Research Highlights
First Physics Results from the sPHENIX Particle Detector
The sPHENIX particle detector, the newest experiment at the Relativistic Heavy Ion Collider (RHIC) at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory, has released its first physics results: precision measurements of the number and energy density of thousands of particles streaming from collisions of near-light-speed gold ions. As described in two papers recently accepted for publication in Physical Review C and the Journal of High Energy Physics, these measurements lay the foundation for the detector’s detailed exploration of the quark-gluon plasma (QGP), a unique state of matter that existed just microseconds after the Big Bang some 14 billion years ago.
The new measurements reveal that the more head-on the nuclear smashups are, the more charged particles they produce and the more total energy those firework-like sprays of particles carry. That matches nicely with results from other detectors that have tracked QGP-generating collisions at RHIC since 2000, confirming that the new detector is performing as promised.
“As a new and highly sophisticated experiment that has gone through a decade of planning, construction, and commissioning, the first questions we need to ask are: Is the detector operating properly, is our calibration accurate, and are our data-processing pipelines reliable?” said Jin Huang, a physicist at Brookhaven Lab and co-spokesperson for the sPHENIX Collaboration. “The best way to do that is to go through measurements of the fundamental collision properties and confirm that the detector is measuring them properly.”
SBU Physics and Astronomy Faculty and Students Prepare to Measure the Universe
Stony Brook University professors — along with post-doctoral, graduate and undergraduate students — from the Department of Physics and Astronomy are preparing to measure the Universe with the newly constructed National Science Foundation (NSF)-Department of Energy (DOE) Vera C. Rubin Observatory in Chile.
Located on the El Peñón peak of Cerro Pachón in the Andes Mountains in Chile, the Rubin Observatory revealed the first set of large, ultra-high-definition images and videos on June 23, showcasing its extraordinary capabilities to the world for the first time at a “First Look Event” in Washington, D.C. Stony Brook researchers celebrated with their colleagues worldwide by hosting a “First Look Watch Party.”
“The known part of our Universe comprises only ~5% of the Universe,” said Chang Kee Jung, distinguished professor and chair of the Department of Physics and Astronomy in the College of Arts and Sciences. “The other part is composed of ‘Dark Energy’ and ‘Dark Matter,’ which we still know little about. The newly constructed Rubin Observatory will provide unprecedented data that will help us to greatly advance our understanding of the Universe. As a particle physicist myself, I have a keen interest in this magnificent telescope, not only for its fundamental science goals but also for its technology and participation of a large number of particle physicists in the project. The Stony Brook faculty members, postdocs and students have made significant contributions to the project. I am eager to see the stunning initial images and looking forward to seeing breakthrough findings from this interdisciplinary and mega-science project.”
NASA's Roman to Peer Into Cosmic 'Lenses' to Better Define Dark Matter
A funky effect Einstein predicted, known as gravitational lensing — when a foreground galaxy magnifies more distant galaxies behind it — will soon become common when NASA’s Nancy Grace Roman Space Telescope begins science operations in 2027 and produces vast surveys of the cosmos.
A particular subset of gravitational lenses, known as strong lenses, is the focus of a new paper published in the Astrophysical Journal coauthored by Simon Birrer, an assistant professor at Stony Brook University. The research team has calculated that over 160,000 gravitational lenses, including hundreds suitable for this study, are expected to pop up in Roman’s vast images. Each Roman image will be 200 times larger than infrared snapshots from NASA’s Hubble Space Telescope, and its upcoming “wealth” of lenses will vastly outpace the hundreds studied by Hubble to date.
Roman will conduct three core surveys, providing expansive views of the universe. This science team’s work is based on a previous version of Roman’s now fully defined High-Latitude Wide-Area Survey. The researchers are working on a follow-up paper that will align with the final survey’s specifications to fully support the research community.
Gravitational lenses are made up of at least two cosmic objects. In some cases, a single foreground galaxy has enough mass to act like a lens, magnifying a galaxy that is almost perfectly behind it. Light from the background galaxy curves around the foreground galaxy along more than one path, appearing in observations as warped arcs and crescents. Of the 160,000 lensed galaxies Roman may identify, the team expects to narrow that down to about 500 that are suitable for studying the structure of dark matter at scales smaller than those galaxies.
“Once Roman’s images are in hand, the researchers will combine them with complementary visible light images from Euclid, Rubin and Hubble to maximize what’s known about these galaxies,” Prof. Birrer said.
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