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.
The inclusive production of ϱ 0 mesons in pp collisions has been measured at five c.m. energies from √ s = 23.6 to 63.0 GeV. The cross sections and the production spectra as a function of transverse momentum and rapidity are discussed.
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.
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.
Inclusive production of ϱ0,f, andg0 mesons and ofKs0,K*0 (892), ϕ andK*0(1430)mesons has been measured at <y>∼2.6 and <pT>∼1.1 GeV/c in proton-proton interactions at\(\sqrt s= 52.5\) GeV. The negative particle from the two-body decays of these resonances were identified by a threshold Cerenkov counter and used for triggering. Starting from the measured differential cross section, total inclusive cross sections for the vector and tensor mesons were determined using various parametrizations for they andpT dependence of the differential cross section. The experimental results are discussed in the framework of production models based on the parton picture. The strangeness suppresion factor λ=(0.30±0.10) due toSU(3) symmetry breaking of the quark sea is derived.
The transverse-momentum spectra of lambdas (Λ0, Λ¯0) produced in the central region has been measured in p¯p collisions at s=1.8 TeV at the Fermilab Collider. We find that the average transverse momentum of the lambdas increases more rapidly with center-of-mass energy than that of charged particles, and the ratio of lambdas to charged particles increases as a function of center-of-mass energy.
The $p_{\rm T}$-differential production cross sections of the prompt (B feed-down subtracted) charmed mesons D$^0$, D$^+$, and D$^{*+}$ in the rapidity range $|y|<0.5$, and for transverse momentum $1< p_{\rm T} <12$ GeV/$c$, were measured in proton-proton collisions at $\sqrt{s} = 2.76$ TeV with the ALICE detector at the Large Hadron Collider. The analysis exploited the hadronic decays D$^0 \rightarrow $K$\pi$, D$^+ \rightarrow $K$\pi\pi$, D$^{*+} \rightarrow $D$^0\pi$, and their charge conjugates, and was performed on a $L_{\rm int} = 1.1$ nb$^{-1}$ event sample collected in 2011 with a minimum-bias trigger. The total charm production cross section at $\sqrt{s} = 2.76$ TeV and at 7 TeV was evaluated by extrapolating to the full phase space the $p_{\rm T}$-differential production cross sections at $\sqrt{s} = 2.76$ TeV and our previous measurements at $\sqrt{s} = 7$ TeV. The results were compared to existing measurements and to perturbative-QCD calculations. The fraction of cdbar D mesons produced in a vector state was also determined.
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 \begin{equation*} \sigma_{pp\rightarrow J/\psi (\rightarrow \mu^{+} \mu^{-})} (2.0 <\eta_{\mu^{\pm}}< 4.5) = 307 \pm 21 \pm 36~\text{pb}, \end{equation*} \begin{equation*} \sigma_{pp\rightarrow \psi(2S) (\rightarrow \mu^{+} \mu^{-})} (2.0 <\eta_{\mu^{\pm}}< 4.5) = 7.8 \pm 1.3 \pm 1.0~\text{pb}, \end{equation*} 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 $p_{\rm T}$-differential inclusive production cross sections of the prompt charmed mesons $D^0$, $D^+$, and $D^{*+}$ in the rapidity range |y|<0.5 were measured in proton-proton collisions at $\sqrt{s} = 7$ TeV at the LHC using the ALICE detector. Reconstructing the decays $D^0\rightarrow K^-\pi^+$, $D^+\rightarrow K^-\pi^+\pi^+$, $D^{*+}\rightarrow D^0\pi^+$, and their charge conjugates, about 8,400 $D^0$, 2,900 $D^+$, and 2,600 $D^{*+}$ mesons with 1<$p_{\rm T}$<24 GeV/$c$ were counted, after selection cuts, in a data sample of 3.14x10$^8$ events collected with a minimum-bias trigger (integrated luminosity $L_{\rm int}$ = 5/nb). The results are described within uncertainties by predictions based on perturbative QCD.