We present the results of our lattice QCD computation of the electric (E1) and magnetic (M2) form factors relevant to the χc1→J/ψγ decay by using the gauge field configurations produced by the Extended Twisted Mass Collaboration with Nf=2+1+1 dynamical Wilson-Clover twisted mass fermions at four different lattice spacings with physical dynamical u, d, s and c quark masses (except for the coarsest lattice for which the lightest sea quark corresponds to a pion with mπ≃175MeV). In the continuum limit, we obtain Γ(χc1→J/ψγ)=0.3265(79)MeV, which agrees to (1÷2)σ with the experimental results and disagrees with a previous (unquenched) lattice QCD calculation. Our result for the magnetic quadrupole fractional transition amplitude, a2=M2/E12+M22=−0.0666(22), is in agreement with the experiment and represents an improvement by a factor of about 30 with respect to the only existing (quenched) lattice QCD result.
Bečirević, D., Di Palma, R., Frezzotti, R., Gagliardi, G., Lubicz, V., Sanfilippo, F., et al. (2025). Lattice QCD study of the χc1→J/ψγ decay. PHYSICS LETTERS. SECTION B, 868, 139811 [10.1016/j.physletb.2025.139811].
Lattice QCD study of the χc1→J/ψγ decay
Di Palma, Roberto;Gagliardi, Giuseppe;Lubicz, Vittorio;
2025-01-01
Abstract
We present the results of our lattice QCD computation of the electric (E1) and magnetic (M2) form factors relevant to the χc1→J/ψγ decay by using the gauge field configurations produced by the Extended Twisted Mass Collaboration with Nf=2+1+1 dynamical Wilson-Clover twisted mass fermions at four different lattice spacings with physical dynamical u, d, s and c quark masses (except for the coarsest lattice for which the lightest sea quark corresponds to a pion with mπ≃175MeV). In the continuum limit, we obtain Γ(χc1→J/ψγ)=0.3265(79)MeV, which agrees to (1÷2)σ with the experimental results and disagrees with a previous (unquenched) lattice QCD calculation. Our result for the magnetic quadrupole fractional transition amplitude, a2=M2/E12+M22=−0.0666(22), is in agreement with the experiment and represents an improvement by a factor of about 30 with respect to the only existing (quenched) lattice QCD result.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
