Bulk viscosity effects in event-by-event relativistic hydrodynamics

Bulk viscosity effects on the collective flow harmonics in heavy-ion collisions are investigated, on an event-by-event basis, using a newly developed 2+1 Lagrangian hydrodynamic code named v-usphydro, which implements the smoothed particle hydrodynamics algorithm for viscous hydrodynamics. A new formula for the bulk viscous corrections present in the distribution function at freeze-out is derived, starting from the Boltzmann equation for multi-hadron species. Bulk viscosity is shown to enhance the collective flow Fourier coefficients from v₂(pT) to v₅(pT) when pT~1--2.5 GeV, even when the bulk viscosity to entropy density ratio, ζ/s, is significantly smaller than 1/(4π).