Note4Students
From UPSC perspective, the following things are important :
Prelims level: Higgs Boson Decay
Mains level: Read the attached story
Central Idea
- Physicists at CERN’s Large Hadron Collider (LHC) reported detecting a rare decay of the Higgs boson into a Z boson and a photon.
- The decay process provides valuable insights into the Higgs boson and the nature of our universe.
Large Hadron Collider (LHC) |
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| What is it? | – The LHC is the world’s largest science experiment constructed by CERN.
– It collides beams of hadrons, such as protons, for high-energy physics research. – Upgrades have enhanced the LHC’s sensitivity and accuracy for its third season of operations. |
| Functioning | – Protons are accelerated through a 27 km circular pipe using powerful magnets.
– Magnetic fields guide the protons, reaching speeds close to the speed of light. |
| Particle Collisions | – Collisions of high-energy protons lead to the creation of various subatomic particles.
– The LHC has achieved collision energies of up to 13.6 TeV. |
| Scientific Discoveries at the LHC | – LHC’s detectors, including ATLAS and CMS, discovered the Higgs boson in 2012.
– Scientists have tested predictions of the Standard Model, observed exotic particles, and gained insights into extreme conditions. |
| Future of the LHC | – Upgrades are planned to increase the LHC’s luminosity by ten times by 2027, aiming to discover new physics.
– There is a debate about investing in a larger LHC or smaller experiments to explore new realms of physics. |
Understanding the Higgs Boson
- The Higgs boson is a type of subatomic particle that carries the force of particle movement through the Higgs field, present throughout the universe.
- Interaction with Higgs bosons determines a particle’s mass, with stronger interaction leading to greater mass.
Importance of Higgs Boson Decay
- Studying how different particles interact with Higgs bosons and understanding the properties of Higgs bosons helps reveal information about the universe.
- The recent detection of Higgs boson decay to a Z boson and a photon provides noteworthy insights.
Role of Virtual Particles
- Quantum field theory suggests that space at the subatomic level is filled with virtual particles that constantly appear and disappear.
- Higgs bosons interact fleetingly with virtual particles during their creation, resulting in the production of a Z boson and a photon.
New Result and Probability
- The Standard Model predicts that the Higgs boson will decay into a Z boson and a photon 0.1% of the time.
- The LHC needed to produce a significant number of Higgs bosons to observe this decay pathway.
Confirmation and Statistical Precision
- The ATLAS and CMS detectors, which previously observed the decay independently, combined their data for increased statistical precision.
- Although the significance is not yet 100%, the combined data enhanced the confirmation of the Higgs boson decay.
Significance for the Standard Model
- Physicists seek to detect and validate the predicted decay pathways of the Higgs boson according to the Standard Model.
- Precise testing of the model’s predictions helps identify potential deviations and explore new theories in physics.
Implications for New Theories
- Higher decay rates through the observed pathway could support new theories beyond the Standard Model.
- Experimental evidence from the LHC could contribute to advancements in scientific understanding.
Back2Basics: Standard Model
- The Standard Model is a theoretical framework in physics that describes the fundamental particles and their interactions, except for gravity.
- It provides a comprehensive understanding of three of the four fundamental forces: electromagnetic, strong nuclear, and weak nuclear forces.
- Developed in the mid-20th century, the Standard Model has been highly successful in explaining and predicting the behaviour of elementary particles.
Key points about the Standard Model:
- Particle Classification: The Standard Model classifies particles into two main categories: fermions and bosons.
- Fermions: Fermions are particles that make up matter. They are further categorized into quarks and leptons. Quarks are the building blocks of protons and neutrons, while leptons include electrons and neutrinos.
- Bosons: Bosons are force-carrying particles responsible for transmitting the fundamental forces. Examples include photons (electromagnetic force), gluons (strong nuclear force), and W and Z bosons (weak nuclear force).
- Fundamental Forces: The Standard Model explains the interactions between particles through the following fundamental forces:
- Electromagnetic Force: Mediated by photons, this force governs the interactions between charged particles.
- Strong Nuclear Force: Mediated by gluons, it binds quarks together to form protons, neutrons, and other particles.
- Weak Nuclear Force: Mediated by W and Z bosons, it is responsible for certain types of radioactive decay.
- Higgs Field and Higgs Boson: The Standard Model introduces the concept of the Higgs field, an energy field that permeates the universe. Particles acquire mass through their interaction with this field. The existence of the Higgs boson, a particle associated with the Higgs field, was confirmed in experiments at the Large Hadron Collider (LHC) in 2012.
Limitations and Open Questions:
While the Standard Model has been highly successful in describing particle interactions, it has some limitations:
- Gravity: The theory does not include a description of gravity, which is described by general relativity. Combining gravity with the other forces remains a challenge.
- Dark Matter and Dark Energy: The Standard Model does not account for dark matter and dark energy, which are believed to constitute a significant portion of the universe.
- Unification: The theory does not provide a unified description of all forces, including electromagnetism, weak nuclear force, and strong nuclear force.
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