Lattice calaulation of χc0→ 2γ decay width

We perform a lattice QCD calculation of the $\chi_{c0} \rightarrow 2\gamma$ decay width using a model-independent method which does not require a momentum extrapolation of the corresponding off-shell form factors. The simulation is performed on ensembles of $N_f=2$ twisted mass lattice QCD gauge configurations with three different lattice spacings. After a continuum extrapolation, the decay width is obtained to be $\Gamma_{\gamma\gamma}(\chi_{c0})=3.65(83)_{\mathrm{stat}}(21)_{\mathrm{lat.syst}}(66)_{\mathrm{syst}}\, \textrm{keV}$. Albeit this large statistical error, our result is compatible with the experimental results within 1.3$\sigma$. Potential improvements of the lattice calculation in the future are also discussed. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Article funded by SCOAP3 and published under licence by Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Science and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.

Low-energy excitations and $$\gamma $$-decay branchings in $$^{124}$$Sn via (p,p’$$\gamma $$) at $$E_p={15}\,\,\hbox {MeV}$$

The dipole response of the proton-magic nucleus $${}^{124}\hbox {Sn}$$ 124 Sn was previously investigated with electromagnetic and hadronic probes. Different responses were observed revealing the so-called isospin splitting of the Pygmy Dipole Resonance (PDR). Here we present the results of a new study of $${}^{124}\hbox {Sn}$$ 124 Sn using inelastic proton scattering at low energies to test an additional probe possibly exciting states of the PDR. The response to the new probe as well as the $$\gamma $$ γ -decay behavior of excited states were studied. The $${}^{124}\hbox {Sn}$$ 124 Sn (p,p’$$\gamma $$ γ ) experiment was performed at $$E_p = {15}\,\,\hbox {MeV}$$ E p = 15 MeV using the combined spectroscopy setup SONIC@HORUS at the Tandem accelerator of the University of Cologne. Proton-$$\gamma $$ γ coincidences were recorded, enabling a state-to-state analysis due to the excellent energy resolution for both particles and $$\gamma $$ γ rays. $$ J=1 $$ J = 1 states in the PDR region were populated in the present inelastic proton scattering experiment. Many $$\gamma $$ γ -decay branching ratios could be determined.

Study of $$K^+ \rightarrow \pi ^{0} e^{+} \nu \gamma $$ decay with OKA setup

Results of a study of the $$K^+ \rightarrow \pi ^{0} e^{+} \nu \gamma $$ K + → π 0 e + ν γ decay at OKA setup are presented. More than 32,000 events of this decay are observed. The differential spectra over the photon energy and the photon–electron opening angle in kaon rest frame are presented. The branching ratios, normalized to that of $$K_{e3}$$ K e 3 decay are calculated for different cuts on $$E^*_\gamma $$ E γ ∗ and $$cos\Theta ^{*}_{e\gamma }$$ c o s Θ e γ ∗ . In particular, the branching ratio for $$E^{*}_{\gamma }>30$$ E γ ∗ > 30 MeV and $$\Theta ^{*}_{e \gamma }>20^{\circ }$$ Θ e γ ∗ > 20 ∘ is measured R = $$\frac{Br(K^+ \rightarrow \pi ^{0} e^{+} \nu _{e} \gamma ) }{Br(K^+ \rightarrow \pi ^{0} e^{+} \nu _{e})} $$ B r ( K + → π 0 e + ν e γ ) B r ( K + → π 0 e + ν e ) = = (0.587±0.010(stat.)±0.015(syst.))$$\times 10^{-2}$$ × 10 - 2 , which is in a good agreement with ChPT $$O(p^{4})$$ O ( p 4 ) calculations.

GIANT M1 RESONANCE ON THE GROUND AND EXCITED STATES IN 2s1d-SHELL NUCLEI

The gamma decay of the resonance-like structures observed in the reaction of radiative capture of protons by the nuclei 22Ne, 26Mg, 30Si, 34,36S, and 38Ar in the region of excitation energies of 7…12 MeV was studied. The excitation functions of this reaction were measured. The resonance strengths in the energy range of the accelerated protons Ep = 1.0…3.0 MeV were determined. The obtained discrete distributions of the magnetic dipole γ-transitions on the ground and excited states for the nuclei of the 2s1d-shell have resonance character. Giant M1 resonance on the ground and excited states in the 23Na, 27Al, 31P, 35.37Cl, and 39K nuclei has been identified. The position of the M1 resonance on excited states coincides with that predicted by the Brink-Axel hypothesis for nuclei that are at the beginning of the subshell.