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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

Status of J-PARC K1.8 Beam Line

Kiyoshi Tanida

Department of Physics and Astronomy, Seoul National University

HNP2011, POSTECHFeb. 24, 2011

j parc japan proton accelerator research complex

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

j parc hadron hall

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

slide9

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)

slide10

K1.8 beamline

Apr, 2010

sks spectrometer

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
brief history status
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)
beam conditions
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-

beam microstructure
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
e19 experiment
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? ...
h igh resolution search why
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

p p k q reaction kek ps e522
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
actual run in oct nov
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
test data p p k s
Test data: p(p-,K+)S-
  • Good mass resolution: 1.9 MeV (FWHM) achieved
  • Cross section OK
  • Good performanceconfirmed
preliminary result
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
summary
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
future prospects
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!