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Study of Doubly Charged Delta Baryons in Collisions of Copper Nuclei at the Relativistic Heavy Ion Collider

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Technical Report

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Experiments involving heavy-ion collisions at the Relativistic Heavy Ion ColliderRHIC produce the hottest matter known to humans, approximately 100,000 times hotter than the center of the Sun or 7 trillion degrees Celsius. In these collisions, the nucleons melt into their constituent quarks and gluons for approximately 10 yoctoseconds 1E-23 seconds. As the collision system expands and cools, the quarks and gluons combine into particles via a process called hadronization and subsequently stream out into the detectors. Detailed studies of these produced particles can yield information about the properties of the medium in which they were produced. Some of the produced particles, known collectively as resonances, have lifetimes comparable to the lifetime of the collision medium itself. More specifically, comparative studies of the relative production of short-lived resonances and possible modifications of their properties by medium effects may provide information about the conditions present in and lifetime of the collision medium. In this project, we utilize data from 24.4 million collisions of copper nuclei at center-of-mass energies of 200 GeV per nucleon pair collected by the Solenoidal Tracker At RHIC STAR detector to reconstruct decays of the doubly-charged Delta baryon resonance and its anti-particle. Fits to the invariant mass distribution of Delta candidates are performed as functions of transverse momentum and collision centrality and properties of the Delta resonances are extracted statistically. Specifically we look at the mass, the width, and the yield of this resonance. Comparisons of our results with previous studies from proton on proton collisions and deuteron on gold nucleus collisions, as well as with model calculations, may provide deeper insight into effects present in the collision medium as well as the lifetime of the medium itself.

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  • Particle Accelerators

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