Projections for charm balance functions in heavy-ion collisions
(2022) FYSK02 20221Particle and nuclear physics
Department of Physics
- Abstract
- In this thesis, pp collisions were simulated using PYTHIA. D+ D- and D0 D0bar balance functions were created in order to contribute with a reference point for future balance functions measured in real data from Pb-Pb collisions. Charm balance functions are important since the charm quark can act as a probe of the QGP, probing the first instances after a collision. The balance functions were created under varying conditions: (i) minimum bias with only events with 2 charms, (ii) forcing charm production and (iii) forcing charm production with only events with 4 charms.
The results were mainly in line with expectations. The main deviation from expectations was that no away-side peak was found in minimum bias collisions, indicating that the... (More) - In this thesis, pp collisions were simulated using PYTHIA. D+ D- and D0 D0bar balance functions were created in order to contribute with a reference point for future balance functions measured in real data from Pb-Pb collisions. Charm balance functions are important since the charm quark can act as a probe of the QGP, probing the first instances after a collision. The balance functions were created under varying conditions: (i) minimum bias with only events with 2 charms, (ii) forcing charm production and (iii) forcing charm production with only events with 4 charms.
The results were mainly in line with expectations. The main deviation from expectations was that no away-side peak was found in minimum bias collisions, indicating that the distributions are dominated by NLO processes. This was not in line with real data from pp collisions from LHCb. (Less) - Popular Abstract
- The first milliseconds after the big bang the universe consisted of what is called the quark-gluon plasma (QGP for short). This is a state of matter just like solid, liquid and gas.
You may recall that the atomic nucleus consists of protons and neutrons. However, it does not stop there: these protons and neutrons in turn consist of particles called quarks. These are the smallest constituents of the universe, and they are bound together by something called gluons (as they act as the glue holding the quarks together). Hadrons is the general name of particles that consist of quarks: protons, neutrons, kaons, pions, etc. Quarks can be seen as the lego pieces forming the hadrons, and the gluons would then be the studs keeping the lego pieces... (More) - The first milliseconds after the big bang the universe consisted of what is called the quark-gluon plasma (QGP for short). This is a state of matter just like solid, liquid and gas.
You may recall that the atomic nucleus consists of protons and neutrons. However, it does not stop there: these protons and neutrons in turn consist of particles called quarks. These are the smallest constituents of the universe, and they are bound together by something called gluons (as they act as the glue holding the quarks together). Hadrons is the general name of particles that consist of quarks: protons, neutrons, kaons, pions, etc. Quarks can be seen as the lego pieces forming the hadrons, and the gluons would then be the studs keeping the lego pieces together. At high enough temperatures the quarks and gluons stop being bound to hadrons, and they form this quark-gluon plasma. The QGP is like a hot, dense soup of quarks and gluons.
As mentioned previously, the QGP existed for the first milliseconds after the big bang. However, it can also be produced for a brief moment after collisions of heavy ions (such as Pb) due to the large amount of energy released during such a collision. ALICE (A Large Ion Collider Experiment) is an experiment at one of the world's largest particle accelerators: the LHC. At ALICE the products of heavy ion collisions are being detected partly for the reason of investigating the QGP. Investigating the particles and their distribution after such a collision can provide information about the plasma.
One specific type of quark is called the charm quark, and this type of quark is especially interesting when investigating the QGP. One of the reasons for this is that it is produced early in a collision, and can therefore provide information about the earliest stages of the collision: the stage when the QGP exists.
In this thesis particle collisions are being simulated and the resulting distribution of charmed hadrons are being investigated, to create what is called a balance function. A balance function tells us the following: if we have the position of a charmed hadron: where is its initial partner? Charm quarks are always created in pairs, so if we have detected a charmed hadron, we know that the charm quark in this hadron has an initial partner in some other hadron. This relationship between where in space a charm quark and its initial partner are located in the final state (the state the detector will be able to analyse) is what this balance function will tell us.
In this thesis it will be attempted to create as realistic simulations as possible, to imitate as closely as possible what it might look like in real data. Using data from LHC Run 3 (2022-2025) this type of balance function could be interesting to measure. To then compare the appearance of the balance function in the two settings: (i) LHC setting where we expect to see a QGP, and (ii) the setting from these simulations where we do not expect to see a QGP (since proton-proton collisions are being simulated), could provide information about how the QGP works. Aside from this, a prediction about how much data will be needed to create such a balance function from real data could be created.
To summarize: in this thesis the distribution of charmed hadrons after a heavy-ion collision is being investiated in hopes of being able to contribute with information about the QGP. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9089370
- author
- Bonnevier Wallstedt, Tilde LU
- supervisor
- organization
- course
- FYSK02 20221
- year
- 2022
- type
- M2 - Bachelor Degree
- subject
- keywords
- Heavy-ion physics, quark-gluon plasma, QGP, balance function, charm quark
- language
- English
- id
- 9089370
- date added to LUP
- 2022-06-20 09:26:33
- date last changed
- 2022-06-20 09:26:33
@misc{9089370,
abstract = {{In this thesis, pp collisions were simulated using PYTHIA. D+ D- and D0 D0bar balance functions were created in order to contribute with a reference point for future balance functions measured in real data from Pb-Pb collisions. Charm balance functions are important since the charm quark can act as a probe of the QGP, probing the first instances after a collision. The balance functions were created under varying conditions: (i) minimum bias with only events with 2 charms, (ii) forcing charm production and (iii) forcing charm production with only events with 4 charms.
The results were mainly in line with expectations. The main deviation from expectations was that no away-side peak was found in minimum bias collisions, indicating that the distributions are dominated by NLO processes. This was not in line with real data from pp collisions from LHCb.}},
author = {{Bonnevier Wallstedt, Tilde}},
language = {{eng}},
note = {{Student Paper}},
title = {{Projections for charm balance functions in heavy-ion collisions}},
year = {{2022}},
}