<p>We present the analytical results for the two-loop form factors needed for <i>χ</i><sub><i>Q</i>,<i>J</i></sub> production and decay. We consider the two-loop corrections to the process <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_26325_Article_IEq1.gif" Format="GIF" Height="25" Rendition="HTML" Resolution="72" Type="Linedraw" Width="81" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <mi mathvariant="italic">γγ</mi> <mo>↔</mo> <mmultiscripts> <msubsup> <mi>P</mi> <mi>J</mi> <mfenced close="]" open="["> <mn>1</mn> </mfenced> </msubsup> <mprescripts /> <none /> <mn>3</mn> </mmultiscripts> </math></EquationSource> <EquationSource Format="TEX">\( \gamma \gamma \leftrightarrow {}^3{P}_J^{\left[1\right]} \)</EquationSource> </InlineEquation>, that has been known only numerically before, and the processes <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_26325_Article_IEq2.gif" Format="GIF" Height="25" Rendition="HTML" Resolution="72" Type="Linedraw" Width="79" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <mi mathvariant="italic">gg</mi> <mo>↔</mo> <mmultiscripts> <msubsup> <mi>P</mi> <mi>J</mi> <mfenced close="]" open="["> <mn>1</mn> </mfenced> </msubsup> <mprescripts /> <none /> <mn>3</mn> </mmultiscripts> </math></EquationSource> <EquationSource Format="TEX">\( gg\leftrightarrow {}^3{P}_J^{\left[1\right]} \)</EquationSource> </InlineEquation>, <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_26325_Article_IEq3.gif" Format="GIF" Height="25" Rendition="HTML" Resolution="72" Type="Linedraw" Width="80" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <mi mathvariant="italic">γg</mi> <mo>↔</mo> <mmultiscripts> <msubsup> <mi>P</mi> <mi>J</mi> <mfenced close="]" open="["> <mn>8</mn> </mfenced> </msubsup> <mprescripts /> <none /> <mn>3</mn> </mmultiscripts> </math></EquationSource> <EquationSource Format="TEX">\( \gamma g\leftrightarrow {}^3{P}_J^{\left[8\right]} \)</EquationSource> </InlineEquation> and <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_26325_Article_IEq4.gif" Format="GIF" Height="25" Rendition="HTML" Resolution="72" Type="Linedraw" Width="79" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <mi mathvariant="italic">gg</mi> <mo>↔</mo> <mmultiscripts> <msubsup> <mi>P</mi> <mi>J</mi> <mfenced close="]" open="["> <mn>8</mn> </mfenced> </msubsup> <mprescripts /> <none /> <mn>3</mn> </mmultiscripts> </math></EquationSource> <EquationSource Format="TEX">\( gg\leftrightarrow {}^3{P}_J^{\left[8\right]} \)</EquationSource> </InlineEquation>, which have not been computed before. We observe that the NRQCD pole structure of the two-loop amplitude in the <i>gg</i> channel is more involved for the spin-triplet <i>P</i>-wave case than for the pseudo-scalar <i>S</i>-wave case. It involves in addition to the standard Coulomb singularity also a new singularity whose cancellation requires the inclusion of the <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_26325_Article_IEq5.gif" Format="GIF" Height="24" Rendition="HTML" Resolution="72" Type="Linedraw" Width="77" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <mi mathvariant="italic">gg</mi> <mo>↔</mo> <mmultiscripts> <msubsup> <mi>S</mi> <mn>1</mn> <mfenced close="]" open="["> <mn>8</mn> </mfenced> </msubsup> <mprescripts /> <none /> <mn>3</mn> </mmultiscripts> </math></EquationSource> <EquationSource Format="TEX">\( gg\leftrightarrow {}^3{S}_1^{\left[8\right]} \)</EquationSource> </InlineEquation> form factor. We give the high precision numerical results for the hard functions that can be used to compute <i>χ</i><sub><i>Q</i>,<i>J</i></sub> production and decay up to NNLO accuracy.</p>

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Two-loop form factors for P-wave quarkonium production and decay

  • Melih A. Ozcelik

摘要

We present the analytical results for the two-loop form factors needed for χQ,J production and decay. We consider the two-loop corrections to the process γγ P J 1 3 \( \gamma \gamma \leftrightarrow {}^3{P}_J^{\left[1\right]} \) , that has been known only numerically before, and the processes gg P J 1 3 \( gg\leftrightarrow {}^3{P}_J^{\left[1\right]} \) , γg P J 8 3 \( \gamma g\leftrightarrow {}^3{P}_J^{\left[8\right]} \) and gg P J 8 3 \( gg\leftrightarrow {}^3{P}_J^{\left[8\right]} \) , which have not been computed before. We observe that the NRQCD pole structure of the two-loop amplitude in the gg channel is more involved for the spin-triplet P-wave case than for the pseudo-scalar S-wave case. It involves in addition to the standard Coulomb singularity also a new singularity whose cancellation requires the inclusion of the gg S 1 8 3 \( gg\leftrightarrow {}^3{S}_1^{\left[8\right]} \) form factor. We give the high precision numerical results for the hard functions that can be used to compute χQ,J production and decay up to NNLO accuracy.