arXiv subjects

Dario van den Berg

Publications and source records attributed to Dario van den Berg.

3 recordsLinked to original sources

arXiv2026

Improved Regge Kinematics and All-Path-Length Corrections to Momentum Broadening in the Quark-Gluon Plasma

We present a study of transverse momentum broadening for high-energy partons propagating through the quark-gluon plasma (QGP), extending the Gyulassy-Levai-Vitev (GLV) formalism to include both all-path-length (APL) corrections and improved sub-Regge kinematics. The standard GLV framework relies on the large separation distance and large formation time approximations, which are well justified in large nuclei but may become unreliable in small collision systems, where the relevant length and coherence scales are comparable. Working to first order in the opacity expansion, we derive analytic expressions for the transverse momentum broadening distribution and the corresponding momentum transport coefficient, $\hat{q}$, while systematically relaxing these approximations. The APL correction arises from relaxing the large separation distance approximation, whereas the sub-Regge and combined sub-Regge-APL corrections are obtained using an improved set of Regge kinematics beyond the strict Regge limit. We find that these corrections can substantially modify both the transverse momentum broadening distribution and the momentum transport coefficient, particularly for short path lengths and high exchanged momentum, providing a more complete theoretical description of momentum broadening in the QGP.

hep-ph↗

arXiv2026

From One to Eight: Supersymmetry Restoration in Lattice 3D ${\cal N} = 4$ Super Yang--Mills

Topological twisting provides a powerful framework for constructing lattice formulations of supersymmetric gauge theories. In three dimensions, a twisted version of ${\cal N} = 4$ super Yang--Mills theory can be discretized so that one nilpotent scalar supersymmetry is preserved exactly at nonzero lattice spacing. The remaining seven supersymmetries are broken by lattice artifacts of ${\cal O}(a)$, where $a$ is the lattice spacing. An important question is whether these supersymmetries are automatically restored in the continuum limit $a \to 0$, or whether fine-tuning of the lattice couplings is required. In this work, we derive the additional twisted supersymmetries by combining discrete $R$-symmetries of the continuum theory with the action of the scalar supercharge. This construction suggests that restoration of rotational symmetry in the continuum limit implies restoration of $R$-symmetry, leading to an automatic enhancement to the full ${\cal N} = 4$ supersymmetry without further tuning. These results may enable nonperturbative lattice studies of three-dimensional supersymmetric gauge theories relevant to string theory and mirror symmetry.

hep-lat↗

arXiv2026

Momentum Broadening in the Opacity Expansion: All-Path-Length Corrections and Improved Regge Kinematics

We present a detailed study of momentum broadening and the jet transport coefficient $\hat{q}$ for high-energy partons traversing the Quark-Gluon Plasma (QGP), extending the Gyulassy-Levai-Vitev (GLV) formalism to include both all-path-length (APL) and sub-Regge kinematical corrections. Traditional GLV calculations rely on the large separation distance and large formation time approximations, which are valid for large systems but whose applicability to small systems, such as $pp$ and $p/d$A collisions, may fail. We derive analytic expressions for the momentum broadening distributions and $\hat{q}$ to first order in the opacity expansion, and perform a detailed numerical investigation to quantify their impact. The APL correction suppresses momentum broadening at low $p_{\perp}$, with a correction scaling as $\propto 1/(L\, p_{\perp})$ that dominates for small systems, while converging to the standard GLV result at large $L$. The sub-Regge kinematical correction enhances momentum broadening at high $p_{\perp}$, becoming significant when the transverse momentum transfer approaches the magnitude of the parton's large light-cone momentum component, and vanishing in the Regge limit where this ratio is small. When both corrections are combined, the sub-Regge kinematical correction partially mitigates the suppression induced by the APL term; in the case of $\hat{q}$, this mitigation is essentially complete, with $\hat{q}_{(\mathrm{APL+SUB})}$ found to coincide closely with the standard GLV result. These findings demonstrate that sub-Regge kinematical corrections can resolve the long-standing problem of large negative energy-loss contributions at high energies identified in earlier studies.

hep-ph↗