# Revisiting the ALEPH Archived e+e- Data at LEP: Challenges, Lessons and Recent Results on an Intriguing Structure in Long Range Correlations in High Multiplicity e+e- Collisions at 91-209 GeV

- Institution: CERN
- Department: EP Seminar
- Speaker: Yi Chen
- Year: 2024
- Language: English
- Source: [CERN](https://videos.cern.ch/record/3008382)
- Licence: [CERN](http://copyright.web.cern.ch)
- Who can watch: Teens profiles and older (sources give no ratings; placed by Invisible Network from the source's own words)

We present measurements of two-particle angular correlations of charged particles emitted in high-energy e+e- collisions using data collected by the ALEPH detector at LEP between 1992 and 2000, pushing the studies of long-range correlation to the smallest collision system limit. We will discuss the effort to reanalyze the archived ALEPH data, including the challenges we faced and lessons learned that give some insights on data preservation for current ongoing experiments.

The recent two particle correlation measurement probes the dependence on charged-particle multiplicity. Higher collision energy LEP2 data allows access to higher event multiplicity and additional production channels beyond the e+e- -> Z -> qq process probed by the LEP1 data at 91 GeV, which shows no significant excess long-range correlations. The highest multiplicity bin suggests an intriguing deviation from archived MC and implies the potential to search for collective phenomena in small systems. It includes the first flow coefficient measurement and a Fourier decomposition analysis in e+e- collisions to quantify the anisotropy in the azimuthal two-particle correlation as a function of charged particles' transverse momentum. This work supplements our understanding of small-system references to long-range correlations observed in proton-proton, proton-nucleus, and nucleus-nucleus collisions.

Refreshments will be served at 09:30. .

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## Lectures

1. [Revisiting the ALEPH Archived e+e- Data at LEP: Challenges, Lessons and Recent Results on an Intriguing Structure in Long Range Correlations in High Multiplicity e+e- Collisions at 91-209 GeV](https://invisiblenetwork.ai/learn/cern/3008382/5e7536eef164), 57 min (CERN's player)