Measurement of beauty photoproduction at threshold using di-electron events with the H1 detector at HERA

The cross section of b anti b photoproduction in ep collisions has been measured with the H1 detector at HERA. Events containing b-quarks were identified through detection of two low momentum electrons in the nal state. Semileptonic decays b anti b→eeX were exploited in the kinematic range of the photon virtuality Q2<1 GeV2, the inelasticity 0.2<y<0.8 and the pseudorapidity of the b-quarks vertical stroke η(b),η(anti b) vertical stroke < 2. The measured differential b-quark production cross section as a function of the transverse b-quark momentum extends the previously experimentally accessible phase space towards the b-quark production threshold. The results are compared to other b-quark cross section measurements, as well as to leading-order and next-to-leading-order QCD predictions. The extension to lower b-quark momenta became possible with a dedicated low momentum electron trigger in the data period 2007, which combines track (Fast Track Trigger) and calorimeter information (Jet Trigger), and by mastering the experimental challenges of low pT-electron identification. (orig.)