Why Does the J/psi Meson Detection Show Large Standard Deviation in CMS Graphs?

Click For Summary
SUMMARY

The discussion centers on the unexpected large standard deviation of 52±3 observed in the CMS graphs for J/psi meson detection, contrasting with the expected width of 0.08 MeV derived from the energy-time uncertainty principle (ΔEΔt≈h). The discrepancy arises from the complexities of particle detection and measurement, which differ significantly from straightforward length measurements. Participants highlight that the shape of the distribution also deviates from expectations, indicating multiple factors influencing the results.

PREREQUISITES
  • Understanding of the energy-time uncertainty principle (ΔEΔt≈h)
  • Familiarity with particle physics and meson detection techniques
  • Knowledge of statistical analysis in experimental physics
  • Experience with interpreting histograms and standard deviation in data sets
NEXT STEPS
  • Research the principles of particle detection in high-energy physics experiments
  • Study the implications of the energy-time uncertainty principle on measurement accuracy
  • Explore statistical methods for analyzing experimental data in physics
  • Investigate the characteristics of J/psi meson decay and its significance in particle physics
USEFUL FOR

Students and researchers in particle physics, experimental physicists analyzing meson detection, and anyone interested in understanding the complexities of measurement in high-energy experiments.

MoAli
Messages
12
Reaction score
0

Homework Statement


See Image
The bit about Spectral lines, I couldn't explain why[/B]

Homework Equations


ΔEΔt≈h

The Attempt at a Solution


I expected the histogram to peak at the given mass in question and to have a width of about 0.08 MeV calculated as ΔE from the Energy-time uncertainty, but I don't understand how the standard deviation is 52±3 in the CMS graph, this is so far away from my calculation, plus, is this the only difference? I would also suspect that i misunderstood the question maybe. I haven't dealt with such graphs before!
 

Attachments

  • Screen Shot 2016-12-11 at 14.54.56.png
    Screen Shot 2016-12-11 at 14.54.56.png
    95.5 KB · Views: 587
Physics news on Phys.org
If you measure the length of something that is exactly 1.381352413243543 meters long with a ruler, do you expect a result of 1.381352413243543 meters? What would actually happen?

The same happens in the CMS measurement, just for different reasons because it is not a length measurement.

The larger width is not the only difference, the shape looks different as well, and there are at least two things you can find (although I'm not sure if the teacher expects those).