Nonlinear Quantum Electrodynamics

Transcription

1 Nonlinear Quantum Electrodynamics Nikolay B. Narozhny National Research Nuclear University MEPHI, Russia Résidence de France Moscou, 26 avril 2013

2 Today, two exawatt class facilities in Europe are already in the planning stage. ELI 4 th Pillar XCELS, Russia Fms optical pulses As X-ray pulses

3 QED is a nonlinear science at F. Sauter, 1931 W. Heisenberg, H. Euler, 1936 J. Schwinger, 1951

4 The only experiment on Nonlinear QED E144 (SLAC, )

5 Nonlinear Compton scattering Final Focus Test Beam at SLAC C.Bula, et al., PRL, 76, 3116 (1996) C.Bamber, et al., PRD, 60, (1999) IP1 interaction point, ECAL silicon-tungsten calorimeter CCM1 gas Čerenkov monitor schematic drawing of the experiment

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7 The multiphoton version of Breit-Wheeler process was observed D.L.Burke, et al., PRL, 79, 1626 (1997) C.Bamber, et al., PRD, 60, (1999) Pair production: two-step process

8 This was the first (and the only) laboratory evidence for inelastic light-by-light scattering involving only real photons!

9 Parameters of E144 experiment Laser: λ=1.054μm (infrared) and λ=0.527μm (green) The laser intensity could be varied, the maximum focused intensity: Electron beam: The field was close to a monochromatic plane wave field Two Lorentz and gauge invariant parameters Dimensionless intensity parameter (classical nonlinearity parameter) Dynamical parameter (quantum nonlinearity parameter) At the proper frame of electron:

10 Parameters of E144 experiment What we will have with new facilities? Fms optical pulses: Electrons: What does it mean experimentally?

11 1. harmonics are undistinguishable, laser field works as a constant crossed field 2. e-m cascades will be observed Analogue of cosmic-ray air showers The effect was observed at SLAC experiment multiplicity = 0.02 It could be the first experiment on laboratory astrophysics

12 3. Fms optical pulses: Electrons: Expansion parameter of perturbation theory at Narozhny, PRD, 1980 Perturbation theory does not work high energy physics in the presence of extreme laser field is an unexplored branch of science!

13 Nonlinear QED vacuum polarization effects have never been observed! Is it possible with new facilities?

14 Vacuum in the presence of an external e-m field is a non-linear optical medium The start of Nonlinear Optics in Vacuum W. Heisenberg and H. Euler, Zeitschr. Phys. 98, 714 (1936) Hans Heinrich Euler ( ) Werner Karl Heisenberg ( )

15 F. Sauter, ZS. f. Phys. 69, 742, 1931 This polarization of the vacuum to be studied below will give rise to a distinction between the vectors on the one hand and on the other permittivity of vacuum permeability of vacuum

16 Vacuum polarization effects 1. Birefringence and dichroism of vacuum R. Baier, P. Breitenlohner, Acta Phys. Austr. 25, 212, 1967 N.B. Narozhnyi, Zh. Eksp. Teor. Fiz. 55, 714 (1968) [Sov. Phys. JETP 28, 371, 1969] S.L. Adler, Ann. Phys. (NY) 67, 599 (1971) I.A. Batalin, A.E. Shabad, Zh. Eksp. Teor. Fiz. 60, 894 (1971) [Sov. Phys. JETP 33, 483, 1971] 2. Photon splitting S.L. Adler, Ann. Phys. (NY) 67, 599 (1971) Z. Bialynicka-Birula, I. Bialynicka-Birula, Phys.Rev D 2, 2341 (1971) V.O. Papanyan, V.I. Ritus Zh. Eksp. Teor. Fiz. 61, 2231 (1971) [Sov. Phys. JETP 33, 483, 1971] 3. Cherenkov radiation T. Erber, Rev. Mod. Phys. 38, 626, 1966 V.I. Ritus, Zh. Eksp. Teor. Fiz. 57, 2176 (1969) [Sov. Phys. JETP 30, 1181, (1970)] I.M. Dremin, Pis ma Zh. Eksp. Teor. Fiz. 76, 185 (2002) [JETP Lett. 76, 151, (2002)]

17 4. Self-focusing in vacuum N.N. Rozanov, JETP, 86, 284 (1998) M. Soljacˇic and M. Segev, Phys. Rev A, 62, (2000) D. Kharzeev and K. Tuchin, Phys. Rev A, 75, (2007) 5. Light-by-light scattering A. Di Piazza, K.Z. Hatsagortsyan, C.H. Keitel, Phys. Rev. D 72, (2005) B. E. Lundström, et al.,phys. Rev. Lett. 96, (2006) 6. Harmonics generation A.E. Kaplan and Y.J. Ding, Phys. Rev. A 62, (2000) A. Di Piazza, K.Z. Hatsagortsyan, C.H. Keitel, Phys. Rev. D 72, (2005) A.M.Fedotov, N.B. Narozhny, Phys. Lett. A 362, 1 (2007)

18 7. Pair creation by e-m field in vacuum W. Heisenberg and H. Euler, Zeitschr. Phys. 98, 714 (1936) J. Schwinger, Phys.Rev., 82, 664 (1951) N.B. Narozhny, A.I. Nikishov, Yad. Fiz. 11, 1072 (1970). N.B. Narozhny, S.S. Bulanov, V.S. Popov, V.D. Mur, PLA 330, 1 (2004) A.M. Fedotov, Las. Phys., 19, 214 (2009) The most promising nonlinear vacuum effect is PAIR PRODUCTION BY LASER FIELD

19 pair creation by a laser field in vacuum becomes observable at intensities The probability for vacuum to stay vacuum in a constant electric field: - the Heisenberg-Euler correction to em field Lagrangian J. Schwinger, Phys.Rev., 82, 664 (1951)

20 Laser pulse: - focal spot radius - pulse duration

21 at

22 The number of pairs created by an electromagnetic field N.B. Narozhny, S.S. Bulanov, V.S. Popov, V.D. Mur, PLA 330, 1 (2004) In the reference frame where

23 Pair production by a single focused pulse N.B. Narozhny, S.S. Bulanov, V.S. Popov, V.D. Mur, PLA 330, 1 (2004) A.M. Fedotov, Las. Phys., 19, 214 (2009) Δ=0.1 Δ=0.05 Δ= !!

24 Number of pairs is growing very fast after the threshold value of intensity Compare the total energy of produced pairs with the energy of the laser pulse COLLAPSE OF THE LASER PULSE PAIR CREATION IMPOSES LIMITATION ON ATTAINABLE LASER INTENSITY!

25 The threshold can be lowered essentially at the expense of MULTIPLE PULSES TECHNOLOGY Collision geometry (linear polarization) n=2 n=4 n=8 n=16

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27 The number of created pairs and threshold energy for different number of colliding pulses S. S. Bulanov, V.D. Mur, N.B. Narozhny, et al., PRL, 104, (2010)

28 Pair creation from vacuum may be observed with laser fields of the strength 2 3 orders lower than the critical (Sauter) field E S.

29 What will happen after creation of a single pair? Particles are accelerated by the field and Meeting A. R. Bell and J. G. Kirk, Phys. Rev. Lett. 101, (2008). A.M. Fedotov and N.B. Narozhny, in Extreme Light Infrastructure: Report on the GC Meeting, April 2009, Paris, A. M. Fedotov, N. B. Narozhny, G.Mourou and G. Korn, Phys. Rev. Lett. 105, (2010).

30 Vacuum instability initiated by a seed particle Acceleration: Cascade can be self-sustained if the field accelerates charged particles It is not the case for PWF or constant electromagnetic field, where is an integral of motion, The self-sustained cascade can arise only in a focused laser field, or for colliding laser pulses

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32 Estimation: An electron can be accelerated by the field many times for 1 period

33 The electron (positron) radiation lifetime (mean free path/c) The photon lifetime The escape time

34 The following hierarchy of time scales should be respected for occurrence of electromagnetic cascade (for optical frequencies) - determines a natural threshold for electromagnetic cascades.

35 The self-sustaining e-m cascades strongly differ from cosmic ray air showers The difference: the laser field is not only a target for primary particles, but also an accelerator for slow particles

36 Present days PW laser + LWFA? NO! 1. Particles loose energy very quickly! 2.Mechanism of acceleration begins to work, if the field is strong enough, and we have revival of the cascade.

37 seed particle The number of created pairs/shot The maximum number of created pairs limited by the energy of the laser pulse

38 Fedotov, A. M.; Narozhny, N. B.; Mourou, G.; Korn, G. PRL, 105, (2010) FIG. 2. Pair production as a function of. The solid curve corresponds to the number of pairs produced by a single cascade process. The dotted curve shows the number of pairs produced by multiple cascades generated by pairs created by two colliding circularly polarized 10 fs laser pulses. The branching point corresponds to the threshold value of where the spontaneous pair production begins. The dash line shows the limit for determined by the energy of the laser pulse. The laser frequency ћω = 1 ev. The inset shows the magnified region of intersection of the curves.

39 The QED cascades (avalanche production of hard photons and electron-positron pairs) catalyzes depletion of the initiating laser pulses. This confirms the N. Bohr s conjecture that the critical QED field strength can be never attained for a pair creating electromagnetic field!

40 Monte-Carlo code for simulation of cascades in EM field has been developed N. V. Elkina, A. M. Fedotov, I. Yu. Kostyukov, et al., PR ST AB 14, (2011) The results support qualitative estimations of A. M. Fedotov, et al., PRL 105, (2010).

41 The increment Γ as a function of the dimensionless field strength µ for two rotation frequencies ћω = 1 ev and ћω = 0:66 ev

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43 In calculations (both, estimations and Monte-Carlo simulations): 1. The laser field was modeled by a uniformly rotating homogeneous electric field (toy model); 2. Back-reaction was neglected. The next step: seed particle A 2D numerical model to study production and dynamics of EPPP in the field of two colliding linearly polarized laser pulses is developed. The laser pulses have Gaussian envelopes and propagate along the x axis. E.N. Nerush, I. Yu. Kostyukov, A. M. Fedotov, et al., PRL 106, (2011)

44 QED cascade stops when the laser energy is almost completely converted into the cascade energy.

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46 At the initial stage of the cascade development, the number of created particles is growing exponentially. Then the growth substantially slows down.

47 Development of e-m cascade by itself leads to depletion of the laser pulse!

48 THANK YOU FOR ATTENTION!