Azimuthally Differential Pion Femtoscopy in Pb-Pb Collisions at sNN=2.76  TeV

Abstract

We present the first azimuthally differential measurements of the pion source size relative to the second harmonic event plane in Pb-Pb collisions at a center-of-mass energy per nucleon-nucleon pair of ffiffiffiffiffiffiffiffi s NN p ¼ 2.76 TeV. The measurements have been performed in the centrality range 0%-50% and for pion pair transverse momenta 0.2 < k T < 0.7 GeV=c. We find that the R side and R out radii, which characterize the pion source size in the directions perpendicular and parallel to the pion transverse momentum, oscillate out of phase, similar to what was observed at the Relativistic Heavy Ion Collider. The final-state source eccentricity, estimated via R side oscillations, is found to be significantly smaller than the initial-state source eccentricity, but remains positive-indicating that even after a stronger expansion in the in-plane direction, the pion source at the freeze-out is still elongated in the out-of-plane direction. The 3 þ 1D hydrodynamic calculations are in qualitative agreement with observed centrality and transverse momentum R side oscillations, but systematically underestimate the oscillation magnitude.

Influence of Spatial and Dynamical Anisotropies on Flow and Femtoscopy Radii in Relativistic Heavy-Ion Collisions at LHC Energies

“…One can see, however, that the relative magnitude of the radii oscillations is reproduced fairly well. For instance, ∆R 2 out and ∆R 2 side between the maxima and minima values do not exceed 15-20% for second-order oscillations [13] and 8-12% for third-order ones [14]. HYDJET++ calculations nicely match these results.…”

“…The calculations with ε 2 = ±0.3 are displayed in Figure 1. ALICE data from [13] for the momentum interval 0.5 < k T < 0.7 GeV/c are plotted onto the calculations also. Recall that the main goal of our present study is the search for the influence of pure spatial and pure dynamical anisotropies on the harmonics of anisotropic flow and femtoscopic radii.…”

“…The oscillations of femtoscopic radii w.r.t. the reaction planes of elliptic flow Ψ 2 and triangular flow Ψ 3 were found experimentally in heavy-ion collisions at energies of RHIC [12] and LHC [13,14]. For brevity, these oscillations are dubbed second-order and third-order oscillations, respectively.…”

Small systems at the LHC

“…ported by the ALICE Collaboration have shown that, when taking the difference between the yields per trigger particle in high-multiplicity and low-multiplicity events, two nearly identical long-range ridge-like excess structures on the near-side and away-side, the so-called "double ridge", arise [9,10]. Results on two-particle correlations of identified hadrons [11][12][13][14] and of Bose-Einstein (HBT) correlations [15,16] further stressed the initial observations, showing striking similarities between pp, p-Pb and Pb-Pb collisions, consistent with the hydrodynamic picture of a particle-production source expanding more explosively along the collision event plane.…”

Therapeutic Potential of Ursolic Acid in Cancer and Diabetic Neuropathy Diseases

“…Improvements can be associated with the UA effects in skeletal muscle [241]. Many studies were indicated that the improved making of irisin in the muscle induced through physical exercise could encourage the making of neurotrophins in the hippocampus [242], neurogenesis, and synaptogenesis in rodents [243]. Multiple synthesized methods based on UA with anti-diabetic, anti-inflammatory, and cardioprotective were identified [243], the neuroprotective potential of UA and analogous compounds, advising, which they can be helpful to the management of PD and AD.…”