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تسجيل مستخدم جديدMeasurement of $J/psi$ polarization in $pp$ collisions at $sqrt{s}=7$ TeV
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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 $2.0<y<4.5$.
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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 rap
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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 femtobar
ns. 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.
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b detector at a centre-of-mass energy of 7 TeV. The polarisation is measured in bins of transverse momentum $p_mathrm{T}$ and rapidity $y$ in the kinematic region $3.5<p_mathrm{T}<15$ GeV$/c$ and $2.0<y<4.5$, and is compared to theoretical models. No significant polarisation is observed.
Exclusive $J/psi$ and $psi(2S)$ vector meson production has been observed in the dimuon channel using the LHCb detector. The cross-section times branching fractions to two muons with pseudorapidities between 2.0 and 4.5 are measured to be $ sigma_{pp
rightarrow J/psi (rightarrow mu^{+} mu^{-})} (2.0 <eta_{mu^{pm}}< 4.5) = 307 pm 21 pm 36 text{pb}, sigma_{pprightarrow psi(2S) (rightarrow mu^{+} mu^{-})} (2.0 <eta_{mu^{pm}}< 4.5) = 7.8 pm 1.3 pm 1.0 text{pb}, $ where the first uncertainties are statistical and the second are systematic. The measurements are found to be in good agreement with results from previous experiments and theoretical predictions. The $J/psi$ photoproduction cross-section has been measured as a function of the photon-proton centre-of-mass energy. The results are consistent with measurements obtained at HERA and confirm a similar power law behaviour for the photoproduction cross-section.
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 f
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