DPG Phi
Verhandlungen
Verhandlungen
DPG

Freiburg 1998 – scientific programme

Parts | Days | Selection | Search | Downloads | Help

T: Teilchenphysik

T 403: Diffraktion I

T 403.2: Group Report

Wednesday, March 25, 1998, 08:55–09:20, HS C

Diffractive vector meson production at HERMES — •Falk Meissner — DESY Zeuthen, Platanenallee 6, 15738 Zeuthen

The electro-production of ρ0,φ, ω and J/ψ vector mesons has been studied at the HERMES experiment at the HERA accelerator at DESY. Longitudinally polarised positrons of 27.5 GeV are scattered on different polarised and unpolarised internal gas targets. In 1997 the third year of data taking was successfully completed.
The measured cross sections cover a Q2 range of 0.2 < Q2 < 5 GeV2 and thus span over a region where pQCD is expected to become valid. Additionally they might resolve a possible discrepancy between existing data from NMC and E665. The measurement of the polar angular distributions of the ρ0–decay gives access to the ρ0 longitudinal polarisation and provides a test of s-channel helicity conservation. Similar analyses are in progress for the φ and ω mesons, where smaller event samples were collected.
The comparison of ρ0 production on 1H , 2H, 3He and 14N targets allows a determination of nuclear transparency.
The J/ψ–meson is studied within the charm program of HERMES. The production of charmed mesons gives a handle on the gluon content of the nucleon, however different models of J/ψ–formation have to be distinguished. In the HERMES kinematics diffractive J/ψ production is expected to be dominant.

100% | Mobile Layout | Deutsche Version | Contact/Imprint/Privacy
DPG-Physik > DPG-Verhandlungen > 1998 > Freiburg