PROBING QUARK GLUON PLASMA WITH BJETS Ins Rebanda
PROBING QUARK GLUON PLASMA WITH B-JETS Inês Rebanda (FCUL) Rodrigo Gazola (FCUL) Supervision: Helena Santos (LIP/FCUL) 1
Quark Gluon Plasma The QGP is a state of extreme temperature and density that happened just after the Big Bang. Assymptoptic freedom is also a characteristic of the QGP and turns that forces between particles become weaker as the density and temperature increases. 2
LHC and the ATLAS detector ATLAS is a generalpurpose LHC detector. The calorimeter system measures the energy, position and momentum of electromagnetic as well as hadronic particles with coverage up to |η| < 5. 3
Jets can be defined as collimated hadronic particle showers that results from the process of hadronization. Jets Initial pt = 0. By momentum conservation, it’s expected that the jets are separated by π. 4
Jets in pp Collision 5
Centrality in Pb+Pb collisions 6
Jet Quenching A signature of the QGP existance! Passage through QGP involves energy loss through collision and radiative interactions. 7
Why B-Jets Bottom quarks are relatively heavy particles. In fact, the heaviest that produce jets. It decays into gluons and other particles. Because they are heavier, they radiate less gluons, which means they lose less energy compared to other jets. 8
Pt, Phi (φ) and Eta (η) for Leading jets Centrality: 0 -10% Irregular η and φ distribution shows passive elements and underlying events in raw data. Data from Pb+Pb collisions at 5. 02 Te. V taken in the Fall of 2018. φ uniformity is expected in ideal conditions. 9
Delta phi and Asymmetry for Leading and Subleading jet (Paper, 2010) L_pt > 100 Ge. V S_pt> 25 Ge. V L_eta < 2. 8 S_eta < 2. 8 If Aj = 0, L and SL are equal. L = Leading jet pt S = Subleading jet pt Data from ”Observation of a Centrality-Dependent Dijet Asymmetry in Lead-Lead Collisions at √s. NN = 2. 76 Te. V with the ATLAS Detector at the LHC” 10
Deltaphi and Asymmetry for Leading and Subleading jet (data) L_pt > 100 Ge. V S_pt> 25 Ge. V L_eta < 2. 8 S_eta < 2. 8 L = Leading jet pt S = Subleading jet pt Data from Pb+Pb collisions at 5. 02 Te. V taken in the Fall of 2018. 11
B-jets, light jets and centrality variations (mv 2 c 10) L_pt > 100 Ge. V S_pt> 25 Ge. V L = Leading jet pt S = Subleading jet pt Data from Pb+Pb collisions at 5. 02 Te. V taken in the Fall of 2018. 12
Centrality in B-jets and light jets (dl 1) L_pt > 100 Ge. V S_pt> 25 Ge. V L = Leading jet pt S = Subleading jet pt If Aj = 0, L and SL are equal. Data from Pb+Pb collisions at 5. 02 Te. V taken in the Fall of 2018. 13
B-jets asymmetries in central (0 -20%) and peripheral (20 -100%) collisions by mv 2 c 10 and dl 1 mv 2 c 10 Data from Pb+Pb collisions at 5. 02 Te. V taken in the Fall of 2018. L = Leading jet pt S = Subleading jet pt If Aj = 0, L and SL are equal. 14
Conclusion ◦ It was possible to verify the QGP influence in jets asymmetry and a different behavior between b-jets and light jet in it’s presence; ◦ It’s neither clear how QGP acts nor how it's formed. It’s also not possible to determine the relative position of the jets to it; ◦ Algorithms were utilized to detect b jets (dl 1 and mv 2 c 10). Despite having used two different ones, we could try others to increase our likelihood of ensuring that we are detecting the right jets. ◦ This work allowed us to understand more about jets (in particular b jets) and made us work with root and a new language that we weren’t familiar with (C++). 15
References ◦ Future of the ATLAS heavy ion program https: //cds. cern. ch/record/1472528/files/ATL-PHYS-PUB-2012 -002. pdf ◦ Overview of Heavy Ions from the ATLAS Experiment∗ PHYS-PROC-2019 -026. pdf https: //cds. cern. ch/record/2667018/files/ATL- ◦ About the ATLAS detector and collisions centrality: Measurement of the pseudorapidity and transverse momentum dependence of the elliptic flow of charged particles in lead-lead collisions at sqrt(s. NN) = 2. 76 Te. V with the ATLAS detector https: //arxiv. org/pdf/1108. 6018. pdf ◦ Dijet asymmetry: Observation of a Centrality-Dependent Dijet Asymmetry in Lead-Lead Collisions at sqrt(S(NN))= 2. 76 Te. V with the ATLAS Detector at the LHC https: //arxiv. org/abs/1011. 6182 ◦ B-tagging in HI events https: //cds. cern. ch/record/2294725/files/ATL-COM-PHYS-2017 -1713. pdf ◦ Measurement of the pseudorapidity and transverse momentum dependence of the elliptic flow of charged particles in lead-lead collisions at √s. NN = 2. 76 Te. V with the ATLAS detector https: //pure. uva. nl/ws/files/1625719/146503_381210. pdf 16
References ◦ Quark Gluon Plasma Formation in Proton-Proton Collisions Using PYTHIA https: //arxiv. org/abs/1902. 05114 ◦ Identification of b-jets and c-jets using Depp Neural Newtwoks with the ATLAS detector: The development and Performance of a Family of DL 1 High-Level Flavour Tagging Algorithms https: //cds. cern. ch/record/2681389 ◦ PPT Heavy Ion Physics https: //indico. lip. pt/event/600/sessions/309/#20190719 17
Correlation between Eta (η) and Pt/Eta (η) and Phi (φ) 18
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