Exotic atoms by the DIRAC experiment Mikhail Zhabitsky for the DIRAC - PowerPoint PPT Presentation

π ± K ∓ atoms Long-lived π + π − atoms Results and Outlook Exotic atoms by the DIRAC experiment Mikhail Zhabitsky for the DIRAC Collaboration (CERN PS-212) Joint Institute for Nuclear Research, Dubna CERN, the European Organization for Nuclear Research Kraków, MESON 2018 M Zhabitsky for DIRAC Exotic atoms by the DIRAC experiment

π ± K ∓ atoms Long-lived π + π − atoms Results and Outlook The DIRAC Collaboration 1998–2003 Lifetime measurement of π + π − -atoms ( A 2 π ) 2007–. . . Search for and lifetime measurement of π ± K ∓ -atoms ( A π K ) 68 physicists from Czechia, Italy, Japan, Romania, Russia, Spain and Switzerland Use double-arm spectrometer at CERN Proton Syncrotron (24 GeV / c ) M Zhabitsky for DIRAC Exotic atoms by the DIRAC experiment

π ± K ∓ atoms Long-lived π + π − atoms Results and Outlook Contents 1 π ± K ∓ atoms Theory and experimental method The DIRAC spectrometer First observation and lifetime measurement of π ± K ∓ atoms 2 Long-lived π + π − atoms Method to observe long-lived π + π − atoms First observation of long-lived π + π − atoms Long-lived π + π − atom lifetime 3 Results and Outlook M Zhabitsky for DIRAC Exotic atoms by the DIRAC experiment

π ± K ∓ atoms Theory and experimental method Long-lived π + π − atoms The DIRAC spectrometer First observation and lifetime measurement of π ± K ∓ atoms Results and Outlook π K atoms lifetime Hydrogen-like atoms, formed by π and K mesons, a B = 249 fm, p B = 0 . 79 MeV / c Lifetime is limited by charge-exchange process π + K − → π 0 ¯ π − K + → π 0 K 0 K 0 or τ = 8 1 � 2 � a 1 / 2 − a 3 / 2 9 α 3 µ 2 p ( 1 + δ K ) 0 0 [S.Bilenky et al., Sov. J. Nucl. Phys. 10 (1969) 469] [J. Schweizer, Phys. Lett. B 587 (2004) 33] SU(3) ChPT predictions [J. Bijnens et al. JHEP 0405 (2004) 036] : + Roy-Steiner equations [P.Büttiker et al., Eur. Phys. J. C33 (2004) 409] : τ = ( 3 . 5 ± 0 . 4 ) · 10 − 15 s M π a − 0 = 0 . 090 ± 0 . 005 , δ K = 0 . 040 ± 0 . 022 ⇒ 1 � � M π a − a 1 / 2 − a 3 / 2 0 = M π = 0 0 3 = 0 . 071 ( CA ) → 0 . 0793 ( 1 l ) → 0 . 089 ( 2 l ) → 0 . 090 ± 0 . 005 ( dis ) Recent Lattice QCD calculations M π a − 0 = 0 . 077 ± 0 . 001 + 0 . 002 [NPLQCD, Phys. Rev. D74 (2006) 114503] − 0 . 005 M π a − 0 = 0 . 081 ± 0 . 006 ± 0 . 012 [PACS-CS, Phys. Rev. D89 (2014) 054502] M π a − 0 = 0 . 0745 ± 0 . 00020 [T. Janowski et al., LATTICE2014] M Zhabitsky for DIRAC Exotic atoms by the DIRAC experiment

π ± K ∓ atoms Theory and experimental method Long-lived π + π − atoms The DIRAC spectrometer First observation and lifetime measurement of π ± K ∓ atoms Results and Outlook Experimental way to observe π K atoms Annihilation: A π K → π 0 K 0 or π 0 K 0 λ anh = βγτ ≈ 20 µ m at γ ≈ 20 Interaction of A π K with target atoms [L. Nemenov, Sov. J. Nucl. Phys. 41 (1985) 629] Excitation/de-excitation of A π K λ 1S int ≈ 40 µ m in Ni A π K ionization ⇒ characteristic “atomic” pairs π ± K ∓ ( n A ): � E + ≈ E − q CMS < 3 MeV / c ⇒ in laboratory frame Θ < 3 mrad Unique P ion = n A = P ion ( τ ) relation N A M Zhabitsky for DIRAC Exotic atoms by the DIRAC experiment

π ± K ∓ atoms Theory and experimental method Long-lived π + π − atoms The DIRAC spectrometer First observation and lifetime measurement of π ± K ∓ atoms Results and Outlook Experimental way to observe π K atoms Annihilation: A π K → π 0 K 0 or π 0 K 0 λ anh = βγτ ≈ 20 µ m at γ ≈ 20 Interaction of A π K with target atoms [L. Nemenov, Sov. J. Nucl. Phys. 41 (1985) 629] Excitation/de-excitation of A π K λ 1S int ≈ 40 µ m in Ni A π K ionization ⇒ characteristic “atomic” pairs π ± K ∓ ( n A ): � E + ≈ E − q CMS < 3 MeV / c ⇒ in laboratory frame Θ < 3 mrad Unique P ion = n A = P ion ( τ ) relation N A M Zhabitsky for DIRAC Exotic atoms by the DIRAC experiment

π ± K ∓ atoms Theory and experimental method Long-lived π + π − atoms The DIRAC spectrometer First observation and lifetime measurement of π ± K ∓ atoms Results and Outlook P ion = P ion ( τ ) A π K propagation in matter: annihilation/ionisation/excitation Total/excitation cross-sections in Born approximation br 0.5 P 0.45 [St. Mrowczynski, 1986, Phys. Rev. A33, 1549] 0.4 [L. Afanasyev, A. Tarasov, 1996, Sov. J. Nucl. Phys 59, 2130] 0.35 Glauber approximation + ionization cross-sections 0.3 [T. Heim et al., 2001, J. Phys. B34, 3763] 0.25 0.2 Multiphoton exchange 0.15 Density matrix formulas 0.1 [O. Voskresenskaya, 2003, J. Phys. B36, 3293] 0.05 0 2 4 6 8 10 12 14 16 18 20 τ , fs Direct calculation of P ion ( τ ) P ion ( τ ) better than 1% [M. Zhabitsky, 2008, Sov. J. Nucl. Phys 71, 1040] M Zhabitsky for DIRAC Exotic atoms by the DIRAC experiment

π ± K ∓ atoms Theory and experimental method Long-lived π + π − atoms The DIRAC spectrometer First observation and lifetime measurement of π ± K ∓ atoms Results and Outlook A π K generation p + Ni → . . . at 24 GeV / c Atoms are generated in nS -states | Ψ nS ( 0 ) | 2 ∝ 1 n 3 : 1 S : 83%, 2 S : 10%, . . . Other sources of inclusive π ± K ∓ -pairs: Coulomb pairs N A = kN C ( q < q 0 ) 4 πµ π K α/ q A C ( q ) = 1 − exp ( − 4 πµ π K α/ q ) Non-correlated pairs P ion = n A n A = N A kN C ⇒ P ion = P ion ( τ ) M Zhabitsky for DIRAC Exotic atoms by the DIRAC experiment

π ± K ∓ atoms Theory and experimental method Long-lived π + π − atoms The DIRAC spectrometer First observation and lifetime measurement of π ± K ∓ atoms Results and Outlook The DIRAC spectrometer σ p / p ≈ 3 · 10 − 3 Resolution in momentum Momentum range p π ∈ [ 1 . 2 , 2 . 5 ] GeV / c p K ∈ [ 4 . 0 , 8 . 9 ] GeV / c Rel. momentum resolution in c.m.s. σ Q x ≈ σ Q y ≈ 0 . 35 MeV / c σ Q L ≈ 0 . 9 MeV / c M Zhabitsky for DIRAC Exotic atoms by the DIRAC experiment

π ± K ∓ atoms Theory and experimental method Long-lived π + π − atoms The DIRAC spectrometer First observation and lifetime measurement of π ± K ∓ atoms Results and Outlook First observation π ± K ∓ atoms 0.8 Evidence for π K -atoms observation with DIRAC 0.7 [Adeva et al. (DIRAC Collaboration) Phys. Lett. B674 (2009) 11] 0.6 Thin Pt target 28 µ m, 2007: 0.5 n A ( π − K + + π + K − ) = 173 ± 54 Pbr 0.4 N A ( π − K + + π + K − ) = kN C = 280 ± 70 0.3 0.2 τ > 0 . 8 · 10 − 15 s (CL=0.9) 0.1 0 0 1 2 3 4 5 6 7 8 9 τ (fs) Further analysis of data collected on Pt and Ni targets: Observation of π K atoms [Adeva et al. (DIRAC Collaboration) Phys. Rev. Lett. 117, 112001 (2016)] n A = 349 ± 62 | tot ( 5 . 6 σ ) M Zhabitsky for DIRAC Exotic atoms by the DIRAC experiment

π ± K ∓ atoms Theory and experimental method Long-lived π + π − atoms The DIRAC spectrometer First observation and lifetime measurement of π ± K ∓ atoms Results and Outlook Lifetime measurement of π ± K ∓ atoms Two analysis: Q and ( | Q L | , Q T ) fits of experimental data: Pt (2007) ( π − K + & π + K − ) Ni (2008-2010) ( π − K + & π + K − ) M Zhabitsky for DIRAC Exotic atoms by the DIRAC experiment

π ± K ∓ atoms Theory and experimental method Long-lived π + π − atoms The DIRAC spectrometer First observation and lifetime measurement of π ± K ∓ atoms Results and Outlook Lifetime measurement of π ± K ∓ atoms (Q analyses) P br from Q -analyses ( Q T < 4 MeV / c ) Systematic uncertainties in Pt Atom Year s , µ m P br π K lab momenta 0.09 A π K 2007 Pt, 25.7 1 . 2 ± 1 . 3 Lab. mom. of bg pairs 0.22 A π K 2008 Ni, 98 0 . 53 ± 0 . 39 Total 0.24 2009 Ni, 108 0 . 29 ± 0 . 20 A π K Systematic uncertainties in Ni A π K 2010 Ni, 108 0 . 33 ± 0 . 22 Multiple scattering 0.0051 2007 Pt, 25.7 1 . 09 ± 0 . 52 A K π π K lab momenta 0.0052 A K π 2008 Ni, 98 0 . 32 ± 0 . 20 P br ( τ ) relation 0.0055 A K π 2009 Ni, 108 0 . 23 ± 0 . 16 Total 0.0092 2010 Ni, 108 0 . 41 ± 0 . 17 A K π M Zhabitsky for DIRAC Exotic atoms by the DIRAC experiment

π ± K ∓ atoms Theory and experimental method Long-lived π + π − atoms The DIRAC spectrometer First observation and lifetime measurement of π ± K ∓ atoms Results and Outlook A π K lifetime and π K scattering lengths ( Q analyses) 1 τ = 8 � 2 ( 1 + δ K ) 9 α 3 µ 2 p � a 1 / 2 − a 3 / 2 0 | m π = 1 � � � × 10 − 15 s � 5 . 5 + 5 . 0 | a − 3 | a 1 / 2 − a 3 / 2 | m π = 0 . 072 + 0 . 031 τ = ⇒ � � − 2 . 8 − 0 . 020 � � tot tot ( | Q L | , Q T analysis): 0 | m π = 1 � � � × 10 − 15 s � | a − 3 . 8 + 3 . 5 3 | a 1 / 2 − a 3 / 2 | m π = 0 . 087 + 0 . 044 τ = ⇒ � � − 2 . 1 − 0 . 024 � � tot tot [DIRAC Collaboration, Phys. Rev. D 96 , 052002 (2017)] M Zhabitsky for DIRAC Exotic atoms by the DIRAC experiment