Facilities and Detectors for Baryon Physics

Transcription

1 Facilities and Detectors for Baryon Physics Volker Credé Florida State University Tallahassee, FL APS-DNP Town Meeting Rutgers University, 1/14/27

2 Outline Introduction 1 Introduction 2 Crystal Ball 3 4

3 Outline Introduction 1 Introduction 2 Crystal Ball 3 4

4 E γ [GeV] W [GeV] 3, 2.6 Reaction Thresholds 2.6* γp pηη γp pπ ω γp pπ η γp pη γp pπππ γp pππ γp pπ 2, γp KΛ KΣ 1, 1.9., ELSA CLAS LEPS MAMI-C

5 E γ [GeV] W [GeV] 3, 2.6 Reaction Thresholds 2.6* γp pηη γp pπ ω γp pπ η γp pη γp pπππ γp pππ γp pπ 2, γp KΛ KΣ 1, Facilities are all complementary 2 International collaborations crucial., ELSA CLAS LEPS MAMI-C

6 Outline Introduction 1 Introduction 2 Crystal Ball 3 4

7 LEPS at SPring-8: Hyogo, Japan LEPS (international) Collaboration Japan South Korea Taiwan Canada U. S. (Ohio University)

8 LEPS at SPring-8: Hyogo, Japan Detector optimized for charged-particle final states Linear Polarization (Compton Backscattering) E γ < 2.4 GeV (new laser will allow E γ < 3 GeV) LEPS covers very forward angles (θ lab > 1 ) LEPS (international) Collaboration Japan South Korea Taiwan Canada U. S. (Ohio University)

9 LEPS at SPring-8: Hyogo, Japan Original detector optimized for K detection Diffractive φ-meson Photoproduction on the Proton near Threshold (a) (b) dσ/dt(t=- t min ) (µb/gev 2 ) 2 1 SLAC(1973) BONN(1974) DESY(1978) DARESBURY(1982) SAPHIR(23) This work W < E γ < < E γ < < E γ < < E γ < πW E γ (GeV) cosθ π 2π φ-φ

10 LEPS at SPring-8: Hyogo, Japan Original detector optimized for K detection Diffractive φ-meson Photoproduction on the Proton near Threshold γn K + Σ : Differential Cross Section/Photon Beam Asymmetry

11 LEPS at SPring-8: Hyogo, Japan Original detector optimized for K detection Diffractive φ-meson Photoproduction on the Proton near Threshold γn K + Σ : Differential Cross Section/Photon Beam Asymmetry Beam Polarization Asymmetries for γp K + Λ and γp K + Σ (kn v -N h )/(kn v +N h ) (kn v -N h )/(kn v +N h ) φ + K (rad) φ + K (rad)

12 Crystal Ball at MAMI-C: Mainz, Germany A2 (international) Collaboration Germany U. S. (GWU, UCLA, Kent State) Great Britain Belgium Italy Sweden Russia Croatia Switzerland Canada

13 Crystal Ball at MAMI-C: Mainz, Germany Optimized for neutral-particle final states 4π Calorimeter (Crystal Ball + TAPS) First-Level Trigger

14 Crystal Ball at MAMI-C: Mainz, Germany Optimized for neutral-particle final states 4π Calorimeter (Crystal Ball + TAPS) First-Level Trigger Charged-Particle Detection (MWPC)

15 Crystal Ball at MAMI-C: Mainz, Germany Optimized for neutral-particle final states 4π Calorimeter (Crystal Ball + TAPS) First-Level Trigger Charged-Particle Detection (MWPC) Polarized Beam and Target E γ < 1.5 GeV (W < 1.9 GeV)

16 Crystal Ball at MAMI-C: Physics Goals Focus on Measurements of total (σ) and differential cross sections ( dσ dω ) using unpolarized neutrons (LD 2): γn n π γn n η γn n η γn KΛ Single- and double-polarization measurements with polarized deuterium target

17 Crystal Barrel at ELSA: Bonn, Germany CB-ELSA Collaboration Germany Russia Switzerland U. S. (Florida State)

18 Crystal Barrel at ELSA: Bonn, Germany Optimized for neutral-particle final states 4π Calorimeter (Crystal Barrel + TAPS) Linear/Circular Beam Polarization Frozen-Spin (Butanol) Target E γ < 3 GeV (W < 2.6 GeV) CB-ELSA Collaboration Germany Russia Switzerland U. S. (Florida State)

19 Neutral-Meson Final States: Available Data from ELSA σ tot [µb] E γ [GeV] γp pπ Crystal ELSA (2/21) γp pπ (PRL D94, 123 (25)) γp pη (PRL D94, 124 (25)) 1 [µb] σ tot W [GeV] - 1/2 E γ [GeV] γp pη + 3/2-5/2 ρ-ω W [GeV]

20 Neutral-Meson Final States: Available Data from ELSA σ tot [µb] E γ [GeV] γp pπ Crystal ELSA (2/21) γp pπ (PRL D94, 123 (25)) γp pη (PRL D94, 124 (25)) γp pπ η (π π ) Strong indication for new states [µb] σ tot W [GeV] - 1/2 E γ [GeV] /2 γp pη - 5/2 ρ-ω W [GeV] 1 Preliminary Baryon Decays into pπ π N / resonances not coupling to Nπ or γn could be produced in such decay cascades m(pπ )

21 Neutral-Meson Final States: Available Data from ELSA σ tot [µb] E γ [GeV] [µb] σ tot W [GeV] - 1/2 E γ [GeV] /2 γp pπ γp pη - 5/2 Crystal ELSA (2/21) γp pπ (PRL D94, 123 (25)) µb ] σ [ γp pη (PRL D94, 124 (25)) γp pπ η (π π ) Strong indication for new states Total cross sections with 2 MeV bin size γp pπ η (exp) γp pπ η (pwa) γp pπ π γp pπ π (GRAAL) Preliminary σ π π σ π η ρ-ω W [GeV] s [ MeV ]

22 Neutral-Meson Final States: Available Data from ELSA σ tot [µb] E γ [GeV] [µb] σ tot W [GeV] - 1/2 E γ [GeV] /2 γp pπ γp pη - 5/2 ρ-ω W [GeV] Crystal ELSA (2/21) γp pπ (PRL D94, 123 (25)) γp pη (PRL D94, 124 (25)) γp pπ η (π π ) Strong indication for new states ELSA (22/23) Factor of 1 more unpolarized data and (almost) full angular coverage Linear photon polarization Cross sections, asymmetries, PWA Double-Polarization (27 ) Longitudinal Target Polarization

23 Outline Introduction 1 Introduction 2 Crystal Ball 3 4

24 Photoproduction of Neutral Mesons: e.g. γp pπ π General Advantage: γ does not couple to π Fewer Born-terms, t-channel exchanges

25 Photoproduction of Neutral Mesons: e.g. γp pπ π General Advantage: γ does not couple to π Fewer Born-terms, t-channel exchanges No diffractive ρ(77) production: ρ π π No direct ++ π production (Kroll-Ruderman term) 1.19 GeV < E γ < 1.26 GeV Arbitrary Units 2 1 Entries 7937 Arbitrary Units 2 Entries 7937 m π + π m pπ GeV < E γ < 1.26 GeV m ππ [GeV] GeV < E γ < 1.26 GeV m pπ [GeV] Saphir

26 Photoproduction of Neutral Mesons: e.g. γp pπ π General Advantage: γ does not couple to π Fewer Born-terms, t-channel exchanges No diffractive ρ(77) production: ρ π π No direct ++ π production (Kroll-Ruderman term) 1.92 GeV < E γ < 2.3 GeV Arbitrary Units 5 Entries 3738 Arbitrary Units 5 25 Entries 3738 m π + π m pπ GeV < E γ < 2.3 GeV m ππ [GeV] GeV < E γ < 2.3 GeV m pπ [GeV] Saphir

27 Photoproduction of Neutral Mesons: e.g. γp pπ π General Advantage: γ does not couple to π Fewer Born-terms, t-channel exchanges No diffractive ρ(77) production: ρ π π No direct ++ π production (Kroll-Ruderman term) Bigger contribution of resonant amplitudes! Arbitrary Units 5 Entries 3738 Arbitrary Units 5 25 Entries 3738 m π + π m pπ GeV < E γ < 2.3 GeV m ππ [GeV] GeV < E γ < 2.3 GeV m pπ [GeV] Saphir

28 γp pπ π and γp pπ + π from CB-ELSA and CLAS - CB-ELSA: - CLAS: 15 m(pπ π ): 2-22 MeV 7 6 m(pπ + π - ): 2-22 MeV γp N / Xπ X = (1232) X = D 13 (152) X = X(166) m(pπ ) m(pπ π ): MeV m(pπ ) m(pπ - ) m(pπ + π - ) >22 MeV m(pπ - ) Similar resonance structures in both data sets! m(pπ + π ): 2 22 MeV ρ(77) m(π + π ) γp pρ

29 Baryon Spectroscopy at BES: J/ψ pπ n ( pπ + n ) N (144)? N (152) N (1535) N (165) N (1675) N (168)? Possible new state M = 265 ± MeV/c2 Γ = 175 ± 12 ± 4 MeV/c 2 Prel. PWA favors (hep-ex/453)

30 Outline Introduction 1 Introduction 2 Crystal Ball 3 4

31 Introduction European and Asian facilities/detectors important (complementary to CLAS) Crystal Ball (A2 Collaboration) Crystal Barrel (CB-ELSA Collaboration) 1 Neutral final states 2 Beam/target polarization SPring-8 (LEPS Collaboration) Charged-particle final states (very forward direction) Polarized photon beam (Compton Backscattering)