Anisotropy as a signature of transverse collective flow

Anisotropic flow inCu+Aucollisions atsNN=200GeV

“…3 [17]. A similar conclusion is obtained for v 4 . Sensitivities of the p T dependence of v 1 at forward mid-η and v 3 at backward mid-η to the parton cross section are also seen.…”

“…Compared with previous results for symmetric Au + Au collisions, charged hadrons produced around midrapidity in asymmetric collisions are found to have a stronger directed flow v 1 and their elliptic flow v 2 is also more sensitive to the parton scattering cross section. Although higher order flows v 3 and v 4 are small at all rapidities, both v 1 and v 2 in these collisions are appreciable and show an asymmetry in forward and backward rapidities. …”

“…The hadron transverse momentum anisotropy is generated by the pressure anisotropy in the initial compressed matter formed in noncentral heavy-ion collisions [2,3] and is sensitive to the properties of produced matter in these collisions. For heavy-ion collisions at the Relativistic Heavy Ion Collider (RHIC), it has been shown that this sensitivity exists not only in the larger elliptic flow [4][5][6][7][8][9][10][11] but also in smaller higher order anisotropic flows [12][13][14][15][16][17][18]. To investigate the influence of initial collision geometry on anisotropic flows in heavy-ion collisions, one usually varies the impact parameter of a collision or the atomic number of colliding nuclei [19].…”

Highlights from STAR

“…Azimuthal anisotropy of particle production is sensitive to the early stage of ultrarelativistic nuclear collisions [21,22]. Figure 4 The hatched band indicates typical results from hydrodynamical calculations [24] from the pion mass (upper dashed curve) to the Ω mass (lower dashed curve).…”

Effective mass splitting of neutron and proton and isospin emission in heavy-ion collisions

“…Rather systematical data has been measured to investigate the equation of state from flow analysis [23,24]. The flow information can be expressed as the first and second coefficients from the Fourier expansion of the azimuthal distribution dN dφ (y, p t ) = N 0 (1 + 2V 1 (y, p t ) cos(φ) + 2V 2 (y, p t ) cos(2φ)) [25], where p t = p 2 x + p 2 y and y are the transverse momentum and the longitudinal rapidity along the beam direction, respectively. The directed (transverse) flow is defined as the first coefficient and expressed as V 1 = p x /p t , which provides the information of the azimuthal anisotropy of the transverse emission.…”