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Showing posts from July, 2023

A Pair of New Tetraquarks

  CERN’ s Large Hadron Collider has detected the signals of two new four-quark states that are unusual because of their charges and their quark compositions. In the protons and neutrons that make up everyday matter, all the hadrons are of the three-quark variety. But quarks can also assemble in larger numbers, showing up fleetingly in particle colliders in groups of four (see Synopsis: New Tetraquark Spotted in Electron-Positron Collisions) or five (see Synopsis: Pentaquark Discovery Confirmed). Now the Large Hadron Collider beauty (LHCb) Collaboration at CERN’s LHC has discovered two new four-quark particles. The quark compositions and charges of these tetraquarks make them good for testing theoretical models. The LHC recently began its third operational run, but this new result is drawn from data gathered during runs 1 and 2. The LHCb Collaboration analyzed detector tracks left by charged kaons and pions, which are the ultimate products of proton–proton collisions. From these tra...

ATLAS sets record precision on Higgs boson’s mass

  In the 11 years since its discovery at the Large Hadron Collider (LHC), the Higgs boson has become a central avenue for shedding light on the fundamental structure of the Universe. Precise measurements of the properties of this special particle are among the most powerful tools physicists have to test the Standard Model, currently the theory that best describes the world of particles and their interactions. At the Lepton Photon Conference this week, the ATLAS collaboration reported how it has measured the mass of the Higgs boson more precisely than ever before. The mass of the Higgs boson is not predicted by the Standard Model and must therefore be determined by experimental measurement. Its value governs the strengths of the interactions of the Higgs boson with the other elementary particles as well as with itself. A precise knowledge of this fundamental parameter is key to accurate theoretical calculations which, in turn, allow physicists to confront their measurements of the H...

Is the end of the 'particle era' of physics upon us?

  The discovery of the Higgs Boson in 2012 represented a major turning point for particle physics marking the completion of what is known as the standard model of particle physics. Yet, the standard model can't answer every question in physics, thus, since this discovery at the Large Hadron Collider (LHC) physicists have searched for physics beyond the standard model and to determine what shape future physics will take. A paper in The European Physical Journal H by Robert Harlander and Jean-Philippe Martinez of the Institute for Theoretical Particle Physics and Cosmology, RWTH Aachen University, Germany, and Gregor Schiemann from the Faculty of Humanities and Cultural Studies, Bergische Universität Wuppertal, Germany, considers the idea that particle physics may be on the verge of a new era of discovery and understanding in particle physics. The paper also considers the implications of the many possible scenarios for the future of high-energy physics. "Over the last century, t...

What does the Standard Model predict for the magnetic moment of the muon?

  image: The high-energy physics community is eagerly anticipating the announcement of the world’s best measurement from the Fermilab Muon g-2 experiment later this year, while the Muon g-2 Theory Initiative is working to shore up the predicted value using new data and new lattice calculations. Predicting the numerical value of the magnetic moment of the muon is one of the most challenging calculations in high-energy physics. Some physicists spend the bulk of their careers improving the calculation to greater precision. Why do physicists care about the magnetic properties of this particle? Because information from every particle and force is encoded in the numerical value of the muon’s magnetic moment. If we can both measure and predict this number to ultra-high precision, we can test whether the Standard Model of Elementary Particles is complete. Muons are identical to electrons except they are about 200 times more massive, are not stable, and disintegrate into electrons and neutr...

IceCube detects high-energy neutrinos from within the Milky Way

    High-energy neutrinos emerging from the Milky Way galaxy have been spotted for the first time. That is according to new findings from the  IceCube Neutrino Observatory  at the Amundsen–Scott South Pole Station that open a new avenue of multi-messenger astronomy by observing the Milky Way galaxy in particles rather than light. Neutrinos are fundamental particles that have very small masses and barely interact with other matter, but they fill the universe with trillions passing harmlessly through your body every second. Previously, neutrinos billions of times more energetic than those produced by fusion reactions within our Sun have been detected coming from extragalactic sources such as quasars. However, theory predicts that high-energy neutrinos should also be produced within the Milky Way. When astronomers look at the plane of our galaxy, they see the Milky Way lit up with gamma-ray emissions that are produced when cosmic rays trapped by our galaxy’s magnetic fi...