Search For Single Top Production Research Articles

Search for single-top production in ep collisions at HERA

A search for single-top production, ep→etX, has been performed with the ZEUS detector at HERA using data corresponding to an integrated luminosity of 0.37 fb−1. No evidence for top production was found, consistent with the expectation from the Standard Model. Limits were computed for single-top production via flavour changing neutral current transitions involving a neutral electroweak vector boson, γ or Z. The result was combined with a previous ZEUS result yielding a total luminosity of 0.50 fb−1. A 95% credibility level upper limit of 0.13 pb was obtained for the cross section at the centre-of-mass energy of s=315 GeV.

Isolated leptons and missing PT at HERA

The search for events containing isolated leptons (electrons or muons) and missing transverse momentum produced in e±p collisions is performed individually and in a common phase space with the H1 and ZEUS detectors at HERA in the period 1994-2007. The analysed H1+ZEUS data sample corresponds to an integrated luminosity of 0.97 fb-1, and composes of the complete high energy data from the HERA programme. A total of 87 events are observed in the data, compared to a Standard Model (SM) prediction of 92.7 ± 11.2. At large hadronic transverse momentum PTX > 25 GeV in the e+p data, luminosity 0.58 fb-1, 23 data events are observed compared to a SM prediction of 14.6 ± 1.9. Production cross section measurements of events containing isolated leptons and missing transverse momentum and single W production, as well as W polarisation fractions performed by the H1 Collaboration are also presented. The H1 isolated lepton events are also examined in the context of a search for single top production.

ISOLATED LEPTONS IN EVENTS WITH LARGE MISSING TRANSVERSE MOMENTUM AND THE SEARCH FOR SINGLE TOP PRODUCTION AT HERA

Recent results in searches for high transverse momentum leptons in events with large missing transverse momentum in electron–proton collisions at HERA are reviewed. These searches have implications for searches for physics beyond the Standard Model. The most recent results on searches for single top production via Flavour Changing Neutral Currents are reviewed. The consistency of results from the H1 and ZEUS collaborations and prospects of discovering new physics during the final year of HERA running are discussed.

Top Production and Properties at CDF

Recent top physics results from CDFII at a center-of-mass energy of 1.96 TeV are presented. Besides measurements of the t t ¯ production cross section in all three decay channels using a set of complementary experimental methods, we report measurements of top branching ratios as well as the W helicity and the search for single top production.

Search for single top production via FCNC at LEP atB?208BGeV

A search for single top production (e+e−→tc̄) via flavour changing neutral currents (FCNC) was performed using the data taken by the DELPHI detector at LEP2. The data analyzed have been accumulated at center-of-mass energies ranging from 189 to 208 GeV. Limits at 95% confidence level were obtained on the anomalous coupling parameters κγ and κZ.

Search for single top production via FCNC at LEP at [formula omitted]–208 GeV

A search for single top production (e+e−→tc̄) via flavour changing neutral currents (FCNC) was performed using the data taken by the DELPHI detector at LEP2. The data analyzed have been accumulated at center-of-mass energies ranging from 189 to 208 GeV. Limits at 95% confidence level were obtained on the anomalous coupling parameters κγ and κZ.

LEP search for single top production and new fermions

LEP searches for different possible extensions of the fermion sector of the Standard Model are summarised in this report. The results are based on the final LEP data sample consisting of about 600 pb −1 collected at centre-of-mass energies ranging from 130 GeV up to 209 GeV. No deviation from the Standard Model expectation is observed and constraints on the parameter space of the new physics models have been set at the 95% CL.

Search for single-top production in ep collisions at HERA

A search for single-top production, ep→etX, has been made with the ZEUS detector at HERA using an integrated luminosity of 130.1pb−1. Events from both the leptonic and hadronic decay channels of the W boson resulting from the decay of the top quark were sought. For the leptonic mode, the search was made for events with isolated high-energy leptons and significant missing transverse momentum. For the hadronic decay mode, three-jet events in which two of the jets had an invariant mass consistent with that of the W were selected. No evidence for top production was found. The results are used to constrain single-top production via flavour-changing neutral current (FCNC) transitions. The ZEUS limit excludes a substantial region in the FCNC tuγ coupling not ruled out by other experiments.

Search for single top production at LEP

Single top production in e+e− annihilations is searched for in data collected by the L3 detector at centre-of-mass energies from 189 to 209 GeV, corresponding to a total integrated luminosity of 634 pb−1. Investigating hadronic and semileptonic top decays, no evidence of single top production at LEP is obtained and upper limits on the single top cross section as a function of the centre-of-mass energy are derived. Limits on possible anomalous couplings, as well as on the scale of contact interactions responsible for single top production are determined.

Search for single top production in e+e− collisions at [formula omitted] up to 209 GeV

Single top production via the flavour changing neutral current reactions e+e−→t̄c,t̄u is searched for within the 214 pb−1 of data collected by ALEPH at centre-of-mass energies between 204 and 209 GeV. No deviation from the Standard Model expectation is observed and upper limits on the single top production cross sections are derived. The combination with data collected at lower centre-of-mass energies yields an upper limit on the branching ratio BR(t→Zc)+BR(t→Zu)<14%, for BR(t→γc)+BR(t→γu)=0 and mt=174 GeV/c2.

Search for Single Top Production with CDF

We search for Standrod Model single-top-quark production in the W -gluon fusion and W* channels using 106 pb-1 of data from [Formula: see text] collisions at [Formula: see text] collected with the Collider Detector at Fermilab. We set an upper limit at 95% C.L. on the combined Wg + W* single-top cross section of 13.5 pb, roughly five-and-a-half times larger larer than the standard model prediction. Separate 95% C.L. upper limits in the Wg-fusion and W* channels ae also determined and are found to be 13.5 and 12.9 pb respectively.