We present evidence for the exclusive reaction e+e−→Ds±Ds*∓, observed with the Mark III detector at the SLAC storage ring SPEAR. The Ds± is reconstructed in the φπ± decay mode, while the Ds*∓ is detected as a narrow peak in the recoil-mass distribution. The mass of the Ds* is found to be 2109.3±2.1±3.1 MeV/c2, yielding a Ds*−Ds mass difference of 137.9±2.1±4.3 MeV/c2. The width of the Ds* is <22 MeV/c2 at the 90%-confidence level. The observed signal corresponds to σ(e+e−→Ds+Ds*−+Ds−Ds*+)B(Ds+→φπ+)=30±6±11 pb at s=4.14 GeV.
No description provided.
We present a search for electroweak production of single top quarks in $\approx 90$ $pb^{-1}$ of data collected with the DZero detector at the Fermilab Tevatron collider. Using arrays of neural networks to separate signals from backgrounds, we set upper limits on the cross sections of 17 pb for the s-channel process $p\bar{p} \to tb + X$, and 22 pb for the t-channel process $p\bar{p} \to tqb + X$, both at the 95% confidence level.
We report a new measurement of the pseudorapidity (eta) and transverse-energy (Et) dependence of the inclusive jet production cross section in pbar b collisions at sqrt(s) = 1.8 TeV using 95 pb**-1 of data collected with the DZero detector at the Fermilab Tevatron. The differential cross section d^2sigma/dEt deta is presented up to |eta| = 3, significantly extending previous measurements. The results are in good overall agreement with next-to-leading order predictions from QCD and indicate a preference for certain parton distribution functions.
Single Inclusive Jet Production Cross Section.
Single Inclusive Jet Production Cross Section.
Single Inclusive Jet Production Cross Section.
We present measurements of the b-bbar production cross section and angular correlations using the D0 detector at the Fermilab Tevatron p-pbar Collider operating at sqrt(s) = 1.8 TeV. The b quark production cross section for |y(b)|<1.0 and p_T(b)>6 GeV/c is extracted from single muon and dimuon data samples. The results agree in shape with the next-to-leading order QCD calculation of heavy flavor production but are greater than the central values of these predictions. The angular correlations between b and bbar quarks, measured from the azimuthal opening angle between their decay muons, also agree in shape with the next-to-leading order QCD prediction.
No description provided.
The distribution of MU+ MU- azimuthal angle difference.
This paper presents the first measurement of the inclusive J/Psi production cross section in the forward pseudorapidity region 2.5<|eta|<3.7 in ppbar collisions at sqrt(s)=1.8TeV. The results are based on 9.8 pb-1 of data collected using the D0 detector at the Fermilab Tevatron Collider. The inclusive J/Psi cross section for transverse momenta between 1 and 16 GeV/c is compared with theoretical models of charmonium production.
Only statistical errors are shown. Cross section tines branching ratio.
We investigate the four-photon final state produced in γγ colissions. In the π 0 π 0 channel we observe f(1270) production with predominantly helicity 2 and measure a partial width Γ γγ 2.9 +0.6 −0.4 ± keV (independent of assumptions on the helicity). We observe A 2 (1310) production in the π 0 η channel and find a partial width Γ γγ = 0.77 ± 0.18 ± 0.27 KeV (assuming helicity 2). We give an upper limit for f ≈ ηη .
Data read from graph. Systematic error on M is of order of 2% or less.
No description provided.
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.
Using 2674 nb−1 of data taken at s from 5.00 to 7.25 GeV with a trigger sensitive to decays of lower-mass particles produced in two-photon collisions, we have observed 56±12 events consistent with the reaction e+e−→e+e−η, η→γγ. Background has been subtracted using separated-beam data. We obtain Γγγ(η)=0.56±0.16 keV and the pseudoscalar-nonet mixing angle θP=−17.6°±3.6°.
No description provided.
Bottom quark production in pbar-p collisions at sqrt(s)=1.8 TeV is studied with 5 inverse picobarns of data collected in 1995 by the DO detector at the Fermilab Tevatron Collider. The differential production cross section for b jets in the central rapidity region (|y(b)| < 1) as a function of jet transverse energy is extracted from a muon-tagged jet sample. Within experimental and theoretical uncertainties, DO results are found to be higher than, but compatible with, next-to-leading-order QCD predictions.
No description provided.
We have measured the inclusive cross section for η production in e+e− interactions near charm threshold using the Crystal Ball detector. No pronounced structure in the energy dependence is observed. By comparing cross sections above and below charm threshold we obtain the limits (90% confidence limit): R(e+e−→FF¯X)RB(F→ηx)<0.15−0.32 (for Ec.m. from 4.0 to 4.5 GeV), RB(D→ηx)<0.13. Our results are inconsistent with a previous report of a large energy dependence of the η cross section ascribed to the crossing of the FF* and F*F* production thresholds.
Axis error includes +- 0.0/0.0 contribution (?////DECAY PI0 --> 2GAMMA//RES-DEF(RES=ETA,BACK=CORRECTED,DEF=340 < M( 2GAMMA ) < 800 MEV)//DECAY-BR(BRN=ETA --> 2GAMMA,BR=38 PCT)).
THE 4.028 GEV DATA ARE NOT INCLUDED IN THE 4.005-4.082 GEV BIN. Axis error includes +- 0.0/0.0 contribution (?////DECAY PI0 --> 2GAMMA//RES-DEF(RES=ETA,BACK=CORRECTED,DEF=340 < M( 2GAMMA ) < 800 MEV)//DECAY-BR(BRN=ETA --> 2GAMMA,BR=38 PCT)).
AT FIXED ENERGIES.
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