A measurement of charm and beauty dijet photoproduction cross sections at the ep collider HERA is presented. Events are selected with two or more jets of transverse momentum $p_t^{jet}_{1(2)}>11(8)$ GeV in the central range of pseudo-rapidity $-0.9<\eta^{jet}_{1(2)}<1.3$. The fractions of events containing charm and beauty quarks are determined using a method based on the impact parameter, in the transverse plane, of tracks to the primary vertex, as measured by the H1 central vertex detector. Differential dijet cross sections for charm and beauty, and their relative contributions to the flavour inclusive dijet photoproduction cross section, are measured as a function of the transverse momentum of the leading jet, the average pseudo-rapidity of the two jets and the observable $x_{\gamma}^{obs}$. Taking into account the theoretical uncertainties, the charm cross sections are consistent with a QCD calculation in next-to-leading order, while the predicted cross sections for beauty production are somewhat lower than the measurement.
Total dijet CHARM cross section in the defined kinematic range.
Total dijet BOTTOM cross section in the defined kinematic range.
Measured CHARM cross section as a function of PT.
The production of c and b quarks in gamma-gamma collisions is studied with the L3 detector at LEP with 410 pb^-1 of data, collected at centre-of-mass energies from 189 GeV to 202 GeV. Hadronic final states containing c and b quarks are identified by detecting electrons or muons from their semileptonic decays. The cross sections sigma(e+e- -> e+e- c c~ X) and sigma(e+e- -> e+e- b b~ X) are measured and compared to next-to-leading order perturbative QCD calculations. The cross section of b production is measured in gamma-gamma collisions for the first time. It is in excess of the QCD prediction by a factor of three.
Total cross section for charm production.
Total cross section for beauty production.
We have measured, with electron tagging, the forward-backward asymmetries of charm- and bottom-quark pair productions at $\langle \sqrt{s} \rangle$=58.01GeV, based on 23,783 hadronic events selected from a data sample of 197pb$~{-1}$ taken with the TOPAZ detector at TRISTAN. The measured forward-backward asymmetries are $A_{FB}~c = -0.49 \pm 0.20(stat.) \pm 0.08 (sys.)$ and $A_{FB}~b = -0.64 \pm 0.35(stat.) \pm 0.13 (sys.)$, which are consistent with the standard model predictions.
No description provided.
We report a measurement of the ratios of the decay rates of the B~+, B~0 and B~0_s mesons into exclusive final states containing a J/psi meson. The final states were selected from 19.6 pb~{-1} of p-pbar collisions recorded by the Collider Detector at Fermilab. These data are interpreted to determine the bquark fragmentation fractions f_u, f_d and f_s. We also determine the branching fractions for the decay modes B~+ --> J/psi K~+, B~+ --> J/psi K~*(892)~+, B~0 --> J/psi K~0, B~0 --> J/psi K~*(892)~0 and B_s~0 --> J/psi phi(1020). We discuss the implications of these measurements to B meson decay models.
Charge conjugated states are implied. FD is considered as a quark fragmentation fraction.
The first observation of open b production in ep collisions is reported. An event sample containing muons and jets has been selected which is enriched in semileptonic b quark decays. The visible cross section \sigma(ep -> b \bar{b}X -> \mu X') for Q^2 < 1 GeV^2, 0.1 < y < 0.8 is measured to be 0.176+-0.016(stat.)+0.026-0.017(syst.) nb for the muons to be detected in the range 35 deg < \theta^\mu < 130 deg and \pt^\mu > 2.0 GeV in the laboratory frame. The expected visible cross section based on a NLO QCD calculation is 0.104+-0.017 nb. The cross sections for electroproduction with Q^2<1 GeV^2 and photoproduction are derived from the data and found to be \sigma(ep-> e b\bar{b}X) = 7.1+-0.6(stat.)+1.5-1.3(syst.) nb and \sigma(\gamma p-> b\bar{b} X) = 111+-10(stat.)+23-20(syst.) at an average <W_{\gamma p}> \sim 180 GeV, respectively.
The visible BQ BQBAR --> MUON X cross section in the stated kinematic range.
The total electroproduction and photoproduction cross sections extrapolated to the full phase space.
We have studied c (charm) and b (bottom) quark production at the TRISTAN energy region by tagging prompt electrons from the semileptonic decays. Electrons were identified over a wide momentum range between 1 and 29 GeV/ c by a transition-radiation-detector in addition to a lead-glass calorimeter. The production cross sections of c and b quarks and the mean values of the fragmentation functions for c and b quarks were obtained as σ c = 55.9±8.8(stat.)±7.9(syst.) pb, σ b = 13.1±2.9(stat.)±1.0(syst.) pb, 〈 x c 〉 = 0.44±0.08(stat.)±0.04(syst.) and 〈 x b 〉 = 0.72±0.12(stat.)±0.08(syst.), respectively. The forward-backward asymmetries of the c and b quarks were also measured to be −0.57±0.16(stat.)±0.06(syst.) and −0.64±0.26(stat.)± 0.07(syst.), respectively. Both the cross sections and the forward-backward asymmetries of the c and b quarks are consistent with the standard model.
No description provided.
No description provided.
We report on the production characteristics and total cross section for 9 beauty hadron pairs produced by a 600 GeV/ c π − beam, the first such information in this energy region. The events were detected in the hybrid emulsion spectrometer of Fermilab Experiment E653. The measured pair cross section for all χ F , assuming linear A dependence, is 33±11 (stat.)±6(syst.) nb/nucleon. Fits of the inclusive single-hadron production distribution to the forms d σ d χ F ∝ (1−|χ F −χ 0 |) n and d σ d p T 2 ∝ exp (−bp t 2 ) give n=5.0 −2.1−1.7 +2.7+1.7 , χ 0 =0.06 −0.07−0.03 +0.06+0.02 , and b=0.13 −0.04−0.02 +0.05+0.02 ( GeV /c −2 . .The pairs tend to be produced back-to-back.
Cross section over all x assuming A**1 nuclear dependence.
Fit to data of form dsig/dx ^ (1-ABS(X-X0))**N yields X0 = 0.06 +0.06,-0.07(DSYS=+0.02,-0.03) and N = 5.0 +2.7,-2.1(DSYS=+-1.7).
Fit to data of form dsig/dPT**2 ^ exp(-B*PT**2) yields B = 0.13 +0.05,-0.04(DSYS=+-0.02).
We summarize the results obtained in the UA1 experiment on the production of bottom quarks in proton-antiproton collisions at √ s =0.63 TeV. Independent muon data samples are used to determine the bottom quark production cross section in different transverse momentum ranges from 6 to 30 GeV. A recent theoretical calculation to O(α s 3 ) of the inclusive bottom quark transverse momentum spectrum in hadronic collisions shows reasonable agreement with the data. We extrapolate the integral P T distribution to P T =0 and in rapidity to estimate the total cross section forthe production of bottom quark pairs. Assuming the shape in P T and rapidity given by the O(α s 3 ) calcultaion, we obtain σ( p p→b b +X) = 10.2 ±3.3 μb .
No description provided.
We have measured the ratio of the strong coupling constants α s for bottom quarks and light quarks at the Z 0 resonance, in order to test the flavour independence of the strong interaction. The coupling strength α s has been determined from the fraction of events with three jets, measured for a sample of all hardronic events, and for inclusive muon and electron events. The b purity is evaluated to be 22% for the first data set and 87% for the inclusive lepton sample. We find α s ( b ) α s ( udsc ) =1.00± 0.05 ( stat. )±0.06 ( syst. ) .
No description provided.
From a study of multimuon events obtained in a high luminosity proton-platinum experiment at 400 GeV/ c , we find 5 ± 4 ψψ events, which correspond to a production cross section σ ( ψψ = 27 ± 10 pb. The observed production is compared to the ψψ events previously found in the same apparatus from incoming π − ; a comparison with QCD predictions is performed, giving a good agreement with expectations from gluon-gluon fusion. Finally, using like-sign dimuon, trimuon and quadrimuon events, we give model-dependent upper limits on beauty meson production: 2 nb/nucleon for central models, 20 nb/nucleon for diffractive production.
No description provided.
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