Finite-width effects in unstable-particle production at hadron colliders

Falgari, Pietro; Papanastasiou, Andrew S.; Signer, Adrian

doi:10.1007/jhep05(2013)156

Cited by 24 publications

(23 citation statements)

References 74 publications

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“…As a further refinement of our result we envisage in the future to include NLO QCD corrections to the pp → W + W − bb process [66][67][68][69] to compute effects from off-shell top quarks and non-factorizable corrections to our prediction. These effects modify the total cross-section by a relative factor t /m t and α s · t /m t , respectively.…”

Section: Discussionmentioning

confidence: 99%

Top quark mass determination from the energy peaks of b-jets and B-hadrons at NLO QCD

et al. 2016

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We analyze the energy spectra of single b-jets and B-hadrons resulting from the production and decay of top quarks within the SM at the LHC at the NLO QCD. For both hadrons and jets, we calculate the correlation of the peak of the spectrum with the top quark mass, considering the "energy peak" as an observable to determine the top quark mass. Such a method is motivated by our previous work where we argued that this approach can have reduced sensitivity to the details of the production mechanism of the top quark, whether it concerns higher-order QCD effects or new physics contributions. For a 1% jet energy scale uncertainty, the top quark mass can then be extracted using the energy peak of b-jets with an error ±(1.2(exp) + 0.6(th)) GeV. In view of the dominant jet energy scale uncertainty in the measurement using b-jets, we also investigate the extraction of the top quark mass from the energy peak of the corresponding B-hadrons which, in principle, can be measured without this uncertainty. The calculation of the B-hadron energy spectrum is carried out using fragmentation functions at NLO. The dependence on the fragmentation scale turns out to be the largest theoretical uncertainty in this extraction of top quark mass.

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Section: Discussionmentioning

confidence: 99%

Top quark mass determination from the energy peaks of b-jets and B-hadrons at NLO QCD

et al. 2016

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“…Various solutions have been proposed, e.g., the alternative use of a so-called 1S mass [46,47] defined through the perturbative contribution to the mass of a hypothetical n = 1, 3 S 1 toponium bound state, cf. [37] for an application to tt hadro-production or the use of a "potential-subtracted" (PS) mass [48], recently considered in [49] in the context of finite-width effects in unstable-particle production at hadron colliders. In any case, since the conventional perturbative expansion of the cross section breaks down for m tt 2m t we do not display this particular kinematic region in Fig.…”

Section: Figmentioning

confidence: 99%

Differential distributions for top-quark hadro-production with a running mass

Dowling

Moch

2014

Eur. Phys. J. C

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We take a look at how the differential distributions for top-quark production are affected by changing to the running mass scheme. Specifically we consider the transverse momentum, rapidity and pair-invariant mass distributions at next-to-leading order for the top-quark mass in the MS scheme. It is found that, similar to the total cross section, the perturbative expansion converges faster and the scale dependence improves using the mass in the MS scheme as opposed to the on-shell scheme. We also update the analysis for the total cross section using the now available full next-to-next-to-leading order contribution.The measurement of top-quark pair production cross sections at hadron colliders has entered the era of precision physics with the analysis of data available from the Large Hadron Collider (LHC) in the runs at center-of-mass energies √ S = 7 and 8 TeV. Measurements of the total cross section for tt-production from ATLAS and CMS reach by now an accuracy of typically better than O(10 %), with the systematic and luminosity uncertainties already dominating over the small statistical uncertainty, see, e.g., [1][2][3]. First results of differential distributions for tt-production from the LHC are appearing as well [4,5]. Thus, given the present experimental accuracy hadro-production of tt-pairs is currently being established as a standard model (SM) benchmark process.This has motivated tremendous activity on the theory side to match the experimental precision by computing higher order corrections in quantum chromodynamics (QCD) and we briefly recapitulate the status for inclusive tt-pair production, i.e., no tagged final states. Predictions for the total cross section are complete to next-to-next-to-leading order (NNLO) [6][7][8][9] while differential distributions are known to next-to-leading order (NLO) [10,11], including top-quark decay [12][13][14][15][16], though. Additional corrections beyond NLO based on threshold logarithms have been obtained for distria e-mail: matthew.dowling@desy.de butions in the top-quark's transverse momentum and rapidity, p t T and y t , as well as in the invariant mass m tt of the top-quark pair [17][18][19][20].Comparison of these theory predictions to experimental data can be used to determine parameters such as the strong coupling constant, the parton luminosity and the top-quark mass and to study their correlations. Of these parameters, the top-quark mass is certainly the most interesting one with prominent implications for the electro-weak vacuum of the SM, see, e.g., [21,22]. It is a particularly attractive feature of cross sections measurements that they offer the opportunity for an unambiguous and theoretically well-defined determination of the top-quark mass in a particular renormalization scheme [23,24].The conventional scheme choice for the quark mass renormalization is the pole mass, which has its short-comings [25,26], though, since it is based on the idea of quarks appearing as asymptotic states. It exhibits poor convergence of the perturbative series and ...

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“…However, it is nevertheless true that the amplitudes written down in these equations give the leading contributions in the double-and single-resonant regions. We note that approaches such as the pole expansion [83,84] or an effective theory expansion [81,85,86] provide gauge-invariant methods to compute cross sections to higher order in the different resonance regions without having to consider the full final-state amplitude. In such expansions the dominant terms in double-and single-resonant regions indeed receive their contributions from eqs.…”

Section: Jhep03(2016)099mentioning

confidence: 99%

Probing the top-quark width through ratios of resonance contributions of e + e − → W + W − b b ¯ $$ {\mathrm{e}}^{+}{\mathrm{e}}^{-}\to {\mathrm{W}}^{+}{\mathrm{W}}^{-}\mathrm{b}\overline{\mathrm{b}} $$

Liebler

Moortgat‐Pick

Papanastasiou

2016

J. High Energ. Phys.

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In this paper we propose a method to gain access to the top-quark width which exploits off-shell regions in the process e + e − → W + W − bb. Working at next-toleading order in QCD we show that carefully selected ratios of off-shell regions to on-shell regions in the reconstructed top and anti-top invariant mass spectra are, independently of the coupling g tbW , sensitive to the top-quark width. We explore this approach for different centre of mass energies and initial-state beam polarisations at e + e − colliders and briefly comment on the applicability of this method for a measurement of the top-quark width at the LHC.

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Finite-width effects in unstable-particle production at hadron colliders

Cited by 24 publications

References 74 publications

Top quark mass determination from the energy peaks of b-jets and B-hadrons at NLO QCD

Top quark mass determination from the energy peaks of b-jets and B-hadrons at NLO QCD

Differential distributions for top-quark hadro-production with a running mass

Probing the top-quark width through ratios of resonance contributions of e + e − → W + W − b b ¯ $$ {\mathrm{e}}^{+}{\mathrm{e}}^{-}\to {\mathrm{W}}^{+}{\mathrm{W}}^{-}\mathrm{b}\overline{\mathrm{b}} $$

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