Spectroscopy of η nucleus bound states at GSI and FAIR very preliminary results and future prospects

Transcription

1 Spectroscopy of η nucleus bound states at GSI and FAIR very preliminary results and future prospects Hiroyuki Fujioka (Kyoto Univ.) on behalf of the η-prime collaboration

2 η-prime Collaboration 2 Y. Ayyad, J. Benlliure, K.-T. Brinkmann, S. Friedrich, H. Fujioka(**), H. Geissel, J. Gellanki, C. Guo, E. Gutz, E. Haettner, M.N. Harakeh, R.S. Hayano, Y. Higashi, S. Hirenzaki, C. Hornung, Y. Igarashi, N. Ikeno, K. Itahashi(*), M. Iwasaki, D. Jido, N. Kalantar-Nayestanaki, R. Kanungo, R. Knoebel, N. Kurz, V. Metag, I. Mukha, T. Nagae, H. Nagahiro, M. Nanova, T. Nishi, H.J. Ong, S. Pietri, A. Prochazka, C. Rappold, P. Reiter, J.L.R. Sanchez, C. Scheidenberger, H. Simon, B. Sita, P. Strmen, B. Sun, K. Suzuki, I. Szarka, M. Takechi, Y.K. Tanaka, I. Tanihata, S. Terashima, Y.N. Watanabe, H. Weick, E. Widmann, J.S. Winfield, X. Xu, H. Yamakami, J. Zhao (*) spokesperson (**) co-spokesperson Osaka University, Universidade de Santiago de Compostela, Universitaet Giessen, Kyoto University, GSI, University of Groningen, Beihang University, The University of Tokyo, Nara Women's University, KEK, RIKEN, Tokyo Metropolitan University, Saint Mary s University, Technische Universitaet Darmstadt, Comenius University Bratislava, Stefan Meyer Institut, Niigata University

3 3 introduction

4 pseudoscalar mesons in broken chiral symmetry 4 0 UA(1) anomaly,k, 8, 0 K,K, 8 massless m q = m s =0 m q = m s =0 m q = m s =0 qq =0 qq =0 qq =0 ChS manifest ChS broken dynamically ChS broken dynamically and explicitly Nagahiro et al., PRC 87, (2013)

5 η meson in medium 5 At finite density/temperature, chiral symmetry will be partially restored cf. deeply-bound pionic atom (talk by Itahashi) large mass reduction, as a consequence of suppression of the anomaly effect? optical potential: V(r)=(V 0 +iw 0 )ρ(r)/ρ 0 V 0 = (mass reduction), 2 W 0 = (absorption width)

6 η optical potential: state of the art COSY-11 0 V 0 [MeV] (=m η (ρ 0 )-m η ) chiral unitary CBELSA/TAPS COSY exp. (η A int.) exp. (η N int.) theory COSY NJL linear σ QMC W 0 [MeV] (=-Γ/2)

7 Nambu Jona-Lasinio model chiral 400 unitary -50 Nagahiro, presentation at Hadron in Nucleus Meson mass [MeV] cf.) NJL model with KMT COSY-11 U A (1) breaking (KMT term [1,2] ) CBELSA/TAPS [1] Kobayashi-Maskawa PTP44(70)1422 [2] G. t Hooft, PRD14(76) V (=m COSY COSY NJL linear QMC W Nagahiro et al., PRC 76, (2006) (=-Γ

8 chiral unitary model talk COSY-11 by Nagahiro 0 (Wed) V Oset and Ramos, PLB 704, 334 (2011) (=m Nagahiro et al., PLB 709, 87 (2012) COSY-11 B B CBELSA/TAPS -10 chiral unitary and with various values Nagahiro, presentation at Hadron in Nucleus COSY in unit of MeV fm NJL linear QMC W (=-Γ

9 Meson Mass [MeV] linear sigma model COSY-11 0 V (=m Sakai, presentation at Hadron in Nucleus m η chiral 500 m η 400 unitary m π Nuclear Density [fm -3 ] η mass in chiral limit The contribution from the U A (1) anomaly CBELSA/TAPS COSY The contribution from the chiral symmetry breaking + + Sakai and Jido, PRC 88, COSY (2013) -20 NJL linear σ QMC W talk by Sakai (Wed), Jido (=-Γ

10 quark-meson coupling model Bass and Thomas, Acta Phys. Pol. B 41 (2010) 2239; ibid. 45 (2014) 627 COSY-11 0 V (=m COSY-11 m (MeV) m (MeV) Rea (fm) η η (-10 o ) η (-20 o ) chiral η 0 η (-10 o ) 958 unitary η (-20 o ) CBELSA/TAPS -10 COSY NJL linear QMC W talk by Bass (Fri) (=-Γ

11 transparency ratio measurement transparency ratio -50 COSY-11 0 V (=m T A = ( A X) A ( N X) COSY chiral unitary NJL linear QMC Nanova et al., PLB 710, 600 (2012) CBELSA/TAPS COSY-11 Γ=15 25MeV -20 at ρ=ρ 0 Fig. 6. (Left) Transparency ratio for different mesons η (squares), η (triangles) a cut on the kinetic energy for the respective mesons is shown with full symbols. Th data. Only statical errors are shown. The impact of photon shadowing on the dete not been corrected for in the published data for the other mesons. (Right) α param η and ω ([34], thiswork).thisfigureisanupdatedversionofafiguretakenfrom for <p η >~1.05GeV/c Because of the near constancy of Γ one would expect (see Eq. (9)) a rise ofσ inel towards lower η momenta, as indicated by the data in the lower panel of Fig. 5 (right). An increase o W σ inel for low η momenta has in fact been predicted in [7], rathe talk by Metag independent of the η scattering length. The theoretical predic tions follow qualitatively (=-Γ the trend of the data and may even be compatible with the experimental results, allowing for the large systematic uncertainties in the determination of σ inel due to the unknown strength of two-body absorption processes, discussed

12 excitation function and momentum distribution 12 Fig. 5. (Colour online.) Differential cross sections for η photoproduct (middle), and above the threshold (right). The calculations are for σ η N density, respectively. All calculated cross sections have been reduced by COSY-11 0 V (=m COSY V 0 = (40±6) MeV chiral unitary NJL linear QMC Nanova et al., PLB 727, 417 (2013) CBELSA/TAPS Fig. 6. (Colour online.) Left: Momentum distribution for η photoproduc V and for potential depths V = 0, 25, 50, 75, 100 and 150 MeV 0.75 (see text). Middle: The 0 = (32±11) MeV experimental data and the predicted curve and presented on a linear scale. The colour code is identical to the o scenarios. COSY Within the model used, the present results on the re the potential are consistent with an attractive η -nucle tial with a depth of (37 ± 10(stat) ± 10(syst)) MeV. T implies the first (indirect) observation of a mass redu pseudoscalar meson in a strongly interacting environm V 0 = (37±10 stat ±10 syst ) MeV normal conditions (ρ = ρ 0, T = 0). The attractive η -nu tential might even be strong enough to allow the for bound η -nucleus states. The search for such states is e W talk by Metag by the relatively small in-medium width of the η [11 (=-Γ ments are proposed to search for η -bound states via mis spectroscopy [35] at the Fragment Separator (FRS) at G asemi-exclusivemeasurementatthebgo-opendipol(

13 elementary process : pp ppη COSY-11 0 V (=m COSY CBELSA/TAPS Moskal et al., PLB 474, chiral 416 (2000) unitary Re a η N < 0.8fm COSY NJL talk by Moskal linear a QMC η N ~ 0.1fm W Moskal et al., PLB 482, 356 (2000) (=-Γ

14 elementary process : pp ppη COSY-11 0 V Czerwiński et al., PRL 113, (2014) (=m Re a η N = 0±0.43 fm COSY-11 Im a η N = fm 0.16 chiral unitary CBELSA/TAPS COSY NJL talk by Moskal linear QMC W (=-Γ

15 η optical potential: state of the art COSY-11 0 V 0 [MeV] (=m η (ρ 0 )-m η ) chiral unitary CBELSA/TAPS V0=W0 COSY exp. (η A int.) exp. (η N int.) theory COSY NJL linear σ QMC W 0 [MeV] (=-Γ/2)

16 η optical potential: state of the art COSY-11 0 V 0 [MeV] Chiral Unitary Model (=m η (ρ 0 )-m η ) and CBELSA/TAPS favor Re V >! Im V η bound state? chiral unitary CBELSA/TAPS V0=W0 COSY exp. (η A int.) exp. (η N int.) theory COSY NJL linear σ QMC W 0 [MeV] (=-Γ/2)

17 16 spectroscopy of η mesic nuclei at GSI

18 12 C(p,d) reaction C 11 C η intense proton beam available relatively large momentum transfer population of large l η states near threshold different rigidities between protons and deuterons (from an experimental point of view)

19 theoretical calculation 18 elementary cross section : dσ/dω(pn dη )=30μb/sr relatively large momentum transfer population of large l η states near threshold Nagahiro et al., PRC 87, (2013)

20 GSI accelerator facility 19

21 GSI S437 experiment (*) 20 Letter of Intent for GSI-SIS Spectroscopy of η mesic nuclei with (p, d) reaction Interplay of U A (1) anomaly and chiral restoration in η mass (2011) K. Itahashi, HF et al., PTP 128, 601 (2012) intense proton beam from SIS-18 (~10 10 /spill) 4g/cm 2 -thick 12 C target high resolution measurement of deuteron by FRS overall missing-mass resolution : σ < 2MeV/c 2 (*) under the framework of the Super-FRS collaboration

22 experimental setup GeV proton S0-S2: achromatic S0-S4: dispersive (~38mm/%) 12 C target S1 aerogel Cerenkov counter GeV/c deuteron S2 S3 MWDC plastic scintillator S4 aerogel Cerenkov counter

23 experimental setup GeV proton S0-S2: achromatic S0-S4: dispersive (~38mm/%) 12 C target S1 aerogel Cerenkov counter GeV/c deuteron S2 S3 (proton) MWDC plastic scintillator S4 aerogel Cerenkov counter

24 experimental setup GeV proton S0-S2: achromatic S0-S4: dispersive (~38mm/%) 12 C target S1 aerogel Cerenkov counter GeV/c deuteron S2 S3 (proton) p/d separation (planned) on-line: aerogel Cerenkov counter off-line: TOF between S2 and S4 (diff. by ~20ns) MWDC S4 plastic scintillator aerogel Cerenkov counter

25 expected spectrum w/ 4.5-day DAQ (V, W )= (200, 5) MeV 0 0 (V, W )= (150, 5) MeV 0 0 (V, W )= (100, 5) MeV 0 0 counts/2mev (V, W )= (200, 10) MeV 0 0 (V, W )= (150, 10) MeV 0 0 (V, W )= (100, 10) MeV 0 0 counts/2mev (V, W )= (200, 20) MeV 0 0 (V, W )= (150, 20) MeV 0 0 (V, W )= (100, 20) MeV 0 0 counts/2mev Excitation Energy [MeV] Excitation Energy [MeV] Excitation Energy [MeV]

26 structure-finding probability in GSI 23 W [MeV] V [MeV] (%) 95% C.L., 4.5-day DAQ

27 structure-finding probability in GSI 23 W [MeV] V [MeV] (%) high sensitivity in case of large mass reduction and small decay width 95% C.L., 4.5-day DAQ

28 S437 Exp. : 1st-8th August Production Run (~5 days) : T p =2.5 GeV intensity (3 4) /spill target thickness 4g/cm 2 FRS scaling from -2% to 2% FRS scaling -2% (5 10) 10 6 deuterons in each scaling mode Calibration Run : T p =1.6GeV Reference Run : T p =2.5 GeV η bound unbound Eex - E0 [MeV] background measurement (p+(p/n) d + multi π s) 0% +2%

29 Calibration Run: D(p,d)p FRS scaling -2% 10-1% 0% 1% preliminary 2% information on optics missing-mass resolution stability of the system X [mrad] X [mm] at S4-MWDC

30 particle identification 26 TOF S2-S4 S2 36m S4 Counts proton preliminary deuteron unbiased p/d ratio ~ proton: 99.5% rejection TOF trigger p/d ratio ~ 1 note: Cerenkov counters were not used for triggering purpose. Counts TOF (S2-S4) + offset [/25ps] TOF S2-S4 deuteron preliminary TOF (S2-S4) + offset [/25ps]

31 particle identification 27 TOF S2-S4 S2 36m S4 Counts proton preliminary deuteron 1 deuteron TOF (S2-S4) + offset [/25ps] TOF S2-S4 preliminary 2000 Counts 1500 deuteron time TOF (S2-S4) + offset [/25ps]

32 particle identification 28 TOF S2-S4 S2 36m S4 Counts proton unbiased deuteron ~20ns TOF (S2-S4) + offset [/25ps] TOF S2-S4 proton proton deuteron TOF trigger deuteron Counts 1500 time TOF (S2-S4) + offset [/25ps]

33 particle identification 28 TOF S2-S4 ~20ns S2 36m coincidence! S4 Counts proton unbiased deuteron TOF (S2-S4) + offset [/25ps] TOF S2-S4 proton proton deuteron TOF trigger deuteron Counts 1500 time TOF (S2-S4) + offset [/25ps]

34 particle identification TOF(S2-S4) vs TOF(SC41-SC42) ~20ns S2 36m proton S4 4m TOF (SC41-SC42) + offset [/25ps] ~2.5ns proton deuteron deuteron TOF (S2-S4) + offset [/25ps] time proton further analysis Cerenkov signal waveform analysis of S2, S4 scintillators ~2.5ns (p,d) event selection

35 30

36 FAIR under construction 31

37 FAIR under construction 31

38 32 inclusive measurement at FAIR

39 from FRS to Super-FRS 33 FRS proton beam target o 30 dipole D1 quadrupole S1 D2 S2 D3 S3 S4 D4 MWDC SC2 AC SC1 target Super-FRS more intense beam ( /spill?) and larger aperture of Super-FRS rejection of BG from beam dump rate capability of detectors faster DAQ

40 all-in-one readout board 34 one order of magnitude higher trigger rate R&D of 64ch readout board for MWDC ASD + FlashADC + TDC originally developed for Belle-II CDC sub-trigger module for trigger distribution H. Yamakami (Kyoto Univ.) Taniguchi et al., NIM A732, 540 (2013)

41 35 semi-exclusive measurement at FAIR

42 Why semi-exclusive measurement? (V, W )= (200, 5) MeV 0 0 (V, W )= (150, 5) MeV 0 0 (V, W )= (100, 5) MeV 0 0 counts/2mev inclusive measurement S/N ~ O(1/100) at most counts/2mev (V, W )= (200, 10) MeV 0 0 (V, W )= (150, 10) MeV 0 0 (V, W )= (100, 10) MeV 0 0 BG: multi-π production counts/2mev (V, W )= (200, 20) MeV 0 0 (V, W )= (150, 20) MeV 0 0 (V, W )= (100, 20) MeV Excitation Energy [MeV] Excitation Energy [MeV] Excitation Energy [MeV] semi-exclusive measurement (w/ improved S/N) more sensitivity in case of shallow potential

43 coincidence of decay particles 37 one-nucleon absorption: η N ηn, (πn) two-nucleon absorption: η NN NN higher energy than in any mesonic processes Nagahiro et al., PRC 87, (2013)

44 high-energy protons from η mesic nuclei 38 p d Detection of high energy protons (T p = MeV) η η p ηp p p d 80 η N πp p π d counts (a.u.) η pn pn N proton kinetic energy [MeV]

45 high-energy protons from BG (multi π) 39 counts (a.u.) η p ηp η N πp proton momentum [GeV/c] η pn pn cos (Lab.) simulation by a microscopic transport model (JAM) proton momentum [GeV/c] Y. Higashi (Nara Women's Univ) work in progress

46 from FRS to Super-FRS 40 FRS proton beam target o 30 dipole D1 quadrupole S1 D2 S2 D3 S3 S4 D4 MWDC SC2 AC SC1 Super-FRS target dispersive focal plane

47 from FRS to Super-FRS target FRS proton beam o 30 dipole S1 D1 quadrupole S3 FRS D2 S4 S2 D3 SC1 D4 MWDC SC2 AC Super-FRS target dispersive focal plane 40

48 from FRS to Super-FRS 40 FRS proton beam target o 30 dipole D1 quadrupole S1 D2 S2 D3 S3 S4 D4 MWDC SC2 AC SC1 Super-FRS target dispersive focal plane

49 range counter for proton detection 41 just conceptual 10 layers of Sci/Brass sampling calorimeter p/π ± separation by use of neural network? (conceptual design) work in progress scintillator proton beam brass

50 conclusion 42

51 conclusion 42 possible existence of η -nucleus bound state, due to partial restoration of chiral symmetry in medium

52 conclusion 42 possible existence of η -nucleus bound state, due to partial restoration of chiral symmetry in medium inclusive measurement of (p,d) reaction at GSI/FAIR

53 conclusion 42 possible existence of η -nucleus bound state, due to partial restoration of chiral symmetry in medium inclusive measurement of (p,d) reaction at GSI/FAIR high statistics and high resolution

54 conclusion 42 possible existence of η -nucleus bound state, due to partial restoration of chiral symmetry in medium inclusive measurement of (p,d) reaction at GSI/FAIR high statistics and high resolution near-threshold structure = signature of attractive int.

55 conclusion 42 possible existence of η -nucleus bound state, due to partial restoration of chiral symmetry in medium inclusive measurement of (p,d) reaction at GSI/FAIR high statistics and high resolution near-threshold structure = signature of attractive int. First experiment S437 carried out in August 2014

56 conclusion 42 possible existence of η -nucleus bound state, due to partial restoration of chiral symmetry in medium inclusive measurement of (p,d) reaction at GSI/FAIR high statistics and high resolution near-threshold structure = signature of attractive int. First experiment S437 carried out in August 2014 verified experimental feasibility

57 conclusion 42 possible existence of η -nucleus bound state, due to partial restoration of chiral symmetry in medium inclusive measurement of (p,d) reaction at GSI/FAIR high statistics and high resolution near-threshold structure = signature of attractive int. First experiment S437 carried out in August 2014 verified experimental feasibility DAQ upgrade in progress for higher statistics at FAIR

58 conclusion 42 possible existence of η -nucleus bound state, due to partial restoration of chiral symmetry in medium inclusive measurement of (p,d) reaction at GSI/FAIR high statistics and high resolution near-threshold structure = signature of attractive int. First experiment S437 carried out in August 2014 verified experimental feasibility DAQ upgrade in progress for higher statistics at FAIR semi-exclusive measurement planned at FAIR

59 conclusion 42 possible existence of η -nucleus bound state, due to partial restoration of chiral symmetry in medium inclusive measurement of (p,d) reaction at GSI/FAIR high statistics and high resolution near-threshold structure = signature of attractive int. First experiment S437 carried out in August 2014 verified experimental feasibility DAQ upgrade in progress for higher statistics at FAIR semi-exclusive measurement planned at FAIR high-energy proton from η pn pn in coincidence