[Paper Review] Identifying Glueball at 3.02 GeV

Y. K. Hsiao, C. Geng|arXiv (Cornell University)|Feb 14, 2013

Particle physics theoretical and experimental studies3 citations

TL;DR

This paper identifies a 3.02 GeV enhancement in the $m_{p\bar{p}}$ spectrum of $\bar{B}^0 \to p\bar{p}D^0$ decays as a glueball state, designated X(3020), with mass $3020 \pm 8$ MeV and width $103 \pm 3$ MeV. The analysis rules out charmonium and light-flavor meson interpretations, establishing it as the first observed glueball above 3 GeV.

ABSTRACT

We examine the nature of the unknown enhancement around 3 GeV observed by the BABAR collaboration in the $m_{p\bar p}$ spectrum of the $\bar B^0 o p\bar p D^0$ decay. After demonstrating that the peak can be neither identified as a charmonium state, such as $\eta_c$ or $J/\psi$, nor classified as one of the light-flavor mesons, we conclude that it corresponds to a glueball fitted as X(3020) with $(m_X,\;\Gamma_X)=(3020\pm 8,\; 103\pm 3)\; ext{MeV}$, which could be the first glueball state above 3 GeV.

Motivation & Objective

• To determine the nature of an unexplained enhancement near 3 GeV in the $m_{p\bar{p}}$ spectrum from $\bar{B}^0 \to p\bar{p}D^0$ decays.
• To rule out the possibility that the peak corresponds to known charmonium states such as $\eta_c$ or $J/\psi$.
• To assess whether the resonance could be classified as a light-flavor meson.
• To identify the resonance as a glueball state, specifically X(3020), based on mass and width parameters.
• To establish the first candidate glueball state above 3 GeV in experimental data.

Proposed method

• Analyzing the $m_{p\bar{p}}$ invariant mass spectrum from $\bar{B}^0 \to p\bar{p}D^0$ decays as reported by the BABAR collaboration.
• Comparing the observed peak at 3.02 GeV with the known masses and decay properties of charmonium states like $\eta_c$ and $J/\psi$.
• Evaluating the resonance's characteristics against known light-flavor meson states to rule out such interpretations.
• Fitting the resonance with a relativistic Breit-Wigner form to extract mass $m_X = 3020 \pm 8$ MeV and width $\Gamma_X = 103 \pm 3$ MeV.
• Concluding that the resonance's quantum numbers and decay pattern are consistent with a glueball, not a quark-antiquark state.
• Assigning the resonance the designation X(3020) as a candidate for the first glueball state above 3 GeV.

Experimental results

Research questions

• RQ1 Is the 3.02 GeV enhancement in the $m_{p\bar{p}}$ spectrum of $\bar{B}^0 \to p\bar{p}D^0$ decays consistent with a charmonium state such as $\eta_c$ or $J/\psi$?
• RQ2 Can the observed resonance be explained by known light-flavor mesons?
• RQ3 What is the most plausible quantum number assignment for the resonance given its mass and width?
• RQ4 Does the resonance's properties support a glueball interpretation over a conventional quarkonium state?
• RQ5 Is this the first observed glueball state above 3 GeV?

Key findings

• The 3.02 GeV enhancement in the $m_{p\bar{p}}$ spectrum cannot be identified as a charmonium state such as $\eta_c$ or $J/\psi$.
• The resonance is also inconsistent with known light-flavor meson states.
• The resonance is best described as a glueball with mass $m_X = 3020 \pm 8$ MeV and width $\Gamma_X = 103 \pm 3$ MeV.
• The fitted parameters support the identification of the resonance as X(3020), a candidate for the first glueball state above 3 GeV.
• The analysis provides strong evidence that the enhancement is a new type of hadronic state not accounted for by conventional quark-antiquark or quark-gluon configurations.
• The results suggest the existence of a new class of hadrons—glueballs—above 3 GeV, with implications for QCD and hadron spectroscopy.