Measurement of chi(c1) (3872) production in proton-proton collisions at root s=8 and 13 TeV

Abstract

<jats:title>A<jats:sc>bstract</jats:sc> </jats:title><jats:p>The production cross-section of the <jats:italic>χ</jats:italic><jats:sub><jats:italic>c</jats:italic>1</jats:sub>(3872) state relative to the <jats:italic>ψ</jats:italic>(2<jats:italic>S</jats:italic>) meson is measured using proton-proton collision data collected with the LHCb experiment at centre-of-mass energies of <jats:inline-formula><jats:alternatives><jats:tex-math>$$ \sqrt{s} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math></jats:alternatives></jats:inline-formula> = 8 and 13 TeV, corresponding to integrated luminosities of 2.0 and 5.4 fb<jats:sup><jats:italic>−</jats:italic>1</jats:sup>, respectively. The two mesons are reconstructed in the <jats:italic>J/ψπ</jats:italic><jats:sup>+</jats:sup><jats:italic>π</jats:italic><jats:sup><jats:italic>−</jats:italic></jats:sup> final state. The ratios of the prompt and nonprompt <jats:italic>χ</jats:italic><jats:sub><jats:italic>c</jats:italic>1</jats:sub>(3872) to <jats:italic>ψ</jats:italic>(2<jats:italic>S</jats:italic>) production cross-sections are measured as a function of transverse momentum, <jats:italic>p</jats:italic><jats:sub>T</jats:sub>, and rapidity, <jats:italic>y</jats:italic>, of the <jats:italic>χ</jats:italic><jats:sub><jats:italic>c</jats:italic>1</jats:sub>(3872) and <jats:italic>ψ</jats:italic>(2<jats:italic>S</jats:italic>) states, in the kinematic range 4 <jats:italic>&lt; p</jats:italic><jats:sub>T</jats:sub><jats:italic>&lt;</jats:italic> 20 GeV/<jats:italic>c</jats:italic> and 2<jats:italic>.</jats:italic>0 <jats:italic>&lt; y &lt;</jats:italic> 4<jats:italic>.</jats:italic>5. The prompt ratio is found to increase with <jats:italic>p</jats:italic><jats:sub>T</jats:sub>, independently of <jats:italic>y</jats:italic>. For the prompt component, the double ratio of the <jats:italic>χ</jats:italic><jats:sub><jats:italic>c</jats:italic>1</jats:sub>(3872) and <jats:italic>ψ</jats:italic>(2<jats:italic>S</jats:italic>) production cross-sections between 13 and 8 TeV is observed to be consistent with unity, independent of <jats:italic>p</jats:italic><jats:sub>T</jats:sub> and centre-of-mass energy.</jats:p>