From: ram@zedat.fu-berlin.de

Jan Panteltje  wrote or quoted:
>This rare phenomenon, known as light-on-light scattering, challenges the
classical idea
>that light waves pass through each other untouched.

  Generated by AI, read below:

  1.  About light-on-light scattering

  2.  What the Scientists in the report found out

  3.  Some terms explained for laymen

  4.  "2." explained for laymen


  1.  About light-on-light scattering

  The concept of light-by-light scattering - that is, photons
  interacting with each other indirectly through quantum
  effects - has been predicted by quantum electrodynamics (QED)
  since the 1930s. The theoretical foundation was laid soon after
  QED itself was developed in the late 1920s and early 1930s, with
  the understanding that photons can scatter off one another via
  virtual charged particles, even though classical electromagnetism
  says light beams pass through each other without interaction.

  However, the actual experimental observation of light-by-light
  scattering is extremely challenging due to the effect's
  tiny probability. It was only very recently - in 2017 - that the
  ATLAS and CMS experiments at the Large Hadron Collider (LHC)
  at CERN reported the first direct observation of elastic
  light-by-light scattering in ultraperipheral heavy-ion
  collisions, confirming the decades-old theoretical prediction


  2.  What the Scientists in the report found out

  The authors identify that tensor mesons (particles with spin-2)
  generate an infinite tower of excitations in holographic QCD,
  and their contributions have not been adequately included in
  previous calculations. Excitations of tensor mesons contribute
  specifically to the symmetric short-distance region, where
  all photon virtualities are large, thus directly addressing the
  noted deficit. Including these tensor meson towers can "fill
  the gap" left by the axial-vector sector

  Quantitative analysis demonstrates that tensor mesons chiefly
  contribute at low energies (photon virtualities below 1.5 GeV),
  with this positive contribution being significant. At intermediate
  ("mixed") energies, their effect is smaller, and at very high
  energies, it becomes negligible. When this component is included,
  it bridges the gap seen between the most recent dispersive
  calculations and lattice QCD results for the total hadronic
  light-by-light contribution to the muon's anomalous magnetic
  moment, potentially resolving a notable portion of the discrepancy


  3.  Some terms explained for laymen

  A meson is a type of subatomic particle made from one quark
  and one antiquark held together by the strong force. Mesons
  are strongly interacting particles, and they help hold
  together protons and neutrons inside atomic nuclei.

  Spin is a fundamental property of particles, similar to electric
  charge or mass. For elementary (and composite) particles, spin
  refers to a type of intrinsic angular momentum. It's measured in
  units of the reduced Planck constant. For example, photons have
  spin 1, electrons have spin 1/2, and tensor mesons have spin 2.

  Holographic QCD is a theoretical framework inspired by string
  theory that approaches the strong force (which binds quarks
  in protons, neutrons, and mesons) using ideas from gravity
  in higher-dimensional spaces. It often predicts many related
  particle "states" called a tower of excitations, much like
  a string that can vibrate at multiple frequencies.

  In quantum mechanics, "light-by-light scattering" refers to photons
  interacting with each other via virtual charged particles like
  mesons. This effect makes a tiny but important contribution to the
  muon's anomalous magnetic moment ("g-2") - an ultra-precise property
  of the muon that serves as a critical test of particle physics.

  In particle physics, a "virtual" photon is a photon that doesn't
  behave quite like ordinary light. It's a mathematical way to
  describe force-carrying particles in quantum field theory, and
  its "virtuality" means the amount by which its energy and
  momentum differ from what a real photon would have.


  4.  "2." explained for laymen

  When physicists use the holographic QCD approach, they not only
  get contributions from certain types of mesons (like axial-vector
  mesons), but also from a whole set - called an "infinite tower"
  - of tensor mesons, which are mesons with spin-2 (think of them
  as more complex cousins of particles like the pion). Previous
  calculations did not include the effects of all these tensor
  mesons. However, in situations where all the interacting photons
  are behaving very "off-shell" (meaning all have high virtuality),
  these tensor mesons start to matter a lot. Their collective
  contributions help to correct a shortfall that arises if you
  only consider the more basic meson types. By including this
  infinite series of tensor mesons, scientists can better match
  the calculations to what is expected from the fundamental QCD
  theory, "filling the gap" that was left in earlier models that
  considered only a finite set or just the axial-vector mesons.
  This improvement helps ensure that theoretical predictions for
  the muon's magnetic properties are more accurate and reliable.

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