Spin and parity of the Pc(4440) and Pc(4457) pentaquarks · revision history

Revision 2

Accepted · core change · record

Changes against revision 1:

Title
Spin and parity of the Pc(4440) and Pc(4457) pentaquarks
Plain
LHCb found in 2019 that one pentaquark signal is two close peaks, at 4440 and 4457 MeV, both just below the energy of a charmed baryon plus a charmed meson. Molecular models predict spins $1/2$ and $3/2$ for this pair while compact models give other patterns, so measuring the spins tests the pictures.
Precise · changed · core
Revision 1: $\mathrm{Pc}(4440)+$ and $\mathrm{Pc}(4457)+$ appear in $J/\psi\,p$ from $\Lambda_{b} \to J/\psi\,p\,K-$ (LHCb, PRL 122, 222001, 2019), about 20 and 3 MeV below the Sigma_c+ anti-D*0 threshold. Determine $J^{P}$ of each from a full amplitude analysis. Answer: $J^{P}$ values; the Sigma_c anti-D* molecular picture predicts $1/2-$ and $3/2-$, with the ordering set by short-range contact terms.
Revision 2: $\mathrm{Pc}(4440)+$ and $\mathrm{Pc}(4457)+$ appear in $J/\psi\,p$ from $\Lambda_{b} \to J/\psi\,p\,K-$ (LHCb, PRL 122, 222001, 2019), about 20 and 3 MeV below the $\Sigma_{c}+ \mathrm{anti}-D*0$ threshold. Determine $J^{P}$ of each from a full amplitude analysis. Answer: $J^{P}$ values; the $\Sigma_{c}\ \mathrm{anti}-D*$ molecular picture predicts $1/2-$ and $3/2-$, with the ordering set by short-range contact terms.
Settled by
A full amplitude analysis of $\Lambda_b \to \mathrm{J}/\psi\, \mathrm{p}\, \mathrm{K}-$ with LHCb Run 3 statistics, cross-checked in a second production channel.
Kind
well-posed
Answer type
identification
References
(empty)
Literature status
open
Status note
No spin-parity determination of either state had been published, to our knowledge, as of mid-2026.
Posed since
2019

Decisions