New measurement by CELSIUS-WASA Collaboration on the pp → pnπ+ reaction reveals clear evidence for the presence of the Roper resonance N∗(1440) which has been ignored in previous theoretical calculations. In this article, based on an effective Lagrangian approach and available knowledge on the Roper resonance, we investigate the role of the Roper resonance for the pp → pnπ+ reaction. It is foun...

Recent experiments at Saturne at 4 GeV showed that the (α, α ′) reaction on the proton shows two distinctive peaks, which were associated to ∆ projectile excitation and Roper target excitation. A subsequent theoretical analysis has shown that this picture is qualitatively correct but there are important interference effects between the two mechanisms. Futhermore, at this energy the ratio of str...

We study the Roper excitation in the (α, α ′) reaction. We consider all processes which may be relevant in the Roper excitation region, namely, Roper excitation in the target, Roper excitation in the projectile, and double ∆ excitation processes. The theoretical investigation shows that the Roper excitation in the proton target mediated by an isoscalar exchange is the dominant mechanism in the ...

The P11(1440) (Roper) resonance 1 is the lowest positive-parity N state, most clearly visible in partial-wave decompositions of πN → πN and πN → ππN scattering, as well as in pion photoproduction. Although this four-star resonance is within the energy reach of many modern research facilities, the experimental analyses so far have not ventured beyond the determination of its mass, width, and ele...

We study the electromagnetic transitions of the Roper N(1440) resonance. Our results, when combined with the previously obtained for the mass and the pionic strong decay widths of the Roper, show that within a non-relativistic constituent quark model scheme, a comprehensible understanding of the Roper phenomenology can be achieved. They also seem to support the view of the Roper as a radial exc...

New measurement by CELSIUS-WASA Collaboration on the pp → pnπ+ reaction reveals clear evidence for the presence of the Roper resonance N∗(1440) which has been ignored in previous theoretical calculations. In this article, based on an effective Lagrangian approach and available knowledge on the Roper resonance, we investigate the role of the Roper resonance for the pp → pnπ+ reaction. It is foun...

We calculate differential cross sections and the spin transfer coefficient D nn in the p+α → p+α+π 0 reaction for proton bombarding energies from 1 to 10 GeV and π 0 − p invariant masses spanning the region of the N * (1440) Roper resonance. Two processes – ∆ excitation in the α-particle and Roper excitation in the proton – are included in an effective reaction model which was shown previously ...

We analyze the quark mass dependence of the Roper mass to one-loop order in relativistic baryon chiral perturbation theory. The loop integrals are evaluated using infrared regu-larization which preserves chiral symmetry and establishes a chiral counting scheme. The derived chiral expansion of the Roper mass may prove useful for chiral extrapolations of lattice data. For couplings of natural siz...