1 / 40

Experiments on X -Nucleus interaction at J-PARC

Experiments on X -Nucleus interaction at J-PARC. Kiyoshi Tanida (Seoul National Univ./JAEA) 13 Dec. 2013 International Workshop on Strangeness Nuclear Physics Xiamen, China. Hyper-nuclear chart. Unexplored world of S=-2. Physics Motivation for S=-2 world.

adin
Download Presentation

Experiments on X -Nucleus interaction at J-PARC

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Experiments on X-Nucleusinteraction at J-PARC Kiyoshi Tanida(Seoul National Univ./JAEA) 13 Dec. 2013 International Workshop on Strangeness Nuclear Physics Xiamen, China

  2. Hyper-nuclear chart Unexplored world of S=-2

  3. Physics Motivation for S=-2 world • A doorway to the multi-strangeness system • Very dynamic system? • Large baryon mixing? Inversely proportional tomass difference. • H dibaryon as a mixed state of LL-XN-SS? • Little is known so far Main motivation of J-PARC

  4. Importance of X systems • Valuable information on XN (effective) interaction • e.g., How strong XN  LL (and thus XN-LL mixing) is? • Relevant to the existence of H dibaryon • XN component in LL-hypernuclei • How about A dependence? • One-meson exchange models predict significant A dependence. • In contrast to small A dependence in normal and L nuclei. • Impact on neutron stars • Does X- play significant role in neutron stars because of its negative charge? • Need to know the XA interaction and its A dependence. • S- was supposed to be important, but its interaction with neutron matter is found to be strongly repulsive.

  5. XN interaction model and XA optical potential (examples) • One boson exchange (NHC-D, Ehime) • strong attraction in odd states  strong A dependence • ESC04d* • strong attraction in 3S1（T=0）

  6. Quark cluster model potential • Example:Kyoto-Niigata/fss2+ G-matrix • Potential shape isnon-trivial, but overallrather weak. • Integral is almost 0

  7. Experimental information • X nuclei in emulsion • V=24±4 MeV?? [C.B. Dover, A.Gal, Ann. Phys. 146 (1989) 309.] • Formation is not guaranteed experimentally, rather doubtful • 12C(K-,K+) reactions • Two experiments, KEK-PS E224 & BNL-AGS E885 • Both shows significant events in the X bound region, after considering the effect of poor experimental resolution AGS E885

  8. Naïve Interpretation • Simple model • Rigid 11B core + X- core excitation is ignored • Woods-Saxon potential with negligible width V=-14~-16 MeV??

  9. Problems (1) • Core excitation • Cross-sections of ground/excited states depend strongly on XN interaction detail If excited states dominate, underestimation results. Sugimoto & Motoba Ehime potential(weak)

  10. Problems (1) • Core excitation • Cross-sections of ground/excited states depend strongly on XN interaction detail If excited states dominate, underestimation results. Sugimoto & Motoba ESC04d potential(strong spin-spin force)

  11. Problems (2) • XNLL conversion • LL continuum can appear at the same energy as X states • Calculation by Kohno and Hashimoto E885 spectrum can be explained with V = 0 MeV (G = 4 MeV) V~-14 MeV is anoverestimation

  12. So, what can we say? • XA potential is still quite a lot uncertain • V~-14 MeV can be underestimate or overestimate • X bound state vsLLcontinuum • Shallower real part ⇔ Larger imaginary part (actual balance is model dependent) LL continuum G (or W) both 4 MeV X bound state -V 14 MeV

  13. How can we distinguish? • If X bound states are dominant • Weak XN-LL coupling • Small imaginary part • These states must be rather narrow (G < 4 MeV) Distinct peaks may be observed • LL continuum dominant • Spectrum would be rather structureless High resolution spectroscopy

  14. E05 X-hypernuclei • Missing mass spectroscopy of 12C(K-,K+)X • 12XBe, 12LLBe 1.8 GeV/c K- beam high intensity 1.4x106 K- /spill (Phase-1) high purityK-/p- ~6.9 Proton beam 30GeV-9mA

  15. ~30msr 2.7T(395A) ~1.5T SksPlus Spectrometer PK+ ~1.3 GeV/c Dp/p=0.12% • 95°total bend • ~7m flight path • Dx=0.3 mm (RMS) high resolution：　DE~ 3 MeV

  16. Expected 12XBe Spectrum VX= -20MeV p X DE = 3 MeVFWHM 1 monthdata taking [counts/0.5MeV] s X Optical potential VX= -14MeV -BX [MeV]

  17. Even higher resolution Ex andG can be as small as 1 MeV Even higher resolution is desirable

  18. S-2S spectrometer • Under construction by grant-in-aid 2011-2015 • Large acceptance: 60 msr • Excellent resolution: Dp/p=0.05%  DM=1.5 MeV (FWHM) x2 more stat. & x2 better resolution than the originalplan! First data expected in 2016

  19. Fe target K- K+ X- X ray E03 X-ray spectroscopy of X atom • The first measurement of X rays from X-atom • Gives direct information on the XA optical potential • Produce X- by the Fe(K-,K+) reaction, make it stop in the target, and measure X rays. • Aiming at establishing the experimental method • Possibility for double-L hypernuclear g-ray

  20. Principle of the experiment • Atomic state – precisely calculable if there is no hadronic interaction • 1st order perturbation • If we assume potential shape,we can accurately determine its depth with only one data • Shape information can be obtained with many data • Even if 1st order perturbation is not good, this is still the same. • Peripheral, but direct  complementary information • Applicable regardless of potential type (repulsive, ...)

  21. X atom level scheme l=n-1 (circular state) X l=n-2 l=n-3 ... Energy (arbitrary scale) ... Z nuclear absorption ... X Z ... l (orbital angular momentum) X ray energy shift – real part Width, yield – imaginary part Successfully used for p-, K-,`p, and S-

  22. Experimental Setup • ＠K1.8 beamline • Long used at KEK-PS K2 beamline (E373, E522, ...) • Large acceptance (~0.2 sr) K- K+ 1.8 GeV/c 1.4x106/spill (4s)

  23. Choice of Target • Physics view: Batty et al. PRC59(1999)295 • For given state, there is optimal target • Nuclear absorption is reasonably small • X-ray energy shift and width are the largest (~a few keV) • They suggested 9F, 17Cl, 53I, and 82Pb for n=3,4,7,9. • The choice depends on the optical potential itself  We can’t know before the 1st experiment

  24. For the 1st experiment • We chose Fe (Iron) because of (mostly) experimental reason • Production rate: A-0.62 as cross section scales with A0.38 • Stopping probability: requires high target density (X- range: 10-20 g/cm2, bgct ~ 2cm) • X-ray absorption: significant at large Z  Small Z(A), yet high density • Koike calculated the energy shift (width) & yield of the Fe X ray (n=6  5) • Woods-Saxon potential: -24 - 3i MeV • Energy shift: 4.4 keV, width: 3.9 keV • Yield per stopped X-: 0.1 (~0.4 without absorption)

  25. X-ray detection • Hyperball-J • 32 Ge detectors • PWO anti-Compton • Detection efficiency • 16% at 286 keV • High-rate capability • < 50% deadtime • Calibration • In-beam, frequent • Accuracy ~ 0.05 keV • Resolution • ~2 keV (FWHM)

  26. Yield & sensitivity estimation • Total number of K-: 1.0x1012 for 100 shifts. • Yield of X • production:3.7×106 • stopped: 7.5×105 • X-ray yield：　2500 for n=65 transition • 7200 for n=76 • Expected sensitivity • Energy shift: ~0.05 keV (systematic dominant)  Good for expected shift (~1 keV, 4.4 keV by Koike ) < 5% accuracy for optical potential depth • Width: directly measurable down to ~ 1 keV • X-ray yield gives additional (indirect) information on absorption potential.

  27. Expected X-ray spectrum (1) n= 65 shift & width 0 keV

  28. Expected X-ray spectrum(2) n= 65 shift & width 4 keV

  29. Run Plan • Expected beam time: somewhere in 2015 after E07 • Primary beam intensity: ~ 50 kW (~20 % of design) • Present J-PARC intensity: ~ 24 kW (~9%) • Two step strategy • In the first beam time, only ~10% of statistics may be obtained. What can we do with that statistics? We can take rather good data

  30. Expectation with ~10% stat. (1) • Observation of X rays is certainly possible • 76 transition: 720 counts with 410 counts/keV BG Rather easy (but no physicsinformation)

  31. Expectation with ~10% stat. (2) • Can we see the 65 transition we are interested in? • Depends on absorption (width & yield) If the width is 0, it’s certainly possible

  32. Expectation with ~10% stat. (3) • Can we see the 65 transition we are interested in? • Depends on absorption (width & yield) If the width is 4 keV, (assumed in proposal) the peak is hardly seen

  33. Expectation with ~10% stat. (4) • Can we see the 65 transition we are interested in? • Depends on absorption (width & yield) If the width is ~1 keV, peak can be seen It may be more clearer because yield would be higher due to smaller absorption at the initial state Shift accuracy: 0.1~0.2 keV  enough for 1 keV shift

  34. Future Prospects（hope） • First experiment • Determine actual yield & background • Establish experimental method • Based on shift & width in iron, • If too small to be seen, use heavier target (Co, Ni) • If too large to be seen, use lighter target (Mn, Cr) • If we are lucky, take a few data points around, and then go to different mass region. • Final goal: a few points for each n • ~10 data points in total • Potential shape, A dependence. • At full intensity, it will take a few weeks/target • Gamma-ray spectroscopy of double L hypernuclei?

  35. Summary & perspective • S=-2 system is a main subject in J-PARC • Potential of X in nuclei is interesting with respect to XN interaction, XN-LL coupling, neutron star, etc. • However, present theories and experiments are not enough to determine the potential • Excited state  deeper potential • LL continuum  shallower potential w/ large absorption • High-resolution spectroscopy of X nuclei can distinguish those 2 scenarios  J-PARC E05 • X-ray spectroscopy of X atom provides complementary information  J-PARC E03

  36. Backup

More Related