1. [n]  United States physicist (born in Austria) who was a discoverer of cosmic radiation (1883-1964)
2. [n]  Nazi leader who in 1941 flew to Scotland in an apparent attempt to negotiate a peace treaty with Great Britain but was imprisoned for life (1894-1987)
3. [n]  Swiss physiologist noted for studies of the brain (1881-1973)
4. [n]  English pianist (1890-1965)

HESS is a 4 letter word that starts with H.