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Title:
Transverse momentum resummation in the azimuthal spectra of Drell-Yan processes
Abstract:
To propose an alternative portal to the W/Z correlations, the azimuthal opening angle $\phi_{L}$ between the final leptons is investigated in this work. In the fixed-order context, the calculation on the $\phi_L$ distribution is not straightforward, as the soft and collimated beam radiations in the regime of $\phi_L\to\pi$ or $q_T\to 0$ give rise to large logarithms bringing down the perturbativity. Hence, it is essential to carry out the all-perturbative order resummation over those singular behaviors, such as $\ln[q_T/M_{V}]$. To accomplish this goal, the soft-collinear effective theory is utilized in this work to factorize and exponentiate those $\ln[q_T/M_{V}]$ terms. Thanks to the rapid developments of the fixed-order studies, the beam and soft ingredients for this method have been computed up to the three-loop level, which permits us to access the N$^3$LL$'$ evaluations. In tacking the hard sectors, not only are the non-singlet amplitudes comprised in the calculation, the singlet influences are also addressed for the neutral DY process particularly. As to the later case, we employ the axial-vector effective field theory to integrate out the heavy quark impacts and recollect the hard ingredients. The according anomalous dimensions and perturbative expressions can be extracted from the anomaly-dependent quark form factors.
For the numerical outputs, the comparison between the singular and QCD contributions are presented at first. Their agreements can be obviously observed in the vicinity of $q_T=0$. Besides that, the resummation-improved results (from NLL$'$ to N$^3$LL$'$) are exhibited as well. It is found that as to the majority of regions, the N$^{3(2)}$LL$'$ results are well situated in the N$^{2(1)}$LL$'$ error bands, and with the accuracy growing, the decrease in the theoretical uncertainties is substantial.
Zoom link: IPPP Seminars (Friday at 2 pm UK time)
https://durhamuniversity.zoom.us/j/99420124988?pwd=ZEFLSDB3THJtaWZOTU54R25mT1NuZz09
Meeting ID: 994 2012 4988