Collectivity in Large and Small Collision Systems: Flow in Xe+Xe Collisions and Sensitivity to the Presence of Hard Scatterings in pp Collisions

The Quark-Gluon Plasma (QGP) produced in heavy-ion collisions has been shown to behave like a nearly perfect fluid, characterized by a very low ratio of shear viscosity to entropy density. Significant measurements in large collision systems have improved the constraints on the value of /. However, the precise temperature dependence of / still remains unknown. The interplay between viscous effects and initial geometry fluctuations is important that requires further investigation. Another key open question in the study of multi-particle production is the relationship between the “ridge” – observed azimuthal correlations between particles in the underlying event that extend over all rapidities – and hard or semi-hard scattering processes in small collision systems. In particular, it is not known whether jets or their soft fragments are correlated with particles in the underlying event. This dissertation presents two analyses. The first analysis measures flow harmonics 2–6 in 3 b^-1 of Xe+Xe collisions at √ = 5.44 TeV using the ATLAS detector at the LHC. The centrality, multiplicity, and _T dependence of the n values obtained using two-particle correlations and template-fit procedure are presented, and the measurements are compared with those in Pb+Pb collisions and +Pb collisions at 5.02 TeV. The n values in Xe+Xe collisions are observed to be larger than those in Pb+Pb collisions for n = 2, 3, and 4 in the most central events. However, the n values in Xe+Xe collisions become smaller than those in Pb+Pb collisions with decreasing centrality or increasing harmonic order n. The n in Xe+Xe and Pb+Pb collisions are also compared as a function of the mean number of participating nucleons and the measured charged-particle multiplicity in the detector. The 3 values in Xe+Xe and Pb+Pb collisions are observed to be similar at the same ⟨_part⟩ or multiplicity, but the other harmonics are significantly different. The second analysis studies two-particle correlations in pp collisions at 13 TeV using data collected by the ATLAS experiment at the LHC, with an integrated luminosity of 15.8 pb⁻¹, in two different configurations. In the first case, charged particles associated with jets are excluded from the correlation analysis, while in the second case, correlations are measured between particles within jets and charged particles from the underlying event. Second-order flow coefficients, 2, are presented as a function of event multiplicity and transverse momentum. These measurements show that excluding particles associated with jets does not affect the measured correlations. Moreover, particles associated with jets do not exhibit any significant azimuthal correlations with the underlying event, ruling out hard processes contributing to the ridge

Single-cell sequencing combined with machine learning reveals the mechanism of interaction between epilepsy and stress cardiomyopathy

BackgroundEpilepsy is a disorder that can manifest as abnormalities in neurological or physical function. Stress cardiomyopathy is closely associated with neurological stimulation. However, the mechanisms underlying the interrelationship between epilepsy and stress cardiomyopathy are unclear. This paper aims to explore the genetic features and potential molecular mechanisms shared in epilepsy and stress cardiomyopathy.MethodsBy analyzing the epilepsy dataset and stress cardiomyopathy dataset separately, the intersection of the two disease co-expressed differential genes is obtained, the co-expressed differential genes reveal the biological functions, the network is constructed, and the core modules are identified to reveal the interaction mechanism, the co-expressed genes with diagnostic validity are screened by machine learning algorithms, and the co-expressed genes are validated in parallel on the epilepsy single-cell data and the stress cardiomyopathy rat model.ResultsEpilepsy causes stress cardiomyopathy, and its key pathways are Complement and coagulation cascades, HIF-1 signaling pathway, its key co-expressed genes include SPOCK2, CTSZ, HLA-DMB, ALDOA, SFRP1, ERBB3. The key immune cell subpopulations localized by single-cell data are the T_cells subgroup, Microglia subgroup, Macrophage subgroup, Astrocyte subgroup, and Oligodendrocytes subgroup.ConclusionWe believe epilepsy causing stress cardiomyopathy results from a multi-gene, multi-pathway combination. We identified the core co-expressed genes (SPOCK2, CTSZ, HLA-DMB, ALDOA, SFRP1, ERBB3) and the pathways that function in them (Complement and coagulation cascades, HIF-1 signaling pathway, JAK-STAT signaling pathway), and finally localized their key cellular subgroups (T_cells subgroup, Microglia subgroup, Macrophage subgroup, Astrocyte subgroup, and Oligodendrocytes subgroup). Also, combining cell subpopulations with hypercoagulability as well as sympathetic excitation further narrowed the cell subpopulations of related functions

Mechanisms of Myocardial Stunning in Stress-Induced Cardiomyopathy

Stress-induced cardiomyopathy, in contrast to acute myocardial infarction, is a type of acute heart failure characterized by reversible left ventricular dysfunction. Cardiac imaging primarily reveals left ventricle myocardial stunning, 81.7% of which is apical type. Emotional or psychological stress usually precedes the onset of stress-induced cardiomyopathy, which is increasingly being recognized as a unique neurogenic myocardial stunning disease. To distinguish between acute myocardial infarction and acute viral or auto-immune myocarditis, this review summarizes specific mechanisms of myocardial stunning in stress-induced cardiomyopathy, such as calcium disorders, metabolic alterations, anatomical and histological variations in different parts of the left ventricle, and microvascular dysfunction

The Role of Sleep Deprivation in Arrhythmias

Sleep is essential to the normal psychological and physiological activities of the human body. Increasing evidence indicates that sleep deprivation is associated with the occurrence, development, and poor treatment effects of various arrhythmias. Sleep deprivation affects not only the peripheral nervous system but also the central nervous system, which regulates the occurrence of arrhythmias. In addition, sleep deprivation is associated with apoptotic pathways, mitochondrial energy metabolism disorders, and immune system dysfunction. Although studies increasingly suggest that pathological sleep patterns are associated with various atrial and ventricular arrhythmias, further research is needed to identify specific mechanisms and recommend therapeutic interventions. This review summarizes the findings of sleep deprivation in animal experiments and clinical studies, current challenges, and future research directions in the field of arrhythmias

Measurement of the sensitivity of two particle correlations in pp collisions at s=13\sqrt{s}=13~TeV to the presence of jets with the ATLAS detector

Measurements of two-particle correlations in $pp$ collisions show the presence of long-range correlations along $\Delta\eta$ that are strikingly similar to those seen in heavy-ion collisions. In heavy-ion collisions, the long-range correlations are known to arise from the collective dynamics of the produced quark-gluon plasma (QGP). The similarity between the $pp$ and heavy-ion measurements raises the possibility that a tiny droplet of the QGP is produced even in $pp$ collisions. However, models that attribute the correlation in $pp$ collisions to semi-hard processes can qualitatively reproduce the measurements. Thus performing the $pp$ measurements with an active rejection of particles associated with semi-hard processes, such as low-$p_{\mathrm{T}}$ jets, can further elucidate the origin of the long-range correlations. This poster presents measurements of two-particle correlations in $pp$ collisions at $\sqrt{s}=13$ TeV when removing tracks associated with jets from the event. The jets are reconstructed from tracks using the anti-$k_t$ algorithm, and all tracks within one unit of pseudorapidity of the jet are removed from the correlation analysis. It is demonstrated that such removal of particles in the vicinity of jets affects the magnitude of long-range correlations only by a few percent

ATLAS measurement of the two-particle correlation sensitivity to jets in pppp collisions

Measurements of two-particle correlations in $pp$ collisions show the presence of long-range correlations along $\Delta\eta$ that are strikingly similar to those seen in heavy-ion collisions. In larger systems, the long-range correlations are known to arise from the collective dynamics of the produced quark-gluon plasma (QGP). The similarity between the $pp$ and heavy-ion measurements raises the possibility that a tiny droplet of the QGP is produced even in $pp$. However, models that attribute the correlation in $pp$ collisions to semi-hard processes can qualitatively reproduce the measurements. Thus performing the $pp$ measurements with distinguishing particles associated with semi-hard processes, such as low-$p_{\mathrm{T}}$ jets, can further elucidate the origin of the long-range correlations. This talk presents new measurements of two-particle correlations in $pp$ collisions at $\sqrt{s}=13$~TeV with two different particle pair selections. In the first case, tracks associated with jets are excluded from the correlation analysis. This case results in a minor influence on the magnitude of the long-range correlation. In the second case, the two-particle correlations are measured between jet constituents and the underlying-event tracks. In this case, the correlations show no ridge-like structure

Measurement of the Azimuthal Anisotropy of Charged Particle Production in Xe+Xe Collisions at sNN\sqrt{s_{NN}}=5.44 TeV with the ATLAS Detector

ATLAS measurements of flow harmonics ($v_{n}$) in Xe+Xe collisions are presented. The measurements are performed using two-particle correlations, multi-particle cumulants and scalar product methods. The measurements are also performed using non-flow subtraction techniques -- recently developed for measurements in proton-nucleus and proton-proton collisions -- to improve the understanding of flow in peripheral collisions. The non-flow removal is shown to have a significant impact on the $v_n$ measurements in peripheral events. By comparing to flow measurements in Pb+Pb collisions, the effects of geometric fluctuations and of viscous effects, both of which are stronger in the smaller Xe+Xe system, are demonstrated

Measurement of the Sensitivity of Two-Particle Correlations in pppp Collisions to the Presence of Hard Scatterings

Measurements of two-particle correlations in $pp$ collisions show the presence of long-range correlations along $\Delta\eta$ that are similar to those seen in heavy-ion collisions. The similarity between the $pp$ and heavy-ion measurements raises the possibility that a tiny droplet of the QGP is produced even in $pp$ collisions. However, alternative models that attribute the correlations in $pp$ collisions to semi-hard processes can also qualitatively reproduce the measurements. Therefore, differentiating between particles produced from semi-hard processes, such as low-$p_{\mathrm{T}}$ jets, and those produced from soft interactions can help determine the origin of the correlations in $pp$ collisions. This talk presents measurements of two-particle correlations in $pp$ collisions at $\sqrt{s}=13$ TeV with two different particle-pair selections. In the first case, tracks associated with jets are excluded from the correlation analysis. This shows that excluding tracks associated with jets does not affect the measured correlations. In the second case, correlations are measured between tracks that are constituents of jets and tracks from the underlying event, which showed that jets do not exhibit any azimuthal correlations with the underlying event. These measurements provide a further understanding of the collective signatures observed in $pp$ collisions

The Study of Flow and Non-flow Effects in Small Collision Systems

Recent research at RHIC and the LHC suggests that a quark-gluon plasma (QGP) can also be formed in the collisions of small systems (e.g., d+Au, p+Pb). In large collision systems (e.g., Au+Au, Pb+Pb), the effect of flow in the QGP is large compared to other contributions, the so-called non-flow\u27\u27 effects. However, in small collision systems, these non-flow effects are more dominant and must be better understood in order to extract the real flow signal from the data. In this thesis, I present calculations of elliptic flow v_2--- the second-order momentum anisotropy coefficient--- in d+Au, Au+Au, p+Pb, and Pb+Pb collisions at 20, 39, 62.5, 200 GeV and 5.02TeV from simulated data generated with the AMPT and the UrQMD models. The participant plane, the event plane, and the multi-particle cumulant methods are applied to analyze the simulated data

Characterizing the collective behavior in small and large systems with ATLAS

Measurements of open heavy-flavor hadron production in proton-proton collisions provide a crucial baseline for interpreting measurements in nucleus-nucleus collisions, and allow for the investigation of the origin and underlying mechanism of collective effects in small systems. These measurements are performed with the ATLAS detector at the LHC and capitalize on the large Run 2 $pp$ dataset at 5.02 TeV and 13 TeV. This talk presents published results on the azimuthal anisotropy ($v_2$ and $v_3$) of muons from heavy-flavor decays in 13 TeV $pp$ collisions, as well as new results on the heavy-flavor muon production cross-section in 5.02 TeV $pp$ collisions. In both measurements, muons from charm and bottom hadrons with $p_\mathrm{T} > 4$ GeV are statistically separated using the transverse impact parameter with respect to the primary collision vertex. Muons from charm hadrons are found to have a significant azimuthal anisotropy in high-multiplicity $pp$ collisions, with a magnitude and $p_\mathrm{T}$-dependence similar to that for light hadrons. On the other hand, the anisotropy for muons from bottom hadrons is significantly smaller, compatible with zero, demonstrating a strong mass dependence for collective effects in small systems. Additionally, the differential cross-section for charm and bottom muon production in $5.02$ TeV $pp$ collisions is presented and compared to FONLL predictions. We discuss this measurement in the context of similar data-theory comparisons in $pp$ collisions at other experiments and collision energies