15th International Seminar on Electromagnetic Interactions of Nuclei (EMIN-2018), Moscow, 9 th Oct. 2018 Delbruck Scattering using linearly polarized Laser Compton Scattering gamma-rays National Institutes for Quantum and Radiological Science and Technology (QST) T. Hayakawa
Contents Introduction: photon-photon interactions Proposal of selective measurement of Delbruck scattering using linearly polarized laser Compton scattering beam J. Koga and T. Hayakawa, Phys. Rev. Lett. 118, 204801 (2017). Generation of 1-MeV quasi-monochromatic gamma-ray for precise measurement of Delbrück scattering by laser Compton scattering H Zen, T Hayakawa, E Salehi, M Fujimoto, T Shizuma, J K Koga, T Kii, M Katoh and H Ohgaki, J. Phys. Coference series, 1067, 092003 (2018).
Interactions between photon and photon QED predicated that a photon can interact with another photon. From 1930’s, the photon-photon interaction has been studied experimentally and theoretically. However, the cross sections are extremely low, and it has been an open question. Photon-photon scattering Photon splitting Photon-photon combing Delbrück Scattering
Photon-photon scattering X-rays scattering using XFEL ・ SALCA Experiment using LHC 11 keV X-ray High energy new Vol.34 No.2 2015/07.08.09 in Japanese ATLAS Pb-Pb heavy ion collision First measurement of photon-photon scattering. 5 TeV gamma-rays with uncertainty of 25% T. Inada, Only 13 events. Phys. Lett. B, 732, 356 (2014) ATLAS Collaboration, Nat. Phys. (2017).
Photon splitting Sh. Zh. Akhmadaliev, Phys. Rev. Lett. 89, 061802 (2002) LCS gamma-rays Laser Target Detector Electron The measurement of the gamma-ray energy after the target with the incident 450-MeV gamma-ray beam. Double Compton scattering made background events.
X-rays from soft gamma-ray repeater X-ray pattern NASA X-ray energy spectra show two components. A candidate for lower component is photon splitting in strong magnetic fields. Candidate is a magnetar (neutron star with strong magnetic fields.) G. Younes, Astrophys. J. 785, 52 (2014)
Delbrück Scattering Scattering of a photon by Coulomb field of nucleus L. Meitner, H. Kỏsters (including M. Delbrück’s idea), Z. Phys. 84 (1933) 137 Scattered gamma-ray Electron Pair creation Annihilation Positron Gamma-ray Nucleus The energy of scattered photon is almost identical to the incident photon energy. The cross section for Delbrück scattering is much larger than other photon-photon interactions.
Previous experiments for Delbrück Scattering Many experiments were carried out using Measurement using LCS gamma-ray radioactivity and neutron capture gamma-rays at in the energy range of 140-480 MeV nuclear reactors with energies lower than 3 MeV. P. Rullhusen, Nucl. Phys. A 313, 307 (1979). 24 Na(T1/2=15.02h) 150 mCi Scattering samples: Th and Bi (500g ) Ge: 76cc Sh. Zh. Akhmadaliev, Phys. Rev. C 58, 2448 (1998).
Elastic scattering Scattered photon Energy E’ Incident photon Delbruck scattering Energy E E ≈ E’
Elastic scattering Scattered photon Energy E’ ? Incident photon • atomic Rayleigh (R) • nuclear Thomson (T) Energy E • GDR • Delbrück (D) E ≈ E’ There is the interference between several elastic scattering.
Total coherent elastic scattering amplitude 4 COHERENT CONTRIBUTIONS TO THE ELASTIC SCATTERING
Higher orders Lowest order Feynman diagrams k , k’ incoming and outgoing g • • i, j polarization lowest order (Z a ) 2 • X Coulomb field D momentum transfer • Higher order Feynman Diagrams x e + x x x x g g e + g ' g ' e + e + e + Higher orders in gamma-ray e - e - e - e - energy has not e - x x x x been calculated. x Higher order (Z a ) 2n n=2,3,4 Higher orders of Delbruck scattering proportional to Z^4, Z^6,,,,
Candidates of Higher orders Z = 92 Contribution of Delbrück larger than Rayleigh Photon energies>1 MeV Signatures of higher orders of Delbruck scattering on 238 U were observed. However, the enhancements originated from resonances on unobserved levels. Delbrück Higher orders were not Rayleigh clearly measured. P. Rullhusen et al., Nucl. Phys. A382 , 79 (1982)
la laser C Compt pton sc scat atterin ing gam amma-ray ay be beam am MeV energy facilities HIgS (Duke Uni.) • Semi-monochromatic energy NewSUBARU dE/E =1~10% • Energy Turntable • Almost 100% Linear (Circular) polarization UVSOR-III
New idea Detector Differential cross sections depends on the angle between the scattered plane and the linear polarization Scattered gamma-rays plane. We search a specific condition at 70 degree which we can observe selectively the Linear polarization amplitude of Delbruck scattering . plane Target LCS gamma-rays
A new code with Feynman diagram by J. Koga An example of calculated results New code using the lowest order Feynman diagram. Present algorism package to calculate qucikly. J.Koga, T.Hayakawa, IFSA 2013, proceedings. We found that the calculation can not be finished even if we use the supercomputer K.
Return to Classical calculation ・ Nuclear Tomson scattering Well known ・ GDR ・ Rayleigh L. Kissel is the last researcher, who was retired around 2000. Second order s-matrix calculation We got his code from him. ・ Delbruck scattering De Tollis’s calculatioin
Differential Cross section Circular polarization Linear polarization (perpendicular/parallel to scattering plane) We use the formulae obtained by: B. De Tollis, M. Lusignoli, and G. Pistoni, Il Nuovo Cimento A Series 11 32, 227 (1976) B. De Tollis and G. Pistoni, Il Nuovo Cimento A Series 11 42, 499 (1977) B. De Tollis and L. Luminari, Il Nuovo Cimento A Series 11 81, 633 (1984).
Results by J. Koga Target ： Tin Gamma-ray energy : 1.1 MeV • Real part • Imaginary part Negative ! Angle Angle We found that the real part corresponding to virtual process has negative values lower than about 70 degree.
Proposal of a new experiment Cross sections Proposed experiment Detector Scattered gamma-rays 70 degree Linear polarization plane Target LCS gamma-rays If we use a linearly polarized gamma-rays as the incident beam, we can selectively measure the cross section of the Delbruck scattering at 70 degree.
Energy Dependence by J. Koga Minimum near ~71 o The minimum angle dose not depend on the energy of the incident photon.
Possible experiment at ELI-NP EI-NP has constructed the next generation of highly intense laser Compton scattering gamma- ray source. Expected gamma-ray beam g 5 10 3 / s / eV E g = 1.1 MeV D E g 5 10 − 3 E g 5.5 keV 2.75 10 7 / s http://www.eli-np.ro/ Detector detection angle D = 0.8 D = 2 (1 − cos D 2 ) = 1.5 10 − 4 We can obtain the cross section with statistical uncertainty of 1% with only 76 day measurement.
How about detecting below 1.022 MeV Energy Gamma-rays Imaginary Part Real pair creation High energy + Real Part Virtual pair creation H. E. Jackson and K. J. Wetzel, PRL 22 (1969) 1008 1.022 MeV Virtual pair creation Below 1.022 MeV real, only vacuum contribution Low energy We generate 1-MeV LCS gamma-ray beam at anywhere
MeV energy LCS gamma-ray facilit ies 1990’s ~ TERAS in AIST HIgS in Duke University Shutdown by the 2011 tohoku earthquake Compton scattering with FEL 2005 年 ~ UVSOR-III in Okazaki ELI-NP high flux NewSUBARU in Spring-8 gamma-ray source Near future LCS gamma-ray generation with 2 um fiver laser H.Zen, et al. Energy Procedia 89 ( 2016 ) 335. 24
UVSOR-III 1 GeV top-up mode operation NewSUBARU + CO 2 laser LCS gamma-ray energy is 1.7 MeV 1.7 MeV is table in low energy region HIgS Not available ELI-NP 750 MeV top-up mode operation UVSOR-III + CO 2 laser LCS gamma-ray energy is just below 1 MeV
LCS gamma-rays at UVSOR-III BL1U beam line LCS γ -rays Detector CO2 laseer Inverse Compton scattering Access Laser LASY20D UVSOR-III Polarization : random Energy: 750MeV Ave. Power ： 20W （ 28V ） Energy Spread: 5.3x10 -4 Beam diameter ： 2.4mm Current ： 300mA M 2 ： below 1.2 Bunch length: 128 ps Wave length ： 10.59 μm
Generation of 1-MeV gamma-ray at UVSOR-III LaBr 3 (Ce) Scintillator 3.5” × 4” 3.0 w/o CO 2 Laser 600 2.5 1 MeV with CO 2 Laser Counts [#/keV/s] 138 La 2.0 Counts per Channel 40 K 400 1.5 1.0 200 0.5 138 La 789 keV, 0.0 0 0 500 1000 1500 500 1000 1500 Energy [keV] Gamma-ray Energy [keV] Difference spectrum which was calculated Measured spectrum with and without CO 2 by subtracting the spectrum without the laser injection. The CO 2 laser power was 1.1 CO 2 laser from the spectrum with the CO 2 W and the electron beam current was 1.3 laser. mA.
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