New two-particle correlations observed in the CMS detector at the LHC

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Discussion Overview

The discussion revolves around the observation of new two-particle correlations in high multiplicity proton-proton events at the CMS detector at the LHC. Participants explore the implications of these observations, the physical origins, and the potential models that could explain the phenomena, with a focus on quantum mechanics and particle interactions.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants note that the physical origin of the observed correlations is not yet understood and suggest that further detailed study is necessary.
  • One participant raises the question of whether it is too early to rule out some models, indicating uncertainty in the interpretation of the results.
  • Another participant compares the new observations to the "near-side ridge" seen at RHIC, suggesting caution against assuming they are the same phenomenon.
  • There is a discussion about the relevance of different energy scales, with one participant questioning if the requirement for total transverse energy greater than 60 GeV indicates two relevant scales in the analysis.
  • Some participants argue that the presence of many tracks with relatively low transverse momentum does not necessarily imply that adding tracks from different collisions would yield similar results, as they could produce random backgrounds instead of signals.
  • One participant emphasizes that the correlations observed are within single events, which they argue is significant in the context of quantum mechanics.
  • A later reply introduces the idea that at least three jets may be necessary to observe correlations through color mechanisms, suggesting that the selection of many tracks enhances the likelihood of observing these jets.
  • Another participant points out that two-jet events must be back-to-back, which complicates the relevance of color arguments in certain regions of the event space.

Areas of Agreement / Disagreement

Participants express various viewpoints, with no consensus reached on the interpretation of the observations or the implications for existing models. There are competing ideas about the significance of the correlations and the mechanisms involved.

Contextual Notes

Participants highlight limitations in understanding the physical origins of the observations and the dependence on specific conditions, such as the requirement for high transverse energy and the nature of the tracks involved.

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However, the physical origin of our observation is not yet understood. Additional characteristics of the high multiplicity p p events displaying this novel feature deserve further detailed study.

Is it too early to rule out some models?
jal
 
The point of that remark, as I read it, was to keep everyone from assuming that this is just the same "near-side ridge" that was seen at RHIC a few years ago. Because that's what it looks like to me.
 
While the structure appears for intermediate trasversal momentum of about 3 GeV, it is also told that "At Level 1 (L1), the total transverse energy summed over the entire set of CMS calorimeters ... was required to be greater tan 60 GeV"

Does it mean that there are two relevant scales in the game?
 
I think it just means you have a lot of tracks, each with relatively little p_T.
 
daschaich said:
I think it just means you have a lot of tracks, each with relatively little p_T.

That was my first idea too, but then they should get the same result by just adding a lot of tracks from different colisions. So either they need a lot of *simultaneus* tracks to get some quantum interference in action, or they need really an object above 60 GeV.
 
arivero said:
they should get the same result by just adding a lot of tracks from different colisions
Why do you say that ? Adding particle tracks from different events will just reproduce random backgrounds (like accidentals), not signals.
arivero said:
So either they need a lot of *simultaneus* tracks to get some quantum interference in action, or they need really an object above 60 GeV.
Those correlations are seen in very high multiplicity events (~100 tracks) indeed.
 
arivero said:
That was my first idea too, but then they should get the same result by just adding a lot of tracks from different colisions.

Why do you say that? I see no reason that correlations within a single collision imply any correlation at all between separate collisions.

arivero said:
they need a lot of *simultaneus* tracks

These tracks are all in single events... I don't know how much more simultaneous you can get.

Edit to add: Scooped!
 
Last edited:
  • #10
Hmm, are you lads following the conversation from #5, or just answering the last post without correlatiing (pun intended) it with the previous ones? If the former, then it is my English... I was telling that it is not "just a lot of tracks", it is "a lot of tracks coming from a single event", which is a different beast in quantum mechanics. I think that the observation is so elementary that you both have thought that I was arguing something, when I was simply being pedantic about the use of "just a".

A poster at Dorigo's has given a pausible explanation: they need at least 3 jets to get correlations via mechanisms based in colour, and then the selection of having a lot of tracks enhances the selection of 3-jets.
 
  • #11
arivero said:
Hmm, are you lads following the conversation from #5
No, and please note that there was not much discussion before #5
arivero said:
A poster at Dorigo's has given a pausible explanation: they need at least 3 jets to get correlations via mechanisms based in colour, and then the selection of having a lot of tracks enhances the selection of 3-jets.
Please note that a two jet event must be back to back, so can not be in the region \Delta\phi\sim0 with large \Delta\eta whether the color argument is relevant or not.
 

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