At the electron-proton collider HERA the inclusive $D~{*\pm}$ meson photoproduction cross section has been measured with the H1 detector in two different, but partly overlapping, kinematical regions. For the first, where $\langle W_{\gamma p}\rangle \approx 200$\ GeV and $Q~2 < 0.01\,\gev~2$, the result is $\sigma(\gamma p \rightarrow c \bar{c} X) = (13.2 \pm 2.2 ~{+2.1}_{-1.7}\, ~{+9.9}_{-4.8})\,\mu b$. The second measurement for $Q~2 < 4\,\gev~2$ yields $\sigma(\gamma p \rightarrow c \bar{c} X) = ( 9.3 \pm 2.1 ~{+1.9}_{-1.8}\, ~{+6.9}_ {-3.2} )\,\mu b$ at $\langle W_{\gamma p}\rangle \approx 142$\,GeV and $\sigma(\gamma p \rightarrow c \bar{c} X) = ( 20.6 \pm 5.5 ~ {+4.3}_{-3.9}\, ~{+15.4}_{-7.2})\,\mu b$ at $\langle W_{\gamma p} \rangle \approx 230$\,GeV, respectively. The third error accounts for an additional uncertainty due to the proton and photon parton density parametrizations. Differential cross sections are presented as a function of the $D~{*\pm}$ transverse momentum and rapidity. The results compare reasonably well with next-to-leading order QCD calculations. Evidence for diffractive photoproduction of charm quark is presented.
We report on measurements of the ϒ(1S), ϒ(2S), and ϒ(3S) differential, (d2σdPtdy)y=0, and integrated cross sections in pp¯ collisions at s=1.8 TeV using a sample of 16.6 ± 0.6 pb−1 collected by the Collider Detector at Fermilab. The three resonances were reconstructed through the decay ϒ→μ+μ−. Comparison is made to a leading order QCD prediction.
J/psi production has been measured in proton-proton collisions at sqrt(s)= 200 GeV over a wide rapidity and transverse momentum range by the PHENIX experiment at RHIC. Distributions of the rapidity and transverse momentum, along with measurements of the mean transverse momentum and total production cross section are presented and compared to available theoretical calculations. The total J/psi cross section is 3.99 +/- 0.61(stat) +/- 0.58(sys) +/- 0.40(abs) micro barns. The mean transverse momentum is 1.80 +/- 0.23(stat) +/- 0.16(sys) GeV/c.
Mid-rapidity open charm spectra from direct reconstruction of $D^{0}$($\bar{D^0}$)$\to K^{\mp}\pi^{\pm}$ in d+Au collisions and indirect electron/positron measurements via charm semileptonic decays in p+p and d+Au collisions at \srt = 200 GeV are reported. The $D^{0}$($\bar{D^0}$) spectrum covers a transverse momentum ($p_T$) range of 0.1 $<p_T<$ 3 \GeVc whereas the electron spectra cover a range of 1 $<p_T<$ 4 GeV/$c$. The electron spectra show approximate binary collision scaling between p+p and d+Au collisions. From these two independent analyses, the differential cross section per nucleon-nucleon binary interaction at mid-rapidity for open charm production from d+Au collisions at RHIC is $d\sigma^{NN}_{c\bar{c}}/dy$=0.30$\pm$0.04 (stat.)$\pm$0.09(syst.) mb. The results are compared to theoretical calculations. Implications for charmoniumm results in A+A collisions are discussed.
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 p_{\rm T}\ and rapidity $y$ in the fiducial region $p_{\rm T}\in[0;14]$ GeV/c and $y\in[2.0;4.5]$. The differential cross-section and fraction of \j psi\ from $b$-hadron decays are also measured in the same p_{\rm T}\ and $y$ range s. The analysis is based on a data sample corresponding to an integrated luminos ity of 5.2 pb$^{-1}$. The measured cross-sections integrated over the fiducial region are $10.52\pm 0. 04\pm 1.40^{+1.64}_{-2.20}\mu b$ for $\mathrm{prompt}~J/\psi$ production and $1.14 \pm 0. 01\pm 0.16 \mu b$ for $J/\psi$ from $b$-hadron decays, where the first uncertainty is statistical and the second systematic. The $\mathrm{prompt}~J/\psi$ production cross-section is obtained assuming no $J/\psi$ polarisation and the third error indicates the acceptance uncertainty due to this assumption.
The production cross-sections of $J/\psi$ mesons in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=5$ TeV are measured using a data sample corresponding to an integrated luminosity of $9.13\pm0.18~\text{pb}^{-1}$, collected by the LHCb experiment. The cross-sections are measured differentially as a function of transverse momentum, $p_{\text{T}}$, and rapidity, $y$, and separately for $J/\psi$ mesons produced promptly and from beauty hadron decays (nonprompt). With the assumption of unpolarised $J/\psi$ mesons, the production cross-sections integrated over the kinematic range $0<p_{\text{T}}<20~\text{GeV}/c$ and $2.0<y<4.5$ are $8.154\pm0.010\pm0.283~\mu\text{b}$ for prompt $J/\psi$ mesons and $0.820\pm0.003\pm0.034~\mu\text{b}$ for nonprompt $J/\psi$ mesons, where the first uncertainties are statistical and the second systematic. These cross-sections are compared with those at $\sqrt{s}=8$ TeV and $13$ TeV, and are used to update the measurement of the nuclear modification factor in proton-lead collisions for $J/\psi$ mesons at a centre-of-mass energy per nucleon pair of $\sqrt{s_{\text{NN}}}=5$ TeV. The results are compared with theoretical predictions.
A precision measurement of the $Z$ boson production cross-section at $\sqrt{s} = 13$ TeV in the forward region is presented, using $pp$ collision data collected by the LHCb detector, corresponding to an integrated luminosity of 5.1 fb$^{-1}$. The production cross-section is measured using $Z\rightarrow\mu^+\mu^-$ events within the fiducial region defined as pseudorapidity $2.0<\eta<4.5$ and transverse momentum $p_{T}>20$ GeV/$c$ for both muons and dimuon invariant mass $60<M_{\mu\mu}<120$ GeV/$c^2$. The integrated cross-section is determined to be $\sigma (Z \rightarrow \mu^+ \mu^-)$ = 196.4 $\pm$ 0.2 $\pm$ 1.6 $\pm$ 3.9~pb, where the first uncertainty is statistical, the second is systematic, and the third is due to the luminosity determination. The measured results are in agreement with theoretical predictions within uncertainties.
The cross-section for inclusive phi meson production in pp collisions at a centre-of-mass energy of sqrt(s) = 7 TeV has been measured with the LHCb detector at the Large Hadron Collider. The differential cross-section is measured as a function of the phi transverse momentum p_T and rapidity y in the region 0.6 < p_T < 5.0 GeV/c and 2.44 < y < 4.06. The cross-section for inclusive phi production in this kinematic range is sigma(pp -> phi X) = 1758 pm 19(stat) ^{+43}_{-14}(syst) pm 182(scale) microbarn, where the first systematic uncertainty depends on the p_T and y region and the second is related to the overall scale. Predictions based on the Pythia 6.4 generator underestimate the cross-section.
The PHENIX experiement has measured the electron-positron pair mass spectrum from 0 to 8 GeV/c^2 in p+p collisions at sqrt(s)=200 GeV. The contributions from light meson decays to e^+e^- pairs have been determined based on measurements of hadron production cross sections by PHENIX. They account for nearly all e^+e^- pairs in the mass region below 1 GeV/c^2. The e^+e^- pair yield remaining after subtracting these contributions is dominated by semileptonic decays of charmed hadrons correlated through flavor conservation. Using the spectral shape predicted by PYTHIA, we estimate the charm production cross section to be 544 +/- 39(stat) +/- 142(syst) +/- 200(model) \mu b, which is consistent with QCD calculations and measurements of single leptons by PHENIX.
J/Psi production in p+p collisions at sqrt(s) = 200 GeV has been Measured in the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) over a rapidity range of -2.2 < y < 2.2 and a transverse momentum range of 0 < pT < 9 GeV/c. The statistics available allow a detailed measurement of both the pT and rapidity distributions and are sufficient to constrain production models. The total cross section times branching ratio determined for J/Psi production is B_{ll} sigma_pp^J/psi = 178 +/- 3(stat) +/- 53(syst) +/- 18(norm) nb.
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