Observation of an ExcitedBc±Meson State with the ATLAS Detector

Abstract

A search for excited states of the Bc(±) meson is performed using 4.9 fb(-1) of 7 TeV and 19.2 fb(-1) of 8 TeV pp collision data collected by the ATLAS experiment at the LHC. A new state is observed through its hadronic transition to the ground state, with the latter detected in the decay Bc(±)→J/ψπ(±). The state appears in the m(Bc(±)π(+)π(-))-m(Bc(±))-2m(π(±)) mass difference distribution with a significance of 5.2 standard deviations. The mass of the observed state is 6842±4±5 MeV, where the first error is statistical and the second is systematic. The mass and decay of this state are consistent with expectations for the second S-wave state of the Bc(±) meson, Bc(±)(2S).

Properties of excited charmed-bottom mesons

“…In 2014 an excited state of B c meson was observed by ATLAS experiment at LHC through the decay channel B ± c → J/ψ π ± in pp collisions. The measured mass of the excited state was found to be 6842 ± 4 ± 5 MeV [4], which is considered as the second S-wave state of B c . However, this excited state has not been confirmed by other experiments yet.…”

Parametrizing the detector response with neural networks

“…For this purpose, muon momentum reconstruction provides the motivation. Characterizing the muon momentum resolution is important for resonance searches [21,22] and has both Gaussian and non-Gaussian components. Further details of the muon momentum reconstruction can be found in Ref.…”

Hard diffractive ηc,b hadroproduction at the LHC

“…A variety of attempts have been carried out to estimate those probabilities [70][71][72], however the actual values are rather uncertain. The selected value can be regarded a lower limit given the recent available experimental results [73,74].…”