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

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## Abstract

The $B_s^0\pi^\pm$ invariant mass distribution is investigated in order to search for possible exotic meson states. 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 $8$ TeV. No significant excess is found, and upper limits are set on the production rate of the claimed $X(5568)$ state within the LHCb acceptance. Upper limits are also set as a function of the mass and width of a possible exotic meson decaying to the $B_s^0\pi^\pm$ final state. The same limits also apply to a possible exotic meson decaying through the chain $B_s^{*0}\pi^\pm$, $B_s^{*0} \to B_s^0 \gamma$ where the photon is excluded from the reconstructed decays.

## 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, with $p_{\mathrm{ T}} ( B ^0_ s ) > 5 \mathrm{ Ge V}$, where the $B ^0_ s$ signal window requirements of $|m( D ^-_ s \pi ^+ ) - 5367 \mathrm{ Me V} | < 30 \mathrm{ Me V}$ and $|m( { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \phi) - 5367 \mathrm{ Me V} | < 13 \mathrm{ Me V}$ are indicated by dotted lines. Results of the fits described in the text are superimposed with the total fit result shown as a red line, the signal component as an unfilled area, the combinatorial background component as a dark blue area and additional background contributions as a light green area. Fig1a.pdf [35 KiB] HiDef png [192 KiB] Thumbnail [171 KiB] *.C file Fig1b.pdf [35 KiB] HiDef png [187 KiB] Thumbnail [161 KiB] *.C file Results of the fit to the $B ^0_ s \pi ^\pm$ mass distribution for candidates (both $B ^0_ s$ modes combined) with minimum $p_{\mathrm{ T}} ( B ^0_ s )$ of (top) $5 \mathrm{ Ge V}$, (middle) $10 \mathrm{ Ge V}$ and (bottom) $15 \mathrm{ Ge V}$. The component for the claimed $X(5568)$ state is included in the fit but is not significant. The distributions of the normalised residuals, or "pulls", displayed underneath the main figures show good agreement between the fit functions and the data. Fig2a.pdf [47 KiB] HiDef png [321 KiB] Thumbnail [256 KiB] *.C file Fig2b.pdf [46 KiB] HiDef png [323 KiB] Thumbnail [260 KiB] *.C file Fig2c.pdf [46 KiB] HiDef png [339 KiB] Thumbnail [282 KiB] *.C file Upper limits (ULs) at 90 % confidence level (CL) as functions of the mass and width of a purported exotic state $X$ decaying to $B ^0_ s \pi ^\pm$ with minimum $p_{\mathrm{ T}} ( B ^0_ s )$ of (top) $5 \mathrm{ Ge V}$, (middle) $10 \mathrm{ Ge V}$ and (bottom) $15 \mathrm{ Ge V}$. The same limits also apply to a possible exotic meson decaying through the chain $B ^{*0}_ s \pi ^\pm$, $B ^{*0}_ s \rightarrow B ^0_ s \gamma$ where the photon is excluded from the reconstructed decays. In the latter case the nominal mass difference $m( B ^{*0}_ s ) - m( B ^0_ s ) = 48.6^{+1.8}_{-1.6} \mathrm{ Me V}$ [16] has to be added to the values on the x-axis to get the mass of the exotic meson under investigation. Fig3a.pdf [19 KiB] HiDef png [258 KiB] Thumbnail [206 KiB] *.C file Fig3b.pdf [19 KiB] HiDef png [256 KiB] Thumbnail [207 KiB] *.C file Fig3c.pdf [19 KiB] HiDef png [268 KiB] Thumbnail [215 KiB] *.C file Animated gif made out of all figures. PAPER-2016-029.gif Thumbnail

## Tables and captions

 Yields, $N$, of $B ^0_ s$ and $X(5568)$ candidates obtained from the fits to the $B ^0_ s$ and $B ^0_ s \pi ^\pm$ candidate mass distributions, with statistical uncertainties only. The values reported for $N( B ^0_ s )$ are those inside the $B ^0_ s$ signal window. The reported values for $X(5568)$ are obtained from fits with signal mass and width parameters fixed to those determined by the D0 collaboration. Relative efficiencies $\epsilon^{\rm rel}(X)$ of the $B ^0_ s$ and $X(5568)$ candidate selection criteria are also given. The reported uncertainties on the relative efficiencies are only statistical, due to the finite size of the simulated samples. Table_1.pdf [53 KiB] HiDef png [108 KiB] Thumbnail [55 KiB] tex code

## Supplementary Material [file]

 Supplementary material full pdf supple[..].pdf [230 KiB] This ZIP file contains supplemetary material for the publication LHCb-PAPER-2016-029. The files are: Supplementary.pdf : An overview of the extra figures *.pdf, *.png, *.eps : The figures in variuous formats Fig1a.pdf [44 KiB] HiDef png [312 KiB] Thumbnail [248 KiB] *C file Fig1b.pdf [43 KiB] HiDef png [314 KiB] Thumbnail [253 KiB] *C file Fig1c.pdf [43 KiB] HiDef png [330 KiB] Thumbnail [275 KiB] *C file Fig2.pdf [39 KiB] HiDef png [276 KiB] Thumbnail [223 KiB] *C file

Created on 20 August 2019.Citation count from INSPIRE on 23 August 2019.