Speaker
Description
We present the first lattice-QCD determination of isovector proton transverse-momentum-dependent parton distribution functions (TMDPDFs) simultaneously in the unpolarized, helicity, and transversity channels. The calculation is performed within large-momentum effective theory using Coulomb-gauge-fixed quasi-TMD correlators on a $2+1$-flavor domain-wall fermion ensemble at the physical pion mass with lattice spacing $a=0.0836~{\rm fm}$. We use proton quasi-TMD beam functions at boost momentum $P_z=1.62~{\rm GeV}$, with the transversity channel newly computed here, and extract the Collins-Soper kernel and intrinsic soft function from pion quasi-TMD wave functions with momenta up to $P_z=1.85~{\rm GeV}$ and large-momentum pion form factors with momentum transfer up to $Q^2=13.7~{\rm GeV}^2$, respectively. Using the matching formula with next-to-leading-logarithmic (NLL) resummation, we extract the corresponding light-cone TMDPDFs in the moderate-$x$ region as functions of Bjorken $x$ and transverse separation up to $b_T \gtrsim 1~{\rm fm}$, accessing a nonperturbative region that is weakly constrained by experiment. The unpolarized, helicity, and transversity TMDPDFs exhibit remarkably similar $b_T$ dependence, providing evidence that these three $T$-even leading-twist channels share approximately universal nonperturbative transverse dynamics, with only mild polarization dependence in the explored moderate-$x$ region. The large-$b_T$ behavior is constrained by the ratio-scheme intrinsic soft function and is used to obtain transverse-momentum-space TMDPDFs through Fourier transformation. These results provide a benchmark lattice-QCD prediction for the nonperturbative three-dimensional partonic structure of the proton relevant to future precision TMD phenomenology.