cern.ch

Search for beautiful tetraquarks in the $\Upsilon(1S)\mu^+\mu^-$ invariant-mass spectrum

[to restricted-access page]

Information

Tools

Contact

Abstract

The $\Upsilon(1S)\mu^+\mu^-$ invariant-mass distribution is investigated for a possible exotic meson state composed of two $b$ quarks and two $\overline{b}$ quarks, $X_{b\overline{b}b\overline{b}}$. The analysis is based on a data sample of $pp$ collisions recorded with the LHCb detector at centre-of-mass energies $\sqrt{s} =$ 7, 8 and 13 TeV, corresponding to an integrated luminosity of 6.3 fb$^{-1}$. No significant excess is found, and upper limits are set on the product of the production cross-section and the branching fraction as functions of the mass of the $X_{b\overline{b}b\overline{b}}$ state. The limits are set in the fiducial volume where all muons have pseudorapidity in the range $[2.0,5.0]$, and the $X_{b\overline{b}b\overline{b}}$ state has rapidity in the range $[2.0,4.5]$ and transverse momentum less than 15 GeV/$c$.

Figures and captions

Linear fit to the ratio of the $X$ and $\Y1S$ widths as a function of the $X$ mass as determined from fits to simulated data samples. The error bars represent the statistical uncertainty arising from the finite size of the simulated samples.

fig1a.pdf [14 KiB]
HiDef png [129 KiB]
Thumbnail [50 KiB]
*.C file
fig1a.pdf

Distributions of $m(\mu ^+\mu ^- )$ for the normalisation datasets at $ p p $ centre-of-mass energies of (a) 7 $\mathrm{\,Te V}$ , (b) 8 $\mathrm{\,Te V}$ , (c) 13 $\mathrm{\,Te V}$ and (d) all combined. The total fit function (solid blue line), the combinatorial background (dashed red line) and the $\Y1S$, $\Y2S$ and $\Y3S$ components (hatched magenta area) are shown overlaid.

fig2a.pdf [49 KiB]
HiDef png [236 KiB]
Thumbnail [66 KiB]
*.C file
fig2a.pdf
fig2b.pdf [49 KiB]
HiDef png [240 KiB]
Thumbnail [67 KiB]
*.C file
fig2b.pdf
fig2c.pdf [49 KiB]
HiDef png [250 KiB]
Thumbnail [72 KiB]
*.C file
fig2c.pdf
fig2d.pdf [49 KiB]
HiDef png [246 KiB]
Thumbnail [70 KiB]
*.C file
fig2d.pdf

Distributions of $m(2\mu^+2\mu^-)$ for the signal datasets at $ p p $ centre-of-mass energies of (a) 7 $\mathrm{\,Te V}$ , (b) 8 $\mathrm{\,Te V}$ , (c) 13 $\mathrm{\,Te V}$ and (d) all combined, using a bin size comparable to the expected $X$ mass resolution. In each case the region around the corresponding $\Y1S$ peak has been selected. The background-only fit function (solid blue line) is shown overlaid. The dotted black lines indicate the range in which limits are set on the product of the $X$ production cross-section and branching fractions. The dash-dotted red and long-dashed green lines show the positions of the $\eta_b\eta_b$ and $\Y1S\Y1S$ thresholds, respectively.

fig3a.pdf [26 KiB]
HiDef png [216 KiB]
Thumbnail [78 KiB]
*.C file
fig3a.pdf
fig3b.pdf [27 KiB]
HiDef png [234 KiB]
Thumbnail [85 KiB]
*.C file
fig3b.pdf
fig3c.pdf [31 KiB]
HiDef png [271 KiB]
Thumbnail [101 KiB]
*.C file
fig3c.pdf
fig3d.pdf [31 KiB]
HiDef png [276 KiB]
Thumbnail [103 KiB]
*.C file
fig3d.pdf

The 95 % CL upper limits on $S\equiv \sigma( p p \rightarrow X)\times\mathcal{B}(X\rightarrow \Y1S\mu ^+\mu ^- ) \times \mathcal{B}(\Y1S\rightarrow \mu^+\mu^-)$ as functions of the $X$ mass hypothesis at $ p p $ centre-of-mass energies of (a) 7 $\mathrm{\,Te V}$ , (b) 8 $\mathrm{\,Te V}$ and (c) 13 $\mathrm{\,Te V}$ and (d) all combined.

fig4a.pdf [17 KiB]
HiDef png [194 KiB]
Thumbnail [63 KiB]
*.C file
fig4a.pdf
fig4b.pdf [17 KiB]
HiDef png [225 KiB]
Thumbnail [68 KiB]
*.C file
fig4b.pdf
fig4c.pdf [17 KiB]
HiDef png [251 KiB]
Thumbnail [74 KiB]
*.C file
fig4c.pdf
fig4d.pdf [17 KiB]
HiDef png [252 KiB]
Thumbnail [75 KiB]
*.C file
fig4d.pdf

The kinematic distribution of (black) simulated $X$ particles in (a) $ p_{\mathrm{ T}} $ and (b) rapidity, and (c) the 2D distribution. For comparison, the kinematic distribution of (red) simulated $\Y4S$ particles is also shown.

fig5a.pdf [13 KiB]
HiDef png [113 KiB]
Thumbnail [45 KiB]
*.C file
fig5a.pdf
fig5b.pdf [12 KiB]
HiDef png [51 KiB]
Thumbnail [24 KiB]
*.C file
fig5b.pdf
fig5c.pdf [13 KiB]
HiDef png [95 KiB]
Thumbnail [40 KiB]
*.C file
fig5c.pdf
fig5d.pdf [20 KiB]
HiDef png [212 KiB]
Thumbnail [98 KiB]
*.C file
fig5d.pdf

Animated gif made out of all figures.

PAPER-2018-027.gif
Thumbnail
thumbnail_PAPER-2018-027.gif

Tables and captions

Upper limits on $\sigma( p p \rightarrow X) \times \mathcal{B}(X\rightarrow \Y1S\mu ^+\mu ^- ) \times \mathcal{B}(\Y1S\rightarrow \mu ^+\mu ^- )$ for different $X$ mass hypotheses in the range $[17.5,18.4] {\mathrm{\,Ge V\!/}c^2} $.

Table_1.pdf [32 KiB]
HiDef png [570 KiB]
Thumbnail [95 KiB]
tex code
Table_1.pdf

Upper limits on $\sigma( p p \rightarrow X) \times \mathcal{B}(X\rightarrow \Y1S\mu ^+\mu ^- ) \times \mathcal{B}(\Y1S\rightarrow \mu ^+\mu ^- )$ for different $X$ mass hypotheses in the range $[18.4,19.3] {\mathrm{\,Ge V\!/}c^2} $.

Table_2.pdf [32 KiB]
HiDef png [551 KiB]
Thumbnail [93 KiB]
tex code
Table_2.pdf

Upper limits on $\sigma( p p \rightarrow X) \times \mathcal{B}(X\rightarrow \Y1S\mu ^+\mu ^- ) \times \mathcal{B}(\Y1S\rightarrow \mu ^+\mu ^- )$ for different $X$ mass hypotheses in the range $[19.3,20.0] {\mathrm{\,Ge V\!/}c^2} $.

Table_3.pdf [32 KiB]
HiDef png [468 KiB]
Thumbnail [77 KiB]
tex code
Table_3.pdf

Created on 19 April 2019.Citation count from INSPIRE on 24 April 2019.