April 24, 2011 Kent State plays a prominent role in new antimatter discovery published today;
Antihelium-4 expected to remain the heaviest stable antinucleus for decades to come
Kent State University researchers are co-leaders of a team of international scientists who have discovered
antihelium-4, the most massive antinucleus known to date. This new discovery is the antimatter partner of
the helium-4 nucleus, also called the alpha particle. Helium-4 is the normal form of helium the
second most abundant element in the universe, after hydrogen.
The international team of scientists studies high-energy collisions of gold nuclei at the Relativistic Heavy
Ion Collider (RHIC), a 2.4 mile-circumference particle accelerator at the U.S Department of Energy’s
Brookhaven National Laboratory on Long Island, NY. The new antinucleus was discovered at RHIC’s STAR
detector, and the same group set the world record for the heaviest known antinucleus just last year. The
new antihelium-4 is a negatively charged state of antimatter containing two antiprotons and two antineutrons,
and does not undergo radioactive decay. The last stable antinucleus discovery was at a Russian accelerator
in 1971. To break the new record for stable antimatter established by the
present discovery, a future experiment would need to find an antinucleus containing six antiparticles, and
if this were produced by the same mechanism, it would be rarer by a factor of 2.6 million. This huge factor
puts that next milestone out of reach for the foreseeable future.
The Author Contact person on behalf of the full international team is Brookhaven scientist Aihong Tang, who
received his doctoral degree from Kent State in 2002. The findings were presented outside the STAR
collaboration for the first time in a colloquium by Aihong Tang at Brookhaven on April 19. The first
scheduled presentation of the new discovery at a conference will be by KSU Prof. Declan Keane at a meeting
sponsored by the American Physical Society in Anaheim, California, on April 27.
Kent State faculty members Declan Keane and Spiros Margetis are the principal investigators of a project
funded by the US Dept of Energy, of which a major goal was the pursuit of this research. The peer-reviewed
findings were published by the journal Nature on April 24, 2011. Nature is the world's most highly-cited
interdisciplinary science journal.
Collisions at RHIC fleetingly produce conditions that existed a few microseconds after the Big Bang, which
gave birth to the universe some 13.7 billion years ago. Our understanding is that matter and antimatter
were initially created with equal abundance immediately following the Big Bang, and the predominance of
matter in the visible universe today remains a major unsolved scientific mystery. Experiments such as the
Alpha Magnetic Spectrometer, which will search for evidence of bulk
antimatter somewhere in the cosmos, will make use of the new measurements by STAR of antihelium production
in terrestrial matter-on-matter collisions when interpreting the data they will observe in space.
Research by Ernest Rutherford in 1911 first revealed that the atom consists of a compact nucleus surrounded
by electrons. Rutherford’s experiments, which ushered in the era of modern subatomic science, used alpha
particles colliding with gold to discover the nucleus; exactly 100 years later, the STAR collaboration used
gold colliding with gold to discover the anti-alpha. There is a noteworthy synergy and symmetry associated
with this coincidence.
Several other members of the Kent State physics department are co-authors of the new paper by virtue of
their vital contributions to constructing and operating the various interlocking subsystems of the STAR
detector, including emeritus professor Bryon Anderson, postdoctoral researchers Jonathan Bouchet and
Lokesh Kumar, Senior Research Fellow Wei-Ming Zhang, and graduate students Jeremy Alford, Jaiby Joseph,
Yadav Pandit, Amilkar Quintero and Joe Vanfossen.
More details of the discovery can be found in the Press Release by the
of Brookhaven National Laboratory.
January 2011 Kent State's discovery named as one of "Top 5" at Brookhaven Lab
Brookhaven National Lab has a staff of about 3,000 scientists and support personnel and
hosts about 4,000 guest researchers every year. Activities span many areas of physics,
chemistry and biology, and past work at Brookhaven has yielded 7 Nobel Prizes. In 2010,
research at Brookhaven led to over 800 peer-reviewed journal articles. In January 2011,
Brookhaven laboratory management identified a paper in the journal Science about
an antimatter discovery, spearheaded by Kent State (see below for specifics) as one of
Brookhaven's Top 5
Scientific Discoveries of 2010.
August 2010 Paper with important implications for Dark Energy co-authored by Prof. Tandy
"Void that is truly empty solves dark energy puzzle" is the tantalizing title
of an article by the science journalist Rachel Courtland in the periodical New Scientist.
Courtland's article is based on a refereed paper in the area of theoretical physics published
this month in the journal Physical Review, authored by Kent State's Prof. Peter Tandy and three
other scientists. The work by Prof. Tandy and his collaborators represents a discovery within
the framework of the highly mathematical theory of Quantum Chromodynamics, and has a connection
to the Cosmological Constant. The Cosmological Constant was first introduced by Einstein, but
was later abandoned by him; he described it as his "biggest blunder". New discoveries about the
universe since Einstein's death have revived the Cosmological Constant.
March 2010 Discovery of the heaviest known antinucleus
High energy nuclear physicists from our department have played a prominent role in a new
discovery the heaviest known antimatter nucleus reported this month in the
journal Science. It is also the first antinucleus to contain a "strange" quark;
normal nuclei contain only "up" and "down" quarks. To learn about this discovery and
the prominent role of Dr. Jinhui Chen in conducting this search while he was a
postdoc at Kent State, along with more details about the role of other KSU faculty,
staff and students, please refer to the many news stories about this, some of which are
linked below. Dr. Chen has since left our group and has been appointed to a
tenured Assistant Scientist position in Shanghai.
News article in the journal Nature
Article by Institute of Physics (UK)
Story in Record Courier newspaper
Press Release by Kent State U
Story in campus newspaper
"Topflight international reverse-alchemy boffins" (we assume it's a compliment)
Official DOE-approved Press Release from Brookhaven National Lab
The original article in the journal Science (aimed at scientists only)
The story has been taken up by journalists and bloggers in many languages; here are some examples in
Congratulations to graduate student Tanya Ostapenko, who has been selected to
participate in the 2010 Lindau
Nobel Laureate Meeting in Germany, which offers a unique opportunity for PhD
candidates in the early-to-mid phase of their research to interact with the world's
A story in this month's issue of APS News (from the American Physical Society) looks back
over the "Top Ten
Physics Newsmakers of the Decade", and names the discovery of Quark Gluon Plasma as one
of these top ten. See our departmental announcements for 2005
and also for 2008 for particulars about the Kent State role
in this discovery.
You can also find archived news & announcements concerning past physics programs
and events from calendar years