I present results for the top quark pair total cross section and the top
quark transverse momentum distribution at Tevatron and LHC energies. I also
present results for single top quark production. All calculations include NNLO
corrections from NNLL threshold resummation.Comment: 7 pages, 8 figures; presented at XIX International Workshop on
  Deep-Inelastic Scattering and Related Subjects (DIS 2011), Newport News,
  Virginia, USA, April 11-15, 201

Kidonakis, Nikolaos

English

arXiv

I present results for the top quark pair total cross section and the top quark transverse momentum distribution at Tevatron and LHC energies. I also present results for single top quark production. All calculations include NNLO corrections from NNLL threshold resummation

DigitalCommons@Kennesaw State University

Kennesaw State UniversityDigitalCommons@Kennesaw State UniversityFaculty Publications5-1-2011Top Quark Cross Sections and DifferentialDistributionsNikolaos KidonakisKennesaw State University, nkidonak@kennesaw.eduFollow this and additional works at: https://digitalcommons.kennesaw.edu/facpubsPart of the Physics CommonsThis Article is brought to you for free and open access by DigitalCommons@Kennesaw State University. It has been accepted for inclusion in FacultyPublications by an authorized administrator of DigitalCommons@Kennesaw State University. For more information, please contactdigitalcommons@kennesaw.edu.Recommended CitationKidonakis, Nikolaos, "Top Quark Cross Sections and Differential Distributions" (2011). Faculty Publications. 3870.https://digitalcommons.kennesaw.edu/facpubs/3870arXiv:1105.3481v1  [hep-ph]  17 May 2011Top quark cross sections and differential distributionsNikolaos KidonakisKennesaw State University, Physics #1202, Kennesaw, GA 30144, USAAbstractI present results for the top quark pair total cross section and the top quark transversemomentum distribution at Tevatron and LHC energies. I also present results for singletop quark production. All calculations include NNLO corrections from NNLL thresholdresummation.TOP-ANTITOP PAIR PRODUCTIONThe leading order processes for top-antitop pair production are qq¯ → tt¯ (dominant at theTevatron) and gg → tt¯ (dominant at LHC energies). The QCD corrections for top pair produc-tion are significant and receive contributions from soft-gluon corrections which are dominantnear threshold. These soft corrections have been resummed through NNLL [1], requiring two-loop calculations of the soft anomalous dimensions [1, 2]. Approximate NNLO differential-levelcross sections, using single-particle inclusive kinematics for partonic threshold, can be derivedfrom the expansion of the resummed cross section.Figures 1 and 2 show the NNLO approximate cross section [1] together with recent datafrom the corresponding experiments at the Tevatron [3, 4] and the LHC [5, 6]. The theoreticalprediction agrees well with the measured cross sections. The upper and lower curves indicatethe uncertainty from scale variation and pdf errors. It is important to note that the soft-gluonapproximation works very well not only for Tevatron but also for LHC energies because partonicthreshold is still important. There is only 1% difference between the first-order approximateand exact corrections as shown in Fig. 3, and thus less than 1% difference between NLOapproximate and exact cross sections. For our best prediction in Figs. 1 and 2 we added theNNLO approximate corrections to the exact NLO cross section. In all the results presentedhere we have used the MSTW 2008 NNLO pdf [7].At the Tevatron, we find that the NNLO corrections provide a 7.8% enhancement over NLO.For a top quark mass of 173 GeV, we findσNNLOapproxtt¯(mt = 173GeV, 1.96TeV) = 7.08+0.00−0.24+0.36−0.27 pbwhere the first uncertainty is from scale variation between mt/2 and 2mt and the second isfrom the MSTW NNLO pdf at 90% C.L. The NNLO approximate corrections reduce the scaledependence greatly over a large range; the separate factorization and renormalization scaledependence has also been calculated in [1].1165 170 175 180m (GeV)5678910σ (pb)NNLO approx+ - scale and pdfCDFD0pp -> tt   at  Tevatron      S1/2=1.96 TeV      Figure 1: Top-antitop pair cross section at the Tevatron.165 170 175 180m (GeV)100120140160180200220σ (pb)NNLO approx+ - scale and pdfATLASCMSpp -> tt   at  LHC      S1/2=7 TeV      Figure 2: Top-antitop pair cross section at the LHC.2165 170 175 180m (GeV)010203040506070σ (pb)O(αs) approx correctionsO(αs)  exact correctionspp -> tt   at  LHC      S1/2=7 TeV      µ=m qq + gg channels       first-order correctionsFigure 3: Approximate and exact NLO corrections for tt¯ production at the LHC.At the LHC at 7 TeV energy, we findσNNLOapproxtt¯ (mt = 173GeV, 7TeV) = 163+7−5+9−9 pb,which is an enhancement over NLO of 7.6%.The top quark transverse momentum distribution at the Tevatron is shown in Fig. 4. ThepT distribution is enhanced by the NNLO corrections but the shape is not significantly affected.Similar results have also been obtained for the LHC [1].In Fig. 5 we show the theoretical cross sections for tt¯ production in pp¯ and pp collisionsas functions of collider energy and corresponding Tevatron [3, 4] and LHC [5, 6] data, againnoting the agreement between theory and experiment.SINGLE TOP QUARK PRODUCTIONWe continue with single top quark production and start by discussing the t-channel pro-cesses: qb→ q′t and q¯b→ q¯′t. The t channel is numerically the largest at the Tevatron and theLHC. We find for the NNLO approximate cross section [8]σNNLOapprox, topt−channel (mt = 173GeV, 1.96TeV) = 1.04+0.00−0.02 ± 0.06 pb,σNNLOapprox, topt−channel (mt = 173GeV, 7TeV) = 41.7+1.6−0.2 ± 0.8 pb.30 50 100 150 200 250 300pT (GeV)00.010.020.030.040.050.06dσ/dp T (pb/GeV)NLO µ=mNLO  µ=m/2, 2mNNLO approx µ=mNNLO approx  µ=m/2, 2mpp -> tt   at  Tevatron      S1/2=1.96 TeV    m=173 GeV   Figure 4: Top quark pT distribution at the Tevatron.2 3 4 5 6 7 8S1/2 (TeV)110100σ (pb)NNLO approx CDFD0ATLASCMStt  cross  section  at  pp  and  pp  collidersFigure 5: Top-antitop pair cross sections in pp¯ (dash-dotted line) and pp (dashed line) collisionsversus collider energy.40 1 2 3 4 5 6 7 8 9 10 11 12 13 14S1/2 (TeV)110100σ (pb)NNLO approx+ - scale and pdf D0CDFCMSATLASt-channel single top + single antitop  cross sectionFigure 6: Single top plus single antitop t-channel cross section versus collider energy.The NNLO approximate corrections contribute a 4% increase over NLO at the Tevatron and a1% decrease at the LHC at 7 TeV.For t-channel antitop production the cross section at the Tevatron is identical to that fortop production. However, at the LHC the cross section is differentσNNLOapprox, antitopt−channel (mt = 173GeV, 7TeV) = 22.5± 0.5+0.7−0.9 pb.Figure 6 shows the combined single top plus single antitop t-channel cross section as afunction of energy together with data from the Tevatron [9, 10] and the LHC [11, 12]. Again,the theory is consistent with the measured cross sections.We continue with s-channel single top quark production: qq¯′ → b¯t, which is numericallysmall at both Tevatron and LHC energies [13]. For top production we findσNNLOapprox, tops−channel (mt = 173GeV, 1.96TeV) = 0.523+0.001−0.005+0.030−0.028 pb,σNNLOapprox, tops−channel (mt = 173GeV, 7TeV) = 3.17± 0.06+0.13−0.10 pb.The NNLO approximate corrections are an enhancement over NLO of 15% at the Tevatron and13% at the LHC. Figure 7 shows the s-channel top cross section as a function of top quarkmass at the Tevatron. The antitop cross section at the Tevatron is the same.For s-channel antitop production at the LHC we haveσNNLOapprox, antitops−channel (mt = 173GeV, 7TeV) = 1.42± 0.01+0.06−0.07 pb.5165 170 175 180mt (GeV)0.40.50.6σ  (pb)1.96 TeVSingle top Tevatron   s-channel  NNLO approx (NNLL)  µ=mtFigure 7: Single top s-channel cross section at the Tevatron.Finally, we present results for associated tW production, bg → tW− [14]. The cross sectionfor this process is very small at the Tevatron, but significant at the LHC. We find that theNNLO approximate corrections increase the NLO cross section by ∼ 8% andσNNLOapproxtW (mt = 173GeV, 7TeV) = 7.8± 0.2+0.5−0.6 pb.Figure 8 shows the tW cross section at the LHC at both 7 TeV and 14 TeV energy. We notethat the t¯W cross section is the same as that for tW production.A related process is associated charged Higgs production, bg → tH−, where the NNLOapproximate corrections increase the NLO cross section by ∼ 15 to ∼ 20% [14].ACKNOWLEDGMENTSThis work was supported by the National Science Foundation under Grant No. PHY0855421.References[1] N. Kidonakis, Phys. Rev. D 82, 114030 (2010) [arXiv:1009.4935 [hep-ph]].[2] N. Kidonakis, Phys. Rev. Lett. 102, 232003 (2009) [arXiv:0903.2561 [hep-ph]].6165 170 175 180mt (GeV)0102030405060σ  (pb)14 TeV7 TeVbg-> tW-   at LHC    NNLO approx (NNLL)    µ=mtFigure 8: tW cross section at the LHC.[3] CDF Collaboration, Conf. Note 9913.[4] D0 Collaboration, Phys. Rev. Lett. 100, 192004 (2008) [arXiv:0803.2779 [hep-ex]]; Phys.Rev. D 80, 071102(R) (2009) [arXiv:0903.5525 [hep-ex]]; Phys. Rev. D 82, 032002 (2010)[arXiv:0911.4286 [hep-ex]].[5] ATLAS Collaboration, ATLAS-CONF-2011-040.[6] CMS Collaboration, CMS-PAS-TOP-11-001.[7] A. Martin, W. Stirling, R. Thorne, and G. Watt, Eur. Phys. J. C 63, 189 (2009)[arXiv:0901.0002 [hep-ph]].[8] N. Kidonakis, Phys. Rev. D 83, 091503(R) (2011) [arXiv:1103.2792 [hep-ph]].[9] D0 Collaboration, Phys. Lett. B 682, 363 (2010) [arXiv:0907.4259 [hep-ex]].[10] CDF Collaboration, Phys. Rev. Lett. 103, 092002 (2009) [arXiv:0903.0885 [hep-ex]].[11] CMS Collaboration, CMS-PAS-TOP-10-008.[12] ATLAS Collaboration, ATLAS-CONF-2011-027.[13] N. Kidonakis, Phys. Rev. D 81, 054028 (2010) [arXiv:1001.5034 [hep-ph]].[14] N. Kidonakis, Phys. Rev. D 82, 054018 (2010) [arXiv:1005.4451 [hep-ph]].7

Top Quark Cross Sections and Differential Distributions

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Top quark cross sections and differential distributions

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