Oct 2020 - Sept 2021

Internal Seminar by Wanli Ju



Transverse momentum resummation in the azimuthal spectra of Drell-Yan processes


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)


Meeting ID: 994 2012 4988