Discovery of the Xi-cc-plus Baryon at CERN

Discovery of the Xi-cc-plus Baryon at CERN

The LHCb experiment at CERN's Large Hadron Collider (LHC) has announced the discovery of a new particle—the Xi-cc-plus—a heavy baryon that will help physicists better understand how the strong force binds together protons, neutrons, and other composite particles.

Key Points

¨     The Xi-cc-plus Particle: The Xi-cc-plus consists of two charm quarks and one down quark, making it a heavier cousin of the proton (which contains two up quarks and one down quark).

¨     It was produced by colliding high-energy protons within the Large Hadron Collider (LHC). Like most hadrons, it is an unstable particle that decays rapidly.

¨     This is the first new particle discovered following the 2023 upgrade of the LHCb detector, bringing the total number of hadrons discovered by LHC experiments to 80.

¨   Physical Properties: Due to the presence of two heavy charm quarks, this particle is approximately four times heavier than a proton and has a significantly shorter lifetime compared to its counterparts.

¨    Rare Discovery: This marks the second time a baryon containing two heavy quarks has been observed. A similar particle—comprising two charm quarks and one up quark—was previously discovered by LHCb in 2017.

¨ Scientific Significance:This discovery helps theorists test models of Quantum Chromodynamics (QCD), which involves the strong force—the force that binds quarks together into hadrons (mesons and baryons). It opens the door to the study of exotic hadrons, such as tetraquarks and pentaquarks, thereby setting the stage for future research at the High-Luminosity LHC. QCD serves as the theoretical framework in particle physics; it describes the strong nuclear force, one of the four fundamental forces of nature. It explains how quarks and gluons interact to form composite particles such as protons, neutrons, and mesons.

The Large Hadron Collider (LHC)

¨  The Large Hadron Collider (LHC) is the world's largest and most powerful particle accelerator, located at CERN near Geneva. It accelerates particles—such as protons—to nearly the speed of light, directing them into two high-energy beams traveling in opposite directions.

¨   These beams are then made to collide at four specific points around the ring, where massive detectors (such as ATLAS, CMS, and LHCb) record the resulting "subatomic debris."

Key Terms

¨     Baryon: A baryon is a type of composite subatomic particle composed of three quarks held together by the strong nuclear force. Together with mesons—which consist of one quark and one antiquark—baryons form part of the broader family of particles known as hadrons.

¨     Quark: Quarks are fundamental particles and constitute the basic building blocks of matter. They possess a fractional electric charge, which can be either +2/3 or -1/3.

¨  Antiquark: Every quark has a corresponding antiparticle, known as an antiquark. An antiquark possesses the same mass as its quark counterpart, but carries opposite physical charges. For example, if a charm quark has a charge of +2/3, its charm antiquark will have a charge of -2/3. If a quark is "blue," its antiquark will be "anti-blue."