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Status of J-PARC K1.8 Beam Line

Status of J-PARC K1.8 Beam Line. Kiyoshi Tanida Department of Physics and Astronomy, Seoul National University HNP2011 , POSTECH Feb. 24, 2011. J-PARC: W here is it?. Tokai, Japan. 50 GeV Synchrotron (15 m A). Material and Biological Science Facility. 3 GeV Synchrotron (333 m A).

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Status of J-PARC K1.8 Beam Line

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  1. Status of J-PARC K1.8 Beam Line Kiyoshi Tanida Department of Physics and Astronomy, Seoul National University HNP2011, POSTECHFeb. 24, 2011

  2. J-PARC: Where is it?

  3. Tokai, Japan 50 GeV Synchrotron (15 mA) Material and Biological Science Facility 3 GeV Synchrotron (333 mA) 400 MeV Linac (350m) Neutrino Facility J-PARC (Japan Proton Accelerator Research Complex) World-highest beam intensity : ~1 MW x10 of BNL-AGS, x100 of KEK-PS

  4. Nuclear & Hadron Physics in J-PARC

  5. Strangeness nuclear physics at K1.8BR and K1.8 approved /proposed (incl. LOI) J-PARC Hadron Hall g spectroscopy of L hypernuclei n-rich Lhypernuclei X hypernuclei LLhypernuclei X-atomic X rays Q+ search Weak decays of L hypernuclei • K- nucleus bound states Pion double charge exchange • nucleus • YN scattering Beam Dump K1.8 K- nucleus bound states K- atomic X rays h nucleus f nucleus • Hyperon resonances Handron Hall K1.8BR High Mom. Line Hadron mass in nuclei Nucleon quark structure meson structure KL K1.1 • Production • target (T1) Q+ study g spectroscopy of Lhyp. S hypernuclei Q+ hypernuclei K1.1BR 30~50 GeV primary beam

  6. June, 2007

  7. June, 2007

  8. Dec, 2008

  9. K1.8beamline Beam analyzer Double stage E.S. Separators (dp/p~10-4) MS2(V) Design of K1.8 beam line MS1(Vertical Slit) Mom(Horizontal slit) IFV(V) IFV(H)

  10. K1.8 beamline Apr, 2010

  11. 2.7T(395A) ~1.5T SKS Spectrometer • High resolution: • dp/p ~0.1% • Mass resolution: ~ 2 MeV (FWHM) • Large acceptance • 100 msr, up to ~1GeV/c • Variations for high mom. • SKS-Plus Keeping resolution • SKS-Minus Keeping acceptance

  12. Brief History & Status • Construction completed in July 2009 • First beam in September • Beam Line commissioning with intermittent beam time • Concurrent with accelerator commissioning • All components were found to work well • Beam intensity and structure is the current issue • First Physics beam time in Nov. 2010 • E19 experiment (Q+ search)

  13. Beam Conditions • Beam intensity: ～3.5 x 1012 protons per 6 second cycle • ~1% of the design. Still, higher than KEK-PS • x3 intensity demonstrated • Pion intensity: > 107/s possible. Limited by detectors. • Kaon is clearlyseen • Purity is to beimproved(low sep.voltage) • # of K-~25 k/cycle consistent π- K-/π- ratio ~ 0.14 Preliminary K-

  14. Beam microstructure • Instantaneous intensity >> average intensity • Limiting the available intensity due to detector pileup • We ran at 1.1 Mp/spill (2.2s)  Instantaneous rate: ~10 MHz • Gradually improving

  15. E19 Experiment Mysteries about Pentaquark, Q+ • Does it really exist? • Confirmation with good sensitivity is crucial • Width? Why so narrow? • Certainly < 1MeV • No bump in K+nK+n, K0p • Spin & parity? • 1/2+? 3/2+? 1/2-? ... • Its nature? • KN? KpN? ...

  16. High resolution search. Why? • For good S/N ratio • Q+ is above KN threshold, and is NEVER BG free • High resolution really helps to achieve good S/N ratio crucial for good sensitivity • Width measurement • Almost certainly, < 1 MeV • Similar or better resolution necessary! • Typical resolution so far ~ 10 MeV • No high resolution search • There is a good chance for high resolution experiments.  Missing mass spectroscopy

  17. p(p-,K-)Q reaction:KEK-PS E522 • Miwa et al.PLB635 (2006) 72. • Poor resolution ~13 MeV (FWHM) • Low statistics: < 1010p- on target • Still, there was a hint of peak: 1.9 mb/sr 2.5s significance •  Statistics: x100 Resolution: x1/5

  18. Actual Run in Oct./Nov. • Beam time: 156 hours • +116 hours for commissioning and calibration • Total statistics: 7.8 x 1010pions on target • ~5% of the proposal

  19. Test data: p(p-,K+)S- • Good mass resolution: 1.9 MeV (FWHM) achieved • Cross section OK • Good performanceconfirmed

  20. Preliminary result • No peak • Upper limit for a peak ~0.4 mb/sr (very preliminary)c.f. 3.9 mb/sr in E522  “hint” ruled out

  21. Summary • Physics experiment in K1.8 beam line has just started! • All detectors are working very well. • Beam intensity & structure is the current issue • Intensity: ~1% of design, still enough for pions • Structure limits the available intensity to ~1 MHz • Improving with efforts of accelerator group • E19: Q+ search in p(p-,K-) reaction • Detector performances are very good • No peak observed • Upper limit ~0.4 mb/sr Ruled out the “hint” in previous KEK-PS E522 spectrum • We will take more data in the coming runs

  22. Future prospects • The next beam time is scheduled in Apr. 2011 • We will continue to run E19 and E27 • Improvement of beam structure expected • Another beam time expected in autumn 2011 • Beam intensity: 1 x 1013/cycle (3% of design) expected • E10, E13 (E19) will run, and E05 will take pilot data. • More exciting experiments are waiting!

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