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1、N* Production in -p and p-p Scattering (Study of the Breathing Mode of the Nucleon),Investigation of the Scalar Structure of baryons (related to strong non-valence quark excitations),H.P. Morsch, MENU2004,Comparison with operator sum rules: Cross section covers maximum monopole strength Extraction o
2、f the baryon compressibility, KB 1.3 GeV,First evidence for the breathing mode of the nucleon from -p scattering at SATURNE (Phys.Rev.Lett. 69,1336 (1992),Strong L=0 excitation in the region of the P11(1440),Projectile excitation,Points to be discussed:,Theoretical studies of a low lying P11 resonan
3、ce Results of -p experiment What are the properties of the Roper resonance? Roper resonance contains 2 structures: 1. Radial mode 2. Second order excitation New analysis of p-p scattering at beam momenta 5-30 GeV/c What can we learn about the baryon structure from this excitation? Comparison with th
4、e longitudinal e-p amplitude S1/2 Summary,1.Theoretical studies of a low lying P11 resonance,Constituent quark model: Gluon exchange Pion exchange Relativistic quark model Bag model Skyrmion model Algebraic models Hybrid structure P11 generated by strong -N interaction Lattice QCD calculations,1s2s
5、transition mass of P11 high mass of P11 lower mass of P11 right (adjusted) (oscillation of the bag) P11 is the lowest N* excitation (flat top) J=1/2+ is lowest state not confirmed by new e-p data P11 contains valence quark contribution!,2. Saturne experiment -p scattering,Observation of a strong mon
6、opole excitation in the P11(1440) region Analysis in terms of operator sum rules S1=energy weighted sum S-1= energy inversely weighted sum H.P.Morsch, Z.Phys. A350, 61 (1994) Results of DWBA calculations: P11 excitation covers the full sum S1 Transition density not compatible with valence quark pict
7、ure! H.P.Morsch et al., Phys.Rev. C67, 064001 (2003),3. What are the properties of the Roper resonance?,Shape of the resonance in a-p different from pi-N: mo1440 MeV, 300-360 MeV in -N mo1390 MeV, 190 MeV in -p,T-matrix description of -p and -N scattering H.P.Morsch and P.Zupranski, Phys.Rev.C61,024
8、002 (99),Two resonance picture consistent with -p2o p (radial mode not excited),new helicity amplitudes from Mainz!,4.New analysis of p-p scattering at beam momenta 5-30 GeV/c,Contibuting resonances 33 (1232) D13 (1520), F15 (1680), strong res. at 1400 MeV,Strongest resonance at 1400 MeV, width 200
9、MeV,No other resonance seen (high selectivity),What are position and width of the strong resonance?,Resonance parameters: mo =140010 MeV = 200 20 MeV,Position and width consistent with Saturne resonance observed in -p scattering,What is the evidence for P11 ? What are the decay modes?,change of mo,c
10、hange of width,What is the evidence for P11?,Information from the t-dependence of the p-p differential cross section,Resonance at 1400 MeV is strongly peaked at small momentum transfer t Characteristic for L=0 excitation !, P11 resonance,Calculation of the differential cross sections in DWBA using a
11、n effective interaction described by multi-gluon exchange (adjusted to fit elastic p-p scattering) Cross section covers the full energy weighted sum rule, consistent with -p!,What are the decay modes of the P11 resonance at 1400 MeV ?,Information from exclusive experiments: 2 prong events: p-p p N*
12、with N* p o and n +,Large yields observed for D13 (1520) and F15(1680) consistent with -N (elast. width 60% and 70%, resp.),4 prong events: p-p p N* with N* p + -,Strong peak above 2 threshold,Description of the + - invariant mass spectrum consistent with the inclusive p-p p N* spectra:,Strong contr
13、ibution from the P11 resonance at 1400 MeV Estimated 2 branching B2= 7520%,5. What can we learn about the baryon structure from excitation of the P11(1400)?,Sensitivity of the calculated differential cross sections to the nucleon transition density,Quantitative description of the data requires a sur
14、face peaked transition density tr(r) (consistent with the results from -p),Transition density not consistent with pure valence quark excitation (constituent quark model),How can we understand the surface peaked transition density?,How can we understand the observed transition density?,1. Excitation
15、of valence quarks 2. Strong sea quark contribution,Sea quark contribution much stronger (factor 4) than that of the valence quarks!,The breathing“ of the sea quark contribution indicates its existence also in the g.s. density,What do we learn from the longitudinal electron scattering amplitude S1/2?
16、 (data from JLab),Comparison with the longitudinal e-p amplitude S1/2 for the Roper resonance excitation,C.Smith, NSTAR2004, I.G.Aznauryan, V.D.Burkert, et al., nucl-th/0407021, L.Tiator, Eur.J.Phys.16 (2004),Transition density for the description of S1/2 requires: 1. valence quark excitation 2. sea quark component,Direct relation of t
