arXiv subjects

A. N. Hiller Blin

Publications and source records attributed to A. N. Hiller Blin.

24 records · Page 2Linked to original sources

arXiv2017

Peripheral transverse densities of the baryon octet from chiral effective field theory and dispersion analysis

The baryon electromagnetic form factors are expressed in terms of two-dimensional densities describing the distribution of charge and magnetization in transverse space at fixed light-front time. We calculate the transverse densities of the spin-1/2 flavor-octet baryons at peripheral distances b = O(M_π^{-1}) using methods of relativistic chiral effective field theory (χEFT) and dispersion analysis. The densities are represented as dispersive integrals over the imaginary parts of the form factors in the timelike region (spectral functions). The isovector spectral functions on the two-pion cut t > 4 M_π^2 are calculated using relativistic χEFT including octet and decuplet baryons. The χEFT calculations are extended into the ρmeson mass region using an N/D method that incorporates the pion electromagnetic form factor data. The isoscalar spectral functions are modeled by vector meson poles. We compute the peripheral charge and magnetization densities in the octet baryon states, estimate the uncertainties, and determine the quark flavor decomposition. The approach can be extended to baryon form factors of other operators and the moments of generalized parton distributions.

hep-ph↗

arXiv2017

Pentaquark photoproduction

We present results and suggestions on how to confirm the existence and resonant nature of the $Pc(4450)$ detected at LHCb through photoproduction experiments. We find that this narrow structure might have escaped detection in past experiments and use those to give a constraint for the upper limit of the branching ratio/coupling to the $J/ψp$ channel.

hep-ph↗

arXiv2016

$ϕ$ meson self-energy in nuclear matter from $ϕN$ resonant interactions

The $ϕ$-meson properties in cold nuclear matter are investigated by implementing resonant $ϕN$ interactions as described in effective approaches including the unitarization of scattering amplitudes. Several $N^*$-like states are dynamically generated in these models around $2$ GeV, in the vicinity of the $ϕN$ threshold. We find that both these states and the non-resonant part of the amplitude contribute sizably to the $ϕ$ collisional self-energy at finite nuclear density. These contributions are of a similar strength as the widely studied medium effects from the $\bar K K$ cloud. Depending on model details (position of the resonances and strength of the coupling to $ϕN$) we report a $ϕ$ broadening up to about $40$-$50$ MeV, to be added to the $ϕ\to\bar K K$ in-medium decay width, and an attractive optical potential at threshold up to about $35$ MeV at normal matter density. The $ϕ$ spectral function develops a double peak structure as a consequence of the mixing of resonance-hole modes with the $ϕ$ quasi-particle peak. The former results point in the direction of making up for missing absorption as reported in $ϕ$ nuclear production experiments.

nucl-th↗

arXiv2016

Studying the P_c(4450) resonance in J/psi photoproduction off protons

A resonance-like structure, the P_c(4450), has recently been observed in the J/psi p spectrum by the LHCb collaboration. We discuss the feasibility of detecting this structure in J/psi photoproduction in the CLAS12 experiment at JLab. We present a first estimate of the upper limit for the branching ratio of the P_c(4450) to J/psi p. Our estimates, which take into account the experimental resolution effects, predict that it will be possible to observe a sizable cross section close to the J/psi production threshold and shed light on the P_c(4450) resonance in the future photoproduction measurements.

hep-ph↗

arXiv2016

$Δ(1232)$ resonance in the $\vecγp\rightarrow pπ^0$ reaction at threshold

We calculate the neutral pion photoproduction on the proton near threshold in covariant baryon chiral perturbation theory, including the $Δ(1232)$ resonance as an explicit degree of freedom, up to chiral order $p^{7/2}$ in the $δ$ counting. We compare our results with recent low-energy data from the Mainz Microtron for angular distributions and photon asymmetries. The convergence of the chiral series of the covariant approach is found to improve substantially with the inclusion of the $Δ(1232)$ resonance.

hep-ph↗

arXiv2015

Chiral dynamics in the gamma p --> p pi0 reaction

We investigate the neutral pion photoproduction on the proton near threshold in covariant chiral perturbation theory with the explicit inclusion of Delta degrees of freedom. This channel is specially sensitive to chiral dynamics and the advent of very precise data from the Mainz microtron has shown the limits of the convergence of the chiral series for both the heavy baryon and the covariant approaches. We show that the inclusion of the Delta resonance substantially improves the convergence leading to a good agreement with data for a wider range of energies.

hep-ph↗