Isospin breaking decays as a diagnosis of the hadronic molecular structure of the Pc(4457)

Abstract

The LHCb Collaboration announced the observation of three narrow structures consistent with hidden-charm pentaquark states. They are candidates of hadronic molecules formed of a pair of a charmed baryon and an anticharmed meson. Among them, the P c (4457) mass is consistent with earlier predictions of a Σ cD * molecule with I = 1/2. We point out that if such a picture were true, one would have B(P c (4457) → J/ψ∆ + )/B(P c (4457) → J/ψp) at the level ranging from a few percent to about 30%. Such a large isospin breaking decay ratio is two to three orders of magnitude larger than that for normal hadron resonances. It is a unique feature of the Σ cD * molecular model, and can be checked by LHCb. * Four years after the discovery of the hidden-charm pentaquark-like states P c (4380) and P c (4450) [1], with the full set of Run-1 and Run-2 data the LHCb Collaboration announced the observation of more structures consistent with hidden-charm pentaquark states with masses and widths given by [2, 3] M Pc(4312) + = 4311.9 ± 0.7 +6.8 −0.6 MeV, Γ Pc(4312) + = 9.8 ± 2.7 +3.7 −4.5 MeV, M Pc(4440) + = 4440.3 ± 1.3 +4.1 −4.7 MeV, Γ Pc(4440) + = 20.6 ± 4.9 +8.7 −10.1 MeV,

Production of Pc states from Λb decay

“…Very recently, the LHCb Collaboration updated its analysis of the J=ψp invariant mass spectroscopy of Λ b → KJ=ψp and found three pentaquark states, which are P þ c ð4312Þ, P þ c ð4440Þ, and P þ c ð4457Þ [33]. After the new observation, some interpretation has been proposed immediately in the molecular [34][35][36][37][38][39][40][41][42][43][44][45][46][47] and pentaquark scenarios [48][49][50][51][52][53][54]. In addition, by fitting the LHCb data around 4312 MeV with the amplitudes satisfying the general principles of S-matrix theory, P c ð4312Þ is assigned as a virtual state resulting from the weak interactions ofD and Σ c [55].…”

Hidden-charm pentaquarks and Pc states

“…Moreover, we use the model to explore the nnscc, ssncc, and ssscc pentaquark states. P c (4312) + : M = 4311.9 ± 0.7 +6.8 −0.6 MeV, Γ = 9.8 ± 2.7 +3.7 −4.5 MeV, P c (4440) + : M = 4440.3 ± 1.3 +4.1 −4.7 MeV, Γ = 20.6 ± 4.9 +8.7 −10.1 MeV, P c (4457) + : M = 4457.3 ± 0.6 +4.1 −1.7 MeV, Γ = 6.4 ± 2.0 +5.7 −1.9 MeV.Since their masses are slightly below the Σ cD , Σ * cD , and Σ cD * thresholds respectively, they can be interpreted as molecules composed of a charm baryon and an anticharm meson [37][38][39][40][41][42][43][44][45][46][47][48][49]. For example, Chen [46] interpreted them as bound states of Σ cD with J P = 1/2 − , Σ * cD with J P = 3/2 − , and Σ cD * with J P = 3/2 − , while Chen et al [45], He [48], and Liu et al [49] interpreted the P c (4312), P c (4440), and P c (4457) as loosely bound Σ cD with (I = 1/2, J P = 1/2 − ), Σ cD * with (I = 1/2, J P = 1/2 − ), and Σ cD * with (I = 1/2, J P = 3/2 − ).…”

Decay behaviors of possible Λcc¯ states in hadronic molecule pictures

“…Recently, the new updated results by LHCb collaboration [2] clearly show that the three narrow states are all just below the corresponding anticharmed meson charmed baryon thresholds, which strongly suggests the hadronic molecule nature for them. There are several new theoretical papers [53][54][55][56][57][58][59][60][61][62] triggered by the new LHCb results support meson baryon state description, mainly fromD ( * ) Σ ( * ) , although they have different views in detail. Only Ref.…”