Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userElectromagnetic proton form factors in dual large-$N_c$ QCD: an update
277
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
An updated determination is presented of the electric and magnetic form factors of the proton, in the framework of a dual-model realization of QCD in the limit of an infinite number of colors. Very good agreement with data is obtained in the space-like region up to $ q^2 simeq - ,30 ,{GeV}^2$. In particular, the ratio $mu_P , G_E(q^2) / G_M(q^2)$ is predicted in very good agreement with recoil polarization measurements from Jefferson Lab, up to $q^2 simeq - 8.5 ,{GeV}^2$. end{abstract}
rate research
Read More
The electromagnetic form factors of the proton are obtained using a particular realization of QCD in the large $N_c$ limit (${QCD}_{infty}$), which sums up the infinite number of zero-width resonances to yield an Eulers Beta function (Dual-${QCD}_{infty}$). The form factors $F_1(q^2)$ and $F_2(q^2)$, as well as $G_M(q^2)$ agree very well with reanalyzed space-like data in the whole range of momentum transfer. In addition, the predicted ratio $mu_p G_E/G_M$ is in good agreement with recent polarization transfer measurements at Jefferson Lab.
The nucleon electromagnetic form factors are calculated in light cone QCD sum rules framework using the most general form of the nucleon interpolating current. Using two forms of the distribution amplitudes (DAs), predictions for the form factors are presented and compared with existing experimental data. It is shown that our results describe remarkably well the existing experimental data.
The electromagnetic form factors of the proton and the neutron are computed within lattice QCD using simulations with quarks masses fixed to their physical values. Both connected and disconnected contributions are computed. We analyze two new ensembles of $N_f = 2$ and $N_f = 2 + 1 + 1$ twisted mass clover-improved fermions and determine the proton and neutron form factors, the electric and magnetic radii, and the magnetic moments. We use several values of the sink-source time separation in the range of 1.0 fm to 1.6 fm to ensure ground state identification. Disconnected contributions are calculated to an unprecedented accuracy at the physical point. Although they constitute a small correction, they are non-negligible and contribute up to 15% for the case of the neutron electric charge radius.
Accessing hadronic form factors at large momentum transfers has traditionally presented a challenge for lattice QCD simulations. Here we demonstrate how a novel implementation of the Feynman-Hellmann method can be employed to calculate hadronic form factors in lattice QCD at momenta much higher than previously accessible. Our simulations are performed on a single set of gauge configurations with three flavours of degenerate mass quarks corresponding to $m_pi approx 470 text{ MeV}$. We are able to determine the electromagnetic form factors of the pion and nucleon up to approximately $6 text{ GeV}^2$, with results for $G_E/G_M$ in the proton agreeing well with experimental results.
We develop techniques to calculate the four Delta electromagnetic form factors using lattice QCD, with particular emphasis on the sub-dominant electric quadrupole form factor that probes deformation of the Delta. Results are presented for pion masses down to approximately 350 MeV for three cases: quenched QCD, two flavors of dynamical Wilson quarks, and three flavors of quarks described by a mixed action combining domain wall valence quarks and dynamical staggered sea quarks. The magnetic moment of the Delta is chirally extrapolated to the physical point and the Delta charge density distributions are discussed.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
