The production of transverse energy in deep inelastic scattering is measured as a function of the kinematic variables $x$ and $Q~2$ using the H1 detector at the ep collider HERA. The results are compared to the different predictions based upon two alternative QCD evolution equations, namely the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) and the Balitsky-Fadin-Kuraev-Lipatov (BFKL) equations. In a pseudorapidity interval which is central in the hadronic centre of mass system between the current and the proton remnant fragmentation region the produced transverse energy increases with decreasing $x$ for constant $Q~2$. Such a behaviour can be explained with a QCD calculation based upon the BFKL ansatz. The rate of forward jets, proposed as a signature for BFKL dynamics, has been measured.
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Nuclear shadowing is observed in the per-nucleon cross-sections of positive muons on carbon, calcium and lead as compared to deuterium. The data were taken by Fermilab experiment E665 using inelastically scattered muons of mean incident momentum 470 GeV/c. Cross-section ratios are presented in the kinematic region 0.0001 < XBj <0.56 and 0.1 < Q**2 < 80 GeVc. The data are consistent with no significant nu or Q**2 dependence at fixed XBj. As XBj decreases, the size of the shadowing effect, as well as its A dependence, are found to approach the corresponding measurements in photoproduction.
Per-nucleon cross section ratio for carbon to deuterium.
Per-nucleon cross section ratio for calcium to deuterium.
Per-nucleon cross section ratio for lead to deuterium.
The inclusive cross sections times leptonic branching ratios for W and Z boson production in PbarP collisions at Sqrt(s)=1.8 TeV were measured using the D0 detector at the Fermilab Tevatron collider: Sigma_W*B(W->e, nu) = 2.36 +/- 0.07 +/- 0.13 nb, Sigma_W*B(W->mu,nu) = 2.09 +/- 0.23 +/- 0.11 nb, Sigma_Z*B(Z-> e, e) = 0.218 +/- 0.011 +/- 0.012 nb, Sigma_Z*B(Z->mu,mu) = 0.178 +/- 0.030 +/- 0.009 nb. The first error is the combined statistical and systematic uncertainty, and the second reflects the uncertainty in the luminosity. For the combined electron and muon analyses we find: [Sigma_W*B(W->l,nu)]/[Sigma_Z*B(Z->l,l)] = 10.90 +/- 0.49. Assuming Standard Model couplings, this result is used to determine the width of the W boson: Gamma(W) = 2.044 +/- 0.093 GeV.
The second DSYS error is due to luminosity.
The E760 Collaboration performed an experiment in the Antiproton Accumulator at Fermilab to study the two photon decay of the ηc(1 1S0) charmonium state formed in p¯p annihilations. This resulted in a new measurement of the mass Mηc=2988.3−3.1+3.3 MeV/c2 and of the product B(ηc→p¯p)×Γ(ηc→γγ) =(8.1−2.0+2.9) eV. We performed a search for the process p¯p→ηc′(2 1S0)→γγ over a limited range of center-of-mass energies. Since no signal was observed, we derived upper limits on the product of branching ratios B(ηc′→p¯p)×B(ηc′→γγ) in the center-of-mass energy range 3584≤ √s ≤3624 MeV. We observed no signal for the nonresonant process p¯+p→γ+γ and obtain upper limits.
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The cross sections for the charged current processes ${e~{-}p}\rightarrow{\nu_e+hadrons}$ and, for the first time, ${e~{+}p}\rightarrow{\overline{\nu}_e+hadrons}$ are measured at HERA for transverse momenta larger than 25 GeV.
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The cross sections for e + e − → hadrons, e + e − , μ + μ − have been measured in the vicinity of the J Ψ resonance using the BES detector operated at BEPC. The partial widths for J Ψ to hadrons, electrons, muons and the total width have been determined to be Γ h = 74.1 ± 8.1 keV, Γ e = 5.14 ± 0.39 keV, Γ μ = 5.13 ± 0.52 keV, and Γ = 84.4 ± 8.9 keV, respectively.
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This paper presents measurements of \k\ and \lam\ production in neutral current, deep inelastic scattering of 26.7 GeV electrons and 820 GeV protons in the kinematic range $ 10 < Q~{2} < 640 $ GeV$~2$, $0.0003 < x < 0.01$, and $y > 0.04$. Average multiplicities for \k\ and \lam\ production are determined for transverse momenta \ \ptr\ $> 0.5 $ GeV and pseudorapidities $\left| \eta \right| < 1.3$. The multiplicities favour a stronger strange to light quark suppression in the fragmentation chain than found in $e~+ e~-$ experiments. The production properties of \k's in events with and without a large rapidity gap with respect to the proton direction are compared. The ratio of neutral \k's to charged particles per event in the measured kinematic range is, within the present statistics, the same in both samples.
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We establish the existence of the top quark using a 67 pb^-1 data sample of Pbar-P collisions at Sqrt(s) = 1.8 TeV collected with the Collider Detector at Fermilab (CDF). Employing techniques similar to those we previously published, we observe a signal consistent with t-tbar decay to WW b-bbar, but inconsistent with the background prediction by 4.8 sigma. Additional evidence for the top quark is provided by a peak in the reconstructed mass distribution. We measure the top quark mass to be 176 +/-8(stat) +/- 10(sys.) GeV/c^2, and the t-tbar production cross section to be 6.8 +3.6 -2.4 pb.
Cross section refers to top quark mass equal 176. (+- 8 +- 10) GeV.. Error contains both statistical and systematic uncertainty.
This paper presents the first direct measurement of the $B$ meson differential cross section, $d\sigma/dp_T$, in $p\overline{p}$ collisions at $\sqrt{s}=1.8$ TeV using a sample of $19.3 \pm 0.7$ pb$~{-1}$ accumulated by the Collider Detector at Fermilab (CDF). The cross section is measured in the central rapidity region $|y| < 1$ for $p_T(B) > 6.0$ GeV/$c$ by fully reconstructing the $B$ meson decays $B~{+}\rightarrow J/\psi K~{+}$ and $B~{0}\rightarrow J/\psi K~{*0}(892)$, where $J/\psi \rightarrow \mu~+\mu~-$ and $K~{*0} \rightarrow K~+ \pi~-$. A comparison is made to the theoretical QCD prediction calculated at next-to-leading order.
Charged B meson cross section.
Average B meson cross section (including charged and neutral).
Total integrated B meson cross section above 6 GeV.
We present an analysis of data from p p¯ collisions at a center-of-mass energy of √s =1800 GeV. A measurement is made of the ratio R≡σB(p p¯→W→eν)/σB(p p¯→Z0→ee). The data represent 19.6 pg−1 collected by the Collider Detector at Fermilab during the 1992–1993 collider run of the Fermilab Tevatron. We find R=10.90±0.32(stat)±0.29(syst), and from this value we extract a measurement of the W→eν branching ratio Γ(W→eν)/Γ(W)=0.1094±0.0033(stat)±0.0031(syst). From this branching ratio we set a limit on the top quark mass of mt>62 GeV/c2 at the 95% confidence level. In contrast with direct searches for the top quark, this limit makes no assumptions about the allowed decay modes of the top quark. In addition, we use a calculation of the leptonic width Γ(W→eν) to obtain a value for the W total decay width: Γ(W)=2.064±0.060(stat)±0.059(syst) GeV.
The cross section ratio contains the branching ratio of W --> E NU and Z0 --> E+ E-. RE = PBAR P --> W+ X.
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