7月4日はヒッグスの日 (Higgs Day, July 4, 2012)

　素粒子に質量を与える原因と考えられる仮説上の素粒子「ヒッグス粒子」を探しているジュネーブの欧州合同原子核研究所（CERN＝セルン）が、7月4日の午前9時（現地時間。日本時間では午後4時）から、超大型粒子加速器 LHC による実験の報告会を行なった。会の様子はウェブで放映されたので、高エネルギー物理学の熱心なファンである私は、丸2時間、パソコンに釘付けになって見ていた（そのビデオは、"Latest update in the search for the Higgs boson" の題名で CERN Document Server に保存されている）。

　最初に CMS 実験グループを代表して、カリフォルニア大学サンタ・バーバラ校の Joe Incandela 氏が、続いて ATLAS グループを代表して CERN の Fabiola Gianotti さんが報告した。両者それぞれの高精度の結果が示された瞬間には、聴衆から大拍手が巻き起こった。どちらの発表もまだ予備的なものだが、質量領域 125〜126 GeV のところに新しい粒子の存在する可能性が十分高くなったということであった。この粒子の存在を理論的に予言したピーター・ヒッグス氏が会場に招かれていたが、「このようなことが私の生きている間に起こったとは信じ難い」と語った。

　ウェブ放映に平行して、その放映を見ている専門家たちのツイートも、私はパソコンの別ウィンドウで眺め、ときどきリツイートした。そのため、当日の私のツイートの数は 23 となり、東北大地震の起きた 2011年3月11日の 34 と、日本時間の午後10時から今回の報告よりももっと予備的な段階で LHC 実験の報告が CERN で行なわれた翌日である 2011年12月14日の 26 に次ぐものであった。この記事の末尾に、関連の報道や解説へのリンクをいくつか載せておく。

At the European Organization for Nuclear Research (also called CERN) located in Geneva, scientists have been experimentally looking for the hypothetical "Higgs particle," which is considered to have given masses to elementary particles. From 9:00 am (local time; 4:00 pm in Japan) of July 4, 2012, a meeting to announce the results of the experiments by the use of the largest ever accelerator, LHC, was held at CERN. The event was aired on the Web, so that I, an enthusiastic fan of high energy physics, was glued to the computer for two hours to watch it (the video of the webcast entitled "Latest update in the search for the Higgs boson" is now stored on the CERN Document Server).

First, Joe Incandela of the University of California at Santa Barbara, reported on behalf of the CMS experiment. Next, Fabiola Gianotti of CERN has reported on behalf of the ATLAS group. When the result of high precision was shown by each presenter, a large applause occurred among the audience. Both the presentations were preliminary, but it has become highly probable that a new particle exists in the mass region around 125–126 GeV. Peter Higgs who theoretically predicted the existence of this particle was invited at the meeting and said, "It is incredible that this has happened in my lifetime."

While watching the webcast, I viewed, in a separate window of the computer, tweets of those experts who were also watching the webcast, retweeting at times some of their words. Thus, the number of my tweets on that day became 23, the largest number next to the number 34 of March 11, 2011, when the large earthquake occurred in Tohoku area, and 26 of December 14, 2011, which was the next day (in Japan time) of the earlier announcements at CERN of the LHC experiments. Some links to the news and explanations related to these epoch-making announcements are given below.

Further reading

1. 素粒子:「ヒッグス粒子」発見か：CERN 発表. 毎日jp (July 4, 2012; revised in July 5, 2012) In Japanese; English version: Eureka! Physicists celebrate evidence of particle. The Mainichi (July 5, 2012).
2. Higgs boson: it's unofficial! Cern scientists discover missing particle. Guardian (July 4, 2012).
3. Physicists find elusive particle seen as key to Universe. New York Times (July 4, 2012).
4. What in the world is a Higgs boson? ibid. (July 4, 2012).
5. Stephen Hawking on Higgs: 'Discovery has lost me $100.' BBC News [video] (July 4, 2012).
6. Search for Higgs boson at Large Hadron Collider reveals new particle. Symmetry Breaking: A Joint Fermilab/SLAC Publication (July 4, 2012).
7. Thanks, Mom! Finding the Quantum of Ubiquitous Resistance. By Frank Wilczek, NOVA's Physics Blog: The Nature of Reality (July 4, 2012).
8. How the Higgs gives mass to the universe. By Ethan Siegel, Blog: Start With a BANG! (July 4, 2012).
9. It's a boson, but what sort? - CERN physicists digest implications of historic discovery. physicsworld.com (July 5, 2012).
10. A new era dawns. By Matt Strassler, Blog: Of Particular Significance (July 5, 2012).

Note added later: You can see additional links to Higgs stories at my twitter record of July 6, 2012.