2D BAO vs 3D BAO: Hints for new physics?

As next-generation telescopes and observational surveys continue to expand the boundaries of our understanding, tensions and discrepancies between observational datasets are becoming increasingly prominent. In this work, we focus on one such discrepancy: the differences between 2D and 3D Baryon Acoustic Oscillation (BAO) measurements. Without extending beyond the standard $\Lambda$CDM framework, we systematically study and highlight this discrepancy in different parameter spaces. This work examines the constraints on fundamental cosmological parameters ($H_0$, $r_d$, $\Omega_m$) derived from Baryon Acoustic Oscillation (BAO) and Type Ia Supernovae (SNIa) data. By analyzing BAO observational datasets from two distinct methodologies (2D and 3D) alongside the Pantheon Plus SNIa sample, we identify a significant systematic difference: 2D BAO measurements consistently yield higher values of $hr_d$ compared to both 3D BAO and DESI analyses. While 2D BAO measurements appear to bridge the Hubble tension by simultaneously accommodating both a higher $H_0$ value (aligning with SH0ES) and a larger sound horizon $r_d$ (matching Planck), this apparent reconciliation comes at the cost of introducing tension with the well-constrained Planck measurement of $\Omega_{m0}h^2$. This behavior arises because of systematically higher values of the product $H_0r_d$ observed in 2D BAO analysis compared to 3D analyses. Therefore, given these systematic differences, we advocate for careful consideration when using 2D BAO measurements to address the Hubble tension, suggesting that understanding the origin of this 2D-3D discrepancy should be a priority for future investigations.