Observation of Lambda H-4 hyperhydrogen by decay-pion spectroscopy in electron scattering

Abstract

At the Mainz Microtron MAMI, the first high-resolution pion spectroscopy from decays of strange systems was performed by electron scattering off a Be-9 target in order to study the ground-state masses of Lambda-hypernuclei. Positively charged kaons were detected by a short-orbit spectrometer with a broad momentum acceptance at zero degree forward angles with respect to the beam, efficiently tagging the production of strangeness in the target nucleus. In coincidence, negatively charged decay-pions were detected by two independent high-resolution spectrometers. About 10^3 pionic weak decays of hyperfragments and hyperons were observed. The pion momentum distribution shows a monochromatic peak at p_pi ~ 133 MeV/c, corresponding to the unique signature for the two-body decay of hyperhydrogen Lambda H-4 -> He-4 + pi-, stopped inside the target. Its binding energy was determined to be B_Lambda = 2.12 +- 0.01 (stat.) +- 0.09 (syst.) MeV with respect to the H-3 + Lambda mass.

References in corpus (3)

• Evaluation of three methods for calculating statistical significance when incorporating a systematic uncertainty into a test of the background-only hypothesis for a Poisson process
• Charge symmetry breaking in $\Lambda$ hypernuclei revisited
• The hyperon-nucleon interaction: conventional versus effective field theory approach

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• Measurement of ${}_{\mathrm{\Lambda }}^4\mathrm{H}$ and ${}_{\mathrm{\Lambda }}^4\mathrm{He}$ binding energy in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 3 GeV
• Spectroscopy of $A=9$ hyperlithium by the $(e,e^{\prime }{K}^{+})$ reaction
• High Precision Momentum Calibration of the Magnetic Spectrometers at MAMI for Hypernuclear Binding Energy Determination
• Decay pion spectroscopy: a new approach
• Isospin breaking from diquark clustering
• Light hyperclusters and hyperons in low-density hot stellar matter