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Measurement of the ratio of prompt chi(c) to J/psi production in pp collisions at root s=7 TeV

Abstract

The prompt production of charmonium chi(c) and J/psi states is studied in proton-proton collisions at a centre-of-mass energy of root s = 7 TeV at the Large Hadron Collider. The chi(c) and J/psi mesons are identified through their decays chi(c) -> J/psi gamma and J/psi -> mu(+)mu(-) using 36 pb(-1) of data collected by the LHCb detector in 2010. The ratio of the prompt production cross-sections for chi(c) and J/psi, sigma(chi(c) -> J/psi gamma)/sigma(J/psi). is determined as a function of the J/psi, transverse momentum in the range 2 < P-T(J/psi) < 15 GeV/c. The results are in excellent agreement with next-to-leading order non-relativistic expectations and show a significant discrepancy compared with the colour singlet model prediction at leading order, especially in the low P-T(J/psi) region. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.

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Related concepts (11)

Large Hadron Collider

The Large Hadron Collider (LHC) is the world's largest and highest-energy particle collider. It was built by the European Organization for Nuclear Research (CERN) between 1998 and 2008 in collaboration with over 10,000 scientists and hundreds of universities and laboratories, as well as more than 100 countries. It lies in a tunnel in circumference and as deep as beneath the France–Switzerland border near Geneva. The first collisions were achieved in 2010 at an energy of 3.

Proton

A proton is a stable subatomic particle, symbol _Proton, H+, or 1H+ with a positive electric charge of +1 e (elementary charge). Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton-to-electron mass ratio). Protons and neutrons, each with masses of approximately one atomic mass unit, are jointly referred to as "nucleons" (particles present in atomic nuclei). One or more protons are present in the nucleus of every atom.

Proton decay

In particle physics, proton decay is a hypothetical form of particle decay in which the proton decays into lighter subatomic particles, such as a neutral pion and a positron. The proton decay hypothesis was first formulated by Andrei Sakharov in 1967. Despite significant experimental effort, proton decay has never been observed. If it does decay via a positron, the proton's half-life is constrained to be at least 1.67e34 years.

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