Polarization analysis of antiprotons produced in pA collisions D. GRZONKA, FORSCHUNGSZENTRUM JÜLICH CERN/PS P349 D. Alfs , D. Grzonka, F. Hauenstein*, K. Kilian, IKP, Forschungszentrum Jülich, 52425 Jülich, Germany D. Lersch, J. Ritman, T. Sefzick B. Glowacz, P. Moskal, M. Zielinski IP, Jagiellonian University, ul. Reymonta 4, PL-30 -059 Krakow, Poland − − M. Diermaier, E. Widmann, J. Zmeskal SMI für subatomare Physik, Boltzmanngasse 3, 1090 Wien, Austria W. Oelert Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany M. Wolke Dep. of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden P. Nadel-Turonski Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 M. Carmignotto, T. Horn, PD, The Catholic University of America, 210 Hannan Hall, Washington, DC 20064 H. Mkrtchyan, A. Asaturyan, A. Mkrtchyan, A. I. Alikhanyan Science Laboratory (Yerevan Physics Institute), Yerevan 0036, Armenia V. Tadevosyan, S. Zhamkochyan S. Malbrunot-Ettenauer CERN, Physics department W. Eyrich, A. Zink PI, Universität Erlangen, Erwin-Rommel-Strasse 1, 91058 Erlangen, Germany *Present address: Old Dominion University, Norfolk, Virginia, USA MESON 2018, June 8th, 2018
Polarization analysis of antiprotons produced in pA collisions • Motivation − • Methods for polarized p beam production Λ -decay Spin-filter method − Polarization in p production ? • Measurement of polarization CNI region • P349 experiment • Status of the analysis Drift chamber calibration DIRC analysis • Summary and outlook � 2
Motivation Preparation of a polarized antiproton beam High Energy: nucleon quark structure : logitudinal momentum distribution f 1 (x) precise data helicity distribution DIS g 1 (x) transversity distribution h 1 (x) PAX collaboration, arXiv 0904.2325 [nucl-ex] (2009) polarized p Low Energy: spin degree of freedom → more detailed analyses possible antiprotonic atom e.g. : p p annihilation at rest possible states: spectroscopy 1 S 0 singlet high density target 3 S 1 triplet → stark mixing → S-wave � 3
Methods for Polarized p Beam Production many ideas → • hyperon decay , • spin filtering , mostly • spin flip processes, very low intensity • stochastic techniques, or low polarization • dynamic nuclear polarization, expected • spontaneous synchrotron radiation, or • induced synchrotron radiation, calculations impossible • interaction with polarized photons, and feasibility studies • Stern-Gerlach effect, require large effort. • channeling, • polarization of trapped antiprotons, •antihydrogen atoms, • polarization of produced antiprotons see e.g: A.D. Krisch, A.M.T. Lin and O. Chamberlain (edts), AIP Conf. Proc. 145 (1986) E. Steffens, AIP Conf.Proc 1008, 1-5 (2008), AIP Conf.Proc.1149, 80-89 (2009) H. O. Meyer, AIP Conf.Proc.1008, 124-131 (2008) � 4
Methods for Polarized p Beam Production Antihyperon decay Λ → p + π + ( 63,9 %) S p lab (p) S p π + p lab ( π + ) p cm Decay momentum in cm syst. is 101 MeV/c Decay makes p with helicity h = - 0.64. Lorentz boost creates transverse vector polarization. � 5
Methods for Polarized p Beam Production Antihyperon decay First and so far only experiment with polarized 200 GeV p at Fermilab. Λ production with primary 800 GeV/c proton beam. At the end an average of 10 4 polarized p s -1 with 0.45 polarization A. Bravar et al. Phys. Rev. Lett. 77 , 2626 (1996) being planned: SPACHARM project at U-70 IHEP (Protvino) Proton beam: 50 - 60 GeV/c, polarized antiproton beam: 15 - 45 GeV/c Intensity: (0.8 − 4.0) × 104 polarized p/cycle, polarization: 0.45 V. A. Okorokov et al., J.Phys.Conf.Ser. 938 (2017) no.1, 012014. I. I. Azhgirey et al., J. Phys.Conf. Ser. 798 (2017) 012177. � 6
Methods for Polarized p Beam Production proposed method for FAIR → PAX Spin filtering (PAX collaboration, arXiv 0904.2325 [nucl-ex] (2009) works in principle, protons at TSR and COSY (F. Rathmann et al., PRL 71, 1379 (1993)) (W. Augustyniak et al., PLB 718 64-69 (2012)) TSR COSY but enormous effort: to be confirmed for antiprotons ! separate filter storage ring (Sibirian snakes), filter time T ≃ 2 τ (beam life time) � 7
Methods for Polarized p Beam Production Polarization in p Production ? simplest method (if production polarized) Use the antiproton factory (nearly) as usual. proton y production beam target Cut one side in the horizontal angular distribution Cut up and down angles Avoid pure s wave antiprotons produced antiprotons in a certain scattering angle spin In addition avoid direction x depolarisation in the cooler synchrotron first step: check antiproton polarisation � 8
Measurement of Polarization CERN/PS testbeam east area • Production of p under useful conditions p momentum ≈ 3.5 GeV/c ( p production at AD and future FAIR facility) no s-wave production ( θ lab > 56 mrad) ⇨ T11: p momentum ≦ 3.5 GeV/c ( ≦ ± 5%) production angle = 150 mr (±3mrad h, ±10mrad v) • Measure transverse polarization via elastic p p scattering φ - distribution of the scattering of produced p in an analyzer target d σ /(d θ d φ ) = d σ /d θ ( 1 + A y * P * cos( φ ) ) determination of polarization P requires knowledge of A y ⇨ CNI region � 9
A y in the CNI Area d σ –– ∼ ⎪ φ 1 ⎪ 2 + ⎪ φ 2 ⎪ 2 + ⎪ φ 3 ⎪ 2 + ⎪ φ 4 ⎪ 2 + 4 ⎪ φ 5 ⎪ 2 1 – 1 – 1 – – 1 helicity frame: dt φ 1 (s,t) = ⟨ ⎪ φ ⎪ ⟩ , + + + + 2 2 2 2 d σ Ay –– = − Im [ ( φ 1 + φ 2 + φ 3 − φ 4 ) φ 5* ] 1 – 1 – – 1 – 1 + + φ 2 (s,t) = ⟨ ⎪ φ ⎪ ⟩ , − − dt 2 2 2 2 1 – 1 – – 1 1 – + − + − φ 3 (s,t) = ⟨ ⎪ φ ⎪ ⟩ , φ i = φ ihad + φ iem : 2 2 2 2 – 1 1 – 1 – 1 – + − − + φ 4 (s,t) = ⟨ ⎪ φ ⎪ ⟩ , d σ d σ d σ d σ 2 2 2 2 Ay –– = (Ay –– ) had + (Ay –– ) em + (Ay –– ) int dt dt dt dt 1 – – 1 1 – – 1 + + + − φ 5 (s,t) = ⟨ ⎪ φ ⎪ ⟩ . 2 2 2 2 interference of nuclear non-spin-flip and em spin-flip (due to magnetic moment) for small t and high energy: (N. Akchurin et al., Pys. Rev. D 48, 3026 (1993), and ref. cited.) A yem (t) = 0 (single photon exchange assumed) data for pp → pp, –– P p =100 GeV/c, A yhad (t) ≈ √ t/s (negligible for t/s → 0 ) ( √ s = 13.7 GeV) – 4 (t/t p ) 3/2 H. Okada et al., t p = √ 3 (8 πα / σ tot ) A yint (t) = A yint (t p ) –––––––––– 3 (t/t p ) 2 +1 PLB 638, ≈ -0.003 450 (2006). – – √ 3 √ t p (µ-1) –– ≈ 0.046 ( µ : magnetic moment ) A yint (t p ) ≈ –– 4 m A y ≈ 4.6 % , at t ≈ − 0.003 ⇒ - for pp and pp (G-parity) � 10
A y in the CNI Area A y data for pp → pp, H. Okada et al., PLB 638, 450 (2006). preliminary calculations for pp → pp (J. Haidenbauer, priv. comm.) Preliminary one-boson-exchange calculations NN potential, - - potential parameters determined by fit to experimental NbarN data, - data point for pp (Phys.Rev.D89,114003 (2014) at 185 GeV/c N. Akchurin et al., PLB 229, 299 (1989) -t / (GeV/c) 2 � 11
DIRC Drift- Drift- P349 Experiment (plexiglass) chamber chamber Start- scintillator lH 2 - 150 mrad target Beam 20 mrad (CNI) Scint. fiber Cherenkov hodoscope Stop Scintillator- (aerogel n=1.03) paddles ∼ 7m � 12
trigger: start ∧ stop ∧ (no Cherenkov-signal) P349 Experiment DIRC Drift- Drift- (plexiglass) chamber chamber Start- scintillator lH 2 - 150 mrad target Beam 20 mrad (CNI) Scint. fiber Cherenkov hodoscope Stop Scintillator- (aerogel n=1.03) paddles ∼ 7m P=1 GeV/c trigger time distribution spill rate check of 400 ms ∼ 30 s Cherenkov veto with p/ 𝜌 + separate datasets: black: data no Cherenkov veto → suppression red: Cherenkov veto on of pions P=3 GeV/c ∼ 1/30 trigger time in spill / ns Δ t (stop-start) � 13
Drift Chamber Calibration Status of the Analysis distance to track / cm Position ⇨ expected resolution ( 𝜏 ): track resolution: 150 - 300 𝛎 m < 1 mrad drift time / ns Poster: Drift chamber calibration and particle identification in the P-349 experiment Marcin Zieli ń ski � 14
Status of the Analysis Track Reconstruction 𝜘 N 35 2 2 χ χ / ndf / ndf 242.8 / 193 242.8 / 193 Constant Constant 23.07 23.07 0.68 0.68 ± ± DC3 1. selection of Mean Mean 0.6829 0.6829 0.1252 0.1252 ± ± 30 unscattered particles: Sigma Sigma 5.553 5.553 0.119 0.119 ± ± track fit including signals 25 of all 3 DC’s 20 DC2 2. reference track: 15 track fit from DC1 signals 10 target 3. determine track resolution: 5 track fit from DC1 DC2+DC3 signals 0 − 15 − 10 − 5 0 5 10 15 angle difference 𝜘 (DC1-track - DC2/DC3-track) / mrad track resolution: ∼ 5 mrad ⇨ optimize calibration and DC positioning � 15
Status of the Analysis DC Positioning DC3 is shifted/rotated relative to DC2 determine mean 𝜓 2 for track fit as a function of shift 𝜓 2 y-shift 𝜓 2 𝜓 2 y-rot. z-shift shift / cm 𝜓 2 z-rot. 𝜓 2 x-shift shift / cm rotation angle / deg 𝜓 2 rotation angle / deg shift / cm x-rot. track reconstruction precision su ffi cient for positioning rotation angle / deg � 16
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