Narrow Results

Ten three-body processes in e⁺e⁻ collisions for heavy particle productions such as Higgs, t-quark, W^± and Z⁰ are calculated by two independent computer codes for automatic calculation of Feynman amplitude. The results are in excellent agreement within statistical error of numerical integration (about 0.5%). This demonstrates that these systems are quite powerful for theoretical study for future e⁺e⁻, e^±γ and γγ colliders. Numerical values of cross sections are summarized in tables and a figure.

The 1992–1995 running of the Fermilab Tevatron (the so-called Run I) ended with many important physics goals accomplished, including the discovery of the top quark, and the anticipation of many further questions to be answered in the future. After many upgrades to the detector and to the accelerator complex, Run II began in April 2001. First results obtained by the Collider Detector at Fermilab (CDF) collaboration from the analysis of early Tevatron Run II data are reported here. They fall into two categories: a number of measurements have been performed with the primary goal of establishing detector performance and physics potential. Another set of measurements make use of completely new capabilities of the upgraded detector, thus allowing for competitive results with a modest amount of integrated luminosity.

We evaluate the total cross-sections of top-charm associated production induced by SUSY–QCD FCNC at the LHC within the general unconstrained MSSM framework. Our results show that these production rates may be as large as a few pb for favorable parameter values allowing by current precise experiments. It means that the LHC may produce abundant events of this process, and the SUSY FCNC effects through the above process may be observable in the future experiments.

We review recent advances in the calculation of higher-order soft-gluon corrections for a variety of QCD, Higgs, and SUSY processes in hadron colliders. A unified approach and master formulas for next-to-next-to-leading order soft and virtual corrections are discussed. We present some applications of the formalism to top quark pair production at the Tevatron and the LHC, top production via anomalous couplings in flavor-changing neutral-current processes, W boson hadroproduction at large transverse momentum, and charged Higgs production at the LHC.

In the proton–antiproton collisions at Fermilab, individual top quarks are expected to be produced by an electroweak mechanism referred to as single-top-quark production. In this paper we review the CDF results of the search for single-top-quarks, along with the prospects for the current collider run.

We present a review of searches for electroweak production of single top quarks at the Fermilab Tevatron proton–antiproton collider at . Searches for s-channel and t-channel single top quark production have been carried out using secondary-vertex b-quark tagging and advanced event analysis methods in order to maximize the sensitivity to single top quark production. So far, no evidence for a single top quark signal has been found. However, 95% confidence level upper limits on the production cross-section have been set that improve upon previous limits by factors of two to three and are approaching the cross-section region predicted by the standard model.

The dilepton decays of the top quark are a powerful laboratory for probing the Standard Model and searching for hints of a more fundamental theory. We present a detailed analysis of the production cross section and the kinematic qualities of top quark pair candidate events in collisions at = 1.96 TeV collected by the CDF detector which include two leptons in the final state, suggesting the decay . We describe the selection of candidate events to suppress major backgrounds and present the number of observed events over background. As a test of the top quark hypothesis, the kinematics of the events are analyzed via a measurement of M_top with unprecedented precision.

We propose some empirical formulas relating the masses of the heaviest particles in the standard model (the W, Z, H bosons and the t quark) to the charge of the positron e and the Higgs condensate v. The relations for the masses of gauge bosons m_W = (1+e)v/4 and are in good agreement with experimental values. By requiring the electroweak standard model to be free from quadratic divergences at the one-loop level, we find: and , or the very simple ratio (m_t/m_H)² = e.

We investigate the degree of spin polarization of single top quarks in the eγ collision via the process with center-of-mass energies , 1 and 1.5 TeV of the parental linear e⁺e^- collider. Dominant spin fractions and spin asymmetries for the various top quark spin bases are investigated. We show that e⁺-beam direction is the favorite top quark spin decomposition axis. It is found to be comparable with the ones in pp and ep collisions.

At the Tevatron, the collider experiments CDF and DØ have data sets at their disposal that comprise a few thousand reconstructed top–antitop-quark pairs and allow for precision measurements of the cross section as well as production and decay properties. Besides comparing the measurements to standard model predictions, these data sets open a window to physics beyond the standard model. Dedicated analyses look for new heavy gauge bosons, fourth generation quarks, and flavor-changing neutral currents. In this mini-review the current status of these measurements is summarized.

The top quark is the heaviest known elementary particle. Observed for the first time in 1995 at the Tevatron by the CDF and D0 experiments, it has become object of several studies aimed to fully characterize its properties and decays. Precise determinations of top quark characteristics verify the internal consistency of the Standard Model (SM) and are sensitive to new physics phenomena. With the advent of the large top quark production rates generated at the LHC, top quark studies have reached unprecedented statistical precision. This review summarizes the recent measurements of top quark properties and studies of its decays performed at the LHC and Tevatron.

We review the status of the forward–backward asymmetry measurements in the pair production of top and antitop in proton–antiproton collisions. We also comment on the charge asymmetry in the production of the system in the proton–proton collisions.

We review the study of the charged Higgs and top quark associated production at the LHC with the presence of an additional scalar doublet. Top quark spin effects are related to the Higgs fermion couplings through this process. The angular distributions with respect to top quark spin turns out to be distinctive observables to study the Htb interaction in different models.

Recent measurements in the top quark sector at the Fermilab Tevatron collider are discussed. Measurements at the Tevatron use up to 9.7 fb^-1 of data corresponding to the full data sets recorded by each of the experiments, CDF and DØ. This review discusses the most recent measurements of inclusive and differential top quark cross-sections in strong and electroweak production of top quarks and related measurements, as well as measurements of angular distributions related to asymmetries in top quark production. Furthermore, the current status of precision measurements of the mass of the top quark is discussed. Where available, combinations of CDF and DØ results are presented.

After the Higgs boson discovery in 2012, the investigation of its properties and compatibility with the Standard Model predictions is central to the physics program of the LHC experiments. Likewise, the study of the top quark is still relevant at the LHC, more than two decades after its discovery at the Tevatron. Top quarks and Higgs bosons are produced at the LHC on a large scale and share a deep connection based on the large mass of the top quark. Both particles provide an excellent laboratory in which to search for new physics: the measurement of their properties tests the foundations of the Standard Model; and they feature prominently in a variety of exotic signals. The coupling of the Higgs boson to the top quark, a fundamental Standard Model parameter, can only be measured directly in processes where the two particles are produced together. The production of a Higgs boson together with one or two top quarks is also sensitive to several exciting new physics effects. A brief overview of the current experimental status of top quark and Higgs boson physics is presented using results from the CMS Collaboration.

The combination of the latest and most precise measurements of several top quark properties is presented in this paper in order to establish allowed regions on anomalous contributions to the Lorentz structure of the Wtb vertex. These measurements include single top production cross-sections, W boson helicity fractions and forward–backward asymmetries, both at Tevatron and at the Large Hadron Collider (LHC), up to a center-of-mass energy of 13 TeV. The results obtained at 95% Confidence Level (CL) for the top quark anomalous couplings are compared with the limits extracted from a combination that includes the expected measurements at the future High-Luminosity run of the LHC.

The measurements of the top quark flavor changing neutral current interactions are one of the most important goals of the top quark physics program in the present and the future collider experiments. These measurements provide direct information on nonstandard interactions of the top quark. Within the framework of new physics beyond the Standard Model, these interactions can be defined by an effective Lagrangian. In this study, we have investigated the potential of the future $\mu p$ colliders on the top quark flavor changing neutral current interactions through the subprocesses $\gamma q\to t\to Wb$, where $q=u,c$. These subprocesses have been produced through the main reaction $\mu p\to \mu \gamma p\to \mu WbX$ at the LHC-$\mu p$, the FCC-$\mu p$ and the SPPC-$\mu p$. For the main reaction, the total cross-sections have been calculated as a function of the anomalous $tq\gamma$ couplings. In addition, sensitivities on $\mathrm{\text{BR}}(t\to q\gamma )$ at 95% Confidence Level have been calculated. We obtain that the best constraints on $\mathrm{\text{BR}}(t\to q\gamma )$ are at the order of $10^{-7}$ which is four orders of magnitude better than the LHC’s experimental results.

Searches for Lepton Flavor Violation (LFV) stand at the forefront of experimental particle physics research, offering a sensitive probe to many scenarios of physics beyond the Standard Model. The high proton–proton collision energy and luminosity provided by the CERN Large Hadron Collider (LHC) and the excellent CMS detector performance allow for an extensive program of LFV searches. This paper reviews a broad range of LFV searches conducted at the CMS experiment using data collected in LHC Run 2, including $\tau \to 3\mu$  decays, Higgs boson decays, and top quark production and decays. In each analysis, the online and offline event selections, signal modeling, background suppression and estimation, and statistical interpretation are elucidated. These searches involve various final state particles in a large transverse momentum range, showcasing the capability of the CMS experiment in exploring fundamental questions in particle physics.

We discuss the most recent calculations of the top quark total cross section and transverse momentum distributions at the Tevatron and the LHC. These calculations include the soft-gluon corrections at next-to-next-to-leading order (NNLO). The soft NNLO corrections stabilize the scale dependence of the cross section.

We report a measurement of the production cross section using dilepton events with jets and missing transverse energy in collisions at . Using 197 pb^-1 of data recorded by the upgraded Collider Detector at Fermilab (CDF II), we use two complementary techniques to select candidate events. The combined result yields a production cross section of which is consistent with the Standard Model.