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

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

Roper´s  N Resonance

90 0 crossing of phase shifts: 90 0 crossing of phase shifts: T lab M T lab M (MeV) (MeV) (MeV) (MeV) P 33 :  (1232) P 33 :  (1232) P 11 : N(1440) P 11 : N(1440) D 13 : N(1520) D 13 : N(1520) Roper, PRL 12, 340 (1964)

How to excite the Roper? N → N * (1440) N → N * (1440) I( J p ): ½( ½ ) + → ½( ½ ) + I( J p ): ½( ½ ) + → ½( ½ ) +  scalar-isoscalar excitation:  scalar-isoscalar excitation:  or or isovector excitation: , ,  (M1) isovector excitation: , ,  (M1) with spinflip preferred with spinflip preferred

Where to see?  N  N photo absorption photo absorption  p → p      p → p     Where is the Roper? Where is the Roper? Morsch and Zupranski, PRC 61, (1999)  D 13 (1520) …

Where to see?  N scattering:  N scattering: Where is the Roper? Where is the Roper? PDG 2006  2. resonance region D 13 (1520) … 3. resonance region F 15 (1680) … I=3/2 I=1/2, 3/2 I=1/2

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

 N partial wave analysis Partial wave amplitudes Partial wave amplitudes Re A SAID nucl-th/ here is theRoper : M pole = 1357 MeV M pole = 1357 MeV  pole = 160 MeV  pole = 160 MeV Bonn (Sarantsev et al.): 1371 (2)  N +  N 184 (20)  N +  N 184 (20)  Argand plot real imag real imag

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

New Generation of Experiments visualizing a „narrow“ Roper (?)  p →  4.2 GeV (Saturne)  p →  4.2 GeV (Saturne) J/  → N N * and N N * (BES) J/  → N N * and N N * (BES) pp → np  1.1 and 1.3 GeV (WASA) pp → np  1.1 and 1.3 GeV (WASA)

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

New idea: Roper is two resonances  (M=1480,  =380 MeV)  excited in  N  (M=1480,  =380 MeV)  excited in  N  N  (M=1390,  =190 MeV)  not -“-  N  (M=1390,  =190 MeV)  not -“- Morsch and Zupranski, PRC 61, (1999)

New Generation of Experiments: 2. J/  → N N * and N N * (BES) n p   and p   n events  I= 1/2 N * excitations only Ablikim et al., PRL 97 (2006) hep-ex/ Roper M=1358(6,16) MeV  =179(26,50) MeV  =179(26,50) MeV

New Generation of Experiments: 3. pp → np  1.1 and 1.3 GeV (WASA) angular momentum and isospin coupling  angular momentum and isospin coupling  Roper favored in pp   and in particular in np   Roper favored in pp   and in particular in np   beam energy allows only  and Roper excitations  beam energy allows only  and Roper excitations  no kinematic reflections no kinematic reflections clean and simple situation clean and simple situation scalar-isoscalar (  ) excitation of Roper possible scalar-isoscalar (  ) excitation of Roper possible p   invariant mass: I=3/2  only   p   invariant mass: I=3/2  only   n   : I=1/2, 3/2  Roper (   very weak) n   : I=1/2, 3/2  Roper (   very weak)

 excitation in pN → NN  pp → pp  893 MeV pn → pp  893 MeV   = 100 MeV

3. pp → np   (WASA)  T p = 1.1 GeV  T p = 1.3 GeV  Roper M p    M n  Data prefer Roper values: M  1350 MeV  140 MeV (nucl-ex/ )

pp → np   (WASA)  T p = 1.1 GeV  T p = 1.3 GeV  Roper M p    M n  Calculation: SAID-values:  : M=1232,  =110 MeV  : M=1232,  =110 MeV Roper: M=1360,  =160 MeV Roper: M=1360,  =160 MeV Data prefer Roper values: M  1350 MeV  140 MeV

3. pp → np   (WASA)  T p = 1.3 GeV averaged over averaged over two triggers two triggers (cc and fc) (cc and fc) only trigger cc only trigger cc  Roper M p    M n  Data prefer Roper values: M  1350 MeV  140 MeV (nucl-ex/ )

Dalitz plots MC pp → np  1.3 GeV   and     and   only Roper   ,    Roper M p    M n   

Dalitz plots MC pp → np  1.3 GeV only   only   only Roper    and Roper MpMp MnMn

Dalitz Plots pp → np  1.3 GeV ( not corrected) data data MC („through detector“) M p    M n   

Dalitz Plots pp → np  1.3 GeV ( not corrected) data data MC MpMp MnMn

Decay of Roper decay channels: BR(1440) BR(1371) decay channels: BR(1440) BR(1371) PDG 2006 Bonn 2007 (Sarantsev et al.) PDG 2006 Bonn 2007 (Sarantsev et al.) N * → N  0.55 – (2) N * → N  0.55 – (2) N * → N  0.30 – (5) N * → N  0.30 – (5) →  → N  0.20 – (2) →  → N  0.20 – (2) → N  → N(  ) I=L=1 < 0.08 → N  → N(  ) I=L=1 < 0.08  → N  → N(  ) I=L= – (3)  → N  → N(  ) I=L= – (3) N* →  N * → N  : 2 – (2) N* →  N * → N  : 2 – (2) PRC 67 ( 2003 ) (Pätzold et al) N * → N  : look in pp → pp * → pp  1.0 (1) N * → N  : look in pp → pp * → pp  1.0 (1)

Status quo ante: experimental and theoretical situation  production chiral dynamics Roper 

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

 Production: pp → pp     Energy dependence of total cross section Energy dependence of total cross section N * →N  N * →   WASA PROMICE/WASA bubble chamber data Roper Valencia No good description of differential data !!!

 Production: pp → pp     Energy dependence of total cross section Energy dependence of total cross section N * →N  N * →   WASA PROMICE/WASA bubble chamber data Roper … gives better description of differential data

Angular distributions cos   cm cos  p cm cos   cm cos  p cm 775 MeV 900 MeV 1000 MeV 1100 MeV 1200 MeV 1300 MeV

Invariant Mass distributions M     M p   M     M p   775 MeV 900 MeV 1000 MeV 1100 MeV 1200 MeV 1300 MeV

threshold region:     Roper excitation and decay jkkjm mmm mmlllll llllllllll ““““ N*N* N*N* ( conventional analysis ) Branching pole: MeV N * →  / N * → N  = 3.4 (3) 0.6 (1) PDG 4 (2)   < < PRC 67 ( 2003 ) ) )

CELSIUS-WASA pp → pp     I   = 0,1 pp → pp     I  = 0 T p = 775 MeV T p = 900 MeV ∙∙∙∙∙∙∙∙ BR(  ) = 1 : 2 I  = ―—— BR(  ) = 1 : 8 I  = 0  N * → N   N * → N  dominantly N → N  ! ( nucl-ex/ ) ( nucl-ex/ ) Roper Pole

Conclusions (1) Roper Resonance historically: Roper Resonance historically: Originally found in  N phase shifts of P 11 partial wave Originally found in  N phase shifts of P 11 partial wave Interpretation as a Breit-Wigner resonance in  N Interpretation as a Breit-Wigner resonance in  N  M  1440 MeV,   400 MeV  M  1440 MeV,   400 MeV Not seen in total cross sections of  N and  N systems Not seen in total cross sections of  N and  N systems A more narrow structure ( M  1400 MeV,   200 MeV) seen in inclusive  p and pp reactions at small Q 2 A more narrow structure ( M  1400 MeV,   200 MeV) seen in inclusive  p and pp reactions at small Q 2 kinematic reflection or characteristics of breathing mode ??? kinematic reflection or characteristics of breathing mode ???

Conclusions (2) Roper resonance now: Roper resonance now: M  (MeV) M  (MeV) SAID  N partial wave analysis: SAID  N partial wave analysis: Bonn (Sarantsev et al)  N +  N 1371(2) 184(20) Bonn (Sarantsev et al)  N +  N 1371(2) 184(20) Explicitly seen in: Explicitly seen in:  p →  X (?)  p →  X (?) J/  → n p   J/  → n p   p p → p n   p p → p n   Roper decay N * → N  Roper decay N * → N  pp → NN   dominantly N * → N  pp → NN   dominantly N * → N 

Conclusions (3) Scalar-isoscalar probes (  exchange) see „narrow“ monopole excitation at very low excitation energy : Scalar-isoscalar probes (  exchange) see „narrow“ monopole excitation at very low excitation energy : breathing   400 MeV ! breathing   400 MeV ! i.e. only 100 MeV above , the lowest excited state i.e. only 100 MeV above , the lowest excited state

 production in NN collisions  threshold region: Roper  T p > 1 GeV: 

 region pp → pp      T p = 1360 MeV     prediction

Inclusive Differential Measurements    p: 8 and 16 GeV/c    p: 8 and 16 GeV/c Enhancement near Enhancement near MM  1400 MeV MM  1400 MeV  200 MeV  200 MeV however, only at small momentum transfer! however, only at small momentum transfer! p + p: 6 – 30 GeV/c p + p: 6 – 30 GeV/c Similar situation! Similar situation! Is this connected with the Roper? Is this connected with the Roper? Anderson et. al, PRL 25, 699 (1970) F 15 D 13 smallmomentumtransfer largermomentumtransfer

1. answer: No Observed structure in inclusive measurements due to kinematic reflection of   p scattering at one vertex Observed structure in inclusive measurements due to kinematic reflection of   p scattering at one vertex Deck model PRL 13, 169 (1964) Deck model PRL 13, 169 (1964)  pp → ppX: pp → ppX: not pp → p N * not pp → p N * but pp →   (p   ) rescatt but pp →   (p   ) rescatt → p   p   → p   p   pp → pp    6.6 GeV/c: pp → pp    6.6 GeV/c: p   production associated with p   production associated with peripheral   production peripheral   production Gellert et al., PRL 16, 884 (1966) pp →   p     N*N* MpMp

2. answer: Yes Reanalysis of inclusive data on pp → ppX Reanalysis of inclusive data on pp → ppX …. …. Morsch and Zupranski, PRC 71, (2005)

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

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

pp → np  45 GeV (CERN) Structure at 1.35 GeV in M n   at low t Structure at 1.35 GeV in M n   at low t interpreted as „well-known low-mass enhancement“ (kinematic reflection ?) interpreted as „well-known low-mass enhancement“ (kinematic reflection ?) MnMn Kerret et al., PLB 63, 477 (1976)