Prague SPIN 05 1

Study of inelastic p- and dp- scattering in Roper resonance region

A.N.Prokofyev

Petersburg Nuclear Physics Institute

and SPES4- Collaboration

Prague SPIN 05 2

• Inelastic p- and dp-scattering reactions were studied in the energy region of Roper resonance excitation. Due to the spin and isospin conservation there are only two dominant channels which are open for this reaction: production at the projectile and N* production at the target. A simultaneous registration of the scattered projectile and the secondaries allowed to separate one- and two pions decay of the intermediate state and pick out the 2 channel, which is exclusively connected with the N* baryon intermediate state.

• The shape of the obtained 2 invariant mass spectra was compared with the Oset-Fernandez calculation predictions. It was found that the decay of N* is predominantly going through the spin-isospin scalar state The contribution of the decay through intermediate (N* - N) is small.

• The experiment was carried out at - and d-beams of the Saturne-II accelerator (Saclay). The scattered particles were registered using the SPES4 high resolution spectrometer (projectiles) and wide aperture Forward spectrometer (secondary protons nad pions).

Prague SPIN 05 3

Main Feynman diagrams for p->’N* (dp->d’N*) reaction.

E.Oset, P.Fernandez et al.

•a. isobar excitation at projectile.

•b,c. N* excitation at the target.

Prague SPIN 05 4

The ’ particle spectra for p-inelastic scattering asa function of energy transferred .

Result of the inclusive measurement at Saturne-II -beam.H.P.Morsch et al., PRL 69 (1992) 1326.

Prague SPIN 05 5

SPES4- installation general view(not on scale)

Prague SPIN 05 6

Forward spectrometer of SPES4- installation.(not in scale)

• ST – straw tube hodoscopes

• X, Y, U, V – drift chambers

Prague SPIN 05 7

Forward spectrometer of SPES4- installationDrift chamber telescope spatial resolution

• a) Resolution in the “proportion chamber” mode.

• b) Resolution in the “drift chamber” mode,0.15 mm.

Prague SPIN 05 8

Reaction p

• Four accepted momentum intervals in comparison with the scale of previous inclusive measurement made by H.P.Morsch.

Prague SPIN 05 9

Resonance masses accepted by

SPES4 and SPES4+FS spectrometers

at different momentum settings.

Prague SPIN 05 10

p-reaction

• Missing mass squared spectra for 4 accepted momentum intervals:

• A) secondary protons detected

• B) secondary pions detected

Prague SPIN 05 11

• Missing mass squared spectra from alpha-p reaction at 4 different momentum settings.

• Secondary protons and pions are detected by Forward spectrometer.

Prague SPIN 05 12

• Angular distribution for protons at momentum setting p/z=3.06 GeV/c.

• Upper plot – MC simulation,

• Lower plot – experimental data.

Prague SPIN 05 13

• Angular distribution of the protons from 2-pi production channel.

• MC simulation and experimental data are presented.

• All momentum settings are included.

Prague SPIN 05 14

• Missing mass squared distributions for forward (solid lines) and backward protons for different reaction channels. MC simulations.

Prague SPIN 05 15

• MM squared distribution for forward and backward protons at momentum setting p/z=3.06GeV/c.

• MC calculations (solid line) and Experimental data are presented.

Prague SPIN 05 16

• Resonance mass distribution. MC simulation with N* (left) and N*+ D13 resonance (right).

Prague SPIN 05 17

N* resonance mass distribution for 2-pions production. P11 and D13 resonance are taken into considerationSetting p/z=3.06 GeV/c

Prague SPIN 05 18

p-reactionManley approach for two-pions decay of Roper resonance

from: E.Hernandez et al.,PRC 65 (2002) 65201

• Feinman diagrams for two main processes contributing to Roper resonance decay into two pions in Manley approach: Diagram amplitude is proportional to (k1.k2).

• a) – intermediate state.

• b) N() – intermediate state

Prague SPIN 05 19

p-reactionManley approach for two-pions decay of Roper resonance

from: E.Hernandez et al., PRC (2002) 65201

Prague SPIN 05 20

2-pion decay channel from p X N in the Roper resonance region.

(in collaboration with G.D. Alkhazov and A.V. Kravtsov)

Comparison with Oset-Fernandez theory predictions.

The results agree with pure phase space calculations and, therefore, with a decay through a scalar intermediate state (solid line). The decay through the intermediate state is rejected (thin dotted line in the upper plot).

Prague SPIN 05 21

dp-reaction

Prague SPIN 05 22

dp-reaction

Prague SPIN 05 23

SUMMARY• The p and dp inelastic scattering reactions were exclusively

studied in the energy transfer region corresponded to the Roper resonance excitation region.

• The registration of the scattered projectiles, as well as the charged secondaries allowed to separate different final states, connected with one and two pions production.

• The data in a region, where the Roper resonance production was expected, demonstrate the dominance of the two pion decay of the intermediate N* state . This can be interpreted as the N* (1440 MeV) baryon production. The next possible baryon state D13(1520 Mev) does not fit the data.

• The comparison of the invariant M mass spectra with the theory predictions demonstrates the dominance of the N* decay through the spin, isospin scalar state The contribution of the decay through the Delta resonance is small. This result is in agreement with the data obtained in pp inelastic scattering study at Uppsala.