W Boson [UPSC Notes]

Recalculation of W boson mass increases tension between competing particle collider experiments. W boson and the large hadron collider experiments at CERN are important topics for the IAS exam science and technology segment. This article describes what W bosons are and what is the latest development in this field.

W Boson

The W boson is an elementary particle responsible for the weak force, which is one of the three fundamental forces in the standard model of particle physics.

• The W boson is the only particle mass in the standard model that can be calculated, and its mass is an essential test of the standard model theory.
• The standard model theory predicts a specific mass for the W boson, unlike other particles such as electrons and quarks, whose masses are inputs and can have any value.

What does a W boson do?

The W boson is a fundamental particle. Together with the Z boson, it is responsible for the weak force, one of four fundamental forces that govern the behaviour of matter in our universe. Particles of matter can interact by exchanging these bosons, but only over short distances.

Who discovered the W boson?

The W boson’s discovery was the result of an idea proposed in 1976 by Carlo Rubbia, Peter McIntyre and David Cline.

Large Hadron Collider’s ATLAS experiment outcome on W Boson: 

• The ATLAS experiment is a particle detector at the Large Hadron Collider (LHC) in CERN, Geneva.
• It has conducted measurements related to the mass of an elementary particle called the W boson.
• A recent reanalysis of old data from the ATLAS experiment has yielded a W boson mass of about 80,360 MeV, which is in alignment with predictions from the standard model.
• This measurement has reduced uncertainty from the researchers’ previous analysis in 2018, increasing their confidence in the result.

New results and their impact: 

• The revised value is in contrast with the measurement of the same particle by the Collider Detector at Fermilab (CDF) experiment, which reported a mass of 80,434 MeV in 2022, about 100 MeV heavier than expected.
• The discrepancy between the ATLAS and CDF measurements could have implications for the standard model, which describes the fundamental forces and quantum bits that make up everything we see in the cosmos.
• If the CDF result is correct, it implies that something is off with the standard model, which has persisted in the face of every experimental challenge thrown at it over the last 50 years.
• The ATLAS reanalysis widens the gap between the CDF measurement and other studies.

Conclusion: New results from the Large Hadron Collider’s ATLAS experiment on the mass of the W boson have increased the tension between measurements from competing particle collider experiments. This could either bolster the standard model of particle physics or reveal signs of its breakdown, depending on which lab’s answer prevails. Further studies and analysis are needed to resolve the discrepancy.

W Boson [UPSC Notes] :- Download PDF Here