The yield of kaonic hydrogen X-rays in the SIDDHARTA experiment

¹ Department of Physics, School of Science, The University of Tokyo, Bunkyo-ku Hongo 7-3-1, Tokyo, Japan,
² INFN, Laboratori Nazionali di Frascati, C.P. 13, Via E. Fermi 40, I-00044 Frascati(Roma), Italy,
³ Department of Physics and Astronomy, University of Victoria, P.O. Box 1700 STN CNC, Victoria BC V8W 2Y2, Canada,
⁴ Stefan-Meyer-Institut für Subatomare Physik, Boltzmanngasse 3, 1090 Wien, Austria,
⁵ IFIN-HH, Institutul National pentru Fizica si Inginerie Nucleara Horia Hulubbei, Reactorului 30, Magurele, Romania,
⁶ Politecnico di Milano, Dipartimento di Elettronica, Informazione e Bioingegneria, Milano, Italy,
⁷ INFN Sezione di Milano, Milano, Italy,
⁸ INFN Sezione di Roma I and Instituto Superiore di Sanita, I-00161 Roma, Italy,
⁹ RIKEN, Institute of Physical and Chemical Research, 2-1 Hirosawa, Wako, Saitama 251-0198, Japan,
¹⁰ Excellence Cluster Universe, Technische Universität München, Boltzmannstraße 2, D-85748 Garching, Germany,
¹¹ Universidade de Santiago de Compostela, Casas Reais 8, 15782 Santiago de Compostela, Spain.

^a e-mail: Hexi.Shi@oeaw.ac.at

Published online: 20 March 2014

Abstract

We measured K-series kaonic hydrogen X-rays in the SIDDHARTA experiment performed at the DAΦNE electron-positron collider of Laboratori Nazionali di Frascati. With a gaseous hydrogen target of density 15 ρ_STP, preliminary values of the absolute yields, defined as the number of atomic X-rays emitted per kaon stopped inside the target, were determined to be 0.012_−0.004^+0.003 for K_α transition and 0.045_−0.012^+0.009 for K_tot, the summation of all the emitted K-series transitions.