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Measurements of $\psi(2S)$ and $X(3872) \to J/\psi\pi^+\pi^-$ production in $pp$ collisions at $\sqrt{s} = 8$ TeV with the ATLAS detector

The collaboration
JHEP 1701 (2017) 117, 2017

Abstract (data abstract)
Differential cross sections are presented for the prompt and non-prompt production of the hidden-charm states $X(3872)$ and $\psi(2S)$, in the decay mode $J/\psi \pi^+\pi^-$, measured using 11.4~fb$^{-1}$ of $pp$ collisions at $\sqrt{s} = 8$~TeV by the ATLAS detector at the LHC. The ratio of cross-sections $X(3872)/\psi(2S)$ is also given, separately for prompt and non-prompt components, as well as the non-prompt fractions of $X(3872)$ and $\psi(2S)$. Assuming independent single effective lifetimes for non-prompt $X(3872)$ and $\psi(2S)$ production gives $R_B = \frac{\mathcal{B}(B \rightarrow X(3872)\textrm{ + any}) \mathcal{B}(X(3872) \rightarrow J\psi\pi^+\pi^-)}{\mathcal{B}(B \rightarrow \psi(2S)\textrm{ + any}) \mathcal{B}(\psi(2S) \rightarrow J\psi\pi^+\pi^-)} = (3.95 \pm 0.32 \mathrm{(stat)} \pm 0.08\mathrm{(sys)}) \times 10^{-2}$, while separating short- and long-lived contributions, assuming that the short-lived component is due to $B_c$ decays, gives $R_B = (3.57 \pm 0.33\mathrm{(stat)} \pm 0.11\mathrm{(sys)}) \times 10^{-2}$, with the fraction of non-prompt $X(3872)$ produced via $B_c$ decays for $p_\mathrm{T}(X(3872)) > 10$~GeV being $(25 \pm 13\mathrm{(stat)} \pm 2\mathrm{(sys)} \pm 5\mathrm{(spin)})\%$. The distributions of the dipion invariant mass in the $X(3872)$ and $\psi(2S)$ decays are also measured and compared to theoretical predictions.

• #### Table 1

Data from Figure 3(a)

10.17182/hepdata.76839.v1/t1

Measured effective pseudo-proper lifetime for non-prompt $\psi(2S)$ production.

• #### Table 2

Data from Figure 3(a)

10.17182/hepdata.76839.v1/t2

Measured effective pseudo-proper lifetime for non-prompt $X(3872)$ production.

• #### Table 3

Data from Figure 3(b)

10.17182/hepdata.76839.v1/t3

Measured non-prompt $X(3872) / \psi(2S)$ production ratio using the single-lifetime fit model.

• #### Table 4

Data from Figure 4(a)

10.17182/hepdata.76839.v1/t4

Measured prompt $X(3872) / \psi(2S)$ production ratio using the two-lifetime fit model.

• #### Table 5

Data from Figure 4(b)

10.17182/hepdata.76839.v1/t5

Measured non-prompt $X(3872) / \psi(2S)$ production ratio using the two-lifetime fit model.

• #### Table 6

Data from Figure 4(b)

10.17182/hepdata.76839.v1/t6

Measured short-lived non-prompt $X(3872)$ / total non-prompt $\psi(2S)$ production ratio using the two-lifetime fit model.

• #### Table 7

Data from Figure 4(b)

10.17182/hepdata.76839.v1/t7

Measured long-lived non-prompt $X(3872)$ / total non-prompt $\psi(2S)$ production ratio using the two-lifetime fit model.

• #### Table 8

Data from Figure 5(a)

10.17182/hepdata.76839.v1/t8

Measured cross section times branching fractions as a function of pT for prompt $\psi$(2S) production.

• #### Table 9

Data from Figure 5(b)

10.17182/hepdata.76839.v1/t9

Measured cross section times branching fractions as a function of pT for non-prompt $\psi$(2S) production.

• #### Table 10

Data from Figure 6(a)

10.17182/hepdata.76839.v1/t10

Measured cross section times branching fractions as a function of pT for prompt X(3872) production.

• #### Table 11

Data from Figure 6(b)

10.17182/hepdata.76839.v1/t11

Measured cross section times branching fractions as a function of pT for non-prompt X(3872) production.

• #### Table 12

Data from Figure 7(a)

10.17182/hepdata.76839.v1/t12

Measured non-prompt fraction for $\psi(2S)$ production.

• #### Table 13

Data from Figure 7(b)

10.17182/hepdata.76839.v1/t13

Measured non-prompt fraction for X(3872) production.

• #### Table 14

Data from Figure 9(a)

10.17182/hepdata.76839.v1/t14

Normalised differential decay width of $\psi(2S) \rightarrow J/\psi \pi\pi$ in bins of $m_{\pi\pi}$.

• #### Table 15

Data from Figure 9(b)

10.17182/hepdata.76839.v1/t15

Normalised differential decay width of $X(3872) \rightarrow J/\psi \pi\pi$ in bins of $m_{\pi\pi}$.