Evidence for a new structure in the $J/\psi p$ and $J/\psi \bar{p}$ systems in $B_s^0 \to J/\psi p \bar{p}$ decays

Information

LHCb-PAPER-2021-018
CERN-EP-2021-150
arXiv:2108.04720 [PDF]

(Submitted on 10 Aug 2021)
Phys. Rev. Lett. 128 (2022) 062001
Inspire 1903743

Tools

Abstract

An amplitude analysis of flavour-untagged $B_s^0 \to J/\psi p \bar{p}$ decays is performed using a sample of $797\pm31$ decays reconstructed with the LHCb detector. The data, collected in proton-proton collisions between 2011 and 2018, correspond to an integrated luminosity of 9 $\text{fb}^{-1}$. Evidence for a new structure in the $J/\psi p$ and $J/\psi \bar{p}$ systems with a mass of $4337 \ ^{+7}_{-4} \ ^{+2}_{-2} \text{MeV}$ and a width of $29 \ ^{+26}_{-12} \ ^{+14}_{-14} \text{MeV}$ is found, where the first uncertainty is statistical and the second systematic, with a significance in the range of 3.1 to 3.7 $\sigma$, depending on the assigned $J^P$ hypothesis.

Figures and captions

Invariant-mass distribution $m( { J \mskip -3mu/\mskip -2mu\psi } p \bar{p})$ for reconstructed signal candidates; the result of the fit described in the text is overlaid.	Fig1.pdf [23 KiB] HiDef png [298 KiB] Thumbnail [236 KiB] *.C file
One-dimensional projections of the angular $(\cos\theta_{\mu}, \cos\theta_p, \varphi)$ and invariant-mass distributions $(m( p \overline p ), m( { J \mskip -3mu/\mskip -2mu\psi } p ), m( { J \mskip -3mu/\mskip -2mu\psi } \overline p ))$, superimposed with the results of the fit from the baseline model (blue) and the default model (red) comprising a NR term and the $P_c$ contribution.	Fig2a.pdf [24 KiB] HiDef png [266 KiB] Thumbnail [233 KiB] *.C file
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Dalitz plot distribution for reconstructed candidates (black dots) within the $ B ^0_ s $ signal region. The colour scale represents the number of candidates in each Dalitz plot interval.	Fig2.pdf [44 KiB] HiDef png [746 KiB] Thumbnail [469 KiB] *.C file
Distribution of the maximum (left) and minimum (right) of $m( { J \mskip -3mu/\mskip -2mu\psi } p )$ and $m( { J \mskip -3mu/\mskip -2mu\psi } \overline p )$. Results of the amplitude fit are superimposed, where the sum of the $P_c^+$ and $P_c^-$ contributions is shown in blue.	Fig4a.pdf [18 KiB] HiDef png [234 KiB] Thumbnail [204 KiB] *.C file
	Fig4b.pdf [17 KiB] HiDef png [195 KiB] Thumbnail [168 KiB] *.C file
Animated gif made out of all figures.	PAPER-2021-018.gif Thumbnail

Tables and captions

Systematic uncertainties associated to the mass $M_{P_c}$ (in $\text{ Me V}$ ), width $\Gamma_{P_c}$ (in $\text{ Me V}$ ), modulus of coupling $A(P_c)$, fit fractions $f(P_c)$ (in %), $p$-values and associated significance ($\sigma$) of the $P_c^{\pm}$ state.	Table_1.pdf [73 KiB] HiDef png [70 KiB] Thumbnail [34 KiB] tex code
$LS$ couplings and free parameters for the NR $1^{--}$ model and the models with the $P_c$ states for different $J^P$ hypotheses. Here, $(L,S)$ and $(l,s)$ refer to the relative angular momentum and spin of $P_c^+ \overline p \ (P_c^- p )$ and $ { J \mskip -3mu/\mskip -2mu\psi } p \ ( { J \mskip -3mu/\mskip -2mu\psi } \overline p )$ final states, respectively, for the $P_c^+$ ($P_c^-$) decay chain. The free parameters are denoted as $(A, \phi)$, where $A$ is the modulus and $\phi$ the phase of the coupling.	Table_2.pdf [78 KiB] HiDef png [52 KiB] Thumbnail [24 KiB] tex code
Results for all spin-parity hypotheses. Values of $-2 \Delta \log\mathcal{L}$ (-2DLL), $p$-value and two-sided significance extracted from pseudoexperiments, together with mass (in $\text{ Me V}$ ), width (in $\text{ Me V}$ ), fit fraction and complex coupling (A,$\phi$) of the $P_c$ states are reported.	Table_3.pdf [69 KiB] HiDef png [53 KiB] Thumbnail [23 KiB] tex code

Supplementary Material [file]

Supplementary material full pdf	supple[..].pdf [217 KiB]
This ZIP file contains supplemetary material for the publication LHCb-PAPER-2021-018. The files are: LHCb-PAPER-2021-018_supplementary.pdf : An overview of the extra figures .pdf, .png, .eps, .C: The figures in variuous formats to compile, just do ``pdflatex supplementary``	Fig5a.pdf [18 KiB] HiDef png [185 KiB] Thumbnail [182 KiB] *C file
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