Shape Changes in the Mirror Nuclei ^{70}Kr and ^{70}Se.

Area of Science:

• Nuclear Physics
• Experimental Nuclear Structure
• Isospin Symmetry Studies

Background:

• The study of isospin symmetry in nuclei provides insights into fundamental nuclear forces.
• The A=70 isospin triplet (⁷⁰Kr, ⁷⁰Br, ⁷⁰Se) is crucial for testing nuclear models.
• Previous studies have not reported violations of isospin symmetry at the level of transition matrix elements.

Purpose of the Study:

• To experimentally determine the reduced transition probability B(E2;0⁺→2⁺) for the proton-rich nucleus ⁷⁰Kr.
• To compare electromagnetic matrix elements within the A=70 isospin triplet and test the linearity with T<0xE2><0x82><0x9B>.
• To investigate potential violations of isospin symmetry in nuclear transitions.

Main Methods:

• Inelastic scattering experiments were conducted at intermediate energies.
• The reduced transition probability B(E2;0⁺→2⁺) was extracted for ⁷⁰Kr.
• Data for ⁷⁰Br and ⁷⁰Se from the same experiment were used for comparison.

Main Results:

• A significant 3σ deviation from the expected linear trend of electromagnetic matrix elements as a function of T<0xE2><0x82><0x9B> was observed.
• This represents the first instance of isospin symmetry violation at the level of transition matrix elements.
• No current nuclear structure theory quantitatively explains this observed deviation.

Conclusions:

• The experimental findings challenge established nuclear structure theories.
• A heuristic explanation involving a shape change between the mirror nuclei ⁷⁰Kr and ⁷⁰Se is proposed, contradicting model predictions.
• This study highlights the need for refined theoretical models to describe isospin symmetry breaking phenomena.