Nav: Home

Syracuse University physicist discovers new class of pentaquarks

March 26, 2019

SYRACUSE, N.Y. - Tomasz Skwarnicki, professor of physics in the College of Arts and Sciences at Syracuse University, has uncovered new information about a class of particles called pentaquarks. His findings could lead to a new understanding of the structure of matter in the universe.

Assisted by Liming Zhang, an associate professor at Tsinghua University in Beijing, Skwarnicki has analyzed data from the Large Hadron Collider beauty (LHCb) experiment at CERN's Large Hadron Collider (LHC) in Switzerland. The experimental physicist has uncovered evidence of three never-before-seen pentaquarks, each divided into two parts.

"Until now, we had thought that a pentaquark was made up of five elementary particles [called quarks], stuck together. Our findings prove otherwise," says Skwarnicki, a Fellow of the American Physical Society.

Skwarnicki is part of a team of researchers, including members of Syracuse's High-Energy Physics (HEP) Group, studying fundamental particles and forces in the Universe. Most of their work takes place at the CERN laboratory, whose LHC is the biggest, most powerful particle detector in the world.

It is within the LHC that protons are flung together at high energies, only to collide with one another. What lies inside the particles, when cracked open, helps scientists probe the mysteries of the fundamental universe.

Studying proton collisions from 2015-18, Skwarnicki has confirmed the existence of substructure within a pentaquark. The giveaway, he says, was a trio of narrow peaks in the LHC kinematic data.

Each peak refers to a particular pentaquark--specifically, one divided into two parts: a baryon, containing three quarks, and a meson, with two quarks.

A peak also suggests resonance, a short-lived phenomenon during particle decay, in which one unstable particle transforms into several others. Resonance happens when protons (a type of baryon) meet--or, more accurately, glide into one another--during an LHC collision.

What is unique about each of these three pentaquarks is that its mass is slightly lower than the sum of its parts--in this case, the masses of the baryon and meson. "The pentaquark didn't decay by its usual easy, fall-apart process," Skwarnicki says. "Instead, it decayed by slowly and laboriously rearranging its quarks, forming a narrow resonance."

Understanding how particles interact with and bind together is Skwarnicki's specialty. In 2015, he and then Ph.D. student Nathan Jurik G'16, Distinguished Professor Sheldon Stone and Zhang made headlines with their role in LHCb's detection of a pentaquark. Theorized a half century earlier, their discovery drew on LHC data from 2011-12.

LHCb's latest data utilized an energy beam that was nearly twice as strong. This method, combined with more refined data-selection criteria, produced a greater range of proton collisions.

"It also gave us 10 times more data and enabled us to observe pentaquark structures more clearly than before," Skwarnicki says. "What we thought was just one pentaquark turned out to be two narrow ones, with little space between them."

The data also revealed a third "companion" pentaquark. "All three pentaquarks had the same pattern--a baryon with a meson substructure. Their masses were below appropriate the baryon-meson thresholds," he adds.

Skwarnicki's discovery occurred relatively fast, considering that LHCb stopped collecting data less than three months ago.

Eric Sedore, associate CIO for infrastructure services in Information Technology Services (ITS), played a supporting role. His Research Computing Team provided the necessary computer firepower for Skwarnicki to achieve his goals.

In addition to Skwarnicki and Stone, HEP includes Professors Marina Artuso and Steven Blusk and Assistant Professor Matthew Rudolph. The group currently is building an apparatus on campus called the Upstream Tracker (UT), being shipped to and installed at CERN next year as part of a major LHCb upgrade.

"The UT will significantly enhance LHCb, which is composed of about 10 different sub-detectors. I am hopeful that the UT will lead to more discoveries," says Skwarnicki, adding that Artuso and Stone are the UT Project's leader and deputy, respectively.

Skwarnicki is excited about LHCb because it helps explain how the smallest constituents of matter behave. His latest discovery, for instance, proves that pentaquarks are built the same way as protons and neutrons, which are bound together in the nucleus of an atom.

"Pentaquarks may not play a significant role in the matter we are made of," he says, "but their existence may significantly affect our models of the matter found in other parts of the universe, such as neutron stars."
-end-
HEP's work is supported by the National Science Foundation.

Syracuse University

Related Large Hadron Collider Articles:

Near misses at Large Hadron Collider shed light on the onset of gluon-dominated protons
New findings from University of Kansas researchers center on work at the Large Hadron Collider to better understand the behavior of gluons.
Springer Nature publishes study for a CERN next generation circular collider
Back in January, CERN released a conceptual report outlining preliminary designs for a Future Circular Collider (FCC), which if built, would have the potential to be the most powerful particle collider the world over.
Large cells for tiny leaves
Scientists identify protein that controls leaf growth and shape.
NYU Physicists develop new techniques to enhance data analysis for large hadron collider
NYU physicists have created new techniques that deploy machine learning as a means to significantly improve data analysis for the Large Hadron Collider (LHC), the world's most powerful particle accelerator.
Mini antimatter accelerator could rival the likes of the Large Hadron Collider
Researchers have found a way to accelerate antimatter in a 1000x smaller space than current accelerators, boosting the science of exotic particles.
A domestic electron ion collider would unlock scientific mysteries of atomic nuclei
The science questions that could be answered by an electron ion collider (EIC) -- a very large-scale particle accelerator - are significant to advancing our understanding of the atomic nuclei that make up all visible matter in the universe, says a new report by the National Academies of Sciences, Engineering, and Medicine.
How large can a tsunami be in the Caribbean?
The 2004 Indian Ocean tsunami has researchers reevaluating whether a magnitude 9.0 megathrust earthquake and resulting tsunami might also be a likely risk for the Caribbean region, seismologists reported at the SSA 2018 Annual Meeting.
Meet the 'odderon': Large Hadron Collider experiment shows potential evidence of quasiparticle sought for decades
A team of high-energy experimental particle physicists, including several from the University of Kansas, has uncovered possible evidence of a subatomic quasiparticle dubbed an
The pros and cons of large ears
Researchers at Lund University in Sweden have compared how much energy bats use when flying, depending on whether they have large or small ears.
Scientists narrow down the search for dark photons using decade-old particle collider data
A fresh analysis of particle-collider data, co-led by Berkeley Lab physicists, limits some of the hiding places for one type of theorized particle -- the dark photon, also known as the heavy photon -- that was proposed to help explain the mystery of dark matter.
More Large Hadron Collider News and Large Hadron Collider Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

Risk
Why do we revere risk-takers, even when their actions terrify us? Why are some better at taking risks than others? This hour, TED speakers explore the alluring, dangerous, and calculated sides of risk. Guests include professional rock climber Alex Honnold, economist Mariana Mazzucato, psychology researcher Kashfia Rahman, structural engineer and bridge designer Ian Firth, and risk intelligence expert Dylan Evans.
Now Playing: Science for the People

#541 Wayfinding
These days when we want to know where we are or how to get where we want to go, most of us will pull out a smart phone with a built-in GPS and map app. Some of us old timers might still use an old school paper map from time to time. But we didn't always used to lean so heavily on maps and technology, and in some remote places of the world some people still navigate and wayfind their way without the aid of these tools... and in some cases do better without them. This week, host Rachelle Saunders...
Now Playing: Radiolab

Dolly Parton's America: Neon Moss
Today on Radiolab, we're bringing you the fourth episode of Jad's special series, Dolly Parton's America. In this episode, Jad goes back up the mountain to visit Dolly's actual Tennessee mountain home, where she tells stories about her first trips out of the holler. Back on the mountaintop, standing under the rain by the Little Pigeon River, the trip triggers memories of Jad's first visit to his father's childhood home, and opens the gateway to dizzying stories of music and migration. Support Radiolab today at Radiolab.org/donate.