arXiv subjects

A. P. Heinson

Publications and source records attributed to A. P. Heinson.

16 recordsLinked to original sources

arXiv2010

Physics Beyond the Single Top Quark Observation

In March 2009, the DZero Collaboration first observed the electroweak production of single top quarks at 5 sigma significance. We measured the cross section for the combined s-channel and t-channel production modes, and set a lower limit on the CKM matrix element |V_tb|. Since then, we have used the same dataset to measure the t-channel production mode independently, the combined cross section in the hadronically-decaying tau lepton final state, and the width and lifetime of the top quark, and we have set upper limits on contributions from anomalous flavor-changing neutral currents. This paper describes these new measurements, as presented at the 3rd International Workshop on Top Quark Physics, held in Brugge, Belgium, May 31 - June 4, 2010.

hep-ex↗

arXiv2010

The D0 Silicon Microstrip Tracker

This paper describes the mechanical design, the readout chain, the production, testing and the installation of the Silicon Microstrip Tracker of the D0 experiment at the Fermilab Tevatron collider. In addition, description of the performance of the detector during the experiment data collection between 2001 and 2010 is provided.

physics.ins-det↗

arXiv2010

Observation of Single Top Quark Production at the Tevatron Collider

On March 4, 2009, the DZero and CDF collaborations at Fermilab's Tevatron Collider submitted papers to Physical Review Letters announcing observation of single top quark production. This review paper describes the successful searches carried out independently by the two collaborations, allowing the reader to see the similarities and differences that led to the simultaneous discoveries. Both collaborations measured a cross section sigma(ppbar->tb+X,tqb+X) consistent with the standard model prediction at 5.0 standard deviation significance, and set a lower limit on the quark mixing matrix element |V_tb| without assuming matrix unitarity with three quark generations.

hep-ex↗

arXiv2009

Observation of Single Top Quark Production at the Tevatron

This paper reports on the first observation of electroweak production of single top quarks by the DZero and CDF collaborations. At Fermilab's 1.96 TeV proton-antiproton collider, a few thousand events are selected from several inverse femtobarns of data that contain an isolated electron or muon and/or missing transverse energy, together with jets that originate from the decays of b quarks. Using sophisticated multivariate analyses to separate signal from background, the DZero collaboration measures a cross section sigma(ppbar->tb+X,tqb+X) = 3.94 +- 0.88 pb (for a top quark mass of 170 GeV) and the CDF collaboration measures a value of 2.3_0.6 -0.5 pb (for a top quark mass of 175 GeV). These values are consistent with theoretical predictions at next-to-leading order precision. Both measurements have a significance of 5.0 standard deviations, meeting the benchmark to be considered unambiguous observation.

hep-ex↗

arXiv2008

Single Top Quarks at the Tevatron

After many years searching for electroweak production of top quarks, the Tevatron collider experiments have now moved from obtaining first evidence for single top quark production to an impressive array of measurements that test the standard model in several directions. This paper describes measurements of the single top quark cross sections, limits set on the CKM matrix element |Vtb|, searches for production of single top quarks produced via flavor-changing neutral currents and from heavy W-prime and H+ boson resonances, and studies of anomalous Wtb couplings. It concludes with projections for future expected significance as the analyzed datasets grow.

hep-ex↗

arXiv2006

Top Quark Mass Measurements

First observed in 1995, the top quark is one of a pair of third-generation quarks in the Standard Model of particle physics. It has charge +2/3e and a mass of 171.4 GeV, about 40 times heavier than its partner, the bottom quark. The CDF and D0 collaborations have identified several hundred events containing the decays of top-antitop pairs in the large dataset collected at the Tevatron proton-antiproton collider over the last four years. They have used these events to measure the top quark's mass to nearly 1% precision and to study other top quark properties. The mass of the top quark is a fundamental parameter of the Standard Model, and knowledge of its value with small uncertainty allows us to predict properties of the as-yet-unobserved Higgs boson. This paper presents the status of the measurements of the top quark mass.

hep-ex↗

arXiv2005

Review of Recent Top Quark Measurements

At the Tevatron Collider at Fermilab, a large number of top quarks have been produced in the ongoing run. The CDF and DZero collaborations have made first measurements of the ttbar cross section in several decay channels, and have measured the top quark mass. In addition, they have set new limits on the cross sections for single top quark production, and have started to measure some of the properties of the top quark via studies of its decays. This paper summarizes the status of these measurements and discusses where they are heading in the next few years. The paper is based on a talk I gave at the Rencontres du Vietnam in Hanoi, August 2004; the results have been updated to show the latest values and new measurements.

hep-ex↗

arXiv2001

A Search for Single Top Quark Production at DZero

We present details of a search for electroweak production of single top quarks in the electron+jets and muon+jets decay channels. The measurements use \~90 pb^-1 of data from Run 1 of the Fermilab Tevatron collider, collected at 1.8 TeV with the DZero detector. We use events that include a tagging muon, implying the presence of a b jet, to set an upper limit at the 95% confidence level on the cross section for the s-channel process ppbar->tb+X of 39 pb. The upper limit for the t-channel process ppbar->tqb+X is 58 pb.

hep-ex↗

arXiv2001

Search for Electroweak Production of Single Top Quarks at DZero

This paper discusses a search for electroweak production of single top quarks in the electron+jets and muon+jets decay channels. The measurements use ~90 pb^-1 of data from Run 1 of the Fermilab Tevatron collider, collected at 1.8 TeV with the DZero detector. We use events that include a tagging muon, implying the presence of a b jet, to set an upper limit at the 95% confidence level on the cross section for the s-channel process ppbar->tb+X of 39 pb. The upper limit for the t-channel process ppbar->tqb+X is 58 pb.

hep-ex↗

arXiv1999

Recent Results on the Top Quark from the Tevatron Collider Experiments

This paper presents the latest measurements of the properties of the top quark as determined by the DZero and CDF collaborations at the Fermilab Tevatron ppbar collider. Both experiments have studied the all-hadronic decay mode of ttbar events. The top quark measurement has been refined over the past year, with the addition of new channels and a re-evaluation of some of the earlier ones. There are recent studies of the mass of the ttbar system, the helicity of the W bosons in the top quark decays, and of the correlation of the spins of the top and antitop quarks. New results are also reported on searches for charged Higgs bosons in top quark decay, and for electroweak production of single top quarks.

hep-ex↗

arXiv1998

A Compact Beam Stop for a Rare Kaon Decay Experiment

We describe the development and testing of a novel beam stop for use in a rare kaon decay experiment at the Brookhaven AGS. The beam stop is located inside a dipole spectrometer magnet in close proximity to straw drift chambers and intercepts a high-intensity neutral hadron beam. The design process, involving both Monte Carlo simulations and beam tests of alternative beam-stop shielding arrangements, had the goal of minimizing the leakage of particles from the beam stop and the resulting hit rates in detectors, while preserving maximum acceptance for events of interest. The beam tests consisted of measurements of rates in drift chambers, scintilation counter hodoscopes, a gas threshold Cherenkov counter, and a lead glass array. Measurements were also made with a set of specialized detectors which were sensitive to low-energy neutrons, photons, and charged particles. Comparisons are made between these measurements and a detailed Monte Carlo simulation.

hep-ex↗

arXiv1997

Measuring the CKM Matrix Element Vtb at DZero and CDF

I present measurements by the CDF collaboration of the Standard Model three generation CKM matrix element Vtb and of a special case extension with additional assumptions, using current Tevatron ttbar data. I then show how we can significantly improve the precision on Vtb and at the same time extend the measurement so it is not constrained by Standard Model assumptions, using single top production at the upgraded Tevatron.

hep-ex↗

arXiv1996

Single top quarks at the Fermilab Tevatron

We present a calculation of the single top quark cross section for proton-antiproton interactions with sqrt(s) = 1.8 TeV at the Fermilab Tevatron collider. We examine the effects of top mass, parton distribution functions, QCD scale, and collision energy, on each of the component production mechanisms, and study the kinematic distributions for standard model electroweak production. At the upgraded Tevatron with sqrt(s) = 2.0 TeV and high luminosity, it will be possible to test the nature of the Wtb coupling using single top production. We estimate the sensitivity to measure the single top cross section, and thus to directly measure V_tb and the top quark partial width. We show what happens to the V_tb measurement when an anomalous (V+A) component is added to the Wtb coupling, and how the top quark polarization affects the kinematic distributions.

hep-ph↗

arXiv1996

Future Top Physics at the Tevatron and LHC

Top quarks are produced at the Tevatron proton-antiproton collider at Fermilab and at the Large Hadron (proton-proton) Collider at CERN in two ways: as quark-antiquark pairs, and singly. For each mode, the cross sections and future experimental yields are presented. I then discuss some precision measurements that can be made using the anticipated large data sets. These measurements include the top quark mass, width and branching fractions, the electroweak Wtb coupling, and the CKM matrix element Vtb. Detailed studies of the top quark polarization and gluon radiation will also be possible, in addition to sensitive searches for ttbar resonances and rare decay modes.

hep-ex↗

arXiv1996

Top Quark Physics at the DZero Experiment

In this paper I present the latest results on top quark physics from the DZero collaboration since the discovery of the top quark in March 1995. I summarize the discovery results, discuss progress since the discovery, and show how we can measure the top quark mass using three separate techniques. The measurements were made at the Fermilab Tevatron, a ppbar collider with sqrt(s) = 1.8 TeV, using 50 pb^-1 data collected from 1992 to early 1995.

hep-ex↗

arXiv1995

Electroweak Top Quark Production at the Fermilab Tevatron

Top quarks can be produced from the electroweak Wtb coupling, leading to a single top or antitop in the final state. We examine single top quark production at the Fermilab Tevatron and calculate the cross section as a function of top quark mass, for each of three separate production processes. We give details of the interferences between Feynman diagrams in W-gluon fusion and then study the effects of an anomalous (V+A) term in the Wtb coupling. Using predictions for the next Tevatron run, we estimate the experimental sensitivity to the CKM matrix element V_tb as a function of the strength of the anomalous coupling.

hep-ph↗