<p>In this paper, we present the resummation-improved differential transverse momentum and azimuthal decorrelation cross sections, <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_25461_Article_IEq2.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="64" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <msub> <mrow> <mi mathvariant="normal">d</mi> <mi>σ</mi> </mrow> <mrow> <mi>t</mi> <mover accent="true"> <mi>t</mi> <mo stretchy="true">¯</mo> </mover> </mrow> </msub> <mo>/</mo> <msub> <mrow> <mi mathvariant="normal">d</mi> <mi>q</mi> </mrow> <mi mathvariant="normal">T</mi> </msub> </math></EquationSource> <EquationSource Format="TEX">\( {\textrm{d}\sigma}_{t\overline{t}}/{\textrm{d}q}_{\textrm{T}} \)</EquationSource> </InlineEquation> and <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_25461_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="81" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <msub> <mrow> <mi mathvariant="normal">d</mi> <mi>σ</mi> </mrow> <mrow> <mi>t</mi> <mover accent="true"> <mi>t</mi> <mo stretchy="true">¯</mo> </mover> </mrow> </msub> <mo>/</mo> <mi mathvariant="normal">d</mi> <mtext>∆</mtext> <msub> <mi>ϕ</mi> <mrow> <mi>t</mi> <mover accent="true"> <mi>t</mi> <mo stretchy="true">¯</mo> </mover> </mrow> </msub> </math></EquationSource> <EquationSource Format="TEX">\( {\textrm{d}\sigma}_{t\overline{t}}/\textrm{d}\Delta {\phi}_{t\overline{t}} \)</EquationSource> </InlineEquation>, in top-antitop pair production at the LHC. Our calculation is based on the observation that both cross sections are dominated by topologies where the top-quark pair is well separated, expressed in their relative velocity <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_25461_Article_IEq4.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="78" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <msub> <mi>β</mi> <mrow> <mi>t</mi> <mover accent="true"> <mi>t</mi> <mo stretchy="true">¯</mo> </mover> </mrow> </msub> <mo>∼</mo> <mi mathvariant="script">O</mi> <mfenced close=")" open="("> <mn>1</mn> </mfenced> </math></EquationSource> <EquationSource Format="TEX">\( {\beta}_{t\overline{t}}\sim \mathcal{O}(1) \)</EquationSource> </InlineEquation>, at colliding energies of <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_25461_Article_IEq5.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="30" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <msqrt> <mi>s</mi> </msqrt> </math></EquationSource> <EquationSource Format="TEX">\( \sqrt{s} \)</EquationSource> </InlineEquation> = 13 TeV or higher. Therefore, the asymptotic behaviour in the limits <i>q</i><sub>T</sub> → 0 and <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_25461_Article_IEq1.gif" Format="GIF" Height="18" Rendition="HTML" Resolution="72" Type="Linedraw" Width="35" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <mtext>∆</mtext> <msub> <mi>ϕ</mi> <mrow> <mi>t</mi> <mover accent="true"> <mi>t</mi> <mo stretchy="true">¯</mo> </mover> </mrow> </msub> </math></EquationSource> <EquationSource Format="TEX">\( \Delta {\phi}_{t\overline{t}} \)</EquationSource> </InlineEquation> → 0 can mostly be captured by the soft and collinear resummation in the HQET+SCET framework. Nevertheless, starting at N<sup>2</sup>LL, Coulomb singularities emerge in the threshold regime, <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_25461_Article_IEq7.gif" Format="GIF" Height="18" Rendition="HTML" Resolution="72" Type="Linedraw" Width="23" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <msub> <mi>β</mi> <mrow> <mi>t</mi> <mover accent="true"> <mi>t</mi> <mo stretchy="true">¯</mo> </mover> </mrow> </msub> </math></EquationSource> <EquationSource Format="TEX">\( {\beta}_{t\overline{t}} \)</EquationSource> </InlineEquation> → 0, in both the hard sector and its evolution kernels, leading to unphysical results upon integration over the entire <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_25461_Article_IEq7.gif" Format="GIF" Height="18" Rendition="HTML" Resolution="72" Type="Linedraw" Width="23" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <msub> <mi>β</mi> <mrow> <mi>t</mi> <mover accent="true"> <mi>t</mi> <mo stretchy="true">¯</mo> </mover> </mrow> </msub> </math></EquationSource> <EquationSource Format="TEX">\( {\beta}_{t\overline{t}} \)</EquationSource> </InlineEquation> range. To this end, two prescriptions, dubbed the D- and R-prescription, are introduced to regularise these Coulomb singularities. They embody two fundamentally different methods to truncate the threshold enhanced terms, rendering their contribution finite. In the absence of a combined threshold and small-transverse-momentum resummation, we present a quantitative assessment of the ambiguity introduced by the choice of prescription, itself a test of the sensitivity of our calculation to such threshold enhancements, for both the <InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_25461_Article_IEq2.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="64" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <msub> <mrow> <mi mathvariant="normal">d</mi> <mi>σ</mi> </mrow> <mrow> <mi>t</mi> <mover accent="true"> <mi>t</mi> <mo stretchy="true">¯</mo> </mover> </mrow> </msub> <mo>/</mo> <msub> <mrow> <mi mathvariant="normal">d</mi> <mi>q</mi> </mrow> <mi mathvariant="normal">T</mi> </msub> </math></EquationSource> <EquationSource Format="TEX">\( {\textrm{d}\sigma}_{t\overline{t}}/{\textrm{d}q}_{\textrm{T}} \)</EquationSource> </InlineEquation> and <InlineEquation ID="IEq10"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_25461_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="81" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <msub> <mrow> <mi mathvariant="normal">d</mi> <mi>σ</mi> </mrow> <mrow> <mi>t</mi> <mover accent="true"> <mi>t</mi> <mo stretchy="true">¯</mo> </mover> </mrow> </msub> <mo>/</mo> <mi mathvariant="normal">d</mi> <mtext>∆</mtext> <msub> <mi>ϕ</mi> <mrow> <mi>t</mi> <mover accent="true"> <mi>t</mi> <mo stretchy="true">¯</mo> </mover> </mrow> </msub> </math></EquationSource> <EquationSource Format="TEX">\( {\textrm{d}\sigma}_{t\overline{t}}/\textrm{d}\Delta {\phi}_{t\overline{t}} \)</EquationSource> </InlineEquation> spectra.</p>

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The qT and \( \Delta {\phi}_{t\overline{t}} \) spectra in top-antitop hadroproduction at NNLL+NNLO: the interplay of soft-collinear resummation and Coulomb singularities

  • Wan-Li Ju,
  • Marek Schönherr

摘要

In this paper, we present the resummation-improved differential transverse momentum and azimuthal decorrelation cross sections, d σ t t ¯ / d q T \( {\textrm{d}\sigma}_{t\overline{t}}/{\textrm{d}q}_{\textrm{T}} \) and d σ t t ¯ / d ϕ t t ¯ \( {\textrm{d}\sigma}_{t\overline{t}}/\textrm{d}\Delta {\phi}_{t\overline{t}} \) , in top-antitop pair production at the LHC. Our calculation is based on the observation that both cross sections are dominated by topologies where the top-quark pair is well separated, expressed in their relative velocity β t t ¯ O 1 \( {\beta}_{t\overline{t}}\sim \mathcal{O}(1) \) , at colliding energies of s \( \sqrt{s} \) = 13 TeV or higher. Therefore, the asymptotic behaviour in the limits qT → 0 and ϕ t t ¯ \( \Delta {\phi}_{t\overline{t}} \) → 0 can mostly be captured by the soft and collinear resummation in the HQET+SCET framework. Nevertheless, starting at N2LL, Coulomb singularities emerge in the threshold regime, β t t ¯ \( {\beta}_{t\overline{t}} \) → 0, in both the hard sector and its evolution kernels, leading to unphysical results upon integration over the entire β t t ¯ \( {\beta}_{t\overline{t}} \) range. To this end, two prescriptions, dubbed the D- and R-prescription, are introduced to regularise these Coulomb singularities. They embody two fundamentally different methods to truncate the threshold enhanced terms, rendering their contribution finite. In the absence of a combined threshold and small-transverse-momentum resummation, we present a quantitative assessment of the ambiguity introduced by the choice of prescription, itself a test of the sensitivity of our calculation to such threshold enhancements, for both the d σ t t ¯ / d q T \( {\textrm{d}\sigma}_{t\overline{t}}/{\textrm{d}q}_{\textrm{T}} \) and d σ t t ¯ / d ϕ t t ¯ \( {\textrm{d}\sigma}_{t\overline{t}}/\textrm{d}\Delta {\phi}_{t\overline{t}} \) spectra.