In this study, the yield and nuclear modification factor ($R_\mathrm{AA}$) for inclusive jet production were measured using 0.49 nb$^{-1}$ of Pb+Pb data at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV and 25 pb$^{-1}$ of $pp$ data at $\sqrt{s}=5.02$ TeV with the ATLAS detector at the Large Hadron Collider (LHC). Jets were reconstructed using the anti-$k_t$ algorithm with a radius parameter $R=0.4$, covering a transverse momentum range of 40-1000 GeV in six rapidity intervals spanning $|y|<2.8$. The results showed that $R_\mathrm{AA}$ increased with rising jet transverse momentum, peaking at approximately 0.6 at 1 TeV in central collisions and increasing towards peripheral collisions. Interestingly, $R_\mathrm{AA}$ was independent of rapidity at low jet transverse momenta but decreased with increasing rapidity at higher momenta. The experimental setup utilized various components of the ATLAS experiment such as the inner detector system (ID), lead/liquid-argon (LAr) electromagnetic (EM) calorimeter, and trigger and data acquisition systems. This detailed analysis provided insights into the dependence of jet suppression on factors like collision centrality and rapidity, shedding light on inclusive jets' behavior in heavy-ion collisions. Overall, this comprehensive study contributes valuable information to our understanding of jet production in high-energy nuclear interactions and has important implications for further research in this field.
SummaryScientists studied how jets are made in big collisions and found that the size of the jet changes depending on how fast it is going. They used special tools to look at this in different situations and learned that some parts of the collision affect the jets more than others.
Definitions
- Yield: The amount of something produced or obtained.
- Nuclear modification factor ($R_{AA}$): A measurement used to compare how particles behave in different types of collisions.
- Inclusive jet production: The creation of high-energy particle clusters called jets in collisions.
- Transverse momentum: The movement of particles perpendicular to their direction of travel.
- Rapidity: A measure related to how fast a particle is moving in a certain direction.
Introduction:
The study of high-energy nuclear interactions has been a major focus in particle physics research for decades. In particular, the production and behavior of jets in heavy-ion collisions have been of great interest due to their potential to provide insights into the properties of the quark-gluon plasma (QGP), a state of matter that is believed to have existed in the early universe. In this context, a recent research paper titled "Measurement of inclusive jet production and nuclear modification factor in Pb+Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV with the ATLAS detector" presents new results on jet production in heavy-ion collisions using data from the ATLAS experiment at the Large Hadron Collider (LHC). This article will provide a detailed overview and analysis of this research paper.
Experimental Setup:
The data used for this study was collected by the ATLAS detector during two different periods: 0.49 nb$^{-1}$ of Pb+Pb data at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV and 25 pb$^{-1}$ of $pp$ data at $\sqrt{s}=5.02$ TeV. The Pb+Pb collision data were taken during LHC's Run 2 period, while $pp$ collision data were taken during Run 3.
Jets are reconstructed using particles detected by various components of the ATLAS experiment, including its inner detector system (ID), lead/liquid-argon (LAr) electromagnetic (EM) calorimeter, and trigger and data acquisition systems. The anti-$k_t$ algorithm with a radius parameter $R=0.4$, which clusters particles based on their distance from each other, was used for jet reconstruction.
Results:
The main focus of this study was to measure both yield and nuclear modification factor ($R_\mathrm{AA}$) for inclusive jet production in Pb+Pb collisions. The yield is the number of jets produced per unit of collision centrality, while $R_\mathrm{AA}$ measures the suppression of jet production in heavy-ion collisions compared to $pp$ collisions.
The results showed that $R_\mathrm{AA}$ increased with rising jet transverse momentum (pT), peaking at approximately 0.6 at 1 TeV in central collisions and increasing towards peripheral collisions. This indicates that jet suppression is stronger in central collisions, where the QGP is expected to be formed, compared to peripheral collisions.
Another interesting finding was that $R_\mathrm{AA}$ was independent of rapidity at low pT but decreased with increasing rapidity at higher pT. This suggests that jet suppression may depend on factors such as energy density and temperature, which vary with rapidity.
Implications:
The results from this study have important implications for our understanding of jet production in high-energy nuclear interactions. The observed dependence of $R_\mathrm{AA}$ on collision centrality and rapidity provides valuable information about the properties of the QGP created in these collisions.
Furthermore, these results can also be used to test theoretical models and improve our understanding of how jets interact with the QGP. For example, some models predict a decrease in jet suppression with increasing pT due to parton energy loss effects becoming less significant at higher energies. However, this study's findings show an increase in suppression with rising pT, indicating a need for further investigation into these models.
Conclusion:
In conclusion, this research paper presents new measurements for inclusive jet production and nuclear modification factor ($R_\mathrm{AA}$) using data from Pb+Pb and $pp$ collisions collected by the ATLAS experiment at LHC. The results provide insights into the behavior of inclusive jets in heavy-ion collisions and their dependence on factors like collision centrality and rapidity.
This study's comprehensive analysis and use of various components of the ATLAS experiment make it a valuable contribution to the field of high-energy nuclear interactions. The findings have important implications for further research in this area, including improving our understanding of jet production in heavy-ion collisions and testing theoretical models.
Measurements of the yield and nuclear modification factor, $R_\mathrm{ AA}$, for inclusive jet production are performed using 0.49 nb$^{-1}$ of Pb+Pb data at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV and 25 pb$^{-1}$ of $pp$ data at $\sqrt{s}=5.02$ TeV with the ATLAS detector at the LHC. Jets are reconstructed with the anti-$k_t$ algorithm with radius parameter $R=0.4$ and are measured over the transverse momentum range of 40-1000 GeV in six rapidity intervals covering $|y|<2.8$. The magnitude of $R_\mathrm{ AA}$ increases with increasing jet transverse momentum, reaching a value of approximately 0.6 at 1 TeV in the most central collisions. The magnitude of $R_\mathrm{ AA}$ also increases towards peripheral collisions. The value of $R_\mathrm{ AA}$ is independent of rapidity at low jet transverse momenta, but it is observed to decrease with increasing rapidity at high transverse momenta.
