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Register a new userMeasurement of the ratio of prompt $chi_{c}$ to $J/psi$ production in $pp$ collisions at $sqrt{s}=7$ TeV
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The prompt production of charmonium $chi_{c}$ and $J/psi$ states is studied in proton-proton collisions at a centre-of-mass energy of $sqrt{s}=7$ TeV at the Large Hadron Collider. The $chi_{c}$ and $J/psi$ mesons are identified through their decays $chi_{c}rightarrow J/psi gamma$ and $J/psirightarrow mu^+mu^-$ 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 $J/psi$, $sigma (chi_{c}rightarrow J/psi gamma)/ sigma (J/psi)$, is determined as a function of the $J/psi$ transverse momentum in the range $2 < p_{mathrm T}^{J/psi} < 15$ 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 $p_{mathrm T}^{J/psi}$ region.
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The production of J/psi mesons in proton-proton collisions at sqrt(s)=7 TeV is studied with the LHCb detector at the LHC. The differential cross-section for prompt J/psi production is measured as a function of the J/psi transverse momentum pT and rapidity y in the fiducial region 0<pT<14 GeV/c and 2.0<y<4.5. The differential cross-section and fraction of J/psi from b-hadron decays are also measured in the same pT and y ranges. The analysis is based on a data sample corresponding to an integrated luminosity of 5.2pb-1. The measured cross-sections integrated over the fiducial region are 10.52 +/- 0.04 +/- 1.40 +1.64/-2.20 mub for prompt J/psi production and 1.14 +/- 0.01 +/- 0.16 mub for J/psi from b-hadron decays, where the first uncertainty is statistical and the second systematic. The prompt J/psi production cross-section is obtained assuming no J/psi polarisation and the third error indicates the acceptance uncertainty due to this assumption.
The polarizations of prompt J/psi and psi(2S) mesons are measured in proton-proton collisions at sqrt(s) = 7 TeV, using a dimuon data sample collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 4.9 inverse femtobarns. The prompt J/psi and psi(2S) polarization parameters lambda[theta], lambda[phi], and lambda[theta,phi], as well as the frame-invariant quantity lambda(tilde), are measured from the dimuon decay angular distributions in three different polarization frames. The J/psi results are obtained in the transverse momentum range 14 < pt < 70 GeV, in the rapidity intervals abs(y) < 0.6 and 0.6 < abs(y) < 1.2. The corresponding psi(2S) results cover 14 < pt < 50 GeV and include a third rapidity bin, 1.2 < abs(y) < 1.5. No evidence of large transverse or longitudinal polarizations is seen in these kinematic regions, which extend much beyond those previously explored.
An angular analysis of the decay $J/psi rightarrow mu^{+} mu^{-}$ is performed to measure the polarization of prompt $J/psi$ mesons produced in $pp$ collisions at $sqrt{s}=7; mathrm{TeV}$. The dataset corresponds to an integrated luminosity of 0.37 fb$^{-1}$ collected with the LHCb detector. The measurement is presented as a function of transverse momentum, $p_mathrm{T}$, and rapidity, $y$, of the $J/psi$ meson, in the kinematic region $2 < p_mathrm{T} < 15; mathrm{GeV}/c$ and $2.0<y<4.5$.
The production of J/psi mesons is studied with the LHCb detector using data from pp collisions at sqrt(s)=2.76 TeV corresponding to an integrated luminosity of 71 nb^-1. The differential cross-section for inclusive J/psi production is measured as a function of its transverse momentum pT. The cross-section in the fiducial region 0<pT<12 GeV/c and rapidity 2.0<y<4.5 is measured to be 5.6 +/- 0.1(stat) +/- 0.4 (syst) mub, with the assumption of unpolarised J/psi production. The fraction of J/psi production from b-hadron decays is measured to be (7.1 +/- 0.6 (stat) +/- 0.7 (syst)) %.
The production of $J/psi$ pairs in proton-proton collisions at a centre-of-mass energy of 7 TeV has been observed using an integrated luminosity of $37.5 pb^{-1}$ collected with the LHCb detector. The production cross-section for pairs with both jpsi in the rapidity range $2<y^{J/psi}<4.5$ and transverse momentum $p_{T}^{J/psi}<10 GeV/c$ is $$ sigma^{J/psi J/psi} = 5.1pm1.0pm1.1 nb,$$ where the first uncertainty is statistical and the second systematic.
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