March 17, 2017

"The LHCb experiment at CERN is a hotbed of new and outstanding physics results. In just the last few months, the collaboration has announced the measurement of a very rare particle decay and evidence of a new manifestation of matter-antimatter asymmetry, to name just two examples." In a paper released today, the LHCb collaboration announced the discovery of a new system of five particles all in a single analysis. by Stefania Pandolfi

'The exceptionality of this discovery is that observing five new states all at once is a rather unique event.

'The particles were found to be excited states – a particle state that has a higher energy than the absolute minimum configuration (or ground state) – of a particle called "Omega-c-zero", Ωc0. This Ωc0 is a baryon, a particle with three quarks, containing two "strange" and one "charm" quark. Ωc0 decays via the strong force into another baryon, called "Xi-c-plus", Ξc+ (containing a "charm", a "strange" and an "up" quark) and a kaon K-. Then the Ξc+ particle decays in turn into a proton p, a kaon K- and a pion π+.

'From the analysis of the trajectories and the energy left in the detector by all the particles in this final configuration, the LHCb collaboration could trace back the initial event – the decay of the Ωc0 – and its excited states. These particle states are named, according to the standard convention, Ωc(3000)0, Ωc(3050)0, Ωc(3066)0, Ωc(3090)0 and Ωc(3119)0. The numbers indicate their masses in megaelectronvolts (MeV), as measured by LHCb.'

"Observation of five new narrow Ω0c states decaying to Ξ+cK−" by R. Aaij, et al, here

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