%0 Generic %1 du2019evidence %A Du, Meng-Lin %A Baru, Vadim %A Guo, Feng-Kun %A Hanhart, Christoph %A Meißner, Ulf-G. %A Oller, José A. %A Wang, Qian %D 2019 %K tetraquark %T Evidence that the LHCb $P_c$ states are hadronic molecules and the existence of a narrow $P_c(4380)$ %U http://arxiv.org/abs/1910.11846 %X Three hidden-charm pentaquark $P_c$ states, $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$ were revealed in the $Łambda_b^0J/p K^-$ process measured by LHCb using both Run I and Run II data. Their nature is under lively discussion, and their quantum numbers have not been determined. We analyze the $J/\psi$ invariant mass distributions under the assumption that the crossed-channel effects provide a smooth background. For the first time, such an analysis is performed employing a coupled-channel formalism taking into account heavy quark spin symmetry. We find that the data can be well described in the hadronic molecular picture, which predicts seven $\Sigma_c^(*)\bar D^(*)$ molecular states in two spin multiplets, such that the $P_c(4312)$ is mainly a $\Sigma_cD$ bound state with $J^P=1/2^-$, while $P_c(4440)$ and $P_c(4457)$ are $\Sigma_cD^*$ bound states with quantum numbers $3/2^-$ and $1/2^-$, respectively. We also show that there is clear evidence for a narrow $\Sigma_c^*D$ bound state in the data which we call $P_c(4380)$, different from the broad one reported by LHCb in 2015. With this state established, all predicted $\Sigma_c D$, $\Sigma_c^* D$, and $\Sigma_c D^*$ hadronic molecules are seen in the data, while the missing three $\Sigma_c^*D^*$ states with smaller production rates are expected to be found in future runs at the LHC or in photoproduction experiments.

@misc{du2019evidence, abstract = {Three hidden-charm pentaquark $P_c$ states, $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$ were revealed in the $\Lambda_b^0\to J/\psi p K^-$ process measured by LHCb using both Run I and Run II data. Their nature is under lively discussion, and their quantum numbers have not been determined. We analyze the $J/\psi$ invariant mass distributions under the assumption that the crossed-channel effects provide a smooth background. For the first time, such an analysis is performed employing a coupled-channel formalism taking into account heavy quark spin symmetry. We find that the data can be well described in the hadronic molecular picture, which predicts seven $\Sigma_c^{(*)}\bar D^{(*)}$ molecular states in two spin multiplets, such that the $P_c(4312)$ is mainly a $\Sigma_c\bar D$ bound state with $J^P=1/2^-$, while $P_c(4440)$ and $P_c(4457)$ are $\Sigma_c\bar D^*$ bound states with quantum numbers $3/2^-$ and $1/2^-$, respectively. We also show that there is clear evidence for a narrow $\Sigma_c^*\bar D$ bound state in the data which we call $P_c(4380)$, different from the broad one reported by LHCb in 2015. With this state established, all predicted $\Sigma_c \bar D$, $\Sigma_c^* \bar D$, and $\Sigma_c \bar D^*$ hadronic molecules are seen in the data, while the missing three $\Sigma_c^*\bar D^*$ states with smaller production rates are expected to be found in future runs at the LHC or in photoproduction experiments.}, added-at = {2019-10-28T14:34:00.000+0100}, author = {Du, Meng-Lin and Baru, Vadim and Guo, Feng-Kun and Hanhart, Christoph and Meißner, Ulf-G. and Oller, José A. and Wang, Qian}, biburl = {https://www.bibsonomy.org/bibtex/2c9467edf1b8e35c81ff67ff2dad299cd/cmcneile}, description = {Evidence that the LHCb ${P_c}$ states are hadronic molecules and the existence of a narrow $P_c(4380)$}, interhash = {b97ce94bd9f08d669c18690abf2469a1}, intrahash = {c9467edf1b8e35c81ff67ff2dad299cd}, keywords = {tetraquark}, note = {cite arxiv:1910.11846Comment: 7 pages, 1 figure and 1 table}, timestamp = {2019-10-28T14:34:00.000+0100}, title = {Evidence that the LHCb ${P_c}$ states are hadronic molecules and the existence of a narrow $P_c(4380)$}, url = {http://arxiv.org/abs/1910.11846}, year = 2019 }