We report measurements of charm particle production asymmetries from the Fermilab photoproduction experiment E687. An asymmetry in the rate of production of charm versus anticharm particles is expected to arise primarily from fragmentation effects. We observe statistically significant asymmetries in the photoproduction of D + , D ∗+ and D 0 mesons and find small (but statistically weak) asymmetries in the production of the D s + meson and the Λ c + baryon. Our inclusive photoproduction asymmetries are compared to predictions from nonperturbative models of charm quark fragmentation.
Production asymmetry. E-gamma = 200 GeV is mean energy. Only reactions for charm particle production are present in the table. SIG(C=ANTI-CHARM) denotes the reaction with anti-charm production.
Antiparticle/particle production ratio. E-gamma = 200 GeV is mean energy. Only reactions for charm particle production are present in the table. SIG(C=ANTI-CHARM) denotes the reaction with anti-charm production.
Production asymmetry for particles produced in association with a D*(2010)+-. E-gamma = 200 GeV is mean energy. Only reactions for charm particle production are present in the table.
We have studied J ψ production in p p collisions at s = 1.8 TeV with the DØ detector at Fermilab using μ + μ − data. We have measured the inclusive J ψ production cross section as a function of J ψ transverse momentum, p T . For the kinematic range p T > 8 GeV/ c and |η| < 0.6 we obtain σ(p p → J ψ + X) · Br ( J ψ → μ + μ − ) = 2.08 ± 0.17( stat) ± 0.46(syst) nb. Using the muon impact parameter we have estimated the fraction of J ψ mesons coming from B meson decays to be f b = 0.35 ± 0.09(stat)±0.10(syst) and inferred the inclusive b production cross section. From the information on the event topology the fraction of nonisolated J ψ events has been measured to be f nonisol = 0.64 ± 0.08(stat)±0.06(syst). We have also obtained the fraction of J ψ events resulting from radiative decays of χ c states, f χ = 0.32 ± 0.07(stat)±0.07(syst). We discuss the implications of our measurements for charmonium production processes.
No description provided.
No description provided.
Integrated b-quark production cross section.
The production of $\phi$ mesons in the reaction $e~{+}p \rightarrow e~{+} \phi p$ ($\phi \rightarrow K~{+}K~{-}$) at a median $Q~{2}$ of $10~{-4} \ \rm{GeV~2}$ has been studied with the ZEUS detector at HERA. The differential $\phi$ photoproduction cross section $d\sigma/dt$ has an exponential shape and has been determined in the kinematic range $0.1<|t|<0.5 \ \rm{GeV~2}$ and $60 < W < 80 \ \rm{GeV}$. An integrated cross section of $\sigma_{\gamma p \rightarrow \phi p} = 0.96 \pm 0.19~{+0.21}_{-0.18}$ $\rm{\mu b}$ has been obtained by extrapolating to {\it t} = 0. When compared to lower energy data, the results show a weak energy dependence of both $\sigma_{\gamma p \rightarrow \phi p}$ and the slope of the $t$ distribution. The $\phi$ decay angular distributions are consistent with $s$-channel helicity conservation. From lower energies to HERA energies, the features of $\phi$ photoproduction are compatible with those of a soft diffractive process.
.
Numerical values of dsig/dt distribution requested from authors.
Numerical values of dsig/dt distribution read from plot.
The cross section for the elastic photoproduction of \r0\ mesons ($\gamma p \rightarrow \rho~0 p$) has been measured with the H1 detector at HERA for two average photon-proton centre-of-mass energies of 55 and 187GeV. TheFcenterline lower energy point was measured by observing directly the $\rho~{0}$ decay giving a cross section of $9.1\pm 0.9\,(\stat)\pm 2.5\,(\syst)\;\mu$b. The logarithmic slope parameter of the differential cross section, ${\rm d}\sigma/{\rm d}t$, is found to be $10.9 \pm 2.4\,(\stat) \pm 1.1\,(\syst)\;$GeV$~{-2}$. The \r0\ decay polar angular distribution is found to be consistent with s-channel helicity conservation. The higher energy cross section was determined from analysis of the lower part of the hadronic invariant mass spectrum of diffractive photoproduction and found to be $13.6\pm 0.8\,(\stat)\pm 2.4\,(\syst)\;\mu$b.
PI+ PI- cross section.
RHO0 cross section by selecting Mpipi to lie between 2Mpi and Mrho + 5width0.
No description provided.
A detailed study of pion production in central Mg - Mg collisions at a momentum of 4.3 GeV/c per incident nucleon was carried out using the GIBS set-up. It has been shown that the dependence of the average kinematical characteristics ( and ) of mesons on multiplicity differs from that for NN collisions at the same energy, which is due to nuclear effects. The temperatures of mesons have been estimated using two different selection criteria: in the rapidity interval and at angles in the CMS. A satisfactory fit for mesons can be achieved by using a form involving two temperatures and . The relative yield of the high-temperature component is . The results obtained by the intranuclear cascade model CASIMIR coincide with the experimental data estimated with both methods. From the analysis of angular distributions of mesons the anisotropy coefficient a was obtained. The anisotropy coefficient increases linearly with the kinetic energy (in the CMS). CASIMIR reproduces the increase of a with , but the slope is less steep than from experimental results.
The average kinematical characteristics of the PI- production.
The mean YRAP and its dispersion in various PT intervals.
No description provided.
We report on the production ofe± μ∓ pairs in 450 GeV/c pBe collisions at the CERN SPS. Theeμ signal, which has average missing energy of 21 GeV, is shown to be consistent with expectations from charm decay, and implies a σ ×B for\(c\bar c\) production in p-nucleon collisions of 0.63 ± 0.35μb. Alternatively, using an estimate of charm production from other experiments, the data imply a 95% confidence level upper limit of 1.16μb on any new physics process which producese±μ∓.
Linear A-dependence is assumed. For the first reaction the cross section times branching ratios. For the second reaction the statistical and systematic errors have been combined in quadrature.
No description provided.
The inclusive production of the f ′ 2 (1525) in hadronic Z 0 decays has been studied in data collected by the DELPHI detector at LEP. The Ring Imaging Cherenkov detectors were important tools in the identification of the decay f ′ 2 (1525) → K + K − . The average number of f ′ 2 (1525) produced per hadronic Z decay, 〈f′ 2 〉 = 0.020 ± 0.005 (stat) ± 0.006 (syst), and the momentum distribution of the f ′ 2 (1525) have both been measured. The mass and width of the f ′ 2 (1525) are found to be 〈M f′ 2 〉 = 1535 ± 5 (stat) ± 4 (syst) MeV/c 2 , (T f′ 2 ;) = 60 ± 20 (stat) ± 19 (syst) MeV/c 2
SIG in (1/SIG) is the total hadronic cross section.
No description provided.
Using data recorded by the CLEO II detector at the Cornell Electron Storage Ring, we report the first observation of an excited charmed baryon decaying into Ξc0π+. The state has mass difference M(Ξc0π+)−M(Ξc0) of 174.3±0.5±1.0MeV/c2, and a width of <3.1MeV/c2 (90% confidence level limit). We identify the new state as the Ξc*+, the isospin partner of the recently discovered Ξc*0.
CONST(NAME=EPS) is the parameter of the Peterson fragmentation function (C.Peterson et al., PR D27, 105 (1983)) D(N)/D(X) = FD(X) = const * (1/X)*1/(1- (1/X)-CONST(NAME=EPS)/(1-X))**2. Charged conjugate states are undestood.
Using the data recorded with the L3 detector at LEP, we study the process e + e − → μ + μ − ( γ ) for events with hard initial-state photon radiation. The effective centre-of-mass energies of the muons range from 50 GeV to 86 GeV. The data sample corresponds to an integrated luminosity of 103.5 pb −1 and yields 293 muon-pair events with a hard photon along the beam direction. The events are used to determine the cross sections and the forward-backward charge asymmetries at centre-of-mass energies below the Z resonance.
Here S refers to the reduced centre-of-mass energy.
Forward-Backward Asymmetry from fit as function of the reduced centre-of-mass energy.
Background corrected Forward-Backward Asymmetry as function of the reduced centre-of-mass energy.
Forum