Inmedium excitation of nucleon resonances using heavyion charge

In-medium excitation of nucleon resonances using heavy-ion charge exchange reactions J. Benlliure University of Santiago de Compostela, Spain International Workshop XLIII on Gross Properties of Nuclei and Nuclear Excitations Hirschegg, Kleinwalsertal, Austria, January 11 - 17, 2015

Motivation Charge-exchange reactions are unique probes to investigate spin-isopin prope - Contrary to b-decay, these reactions may excite spin-isospin modes over a bro - Spin-isospin excitations manifest in two different energy domains at low energies: particle-hole excitations (Gamow-Teller, spin-dipole, spin- quadrupole or quasi-elastic). - Gamow-Teller: BGT transition strengths 27 A(20 Ne, 20 Na) @ 900 Me. V/u- spin-dipole: radial distributions of protons and neutrons A. Krasznahorkay et al. NPA 731 (200 at high energies: excitation of nucleon resonances (e. g. D resonance) - In-medium properties of baryon resonances C. Bachelier et al. PLB 172 (1986) 23 Energy(Me. V) José Benlliure Hirschegg Int. Workshop, Janua

Motivation Subnucleonic degrees of freedom play a role in ground-state and structural pro Gamow-Teller strength quenching. role of D-h excitations Three-body nuclear forces. role of D(1232) and N*(1440) The relative probability for inelastic (n, p) and (p, n ) reactions can be used to p of protons and neutrons at the nuclear periphery. Because of the strong absorption isobar chargeexchange reactions are peripheral Renewed interest in the in-medium properties of the processes. D-resonance Role of nucleon excitations in compact and José Benlliuremassive neutron stars. Hirschegg Int. Workshop, Janua

Outline Isobar charge-exchange reactions and the ejectile missing-energy spectra. Previous investigations on nucleon resonances excitations using heavy-ion charge-exchange reactions. Recent measurements at FRS@GSI. experimental requirements improved resolution preliminary results First model calculations. Future perspectives. first exclusive measurements at FRS@GSI nucleon resonances excitation in asymmetric nuclear matter at Super. FRS@FAIR José Benlliure Hirschegg Int. Workshop, Janua

Isobar charge-exchange reactions investigated in inverse kinematics allow for t of in-medium excitation of the Delta resonance for both (p, n) and (n, p) channel C. Bachelier et al. PLB 172 (1986) 23 20 N a 20 N e 20 F n n p, n p p N p n p+ p D N n p+, N p Do p- po n p p In the inelastic charge-exchange process the pion must in order to preserve the isobar character José scape Benlliure The momentum recoil induced by the p emission proves the excitation of the re Hirschegg Int. Workshop, Janua

Isobar charge-exchange reactions at Saturne Systematic investigations with stable light and medium-mass projectiles were performed measuring the missing-energy spectra of the ejectiles with the SPES 4 spectrometer. A downward shift of about 70 Me. V in the mass of the Delta resonance was observed when excited with composite targets. Many theoretical works tried to explain the origin of the shift as due to in-medium effects. F. Osterfeld. Rev. Mod. Phys. 64 (1992) 491 José Benlliure D. Contardo et al. . PLB 168 (1986) 331 Other experiments at: Gatchina: V. N. Baturin et al. Sov. J. NP 31 (1980) 207 Lampf: D. A Lind, Can. J. Phys. 65 (1987) 637 Dubna: V. G. Ableev et al. , Jetp. 40 Hirschegg Int. Lett. Workshop, Janua

Isobar charge-exchange reactions at Saturne The observable used to identify the excitation of the Delta resonance, missing-energy spectra of the ejectiles, is sensitive to excitation in the projectile and the target nucleus. Projectile excitations Target excitations 3 He Detailed calculations showed that projectile and target excitations lead to missing-energy spectra with different shapes that contribute to the observed E. Osetshift. et al. PLB 224 (1989) 249 mass José Benlliure d t. DN THe = 2 Ge. V Hirschegg Int. Workshop, Janua

Direct observation of the Roper resonance at S Direct observation of the Roper resonance in the missing energy spectra in (a, a’) reactions on a proton target. José Benlliure H. P. Morsch et al. , PRL 69 (1992) 133 Hirschegg Int. Workshop, Janua

Direct observation of the Roper resonance at S Direct observation of the Roper resonance in the missing energy spectra in (a, a’) reactions on a proton target. José Benlliure Hirschegg Int. Workshop, Janua

Direct observation of the Roper resonance at S The unknown nature of the Roper resonance. In a quark model with and oscillator potential the Roper would be the second excited state N*(1440) as a collective excitation (breathing mode). - Bag model: monopole vibration of the bag surface (G. Brown et al. NPA 397 (1983) 447) - Quarks in a deformed oscillator potential: rotational state N*(1440) with an exotic nature. al. ) - Hybrid state qqq. G (H. Toki et (S. Capstick et al. PRD 60 (1999) 111501) - Dual nature qqq and qqqqq (B. Julia-Diaz and D. Riska NPA 780 (2006) 175) …… José Benlliure Taken from L. Alavarez-Ruso ar. Xiv: 1011 Hirschegg Int. Workshop, Janua

Isobar charge-exchange reactions at FRS@GSI First observation of the D-resonance in (n, p) isobaric charge-exchange reactions at the FRS 208 Pb(1000 Me. V/u)+p, d ---- p(208 Pb, 208 Bi) ---d(208 Pb, 208 Bi) A. Kelic et al. , Phys. Rev. C 70 (2004) 64608 José Benlliure Hirschegg Int. Workshop, Janua

A new exploratory experiment at FRS@GSI To investigate the feasibility of accurate measurements of nucleon resonances excited in isobar charge-exchange reactions induced by stable and unstable projectiles using the inverse kinematic technique. Te Te 120 121 122 123 124 125 126 Sb Sb Sb 123 123 Sn Sn Sn Sn Sn 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 In 115 124 Sn+CH 124 Sn+Be Me. V 2, C 124 Sb, 124 In @ 1000 A Me. V 120 Sn+CH 2, C 120 Sb, 120 In @ 1000 A 112 Sn+CH 2, C, Cu, Pb 112 Sb, 112 In @ 400, 700, 1000 A Me. V 112 Sn+Be José Benlliure 110 Sn+CH 2, C 110 Sb, 110 In @ 1000 A Hirschegg Int. Workshop, Janua

Experimental requirements 132 S Observables: cross sections for both charge exchange reactions and channels b 132 S n 132 In missing-energy spectra mean energy and width of the D-resonance Requirements for the setup: isotopic identification of reaction ejectiles separation of elastic and resonant chargeexchange channels magnetic analysis of the reaction ejectiles José Benlliure Hirschegg Int. Workshop, Janua

Experimental setup D-resonance and quasi-elastic charge-exchange reactions identified at the FRS: (standar detection setup) prima ry target DZ/Z ~ 7 10 -3 DA/A ~ 2. 4 10 -3 DE ~ 30 Me. V (124 Sn, 112 Sn @ 1000 Me. V/u) secondar y target - Reactions with stable beams induced at the primary target - Unstable beams produced at the primary target and charge-exchange reac in the secondary target José Benlliure Hirschegg Int. Workshop, Janua

Recent measurements with the FRS Isotopic identification of isobaric charge-exchange residues 12 C(112 Sn, 112 Sb)X 12 C(112 Sn, 112 In)X 112 Sn José Benlliure 49+ Hirschegg Int. Workshop, Janua

Recent measurements with the FRS Missing-energy spectra in isobar charge-changing reactions indu (p, n) José Benlliure (n, p) Hirschegg Int. Workshop, Janua

Recent measurements with the FRS Comparison with the Saturne data (p, n) (n, p) C. Bachelier et al. PLB 172 (1986) 23 José Benlliure Hirschegg Int. Workshop, Janua

Recent measurements with the FRS Comparison with the Saturne data (n, p) (124 Sn, 124 Sb) José Benlliure Hirschegg Int. Workshop, Janua

Recent measurements with the FRS Unfolding the missing-energy spectrum with the experimental re Y: measured spectrum H: experimental response function X: observable The primary beam centred through the FRS constitutes our response function H José Benlliure Hirschegg Int. Workshop, Janua

Recent measurements with the FRS Unfolding the missing-energy spectrum with the experimental re The most reliable unfolding techniques are based on iterative procedures (Richardson-Lucy) A stopping condition is needed to determine the optimum number of iterations J. Vargas, J. B. and M. Caamaño NIMA 707 (2013) 16 José Benlliure Hirschegg Int. Workshop, Janua

Recent measurements with the FRS Unfolding the missing-energy with the experimental response fu 63 Cu(112 Sn, 112 Sb)X Final resolution after deconvolution DE ~ 15 Me. V (124 Sn, 112 Sn @ 1000 A M José Benlliure Hirschegg Int. Workshop, Janua

Recent measurements with the FRS Excitation of nucleon resonances p(a, a’)X @ 4. 2 Ge. V 63 Cu(112 Sn, 112 Sb)X D(1230) N*(1440) ? ? H. P. Morsch et al. , PRL 69, 1336 (1 The unfolded data show clear structures in the inelastic component The second substructure is tentatively identified as the Roper resonance José Benlliure Hirschegg Int. Workshop, Janua

Recent measurements with the FRS Unfolding the missing-energy with the experimental response fu José Benlliure Hirschegg Int. Workshop, Janua

Recent measurements with the FRS Isobar charge-exchange reactions at relativistic energies 12 C(112 Sn, 112 Sb)X 1000 A Me. V 700 A Me. V 400 A Me. V p(112 Sn, 112 Sb)X 12 C(112 Sn, 112 Sb)X The excitation probability of the resonances scales with energy as expect A downward shift in the energy of the resonances is also observed with c José Benlliure Hirschegg Int. Workshop, Janua

Recent measurements with the FRS Missing-energy spectra with secondary beams 110 Sn 112 Sn 110 Sn 12 C(110 Sn, 110 Sb)X 110 Sb Main difficulties: - Low statistics - Thick S 2 target (1 g/cm 2 C) - Important background at S 2 José Benlliure Hirschegg Int. Workshop, Janua

Recent measurements with the FRS: conclusion The feasibility of experiments aiming to investigate the in-medium excitation of nucleon resonances using isobar charge-exchange reactions has been proven. The measured missing-energy spectra show a clear separation between the quasi-elastic and resonant charge-exchange channels. The evolution of the missing-energy spectra with the target is in qualitative agreement with previous measurements at Saturne. The resolution has been improved with respect to previous experiments by using thin targets and unfolding the measured spectra from the response function of the spectrometer. The improved resolution allows us to observe substructures in the inelastic charge-exchange peak. The largest component in the inelastic peak is associated to the excitation of the D resonance while the second substructure is tentatively associated to the Roper resonance. Heavier resonances may also be present in the spectra. Measurements from secondary beams suffered from low statistics and the straggling induced by the use of thick targets José Benlliure Hirschegg Int. Workshop, Janua

Model calculations Differential cross sections: Isaac Vidaña, U. Coimb Elemental processes: R=D, N* José Benlliure Hirschegg Int. Workshop, Janua

Model calculations Elemental processes: Isaac Vidaña, U. Coimb Quasi-elastic channel Scattering amplitudes are calculated in the Born approximation one pion exchange José Benlliure short-range correlations Hirschegg Int. Workshop, Janua

Model calculations Elemental processes: Isaac Vidaña, U. Coimb R=D, N* Inelastic channels Invariant mass of the resonances for target excitations: Invariant mass of the resonances for projectile excitations: José Benlliure Hirschegg Int. Workshop, Janua

Model calculations Projectile and target resonance excitations: Isaac Vidaña, U. Coimb projectile excitations target excitations José Benlliure Hirschegg Int. Workshop, Janua

Model calculations Benchmarking with elemental processes (pp pnp+): Isaac Vidaña, U. Coimb José Benlliure data: G. Glass et al. , PRD 15 (1977) 37 Hirschegg Int. Workshop, Janua

Model calculations Effective number of elementary processes in heavy-ion Isaaccollisions: Vidaña, U. Coimb Overlapping nucleon density: Transmission function: Pion survival probability: José Benlliure Hirschegg Int. Workshop, Janua

Model calculations Effective number of elementary processes in heavy-ion Isaaccollisions: Vidaña, U. Coimb José Benlliure Hirschegg Int. Workshop, Janua

Model calculations Isaac Vidaña, U. Coimbra Preliminary calculations Preliminary model calculations provide a good qualitative description of the measured distributions The calculations clearly show the contribution of different resonances and their excitation in the projectile but also in the target nucleus José Benlliure Hirschegg Int. Workshop, Janua

Model calculations Isaac Vidaña, U. Coimbra Preliminary calculations 12 C(112 Sn, 112 Sb)X 1000 A Me. V 700 A Me. V 400 A Me. V Reactions induced on protons are the more selective to the excitation of Delta and the Roper. energies can also be used to select the Delta the Measurements at different José Benlliure and Roper in carbon Hirschegg Int. Workshop, Janua

Model calculations: conclusions New model calculations of isobaric charge-exchange reactions are under development. This model describes both the quasi-elastic and resonant channels including for the moment the excitation of the Delta and Roper resonances in target and projectile nuclei. The model describe reasonably well elemental charge-exchange reactions pp pnp+. The description of nucleus-nucleus charge-exchange reactions requires a realistic description of the proton and neutron densities (transmission function) and of the absorption probability of pions. The combination of both selects a narrow window in impact parameter at the nuclear periphery. The present version of the model provides a qualitative description of the data measured at GSI. These calculations show a complicated mixing of excitations in the target and projectile nuclei. These results suggest that reactions induced on protons and carbon could be used to extract the properties of the resonances excited in these reactions. José Benlliure Hirschegg Int. Workshop, Janua

Next steps A new experimental proposal at FRS@GSI - improved momentum resolution with the FRS: stripped target, better tracking detectors - exclusive measurements detecting projectile pions in coincidence - the required setup strongly overlap with the one required for hypernuclei studies From T. Saito José Benlliure Hirschegg Int. Workshop, Janua

Next steps A new experimental proposal at FRS@GSI - improved momentum resolution with the FRS: strip target, better tracking detectors - exclusive measurements detecting pions in coincidence An experimental program at Super. FRS@FAIR - larger acceptance and resolution at the Super. FRS - exclusive measurements detecting projectile and target pions in coincidence - measurements with intense secondary beams: excitation of nucleon resonances in asymmetric nuclear matter José Benlliure Hirschegg Int. Workshop, Janua

Conclusions A high-resolving power magnetic spectrometer has been proven to be an ex nucleonic excitations in heavy-ion isobaric charge-exchange reactions: - several baryon resonances were identified in the projectile remnant missin - cross sections for elastic and inelastic, (p, n) and (n, p) reactions were also m - in-medium properties of these baryons and the relative abundance of pro the nuclear periphery will be investigated using reliable model calculation The Super-FRS at FAIR will offer unique opportunities for these investigation - extremely asymmetric nuclear matter - improved separation capabilities (pre-separator) and resolution - exclusive measurements detecting pions in coincidence José Benlliure

Collaborators U. Santiago de Compostela: J. Vargas, Y. Ayyad, S. Beceiro, D. Cortina, P. Díaz, M. Mostazo, C. Paradela GSI: T. Aumann, J. Atkinson, K. Boretzky, A. Estrade, H. Geissel, A. Kelic, Y. Litvinov, S. Pietri, A. Prochazka, M. Takechi, H. Weick, J. Winfield CEA/DAM: A. Chatillon, J. Taieb U. Coimbra: I. Vidaña U. Giessen: H. Lenske José Benlliure