ATLAS reanalysis of W mass: Lower uncertainty, agrees with SM

In summary, the recent ATLAS result on the W boson has been improved with better analysis methods and new results from elsewhere. The primary difference is improvements in the event generation, particularly in obtaining the mass of W. As time passes, some of the models and inputs used for this measurement become outdated and are replaced with newer ones. This is a complex process that requires a lot of tuning and adjustment. Pythia, a commonly used event generator, may not be accurate enough for this measurement.
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ATLAS reduced the systematic uncertainties of its measurement. This puts the CDF measurement in even stronger disagreement with other experiments.
Improved ATLAS result weighs in on the W boson
Same dataset, but better analysis methods and some new results from elsewhere that could be used. Money plot from ATLAS:

ATLAS-Plot_Overview_WMass%20%281%29.png


This makes the CDF measurement an even weirder outlier than it was at the time of publication.
 
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The primary difference is improvements in the event generation. It makes one wonder if there are similar improvements to be made at Tevatron energies.
 
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Vanadium 50 said:
The primary difference is improvements in the event generation
What are the improvements?
 
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Without getting too technical, what you want is m(W). What you have is m(l + v) and you're missing the z-component of the neutrino. It takes some modeling to get from one to the other and those models contain inputs like proton structure.

As time passes, some of these models (or inputs) are disfavored by the data and new ones are created to take their place.
 
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I have used pythia a lot.

Is it just the event generation of W -> l + v that has been improved or what else have they done?

If you have any technical references, I would be happy to read them
 
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Pythia (at leas Pythia 6 out of the box) won't come close. The PDFs are ancient, the underlying event isn't right, and it won't get radiation of the lepton right.

This is kind of a part in 10,000 measurement. Takes lots of tuning and adjustment to get everything right.
 
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Yeah I have also used Pythia with various pdfs. I guess I have to look more into the newest version of PHOTOS
 

1. What is the ATLAS reanalysis of W mass?

The ATLAS reanalysis of W mass is a scientific study conducted by the ATLAS collaboration at the Large Hadron Collider (LHC) in Geneva, Switzerland. It involves analyzing data from proton-proton collisions to determine the mass of the W boson, a fundamental particle that is responsible for the weak nuclear force.

2. How does this reanalysis lower the uncertainty of the W mass?

The ATLAS reanalysis uses improved measurement techniques and more data compared to previous studies, resulting in a more precise determination of the W mass. This lower uncertainty means that the measured value is closer to the true value of the W mass.

3. What is the Standard Model (SM) and why is it significant that the reanalysis agrees with it?

The Standard Model is a theory that describes the fundamental particles and forces that make up the universe. It has been extensively tested and is considered to be the most accurate description of the subatomic world. The fact that the ATLAS reanalysis agrees with the predicted W mass in the Standard Model provides further evidence for the validity of this theory.

4. What are the potential implications of this reanalysis?

The ATLAS reanalysis has important implications for our understanding of the fundamental particles and forces in the universe. It provides a more precise measurement of the W mass, which can be used to test and refine existing theories and potentially reveal new physics beyond the Standard Model.

5. How does the ATLAS reanalysis contribute to our overall understanding of particle physics?

The ATLAS reanalysis is a significant contribution to the field of particle physics as it provides a more accurate measurement of a fundamental particle. This information can be used to further our understanding of the building blocks of the universe and potentially uncover new physics that may lie beyond our current understanding.

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