jing Li, Lei Li, Ho Ling Li, Zhen Liu, Hao Liu, Werner Lustermann, Bibhuprasad Mahakud, Maren Tabea Meinhard, Thomas Muller, Ioannis Papadopoulos, Vladimir Petrov, Quentin Python, Andrea Rizzi, Paolo Ronchese, Sourav Sen, Ashish Sharma, Varun Sharma, Lesya Shchutska, Wei Shi, Kun Shi, Muhammad Shoaib, Gurpreet Singh, Jan Steggemann, Marco Trovato, Andromachi Tsirou, David Vannerom, Joao Varela, Yi Wang, Zheng Wang, Qian Wang, Siyuan Wang, Jian Wang, Mingkui Wang, Hui Wang, Xiao Wang, Muhammad Waqas, Matthias Weber, Matthias Wolf, Fan Xia, Meng Xiao, Zhirui Xu, Yong Yang

Combined measurements of the production and decay rates of the Higgs boson, as well as its couplings to vector bosons and fermions, are presented. The analysis uses the LHC proton–proton collision data set recorded with the CMS detector in 2016 at $\sqrt{s}=13\,\text {Te}\text {V}$ , corresponding to an integrated luminosity of 35.9 ${\,\text {fb}^{-1}}$ . The combination is based on analyses targeting the five main Higgs boson production mechanisms (gluon fusion, vector boson fusion, and associated production with a $\mathrm {W}$ or $\mathrm {Z}$ boson, or a top quark-antiquark pair) and the following decay modes: $\mathrm {H} \rightarrow \gamma \gamma$ , $\mathrm {Z}\mathrm {Z}$ , $\mathrm {W}\mathrm {W}$ , $\mathrm {\tau }\mathrm {\tau }$ , $\mathrm {b} \mathrm {b}$ , and $\mathrm {\mu }\mathrm {\mu }$ . Searches for invisible Higgs boson decays are also considered. The best-fit ratio of the signal yield to the standard model expectation is measured to be $\mu =1.17\pm 0.10$ , assuming a Higgs boson mass of $125.09\,\text {Ge}\text {V}$ . Additional results are given for various assumptions on the scaling behavior of the production and decay modes, including generic parametrizations based on ratios of cross sections and branching fractions or couplings. The results are compatible with the standard model predictions in all parametrizations considered. In addition, constraints are placed on various two Higgs doublet models.