Abstract
We study the Λ b ( 6146 ) 0 and Λ b ( 6152 ) 0 recently observed by LHCb using the method of Quantum Chromodynamics (QCD) sum rules within the framework of heavy quark effective theory. Our results suggest that they can be interpreted as D-wave bottom baryons of J P = 3 / 2 + and 5 / 2 + respectively, both of which contain two λ -mode excitations. We also investigate other possible assignments containing ρ -mode excitations. We extract all the parameters that are necessary to study their decay properties when using the method of light-cone sum rules. We predict masses of their strangeness partners to be m Ξ b ( 3 / 2 + ) = 6.26 − 0.14 + 0.11 GeV and m Ξ b ( 5 / 2 + ) = 6.26 − 0.14 + 0.11 GeV with the mass splitting Δ M = m Ξ b ( 5 / 2 + ) − m Ξ b ( 3 / 2 + ) = 4.5 − 1.5 + 1.9 MeV, and propose to search for them in future CMS, EIC, and LHCb experiments.
Highlights
In the past few years important experimental progresses were made in the field of bottom baryons
Collaboration discovered the Λb (5912)0 and Λb (5920)0 in 2012 [2], which were later confirmed by the CDF Collaboration [3]. These were the only two excited bottom baryons well observed in experiments, while in the past two years the LHCb and CMS Collaborations continuously observed as many as nine excited bottom baryons:
Invariant mass spectra [4,5]; In 2020 the LHCb Collaboration discovered four excited Ωb states, Ωb (6316)−, Ωb (6330)−, Ωb (6340)−, and Ωb (6350)−, at the same time in the Ξ0b K − invariant mass spectrum [6]; In 2019 the LHCb Collaboration reported their discovery of two excited bottom baryons Λb (6146)0 and Λb (6152)0 in the Λ0b π + π − invariant mass distribution [7]: Λb (6146)0
Summary
In the past few years important experimental progresses were made in the field of bottom baryons. 30 years, such as the constituent quark model [14,15,16,17], the relativistic quark model [9], the chiral quark model [18,19,20], the heavy quark effective theory [10], the quark pair creation model [21,22,23,24], the relativistic flux tube model [11], the color hyperfine interaction [25,26], the chiral perturbation theory [27,28], and Lattice QCD [29,30,31], etc These studies are all based on the traditional excited bottom baryon interpretation, while there exists the molecular interpretation [32,33,34,35,36,37,38,39,40,41,42].
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