A new next-to-leading order Monte Carlo program for calculation of fully
differential single top quark final states is described and first results
presented. Both the s- and t-channel contributions are included.Comment: 3 pages, 3 figures, talk presented at DPF2000, August 9-12, 2000. To
  appear in International Journal of Modern Physics 

B. W. Harris

Collaboration CTEQ

E. Laenen

L. Phaf

S. Weinzierl

Smith M.

Stelzer T.

Z. Sullivan

English

arXiv

Crossref

Fully Differential QCD Corrections to Single Top Quark Final States

The authors have performed a fully differential calculation of QCD corrections to electroweak production of single top quarks. The method used allows for jet definitions and experimental cuts. The corresponding computer code passes the necessary check of reproducing the previously known total rate. First examination of the rapidity and transverse momentum of the top quark shows the corrections to be flat relative to leading order. Additional phenomenological studies are in order. Further work is in progress on the corrections to t-b-jet final states which will give a comprehensive set of tools for studying single-top-quark production at future hadron-hadron colliders

Harris, B. W.

Laenen, E.

Phaf, L.

Sullivan, Z.

Weinzierl, S.

UNT (University of North Texas) Digital Library

. -.&To be published in the proceedings of the ~()~()Meeting of the Division ot’ Pmticles ml ~iekis of’ the .knericanPhysical Society (DPF 2000). Columbus. OH. August 9-12.2000,International Journal d Mo&ern Physics ,t,(@ World Scientific Publishing Company ANL-HEP-CP-()(J.094Fully differentia~ QCD corrections to single top quark final statesB. W. Harris*l, E. Laenen2, L. Pha~, Z. SuIlivanl, S. Weinzier121 HEP Division, Argonne National Labomtor~, Argonne, IL 60439, USA2 NIKHEF Theory Group, Kruislaan 409, 1098 SJ Amsterdam, The NetherlandsA new next-to-leading order Monte Carlo program for calculation of fully differentialsingle top quark final states is described and first results presented. Both the s- andt-channel contributions are included.1. IntroductionThe electroweak production of single top quarks, despite being smaller in ratethan it’s strong interaction counterpart — tf pair production, offers many physicspossibilities for the Tevatron Run II and the LHC. Direct measurement of lv~b12andsensitivity beyond the Standard Model are two examples 1. It is also a backgroundto some signals for the Higgs boson and various types of new physics. Total rates forthe s- and t-channel production processes have been calcu1ated2’3 to next-to-leadingorder (NLO) in perturbative QCD.Herein we give first results in our ongoing effort to calculate fully differentialNLO QCD corrections to single top quark final states at hadron colliders. Theadvantages of calculating cross sections to NLO in a fully differential manner are wellknown in general. For example, only at NLO does a jet definition enter non-trivially..4dditionally, systematic errors are always reduced when one can predict the crossin the experimentally visible region, as opposed to extrapolating the measured crosssection to the full phase space to get a total rate.2. MethodThe results presented below are from a calculation performed using the phase spaceslicing method 4. Briefly, two cutoffs are used to isolate the regions containing softand collinear singularities from the remainder of the three-body phase space. Thethree-body squared matrix elements are integrated over these singular regions an-alytically. The soft singuku-ities cancel upon addition of the virtual contributions,and the remaining collinear singularities are factorized into the parton distribu-tions. The integrations over the singularity-free portions of the three-body phasespace are performed using Monte Carlo methods. When all of the contributions arecombined at the histogramming stage the various cutoff dependence cancel, sincethe cutoffs merely mark the boundary between the regions where the integrationswere performed using analytic or Monte Carlo methods.“presenter; E-mail: harris@hep. anl. gov1The submitted manuscnpt has been crealedby the University of Chicago as operator ofArgonne National Laboratory (“Argcr’ne’”under Contract INO.W-31 -109-ENG-38 wfh$he IJ S. Department of Energy. The IJ.SGovernment retains for i[self. and others ac[-mg on Its behalf, a paid-up, nonexcluswe,Irrevocable worldwrde license in ~a,d a~icleiO remoduce, prepare derwatwe works d,~.lr, kte coptes to the public and pertor,m pub-hr;!y and d!splay publicly, by or on behalf otthe Gowwnment.DISCLAIMERThis report was prepared as an account of work sponsoredby an agency of the United States Government. Neitherthe United States Government nor any agency thereof, norany of their employees, make any warranty, express orimplied, or assumes any legal liability or responsibility forthe accuracy, completeness, or usefulness of anyinformation, apparatus, product, or process disclosed, orrepresents that its use would not infringe privately ownedrights. Reference herein to any specific commercialproduct, process, or service by trade name, trademark,manufacturer, or otherwise does not necessarily constituteor impJy its endorsement, recommendation, or favoring bythe United States Government or any agency thereof. Theviews and opinions of authors expressed herein do notnecessarily state or reflect those of the United StatesGovernment or any agency thereof.PortionsDISCLAIMERof this document may be illegiblein electronic image products. Images areproduced from the best available originaldocument.2 l%lly differential Q CD corrections to single top10[~3 body50 sumut% (pb)–5–lo2 body– 15 I I I I0.30..... .. ... .... . . .. .. .... .. .. . .. . .. .... .. .. ... ... . .. .. . .. .. ... .. . ... .. ... . .. .. ... . .. .0.26 ..u . . . ..o . . . ..u . . . .." . . ..< . . . ..u . . . ..0 . . . ..o . . ..? . . . ..Q . . . ..O . . . .. O . . ..o . . . . . . .0.24 0Fig. 1. The next-to-leading order contribution to the single-top-quark total cross section via thes-channel process. The two- and three-body contributions, together with their sum, are shown asa function of the soft cut-off d.. The bottom enlargement shows the sum (open circles) relative to+5% (dotted lines) of the analytic result (solid line).3. ResultsUsing the method described in the previous section we have calculated the cor-rections to both s- and t-channel singl+top-quark production. Due to space limita-tions only s-channel results will be shown, and those only superficially. Full detailsare forthcoming 5.A necessary check on the results based on this method is that infrared-safephysical observable are independent of the cut-offs used to delineate phase space,provided they are chosen small enough. The total cross section is an infrared-safeobservable. Shown in Fig. (1) is the NLO correction to the total cross section asa function of the soft cut-off 6, summed over t and f final states for the s-channelproduction process compared with the known result2 using CTEQ4M6 parton dis-tribution functions at a ~ = 2 TeV proton- antiproton machine. The mass fac-torization and renormalization scales are taken to be pf = p? = mtOP= 175 GeV.The mass of the bottom quark was neglected and that of the W gauge boson wastaken to be 80.4 GeV. The Monte Carlo result for the NLO correction is within onepercent of the analytical result of 0.264 pb for 68 < 10–3 implying better than athird of a percent agreement for the full NLO result of 0.922 pb.Shown in Fig. (2) are the leading order (lower curves) and full next-to-leadingorder (upper curves) rapidity (left) and transverse momentum (right) distributionsof the top quark produced via the s-channel process. These curves were made usingthe same inputs as above, and no other cuts were applied. These results are alsocut-off independent, as expected. Taking the ratio of NL() and LO the correctionsFully differential QCD corrections to single top . 311,$ , , t ~~() .~()0.4 - //1,,!). 3=,,’ ., -.. ,& / ,/ ~. \,.z / ,.’ ‘.+ 02 - . ‘\/“\\0. i :\/’”>, ‘~i%o ,-3 -2 -1 0 1 2 3,“.2,.-3,~-,,.-8, 1 r i ,XLO.-..-./:-, LO -.:: /., -...>,.:,,,“’’”h‘%,‘~,-. \t , 1 I I0 50 100 150 200 250 mPI [GeV]Fig. 2. Leading (lower cu~ves) and full next-to-leading (upper curves) order rapidity (left) andtransverse momentum (right) spectra for the top quark produced via the s-channel process.are observed to be relatively independent of the rapidity and transverse momentumof the top quark, a somewhat atypical, but serendipitous (from the event generationpoint of view), situation that warrants further investigation.In conclusion, we have performed a fully differential calculation of QCD correc-tions to electroweak production of single top quarks. The method used allows forjet definitions and experimental cuts. The corresponding computer code passes thenecessary check of reproducing the previously known total rate. First examinationof the rapidity and transverse momentum of the top quark shows the corrections tobe flat relative to leading order. Additional phenomenological studies are in order.Further work is in progress on the corrections to t – b – jet final states which willgive a comprehensive set of tools for studying single-top-quark production at futurehadron-hadron colliders.This work was supported in part by the United States Department of Energy, HighEnergy Physics Division, under contract W-31 -109-Eng-38, and the Foundationfor Fundamental Research of Matter (FOM) and the National Organization forScientific Research (NWO), The Netherlands.References1.2.3.4.5.6.See, for example, T. Stelzer, Z. Sullivan, and S. Willenbrock Phys. Rev. D58 (1998)094021; T. Tait and C.-P. Yuan, [hep-ph/0007298].M. Smith and S. Willenbrock, Phys. Rev. D54 (1996) 6696; S. Mrenna and C.–P. Yuan,F’hys. Lett. B416 (1998) 200,T. Stelzer, Z. Sullivan, and S. Willenbrock, Phys. Rev. D56 (1997) 5919; T. Tait andC.-P. Yuan, [hep-ph/9710372].L. J. Bergmann, Ph.D. thesis, Florida State University, 1989 (unpublished); H. Baer,J. Ohnemus, and J. F. Owens, Phys. Rev. D40 (1989) 2844; see also B. W. Harris andJ. F. Gvens, .4NL-HEP-PR-00-044 for full details and review of the method.B, W. Harris, E. Laenen, L. Phaf, Z. Sullivan, and S. Weinzier], in preparation.CTEQ Collaboration, H. L. Lai et al., Phys. Rev. D55 (1997) 1280.

Fully differential QCD corrections to single top quark final states.

A new next-to-leading order Monte Carlo program for calculation of fully differential single top quark final states is described and first results presented. Both the s- and t-channel contributions are included

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Fully differential QCD corrections to single top quark final states

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Fully differential QCD corrections to single top quark final states

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