Azimuthal asymmetry of pions in pp and pA collisions

Journal Article · Mon Dec 01 00:00:00 EST 2008 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.78.114009· OSTI ID:21250997

Kopeliovich, B Z; Rezaeian, A H; Schmidt, Ivan ^[1]

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1. Departamento de Fisica y Centro de Estudios Subatomicos, Universidad Tecnica Federico Santa Maria, Casilla 110-V, Valparaiso (Chile)

We investigate the azimuthal asymmetry v{sub 2} of produced pions in pp and pA collisions at both the Relativistic Heavy Ion Collider and CERN SPS energies. In our approach, based on the perturbative QCD parton model and the light-cone QCD-dipole formalism, the azimuthal asymmetry results from a correlation between the color-dipole orientation and the impact parameter of the collision. We introduce the color-dipole orientation within an improved Born approximation and the saturation model which satisfies available deep inelastic scattering data, showing that the azimuthal asymmetry of partons and pions is very sensitive to the choice of the model, and that it is reduced in the saturation model. We find that v{sub 2} of quarks and gluons in parton-nucleus collisions have very different patterns. The azimuthal asymmetry of gluons in gluon-nucleus collisions can be negative at small transverse momentum, and can change sign and become positive at high transverse momentum. The azimuthal asymmetry of quarks in quark-nucleus collisions is positive at all values of transverse momentum. We find that the azimuthal anisotropy v{sub 2} of produced pions in both pp and pA collisions is positive, albeit rather small.

• OSTI ID: 21250997
• Journal Information: Physical Review. D, Particles Fields, Vol. 78, Issue 11; Other Information: DOI: 10.1103/PhysRevD.78.114009; (c) 2008 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ANISOTROPY
ASYMMETRY
BORN APPROXIMATION
CERN SPS SYNCHROTRON
COLLISIONS
COLOR MODEL
DEEP INELASTIC SCATTERING
DIPOLES
GLUONS
HEAVY ION REACTIONS
IMPACT PARAMETER
ION-ATOM COLLISIONS
PERTURBATION THEORY
PIONS
PROTON-PROTON INTERACTIONS
QUANTUM CHROMODYNAMICS
QUARKS
SATURATION
TRANSVERSE MOMENTUM