Version 2.4.5beta December 08, 2025

New Physics Modeling:

• Lambda sub-binomial recombination fluctuation parameter for nuclear recoils, with a smooth transition between the supra- and sub-binomial regimes (Chen Ding, LZ / Brown)
• Energy dependence allowed for NR’s F_ex and F_i (Chen Ding, LZ / Brown; Matthew Szydagis, LZ / UAlbany SUNY)
• Recombination fluctuations in the beta and gamma models (super-binomial still) can now depend on energy or total quanta Nq instead of electron fraction ‘y’ or the mean recombination probability ‘r’ (Matthew)
• Liquid Argon S1 PSD updated, along with beta and NR Ly and Qy (Kate and Olga)
• Liquid Xenon S1 PSD updates (Yufan Qie, LZ / Rochester) with added physical sanity check for getting photon times (Lanqing Yuan, WUSTL / XENONnT) and new verbosity level and more code comments (Kate)
• Power law constant-offset option added to total NR quanta, and coupled to removal of sigmoid in NR Ly (Ryan McMonigle, LZ / UAlbany)
• More accurate alpha Qy and Ly at both lower E-fields and much lower energies (Scott Haselschwardt, LZ / UMichigan; Harry Nelson, LZ / UCSB)
• Revised longitudinal diffusion model for S2s. Three options: low (the default at low fields), medium, and high
• Weighted ER modeling replaced with ability to customize beta and gamma yields: Qy multiplicative factor replaces random seed input*
• Removed all references to the “older” ER (beta) model, which is now ancient history, erasing entirely the old beta model
• Created new shell unction to hold future modeling work (mod TIB) while providing fresh vectors for storing mean-yield parameters for said future work (by Yung Nok Joseph Lau, UCLA) with external flexibility
• Changed standard halo model velocity distribution to truncated MB distribution (Kian Trengove, LZ / UAlbany)

New Code Features:

• Initial implementation of ACC (adaptive cut & count) dark-matter exclusion-limit setting technique
• G2 (Generation-2) analysis header now the default header file in both execNEST.cpp and rootNEST.cpp
• Added lock of random seed (Dacheng Xu, XENONnT / Columbia)
• bareNEST default detector changed from XENON10 to LUX Run03
• A new comment tells users precisely where to change the parameter vectors within execNEST.cpp
• D-D n Xe recoil spectrum changes: skew Gaussian peak, default spectrum now LZ instead of LUX
• Velocity and diffusion constants in both gas and liquid now all permit dependence on temperature, pressure, and density separately or all together
• Detector name calling more automatic now
• Note added on how to restore the original energy and field dependences of the Fano factor for total beta (or gamma) quanta
• Enormous overhaul of the “loopNEST” feature
• Poisson random number generator upgraded to 64-bit unsigned integer
• *Old-school weighted ER modeling accessible with a 0 seed, which has a default of 1
• New power law for AmBe spectrum (Yongheng Xu, LZ / UCLA)
• Made DetName a class member, updated execNEST to use this accessor, and added LZ WS2024 aka SR3 detector parameters header file (Albert Baker, LZ / KCL)
• Added extra options to runNESTvec() and updated the NESTObservableArray to simplify that function (Albert Baker)
• Additional comments warning about PrintSubThr being set to false causing the number of events the end user sees to be fewer than what had been requested
• Caution statement prevents end-user error during manual positioning of events (outside of the detector volume)
• (Re-)standardized the detector names across LZ WIMP searches 22 and 24 and across the entire codebase, removing outdated and repeated information
• LZ WS2024 (SR3) made the new default in terms of the detector configuration file, complete with S1 and S2 (polynomial-fit) LCE maps for g1(x,y,z) and g2(x,y)

Miscellaneous Bug Fixes:

• Updated G4integration/CMakeLists.txt to fix CMake directory error (Noah Everett, Harvard)
• Replaced undefined uint with more standard type unsigned int (Pierce Comerford, Oxford)
• Fixed inaccuracy in warning message on exceeding S1 and S2 linear noise terms (Chami Amarasinghe, UCSB / LZ)
• Now possible to input less than 1 kg-day of WIMP-search exposure
• Corrected missing fourth parameter in the SetDriftVelocity() function
• Negative Nq disallowed in extremely preliminary new beta yields model made available for testing