Abstract:
The impact of recent precision measurements of DIS structure functions and inclusive jet production at the Tevatron on the global QCD analysis of parton distribution functions is studied in detail. Particular emphasis is placed on exploring the range of variation of the gluon distribution $G(x,Q)$ allowed by these new data. The strong coupling of $G(x,Q)$ with $\alpha_s$ is fully taken into account. A new generation of CTEQ parton distributions, CTEQ4, is presented. It consists of the three standard sets (\mbox{\small {$\overline {\rm MS}$}}, {\protect \small DIS} and leading order), a series that gives a range of parton distributions with corresponding $\alpha_s$'s, and a set with a low starting value of $Q$. Previously obtained gluon distributions that are consistent with the high $E_t$ jet cross-section are also discussed in the context of this new global analysis.

Abstract:
We present results from the measurement of the inclusive jet cross section for jet transverse energies from 40 to 465 GeV in the pseudo-rapidity range $0.1<|\eta|<0.7$. The results are based on 87 $pb^{-1}$ of data collected by the CDF collaboration at the Fermilab Tevatron Collider. The data are consistent with previously published results. The data are also consistent with QCD predictions given the flexibility allowed from current knowledge of the proton parton distributions. We develop a new procedure for ranking the agreement of the parton distributions with data and find that the data are best described by QCD predictions using the parton distribution functions which have a large gluon contribution at high $E_T$ (CTEQ4HJ).

Abstract:
Inclusive jet cross sections for events with a large rapidity gap with respect to the proton direction from the reaction $ep \rightarrow jet \; + \; X$ with quasi-real photons have been measured with the ZEUS detector. The cross sections refer to jets with transverse energies $E_T^{jet}>8$~GeV. The data show the characteristics of a diffractive process mediated by pomeron exchange. Assuming that the events are due to the exchange of a pomeron with partonic structure, the quark and gluon content of the pomeron is probed at a scale $\sim (E_T^{jet})^2$. A comparison of the measurements with model predictions based on QCD plus Regge phenomenology requires a contribution of partons with a hard momentum density in the pomeron. A combined analysis of the jet cross sections and recent ZEUS measurements of the diffractive structure function in deep inelastic scattering gives the first experimental evidence for the gluon content of the pomeron in diffractive hard scattering processes. The data indicate that between 30\% and 80\% of the momentum of the pomeron carried by partons is due to hard gluons.

Abstract:
Jet production is studied in the Breit frame in deep-inelastic positron-proton scattering over a large range of four-momentum transfers 5 < Q^2 < 15000 GeV^2 and transverse jet energies 7 < E_T < 60 GeV. The analysis is based on data corresponding to an integrated luminosity of L_int \simeq 33 pb^(-1) taken in the years 1995-1997 with the H1 detector at HERA at a center-of-mass energy sqrt(s)=300 GeV. Dijet and inclusive jet cross sections are measured multi-differentially using k_perp and angular ordered jet algorithms. The results are compared to the predictions of perturbative QCD calculations in next-to-leading order in the strong coupling constant alphas.QCD fits are performed in which alphas and the gluon density in the proton are determined separately. The gluon density is found to be in good agreement with results obtained in other analyses using data from different processes. The strong coupling constant is determined to be alphas(MZ)=0.1186+-0.0059. In addition an analysis of the data in which both alphas and the gluon density are determined simultaneously is presented.

Abstract:
HERA jet data, in addition to combined HERA inclusive data, are input to the HERAPDF NLO QCD analysis in order to further constrain the gluon PDF and to allow an accurate evaluation of $\alpha_S(M_Z)$

Abstract:
In the light gluino variant of the minimal supersymmetric model gluino pairs can be readily produced in collider experiments even if the squarks are arbitrarily heavy. This enhances the jet transverse energy distributions. In addition the slower running of the strong coupling constant in the presence of light gluinos leads to a further enhancement at higher transverse energies relative to the standard $QCD$ expectations. Finally, the enhanced squark gluino production would lead to a Jacobian peak in the $E_T$ distribution at about $M_{\tilde Q}/2$. These effects are of about the right magnitude to explain anomalies observed by the $CDF$ and $D0$ collaborations.

Abstract:
This contribution presents the most recent mid-rapidity inclusive jet results from 3 pb^-1 of data collected from longitudinally polarized proton collisions at sqrt(s)=200 GeV during the 2005 RHIC run. The inclusive jet asymmetry, a_LL, with it's increased transverse momentum range and precision, provides strong constraints on the gluon helicity distribution when compared with existing next-to-leading order perturbative QCD evaluations.

Abstract:
Recent measurements of high E_T jet production at the Tevatron are presented. These data provide stringent tests of perturbative QCD as well as constraints on parton distribution functions, the strong coupling constant and models implemented in event generators. Measurements of inclusive jet and multijet production as well as the associated production of jets with the electroweak bosons obtained by both the D0 and CDF collaborations are reviewed.

Abstract:
Differences between the properties of gluon and quark jets have been convincingly established by experiments at LEP. Quantitative tests of QCD analytic predictions for these differences have not been possible, however, because of differences between the theoretical and experimental definitions of the jets and event samples. Here, a new method to compare gluon and quark jet properties is described, which uses an inclusive definition of the jets in analogy to theoretical calculations. Using this new method, a value 1.552+-0.041(stat.)+-0.061(syst.) is found for the ratio of the mean charged particle multiplicity in gluon jets to that in quark jets, in agreement with a recent analytic calculation which incorporates energy conservation.

Abstract:
We study evolution of colour gluons and prove the possibility of gluon squeezed states at the nonperturbative QCD jet stage. Angular and rapidity dependences of squeezed gluon second correlation function are studied. We demonstrate that the new gluon states can have both sub-poissonian and super-poissonian statistics corresponding to antibunching and bunching of gluons.