Report from Spectroscopy Experiment. of η Mesic Nuclei at GSI

Transcription

1 Report from Spectroscopy Experiment of η Mesic Nuclei at GSI Yoshiki K. Tanaka (Univ. of Tokyo) for the η-prime collaboration 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. Winfield, X. Xu, H. Yamakami, J. Zhao 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

2 η meson Mass η meson M=958 MeV/c 2 Γ=0.198 MeV Pseudoscalar meson ( J π =0 - ) Decay mode π + π - η(43%), ρ 0 γ(29%), π 0 π 0 η(22%) 2

3 η meson 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 3 ChS broken dynamically and explicitly H.Nagahiro et al.,prc 87 (2013)

4 η meson UA(1) anomaly effect on η mass - KMT interaction in NJL model - related to the strength of chiral condensate <qq> - by Hirenzaki Kobayashi-Maskawa- t Hooft 6-point vertex Kobayashi, Maskawa, PTP44(70)1422 t Hooft, PRD14(76)3432. T. Kunihiro, Phys. Lett. B219(89)363. Klimt, Lutz, Vogl, Weise, NPA516(90)429. 4

5 η meson in medium - Chiral condensate <qq> - reduced by ~30% at ρ0. partial restoration of chiral symmetry - Mass reduction expected e.g., NJL model calculation 150 MeV/c 2 mass reduction -30 % K. Suzuki et al., PRL92(04) ρ0 P.Costa et al.,plb560, (2003) 171. H.Nagahiro et al.,prc 74, (2006)

6 in-medium mass and width η nucleus optical potential : V η = (V0+iW0) ρ(r) V0 = Δm(ρ0), W0 = Γ(ρ0) / 2 - NJL model prediction V0 ~ -150 MeV strong attraction? ρ0 6

7 - NJL model prediction V0 ~ -150 MeV strong attraction? - CBELSA/TAPS in-medium mass and width η nucleus optical potential : V η = (V0+iW0) V0 = -37 ±10(stat) ±10(syst) MeV Γ (ρ0) = MeV, for P η, average =1.05GeV/c ρ(r) M. Nanova et al., Phys. Lett. B 727 (2013) 417 M. Nanova et al., PLB710, 600(2012) - relatively small scattering length of the s-wave η -proton interaction a η p = 0 ± 0.43 fm E. Czerwiński et al., PRL 113, (2014) ρ0 V0 = Δm(ρ0), W0 = Γ(ρ0) / 2 7

8 - NJL model prediction V0 ~ -150 MeV strong attraction? - CBELSA/TAPS in-medium mass and width η nucleus optical potential : V η = (V0+iW0) V0 = -37 ±10(stat) ±10(syst) MeV Γ (ρ0) = MeV, for P η, average =1.05GeV/c ρ(r) M. Nanova et al., Phys. Lett. B 727 (2013) 417 M. Nanova et al., PLB710, 600(2012) - relatively small scattering length of the s-wave η -proton interaction a η p = 0 ± 0.43 fm E. Czerwiński et al., PRL 113, (2014) ρ0 V0 = Δm(ρ0), W0 = Γ(ρ0) / 2 W0 smaller than possible mass reduction V0 possibility to observe η meson-nucleus bound state (η mesic nuclei)

9 Experiment at FRS-GSI 9

10 Missing mass spectroscopy of (p,d) reaction 2.5 GeV proton beam momentum measurement by Fragment Separator missing-mass spectrum Target η mesic nuclei K. Itahashi et al., PTP 128,601(2012) 1st Step : Inclusive measurement of (p,d) reaction at GSI - no assumption on decay process - poor S/N ratio due to BG processes (e.g., multi-pion production) 10

11 Missing mass spectroscopy of (p,d) reaction 2.5 GeV proton beam momentum measurement by Fragment Separator missing-mass spectrum Target η mesic nuclei K. Itahashi et al., PTP 128,601(2012) 1st Step : Inclusive measurement of (p,d) reaction at GSI - no assumption on decay process - poor S/N ratio due to BG processes (e.g., multi-pion production) High-statistics measurement is essential using high-intensity beam + thick target 11

12 Theoretical spectra of 12 C(p,d) 11 C η η nucleus optical potential : - Green s function method - proton energy 2.5 GeV, mom. transfer ~ 400 MeV/c V η = (V0+iW0) ρ(r) ρ0 V0 = Δm(ρ0), W0 = Γ(ρ0) / 2 12 H.Nagahiro et al.,prc 87 (2013)

13 Theoretical spectra of 12 C(p,d) 11 C η η nucleus optical potential : - Green s function method - proton energy 2.5 GeV, mom. transfer ~ 400 MeV/c V η = (V0+iW0) ρ(r) ρ0 V0 = Δm(ρ0), W0 = Γ(ρ0) / 2 13 H.Nagahiro et al.,prc 87 (2013)

14 Simulation of inclusive measurement Simulated spectra of inclusive measurement assuming 4.5 day DAQ K. Itahashi et al., PTP 128,601(2012) V0, W0 : real, imaginary part of optical potential ρ(r) V η = (V0+iW0) ρ0 (V0 = Δm(ρ0), W0 = Γ(ρ0) / 2) S/N ratio ~ O(1/100) at most counts/2mev counts/2mev counts/2mev counts/2mev counts/2mev counts/2mev (V, W )= (200, 5) MeV 0 0 (V, W )= (200, 10) MeV 0 0 (V, W )= (200, 20) MeV (V, W )= (150, 5) MeV 0 0 ηʼ production (V, W )= (150, 10) MeV 0 0 (V, W )= (150, 20) MeV 0 0 background (e.g.,p+n d+πʼ s) (V, W )= (100, 5) MeV 0 0 (V, W )= (100, 10) MeV 0 0 Simulation (V, W )= (100, 20) MeV Excitation Energy [MeV] Excitation Energy [MeV] Excitation Energy [MeV] Excitation Energy [MeV] Excitation Energy [MeV] Excitation Energy [MeV]

15 Structure-finding probability 15

16 Structure-finding probability 16

17 First experiment at GSI (2014 Aug.) in a framework of the Super-FRS collaboration for FAIR

18 GSI facilities Ion sources 12 C target 2.5 GeV proton momentum analysis 18 UNILAC Ion source

19 Experimental setup at FRS p (Tp = 2.5 GeV, Ip ~ /spill) 12 C target 2 (4 g/cm ) signal d (Pd = GeV/c) ~ 4 k/spill (at S4) S2 MWDC 2 achromatic SC AC dispersive Fragment Separator (FRS) 19 Scintillator (SC) Aerogel Cherenkov (AC) 72m S4

20 Experimental setup at FRS p (Tp = 2.5 GeV, Ip ~ /spill) 12 C target 2 (4 g/cm ) signal d (Pd = GeV/c) ~ 4 k/spill (at S4) S2 missing-mass resolution : σ ~ 1.6 MeV/c 2 (expected) momentum measurement MWDC 2 achromatic SC AC dispersive Fragment Separator (FRS) 20 Scintillator (SC) Aerogel Cherenkov (AC) 72m S4

21 Experimental setup at FRS p (Tp = 2.5 GeV, Ip ~ /spill) background 12 2 C target (4 g/cm ) p ~ 800 k/spill signal d (Pd = GeV/c) ~ 4 k/spill (at S4) S2 missing-mass resolution : σ ~ 1.6 MeV/c 2 (expected) momentum measurement MWDC 2 achromatic SC AC dispersive Fragment Separator (FRS) βp ~ 0.95 βd ~ Scintillator (SC) Aerogel Cherenkov (AC) 72m S4

22 Particle Identification 10ns/grid S2-S4 TOF (unbiased) p/d ratio ~ 200 / proton TOF S2-S4 20ns preliminary S2-deuteron S4-deuteron Counts Counts 2 10 deuteron S2-proton 10 S4-proton time TOF (S2-S4) + offset [/25ps] TOF (S2-S4) + offset [/25ps] preliminary 22

23 Particle Identification 10ns/grid S2-S4 TOF (unbiased) p/d ratio ~ 200 / proton TOF S2-S4 20ns preliminary S2-deuteron S4-deuteron Counts Counts 2 10 deuteron S2-proton 10 S4-proton time with hardware TOF trigger p/d ratio ~ 1 / TOF (S2-S4) + offset [/25ps] TOF (S2-S4) TOF + S2-S4 offset [/25ps] preliminary Counts accidental multi-hit (proton) deuteron TOF (S2-S4) + offset [/25ps] TOF (S2-S4) + offset [/25ps]

24 Particle Identification 10ns/grid S2-S4 TOF (unbiased) p/d ratio ~ 200 / proton TOF S2-S4 20ns preliminary S2-deuteron S4-deuteron Counts Counts 2 10 deuteron S2-proton 10 S4-proton time with hardware TOF trigger p/d ratio ~ 1 / TOF (S2-S4) + offset [/25ps] TOF (S2-S4) TOF + S2-S4 offset [/25ps] preliminary 99.5 % of BG protons were rejected by TOF trigger without using Aerogel Čerenkov detector Counts accidental multi-hit (proton) deuteron TOF (S2-S4) + offset [/25ps] TOF (S2-S4) + offset [/25ps]

25 Particle Identification Further rejection of the accidental multi-proton in offline analysis - TOF in the last focal plane (SC41-SC42) - Waveform analysis - Aerogel Čerenkov detectors TOF (SC41-SC42) + offset [/25ps] TOF (SC41-SC42) + offset [/25ps] TOF(S2-S4) vs TOF(SC41-SC42) accidental multi-hit (proton) deuteron preliminary 2.5 ns TOF (S2-S4) + offset [/25ps] 25 TOF (S2-S4) + offset [/25ps]

26 Further rejection of the accidental multi-proton in offline analysis - TOF in the last focal plane (SC41-SC42) - Waveform analysis - Aerogel Čerenkov detectors Examples of SC(S2) waveform Particle Identification ADC value deuteron-like preliminary ADC value time [ns] multi-proton-like time [ns] Counts TOF (S2-S4) + offset [/25ps]

27 Calibration Reaction p (Tp = 1.6 GeV ) 2 CD2 target(1 g/cm ) D(p,d)p elastic scattering for spectrometer calibration d (Pd = 2.82 GeV/c) S2 momentum measurement MWDC 2 achromatic SC AC dispersive Fragment Separator (FRS) 27 Scintillator (SC) Aerogel Cherenkov (AC) 72m S4

28 Calibration Reaction X (horizontal position) - X (angle) by MWDC FRS scaling by -2% -1% 0% +1% preliminary 10 +2% X X [mrad] X [mm] X [mm] - Confirmation of the whole system - Ion-optical information (focus, dispersion, higher-order aberration) - Stability check 28

29 Calibration Reaction Focal plane position (online, ion-optics roughly corrected) Count % 0% preliminary FRS scaling by -2% 1% % X at Focal Plane [mm] σx = 2.7 mm (CD2 calibration run) - energy loss and straggling calculation - spectrometer momentum resolution - beam momentum spread σmissing mass ~ 2 MeV/c 2 (production run with 12 C 4g/cm 2 ) 29

30 Run Summary Production run (~ 5 days) - C(p,d) reaction at Tp=2.5 GeV with ~ /spill proton beam and 4 g/cm 2 C target - scaling FRS Bρ from -2% to 2% - for each setting deuterons were accumulated. - calibration run every 6 hours Reference run (~ 0.5 day) - production setting with CD2 target, for D(p,d) spectrum - for understanding background processes (e.g., p+n d+π s) - scaling FRS Bρ from -2% to 2% FRS scaling -2% Region in excitation energy 0% +2% Eex - E0 [MeV]

31 Future Plan at FAIR 31

32 FAIR facilities Facility for Antiproton and Ion Research (FAIR) p-linac SIS-18 SIS-100 / SIS-300 UNILAC CBM HESR Rare Isotope Production Target GSI Plasma Physics PANDA Super-FRS Antiproton Production Target 50 m Atomic Physics RESR/ CR FLAIR NESR 32

33 Future plan at FAIR 1st Step : Inclusive measurement of (p,d) reaction with FRS at GSI 2nd Step : - Inclusive measurement with higher intensity beam at FAIR - Semi-exclusive measurement of (p,dp) with Super-FRS at FAIR missing-mass measurement w/ S-FRS Target η mesic nuclei 33

34 Future plan at FAIR 1st Step : Inclusive measurement of (p,d) reaction with FRS at GSI 2nd Step : - Inclusive measurement with higher intensity beam at FAIR - Semi-exclusive measurement of (p,dp) with Super-FRS at FAIR Target N N η mesic nuclei missing-mass measurement w/ S-FRS decay of η mesic nuclei : - η N ηn or πn - η NN NN Tagging proton in coincidence with deuteron S/N ratio can be improved 34

35 Tagging decay proton signal η mesic nuclei background multi-π production count [a.u.] 1 nucleon absorption nucleon absorption sampling calorimeter (conceptual design) proton beam proton proton momentum [GeV/c] 35 deuteron

36 Tagging decay proton signal η mesic nuclei background multi-π production count [a.u.] 1 nucleon absorption proton momentum [GeV/c] 2 nucleon absorption sampling calorimeter - Simulation of emitted particles from the (conceptual (p,d) reaction design) using microscopic transport model (JAM) proton Talk by Y. beam Higashi proton - Development of proton tagging counter - New DAQ system using 64ch RAINER board O(10kHz) trigger rate, for inclusive measurement 36 deuteron

37 Summary Missing-mass spectroscopy of η mesic nuclei with (p,d) reaction for studying in-medium properties of η meson With large mass reduction (~100MeV) and narrow decay width (~20MeV), η mesic nuclei may be observed in inclusive spectrum. The first inclusive measurement using FRS at GSI has been performed. High-statistics data were obtained with good PID and spectrometer performance. Analysis of missing-mass spectra is currently underway. At FAIR, we plan semi-exclusive measurement of (p,dp) reaction as well as higher-statistics inclusive measurement. Tagging decay protons could improve S/N ratio. R&D is presently on-going. 37