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Teilchenphysik Donnerstag
T 503 Diffraktion
Zeit: Donnerstag 16:15–18:15 Raum: HS 10
T 503.1 Do 16:15 HS 10
Dijets in Diffractive Photoproduction at HERA — •Sebastian
Schätzel 1 , Olaf Behnke 1 , Franz Eisele 1 , and Frank-Peter
Schilling 2 — 1 Physikalisches Institut, Universität Heidelberg —
2 DESY Hamburg
Diffractive parton densities extracted from diffractive deep-inelastic
scattering (DDIS) at HERA fail to describe hard p¯p diffractive scattering
at the Tevatron. Photoproduction provides a transition between DIS
and p¯p collisions and can reveal the underlying mechanism of factorization
breaking. Preliminary results, obtained with the H1 experiment at
HERA, are presented for the production of jet pairs in diffractive photoproduction.
The measurements are compared to predictions based on
diffractive structure functions extracted in DDIS and to models which
try to explain the suppression of diffractive processes in p¯p collisions.
T 503.2 Do 16:30 HS 10
Pomeron- and Odderon Induced Photoproduction of Mesons
Decaying to Pure Multiphoton Final States at HERA —
•Christoph von Cube, Thomas Berndt, Tobias Golling,
Karlheinz Meier, Oliver Nix, and Jürgen Stiewe for the H1
collaboration — KIP, Schröderstr. 90, 69120 Heidelberg
Cross section measurements made at HERA for the reactions γp → ωp
and γp → ωπ 0 X, and on searches for the reactions γp → π 0 N ∗ ,
γp → f2(1270)X, andγp → a 0 2(1320)X, whereN ∗ denotes an excited
nucleon state, are presented. The mean γp centre-of-mass energy was
〈W 〉 = 200 GeV (215 GeV for the reaction γp → π 0 N ∗ ). Cross sections
for the Pomeron-mediated reactions were determined in agreement with
previous measurements and phenomenological expectations. In contrast,
Odderon induced processes have not been observed; upper limits on cross
sections are below predictions from a non-perturbative QCD model.
T 503.3 Do 16:45 HS 10
Exklusive Elektroproduktion von J/Ψ imZEUS Experiment bei
sehr kleinem Q 2 — •Joachim Tandler für die ZEUS-Kollaboration
— DESY, ZEUS Bonn, Notkestraße 85, 22607 Hamburg
Bei HERA kann man den Positronenstrahl als Quelle virtueller Photonen
auffassen. Wenn ein Positron unter einem kleinen Winkel gestreut
und in einem speziellen Kalorimeter (BPC) nachgewiesen wird, ist die
Virtualität Q 2 des Photons auf einen Bereich (für tiefinelastische Streuung
an HERA) sehr kleiner Werte festgelegt (0.15 6GeVand−1