First observation of a doubly charged tetraquark and its neutral partner

Information

LHCb-PAPER-2022-026
CERN-EP-2022-239
arXiv:2212.02716 [PDF]

(Submitted on 06 Dec 2022)
Phys. Rev. Lett. 131 (2023) 041902
Inspire 2682593

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Abstract

A combined amplitude analysis is performed for the decays $B^0 \rightarrow \overline{D}^0 D^+_s\pi^-$ and $B^+\rightarrow D^- D^+_s\pi^+$, which are related by isospin symmetry. The analysis is based on data collected by the LHCb detector in proton-proton collisions at center-of-mass energies of 7, 8 and 13$ \rm{TeV}$. The full data sample corresponds to an integrated luminosity of 9$ \rm{fb^{-1}}$. Two new resonant states with masses of $2.908\pm0.011\pm0.020 \rm{GeV}$ and widths of $0.136\pm0.023\pm0.011 \rm{GeV}$ are observed, which decay to $D^+_s\pi^+$ and $D^+_s\pi^-$ respectively. The former state indicates the first observation of a doubly charged open-charm tetraquark state with minimal quark content $[c\bar{s}u\bar{d}]$, and the latter state is a neutral tetraquark composed of $[c\bar{s}\bar{u}d]$ quarks. Both states are found to have spin-parity $0^+$, and their resonant parameters are consistent with each other, which suggests that they belong to an isospin triplet.

Figures and captions

Dalitz plots of (a) $ B ^0 \rightarrow \overline{ D } {}^0 D ^+_ s \pi ^- $ and (b) $ B ^+ \rightarrow D ^- D ^+_ s \pi ^+ $ decays after the full selection is applied.	Fig1a.pdf [248 KiB] HiDef png [865 KiB] Thumbnail [485 KiB] *.C file
	Fig1b.pdf [228 KiB] HiDef png [824 KiB] Thumbnail [466 KiB] *.C file
Distributions of (a) $M(\overline{ D } {}^0 \pi ^- )$; (b) $M( D ^+_ s \pi ^- )$; (c) $M(\overline{ D } {}^0 D ^+_ s )$ for the $\overline{ D } \pi$ components of the $ B ^0 \rightarrow \overline{ D } {}^0 D ^+_ s \pi ^- $ candidates; and (d) $M( D ^- \pi ^+ )$; (e) $M( D ^+_ s \pi ^+ )$; (f) $M( D ^- D ^+_ s )$ of the $ B ^+ \rightarrow D ^- D ^+_ s \pi ^+ $ candidates. The data are overlaid with the results of the fits.	Fig2a.pdf [39 KiB] HiDef png [341 KiB] Thumbnail [270 KiB] *.C file
	Fig2b.pdf [35 KiB] HiDef png [341 KiB] Thumbnail [245 KiB] *.C file
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	Fig2d.pdf [39 KiB] HiDef png [333 KiB] Thumbnail [262 KiB] *.C file
	Fig2e.pdf [35 KiB] HiDef png [333 KiB] Thumbnail [239 KiB] *.C file
	Fig2f.pdf [34 KiB] HiDef png [318 KiB] Thumbnail [223 KiB] *.C file
Distributions of (a) $M( D ^+_ s \pi ^- )$ of $ B ^0 \rightarrow \overline{ D } {}^0 D ^+_ s \pi ^- $ decays; and (b) $M( D ^+_ s \pi ^+ )$ for the $ B ^+ \rightarrow D ^- D ^+_ s \pi ^+ $ sample. The data are overlaid with the fit results with the inclusion of the new $0^+$ $ D ^+_ s \pi$ resonant states.	Fig3a.pdf [38 KiB] HiDef png [372 KiB] Thumbnail [252 KiB] *.C file
	Fig3b.pdf [37 KiB] HiDef png [365 KiB] Thumbnail [246 KiB] *.C file
	Fig3legend.pdf [19 KiB] HiDef png [399 KiB] Thumbnail [572 KiB] *.C file
Spin analysis for the $J^P=0^+$ hypothesis over $J^P=1^-$. The solid blue and black dashed histograms are the distributions of the $2\Delta{\rm LL}$ of the pseudoexperiments based on the fit results with the $0^+$ and $1^+$ hypotheses, respectively. The purple vertical line shows the $2\Delta{\rm LL}$ of the data fitted with the new $ D ^+_ s \pi$ exotic state under the $J^P=0^+$ and $J^P=1^-$ hypotheses. The red curve shows the result of a fit with the Gaussian function to the black dashed histogram.	Fig4.pdf [18 KiB] HiDef png [149 KiB] Thumbnail [134 KiB] *.C file
Argand diagram for the $ T^a_{c\bar{s}0}(2900) $ exotic state. The green star and black dots show the start point and phase variation for a $ T^a_{c\bar{s}0}(2900) $ Breit--Wigner function. The red solid line shows the fitted spline function used to model the $J^P = 0^+$ $ D ^+_ s \pi$ component in the $ T^a_{c\bar{s}0}(2900) $ mass region, and the blue error bars show the uncertainties on the values of the spline at the knots.	Fig5.pdf [26 KiB] HiDef png [251 KiB] Thumbnail [242 KiB] *.C file
Animated gif made out of all figures.	PAPER-2022-026.gif Thumbnail

Supplementary Material [file]

This ZIP file contains supplemetary material for the publication LHCb-PAPER-2022-026. The files are: supplementary.tex : LaTeX source file of supplementary supplementary.pdf : An overview of the supplementary figs/.pdf, .png, *.eps : The figures in variuous formats	FigS1a.pdf [43 KiB] HiDef png [344 KiB] Thumbnail [266 KiB] *C file
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