We have used 106 pb~-1 of data collected in proton-antiproton collisions at sqrt(s)=1.8 TeV by the Collider Detector at Fermilab to measure jet angular distributions in events with two jets in the final state. The angular distributions agree with next to leading order (NLO) predictions of Quantum Chromodynamics (QCD) in all dijet invariant mass regions. The data exclude at 95% confidence level (CL) a model of quark substructure in which only up and down quarks are composite and the contact interaction scale is Lambda_ud(+) < 1.6 TeV or Lambda_ud(-) < 1.4 TeV. For a model in which all quarks are composite the excluded regions are Lambda(+) < 1.8 TeV and Lambda(-) < 1. 6 TeV.
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Di-jet angular ratio, defined as the number with CHI < 2.5 divided by the number with CHI between 2.5 and 5.
The properties of high-mass multijet events produced at the Fermilab proton-antiproton collider are compared with leading order QCD matrix element predictions, QCD parton shower Monte Carlo predictions, and the predictions from a model in which events are distributed uniformly over the available multibody phase-space. Multijet distributions corresponding to (4N-4) variables that span the N-body parameter space are found to be well described by the QCD calculations for inclusive three-jet, four-jet, and five-jet events. The agreement between data, QCD Matrix Element calculations, and QCD parton shower Monte Carlo predictions suggests that 2 -> 2 scattering plus gluon radiation provides a good first approximation to the full LO QCD matrix element for events with three, four, or even five jets in the final state.
3-jet mass distribution.
Inclusive 3-jet Dalitz X3 distribution.
Inclusive 3-jet Dalitz X4 distribution.
We present a study of events with Z bosons and hadronic jets produced in $\overline{p}p$ collisions at a center-of-mass energy of 1.8 TeV. The data consist of 6708 $Z \rightarrow e~+e~-$ decays from 106 pb$~{-1}$ of integrated luminosity collected using the CDF detector at the Tevatron Collider. The Z $+ \ge n$ jet cross sections and jet production properties have been measured for n = 1 to 4. The data compare well to predictions of leading order QCD matrix element calculations with added gluon radiation and simulated parton fragmentation.
The notation (N)JET(S) means greater than or equal to N jets. Cross sections include the branching ratio to E+ E-.
Transverse energy distribution of the first highest ET jet in >= 1jet events.. Data read from plots.
Transverse energy distribution of the second highest ET jet in >= 2jet events.. Data read from plots.
A measurement of inclusive charged particle distributions in deep inelastic $ep$ scattering for $\gamma~* p$ centre-of-mass energies $75< W < 175$GeV and momentum transfer squared $10< Q~2 < 160$GeV$~2$ from the ZEUS detector at HERA is presented. The differential charged particle rates in the $\gamma~* p$ centre-of-mass system as a function of the scaled longitudinal momentum, $x_F$, and of the transverse momentum, $p_t~*$ and $<\!\!p_t~{*\,2}\!\!>\,\,$ , as a function of $x_F$, $W$ and $Q~2$ are given. Separate distributions are shown for events with (LRG) and without (NRG) a rapidity gap with respect to the proton direction. The data are compared with results from experiments at lower beam energies, with the naive quark parton model and with parton models including perturbative QCD corrections. The comparison shows the importance of the higher order QCD processes. Significant differences of the inclusive charged particle rates between NRG and LRG events at the same $W$ are observed. The value of $<\!\!p_t~{*\,2}\!\!>\,\,$ for LRG events with a hadronic mass $M_X$, which excludes the forward produced baryonic system, is similar to the $<\!\!p_t~{*\,2}\!\!>\,\,$ value observed in fixed target experiments at $W \approx M_X$.
Differential multiplicites for NRG events.. XL is parallel to the virtual photon axis.
Differential multiplicites for NRG events.. PT is relative to the virtual photon axis.
Mean PT**2 for NRG events.. PT is relative to the virtual photon axis.
The fragmentation function for the process e+e−→h+X, whereh represents a hadron, may be decomposed into transverse, longitudinal and asymmetric contributions by analysis of the distribution of polar production angles. A number of new tests of QCD have been proposed using these fragmentation functions, but so far no data have been published on the separate components. We have performed such a separation using data on charged particles from hadronic Z0 decays atOpal, and have compared the results with the predictions of QCD. By integrating the fragmentation functions, we determine the average charged particle multiplicity to be\(\overline {n_{ch} }= 21.05 \pm 0.20\). The longitudinal to total cross-section ratio is determined to be σL/σtot=0.057±0.005. From the longitudinal fragmentation function we are able to extract the gluon fragmentation function. The connection between the asymmetry fragmentation function and electroweak asymmetrics is discussed.
Transverse component of the fragmentation function.
Longitudinal component of the fragmentation function.
Asymmetry component of the fragmentation function.
Photoproduction at HERA is studied in $ep$ collisions, with the ZEUS detector, for $\gamma p$ centre-of-mass energies ranging from 130-270 GeV. A sample of events with two high-$p_T$ jets ($p_T > 6$ GeV, $\eta <1.6$) and a third cluster in the approximate direction of the electron beam is isolated using a clustering algorithm. These events are mostly due to resolved photoproduction. The third cluster is identified as the photon remnant. Its properties, such as the transverse and longitudinal energy flows around the axis of the cluster, are consistent with those commonly attributed to jets, and in particular with those found for the two jets in these events. The mean value of the photon remnant $p_T$ with respect to the beam axis is measured to be $2.1 \pm 0.2$ GeV, which demonstrates substantial mean transverse momenta for the photon remnant.
Pseudorapidity distribution of the third cluster corrected to the hadron level.
Corrected PT distribution of the third cluster corrected to the hadron level.
Corrected Energy distribution of the third cluster corrected to the hadron level.
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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Inclusive transverse momentum spectra of charged particles in photoproduction events in the laboratory pseudorapidity range $-1.2<\eta<1.4$ have been measured up to $p_{T}=8\GeV $ using the ZEUS detector. Diffractive and non--diffractive reactions have been selected with an average $\gamma p$ centre of mass (c.m.) energy of $\langle W \rangle = 180\GeV$. For diffractive reactions, the $p_{T}$ spectra of the photon dissociation events have been measured in two intervals of the dissociated photon mass with mean values $\langle M_{X} \rangle = 5$ GeV and $10$ GeV. The inclusive transverse momentum spectra fall exponentially in the low $p_{T}$ region. The non--diffractive data show a pronounced high $p_{T}$ tail departing from the exponential shape. The $p_{T}$ distributions are compared to lower energy photoproduction data and to hadron--hadron collisions at a similar c.m. energy. The data are also compared to the results of a next--to--leading order QCD calculation.
Rate of charged particle production in an average non-diffractive event.
Rate of charged particle production in an average event with a diffractively dissociated photon state of mass M(X) = 5 GeV.
Rate of charged particle production in an average event with a diffractively dissociated photon state of mass M(X) = 10 GeV.
The properties of two-, three-, four-, five-, and six-jet events with multijet masses >600 GeV /c2 are compared with QCD predictions. The shapes of the multijet-mass and leading-jet-angular distributions are approximately independent of jet multiplicity and are well described by the NJETS matrix element calculation and the HERWIG parton shower Monte Carlo predictions. The observed jet transverse momentum distributions for three- and four-jet events discriminate between the matrix element and parton shower predictions, the data favoring the matrix element calculation.
Exclusive 2-jet mass distribution.
Exclusive 3-jet mass distribution.
Exclusive 4-jet mass distribution.
We have studied the production of D*± mesons in a sample of 1.25 million multihadronic decays of the Z0, in which 1969 candidates have been identified. We have determined the total multiplicity of charged D* mesons in multihadronic Z0 decays to be
No description provided.
Multiplicity data uncorrected for decay branching ratios.
No description provided.
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