High Energy Proton-antiproton Collisions Research Articles

Inclusive production of charged pion pairs in proton-antiproton collisions

In this study, we have considered the contribution of the higher-twist (HT) effects of the subprocesses to inclusive pion pair production cross section in the high energy proton-antiproton collisions by using various pion distribution amplitudes (DAs) within the frozen coupling constant approach and compared them with the leading-twist contributions. The feature of the HT effects may help the theoretical interpretation of the future PANDA experiment. The dependencies of the HT contribution on the transverse momentum $p_T$, the center of mass energy $\sqrt s$, and the variable $x_T$ are discussed numerically with special emphasis put on DAs. Moreover, the obtained analytical and numerical results for the differential cross section of the pion pair production are compared with the elastic backward scattering of the pion on the proton. We show that the main contribution to the inclusive cross section comes from the HT direct production process via gluon-gluon fusion. Also, it is strongly dependent on the pion DAs, momentum cut-off parameter $\triangle p$ and $<{q_{T}^2}>$ which is the mean square of the intrinsic momentum of either initial parton.

The production of charged-kaon pairs in proton–antiproton collisions: The role of higher-twist mechanism

The higher-twist (HT) contribution to the charged-kaon pair production in the high energy proton–antiproton collisions at large transverse momentum [Formula: see text] is investigated by using the frozen coupling constant approach for various kaon distribution amplitudes (DAs), which are predicted by light-cone formalism, the light-front quark model, the nonlocal chiral quark model and the light-front holographic AdS/CFT approach. In the numerics, the dependencies of the HT contribution on the transverse momentum [Formula: see text], the rapidity [Formula: see text], and the variable [Formula: see text] are discussed with special emphasis put on DAs. The HT contribution is also compared with the leading-twist ones. It is shown that the HT contributions are dependent on the kaon DAs and also some other phenomenological parameters such as momentum cutoff parameter [Formula: see text]. Inclusive kaon pair production presents a remarkable test case in which HT terms dominate those of LT in certain kinematic regions. The HT direct production process via gluon–gluon fusion contributes significantly to the inclusive cross-section at large [Formula: see text].

Track extrapolation and distribution for the CDF-II trigger system

The CDF-II experiment is a multipurpose detector designed to study a wide range of processes observed in the high energy proton–antiproton collisions produced by the Fermilab Tevatron. With event rates greater than 1 MHz, the CDF-II trigger system is crucial for selecting interesting events for subsequent analysis. This document provides an overview of the Track Extrapolation System (XTRP), a component of the CDF-II trigger system. The XTRP is a fully digital system that is utilized in the track-based selection of high momentum lepton and heavy flavor signatures. The design of the XTRP system includes five different custom boards utilizing discrete and FPGA technology residing in a single VME crate. We describe the design, construction, commissioning and operation of this system.

The top quark

Abstract The top quark has probably been found at last, produced in very high energy proton-antiproton collisions. This article reviews the history of the discovery of the six quark types and their fundamental partners, the six lepton types (electrons, neutrinos etc.).

Polarization density matrix of high- g T gauge bosons in high energy proton-antiproton collisions

We discuss the structure of the polarization density matrix of gauge bosons produced at high q T in high energy proton-antiproton collisions. First O( α s 2) results on the parity-conserving components of the polarization density matrix are reported. We calculate next-to-leading order corrections to the O( α s ) relation A 0 = A 2 between the longitudinal and transverse interference density matrix elements.

CP-tests in high-energy proton-antiproton collisions

A general analysis of CP-violating correlations forW,Z and jet production in proton-antiproton collisions is presented. We consider unpolarizedp,\(\bar p\) beams, but a polarisation analysis of the producedW's andZ's. New CP-violating interactions beyond the standard model are parametrized by an effective Lagrangian. The bounds obtainable on the parameters of this Lagrangian from measurements are discussed. Finally we point out that a particular combination of polarisation observables of theW's and theZ allows a direct determination of the gluon distribution in the proton if the quark distributions are assumed to be known.

Counting neutrino species in high-energy proton-antiproton collisions

The ratio of the cross sections sigma(pp-bar..-->..ZX)/sigma(pp-bar..-->..WX) is calculated in the framework of QCD. Although the absolute value of the cross section has large uncertainties, most of them are found to cancel in the ratio. Remaining uncertainties are studied in detail. An upper bound on the number of low-mass neutrinos is obtained. The effect of t-quark mass and fourth charged lepton is discussed.

Counting Neutrino Species at High-Energy Proton-Antiproton Collisions

Counting Neutrino Species at High-Energy Proton-Antiproton Collisions

Weak Drell-Yan processes in [formula omitted] collisions

The weak production of leptons in high energy proton-antiproton collisions is investigated using the parton model. Charged and neutral current signals are calculated both with the standard SU(2) × U(1) gauge model and with a pointlike four-fermion coupling. In addition to differential cross-sections, angular and polarization asymmetries are calculated and their significance is assessed.

Prospects for high-energy [formula omitted] beams: Study of hadronic jets and possible intermediate bosons

Predictions for large p T hadronic jets in high-energy proton-antiproton collisions, produced by strong interactions alone or through intermediate boson production and decay, and strong interactions, are calculated and compared. Two alternative models are considered for the strong interactions between partons: the phenomenological model of quark-scattering and lowest order QCD. In the last case, gluons are also taken into account as partons, with different choices of the gluon distribution inside the proton. The differential cross-sections for two-jet productions are given in the more interesting regions of the phase-space, as well as the predictions for the mean charge of the jets. Possible signatures for the detection of the W are stressed. In particular, W's could show up only for jets with p T near its maximum value. Our conclusions are mostly independent of the weak interaction model: the Weinberg-Salam one is considered for definiteness but alternative models are also discussed. The mean charge of the hadronic jets arising from either the weak or the strong interactions could be a rather distinctive tool in the search for the W. However, if gluons are present, their interactions could preponderate in the jet production mechanism and obstruct the search for intermediate bosons in the hadronic channels.