# Search for structure in the $B_s^0\pi^\pm$ invariant mass spectrum

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## Abstract

The claim by the D0 collaboration of the observation of a tetraquark state, dubbed the $X(5568)$, in the $B ^0_ s \pi ^\pm$ invariant mass distribution is investigated. The analysis is based on a data sample recorded with the LHCb detector corresponding to $3\,fb^{-1}$ of $pp$ collision data at $\sqrt{s} = 7$ and $8 \mathrm{\,Te\kern -0.1em V}$. No significant excess is found, and upper limits are set on the production rate of the claimed $X(5568)$ state.

## Figures and captions

 Selected candidates for (left) $B ^0_ s \rightarrow D ^-_ s \pi ^+$ and (right) $B ^0_ s \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \phi$ decays. Results of the fits described in the text are superimposed with the total fit result shown as a dashed black line, and signal and background components as red and blue solid lines. Fig1a.pdf [25 KiB] HiDef png [164 KiB] Thumbnail [49 KiB] Fig1b.pdf [26 KiB] HiDef png [153 KiB] Thumbnail [49 KiB] Results of the fit to the $Q$ value distribution, shifted to display the $B ^0_ s \pi ^\pm$ invariant mass, for $B ^0_ s \pi ^\pm$ candidates (both $B ^0_ s$ modes combined) with minimum $B ^0_ s$ $p_{\mathrm{ T}}$ of (top) $5 {\mathrm{\,Ge\kern -0.1em V\!/}c}$ and (bottom) $10 {\mathrm{\,Ge\kern -0.1em V\!/}c}$. The pull distributions, shown underneath the main figures, show good agreement between the fit functions and the data. Fig2a.pdf [115 KiB] HiDef png [356 KiB] Thumbnail [93 KiB] Fig2b.pdf [115 KiB] HiDef png [380 KiB] Thumbnail [108 KiB] Results of the fit to the $Q$ value distribution, shifted to display the $B ^0_ s \pi ^+$ invariant mass, for $B ^0_ s \pi$ candidates (both $B ^0_ s$ modes combined) with the signal yield fixed to zero. The fits are shown for minimum $B ^0_ s$ $p_{\mathrm{ T}}$ of (left) $5 {\mathrm{\,Ge\kern -0.1em V\!/}c}$ and (right) $10 {\mathrm{\,Ge\kern -0.1em V\!/}c}$. The pull distributions, shown underneath the main figures, show good agreement between the fit functions and the data. Fig3a.pdf [114 KiB] HiDef png [349 KiB] Thumbnail [91 KiB] Fig3b.pdf [114 KiB] HiDef png [371 KiB] Thumbnail [106 KiB] Results of the fit to the $Q$ value distribution for $B ^0 \pi$ candidates. Fig4.pdf [75 KiB] HiDef png [347 KiB] Thumbnail [91 KiB] Results of the fit to the $Q$ value distribution, shifted to display the $B ^0_ s \pi ^+$ invariant mass, for $B ^0_ s \pi$, $B ^0_ s \rightarrow D ^-_ s \pi ^+$ candidates with minimum $B ^0_ s$ $p_{\mathrm{ T}}$ of (left) $5 {\mathrm{\,Ge\kern -0.1em V\!/}c}$ and (right) $10 {\mathrm{\,Ge\kern -0.1em V\!/}c}$. The pull distributions, shown underneath the main figures, show good agreement between the fit functions and the data. Fig5a.pdf [114 KiB] HiDef png [363 KiB] Thumbnail [96 KiB] Fig5b.pdf [115 KiB] HiDef png [383 KiB] Thumbnail [108 KiB] Results of the fit to the $Q$ value distribution, shifted to display the $B ^0_ s \pi ^+$ invariant mass, for $B ^0_ s \pi$, $B ^0_ s \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \phi$ candidates with minimum $B ^0_ s$ $p_{\mathrm{ T}}$ of (left) $5 {\mathrm{\,Ge\kern -0.1em V\!/}c}$ and (right) $10 {\mathrm{\,Ge\kern -0.1em V\!/}c}$. The pull distributions, shown underneath the main figures, show good agreement between the fit functions and the data. Fig6a.pdf [115 KiB] HiDef png [357 KiB] Thumbnail [99 KiB] Fig6b.pdf [112 KiB] HiDef png [377 KiB] Thumbnail [107 KiB] Results of fits to the $Q$ value distribution, shifted to display the $B ^0_ s \pi ^+$ invariant mass, for $B ^0_ s \pi$ candidates (both $B ^0_ s$ modes combined) with minimum $B ^0_ s$ $p_{\mathrm{ T}}$ of $5 {\mathrm{\,Ge\kern -0.1em V\!/}c}$ in different rapidity bins. From left to right, top to bottom: $y\in [1.8,2.6]$, $y\in [2.6,3.0]$, $y\in [3.0,3.4]$, $y\in [3.4,5.0]$. Fig7a.pdf [56 KiB] HiDef png [202 KiB] Thumbnail [67 KiB] Fig7b.pdf [56 KiB] HiDef png [197 KiB] Thumbnail [65 KiB] Fig7c.pdf [58 KiB] HiDef png [200 KiB] Thumbnail [64 KiB] Fig7d.pdf [56 KiB] HiDef png [194 KiB] Thumbnail [64 KiB] Results of fits to the $Q$ value distribution, shifted to display the $B ^0_ s \pi ^+$ invariant mass, for $B ^0_ s \pi$ candidates (both $B ^0_ s$ modes combined) with minimum $B ^0_ s$ $p_{\mathrm{ T}}$ of $10 {\mathrm{\,Ge\kern -0.1em V\!/}c}$ in different rapidity bins. From left to right, top to bottom: $y\in [1.8,2.6]$, $y\in [2.6,3.0]$, $y\in [3.0,3.4]$, $y\in [3.4,5.0]$. Fig8a.pdf [57 KiB] HiDef png [207 KiB] Thumbnail [69 KiB] Fig8b.pdf [56 KiB] HiDef png [199 KiB] Thumbnail [66 KiB] Fig8c.pdf [56 KiB] HiDef png [195 KiB] Thumbnail [65 KiB] Fig8d.pdf [58 KiB] HiDef png [207 KiB] Thumbnail [69 KiB] Distribution of $Q$ value, shifted to display the $B ^0_ s \pi ^+$ invariant mass (both $B ^0_ s$ modes combined), for candidates with minimum $B ^0_ s$ $p_{\mathrm{ T}}$ of $10 {\mathrm{\,Ge\kern -0.1em V\!/}c}$, with a signal component superimposed that corresponds to $\rho_X^{\rm LHCb} = 8.6\,\%$. The shape and yield of the combinatorial background component is obtained from the fit with the signal yield fixed to zero, shown in Fig. 3 (right). Fig9.pdf [21 KiB] HiDef png [210 KiB] Thumbnail [67 KiB]

## Tables and captions

 Yields $N( B ^0_ s )$ and $N(X)$ obtained from the fits to the $B ^0_ s$ candidate mass distributions and the $B ^0_ s \pi ^\pm$ Q-value distributions, respectively, with statistical uncertainties only. The values reported for $N( B ^0_ s )$ are those inside the $B ^0_ s$ signal window. Relative efficiencies $\epsilon^{\rm rel}(X)$ are also given. Results are given for the baseline selection and for the case where the $B ^0_ s$ minimum $p_{\mathrm{ T}}$ requirement is increased to $10 {\mathrm{\,Ge\kern -0.1em V\!/}c}$. Table_1.pdf [53 KiB] HiDef png [65 KiB] thumbnail [10 KiB] tex code

Created on 04 March 2017.Citation count from INSPIRE on 04 March 2017.