j-parc: where is it? j-parc (japan proton accelerator research complex) tokai, japan 50 gev...
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Status of J-PARC K1.8 Beam Line
Kiyoshi TanidaDepartment of Physics and Astronomy,
Seoul National UniversityHNP2011, POSTECH
Feb. 24, 2011
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J-PARC: Where is it?
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J-PARC (Japan Proton Accelerator Research Complex)
J-PARC (Japan Proton Accelerator Research Complex)
Tokai, JapanTokai, Japan
50 GeV Synchrotron (15 mA)
400 MeV Linac (350m)
3 GeV Synchrotron (333 mA)
Material and Biological Science Facility
World-highest beam intensity : ~1 MW x10 of BNL-AGS, x100 of KEK-PS
Neutrino Facility
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Nuclear & Hadron Physics in J-PARC
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J-PARC Hadron Hall
Handron Hall
Beam Dump
K1.8
K1.8BR
K1.1
K1.1BR 30~50 GeV primary beam
Productiontarget (T1)
Strangeness nuclear physics at K1.8BR and K1.8
g spectroscopy of L hypernuclei
n-rich L hypernucleiX hypernuclei
LL hypernucleiX-atomic X raysQ+ searchWeak decays of L hypernucleiK- nucleus bound statesPion double charge exchangew nucleusYN scattering
K- nucleus bound statesK- atomic X raysh nucleusf nucleusHyperon resonances
approved / proposed (incl. LOI)
High Mom. Line
Q+ studyg spectroscopy of L hyp.S hypernucleiQ+ hypernuclei
KLHadron mass in nucleiNucleon quark structuremeson structure
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June, 2007
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June, 2007
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Dec, 2008
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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-9mA2.0E+14
Length (m) 45.853
Acceptance (msr.%) 1.4
K-( ) p intensity (ppp) @1.8 GeV/c 1.4E+06
@1.5 GeV/c 0.54E+06
@1.1 GeV/c 0.08E+06
Electrostatic separators 750kV/10cm, 6m×2
Single rate @ MS2 @ 1.8 GeV/c > 8E+06
K-/(p-+m- ) @ FF @ 1.8 GeV/c 3.5
X/Y(rms) size @ FF (mm) 19.8/3.2
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Apr, 2010K1.8 beamline
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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
2.7T(395A)
~1.5T
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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)
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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 be
improved(low sep.voltage)
• # of K-
~25 k/cycle consistent
K-/π- ratio ~ 0.14
π-
K-
Preliminary
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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
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E19 ExperimentMysteries 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? ...
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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
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p(p-,K-)Q reaction: KEK-PS E522Miwa et al.PLB635 (2006) 72.
• Poor resolution ~13 MeV (FWHM)• Low statistics: < 1010 p- on target
• Still, there was a hint of peak: 1.9 mb/sr 2.5 s significance
Statistics: x100 Resolution: x1/5
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Actual Run in Oct./Nov.• Beam time: 156 hours
– +116 hours for commissioning and calibration
• Total statistics: 7.8 x 1010 pions on target– ~5% of the proposal
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Test data: p(p-,K+)S-
• Good mass resolution: 1.9 MeV (FWHM) achieved
• Cross section OK
• Good performanceconfirmed
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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
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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
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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!