I present results for single-top and top-pair production at the LHC and the
Tevatron. Higher-order two-loop corrections are used to achieve NNLL
resummation, which is then used to derive NNLO soft-gluon corrections. Results
are presented for total cross sections, top transverse momentum distributions,
and top rapidity distributions. All results are in excellent agreement with
data from the LHC and the Tevatron. I also clarify the differences between
various methods in top-pair production and their relation to exact NNLO
results.Comment: 6 pages, 5 figures; Proceedings of CKM 2012, the 7th International
  Workshop on the CKM Unitarity Triangle, Cincinnati, Ohio, USA, 28 September -
  2 October 201

Kidonakis, Nikolaos

English

arXiv

I present results for single-top and top-pair production at the LHC and the Tevatron. Higher-order two-loop corrections are used to achieve NNLL resummation, which is then used to derive NNLO soft-gluon corrections. Results are presented for total cross sections, top transverse momentum distributions, and top rapidity distributions. All results are in excellent agreement with data from the LHC and the Tevatron. I also clarify the differences between various methods in top-pair production and their relation to exact NNLO results

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Kennesaw State UniversityDigitalCommons@Kennesaw State UniversityFaculty Publications12-1-2012Single Top and Top Pair ProductionNikolaos 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, "Single Top and Top Pair Production" (2012). Faculty Publications. 3863.https://digitalcommons.kennesaw.edu/facpubs/3863arXiv:1212.2844v1  [hep-ph]  12 Dec 2012Single top and top pair productionNikolaos KidonakisKennesaw State UniversityKennesaw, GA 30144, USA1 IntroductionI present results for single-top and top-pair production at the LHC and the Tevatron.Higher-order two-loop corrections are used to achieve NNLL resummation, which isthen used to derive NNLO soft-gluon corrections. Results are presented for total crosssections, top transverse momentum distributions, and top rapidity distributions. Allresults are in excellent agreement with data from the LHC and the Tevatron. Ialso clarify the differences between various methods in top-pair production and theirrelation to exact NNLO results.The LO partonic processes for single-top production are qb → q′t and qb → q′t,i.e. the t channel, dominant at the Tevatron and the LHC; qq′ → bt, i.e. the s chan-nel, numerically small at the Tevatron and the LHC; and associated tW production,bg → tW−, very small at the Tevatron but significant at the LHC. The LO partonicprocesses for top-pair production are qq → tt, dominant at the Tevatron; and gg → tt,dominant at the LHC.QCD corrections are significant for single top and top pair production. Soft-gluoncorrections from emission of soft (low-energy) gluons appear as lnk(s4/m2)/s4, withk ≤ 2n− 1 and s4 the distance from threshold, and are dominant near threshold. Weresum these soft corrections using factorization and renormalization-group evolution.Complete results are available at NNLL using two-loop soft anomalous dimensionsfor both top-pair [1, 2] and single-top production [3, 4, 5]. Approximate NNLO dif-ferential cross sections are derived from the expansion of the resummed cross section;see Ref. [6] for the newest results. This is the only calculation using the standardmoment-space resummation in pQCD for partonic threshold at the double-differentialcross section level. The soft-gluon approximation works very well for both Tevatronand LHC energies; there is less than 1% difference between NLO approximate andexact cross sections, and similarly for differential distributions [6].Proceedings of CKM 2012, the 7th International Workshop on the CKM Unitarity Triangle,Cincinnati, Ohio, USA, 28 September - 2 October 201212 Single top production1 2 3 4 5 6 7 8 9 10 11 12 13 14S1/2 (TeV)110100σ (pb)NNLO approx+ - scale and pdf D0CDFCMSATLASt-channel total  cross section      mt=172.5 GeV20 40 60 80 100 120 140pT (GeV)00.20.40.60.8dσ/dp T (pb/GeV)8 TeV top7 TeV top8 TeV antitop7 TeV antitopt-channel top/antitop pT distributions at LHC   µ=mt=173 GeV   NNLO approx (NNLL)Figure 1: Single-top t-channel cross sections (left) and pT distributions (right).We begin with the t channel. On the left plot of Fig. 1 we show the totalapproximate NNLO t-channel cross section versus collider energy with mt = 172.5GeV and MSTW2008 pdf [7] and compare it with recent Tevatron [8, 9] and LHC[10, 11] data. The agreement between theory and experiment is very good. Thet-channel top and antitop pT distributions at the LHC are shown in the right plot.Table 1 shows the separate single-top and single-antitop t-channel cross sectionsand their sum at 7 and 8 TeV LHC energy for mt = 173 GeV. The ratio σ(t)/σ(t) =1.88+0.11−0.09 at 7 TeV, which compares well with the ATLAS result 1.81+0.23−0.22 [12].For the s-channel, the total cross sections (single top+antitop) at the LHC withmt = 173 GeV are 4.56± 0.07+0.18−0.17 pb at 7 TeV and 5.55± 0.08± 0.21 pb at 8 TeV.At the Tevatron at 1.96 TeV formt = 173 GeV, the t-channel total (single top andsingle antitop) cross section is 2.08+0.00−0.04±0.12 pb; the s-channel total is 1.05+0.00−0.01±0.06pb; and the sum of the two channels is 3.13+0.00−0.05 ± 0.18 pb. The sum of the t- ands-channel cross sections at the Tevatron is plotted in the left plot of Fig. 2 as afunction of mt and compared with CDF [8] and D0 [9] data.For associated tW− production at the LHC with mt = 173 GeV, the cross sectionLHC t t Total (pb)7 TeV 43.0+1.6−0.2 ± 0.8 22.9± 0.5+0.7−0.9 65.9+2.1−0.7+1.5−1.78 TeV 56.4+2.1−0.3 ± 1.1 30.7± 0.7+0.9−1.1 87.2+2.8−1.0+2.0−2.2Table 1: t-channel cross sections ± scale ± pdf errors for mt = 173 GeV withMSTW2008 NNLO 90% CL pdf [7].2165 170 175 180mt (GeV)1.522.533.544.55σ  (pb)NNLO approx+- scale and pdfD0CDFt+s channels total     Tevatron     S1/2= 1.96 TeV2 3 4 5 6 7 8 9 10 11 12 13 14S1/2 (TeV)110100σ (pb)NNLO approx+- scale&pdfCMSATLAStW- + tW+ cross section      mt=172.5 GeVFigure 2: Single-top t- plus s-channel (left) and tW (right) cross sections.at 7 TeV is 7.8± 0.2+0.5−0.6 pb and at 8 TeV it is 11.1± 0.3± 0.7 pb. The cross sectionfor tW+ production is identical. In the right plot of Fig. 2 we display the total tW−plus tW+ cross section with mt = 172.5 GeV versus LHC energy and compare it withrecent ATLAS [13] and CMS [14] results - the agreement is excellent.3 Top pair production165 170 175 180mt (GeV)100120140160180200220σ (pb)NNLO approx+- scale and pdfCMSATLASpp -> tt    at   LHC         S1/2= 7 TeV165 170 175 180mt (GeV)160180200220240260280300320340σ (pb)NNLO approx+- scale and pdfCMSpp -> tt    at   LHC       S1/2= 8 TeVFigure 3: Top pair cross sections at the LHC at 7 TeV (left) and 8 TeV (right).The total tt cross section with mt = 173 GeV at the LHC is 163+7−5 ± 9 pb at 7TeV; and 234+10−7 ± 12 pb at 8 TeV. Figure 3 shows the cross section as a function ofmt at 7 TeV (left) and 8 TeV (right) together with LHC data [15, 16]. The agreementof theory with experiment is very good and the uncertainties are similar.3165 170 175 180mt (GeV)5678910σ (pb)NNLO approx+ - scale and pdfCDFD0pp -> tt   at  Tevatron      S1/2=1.96 TeV      0 50 100 150 200 250 300 350 400pT (GeV)020406080dσ/dp T (fb/GeV)D0---- NNLO approx  mt/2<µ<2mt- . -  NLO Top quark pT at  Tevatron      S1/2=1.96 TeV    mt=170 GeV   200 250 300 350 4000.1110Figure 4: Top pair cross sections (left) and top pT distributions (right) at Tevatron.The tt cross section at the Tevatron at 1.96 TeV is 7.08+0.00−0.24+0.36−0.27 pb for mt = 173GeV. The left plot of Fig. 4 shows the cross section and compares it to Tevatron data[17, 18]. The right plot shows the top pT distribution together with D0 data [19].Again the agreement of theory and experiment is excellent.The resummation approaches that have appeared in [1, 20, 21, 22] differ fromeach other in many respects. Differences include the use of moment-space pQCD[1, 20] versus SCET [21, 22]; doing the resummation for the double-differential crosssection [1, 21] versus for the total cross section only [20, 22]; inclusion of subleadingterms, etc. More discussion can be found in [6, 23]. All results presented in thispaper are approximate NNLO from moment-space NNLL resummation for the double-differential cross section in single-particle-inclusive (1PI) kinematics.The result of Ref. [1] is very close to the partially exact NNLO (exact for qq plusapproximate for gg) of [24] at Tevatron energy: 7.08 vs 7.07 pb, with similar scaleuncertainty. It is claimed in [24] that the threshold approximation is not very good;however that only applies to the resummation method used in [24]. As discussed indetail in [6] and in [23], the various resummation formalisms are both numericallyand theoretically very different. Thus, the claim in [24] does not necessarily apply toother methods, and it is most certainly irrelevant to the method used here; as shownexplicitly in [6] and previous work, the method that we use here provides an excellentapproximation (less that 1% difference between exact and approximate results bothat NLO and at NNLO), which is significantly better than in [24]. This was expectedfrom the study of 1PI and PIM results in [25] (see also discussion in [1, 6, 26]). Adouble-differential calculation for partonic (not absolute) threshold as used here andin [1, 2, 6] has a lot more theoretical/analytical information (also useful for derivingdistributions) and potential for numerical accuracy than one for the total cross sectiononly as used in [24]. This is a point often misunderstood and not emphasized in the4literature. We also note that once NNLO is fully known, the next step will be to addthe approximate NNNLO corrections (see [27] for some early NNNLO results).0 50 100 150 200 250 300 350 400pT (GeV)00.0020.0040.0060.0081/σ  dσ/dp T (GeV-1 )  NNLO  approx             +- scale+ CMS l+jetsNormalized top pT distribution at LHC   S1/2=7 TeV  mt=173 GeV   -3 -2 -1 0 1 2 3Y00.10.20.30.41/σ  dσ/dYNNLO  approx          +- scaleCMS dileptonsNormalized top Y distribution at LHC   S1/2=7 TeV  mt=173 GeV   Figure 5: Top-quark pT (left) and rapidity (right) distributions at the LHC.The normalized top quark pT distribution at the LHC is shown in the left plotof Fig. 5 while the normalized top quark rapidity distribution is shown on the right.Both distributions predict very well the CMS results [28], also shown on the plots.This material is based upon work supported by the National Science Foundationunder Grant No. PHY 1212472.References[1] N. Kidonakis, Phys. Rev. D 82, 114030 (2010) [arXiv:1009.4935 [hep-ph]].[2] N. Kidonakis, Phys. Rev. D 84, 011504 (2011) [arXiv:1105.5167 [hep-ph]].[3] N. Kidonakis, Phys. Rev. D 81, 054028 (2010) [arXiv:1001.5034 [hep-ph]].[4] N. Kidonakis, Phys. Rev. D 82, 054018 (2010) [arXiv:1005.4451 [hep-ph]].[5] N. Kidonakis, Phys. Rev. D 83, 091503(R) (2011) [arXiv:1103.2792 [hep-ph]].[6] N. Kidonakis, arXiv:1210.7813 [hep-ph].[7] A.D. Martin, W.J. Stirling, R.S. Thorne, and G. Watt, Eur. Phys. J. C 63, 189(2009) [arXiv:0901.0002 [hep-ph]].[8] CDF Collaboration, CDF Note 10793.5[9] D0 Collaboration, Phys. Rev. D 84, 112001 (2011) [arXiv:1108.3091 [hep-ex]].[10] ATLAS Collaboration, Physics Letters B 717, 330 (2012) [arXiv:1205.3130 [hep-ex]]; ATLAS-CONF-2012-132.[11] CMS Collaboration, arXiv:1209.4533 [hep-ex]; CMS-PAS-TOP-12-011.[12] ATLAS Collaboration, ATLAS-CONF-2012-056.[13] ATLAS Collaboration, Phys. Lett. B 716, 142 (2012) [arXiv:1205.5764 [hep-ex]].[14] CMS Collaboration, arXiv:1209.3489 [hep-ex].[15] ATLAS Collaboration, ATLAS-CONF-2012-131.[16] CMS Collaboration, CMS-PAS-TOP-11-024; CMS-PAS-TOP-12-007.[17] CDF Collaboration, Conf. Note 10163; Phys. Rev. D 82, 052002 (2010)[arXiv:1002.2919 [hep-ex]].[18] D0 Collaboration, Phys. Lett. B 679, 177 (2009) [arXiv:0901.2137 [hep-ex]];Phys. Rev. D 82, 032002 (2010) [arXiv:0911.4286 [hep-ex]]; Phys. Lett. B 704,403 (2011) [arXiv:1105.5384 [hep-ex]].[19] D0 Collaboration, Phys. Lett. B 693, 515 (2010) [arXiv:1001.1900 [hep-ex]].[20] M. Aliev, H. Lacker, U. Langenfeld, S. Moch, P. Uwer, and M. Wiedermann,Comput. Phys. Commun. 182, 1034 (2011) [arXiv:1007.1327 [hep-ph]].[21] V. Ahrens, A. Ferroglia, M. Neubert, B.D. Pecjak, and L.L. Yang, Phys.Lett. B703, 135 (2011) [arXiv:1105.5824 [hep-ph]].[22] M. Beneke, P. Falgari, S. Klein, C. Schwinn, Nucl. Phys. B 855, 695 (2012)[arXiv:1109.1536 [hep-ph]].[23] N. Kidonakis and B.D. Pecjak, Eur. Phys. J. C 72, 2084 (2012) [arXiv:1108.6063[hep-ph]].[24] P. Baernreuther, M. Czakon, and A. Mitov, Phys. Rev. Lett. 109, 132001 (2012)[arXiv:1204.5201 [hep-ph]].[25] N. Kidonakis and R. Vogt, Phys. Rev. D 68, 114014 (2003) [hep-ph/0308222].[26] N. Kidonakis and R. Vogt, Phys. Rev. D 78, 074005 (2008) [arXiv:0805.3844[hep-ph]].[27] N. Kidonakis, Phys. Rev. D 73, 034001 (2006) [hep-ph/0509079].[28] CMS Collaboration, arXiv:1211.2220 [hep-ex].6

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