Nuclear-matter modification of decay widths in the phi-->e+e- and phi-->K+K- channels

Area of Science:

• Nuclear Physics
• Particle Physics
• Hadron Spectroscopy

Background:

• Investigating modifications of hadrons in nuclear matter is crucial for understanding Quantum Chromodynamics (QCD) phase transitions.
• The phi meson (φ) is a vector meson composed of a strange quark-antiquark pair, making it sensitive to medium effects.

Purpose of the Study:

• To search for in-medium modifications of phi mesons by analyzing their K+K- decay channel.
• To compare the nuclear mass number dependence of phi meson production via K+K- and e+e- decay channels.

Main Methods:

• Measurement of invariant mass spectra of phi --> K+K- decays in 12 GeV proton-nucleus (p+A) reactions.
• Analysis of K+K- spectra using a relativistic Breit-Wigner function with a combinatorial background.
• Comparison of nuclear mass number dependence (using sigma(A)=sigma0Aalpha parameterization) for K+K- and e+e- decay channels.

Main Results:

• The K+K- spectra were well described by the relativistic Breit-Wigner function across different betagamma regions.
• The difference in the nuclear mass number exponent (alpha) between the K+K- and e+e- decay channels was found to be 0.14 ± 0.12.
• Limits were established for the partial decay widths of phi mesons in nuclear matter.

Conclusions:

• The study did not find significant evidence for in-medium modifications of the phi meson.
• The results provide constraints on theoretical models describing hadron properties in dense nuclear matter.