Forward-Backward Multiplicity Correlations for Proton-Proton Collisions with ALICE at LHC-CERN
(2022) FYSK02 20221Particle and nuclear physics
Department of Physics
- Abstract
- This thesis presents the study of two-particle pseudorapidity correlations in pp-collisions at √s = 13 TeV using the ALICE detector at LHC, CERN. The correlation function was calculated as a function of multiplicity and was repeated for several multiplicity classes and different charge combinations in the forward-backward and central regions of the detector, respectively. The results reveal an enhancement of particle pairs being emitted in the same direction and strong autocorrelations using the mid-multiplicity estimator at low multiplicities. Comparing the results with PYTHIA simulations, similar results are obtained for both multiplicity estimators. This reveals that PYTHIA simulations are able to accurately reproduce these results,... (More)
- This thesis presents the study of two-particle pseudorapidity correlations in pp-collisions at √s = 13 TeV using the ALICE detector at LHC, CERN. The correlation function was calculated as a function of multiplicity and was repeated for several multiplicity classes and different charge combinations in the forward-backward and central regions of the detector, respectively. The results reveal an enhancement of particle pairs being emitted in the same direction and strong autocorrelations using the mid-multiplicity estimator at low multiplicities. Comparing the results with PYTHIA simulations, similar results are obtained for both multiplicity estimators. This reveals that PYTHIA simulations are able to accurately reproduce these results, notably, also the autocorrelations are reproduced. (Less)
- Popular Abstract
- Despite the universe being so vast, it seems as its secrets lie hidden in the smallest objects yet known, so naturally, we smash them together.
Imagine smashing two watermelons together at high speed, what we’d expect is for the melons to explode and shoot out their insides all over the place. Similarly, when colliding protons together many particles are produced in the explosion that will be shot off everywhere. Now, if one were to record exactly where all parts of the watermelon had landed it would not be too difficult to figure out where the two watermelons were and how they traveled before the collision. However, when colliding protons this is not as easy.
Trying to figure out what and where the protons were during the collision... (More) - Despite the universe being so vast, it seems as its secrets lie hidden in the smallest objects yet known, so naturally, we smash them together.
Imagine smashing two watermelons together at high speed, what we’d expect is for the melons to explode and shoot out their insides all over the place. Similarly, when colliding protons together many particles are produced in the explosion that will be shot off everywhere. Now, if one were to record exactly where all parts of the watermelon had landed it would not be too difficult to figure out where the two watermelons were and how they traveled before the collision. However, when colliding protons this is not as easy.
Trying to figure out what and where the protons were during the collision is similar to a detective’s work. Putting together the clues to figure out how the crime was committed, here becomes: trying to determine what happened during the collision using the fact that we know where produced particles flew off. There are different theories of what happens when smashing protons together. Some experiments indicate that such high energies are reached during these collisions that for an extremely short time, an entirely different phase of matter is produced. This phase is believed to have existed for the very first moments of the universe after the Big Bang.
To further improve the detective’s work, of understanding what happens when smashing protons together, one can test the models used to simulate these events. In contrast to the watermelon case, the matter in particle collisions is not conserved because additional matter can be created from the kinetic energy according to Einstein’s famous formula E=mc^2. This means that it is necessary to have models describing both the matter produced from the kinetic energy and directly from the protons. One of the most successful models in the latter is the Lund string model. Finding limitations in this model will help us understand where our understanding fails us and may point us in the direction to find even better models.
One way of testing these models is by studying “multiplicity correlations”. This reveals in what direction most pairs of particles are produced after a collision and is particularly sensitive to correlations between particles produced together, e.g., from the same Lund string. This makes it possible to learn about the number of strings formed and their length.
Verifying if models are true will either lead to better future models or validation of the accuracy of the current ones. This can in turn improve many aspects of particle physics, one of which is to improve our understanding of what happened at the big bang and how the universe we know today came to be. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9081656
- author
- Koppers, August LU
- supervisor
- organization
- course
- FYSK02 20221
- year
- 2022
- type
- M2 - Bachelor Degree
- subject
- keywords
- ALICE, Particle physics, CERN, LHC, QCD, pp collisions, Lund string model, Two particle correlation
- language
- English
- id
- 9081656
- date added to LUP
- 2022-05-30 10:44:35
- date last changed
- 2022-05-30 10:44:35
@misc{9081656,
abstract = {{This thesis presents the study of two-particle pseudorapidity correlations in pp-collisions at √s = 13 TeV using the ALICE detector at LHC, CERN. The correlation function was calculated as a function of multiplicity and was repeated for several multiplicity classes and different charge combinations in the forward-backward and central regions of the detector, respectively. The results reveal an enhancement of particle pairs being emitted in the same direction and strong autocorrelations using the mid-multiplicity estimator at low multiplicities. Comparing the results with PYTHIA simulations, similar results are obtained for both multiplicity estimators. This reveals that PYTHIA simulations are able to accurately reproduce these results, notably, also the autocorrelations are reproduced.}},
author = {{Koppers, August}},
language = {{eng}},
note = {{Student Paper}},
title = {{Forward-Backward Multiplicity Correlations for Proton-Proton Collisions with ALICE at LHC-CERN}},
year = {{2022}},
}