Centauric 1-Jettiness in DIS and Universal Power Corrections

Abstract

We introduce the \emph{Centauric 1-jettiness}, ${\tau }_1^C$, a generalized event shape for Deep Inelastic Scattering (DIS) with adjustable beam and jet reference vectors and thus beam and jet regions. We demonstrate that a specific choice of weights allows this observable to exactly reproduce the geometric boundaries of the Centauro jet algorithm in the Breit frame. Within the framework of Soft-Collinear Effective Theory (SCET), we derive a factorized cross section in the small-${\tau }_1^C$ region in terms of known perturbative ingredients. This allows the resummation of large logarithms to N${}^3$LL accuracy, which we then match to fixed-order NLO QCD ($\mathcal{O}({\alpha }_s^2)$) predictions from \texttt{NLOJet++}. We establish that the soft measurement reduces to a rescaled hemisphere measurement, placing Centauric 1-jettiness in the same universality class, for the leading non-perturbative corrections, as DIS thrust and jet mass. As a consequence, the leading non-perturbative shift depends on the same universal first-moment-shift parameter ${\Omega }_1$ and scales exactly as $1/R$ with the jet radius, thanks to the boost invariance of the Centauro algorithm along the photon axis in the Breit frame, a scaling that we test using \textsc{Pythia} simulations. These results open new strategies for determining the strong coupling from DIS event shapes, with $R$ providing a handle to break the degeneracy between ${\alpha }_s$ and the universal non-perturbative shift parameter ${\Omega }_1$.

81 pages, 27 figures, 2 tables