Single Top Production Cross Section Research Articles

Recent top quark measurements with the CMS experiment

Latest results on top quark pair and single top quark production cross sections (inclusive and differential) are presented using proton-proton collision data collected by CMS. The results are used to constrain the standard model parameters. For the first time, the third row of the CKM matrix is measured from single top quark events and multidifferential cross sections are used to constrain simultaneously the top quark pole mass, α S , and PDFs. Moreover, recent results on top quark properties, such as mass measurements or constraints on top Yukawa from differential cross sections are also presented.

Top quark physics with the ATLAS detector: recent highlights

The top quark is the heaviest known fundamental particle. As it is the only quark that decays without hadronisation, it provides the unique opportunity to probe the properties of bare quarks at the Large Hadron Collider (LHC). This article will present highlights of a few recent precision measurements of the top quark using 13 TeV collision data with the ATLAS experiment. Top-quark pair and single top production cross sections, including differential distributions and production in association with bosons, will be presented alongside top quark properties measurements. Measurements of the top-quark mass and searches for rare top decays are also presented.

Top quark anomalous couplings at the high-luminosity phase of the LHC

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 s-Channel Single Top Quark Production as a Constraint for W ' Boson Contribution

An analysis is performed to constrain the W' boson production using the measurement of the s‑channel single top quark production cross section. Both phenomenological and statistical approaches are examined and results are presented. In the best case, W' bosons that interact only to the right-handed fermions are excluded below 1390 GeV. To our knowledge, it is the first time that the measured cross section of the s-channel single top quark production from the colliders is used to rule out a part of the phase space of the W' boson.

Model-independent constraints on the CKM matrix elements |Vtb|, |Vts| and |Vtd|

Single top quark production cross sections at hadron colliders are traditionally used to extract the modulus of the Vtb element of the Cabibbo-Kobayashi-Maskawa matrix under the following assumption: |Vtb| ≫ |Vtd|, |Vts|. For the first time, direct limits on |Vtd| and |Vts| are obtained using experimental data without the assumption of the unitarity of the CKM matrix. Limits on the |Vtd|, |Vts| and |Vtb| are extracted from differential measurements of single top quark cross sections in t-channel as a function of the rapidity and transverse momentum of the top quark and the light jet recoiling against the top quark. We have shown that the pseudorapidity of the forward jet in the single top production is one of the most powerful observables for discriminating between the |Vtd| and |Vtb| events. We perform a global fit of top quark related CKM elements to experimental data from the LHC Runs I and II and Tevatron. Experimental data include inclusive and differential single top cross sections in t-channel, inclusive tW production cross section, and top quark branching ratio to b quark and W boson. We present bounds on |Vtb|, |Vts| and |Vtd| using current data and project the results for future LHC data sets corresponding to luminosities of 300 and 3000 fb−1.

Highlights from the Compact Muon Solenoid (CMS) Experiment

The highlights of the recent activities and physics results leading up to the summer of 2018 from the Compact Muon Solenoid (CMS) experiment at the CERN Large Hadron Collider (LHC) are presented here. The CMS experiment has a very wide-ranging physics program, and only a very limited subset of the physics analyses being performed at CMS are discussed here, consisting of several important results from the analysis of proton-proton collision data at center-of-mass energy of 13 TeV. These include important analyses of Higgs boson physics, with the highlight being the first observation of the t t ¯ H production of the Higgs boson, along with analyses pertaining to precision standard model measurements, top quark physics, with the single top production cross-section measurement, and flavor physics, with the important observation of χ b (3P) states. Additionally, important searches for physics beyond the standard model are also presented.

Measurements of top quark production cross-section at ATLAS

Measurements of the inclusive and differential cross-sections for top quark pair and single top production cross-sections in proton-proton collisions with the ATLAS detector at the Large Hadron Collider (LHC) are presented at centre-of-mass energies of 8 TeV and 13 TeV. These measurements reach high precision and are compared to the best available theoretical calculations. The differential measurements, including results using boosted topology, probe our understanding of top quark pair production in the TeV regime. Measurements of top-quark pair with additional jets enable the study of effect of gluon radiation, especially the measurement with additional heavy flavour jets provides test of multi-scale QCD calculation. The first evidence of single top quark production in the s-channel is quoted. Interference of top quark pair and single top productions is investigated, and the single top production cross-section in association with a Z boson is measured. Measurements of the properties of the Wtb vertex in single top quark production allow to set limits on anomalous couplings.

Global constraints on top quark anomalous couplings

The latest results on top quark physics, namely single top quark production cross sections, $W$-boson helicity and asymmetry measurements are used to probe the Lorentz structure of the $Wtb$ vertex. The increase of sensitivity to new anomalous physics contributions to the top quark sector of the Standard Model is quantified by combining the relevant results from Tevatron and the Large Hadron Collider. The results show that combining an increasing set of available precision measurements in the search for new physics phenomena beyond the Standard Model leads to significant sensitivity improvements, especially when compared with the current expectation for the High Luminosity run at the LHC.

Top Quark Production Cross Section Measurements

Measurements of the inclusive and differential cross-sections for top-quark pair and single top production cross sections in proton-proton collisions with the ATLAS detector at the Large Hadron Collider are presented at centre-of-mass energies of 8 TeV and 13 TeV.The inclusive measurements reach high precision and are compared to the best available theoretical calculations. These measurements, including results using boosted tops, probe our understanding of top-pair production in the TeV regime. The results are compared to Monte Carlo generators implementing LO and NLO matrix elements matched with parton showers and NLO QCD calculations.For the t-channel single top measurement, the single top-quark and anti-top-quark total production cross-sections, their ratio, as well as differential cross sections are also presented. A measurement of the production cross section of a single top quark in association with a W boson, the second largest single-top production mode, is also presented. Finally, measurements of the properties of the Wtb vertex allow to set limits on anomalous couplings. All measurements are compared to state-of-the-art theoretical calculations.

Top quark measurements at ATLAS

The top quark is the heaviest known fundamental particle. As it is the only quark that decays before it hadronizes, it allows us to probe the properties of bare quarks at the Large Hadron Collider. Highlights of a few recent precision measurements by the ATLAS Collaboration of the top quark using 13 TeV and 8 TeV collision data will be presented: top-quark pair and single top production cross sections including differential distributions will be presented alongside measurements of top-quark properties, including results using boosted top quarks, probe our understanding of top-quark production in the TeV regime. Measurements of the top-quark mass and searches for rare top quark decays are also presented.

A general analysis of Wtb anomalous couplings**Supported by National Science Foundation of China (11275009, 11675002, 11635001), National Science Foundation (PHY-1315983, PHY-1316033) and DOE (DE- SC0011095)

We investigate new physics effects on the Wtb effective couplings in a model-independent framework. The new physics effects can be parametrized by four independent couplings, , , and . We further introduce a set of parameters x0, xm, xp and x5 which exhibit a linear relation to the single top production cross sections. Using recent data for the t-channel single top production cross section σt, tW associated production cross section σtW, s-channel single top production cross section σs, and W-helicity fractions F0, FL and FR collected at the 8 TeV LHC and Tevatron, we perform a global fit to impose constraints on the top quark effective couplings. Our global fitting results show that the top quark effective couplings are strongly correlated. We show that (i) improving the measurements of σt and σtW is important in constraining the correlation of (,) and (,); (ii) and are anti-correlated, and are sensitive to all the four experiments; (iii) and are also anti-correlated, and are sensitive to the F0 and FL measurements; (iv) the correlation between and is sensitive to the precision of the σt, σtW and F0 measurements. The effective Wtb couplings are studied in three kinds of new physics models: the G(221) = SU(2)1 ⊗ SU(2)2 ⊗ U(1)X models, the vector-like quark models and the Littlest Higgs model with and without T-parity. We show that the Wtb couplings in the left-right model and the un-unified model are sensitive to the ratio of gauge couplings when the new heavy gauge boson’s mass (MW′) is less than several hundred GeV, but the constraint is loose if MW′ > 1 TeV. Furthermore, the Wtb couplings in vector-like quark models and the Littlest Higgs models are sensitive to the mixing angles of new heavy particles and SM particles.

Highlights of top quark cross-section measurements at ATLAS

The highlights of the measurements of top quark production in proton-proton collisions at the Large Hadron Collider with the ATLAS detector are presented. The inclusive measurements of the top-pair production cross section have reached high precision and are compared to the best available theoretical calculations. The differential cross section measurements, including results using boosted top quarks, probe our understanding of top-pair production in the TeV regime. The results are compared to Monte Carlo generators implementing LO and NLO matrix elements matched with parton showers. Measurements of the single top quark production cross section are presented in the t -channel and s -channel, and with associated production with a W boson. For the t -channel production, results on the ratio between top quark and antitop quark production cross sections and differential measurements are also included.

Precision Measurements of Top Quark Production with the ATLAS Detector

The top quark is the heaviest known fundamental particle. It is the only quark that decays before it hadronises which gives us the unique opportunity to probe the properties of bare quarks and to test perturbative QCD. This overview will focus on a few recent precision top quark measurements by the ATLAS Collaboration at the LHC: Fiducial top pair and single top production cross-sections including differential distributions will be presented and compared with QCD predictions. The results include the first top quark measurements at 13 TeV using data from LHC Run 2.

New limits on anomalous contributions to theWtbvertex

The latest and most precise top quark measurements at the LHC and Tevatron are used to establish new limits on the $Wtb$ vertex. Recent results on the measurements of the $W$-boson helicity fractions and single top quark production cross section are combined in order to establish new limits at 95% CL (confidence level). The allowed regions for these limits are presented, for the first time, in three-dimensional graphics, for both real and imaginary components of the different anomalous couplings, providing a new perspective on the impact of the combination of different physics observables. These results are also combined with the prospected future measurement of the single top quark production cross section and $W$-boson helicity fractions at the LHC.

Measurement of the single top quark production cross section and|Vtb|in 1.96 TeVpp¯collisions with missing transverse energy and jets and final CDF combination

An updated measurement of the single top quark production cross section is presented using the full data set collected by the Collider Detector at Fermilab (CDF) and corresponding to 9.5 fb${}^{-1}$ of integrated luminosity from proton-antiproton collisions at 1.96 TeV center-of-mass energy. The events selected contain an imbalance in the total transverse energy, jets identified as originating from $b$ quarks, and no identified leptons. The sum of the $s$- and $t$-channel single top quark cross sections is measured to be $3.53_{-1.16}^{+1.25}$ pb and a lower limit on $V_{tb}$ of 0.63 is obtained at the 95% credibility level. These measurements are combined with previously reported CDF results obtained from events with an imbalance in total transverse energy, jets identified as originating from $b$ quarks, and exactly one identified lepton. The combined cross section is measured to be $3.02_{-0.48}^{+0.49}$ pb and a lower limit on $V{tb}$ of 0.84 is obtained at the 95% credibility level.

Top-quark production in proton–nucleus and nucleus–nucleus collisions at LHC energies and beyond

Single and pair top-quark production in proton–lead (p–Pb) and lead–lead (Pb–Pb) collisions at the CERN Large Hadron Collider (LHC) and Future Circular Collider (FCC) energies, are studied with next-to-leading-order perturbative QCD calculations including nuclear parton distribution functions. At the LHC, the pair-production cross sections amount to σtt¯=3.4 μb in Pb–Pb at sNN=5.5 TeV, and σtt¯=60 nb in p–Pb at sNN=8.8 TeV. At the FCC energies of sNN=39 and 63 TeV, the same cross sections are factors of 90 and 55 times larger respectively. In the leptonic final-state tt¯→W+bW−b¯→bb¯ℓℓνν with ℓ=e±,μ±, after typical acceptance and efficiency cuts, one expects about 90 and 300 top-quarks per nominal LHC-year and 4.7⋅104 and 105 per FCC-year in Pb–Pb and p–Pb collisions respectively. The total tt¯ cross sections, dominated by gluon fusion processes, are enhanced by 3–8% in nuclear compared to p–p collisions due to an overall net gluon antishadowing, although different regions of their differential distributions are depleted due to shadowing or EMC-effect corrections. The rapidity distributions of the decay leptons in tt¯ processes can be used to reduce the uncertainty on the Pb gluon density at high virtualities by up to 30% at the LHC (full heavy-ion programme), and by 70% per FCC-year. The cross sections for single-top production in electroweak processes are also computed, yielding about a factor of 30 smaller number of measurable top-quarks after cuts, per system and per year.

Measurement of the single top quark production cross section and |Vtb| in events with one charged lepton, large missing transverse energy, and jets at CDF.

We report a measurement of single top quark production in proton-antiproton collisions at a center-of-mass energy of sqrt[s]=1.96 TeV using a data set corresponding to 7.5 fb(-1) of integrated luminosity collected by the Collider Detector at Fermilab. We select events consistent with the single top quark decay process t→Wb→ℓνb by requiring the presence of an electron or muon, a large imbalance of transverse momentum indicating the presence of a neutrino, and two or three jets including at least one originating from a bottom quark. An artificial neural network is used to discriminate the signal from backgrounds. We measure a single top quark production cross section of 3.04(-0.53)(+0.57) pb and set a lower limit on the magnitude of the coupling between the top quark and bottom quark |Vtb|>0.78 at the 95% credibility level.

Studying theWtbvertex structure using recent LHC results

The $Wtb$ vertex structure and the search for new anomalous couplings is studied using top quark measurements obtained at the LHC, for a centre-of-mass energy of 8 TeV. By combining the latest and most precise results on the single top quark production cross section and the measurements of the $W$-boson helicity fractions ($F_0$ and $F_L$), it is possible to set new limits, at 95% CL (confidence level), on the real and imaginary components of the new couplings. The combination of the LHC observables clearly improves the limits obtained when using the individual results alone. The updated measurements of the $W$-boson helicity fractions and the $s+t$-channels electroweak single top quark production, at the Tevatron, improve the LHC limits, when a world combination of all observables (LHC+Tevatron) is performed.

On the NNLO QCD corrections to single-top production at the LHC

We present a fully-differential calculation of the NNLO QCD corrections to the t-channel mechanism for producing single top quarks at the LHC. We work in the structure function approximation, computing QCD corrections to the light- and heavy-quark lines separately and neglecting the dynamical cross-talk between the two. The neglected contribution, which appears at NNLO for the first time, is color-suppressed and is expected to be sub-dominant. Within this approximation, we find that, for the total cross section, NNLO QCD corrections are in the few percent range and, therefore, are comparable to NLO QCD corrections. We also find that the scale independence of the theoretical prediction for single-top production improves significantly once NNLO QCD corrections are included. Furthermore, we show how these results change if a cut on the transverse momentum of the top quark is applied and derive the NNLO QCD prediction for the ratio of single top and single anti-top production cross sections at the 8 TeV LHC.

Single Top Quark Measurements at the Tevatron

This paper reports the measurement of electroweak production of single top quarks in lepton plus jets final state by the DØ and CDF collaborations. At Fermilab's 1.96 TeV proton-antiproton collider, events are selected from several inverse femtobarns of data in the W+jets topology consistent with the signature of an isolated charged lepton (electron or muon), large missing transverse energy from the W boson decay and two or more jets, at least one of them is required to be identified as originating from a bottom quark. Sophisticated multivariate analysis techniques are employed to separate the small single top quark signal from background. Both experiments measure the single top production cross section in s-channel, t-channel and s + t-channel. The data is also used to extract limits on the CKM matrix element |Vtb|.