Miyachi, Y. [Yamagata U.]

DOE OSTI2026

Measurements of Angular Distributions of Drell-Yan Dimuons in $p+p$ and $p+d$ Interactions at 120 GeV/$c$

We present experimental results on the angular distributions of Drell-Yan muons produced by a 120 GeV/$c$ proton beam interacting with liquid hydrogen and deuterium targets. The dimuon angular distributions in both polar ($θ$) and azimuthal ($ϕ$) angles in the Collins-Soper frame are measured within the kinematic range of $4.5 < m_{μμ} < 10\ \mathrm{GeV}/c^2$, $0.19 < p_T < 2.24\ \mathrm{GeV}/c$, and $0 < x_F < 0.95$. Unlike the results of a previous proton-induced Drell-Yan experiment at a higher energy, the data reveal a pronounced $\cos 2ϕ$ modulation in the angular distributions. Comparison with perturbative QCD (pQCD) predictions shows statistically significant deviations, with p-values of 3.5% for the $p+p$ and 1.5% for the $p+d$ Drell-Yan processes. These results suggest the presence of nonperturbative QCD contributions.

Nagai, K. [Christian Brothers U.; Los Alamos; Taiw↗

DOE OSTI2025

LHCspin: a Polarized Gas Target for LHC

The goal of the LHCspin project is to develop innovative solutions for measuring the 3D structure of nucleons in high-energy polarized fixed-target collisions at LHC, exploring new processes and exploiting new probes in a unique, previously unexplored, kinematic regime. A precise multi-dimensional description of the hadron structure has, in fact, the potential to deepen our understanding of the strong interactions and to provide a much more precise framework for measuring both Standard Model and Beyond Standard Model observables. This ambitious task poses its basis on the recent experience with the successful installation and operation of the SMOG2 unpolarized gas target in front of the LHCb spectrometer. Besides allowing for interesting physics studies ranging from astrophysics to heavy-ion physics, SMOG2 provides an ideal benchmark for studying beam-target dynamics at the LHC and demonstrates the feasibility of simultaneous operation with beam-beam collisions. With the installation of the proposed polarized target system, LHCb will become the first experiment to simultaneously collect data from unpolarized beam-beam collisions at $\sqrt{s}$=14 TeV and polarized and unpolarized beam-target collisions at $\sqrt{s_{NN}}\sim$100 GeV. LHCspin has the potential to open new frontiers in physics by exploiting the capabilities of the world's most powerful collider and one of the most advanced spectrometers. This document also highlights the need to perform an R&D campaign and the commissioning of the apparatus at the LHC Interaction Region 4 during the Run 4, before its final installation in LHCb. This opportunity could also allow to undertake preliminary physics measurements with unprecedented conditions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗