We present the investigation of the use of Opticks, a GPU-accelerated optical photon interface with the LHCb detector simulation, to improve computation time of optical photon propagation. The hybrid workflow, combining the particle simulation package Geant4 and Opticks, offloads optical photon propagation to GPUs, thereby accelerating the overall simulation process. The consistency of the results obtained from Geant4 and Opticks simulations is verified with a simplified LHCb RICH1 detector geometry, demonstrating the feasibility of the proposed approach. In addition, the ongoing transition to the NVIDIA OptiX 7 API and re-structuring of Opticks code is discussed within the context of HEP simulation workflows, with caveats explored.

United Kingdom

Yunlong Li

Adam Davis

Sajan Easo

Keith Evans

Evelina Gersabeck

Marco Gersabeck

Lucas Girardey

Raja Nandakumar

Annabelle Pointer

Gpu-based optical photon simulation for the LHCb RICH 1 detector

We introduce a new unbinned two sample test statistic sensitive to CP violation utilizing the optimal transport plan associated with the Wasserstein (earth mover’s) distance. The efficacy of the test statistic is shown via two examples of CP asymmetric distributions with varying sample sizes: the Dalitz distributions of B 0 → K + π  −  π 0 and of D 0 → π + π  −  π 0 decays. The windowed version of the Wasserstein distance test statistic is shown to have comparable sensitivity to CP violation as the commonly used energy test statistic, but also retains information about the localized distributions of CP asymmetry over the Dalitz plot. For large statistic datasets we introduce two modified Wasserstein distance based test statistics — the binned and the sliced Wasserstein distance statistics, which show comparable sensitivity to CP violation, but improved computing time and memory scalings. Finally, general extensions and applications of the introduced statistics are discussed.

United States

Tony Menzo

Ahmed Youssef

Jure Zupan

Earth mover’s distance as a measure of CP violation

The BICEP2 experiment has announced a signal for primordial gravity waves with tensor-to-scalar ratio r=0.2−0.05+0.07 [1] . There are two ways to reconcile this result with the latest Planck experiment [2] . One is by assuming that there is a considerable tilt of r , Tr , with a positive sign, Tr=dln⁡r/dln⁡k≳0.57−0.27+0.29 corresponding to a blue tilt for the tensor modes of order nT≃0.53−0.27+0.29 , assuming the Planck experiment best-fit value for tilt of scalar power spectrum nS . The other possibility is to assume that there is a negative running in the scalar spectral index, dnS/dln⁡k≃−0.02 which pushes up the upper bound on r from 0.11 up to 0.26 in the Planck analysis assuming the existence of a tensor spectrum. Simple slow-roll models fail to provide such large values for Tr or negative runnings in nS [1] . In this note we show that a non-Bunch–Davies initial state for perturbations can provide a match between large field chaotic models (like m2ϕ2 ) with the latest Planck result [3] and BICEP2 results by accommodating either the blue tilt of r or the negative large running of nS .