What does a QCD background refer to?

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In summary, the conversation is about the Higgs Boson and the "high QCD background" mentioned in research papers. The speaker is looking for clarification on the definition of this term and its relevance in proton-proton collisions at the LHC. The background refers to strong interaction events that need to be subtracted to isolate the electro-weak Higgs signal. This is not an issue in electron-positron colliders. The term is colloquially used but not allowed in published work, and generally refers to processes that produce hadronic jets in the final state. These jets can be mistaken for other particles and their frequency is taken into consideration in background calculations.
  • #1
martinhiggs
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Hi!

I'm currently performing lots of research into the Higgs Boson. In many papers, when talking specifically about production and decay mechanisms, they talk about the "high QCD background". I can't find a specific definition for what this means and refers to.

Any clarification would be appreciated :)
 
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  • #2
I guess you are interested in proton-proton collision at the LHC.

The Higgs boson is produced via electro-weak processes, but almost all events that are detected are due to the strong interaction. Therefore all these events are "background" and have to be subtracted to get the electro-weak Higgs signal.

There would be no such problem with an electron-positron collider b/c no strong interacting particles are present.
 
  • #3
In experimental terms, it's a bit of a bastardised term (CMS publication guidelines are explicit in not allowing it, along with other phrases such as 'more statistics' - we use these colloquially, but they shouldn't be in our published work).

What it generally refers to are processes which lead to two hadronic jets in the final state. These can fake things such as electrons, and their cross section is very high. We spend a lot of our time quantifying the probability of a jet to fake a certain physics object, and take this into account in our background computations.
 

1. What is QCD background?

QCD background refers to the background noise or signal that is generated in a particle physics experiment due to quantum chromodynamics (QCD), which is the theory that describes the strong interaction between quarks and gluons.

2. How does QCD contribute to background in particle physics experiments?

QCD contributes to background in particle physics experiments because it is a fundamental force that is present in all interactions involving quarks and gluons. This means that any particle interactions involving these particles will also produce background noise or signal.

3. Can QCD background be eliminated in particle physics experiments?

No, it is not possible to completely eliminate QCD background in particle physics experiments. However, scientists use various techniques and analysis methods to reduce its impact and distinguish it from potential new particles or phenomena that they are studying.

4. How do scientists account for QCD background in their research?

Scientists use simulations and theoretical calculations based on QCD to model and predict the expected levels of background in their experiments. They also compare their experimental data to these predictions to identify any discrepancies that may indicate the presence of new particles or phenomena.

5. Is QCD background a hindrance to scientific discoveries?

No, QCD background is not a hindrance to scientific discoveries. In fact, it is an important aspect of particle physics research as it helps scientists better understand and study the strong interaction and its effects on particle interactions. By accounting for and understanding QCD background, scientists are able to make more accurate and meaningful interpretations of their experimental data.

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