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Baryon Spectroscopy at Jlab and J-PARC

Baryon Spectroscopy at Jlab and J-PARC. K. Hicks (Ohio U.) Baryons2013 Conference 24 June 2013. Physics of broad & overlapping resonances . N* : 1440, 1520, 1535, 1650, 1675, 1680, ... D : 1600, 1620, 1700, 1750, 1900, …. Δ (1232). Width: a few hundred MeV.

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Baryon Spectroscopy at Jlab and J-PARC

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  1. Baryon Spectroscopy at Jlab and J-PARC K. Hicks (Ohio U.) Baryons2013 Conference 24 June 2013

  2. Physics of broad & overlapping resonances N* : 1440, 1520, 1535, 1650, 1675, 1680, ... D : 1600, 1620, 1700, 1750, 1900, … Δ (1232) • Width: a few hundred MeV. • Resonances are highly overlapped • in energy except D(1232). • →Complex PWA is necessary • Width: ~10 keV to ~10 MeV • Each resonance peak is clearly separated. From: H. Kamano, JAEA seminar

  3. S L=0 L=1 L=2 L=4 Decuplet Assignments (PDG) From p-scatt. database: all **** rated. Lots of missing states! Lack of K-scatt. data or photoproduction data.

  4. L=0 L=1 L=0 L=2 Octet Assignments (PDG) Mass hierarchy problem with L=1, S=3/2 !! Here, there are more assignments, but many have few-star ratings.

  5. Capstick & Roberts (1993) Even 20 years ago, this problem was known! (Note: just N PWA.)

  6. Experiment vs. Quark Model Source: PDG review

  7. Goals of this Physics • Understanding the spectrum of excited states of the nucleon leads to a deeper understanding of non-perturbative QCD. • Similarly, the spectrum of excited states of the hydrogen atom led to advances in QM. • My working hypothesis: • The constituent quark model is a failure for excited states of the nucleon. • Perhaps the reason is that the CQM does not include effects of the meson-baryon cloud.

  8. L(1405) Photoproduction at CLAS R. Schumacher, Thursday 9:00 talk If the L(1405) were a single 3-quark resonance, then all three decays should be symmetric. However, if the resonance is dynamically generated, interference of poles with different isospin can occur

  9. Drell-Yan: nucleon has pion cloud The Drell-Yan process measures the antiquark sea in the nucleon. From: P. Reimer, arXiv:0704.3621. The results show that there is an asymmetry to the u* and d* sea in the proton. The nucleon has an admixture of qqq(qqbar).

  10. NΔ Transition Form Factor (GM) from EBAC • One third of G*M at low Q2 is due to contributions from meson–baryon (MB) dressing: The area of Q2<7.0 GeV2 is far from pQCD domain Meson- Baryon Cloud Effect bare quark core In the relativistic QM framework, the bare-core contribution is well described by the three-quark component of the wavefunction at high Q2. B.Julia-Diaz et al., PRC 69, 035212 (2004)

  11. Physical N*s will be a “mixture” of the two pictures: meson cloud Resonance core baryon meson Dynamical Coupled-Channels model MB channels ppN pN->ppN Reaction Amplitude B* bare resonance core (from QM)

  12. Recent Lattice Calculations Reference: J. Dudek et al.,, arXiv:1201.2349 Note: Not real mass!

  13. Projection of N* to SLJ

  14. A Tale of Two Labs • Jefferson Lab and J-PARC share a common interest: to understand QCD. • The combination of high-quality hadronic data with double-polarization photoproduction data is more powerful than either one alone. • Of course, other labs also share this interest. • It is becoming clear that both hadronic and photoproduction data are needed due to coupled-channels effects that naturally link them together.

  15. P11(1440) couplings from CLAS N N Meson cloud effect Light front models: I. Aznauryan hybrid P11(1440) S. Capstick

  16. CLAS: e p → e' p +- The BLUE dotted curve uses only the known resonances from the Particle Data Group. The RED solid curve includes an extra resonance not seen from the PWA of N data alone.

  17. CLAS: Partial Wave Analysis A new P13 resonance, much lower in mass than the quark model prediction, is necessary to fit the data.

  18. Importance of N Decay

  19. What data do we need? • For almost 40 years, there have been no new measurements on (p,2p) in the nucleon resonance region. • For many years, elastic pN was good enough • With precise new data on gNpN, ppN at Jefferson Lab, Bonn and elsewhere, along with theory advances, it becomes clear that hadronic-beam data is also needed to properly interpret the photoproduction data.

  20. p-N Total Cross Sections

  21. ppN Total Cross Sections Kamano et al., PRC 79, 025206 (2009). Dashed line: no channel coupling.

  22. The Primary Source of (,2)

  23. Complete (p,2p) Database M. Manley, Phys. Rev. D 30, 904 (1984). Total number of events!

  24. Mass Projections Note: the normalization of these data is not known. The total cross sections were used to set the vertical scale. The solid curves are the full calculation using only pN elastic data. The other curves do not include some coupled-channels effects.

  25. PRELIMINARY PRELIMINARY F37 D33 F37 S31 S31 P33 F35 D33 P31 P33 D35 P31 F35 D35

  26. PRELIMINARY TCS TCS W W M(π0 p) M(π+ n) M(π+ p) Current model Refit F37 PWA keeping N*  πΔ off M(π+ π+) M(π+ π0)

  27. J-PARC Experiment

  28. K1.8 beamline with TPC

  29. Experimental SetupHyp-TPC Spectrometer Measure (p,2p) in large acceptance TPC p-p→p+p-n, p0p-p p+p→p0p+p, p+p+n p+- beam ~ 1M/spill (p=0.6-2.0 GeV/c) Liquid-proton target Trigger: Two charged particles in hodoscope Hodoscope p- beam Superconducting Helmholtz Dipole magnet Hyp-TPC

  30. Hyp-TPC 50φ 500φ • P-10 gas • H-target in TPC • Gating grid wires • 3-layer GEM • Good performance at high beam rates • Pad size • 2.5 x 9~13 mm : 30 layers • 5045 pads in total • p/K/p PID with dE/dx vs p P-10 gas Target holder E=180V/cm p+ ~600 ionization p- beam n p- B=1T Liquid H target Electron drift Gating Grid GEM Pad plane

  31. TPC prototype test results Charged particle Field wires Hit position distortion <0.1mm • Beam test at RCNP (Nov.2011) e Drift field 20cm Expected Dp/p= 1-3% (p,p) Position resolution (B=0) sx=0.40mm sy= 0.55mm

  32. Expected statistics Total (p,2p) cross section : ~2 mb Pion beam rate : ~106 (per 6 second spill) 5cm thick Liquid Hydrogen target TPC acceptance of 50% Result: 200 events / spill Energy coverage: W=1.50 – 2.15 GeV 26 energy bins(W=0.025) 20 angle bins 10K events / bin Result: 24M events in45 shifts (2 months)

  33. Status of R&D • TPC development • 1st prototype successful to confirm basic performance at high beam rate • Design for real size 2nd prototype going on with electronics development Other R&D specially for P45 • Liquid hydrogen target • to fit TPC target hole of ~ 5cm cylinder • Trigger hodoscopes • Optimize segmentation

  34. General Summary The N* spectrum is a long-standing problem. Today, we know that dynamical coupled-channels calculations are needed. → Coupled channels requires hadronic data. → Many N* states couple to 2 decay. My opinion: without quality (,2) data, it is difficult to see how the N* spectrum can be extractedwith PWA techniques.

  35. Backup slides

  36. Additional final state: KY data • Data for KL and KS come for free • Cross sections are smaller, but the final state is two-body, so less data are needed. • These final states have two charged particles and hence will be part of the trigger. • Data on p+p K+S+ are especially useful • Only isospin 3/2 contributes: D resonances. • Is the D(1600) the I=3/2 partner of the Roper?

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