Observation of New Ξc0 Baryons Decaying to Λc+K−

Abstract

The Λ þ c K − mass spectrum is studied with a data sample of pp collisions at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 5.6 fb −1 collected by the LHCb experiment. Three Ξ 0 c states are observed with a large significance and their masses and natural widths are measured to be m½Ξ c ð2923Þ 0 ¼ 2923.04 AE 0.25 AE 0.20 AE 0.14 MeV, Γ½Ξ c ð2923Þ 0 ¼ 7.1 AE 0.8 AE 1.8 MeV, m½Ξ c ð2939Þ 0 ¼ 2938.55 AE 0.21 AE 0.17 AE 0.14 MeV, Γ½Ξ c ð2939Þ 0 ¼ 10.2 AE 0.8 AE 1.1 MeV, m½Ξ c ð2965Þ 0 ¼ 2964.88 AE 0.26 AE 0.14 AE 0.14 MeV, Γ½Ξ c ð2965Þ 0 ¼ 14.1 AE 0.9 AE 1.3 MeV, where the uncertainties are statistical, systematic, and due to the limited knowledge of the Λ þ c mass. The Ξ c ð2923Þ 0 and Ξ c ð2939Þ 0 baryons are new states. The Ξ c ð2965Þ 0 state is in the vicinity of the known Ξ c ð2970Þ 0 baryon; however, their masses and natural widths differ significantly.

QQs¯s¯ tetraquarks in the chiral quark model

“…Later on, the LHCb collaboration also announced one more Λ 0 b baryon around 6070 MeV in the Λ 0 b π þ π − invariant mass spectrum [4], which is consistent with the reported one of the CMS collaboration [5]. Additionally, three excited Ξ 0 c states were announced by the LHCb collaboration in the Λ þ c K − mass spectrum [6].…”

Charmed baryon spectrum from lattice QCD near the physical point

“…Ref. [12], Ξ c ð2965Þ, either corresponds to the already seen Ξ c ð2970Þ or is another entirely new resonance.…”

“…Above 2.9 GeV=c 2 , the PDG reports the five states Ξ c ð2930Þ, Ξ c ð2970Þ, Ξ c ð3055Þ, Ξ c ð3080Þ and Ξ c ð3123Þ, for none of which the spin and parity quantum numbers have been measured. Very recently, the spectrum of these states has received an update by a new measurement of the LHCb Collaboration [12] in the Λ þ c K − channel. According to this measurement, the Ξ c ð2930Þ (observed earlier by the Belle [4] and the BABAR [10] Collaborations in the same channel) should be considered to be a previously unresolved combination of two independent states Ξ c ð2923Þ and Ξ c ð2939Þ.…”

“…In contrast, the Ξ c sector is quite rich since it can have flavor symmetric and antisymmetric wave functions. There are up to seven Ξ c excitations observed by the Belle [4][5][6][7][8][9], the BABAR [10,11] and very recently by the LHCb [12] Collaborations in the energy range of 2920-3120 MeV=c 2 . The PDG considers the existence of three of them to be very likely or certain while the confidence for the other two is smaller.…”

Canonical interpretations of the newly observed $$\Xi _c(2923)^0$$, $$\Xi _c(2939)^0$$, and $$\Xi _c(2965)^0$$ resonances

“…Theoretical interpretations on c (2930) and c (2970) resonances include conventional charmed strange baryons [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] and molecular states [23][24][25][26] with various quantum numbers. The observations of LHCb Collaboration indicate that the c (2930) 0 should be the overlap of the two narrow states c (2923) 0 and c (2939) 0 , and whether the c (2970) 0 and c (2965) 0 structures are different or not needs further investigations [1]. Above 3000 MeV, the situation becomes more complicated, and the detailed explanations and discussions can be found in the reviews [38][39][40].…”