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Tests of beam-beam effects with strong field QED experiments in crystals Ulrik I. Uggerhøj Department of Physics and Astronomy Aarhus University, Denmark Beamstrahlung Beam-beam interaction Electric field from one bunch boosted by 22 as seen by particles in the other bunch Small beams, high Lorentz factors => Strong electromagnetic fields => Beam focusing Increase of luminosity Beamstrahlung Synchrotron radiation ’Typical’ fraction of energy radiated classically B photons electrons Beamstrahlung High energy, high luminosity ’Typical’ fraction of energy radiated classically For high energy and high luminosity (unless ’ribbon pulses’ are used): Classical synchrotron-radiation Classical synchrotron radiation 10 Incident energy, Ee=10 GeV dN/d 1 Critical energy 0.1 0.01 Standard magnet, B = 1 T, 1m Si <110>max , Bequiv = 25.000 T, 0.1 mm 0.001 0.001 0.01 0.1 1 10 100 Photon energy [MeV] 1000 10000 100000 D. Schulte Strong, but partial, suppression compared to classical beamstrahlung From the ’locals’ But do we know (i.e. do experiments show) that these formulas are correct? Strong fields Other kinds of motivation… heavy ion collisions Superstrong field, but of short duration E1s/E0 = 3Z3 Extended nucleus: Z 172 Coherent pair production “The total capture cross sections are dominated by electron capture from pair production ...” Strong lasers (-collisions ) -collision scheme (Telnov et al.) Laser wavelength (and energy) limited by non-linear Compton scattering χ (or ) 1 Plasma wakefields Transverse focusing forces: Lead to values for realistic parameters: Magnetars • Magnetars • B 1010 T • relativistic gyration: ħ/mc2 = B/B0 • Electrosphere of strange stars: ≈ 5-100 T=0.01 MeV T=15 MeV The strong magnetic field of the Earth 1,0 0,9 a Conversion probability 0,8 0,7 0,6 0,5 0,4 0,3 0.53 G 0.25 G 0,2 0,1 0,0 10 100 Photon energy [EeV] 1000 Hawking radiation as a strong field effect Gravitatonal acceleration at Schwarzschild radius: g(RS)=c4/4GM RS=2GM/c2 Set equal to critical field acc.: g0=eE0/m=c2/c Light (small) black holes are hotter: c=2RS Beamstrahlung | V Crystals ? What are the invariants? Motion perpendicular to an electric field: Recall: Synchrotron-radiation in a critical field Classical synchrotron radiation 1.0 10 Incident energy, Ee=10 GeV 0.8 dN/d 1 0.6 Critical energy 0.1 0.01 0.4 Standard magnet, B = 1 T, 1m Si <110>max , Bequiv = 25.000 T, 0.1 mm 0.001 0.001 0.2 0.01 0.1 1 10 100 Photon energy [MeV] I/Icl 0.0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1 0.1 0.01 1E-3 0.01 0.1 1 10 100 J. Schwinger, 1954 See, e.g. Berestetskii, Pitaevskii, Lifshitz – Quantum electrodynamics 1000 10000 100000 Similar situations ? Blankenbecler, Drell (PRD 36, 277 (1987), Quantum treatment of beamstrahlung: ”Pulse transforms into a very long narrow ’string’ of N charges.” ILC / CLIC Bunch-size: 3000.60.006 μm3, 2·1010 particles Density: 0.005 Å-3, 0.6 Å-3 (at IP) Si crystal Density: 0.05 Å-3, of Z = 14 Strong fields in crystals Experiments on strong field QED in crystals (CERN NA43 and NA63) J.U. Andersen, H. Knudsen, S.P. Møller, A.H. Sørensen, E. Uggerhøj, U.I. Uggerhøj Department of Physics and Astronomy, Aarhus University, Denmark P. Sona Dipartimento di Fisica, Universitá degli Studi di Firenze, Polo Scientifico, Sesto F.no, Italy S. Connell, S. Ballestrero Schonland Research Institute, Johannesburg, South Africa T. Ketel NIKHEF, Amsterdam, Holland S. Kartal, A. Dizdar Department of Physics, Istanbul University, Turkey A. Mangiarotti Laboratório de Instrumentação e Física Experimental de Partículas, Coimbra, Portugal Strong crystalline fields Crystals Extremely strong electric fields 1010-1011 V/cm Channeling transverse potential 50 V / 0.1 Å = 5·1010 V/cm ’Super-critical’ fields 9 Electric field in units of =E/Ec Relativistic invariant: Ge <110> at 100 K 8 7 6 5 4 3 2 16 Ec=mc /eC=1.3*10 V/cm 2 1 0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Distance from atomic string [A] 0.8 0.9 1.0 Formation length High particle energy, low photon energy: Long formation length 250 GeV e-, 1 GeV γ: 0.1 mm NA63 experiment Crystal on goniometer Total length of setup: 65 m => good angular resolution (few μrad) Strong crystalline fields • Critical fields can be simulated in a crystal. • Example: Radiation emission in diamond (CERN NA43) One of the complications Setting up within a few days: Electronics, hardware, crystal target…. Strong crystalline fields • Critical fields can be simulated in a crystal. • Example: Pair production in Ge (CERN NA43) Similar results obtained in W and Ir Quantum synchrotron χ << 1 Synchrotron-radiation 1.0 0.8 0.6 0.4 0.2 I/Icl 0.0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1 0.1 0.01 1E-3 0.01 0.1 1 10 100 Schwinger, Proc. Nat. Acad. Sci. 1954; Berestetskii, Lifshitz, Pitaevskii Beamstrahlung – synchr.rad. Quantum suppression of intensity 1.0 Synchrotron radiation Blankenbecler & Drell, eq. (7.5) 0.8 0.6 0.4 0.2 0.0 -4 Classical: -> 0 => Cb -> infty -2 0 log10(1/), log10(C) 2 4 Quantum-synchrotron (CERN NA43) Classical = linear Beamstrahlung, D. Schroeder Spin-flip Spin-flip Spin-flip ’Polarization time’ Similar situations Blankenbecler, Drell (PRD 36, 277 (1987), Quantum treatment of beamstrahlung: ”Pulse transforms into a very long narrow ’string’ of N charges.” ILC / CLIC Bunch-size: 3000.60.006 μm3, 2·1010 particles Density: 0.005 Å-3, 0.6 Å-3 (at IP) Si crystal Density: 0.05 Å-3, of Z = 14 Spin contr. to beamstrahlung Blankenbecler and Drell, ”Quantum treatment of beamstrahlung”, PRD 36, 277 (1987) Radiation from crystal 1.0 0.9 =100 0.8 Total pure spin no spin C ≈ 1/χ dN/d [Arb.] 0.7 0.6 0.5 0.4 0.3 0.2 Spin-flip contribution: 0.1 0.0 0.0 0.2 0.4 0.6 Fractional photon energy, =h/Ee 0.8 1.0 Spin contr. to beamstrahlung 35 GeV, =1.0 no spin w/ spin 2.0 1.8 1.6 Power, dN/d 1.4 Blankenbecler and Drell, ”Quantum treatment of beamstrahlung”, PRD 36, 277 (1987) 1.2 1.0 0.8 0.6 0.4 0.2 0.0 0.0 0.2 0.4 0.6 Fractional photon energy, =h/Ee 0.8 1.0 Trident production (electroproduction) ’Coherent pairs’ ’Landau-Lifshitz process’ Electroproduction “The probability of photon radiation during beam-beam collision in linear colliders turns out to be of the order of unity and the density of accompanying photons becomes comparable to the density of the charged particles in the colliding beams. At these photons are converted with high probability in electron-positron pairs in the field of the counter-moving beam.” Amorphous case Electroproduction of electron-positron pair in a medium Authors: V. N. Baier, V. M. Katkov arXiv:0805.0456v1 [hep-ph] Direct Sequential Direct process dominates below 30 GeV Non-aligned crystal 0.035 170 m Ge <110> Experiment Theory Photons Sum a) 0.030 E0dN/dE+ 0.025 Geometric acceptance 0.020 0.015 Small multihit capability 0.010 0.005 0.000 1 2 3 Positron momentum [GeV/c] JETP Lett.88:80-84,2008 4 5 Aligned crystal enhancement 10 1 180 GeV, 170 m Theory Experiment, positrons Experiment, electrons a) 1 2 p [GeV/c] Phys. Lett. A, accepted 3 4 5 Summary • Experiments in crystals may address today: – Coherent pairs – Electroproduction – Beamstrahlung (radiation) • Quantum reduction • Spin-flip processes in the >> 1 regime relevant for beamstrahlung in future linear colliders. More about these and related effects in: •H.D. Hansen, U.I. Uggerhøj, C. Biino, S. Ballestrero, A. Mangiarotti, P. Sona, T. Ketel and Z.Z. Vilakazi: Is the electron radiation length constant at high energies?, Phys. Rev. Lett. vol. 91, 014801 (2003) •H.D. Hansen, U.I. Uggerhøj, C. Biino, S. Ballestrero, A. Mangiarotti, P. Sona, T. Ketel and Z.Z. Vilakazi: The LPM effect for multi-hundred GeV electrons, Phys. Rev. D vol. 69, 032001 (2004) •U.I. Uggerhøj, H. Knudsen, S. Ballestrero, A. Mangiarotti, P. Sona, T.J. Ketel, A. Dizdar, S. Kartal and C. Pagliarone: Formation length effects in very thin targets, Phys. Rev. D vol. 72, 112001 (2005) •H.D. Thomsen, K. Kirsebom, H. Knudsen, E. Uggerhøj, U.I. Uggerhøj, P. Sona, A. Mangiarotti, T.J. Ketel, A. Dizdar, M. Dalton, S. Ballestrero and S. Connell: On the macroscopic formation length for GeV photons, subm. to Phys. Lett. B (2008) •T. Virkus, U.I. Uggerhøj, H. Knudsen, S. Ballestrero, A. Mangiarotti, P. Sona, T.J. Ketel, A. Dizdar, S. Kartal and C. Pagliarone (CERN NA63): Direct measurement of the Chudakov effect, Phys. Rev. Lett. vol. 100, 164802 (2008) •J. Esberg, K. Kirsebom, H. Knudsen, H.D. Thomsen, E. Uggerhøj, U.I. Uggerhøj, P. Sona, A. Mangiarotti,, T.J. Ketel, A. Dizdar, M. Dalton, S. Ballestrero, S. Connell (CERN NA63): Addressing the Klein paradox by trident production in strong crystalline fields, in preparation (2008) Thank you for your attention!