Researchers have recently made new discoveries about exotic subatomic particles and the strong force. Their work uses computational methods to predict the existence of a novel tetraquark, made up of beauty and charm quarks and two light antiquarks. This discovery expands our understanding of quantum chromodynamics and the composition of visible matter. Source: SciTechDaily.com
A new study reveals the existence of a tetraquark composed of beauty and charm quarks, expanding our knowledge of the physics of subatomic particles and strong force interactions.
Scientists from the Institute of Mathematical Science (IMSc) and the Tata Institute of Fundamental Research (TIFR) exploring the complex field of subatomic particles have recently published a new discovery in the journal Physical Examination LettersTheir study opens a new horizon within quantum chromodynamics (QCD), sheds light on exotic subatomic particles and extends the boundaries of our understanding of the strong force.
Schematic representation of the predicted tetraquark Tbc, consisting of four quarks: beauty quarks, charm quarks and two light antiquarks. Image credit: Nilmani Mathur
The mysterious strong force and the world of hadrons
At the heart of this investigation is the enigmatic fundamental strong force that generates almost all the mass of all visible matter in the universe. A handful of elementary particles known as quarks, which undergo fascinating interactions by exchanging gluons, generate all the composite subatomic particles that eventually make up all the visible matter of our universe.
Central to this understanding is the theory of quantum chromodynamics (QCD), which governs the dynamics of strong interactions. QCD enables the formation of color-neutral combinations of quarks into subatomic particles, commonly referred to as hadrons.
Traditionally, hadrons are divided into two main categories: mesons, like pions, which consist of one quark and one antiquark, and baryons, like protons, which consist of three quarks. Outside these categories, however, there are exotic hadrons, including those with four, five, or six quarks, and even particles with gluons, like glueballs.
Until relatively recently, however, the existence of these exotic hadrons was largely uncharted territory for particle physicists. Over the past decade and a half, a flood of experimental discoveries has illuminated this previously unknown territory, revealing a rich spectrum of exotic hadrons that contradict conventional ideas about the strong force and challenge our understanding of subatomic particles.
Schematic representation of the formation of Tbc by interactions of a bottom and a charm meson. Image credit: A. Radhakrishnan and V. Raj
Discovery of tetraquarks: A new frontier in particle physics
These exotic hadrons include tetraquarks, which consist of four quarks (more precisely, two quarks and two antiquarks). They could exist in highly compact form or as loosely bound molecules made of two mesons or something else: their exact structure remains a mystery. They are among the most common exotic hadrons and many more are expected to be discovered in the future. Theoretical studies can help in the discovery of these hadrons by predicting their quark content and possible energy ranges.
In this recent work, Prof. Nilmani Mathur and a postdoctoral fellow, Dr. Archana Radhakrishnan, from the Institute of Theoretical Physics at TIFR and Dr. M. Padmanath from IMSc have predicted the existence of a new tetraquark. This new subatomic particle consists of a beauty and a charm quark and two light antiquarks and belongs to a family of tetraquarks called Tv. Chr.: The beautiful-enchanting tetraquarks.
They have used the computing power of the Indian Lattice Gauge Theory Initiative (ILGTI) to perform this calculation. The formation of this particular tetraquark was studied using the interactions between a bottom and a charm meson. Using variational techniques over different lattice spacings and valence light quark masses, this study examined the energy eigenvalues of the interacting meson systems within confined volumes and concluded that this tetraquark exists. Similar to the predicted particle, there could be other tetraquarks with the same quark content but different spin and parity.
This prediction comes at an opportune time, coinciding with the recent discovery of a tetraquark (Tcc), which consists of two charm quarks and two light antiquarks. Consequently, there is a possibility that the newly predicted particle, or a related variant, could be discovered using similar experimental methods as the energy range and luminosity required for their creation and detection become increasingly accessible.
Furthermore, the binding energy of the predicted particle exceeds that of all tetraquarks discovered so far, and the binding weakens as the mass of the light quark increases. This suggests the complex dynamics of strong interactions in different quark mass ranges and explains the intriguing features of the strong interaction in the formation of hadrons, especially those with heavy quarks.
This also provides additional motivation to search for heavier exotic subatomic particles in next-generation experiments that could be used to decipher the strong force and unlock its full potential.
Reference: “Bound Isoscalar Axial-Vector 𝑏𝑐𝑢¯𝑑¯ Tetraquark 𝑇𝑏𝑐 from Lattice QCD Using Two-Meson and Diquark-Antidiquark Variational Basis” by M. Padmanath, Archana Radhakrishnan and Nilmani Mathur, 14 May 2024, Physical Examination Letters.
DOI: 10.1103/PhysRevLett.132.201902