Observation of New Baryons in the Ξb-π+π- and Ξb0π+π- Systems

Information

LHCb-PAPER-2023-008
CERN-EP-2023-126
arXiv:2307.13399 [PDF]

(Submitted on 25 Jul 2023)
Phys. Rev. Lett. 131 (2023) 171901
Inspire 2680343

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Abstract

The first observation and study of two new baryonic structures in the final state $\Xi_b^0\pi^+\pi^-$ and the confirmation of the $\Xi_b(6100)^-$ state in the $\Xi_b^-\pi^+\pi^-$ decay mode are reported using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9$\mathrm{fb}^{-1}$. In addition, the properties of the known $\Xi_b^{*0}$, $\Xi_b^{'-}$ and $\Xi_b^{*-}$ resonances are measured with improved precision. The new decay mode of the $\Xi_b^0$ baryon to the $\Xi_c^+\pi^-\pi^+\pi^-$ final state is observed and exploited for the first time in these measurements.

Figures and captions

Distributions of the mass difference $Q = m_{\Xi _ b \pi} - m_{\Xi _ b } - m_{\pi}$ for selected (a) $\Xi ^-_ b $ $\pi ^+$ and (b) $\Xi ^0_ b $ $\pi ^-$ candidates. The fit results are superimposed.	fig1a.pdf [84 KiB] HiDef png [341 KiB] Thumbnail [233 KiB] *.C file
	fig1b.pdf [91 KiB] HiDef png [338 KiB] Thumbnail [235 KiB] *.C file
Distributions of the mass difference $Q = m_{\Xi _ b \pi\pi} - m_{\Xi _ b } - 2 m_{\pi}$ for selected (a) $\Xi ^-_ b $ $\pi ^+$ $\pi ^-$ candidates in the $\Xi ^{0}_ b $ mass window, (b) $\Xi ^0_ b $ $\pi ^-$ $\pi ^+$ candidates in the $\Xi '^{-}_ b $ mass window and (c) $\Xi ^0_ b $ $\pi ^-$ $\pi ^+$ candidates in the $\Xi ^{-}_ b $ mass window. The fit results are superimposed.	fig2a.pdf [161 KiB] HiDef png [208 KiB] Thumbnail [170 KiB] *.C file
	fig2b.pdf [171 KiB] HiDef png [218 KiB] Thumbnail [180 KiB] *.C file
	fig2c.pdf [164 KiB] HiDef png [195 KiB] Thumbnail [166 KiB] *.C file
Mass distributions of the (a) $\Xi ^-_ b \rightarrow \Xi ^0_ c \pi ^- $, (b) $\Xi ^0_ b \rightarrow \Xi ^+_ c \pi ^- $, (c) $\Xi ^-_ b \rightarrow \Xi ^0_ c \pi ^- \pi ^+ \pi ^- $ and (d) $\Xi ^0_ b \rightarrow \Xi ^+_ c \pi ^- \pi ^+ \pi ^- $ selected signal candidates.	fig3a.pdf [42 KiB] HiDef png [339 KiB] Thumbnail [242 KiB] *.C file
	fig3b.pdf [42 KiB] HiDef png [336 KiB] Thumbnail [242 KiB] *.C file
	fig3c.pdf [41 KiB] HiDef png [368 KiB] Thumbnail [270 KiB] *.C file
	fig3d.pdf [41 KiB] HiDef png [336 KiB] Thumbnail [238 KiB] *.C file
Distributions of the mass difference $Q = m_{\Xi _ b \pi\pi} - m_{\Xi _ b } - 2 m_{\pi}$ for selected $\Xi ^-_ b $ $\pi ^+$ $\pi ^-$ candidates, (a) in the $\Xi ^{0}_ b $ mass window and (b) outside the $\Xi ^{0}_ b $ mass window. The results of the simultaneous fit are superimposed.	fig4.pdf [208 KiB] HiDef png [433 KiB] Thumbnail [395 KiB] *.C file
Distributions of the mass difference $Q = m_{\Xi _ b \pi\pi} - m_{\Xi _ b } - 2 m_{\pi}$ for selected $\Xi ^0_ b $ $\pi ^+$ $\pi ^-$ candidates, (a) in the $\Xi '^{-}_ b $ mass window, (b) in the $\Xi ^{*-}_ b $ mass window and (c) outside the mass windows of the intermediate resonances. The results of the simultaneous fit are superimposed.	fig5.pdf [258 KiB] HiDef png [704 KiB] Thumbnail [647 KiB] *.C file
Animated gif made out of all figures.	PAPER-2023-008.gif Thumbnail

Tables and captions

Systematic uncertainties ( $\text{ Me V}$ ) on the measured physical properties. The parameters $Q_0$ and $\Gamma$ are the mean and the width of the Breit--Wigner distribution, respectively.	Table_1.pdf [61 KiB] HiDef png [43 KiB] Thumbnail [21 KiB] tex code
Masses and widths of the states considered in this Letter. The first uncertainty is statistical, the second systematic. The third uncertainty on $m_0$ is due to limited knowledge of the $\Xi ^-_ b $ and $\Xi ^0_ b $ baryon masses [30].	Table_2.pdf [65 KiB] HiDef png [162 KiB] Thumbnail [86 KiB] tex code

Supplementary Material [file]

	fig3a.pdf [42 KiB] HiDef png [339 KiB] Thumbnail [242 KiB] *C file
	fig3b.pdf [42 KiB] HiDef png [336 KiB] Thumbnail [242 KiB] *C file
	fig3c.pdf [41 KiB] HiDef png [368 KiB] Thumbnail [270 KiB] *C file
	fig3d.pdf [41 KiB] HiDef png [336 KiB] Thumbnail [238 KiB] *C file
	fig4.pdf [208 KiB] HiDef png [433 KiB] Thumbnail [395 KiB] *C file
	fig5.pdf [258 KiB] HiDef png [704 KiB] Thumbnail [647 KiB] *C file