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The hyperfine splitting in charmonium. Lattice computations using the Wilson and clover fermion actions / Christopher Michael, R.D. Kenway, B.J. Pendleton, Christopher T. Sachrajda, D.G. Richards, K.C. Bowler, S.P. Booth, D.S. Henty, J.N. Simone, A.D. Simpson, P.W. Stephenson, Chris Allton

Physics Letters B, Volume: 292, Issue: 3-4, Pages: 408 - 412

Swansea University Author: Chris Allton

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Abstract

We compute the hyperfine splitting $m_{J/\psi}-m_{\eta_c}$ on the lattice, using both the Wilson and $O(a)$-improved (clover) actions for quenched quarks. The computations are performed on a $24~3\times48$ lattice at $\beta = 6.2$, using the same set of 18 gluon configurations for both fermion actio...

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Published in: Physics Letters B
ISSN: 03702693
Published: 1992
Online Access: Check full text

URI: https://cronfa.swan.ac.uk/Record/cronfa28430
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Abstract: We compute the hyperfine splitting $m_{J/\psi}-m_{\eta_c}$ on the lattice, using both the Wilson and $O(a)$-improved (clover) actions for quenched quarks. The computations are performed on a $24~3\times48$ lattice at $\beta = 6.2$, using the same set of 18 gluon configurations for both fermion actions. We find that the splitting is 1.83\err{13}{15} times larger with the clover action than with the Wilson action, demonstrating the sensitivity of the spin-splitting to the magnetic moment term which is present in the clover action. However, even with the clover action the result is less than half of the physical mass-splitting. We also compute the decay constants $f_{\eta_c}$ and $f~{-1}_{J/\psi}$, both of which are considerably larger when computed using the clover action than with the Wilson action. For example for the ratio $f~{-1}_{J/\psi}/f~{-1}_{\rho}$ we find 0.32\err{1}{2} with the Wilson action and $0.48\pm 3$ with the clover action (the physical value is 0.44(2)).
College: College of Science
Issue: 3-4
Start Page: 408
End Page: 412