J-PARC: Where is it?

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

Nuclear & Hadron Physics in J-PARC

J-PARC Hadron Hall Handron Hall Beam Dump K1.8 K1.8BR K1.1 K1.1BR 30~50 GeV primary beam Production target (T1) Strangeness nuclear physics at K1.8BR and K1.8  spectroscopy of  hypernuclei n-rich   hypernuclei  hypernuclei   hypernuclei  -atomic X rays   search Weak decays of  hypernuclei K - nucleus bound states Pion double charge exchange  nucleus YN scattering K - nucleus bound states K - atomic X rays  nucleus  nucleus Hyperon resonances approved / proposed (incl. LOI) High Mom. Line   study  spectroscopy of  hyp.  hypernuclei   hypernuclei KL Hadron mass in nuclei Nucleon quark structure meson structure

June, 2007

Dec, 2008

K1.8 Beam Line High intensity: 1.4x10 6 K  /spill (Phase-1) High purity: K  /   ~6.9 Proton beam 30GeV-9  A 1.8 GeV/c K  beam

K1.8 beamline Design of K1.8 beam line Double stage E.S. Separators MS2(V) MS1(Vertical Slit) Mom(Horizontal slit) IFV(V) IFV(H) Beam analyzer (dp/p~10 -4 ) Primary proton beam (protons/spill) 30 GeV-9  A 2.0E+14 Length (m) Acceptance (msr.%)1.4 K  (  intensity GeV/c GeV/c0.08E+06 Electrostatic separators750kV/10cm, 6m×2 Single rate 1.8 GeV/c ＞ 8E+06 K  /(   +   1.8 GeV/c 3.5 X/Y(rms) FF (mm)19.8/3.2

Apr, 2010 K1.8 beamline

SKS Spectrometer High resolution: –  p/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 2.7T(395A) ~1.5T

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 – E19 experiment (   search)

Beam Conditions Beam intensity: ～ 3.5 x protons per 6 second cycle – ~1% of the design. Still, higher than KEK-PS – x3 intensity demonstrated – Pion intensity: > 10 7 /s possible. Limited by detectors. Kaon is clearly seen – Purity is to be improved (low sep. voltage) # of K - ~25 k/cycle  consistent K - /π - ratio ~ 0.14 π-π- K-K- Preliminary

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

E19 Experiment Mysteries about Pentaquark,   Does it really exist? – Confirmation with good sensitivity is crucial Width? Why so narrow? – Certainly < 1MeV – No bump in K + n  K + n, K 0 p Spin & parity? – 1/2 + ? 3/2 + ? 1/2 - ?... Its nature? – KN? K  N?...

High resolution search. Why? For good S/N ratio –   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

p(  ,K  )  reaction: KEK-PS E522 Miwa et al. PLB635 (2006) 72. Poor resolution ~13 MeV (FWHM) Low statistics: <   on target Still, there was a hint of peak: 1.9  b/sr 2.5  significance  Statistics: x100 Resolution: x1/5

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

Test data: p(  ,K  )   Good mass resolution: 1.9 MeV (FWHM) achieved Cross section OK Good performance confirmed

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

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:   search in p(  ,K  ) reaction – Detector performances are very good – No peak observed – Upper limit ~0.4  b/sr  Ruled out the “hint” in previous KEK-PS E522 spectrum – We will take more data in the coming runs

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