Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userHigher $eta_c(nS)$ and $eta_b (nS)$ mesons
104
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The hyperfine splittings in heavy quarkonia are studied in a model-independent way using the experimental data on di-electron widths. Relativistic correlations are taken into account together with the smearing of the spin-spin interaction. The radius of smearing is fixed by the known $J/psi-eta_c(1S)$ and $psi(2S)-eta_c(2S)$ splittings and appears to be small, $r_{ss} cong 0.06$ fm. Nevertheless, even with such a small radius an essential suppression of the hyperfine splittings ($sim 50%)$ is observed in bottomonium. For the $nS~ bbar b$ states $(n=1,2,...,6)$ we predict the values (in MeV) 28, 12, 10, 6, 6, and 3, respectively. For the $3S$ and $4S$ charmonium states the splittings 16(2) MeV and 12(4) MeV are obtained.
rate research
Read More
The Light-front quark model (LFQM) has been applied to calculate the transition matrix elements of heavy hadron decays. However, it is noted that using the traditional wave functions of the LFQM given in literature, the theoretically determined decay constants of the $Upsilon(nS)$ obviously contradict to the data. It implies that the wave functions must be modified. Keeping the orthogonality among the $nS$ states and fitting their decay constants we obtain a series of the wave functions for $Upsilon(nS)$. Based on these wave functions and by analogy to the hydrogen atom, we suggest a modified analytical form for the $Upsilon(nS)$ wave functions. By use of the modified wave functions, the obtained decay constants are close to the experimental data. Then we calculate the rates of radiative decays of $Upsilon(nS)to eta_b+gamma$. Our predictions are consistent with the experimental data on decays $Upsilon(3S)to eta_b+gamma$ within the theoretical and experimental errors.
We consider a holographic model constructed through using the D4/D8-$bar{rm D8}$ brane configuration with a background field. We study some properties of the effective field theory in this intersecting brane construction, and calculate the effects of this NS-NS background field on some underlying dynamics. We also discuss some other general brane configurations.
We study the transformations of the worldvolume fields of a system of multiple coinciding D-branes under gauge transformations of the supergravity Kalb-Ramond field. We find that the pure gauge part of these NS-NS transformations can be written as a U(N) symmetry of the underlying Yang-Mills group, but that in general the full NS-NS variations get mixed up non-trivially with the U(N). We compute the commutation relations and the Jacobi identities of the bigger group formed by the NS-NS and U(N) transformations.
Based on previous studies that support the vector-vector molecular structure of the $f_2(1270)$, $f_2(1525)$, $bar{K}^{*,0}_2(1430)$, $f_0(1370)$ and $f_0(1710)$ resonances, we make predictions for $psi (2S)$ decay into $omega(phi) f_2(1270)$, $omega(phi) f_2(1525)$, $K^{*0}(892) bar{K}^{*,0}_2(1430)$ and radiative decay of $Upsilon (1S),Upsilon (2S), psi (2S)$ into $gamma f_2(1270)$, $gamma f_2(1525)$, $gamma f_0(1370)$, $gamma f_0(1710)$. Agreement with experimental data is found for three available ratios, without using free parameters, and predictions are done for other cases.
We argue that the Black Hole-Neutron Star (BH-NS) binaries are the natural astrophysical probes of quantum gravity in the context of the new era of multi-messenger astronomy. In particular, we discuss the observable effect of enhanced black-hole mass loss in a BH-NS binary, due to the presence of an additional length scale tied to the intrinsic non-commutativity of quantum spacetime in quantum gravity.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
