While the prompt $$\mathrm{J}/\psi $$ cross section and polarization have been measured with good precision as a function of transverse momentum, $$p_\mathrm{T}$$ , those of the directly produced $$\mathrm{J}/\psi $$ are practically unknown, given that the cross sections and polarizations of the $$\chi _{{c}1} $$ and $$\chi _{{c}2} $$ mesons, large indirect contributors to $$\mathrm{J}/\psi $$ production, are only known with rather poor accuracy. The lack of precise measurements of the $$\chi _{{c}J} $$ polarizations induces large uncertainties in the level of their feed-down contributions to the prompt $$\mathrm{J}/\psi $$ yield, because of the polarization-dependent acceptance corrections. The experimental panorama of charmonium production can be significantly improved through a consistent and model-independent global analysis of existing measurements of $$\mathrm{J}/\psi $$ , $$\psi \mathrm{(2S)}$$ and $$\chi _{c}$$ cross sections and polarizations, faithfully respecting all the correlations and uncertainties. In particular, it is seen that the $$\chi _{{c}J} $$ polarizations and feed-down fractions to $$\mathrm{J}/\psi $$ production have a negligible dependence on the $$\mathrm{J}/\psi $$ $$p_\mathrm{T}$$ , with average values $$\lambda _\vartheta ^{\chi _{{c}1}} = 0.55 \pm 0.23$$ , $$\lambda _\vartheta ^{\chi _{{c}2}} = -0.39 \pm 0.22$$ , $$R^{\chi _{{c}1}} = (18.8 \pm 1.4)\%$$ and $$R^{\chi _{{c}2}} = (6.5 \pm 0.5)\%$$ . The analysis also shows that $$(67.2 \pm 1.9)$$ % of the prompt $$\mathrm{J}/\psi $$ yield is due to directly-produced mesons, of polarization constrained to remarkably small values, $$\lambda _\vartheta ^{\mathrm{J}/\psi } = 0.04 \pm 0.06$$ .
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"surname": "Louren\u00e7o",
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"organization": "DESY"
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"title": "From prompt to direct $$\\mathrm{J}/\\psi $$ <math><mrow><mi>J</mi><mo>/</mo><mi>\u03c8</mi></mrow></math> production: new insights on the $$\\chi _{{c}1} $$ <math><msub><mi>\u03c7</mi><mrow><mi>c</mi><mn>1</mn></mrow></msub></math> and $$\\chi _{{c}2} $$ <math><msub><mi>\u03c7</mi><mrow><mi>c</mi><mn>2</mn></mrow></msub></math> polarizations and feed-down contributions from a global-fit analysis of mid-rapidity LHC data"
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"source": "Springer",
"value": "While the prompt $$\\mathrm{J}/\\psi $$ <math><mrow><mi>J</mi><mo>/</mo><mi>\u03c8</mi></mrow></math> cross section and polarization have been measured with good precision as a function of transverse momentum, $$p_\\mathrm{T}$$ <math><msub><mi>p</mi><mi>T</mi></msub></math> , those of the directly produced $$\\mathrm{J}/\\psi $$ <math><mrow><mi>J</mi><mo>/</mo><mi>\u03c8</mi></mrow></math> are practically unknown, given that the cross sections and polarizations of the $$\\chi _{{c}1} $$ <math><msub><mi>\u03c7</mi><mrow><mi>c</mi><mn>1</mn></mrow></msub></math> and $$\\chi _{{c}2} $$ <math><msub><mi>\u03c7</mi><mrow><mi>c</mi><mn>2</mn></mrow></msub></math> mesons, large indirect contributors to $$\\mathrm{J}/\\psi $$ <math><mrow><mi>J</mi><mo>/</mo><mi>\u03c8</mi></mrow></math> production, are only known with rather poor accuracy. The lack of precise measurements of the $$\\chi _{{c}J} $$ <math><msub><mi>\u03c7</mi><mrow><mi>cJ</mi></mrow></msub></math> polarizations induces large uncertainties in the level of their feed-down contributions to the prompt $$\\mathrm{J}/\\psi $$ <math><mrow><mi>J</mi><mo>/</mo><mi>\u03c8</mi></mrow></math> yield, because of the polarization-dependent acceptance corrections. The experimental panorama of charmonium production can be significantly improved through a consistent and model-independent global analysis of existing measurements of $$\\mathrm{J}/\\psi $$ <math><mrow><mi>J</mi><mo>/</mo><mi>\u03c8</mi></mrow></math> , $$\\psi \\mathrm{(2S)}$$ <math><mrow><mi>\u03c8</mi><mrow><mo>(</mo><mn>2</mn><mi>S</mi><mo>)</mo></mrow></mrow></math> and $$\\chi _{c}$$ <math><msub><mi>\u03c7</mi><mi>c</mi></msub></math> cross sections and polarizations, faithfully respecting all the correlations and uncertainties. In particular, it is seen that the $$\\chi _{{c}J} $$ <math><msub><mi>\u03c7</mi><mrow><mi>cJ</mi></mrow></msub></math> polarizations and feed-down fractions to $$\\mathrm{J}/\\psi $$ <math><mrow><mi>J</mi><mo>/</mo><mi>\u03c8</mi></mrow></math> production have a negligible dependence on the $$\\mathrm{J}/\\psi $$ <math><mrow><mi>J</mi><mo>/</mo><mi>\u03c8</mi></mrow></math> $$p_\\mathrm{T}$$ <math><msub><mi>p</mi><mi>T</mi></msub></math> , with average values $$\\lambda _\\vartheta ^{\\chi _{{c}1}} = 0.55 \\pm 0.23$$ <math><mrow><msubsup><mi>\u03bb</mi><mi>\u03d1</mi><msub><mi>\u03c7</mi><mrow><mi>c</mi><mn>1</mn></mrow></msub></msubsup><mo>=</mo><mn>0.55</mn><mo>\u00b1</mo><mn>0.23</mn></mrow></math> , $$\\lambda _\\vartheta ^{\\chi _{{c}2}} = -0.39 \\pm 0.22$$ <math><mrow><msubsup><mi>\u03bb</mi><mi>\u03d1</mi><msub><mi>\u03c7</mi><mrow><mi>c</mi><mn>2</mn></mrow></msub></msubsup><mo>=</mo><mo>-</mo><mn>0.39</mn><mo>\u00b1</mo><mn>0.22</mn></mrow></math> , $$R^{\\chi _{{c}1}} = (18.8 \\pm 1.4)\\%$$ <math><mrow><msup><mi>R</mi><msub><mi>\u03c7</mi><mrow><mi>c</mi><mn>1</mn></mrow></msub></msup><mo>=</mo><mrow><mo>(</mo><mn>18.8</mn><mo>\u00b1</mo><mn>1.4</mn><mo>)</mo></mrow><mo>%</mo></mrow></math> and $$R^{\\chi _{{c}2}} = (6.5 \\pm 0.5)\\%$$ <math><mrow><msup><mi>R</mi><msub><mi>\u03c7</mi><mrow><mi>c</mi><mn>2</mn></mrow></msub></msup><mo>=</mo><mrow><mo>(</mo><mn>6.5</mn><mo>\u00b1</mo><mn>0.5</mn><mo>)</mo></mrow><mo>%</mo></mrow></math> . The analysis also shows that $$(67.2 \\pm 1.9)$$ <math><mrow><mo>(</mo><mn>67.2</mn><mo>\u00b1</mo><mn>1.9</mn><mo>)</mo></mrow></math> % of the prompt $$\\mathrm{J}/\\psi $$ <math><mrow><mi>J</mi><mo>/</mo><mi>\u03c8</mi></mrow></math> yield is due to directly-produced mesons, of polarization constrained to remarkably small values, $$\\lambda _\\vartheta ^{\\mathrm{J}/\\psi } = 0.04 \\pm 0.06$$ <math><mrow><msubsup><mi>\u03bb</mi><mi>\u03d1</mi><mrow><mi>J</mi><mo>/</mo><mi>\u03c8</mi></mrow></msubsup><mo>=</mo><mn>0.04</mn><mo>\u00b1</mo><mn>0.06</mn></mrow></math> ."
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