SNAPMOC S REC TA PION POLARIZABILITY Murray Moinester Tel Aviv University Institute of Nuclear Theory, University of Washington, August 2012
![The polarizabilities [in 10 -4 fm 3] The polarizability (electric and magnetic ) relates](https://present5.com/presentation/7b9c224ef62a562637e3d828691db1a0/image-2.jpg "The polarizabilities [in 10 -4 fm 3] The polarizability (electric and magnetic ) relates")
The polarizabilities [in 10 -4 fm 3] The polarizability (electric and magnetic ) relates the average dipole (electric p and magnetic ) moment to an external electromagnetic field, characterizing the rigidity of the quark-antiquark system The pion polarizabilities can be described in the framework of the Chiral Perturbation Theory ( PT) based on the chiral symmetry of QCD and Goldstone theorem using the effective chiral lagrangian The numerical values are: (απ+βπ)= 0. 16; (απ-βπ)=(5. 7± 1. 0) [1] Other models (dispersion sum rules[2], QCD sum rule[3], lattice calculations[4], …) predict quite different value for the pion polarizabilities : 0<(απ+βπ)<0. 39; 3. 2<(απ-βπ)<11. 2 [5] [1] J. Gasser et al. , Nucl. Phys B 745 (2006) 84 -108 [2] L. V. Fil’kov et al. , Eur. Phys. J. A 5 (1999) 285 [3] M. J. Lavelle et al. , Phys. Lett. B 335 (1994) 211 [4] W. Wilcox. , Phys. Rev D 57 (1998) 6731 [5] A. Wilmot et al. , Phys. Rev. C 65 (2002) 035206
The Primakoff reaction + Z ’ + Z + ’ Inverse kinematics for the Compton scattering: γ*π→γπ’ In the incoming pion rest frame (Anti-laboratory system) γ γ* Z, A απ, βπ independently ω is the energy of the virtual photon in the anti-laboratory sys. Assuming (απ+βπ)= 0 in the Laboratory system: βπ Q 2 max depends on analysis cut Eγ is the energy of the real photon
![Experimental values Experiment Reaction [10 -4 fm 3] Lebedev γp→γπ+n 20± 12 PLUTO γγ→π+π-](https://present5.com/presentation/7b9c224ef62a562637e3d828691db1a0/image-17.jpg "Experimental values Experiment Reaction [10 -4 fm 3] Lebedev γp→γπ+n 20± 12 PLUTO γγ→π+π-")
Experimental values Experiment Reaction [10 -4 fm 3] Lebedev γp→γπ+n 20± 12 PLUTO γγ→π+π- 19. 1± 4. 8± 5. 7 DM 1 γγ→π+π 17. 2± 4. 6 DM 2 γγ→π+π 26. 3± 7. 4 MARK II γγ→π+π 2. 2± 1. 6 Serpukhov πZ→πZγ 6. 8 ± 1. 4± 1. 2 Experiment Reaction ( +β)[10 -4 fm 3] Serpukhov πZ→πZγ 1. 4± 3. 1± 2. 8 Experiment Reaction ( -β) [10 -4 fm 3] Serpukhov πZ→πZγ 13. 6 ± 2. 8 MAMI-A 2 γp→γπ+n 11. 6± 1. 5± 3. 0± 0. 5 The experiments are affected by too large statistical and/or systematic errors
COMPASS NA 58 experiment at CERN SPS COmmon Muon and Proton Apparatus for Structure and Spectroscopy 20 Institutes/11 counties/~230 physicists Czech Republic, Finland, France, Germany, India, Israel, Italy, Japan, Poland, Portugal and Russia Bielefeld, Bochum, Bonn, Burdwan/Calcutta, CERN, Dubna, Erlangen, Freiburg, Lisbon, Mainz, Moscow, Munich, Prage, Protvino, Saclay, Tel Aviv, Torino, Trieste, Warsaw and Yamagata
COMPASS at CERN Lake LEMAN COMPASS Airport SPS LHC CERN (France) N CERN (Suisse) • p up to 400 Ge. V 16/03/2018 BEACH 08 • secondary hadrons ( , K, . . . ): 2· 107/s 26 june 2008 19 • tertiary (polarized): 4· 107/s. New Frontiers in QCD, February 5, 2010 Takahiro Iwata
Trigger Experimental conditions during the 2004 hadron run (7 days) • Beam: 190 Ge. V/c; ~106 π/s, 4. 8 s / 16 s spill structure Beam 190 Ge. V/c; ~108 μ/s • Targets: 1. 6 – (2+1) - 3 mm Pb , 7 mm Cu, 23 mm C Targets • Triggers: • Primakoff 1 = Hodoscope hit x ECal 2 (E>50 Ge. V) x HCal 2 (E>18 Ge. V) • Primakoff 2 = ECal 2 (E>100 Ge. V) • Saturated trigger rate (40 -50 k/spill)
THE RICH DETECTOR 3 m 6 m 5 m photon detectors C 4 F 10 • radiator gas: C 4 F 10 20 m 2 surface • mirror wall: • photon-detectors: • outer part (75%) MWPC(pad RO) with Cs. I cathode • inner part(25%) 576 MAPMTs with indiv. telescope threshold momenta ● p = 2 Ge. V/c ● p = 9 Ge. V/c K ● p =17 Ge. V/c P Installed in 2005, Used in data taking from 2006
The Compass Spectrometer
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