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Register a new userDiffraction at the Tevatron and the LHC
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C. Royon
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In these lectures, we present and discuss the most recent results on inclusive diffraction at the Tevatron collider and give the prospects at the LHC. We also describe the search for exclusive events at the Tevatron. Of special interest is the exclusive production of Higgs boson and heavy objects ($W$, top, stop pairs) at the LHC which will require precise measurements and analyses of inclusive and exclusive diffraction to constrain further the gluon density in the pomeron. At the end of these lectures, we describe the projects to install forward detectors at the LHC to fulfil these measurements.
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We explore the possibility that the right-handed top quark is composite. We examine the consequences that compositeness would have on $t bar{t}$ production at the Tevatron, and derive a weak constraint on the scale of compositeness of order a few hundred GeV from the $t bar{t}$ inclusive cross section. More detailed studies of differential properties of $t bar{t}$ production could potentially improve this limit. We find that a composite top can result in an enhancement of the $t bar{t} t bar{t}$ production rate at the LHC (of as much as $10^3$ compared to the Standatd Model four top rate). We explore observables which allow us to extract the four top rate from the backgrounds, and show that the LHC can either discover or constrain top compositeness for wide ranges of parameter space.
We update the theoretical predictions for direct Y(nS) hadroproduction in the framework of NRQCD. We show that the next-to-leading order corrections in alpha_s to the color-singlet transition significantly raise the differential cross section at high pT and substantially affect the polarization of the Upsilon. Motivated by the remaining gap between the NLO yield and the cross section measurements at the Tevatron, we evaluate the leading part of the alpha_s^5 contributions, namely those coming from Y(nS) associated with three light partons. The differential color-singlet cross section at alpha_s^5 is in substantial agreement with the data, so that there is no evidence for the need of color-octet contributions. Furthermore, we find that the polarization of the Y(nS) is longitudinal. We also present our predictions for Y(nS) production at the LHC.
Inclusive bottomonium hadroproduction at the Tevatron is firstly examined in a Monte Carlo framework with the colour-octet mechanism implemented in the event generation. We extract some NRQCD colour-octet matrix elements relevant for $Upsilon(1S)$ hadroproduction. Remarkably we find a quite small contribution (compatible with zero) from feeddown of $chi_{bJ}$ states produced through the colour-octet mechanism: $Upsilon(1S)$ indirect production via $chi_{bJ}$ decays should be mainly ascribed to the colour-singlet model. Finally we extrapolate to LHC energies to predict prompt $Upsilon(1S)$ production rates.
Spin correlations of top quarks produced in hadron collisions have not been observed experimentally with large significance. In this Letter, we propose a new variable that may enable demonstration of the existence of spin correlations with 3-4 sigma significance using just a few hundred dilepton events both at the Tevatron and the LHC. Such number of dilepton events has been observed at the Tevatron. At the LHC, it will become available once integrated luminosity of a few hundred inverse picobarns is collected.
We present predictions on the total cross sections and on the ratio of the real part to the imaginary part of the elastic amplitude (rho parameter) for present and future pp and pbar p colliders, and on total cross sections for gamma p -> hadrons at cosmic-ray energies and for gamma gamma -> hadrons up to sqrt(s)=1 TeV. These predictions are based on a study of many possible analytic parametrisations and invoke the current hadronic dataset at t=0. The uncertainties on total cross sections, including the systematic theoretical errors, reach 1% at RHIC, 3% at the Tevatron, and 10% at the LHC, whereas those on the rho parameter are respectively 10%, 17%, and 26%.
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