A test of $\Delta $B=2 baryon number nonconservation. MOHAPATRA 1980 and MOHAPATRA 1989 discuss the theoretical motivations for looking for ${{\mathit n}}{{\overline{\mathit n}}}$ oscillations. DOVER 1983 and DOVER 1985 give phenomenological analyses. The best limits come from looking for the decay of neutrons bound in nuclei. However, these analyses require model-dependent corrections for nuclear effects. See KABIR 1983, DOVER 1989, ALBERICO 1991, and GAL 2000 for discussions. Direct searches for ${{\mathit n}}$ $\rightarrow$ ${{\overline{\mathit n}}}$ transitions using reactor neutrons are cleaner but give somewhat poorer limits. We include limits for both free and bound neutrons in the Summary Table. See MOHAPATRA 2009 and PHILLIPS 2016 for recent reviews.

VALUE (s) CL% DOCUMENT ID TECN  COMMENT $\bf{>4.7 \times 10^{8}}$ 90 1 ABE 02   CNTR ${{\mathit n}}$ bound in oxygen $\bf{>8.6 \times 10^{7}}$ 90 BALDO-CEOLIN 99   CNTR Reactor (free) neutrons • • We do not use the following data for averages, fits, limits, etc. • • $>1.37 \times 10^{8}$ 90 2 AHARMIM 01   SNO ${{\mathit n}}$ bound in deuteron $>2.7 \times 10^{8}$ 90 ABE 01 C   CNTR ${{\mathit n}}$ bound in oxygen $>1.3 \times 10^{8}$ 90 CHUNG 00 B   SOU2 ${{\mathit n}}$ bound in iron $>1 \times 10^{7}$ 90 BALDO-CEOLIN 99   CNTR See BALDO-CEOLIN 1994 $>1.2 \times 10^{8}$ 90 BERGER 99   FREJ ${{\mathit n}}$ bound in iron $>4.9 \times 10^{5}$ 90 BRESSI 99   CNTR Reactor neutrons $>4.7 \times 10^{5}$ 90 BRESSI 98   CNTR See BRESSI 1990 $>1.2 \times 10^{8}$ 90 TAKITA 98   CNTR ${{\mathit n}}$ bound in oxygen $>1 \times 10^{6}$ 90 FIDECARO 98   CNTR Reactor neutrons $>8.8 \times 10^{7}$ 90 PARK 98 B   CNTR $>3 \times 10^{7}$ BATTISTONI 98   NUSX $> 0.27 - 1.1 \times 10^{8}$ JONES 98   CNTR $>2 \times 10^{7}$ CHERRY 98   CNTR 1  ABE 2021 supersedes ABE 2015C. 2  The AHARMIM 2017 value is an unbounded limit (it does not assume a positive lifetime). The bounded limit is $1.23 \times 10^{8}$ sec.

Conservation Laws:

BARYON NUMBER

References