The dijet invariant mass distribution has been measured in the region between 140 and 1000 GeV/c2, in 1.8 TeV p p¯ collisions. Data collected with the Collider Detector at Fermilab show agreement with QCD calculations. A limit on quark compositeness of Λc>1.3 TeV is obtained. Axigluons with masses between 240 and 640 GeV/c2 are excluded at 95% C.L. if we assume ten open decay channels. Model-independent limits on the production of heavy particles decaying into two jets are also presented.
No description provided.
We have measured total cross sections for the reaction π+p→π+π−p at incident pion kinetic energies of 190, 200, 220, 240, and 260 MeV. We use this result to deduce a new value of the chiral symmetry breaking parameter, ξ=-0.25±0.10, in a global constrained fit of the five ππN near-threshold amplitudes. Consequently, we report new soft pion model values for the s-wave ππ scattering lengths.
No description provided.
We present a measurement of the b-quark cross section in 1.8 TeV p-p¯ collisions recorded with the Collider Detector at Fermilab using muonic b-quark decays. In the central rapidity region (‖yb‖<1.0), the cross section is 295±21±75 nb (59±14±15 nb) for pTb>21 GeV/c (29 GeV/c). Comparisons are made to previous measurements and next-to-leading order QCD calculations.
No description provided.
We have mesured the polarization of 375-GeV/c Σ+ and Σ¯ − hyperons produced by 800-GeV/c protons incident on a Cu target. We find that the Σ+ polarization rises with increasing pt to a maximum of 16% at pt=1.0 GeV/c and then decreases to 10% at pt=1.8 GeV/c. We compare this Σ+ polarization with data at lower energies. The Σ¯ − polarization has been measured for the first time. It has the same sign as the Σ+ but smaller magnitude in a similar kinematical region.
Data from Horizontal targeting.
Data from Vertical targeting.
Data from Horizontal targeting.
We measure the Drell-Yan differential cross section d2σdMdy||y|<1 over the mass range 11
Dielectron differential cross section.
Dimuon differential cross section.
Drell-Yan differential cross section for combined dielectron and dimuon data. Error includes both statistics and systematics.
This paper reports a search for excited electrons at the HERA electron-proton collider. In a sample corresponding to an integrated luminosity of 26 nb − , no evidence was found for any resonant state decaying into e − γ , ν W − or e − Z 0 . Limits on the coupling strength of an excited electron have been determined for masses between 45 and 225 GeV. This study also reports the observation of the wide-angle e γ Compton scattering process.
No description provided.
The forward-backward asymmetries of$$e^ + e^ - \to Z^0 \to b\bar b and e^ + e^ - \to Z^0 \to c\bar c$$
Measurement of the asymmetry in b-quark production on the Z0 peak using a two parameter fit, neglecting the effects of B0-BBAR0 mixing.
Measurement of the asymmetry in b-quark production on the Z0 peak using a two parameter fit and correcting for B0-BBAR0 mixing. The second systematic error is due to the uncertainty of the mixing factor.
Measurement of the asymmetry in c-quark production on the Z0 peak using a two parameter fit.
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 the full reconstruction of χc mesons through the decay chain χc→J/ψ γ, J/ψ→μ+μ−, using data obtained at the Collider Detector at Fermilab in 2.6±0.2 pb−1 of p¯p collisions at √s =1.8 TeV. This exclusive χc sample is used to measure the χc-meson production cross section times branching fractions. We obtain σ×B=3.2±0.4(stat)−1.1+1.2(syst) nb for χc mesons decaying to J/ψ with pT>6.0 GeV/c and pseudorapidity ‖η‖<0.5. From this and the inclusive J/ψ cross section we calculate the inclusive b-quark cross section to be 12.0±4.5 μb for pTb>8.5 GeV/c and ‖yb‖<1.
No description provided.
This determination of the b-quark cross section uses an earlier CDF measurement of the pbar p --> J/PSI X cross section of 6.88 +- 1.11 nb. See Abe et al. PRL 69, 3704.
A study of the fragmentation properties of charm and bottom quarks intoD mesons is presented. From 263 700Z0 hadronic decays collected in 1991 with the DELPHI detector at the LEP collider,D0,D+ andD*+ are reconstructed in the modesK−π+,K−π+K+ andD0π+ followed byD0→K−π+, respectively. The fractional decay widths\(\Gamma {{(Z^0\to {D \mathord{\left/ {\vphantom {D {\bar D}}} \right. \kern-\nulldelimiterspace} {\bar D}}X)} \mathord{\left/ {\vphantom {{(Z^0\to {D \mathord{\left/ {\vphantom {D {\bar D}}} \right. \kern-\nulldelimiterspace} {\bar D}}X)} {\Gamma _h }}} \right. \kern-\nulldelimiterspace} {\Gamma _h }}\) are determined, and first results are presented for the production ofD mesons from\(c\bar c\) and\(b\bar b\) events separately. The average energy fraction ofD*± in charm quark fragmentation is found to be 〈XE(D*)〉c=0.487±0.015 (stat)±0.005 (sys.). Assuming that the fraction ofDs and charm-baryons produced at LEP is similar to that around 10 GeV, theZ0 partial width into charm quark pairs is determined to beΓc/Γh=0.187±0.031 (stat)±0.023 (sys). The probability for ab quark to fragment into\(\bar B_s \) orb-baryons is inferred to be 0.268±0.094 (stat)±0.100 (sys) from the measured probability that it fragments into a\(\bar B^0 \) orB−.
Using full data sample.
Using full data sample with proper time > 1 ps to enrich (b bbar) content.
Data with Delta(L) > 1.
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