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Excitation of the Roper Resonance in Single- and Double-Pion Production in NN collisions

Excitation of the Roper Resonance in Single- and Double-Pion Production in NN collisions. NSTAR, Bonn 2007. Heinz Clement. Roper‘s resonance a resonance without seeing it: p N and g N and what the „bible“ tells us new generation of experiments: visualizing a „narrow“ Roper

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Excitation of the Roper Resonance in Single- and Double-Pion Production in NN collisions

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  1. Excitation of the Roper Resonance in Single- and Double-Pion Productionin NN collisions NSTAR, Bonn 2007 Heinz Clement Roper‘s resonance a resonance without seeing it: pN and gN and what the „bible“ tells us new generation of experiments: visualizing a „narrow“ Roper p production in pp collisions: D and N* pp production: N* decay branchings

  2. Why is the Roper resonance special? • N*(1440) : • lowest N* excitation • same quantum numbers as N  • monopole excitation (breathing mode) of N ? •  compressibility of the nucleon (quark matter) • nature of Roper not well understood • lattice QCD not able to come close to experiment • quark and other models have problems either

  3. Roper´s pN Resonance

  4. Roper´s pN Resonance • 900 crossing of phase shifts: Tlab M (MeV) (MeV) • P33: 193 1234 D(1232) • P11: 556 1485 N(1440) • D13: 676 1559 N(1520) Roper, PRL 12, 340 (1964)

  5. How to excite the Roper? • N → N* (1440) I( Jp ): ½( ½ )+ → ½( ½ )+  • scalar-isoscalar excitation: s or • isovectorexcitation: p, r, g (M1) with spinflip preferred

  6. Where to see? D D13(1520) … • gN • photo absorption • gp → p p0p0 • Where is the Roper? Morsch and Zupranski, PRC 61, 024002 (1999)

  7. 2. resonance region D13(1520) … Where to see? D 3. resonance region F15(1680) … • pN scattering: • Where is the Roper? I=3/2 I=1/2 I=1/2, 3/2 PDG 2006

  8. p- p total cross section Where is the Roper? SAID data base

  9. pN partial wave analysis • Argand plot SAID nucl-th/0605082 • Partial wave amplitudes imag real Re A here is theRoper : Mpole = 1357 MeV Gpole = 160 MeV Bonn (Sarantsev et al.): 1371 (2) pN + gN 184 (20) imag real

  10. What does the „Bible“ tell us today? PDG 2006:

  11. New Generation of Experiments visualizing a „narrow“ Roper (?) • a p → a X @ 4.2 GeV (Saturne) • J/y → N N* and N N* (BES) • pp → npp+ @ 1.1 and 1.3 GeV (WASA)

  12. New Generation of Experiments:1. a p → a X (Saclay) G 190 MeV G 400 MeV • scalar-isoscalar probe a however: • interfering background from projectile excitation Hirenzaki et al., PRC 53, 277 (1996) Morsch et al., PRL 69, 1336 (1992) and PRC 61, 024002 (1999)

  13. New Generation of Experiments:2. J/y → N N* and N N*(BES) n pp- and pp+ n events  I= 1/2 N* excitations only Roper M=1358(6,16) MeV G=179(26,50) MeV Ablikim et al., PRL 97 (2006) 062001 hep-ex/0405030

  14. New Generation of Experiments:3. pp → npp+ @ 1.1 and 1.3 GeV (WASA) • angular momentum and isospin coupling  • Roperfavored in ppp- and in particular in npp+ • beam energy allows only D and Roper excitations  • no kinematic reflections • clean and simple situation • scalar-isoscalar (s) excitation of Roper possible • pp+ invariant mass: I=3/2  only D++ • np+ : I=1/2, 3/2  Roper (D0 very weak)

  15. 3. pp → npp+(WASA) Mpp+Mnp+ Roper D • Tp = 1.1 GeV • Tp = 1.3 GeV • Data prefer Roper values: • M  1350 MeV •  140 MeV (nucl-ex/0612015)

  16. D++ and D+ only Roper Dalitz plots MC pp → npp+ @ 1.3 GeV • D++ , D+, Roper Mnp+ 2 Mpp+ 2

  17. data MC („through detector“) Dalitz Plots pp → npp+ @ 1.3 GeV( not corrected) Mnp+ 2 Mpp+ 2

  18. Decay of Roper • decay channels: BR(1440) BR(1371) PDG 2006 Bonn 2007 (Sarantsev et al.) • N* → Np 0.55 – 0.75 0.61 (2) • N* → Npp 0.30 – 0.40 0.39 (5) • → Dp → Npp 0.20 – 0.30 0.18 (2) • → Nr → N(pp)I=L=1 < 0.08 • → Ns → N(pp)I=L=0 0.05 – 0.10 0.21 (3) • N* → Dp / N* → Ns :2 – 60.9 (2) PRC 67 ( 2003 ) 052202(Pätzold et al) • N* → Npp: look in pp → pp* → pppp : 1.0 (1)

  19. pp production Status quo ante:experimental and theoretical situation DD Roper chiral dynamics

  20. PROMICE / WASA • Tp = 650 – 775 MeV Phys. Rev. Lett. 88 (2002) 192301 Nucl. Phys. A 712 (2002) 75 Phys. Lett. B 550 (2002) 147 Phys. Rev. C 67 (2003) 052202 Rapid Comm. many conference contributions Sarantsev et al. WASA preliminary • WASA • Tp = 775 – 1450 MeV • M. Bashkanov • T. Skorodko

  21. pp Production: pp → ppp0p0 • Energy dependence of total cross section DD Valencia N*→Ns Roper N*→Dp No good description of differential data !!! WASA PROMICE/WASA bubble chamber data

  22. pp Production: pp → ppp0p0 • Energy dependence of total cross section DD N*→Ns Roper N*→Dp … gives better description of differential data WASA PROMICE/WASA bubble chamber data

  23. Angular distributions cos Qpcm cos Qpcm 775 MeV 775 MeV 900 MeV 900 MeV 1000 MeV 1100 MeV 1000 MeV 1100 MeV 1200 MeV 1300 MeV 1200 MeV 1300 MeV

  24. Invariant Mass distributions Mp0p0 Mpp0 775 MeV 900 MeV 775 MeV 900 MeV 1000 MeV 1100 MeV 1000 MeV 1100 MeV 1200 MeV 1300 MeV 1200 MeV 1300 MeV

  25. threshold region:p+p-Roperexcitation and decay ( conventional analysis ) d d PRC 67 ( 2003 ) 052202 < < ) jkkjmmmmmmlllllllllllllll ) “s“ D N* N* Branching Ratio @ pole: 1440 1350 MeV N*→Dp / N*→Ns = 3.4 (3) 0.6 (1) PDG 4 (2)

  26. Roper Pole CELSIUS-WASApp → ppp+p- Ipp= 0,1 pp → ppp0p0Ipp = 0 Tp = 775 MeV Tp = 900 MeV  N* → Npp dominantly N → Ns ! ( nucl-ex/0612015) ∙∙∙∙∙∙∙∙ BR(Dp/Ns) = 1 : 2 Ipp = 0 + 1 ―—— BR(Dp/Ns) = 1 : 8 Ipp = 0

  27. Conclusions (1) • Roper Resonance historically: • Originally found in pN phase shifts of P11 partial wave • Interpretation as a Breit-Wigner resonance in pN  M  1440 MeV, G  400 MeV • Not seen in total cross sections of pN and gN systems • A more narrow structure ( M  1400 MeV, G  200 MeV) seen in inclusive pp and pp reactions at small Q2 • kinematic reflection or characteristics of breathing mode ???

  28. Conclusions (2) • Roper resonance now: M G (MeV) • SAID pN partial wave analysis: 1357 160 • Bonn (Sarantsev et al)pN + gN 1371(2) 184(20) • Explicitly seen in: • a p → a X 1390 190 (?) • J/y → n pp- 1358 160 • p p → p np+ 1350 140 • Roper decay N* → N pp • pp → NNpp dominantlyN* → N s

  29. Conclusions (3) • Scalar-isoscalar probes (s exchange) see „narrow“ monopole excitation at very low excitation energy : breathing mode @w  400 MeV ! i.e. only 100 MeV above D, the lowest excited state

  30. pp production in NN collisions • threshold region: Roper • Tp > 1 GeV: DD

  31. DD regionpp → ppp+p-@Tp = 1360 MeV DD prediction (DD)0+

  32. Inclusive Differential Measurements D13 F15 • p- + p: 8 and 16 GeV/c • Enhancement near MM  1400 MeV G 200 MeV however, only at small momentum transfer! • p + p: 6 – 30 GeV/c • Similar situation! • Is this connected with the Roper? small momentum transfer larger momentum transfer Anderson et. al, PRL 25, 699 (1970)

  33. 1. answer: No • Observed structure in inclusive measurements due to kinematic reflection of p-p scattering at one vertex Deck model PRL 13, 169 (1964)  • pp → ppX: • not pp → p N* • but pp → D++ (pp-)rescatt → pp+ pp- • pp → ppp+p- @ 6.6 GeV/c: • pp- production associated with peripheral D++ production Gellert et al., PRL 16, 884 (1966) N* D++ pp → D++ pp- Mpp+p-

  34. 2. answer: Yes (cont.) • Reanalysis of inclusive data on pp → pp X and pp → pp X • Resumé: structure at 1400 MeV decreases rapidly with increasing four-momentum transfer t Morsch and Zupranski, PRC 71, 065203 (2005)

  35. N → N*(1440): monopole transition (breathing mode)  transition density has node  formfactor has very steep t-dependence at low t Morsch and Zupranski, PRC 71, 065203 (2005) 2. answer: Yes (cont.)

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