Neutron–antineutron oscillation accompanied by CP-violation in magnetic fields

Abstract In this work, we explore the possibility of the n – <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>n</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> </mml:math> oscillation accompanied by CP-violation in the presence of magnetic fields. The n – <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>n</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> </mml:math> oscillation, which violates the baryon number ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi class="MJX-tex-calligraphic" mathvariant="script">B</mml:mi> </mml:math> ) by two units ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo stretchy="false">∣</mml:mo> <mml:mi mathvariant="normal">Δ</mml:mi> <mml:mi class="MJX-tex-calligraphic" mathvariant="script">B</mml:mi> <mml:mo stretchy="false">∣</mml:mo> <mml:mo>=</mml:mo> <mml:mn>2</mml:mn> </mml:math> ), can originate from the mixing between the neutron ( n ) and the neutral elementary particle ( η ) and may give rise to non-trivial physical consequences that can be testable in future experiments. We show that the probability of the n – <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>n</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> </mml:math> oscillation can be greatly enhanced by properly adjusting the magnetic field. In particular, the peak values of the oscillation probability in the presence of resonance magnetic fields can be 8–10 orders of magnitude higher than that in the absence of magnetic fields. We point out that there might not be sizable CP-violating effects in the n – <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>n</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> </mml:math> oscillation unless the mass of η is close to the mass of the neutron. We also analyze the interplay among various parameters associated with both <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi class="MJX-tex-calligraphic" mathvariant="script">B</mml:mi> </mml:math> -violation and CP-violation and attempt to disentangle the effects of such parameters. The n – <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>n</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> </mml:math> oscillation process accompanied by CP-violation may open a promising avenue for exploring new physics beyond the Standard Model (SM).