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SJTU Team Contributed to LHC Research’s Result of New Model of Higgs Boson Production

June 11, 2018      Author: Li Liang

The latest research result of large hadron collider (LHC) experiment was presented recently by European Organization for Nuclear Research, ATLAS Collaboration and CMS Collaboration. Both collaborations found Higgs boson production in association with a top quark pair (ttH). This is another milestone in the field of Higgs physics and even particle physics.

The ttH research team from Institute of Nuclear and Particle Physics of SJTU School of Physics and Astronomy, with principle members as Distinguished Researcher, Li Liang, Post Doctor Li Xingguo and Doctor Hu Shuyang, participated in measurement and analysis of ttH production led by ATLAS Collaboration. The team directly contributed to the measurement result of bottom quark pair reaction channel because the previous result of this reaction channel had already been published in Physical Review D as one of the team’s first ttH production experimental evidences. The team’s research was founded by the Organization Department of the Central Committee of the CPC “Young Overseas High-Level Talents Introduction Plan” and National Natural Science Foundation of China.

ABSTRACT: A search for the standard model Higgs boson produced in association with a top-quark pair, t¯tH, is presented. The analysis uses 36.1  fb1 of pp collision data at s=13  TeV collected with the ATLAS detector at the Large Hadron Collider in 2015 and 2016. The search targets the H→b¯b decay mode. The selected events contain either one or two electrons or muons from the top-quark decays, and are then categorized according to the number of jets and how likely these are to contain b-hadrons. Multivariate techniques are used to discriminate between signal and background events, the latter being dominated by t¯t+jets production. For a Higgs boson mass of 125 GeV, the ratio of the measured t¯tH signal cross-section to the standard model expectation is found to be μ=0.84+0.640.61. A value of μ greater than 2.0 is excluded at 95% confidence level (C.L.) while the expected upper limit is μ<1.2 in the absence of a t¯tH signal.


Translated by Zhang Qianqian  Reviewed by Wang Bingyu