Azimuthal correlations of high transverse momentum jets at next-to-leading order in the parton branching method

Abstract The azimuthal correlation, $$\Delta \phi _{12}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>Δ</mml:mi> <mml:msub> <mml:mi>ϕ</mml:mi> <mml:mn>12</mml:mn> </mml:msub> </mml:mrow> </mml:math> , of high transverse momentum jets in pp collisions at $$\sqrt{s}=13$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> <mml:mo>=</mml:mo> <mml:mn>13</mml:mn> </mml:mrow> </mml:math> TeV is studied by applying PB-TMD distributions to NLO calculations via MCatNLO together with the PB-TMD parton shower. A very good description of the cross section as a function of $$\Delta \phi _{12}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>Δ</mml:mi> <mml:msub> <mml:mi>ϕ</mml:mi> <mml:mn>12</mml:mn> </mml:msub> </mml:mrow> </mml:math> is observed. In the back-to-back region of $${\Delta \phi _{12}}\rightarrow \pi $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mrow> <mml:mi>Δ</mml:mi> <mml:msub> <mml:mi>ϕ</mml:mi> <mml:mn>12</mml:mn> </mml:msub> </mml:mrow> <mml:mo>→</mml:mo> <mml:mi>π</mml:mi> </mml:mrow> </mml:math> , a very good agreement is observed with the PB-TMD Set 2 distributions while significant deviations are obtained with the PB-TMD Set 1 distributions. Set 1 uses the evolution scale while Set 2 uses transverse momentum as an argument in $$\alpha _\mathrm {s}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>α</mml:mi> <mml:mi>s</mml:mi> </mml:msub> </mml:math> , and the above observation therefore confirms the importance of an appropriate soft-gluon coupling in angular ordered parton evolution. The total uncertainties of the predictions are dominated by the scale uncertainties of the matrix element, while the uncertainties coming from the PB-TMDs and the corresponding PB-TMD shower are very small. The $$\Delta \phi _{12}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>Δ</mml:mi> <mml:msub> <mml:mi>ϕ</mml:mi> <mml:mn>12</mml:mn> </mml:msub> </mml:mrow> </mml:math> measurements are also compared with predictions using MCatNLO together Pythia 8, illustrating the importance of details of the parton shower evolution.