Pawsey filesystems follow the POSIX standard, as is used in typical Linux and Mac OSX filesystems. There are many tutorials on the internet, such as www.tldp.org/LDP/intro-linux/html/sect_03_04.html.
Do not set any of your directories to be world-readable. This has the risk that every user on the supercomputer can read the data, even if for a short time.
When running jobs through SLURM, the group of new files written is the group given to SLURM using the –A flag (e.g. #SBATCH –A project_code). This is usually your project group, so others in your project can read the files if they and the directory (and relevant parent directories) have the group-read attribute.
Use the group-sticky attributed. If a directory has the group-sticky attribute (can be set by chmod g+S directoryname), then new files copied to the directory will change to have the group of the directory. This is useful in /group for reliably sharing data and source code.
If a directory does not have the group-sticky attribute, then new files copied to the directory will change to have the group of the user who copied the files. This can be useful in /scratch if you do not want other members of the project group to be able to access, modify or delete files.
Some file transfer programs (like WinSCP) by default will ignore a group-sticky bit. You can either edit the program’s configuration or fix the permissions after the upload.