🤖 AI Summary
**ブロックヘブン国立研究所（BNL）の相対論的重イオン衝突型加速器（RHIC）が閉鎖**
- 2026年2月6日、DOE副長官ダリオ・ギルが赤いボタンを押し、25年にわたるRHICの運転を終了。
- 最後の実験では数百ペタバイトに上るデータが取得され、仮想粒子の直接観測など新たな成果が報告された。
**RHICの主な功績**
- 2000年の本格稼働以降、金イオン同士の衝突でクォーク・グルオン・プラズマ（QGP）を生成し、液体のように「完璧」な性質（摩擦ゼロ、極大渦度）を示した。
- 最高温度約4兆度のプラズマを実現し、ガンマ線や反物質の大量生成、陽子スピン問題の解決に近づくなど、素粒子物理と宇宙初期状態の理解を大きく前進させた。
- 2つの陽子ビームをスピンを揃えて衝突させる技術は、現在も唯一の実績である。
**次世代施設：電子イオン衝突型加速器（EIC）**
- RHICの地下リングの一つを再利用し、電子ビームとイオンビームを衝突させる新装置を10年計画で建設予定。
- EICは米国初の新粒子加速器となり、クォーク・グルオンの構造解明や最強相互作用の詳細研究に向けた「小さなナイフ」役割を担う。
- 若手研究者にとって世界トップクラスの研究拠点となり、米国の粒子物理学が欧州・アジアに続いていた勢いを取り戻すことが期待されている。
**結論**
RHICは「唯一の米国内ヘッドオン衝突型加速器」として、25年間にわたり素粒子・核物理の最前線を切り開いた。その科学的遺産は膨大なデータとともに残り、すぐに終わりを迎えるわけではない。一方、EICの建設はRHICの成果を受け継ぎ、次世代の探求領域へと踏み出す重要なステップとなる。
2001: "Brookhaven Labs has produced for the first time collisions of gold nuclei at a center of mass energy of 200GeV/nucleon."
2002: "There may be a new type of matter according to researchers at Brookhaven National Laboratory."
2010: The hottest man-made temperatures ever achived were a record 4 trillion degree plasma experiment at Brookhaven National Laboratory in New York... anointed the Guinness record holder."
2023: "Scientists at Brookhaven National Laboratory have uncovered an entirely new kind of quantum entanglement."
2026: On Friday, February 6, "a control room full of scientists, administrators and members of the press gathered" at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Lab in Upton, New York to witness its final collisions, reports Scientific American:
The vibe had been wistful, but the crowd broke into applause as Darío Gil, the Under Secretary for Science at the U.S. Department of Energy, pressed a red button to end the collider's quarter-century saga... "I'm really sad" [said Angelika Drees, a BNL accelerator physicist]. "It was such a beautiful experiment and my research home for 27 years. But we're going to put something even better there."
That "something" will be a far more powerful electron-ion collider to further push the frontiers of physics, extend RHIC's legacy and maintain the lab's position as a center of discovery. This successor will be built in part from RHIC's bones, especially from one of its two giant, subterranean storage rings that once held the retiring collider's supply of circulating, near-light speed nuclei...slated for construction over the next decade. [That Electron-Ion Collider, or EIC] will utilize much of RHIC's infrastructure, replacing one of its ion rings with a new ring for cycling electrons. The EIC will use those tiny, fast-flying electrons as tiny knives for slicing open the much larger gold ions. Physicists will get an unrivaled look into the workings of quarks and gluons and yet another chance to grapple with nature's strongest force. "We knew for the EIC to happen, RHIC needed to end," says Wolfram Fischer, who chairs BNL's collider-accelerator department. "It's bittersweet."
EIC will be the first new collider built in the US since RHIC. To some, it signifies the country's reentry into a particle physics landscape it has largely ceded to Europe and Asia over the past two decades. "For at least 10 or 15 years," says Abhay Deshpande, BNL's associate laboratory director for nuclear and particle physics, "this will be the number one place in the world for [young physicists] to come."
The RHIC was able "to separately send two protons colliding with precisely aligned spins — something that, even today, no other experiment has yet matched," the article points out:
During its record-breaking 25-year run, RHIC illuminated nature's thorniest force and its most fundamental constituents. It created the heaviest, most elaborate assemblages of antimatter ever seen. It nearly put to rest a decades-long crisis over the proton's spin. And, of course, it brought physicists closer to the big bang than ever before...
When RHIC at last began full operations in 2000, its initial heavy-ion collisions almost immediately pumped out quark-gluon plasma. But demonstrating this beyond a shadow of a doubt proved in some respects more challenging than actually creating the elusive plasma itself, with the case for success strengthening as RHIC's numbers of collisions soared. By 2010 RHIC's scientists were confident enough to declare that the hot soup they'd been studying for a decade was hot and soupy enough to convincingly constitute a quark-gluon plasma. And it was even weirder than they thought. Instead of the gas of quarks and gluons theorists expected, the plasma acted like a swirling liquid unprecedented in nature. It was nearly "perfect," with zero friction, and set a new record for twistiness, or "vorticity." For Paul Mantica, a division director for the Facilities and Project Management Division in the DOE's Office of Nuclear Physics, this was the highlight of RHIC's storied existence. "It was paradigm-changing," he says...
Data from the final run (which began nearly a year ago) has already produced yet another discovery: the first-ever direct evidence of "virtual particles" in RHIC's subatomic puffs of quark-gluon plasma, constituting an unprecedented probe of the quantum vacuum.
RHIC's last run generated hundreds of petabytes of data, the article points out, meaning its final smash "isn't really the end; even when its collisions stop, its science will live on."
But Science News notes RHIC's closure "marks the end for the only particle collider operating in the United States, and the only collider of its kind in the world. Most particle accelerators are unable to steer two particle beams to crash head-on into one another."
Read more of this story at Slashdot.
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