Elastic rho^0 photoproduction has been measured using the ZEUS detector at HERA. Untagged photoproduction events from ep interactions were used to measure the reaction gamma p --> rho^ p (rho^0 --> pi+ pi-) at photon-proton centre-of mass energies between 60 and 80 GeV and |t| < 0.5 GeV^2, where t is the square of the four-momentum transferred at the proton vertex. The differential cross section d(sigma)/dM(pi pi), where M (pi pi) is the invariant mass of the two pions, and the integrated cross section, sigma(gamma p --> rho^0 p) are presented; the latter was measured to be 14.7 +- 0.4 (stat.) +- 2.4 (syst.) microbarn. The differential cross section d(sigma)/dt has an approximately exponential shape. The rho^0 is produced predominantly with transverse polarisation, demostrating that s-channel helicity conservation holds at these energies.
Measurement of elastic rho^0 photoproduction at HERA.
ANZIVINO, Giuseppina
1995
Abstract
Elastic rho^0 photoproduction has been measured using the ZEUS detector at HERA. Untagged photoproduction events from ep interactions were used to measure the reaction gamma p --> rho^ p (rho^0 --> pi+ pi-) at photon-proton centre-of mass energies between 60 and 80 GeV and |t| < 0.5 GeV^2, where t is the square of the four-momentum transferred at the proton vertex. The differential cross section d(sigma)/dM(pi pi), where M (pi pi) is the invariant mass of the two pions, and the integrated cross section, sigma(gamma p --> rho^0 p) are presented; the latter was measured to be 14.7 +- 0.4 (stat.) +- 2.4 (syst.) microbarn. The differential cross section d(sigma)/dt has an approximately exponential shape. The rho^0 is produced predominantly with transverse polarisation, demostrating that s-channel helicity conservation holds at these energies.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
