Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userThe K-matrix approach to the Delta - resonance mass splitting and isospin violation in low-energy pi-N scattering
67
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The experimental data on pi N scattering in the elastic energy region T_pi < 250 MeV are analyzed within the multichannel K-matrix approach with effective Lagrangians. Isospin invariance is not assumed in this analysis and the physical values for masses of the involved particles are used. The corrections due to pi^+- pi^0 and p-n mass differences are calculated and found to be in a reasonable agreement with the NORDITA results. Analysis shows the good description of the all experimental observables. From the data, new values for mass and width of the Delta^0 and Delta^{++} resonances were obtained. The isospin symmetric version gives phase shifts values close to the new solution for the pi-N elastic scattering amplitude FA02 by the GW group based on the latest experimental data. Our analysis leads to a considerably smaller < 1% isospin violation in the energy interval T_pi ~ 30-70 MeV as compared to 7% in some older analyses, however, it does confirm recent calculations based on chiral perturbation theory.
rate research
Read More
We study the Dalitz plot of the decay D^+ --> K^- pi^+ pi^+ with a sample of 15090 events from Fermilab experiment E791. Modeling the decay amplitude as the coherent sum of known K pi resonances and a uniform nonresonant term, we do not obtain an acceptable fit. If we allow the mass and width of the K^*_0(1430) to float, we obtain values consistent with those from PDG but the chi^2 per degree of freedom of the fit is still unsatisfactory. A good fit is found when we allow for the presence of an additional scalar resonance, with mass 797 +/- 19 +/- 43 MeV/c^2 and width 410 +/- 43 +/- 87 MeV/c^2. The mass and width of the K^*_0(1430) become 1459 +/- 7 +/- 5 MeV/c^2 and 175 +/- 12 +/- 12 MeV/c^2, respectively. Our results provide new information on the scalar sector in hadron spectroscopy.
The proposed $e^+e^-$-collider FCC-ee aims at an unprecedented accuracy for $e^+e^-$ collisions into fermion pairs at the $Z$ peak, based on about $10^{13}$ events. The S-matrix approach to the $Z$ boson line shape allows the model-independent quantitative description of the reaction $e^+e^- to {bar f}f$ around the $Z$ peak in terms of few parameters, among them the mass $M_Z$ and width $Gamma_Z$ of the $Z$-boson. While weak and strong corrections remain black, a careful theoretical description of the photonic interactions is mandatory. I introduce the method and describe applications and the analysis tool SMATASY/ZFITTER.
In this project, we will compute the form factors relevant for $B to K^*(to K pi)ell^+ell^-$ decays. To map the finite-volume matrix elements computed on the lattice to the infinite-volume $B to K pi$ matrix elements, the $K pi$ scattering amplitude needs to be determined using Luschers method. Here we present preliminary results from our calculations with $2+1$ flavors of dynamical clover fermions. We extract the $P$-wave scattering phase shifts and determine the $K^*$ resonance mass and the $K^* K pi$ coupling for two different ensembles with pion masses of $317(2)$ and $178(2)$ MeV.
We study two rare decays, $Z to pi^+pi^-$ and $K^+K^-$, in the perturbative QCD approach up to the next-to-leading order of the strong coupling and the leading power of $1/m_Z$, $m_Z$ being the $Z$ boson mass. The branching ratios $mathcal{B}(Zto pi^+pi^-) = (0.83 pm 0.02 pm 0.02 pm 0.04)times 10^{-12}$ and $mathcal{B}(Zto K^+K^-) = (1.74^{+0.03}_{-0.05} pm 0.04 pm 0.02)times 10^{-12}$ are obtained and can be measured at a tera-$Z$ factory. Because the subleading-power contributions to the branching ratios are negligible, and the leading one does not depend on any free parameter, the two channels can serve as a touchstone for the applicability of the perturbative QCD approach.
In this paper we study the direct CP asymmetry of the doubly Cabibbo-suppressed decay mode $D^0 to K^+ pi^- $ within standard model and two Higgs doublet model with generic Yukawa structure. In the standard model we derive the corrections to the tree level amplitude, generated from the box and di-penguin diagrams, required for generating the weak CP violating phases. We show that these phases are so tiny leading to a direct CP asymmetry of order $10^{-9}$. Regarding the two Higgs doublet model with generic Yukawa structure we derive the Wilson coefficients relevant to $D^0 to K^+ pi^- $. After taking into account all constraints on the parameter space of the model we show that charged Higgs couplings to quarks can lead to a direct CP asymmetry of order $10^{-3}$ which is $6$ orders of magnitude larger than the standard model prediction.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
