ATLAS Collaboration released the latest heavy resonance search results in diboson final state

 

 






 

 

 

 

On May 8th, 2018, ATLAS collaboration, being one of the main experiments at LHC CERN and consisting of ~3000 scientists all over the world, released the latest results on the search for the new physics via heavy resonance signatures in the diboson W/Z/H+photon final states (arXiv: 1805.01908).


http://atlas.cern/updates/physics-briefing/searching-forces-beyond-standard-model
https://twitter.com/ATLASexperiment/status/993840433825501184


On May 30th, 2018, this result was chosen by ATLAS as one of its annual physics highlights to be presented at the LHCC open session, with dedicate emphasis as “first search for a massive boson X decaying to Hγ”.


https://indico.cern.ch/event/726320/contributions/2988541/attachments/1658397/2655813/ATLAS_LHCC_May2018.pdf

By means of careful optimizations, categorizations and combinations of the searched phasespaces, ATLAS managed to obtain the most stringent diboson search cross section limits on the heavy resonance decaying into the W/Z/H+photon final states, for the 1st time up to the invariant mass of 6.7TeV in ever searched diboson channels. This work provides the latest and most stringent constraints on the new theory models that predict narrow width heavy particles decaying into W/Z/H+photon. Using the same amount of proton-proton collision dataset, the CMS physics results on Z+photon search only manages to probe the new physics limit up to 4TeV invariant mass. Moreover, the ATLAS result also provide, for the first time in the world, the search limits on the cross section of a heavy vector boson decaying into H+photon final states.

      

This work has been led and completed by Dr. Shu LI, the T.D. Lee Junior Fellow of Tsung-Dao Lee Institute (TDLI) and Institute of Nuclear and Particle Physics (INPAC) School of Physics and Astronomy, Shanghai Jiao Tong University, and Dr. Zhijun LIANG, the associate research fellow of Institute of High Energy Physics, Beijing. Being one of the two analysis coordinators, Dr. Shu LI has introduced for the first time the benchmark model of Higgs+Photon heavy resonances into the LHC experiment physics analysis, and has initiated and driven the analysis process till the final accomplishment.

Dr. Shu LI did his undergraduate study at the Special Class for Gifted Young (SCGY) in University of Science and Technology of China (USTC) and graduated in 2008. After that, he continued his gradschool at the Department of Modern Physics, USTC, under the supervision of Prof. Zhengguo ZHAO, academician of Chinese Academy of Sciences, where he finished his physics PhD thesis half a year ahead of schedule at the end of 2012. Starting from 2013, he worked as postdoctoral research fellow at Duke University and based at CERN, deeply involved in the research on the high energy frontier experimental particle physics with the ATLAS experiment. He joined the newly founded Tsung-Dao Lee Institute as the first T.D. Lee Junior Fellow, co-appointed by the Institute of Nuclear and Particle Physics, School of Physics and Astronomy, Shanghai Jiao Tong University. Dr. Shu LI has quite a few remarkable research achievements in his career, such as: the precise measurement of the Standard Model background of Higgs to WW which greatly helped with the Higgs discovery in 2012, the first observantion of triboson Zγγ rare process at LHC and probe of anomalous gauge couplings, the first ATLAS measurement of electroweak Zγ+jj process with vector boson scattering topology, the search for heavy resonances decaying into Z+photon which greatly helped to resolve the 750GeV puzzle in 2016, the first ever search for heavy resonances decaying into Higgs+photon final states at LHC. With the high recognition of his contribution, he has been appointed by the ATLAS collaboration (~3000 members in the world) to several important leadership positions such as: 2015/12-2017/01, the convener of the Monte Carlo Validation Group; 2017/04-2018/03, the convener of the Standard Model Electroweak (SM-EWK) Physics Group; 2018/04-Present, the convener of the Monte Carlo Generator Development and Tuning Group. Especially, the SM-EWK group has got ~200 participants from ~50 different research institutions worldwide including Havard, UC Berkeley, Oxford, Michigan etc., working on tens of multiboson production measurement and anomalous coupling search topics.


LHC实验上首例对重质量玻色子衰变为 希格斯粒子和光子的新物理探索
Published:2018-06-06 Hits:71

众所周知,2012年欧洲核子研究中心大型强子对撞机(LHC)实验上发现了希格斯玻色子,成功解释了基本粒子的质量起源,为2013年的诺贝尔物理学奖提供了最关键的实验证据,是过去半个多世纪基础物理学最重大的科学发现之一。此后大型强子对撞机通过能量和亮度升级,2015年重新启动,运行在更高的能区13万亿电子伏特,积累了大统计量的质子对撞实验数据。除了对希格斯粒子的各种性质进行精确测量外,寻找超出标准模型的新粒子,如重质量的共振态粒子,超对称理论预言的粒子等,是LHC实验的重要物理目标。

                   

 

2018年5月8日,ATLAS国际合作组(约3000人)专题报导了寻找重质量共振态粒子衰变到W/Z/H和光子末态的最新研究结果(arXiv:1805.01908)。通过对W/Z/H+光子末态新物理寻找的多个相空间重新优化和联合统计分析,在LHC实验所能达到的最高不变质量区(达6.8万亿电子伏特),获得了新共振态粒子衰变到矢量双玻色子(W/Z+光子)衰变截面的统计上限。对重质量新粒子到W/Z和光子双玻色子衰变的理论模型作出了最新、最严格的实验检验和统计限制。同时,在LHC实验中首次提出了重共振态粒子衰变到希格斯粒子+光子末态的新物理课题,并发布了在1-3万亿电子伏特质量区间,新粒子到希格斯粒子+光子衰变截面的统计上限。

该结果随后于2018年5月30日,被ATLAS合作组选为年度代表性物理成果之一,于LHC委员会公开会议(LHCC)上作为“First search for a massive boson X decaying to Hγ”的亮点研究报告。

该研究课题由上海交通大学李政道研究所(TDLI)与物理与天文学院粒子和核物理研究所(INPAC)青年学者李数,和中科院高能物理研究所梁志均,合作和主导完成。李数作为课题负责人之一,在LHC实验中首次引入了希格斯粒子和光子二体共振态的理论模型,负责和推动了整个物理分析工作的开展和顺利完成。

 

李数研究员2008年毕业于中国科学技术大学,2012年获得博士,师从赵政国院士;2013-2017年在美国杜克大学作博士后;2017年起作为首位“李政道青年学者”加盟李政道研究所和上海交通大学物理与天文学院粒子和核物理研究所(INPAC)。2009年起从事LHC/ATLAS实验前沿课题研究,历任ATLAS合作组蒙特卡洛验证组负责人(2015-2017),标准模型电弱物理组负责人(2017-2018),蒙特卡洛产生子研发组负责人(2018.4-)。重要的研究成果还包括:1)WW玻色子产生截面和反常耦合测量、2)精确测量希格斯粒子的WW衰变道标准模型本底、3)LHC首次发现三玻色子(Z和双光子)稀有过程及反常耦合测量、4)ATLAS首篇Z+光子+双喷注纯电弱相互作用散射过程测量,有效排除750GeV疑似共振态的Z+光子重质量共振态信号。

http://atlas.cern/updates/physics-briefing/searching-forces-beyond-standard-model

https://arxiv.org/abs/1805.01908



 

 

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