THE DISCOVERY OF THE Higgs PARTICLE IN 2012
The Higgs discovery was a culmination of two decades of work by the ingenious LHC machine physicists and by 6000 ATLAS and CMS physicists who built and now operate the detectors, designed and manage a computer system that distributes data around the world, created novel hardware and computer software to identify the most interesting collisions, and wrote the algorithms that dig out the most pertinent events from the great morass of data being recorded.
For over twenty years, in ALEPH at LEP, and ATLAS at LHC, Wu has chosen the Higgs search as primary challenge. The Higgs discovery, announced on July 4, 2012, is a giant step towards understanding the fundamental laws of nature. We have played a seminal role in the discovery.
CERN Council Meeting. On December 13, 2011, ATLAS and CMS showed an intriguing excess at mH=125GeV, mainly from the H→γγ and H→4 leptons channels. We made outstanding contributions to the results in both channels and to the ATLAS Higgs combination result of 3.6σ.
CERN Public Seminar. On July 4, 2012, in a joint ATLAS-CMS seminar, CERN announced the discovery of a new particle resulting from the search for the Higgs boson, using a dataset of 4.8 fb-1 at 7 TeV and 5.9 fb-1 at 8 TeV. In ATLAS, the significance of the excess was 4.5σ in H→γγ and 3.4σ in H→ZZ→4 leptons. Combined with other Higgs channels, the significance was 5.1σ; i.e., the chance that the observation is due to background fluctuations was one part in 3.5 million. Our group played an outstanding and leading role in producing these results:
1. We are one of the two groups who first obtained the H→γγ final results of 4.5σ that led to the discovery. Wisconsin graduate student Haichen Wang, who contributed intensively in ATLAS in the H→γγ channel, was among the physicists who produced the results and the plot in Figure 1 (local p0: probability that the background fluctuates to the observed data, or higher). He has been awarded two postdoc fellowships – the Chamberlain Fellowship at Berkeley and the Enrico Fermi Fellowship at the University of Chicago.
2. We played an outstanding role in obtaining the result in the H→4-lepton channel. Wisconsin graduate student X. Ju was among the physicists who produced this statistical result of 3.4σ and the plot shown in Figure 2. For his work on this channel, Assistant Scientist Luis Flores has been awarded the prize for Scientific Research 2012 of the Mexican Physical Society.
3. Wisconsin graduate student, H. Ji, is one of the physicists who first obtained the final Higgs discovery significance of 5.1σ on June 25, 2012 at 3pm, which is the stringent standard that one insists on to claim a discovery. He was among the physicists who produced the result and the plot shown in Figure 3.
4. All our many years of work, together with our ATLAS collaborators, culminated in the publication of the Higgs discovery paper, which was submitted on July 31, 2012, and was published in Phys Lett. B 716 (2012) 1-29. The result and plot of 5.9σ; were produced by our Grad. Student H. Ji together with other physicists, and made it to the cover of Phys. Lett. B
Phys. Lett. B 716 (2012), Issue 1