Search for mesic nuclei in the photoproduction of and ' mesons - PowerPoint PPT Presentation

Search for mesic nuclei in the photoproduction of η and η ' mesons off light nuclei I.Keshelashvili Group of Prof. B. Krusche University of Basel

Outline Outline ✔ Introduction ✔ Experimental Setup ✔ Data Analysis ✔ Results ✔ Conclusion η γ p p n p p University of Basel I.Keshelashvili FAIRNESS'13 [ 2]

Basel group EMC @ PANDA, PreAmp & HV & HV Basel group EMC @ PANDA, PreAmp Low Noise/Low Power ( LNP ) preamplifier for APD and VPTT W. Erni, M. Steinacher, I. Keshelashvili, B. Krusche Material: PbW0 4 - 22 X 0 Crystal size: 2 cm x 2 cm x 20 cm Energy resolution: 1.54% / √E/[GeV]+0.3% Number of crystals: 15552 Forward EMC: 3600 – Basel LNP Per crystal 2xAPD or VPTT Cooled down to -25 o C University of Basel I.Keshelashvili FAIRNESS'13 [ 3]

Basel group EMC @ PANDA, PreAmp & HV & HV Basel group EMC @ PANDA, PreAmp 2013 2014 Development Test setup L Apache/PHP/MySQL I Mass-production N U ROOT based DAQ + slow control X RS232 RS232 RS232 USB3 FPGA NIM - HV Power VME - SADC Generator ISEG Low V / I[nA] Struck 12bit, 500MS/s <10nA> Trigger 2xCH 1xCH 2xCH 'APD' LNP PreAmp Pulser University of Basel I.Keshelashvili FAIRNESS'13 [ 4]

Introduction University of Basel I.Keshelashvili FAIRNESS'13 [ 5]

Strong Interaction Strong Interaction η FSI ISI A A University of Basel I.Keshelashvili FAIRNESS'13 [ 6]

Why coherent production? Why coherent production? 1) Coherent η 3) Incoherent (XS small) η γ p n p p γ n n p p p n n p p n 2) Break-Up (main BG) 4) Double meson η γ η γ p p p n p n n n p p p p p π 0 University of Basel I.Keshelashvili FAIRNESS'13 [ 7]

History History 1985: Bhalerao & Liu: coupled-channel analysis experiments: attractive s-wave η -A ; π− induced for A≥12 threshold behavior scatt. lengths: Re: 0.27-0.28 fm Im: 0.19-0.22 fm; of η -production 1986: Liu & Haider: suggestion of η -nucleus bound states for A>10 experiments: inconclusive evidence: Chrien et al. (1988): π + + 16 O→p+ η 15 O Johnson et al. (1993): π + + 18 O→ π− + η 18 Ne Sokol et al. (99): γ + 12 C→p(n)+ η 11 B(C)→ π + +n+X 1993 - 2002: analysis of new η -production data from the proton: larger η N-scattering lengths 1991 - 2002: T. Ueda, C. Wilkin, S.A. Rakityanski and others: suggestions of bound 2 H-, 3 H-, 3 He-, 4 He- η states University of Basel I.Keshelashvili FAIRNESS'13 [ 8]

η -meson case special? Why is the η -meson case special? Why is the ● η -photoproduction dominated by excitation of S 11 (1535) → spin-flip transition ● Expectation for light nuclei: I) 4 He: J=0, I=0, isoscalar, non spin-flip → very small signal (not seen, only upper bounds, V. Hejny et al.) II) 2 H: J=1, I=0, isoscalar, spin-flip → small signal (seen, almost in agreement with expectations) III) 3 He: J=1/2, I=1/2, isovector, spin-flip → ‘large’ signal University of Basel I.Keshelashvili FAIRNESS'13 [ 9]

η – mesic TAPS - Photoproduction of η – mesic 3 He TAPS - Photoproduction of 3 He Photoproduction of eta-mesic 3 He M. Pfeiffer at al. Phys. Rev. Lett. 92 (2004) 252001 University of Basel I.Keshelashvili FAIRNESS'13 [ 10]

η He η ANKE - Excitation function: dp→ 3 ANKE - Excitation function: dp→ 3 He η p p p n p p p p n n p ANKE @ COSY, PRL 98, 242301 χ 2 /n free =0.82 University of Basel I.Keshelashvili FAIRNESS'13 [ 11]

Experiment University of Basel I.Keshelashvili FAIRNESS'13 [ 12]

MAMI (Ma Mainzer inzer Mi Mikrotron) krotron) MAMI ( continuous wave University of Basel I.Keshelashvili FAIRNESS'13 [ 13]

Glasgow Tagger Glasgow Tagger Crystal Ball Experiment ~1.6GeV 352 Plastic ~400MeV Scintillators ∆ E ~ 2-4MeV quadrupole 1m radiator MAMI-C e - beam University of Basel I.Keshelashvili FAIRNESS'13 [ 14]

How to get the photon energy? How to get the photon energy? E γ =E e -E e ' N E e ' 1/E γ E e B E e Ε γ Photon Energy N Real Events I II Time (Tagger vs CB/TAPS) University of Basel I.Keshelashvili FAIRNESS'13 [ 15]

Crystal Ball / TAPS Detector Crystal Ball / TAPS Detector Crystal Ball TAPS 672 NaI(Tl) BaF 2 + PWO Polarized Target PID 24 Pl.Sci. VETO 384 Pl.Sci. University of Basel I.Keshelashvili FAIRNESS'13 [ 16]

Crystal Ball detector at SPEAR @ SLAC Crystal Ball detector at SPEAR @ SLAC SPEAR began 1972 ✗ e - e + @ 3GeV ✗ J/ ψ meson ✗ Nobel price 1976 +many charmonium ✗ states SLAC, DASY, BNL, MAMI ✗ University of Basel I.Keshelashvili FAIRNESS'13 [ 17]

Crystal Ball / TAPS Detector Crystal Ball / TAPS Detector Invariant Mass Missing Energy or Mass TAPS BaF 2 Pulse Shape TOF – Time-Of-Flight University of Basel I.Keshelashvili FAIRNESS'13 [ 18]

Analysis University of Basel I.Keshelashvili FAIRNESS'13 [ 19]

Data Analysis Data Analysis TAPS Time TAPS - Tagger PID Scintillators University of Basel I.Keshelashvili FAIRNESS'13 [ 20]

Results γ+3 He →3 He+ η University of Basel I.Keshelashvili FAIRNESS'13 [ 21]

η γ p p n p p University of Basel I.Keshelashvili FAIRNESS'13 [ 22]

η photoproduction off Coherent η photoproduction off 3 He Coherent 3 He ME coherent η off 3 He - 2 γ (left) and 3 π 0 /6γ (right) University of Basel I.Keshelashvili FAIRNESS'13 [ 23]

η photoproduction off Coherent η photoproduction off 3 He Coherent 3 He Sys. Err. Shevchenko et al. 3N system in a microscopic few-body description. Strong dependence on the elastic ηN rescattering. Strong threshold effects, bad reproduction above the breakup threshold Fix et al. 3 He and 3 H in PWIA, in a distorted-wave impulse approximation (DWIA) using optical potential. Strong FSI effects. Underestimates XS. Tiator et al. model was based on the PWIA. Strongly underestimates measured XS and does not reproduce the energy dependence. University of Basel I.Keshelashvili FAIRNESS'13 [ 24]

η photoproduction off Coherent η photoproduction off 3 He Coherent 3 He (Red) η→2γ decay (Blue) η→6γ decay The behavior of the angular distributions of the PWIA is dominated by the nuclear form factor, which is responsible for the strong forward peaking. Solid (dashed) curves: PWIA with realistic (isotropic) angular distribution for γ n → n η University of Basel I.Keshelashvili FAIRNESS'13 [ 25]

η – mesic Photoproduction of η – mesic 3 He Photoproduction of 3 He simulation of opening angle behavior for quasi-free π 0 production and η -mesic state ● nucleon resonances produce opening angle dependent structures in excitation functions ● subtraction of excitation functions for different opening angles can produce artificial structures almost everywhere ● basically no hope to isolate tiny structure from η -mesic state in this complicated landscape! University of Basel I.Keshelashvili FAIRNESS'13 [ 26]

η – mesic Photoproduction of η – mesic 3 He Photoproduction of 3 He γ+ 3 He →(η 3 He )→ p +π 0 + X Excitation functions x E γ 6 Excitation functions University of Basel I.Keshelashvili FAIRNESS'13 [ 27]

Summary I Summary I γ+3 He →3 He+ η ✗ Strong threshold enhancement and shape of angular distributions confirmed ✗ Evidence for very strong FSI effects ✗ Alternative decay channel π 0 -p back-to back suffers from complicated background structure, signal not confirmed University of Basel I.Keshelashvili FAIRNESS'13 [ 28]

Coherent η -photoproduction off 7 Li nuclei (Ph.D. work of Yasser Maghrbi) University of Basel I.Keshelashvili FAIRNESS'13 [ 29]

η - photoproduction off Coherent η - photoproduction off 7 Li Coherent 7 Li ME coherent η off 7 Li - 2 γ (left) and 3 π 0 /6γ (right) University of Basel I.Keshelashvili FAIRNESS'13 [ 30]

η - photoproduction off Coherent η - photoproduction off 7 Li Coherent 7 Li University of Basel I.Keshelashvili FAIRNESS'13 [ 31]

η - photoproduction off Coherent η - photoproduction off 7 Li Coherent 7 Li X University of Basel I.Keshelashvili FAIRNESS'13 [ 32]

η – mesic Photoproduction of η – mesic 7 Li Photoproduction of 7 Li γ+ 7 Li →(η 7 Li )→ p +π 0 + X University of Basel I.Keshelashvili FAIRNESS'13 [ 33]

Coherent η′ -photoproduction off LD and 3 He nuclei (Ph.D. work of Roman Trojer) University of Basel I.Keshelashvili FAIRNESS'13 [ 34]

η′ - photoproduction off Coherent η′ - photoproduction off LD LD Coherent γ+ d → X +η′→ X +η(γγ)π 0 (γγ)π 0 (γγ) University of Basel I.Keshelashvili FAIRNESS'13 [ 35]

η′ - photoproduction off Coherent η′ - photoproduction off LD LD Coherent γ+ d → X +η′→ X +η(γγ)π 0 (γγ)π 0 (γγ) University of Basel I.Keshelashvili FAIRNESS'13 [ 36]

η′ - photoproduction off Coherent η′ - photoproduction off 3 He Coherent 3 He γ+ 3 He → X +η′→ X +η(γγ)π 0 (γγ)π 0 (γγ) University of Basel I.Keshelashvili FAIRNESS'13 [ 37]

η′ - photoproduction off Coherent η′ - photoproduction off 3 He Coherent 3 He γ+ 3 He → X +η′→ X +η(γγ)π 0 (γγ)π 0 (γγ) University of Basel I.Keshelashvili FAIRNESS'13 [ 38]