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Thomas S. Bauer - NIKHEF PowerPoint Presentation
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Thomas S. Bauer - NIKHEF

Thomas S. Bauer - NIKHEF

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Thomas S. Bauer - NIKHEF

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  1. Thomas S. Bauer - NIKHEF Th. S. Bauer - NIKHEF

  2. Q Thomas S. Bauer - NIKHEF Th. S. Bauer - NIKHEF

  3. Qwith ?s • Some questions and critical remarks to • the recently reported exotic states: • + = { u u d d s } at 1.540 GeV and X- - = { u d d s s }at 1.862 GeV. Th. S. Bauer - NIKHEF

  4. Present experimental status • several experiments reporting positive results; • all reported signals are not very strong; • revisiting an intensively studied domain; • several critical remarks published; • possibly other origins of observed effects; Th. S. Bauer - NIKHEF

  5. Present experimental status • several experiments reporting positive results; • all reported signals are not very strong; • revisiting an intensively studied domain; • several critical remarks published; • possibly other origins of observed effects; • but : • no discussion of other results than mass and width; • (almost) no comparison with existing data; • no assessment of consistency of results; • experiments without result refrain to publish ... Th. S. Bauer - NIKHEF

  6. List of experiments: g g g e-scatt. (K+ + Xe) (p + A) (p + p) e-p scatt. • SPring-8 (Japan) hep-ex/0301020 08 Jul. 2003 • CLAS (TJLab) hep-ex/0307018 10 Dec. 2003 • SAPHIR (Bonn) hep-ex/0307083 30 Sep. 2003 • Hermes (HERA) hep-ex/0312044 22 Jan. 2004 • n-data(BEBC and Fermilab) hep-ex/0309042 25 Sep. 2003 • Diana (ITEP) hep-ex/0304040 18 Sep. 2003 • SVD-2 (Protvino) hep-ex/0401024 22 Jan. 2004 • NA49 (CERN) hep-ex/0310014 8 Oct. 2003 • ZEUS (HERA) ... WA89; Graal; H1; CoSy; Hera-B ... Th. S. Bauer - NIKHEF

  7. L and S resonances Q+ {uudds} decays to n K+ and to p K 0 Th. S. Bauer - NIKHEF

  8. X resonances X - - {ssddu} decays to X -p- Th. S. Bauer - NIKHEF

  9. SPring-8 Th. S. Bauer - NIKHEF

  10. SPring-8 (LEPS) ( g + 12C) Some salient features: • new experiment, optimized for f-physics *) ; • uses real photons from Synchr. Radiation Source; • Eg < 2.4 GeV; • LH2target and 12Ctarget - only 12C used; • PID through ToF and magnetic field; • recoiling protons via Si-strip detector; • correction for Fermi-motion. *) “new” = 2001. No printed publication except 2 conference contributions + PQ – paper. Th. S. Bauer - NIKHEF

  11. SPring-8 (LEPS) • first evidence for Q+-state; • produced in : • + n  Q+ + K-; Q+  K+ + n; used C-target; 19 events in peak. Th. S. Bauer - NIKHEF

  12. SPring-8 (LEPS) Particle Identification: magnetic field + Time of Flight ( + Cherenkov ) possible problem: 43 * 106 triggers 8000 events with K+ K-, final signal = 19 events need purity of10-6!! (including other cuts) Th. S. Bauer - NIKHEF

  13. SPring-8 (LEPS) A closer look at Fermi motion: • due tonucleartarget; • “correlated with Q-value”; • correction crucial for final result! • However • measured width of Q+  n K+ • much smaller than width of S !! • (20 MeV vs. 42 MeV) • by the way: shouldn’t the width rather • be correlated to momentum in cms ...? • which would make things worse. Th. S. Bauer - NIKHEF

  14. SPring-8 (LEPS) • Identification of Q+ state relies heavily on absence of (fast) proton: • the Si-strip detector is used as VETO -- • this relies crucially on (very) high efficiency.(no info on this found in the available SPRING-8 documents). (Questions: strip efficiency, coincidence between layers, etc.) • The Veto condition is checked at ± 45 mm around the presumed impact of the proton. • this requires knowledge of the complete kinematics – which is not available! Th. S. Bauer - NIKHEF

  15. SPring-8 (LEPS) (from Nakano et al.) Th. S. Bauer - NIKHEF

  16. SPring-8 (LEPS) Question: “removing” 5 events destroys peak. (from Nakano et al.) Th. S. Bauer - NIKHEF

  17. SPring-8 (LEPS) • Question: • “removing” 5 events destroys peak. • Thus: how can we gain trust in result ? • Answer: • Use data on LH2: • must be able to see Q+ p + K0s; • no problem with proton-veto ; • no problem with Fermi-motion. (from Nakano et al.) Note: SPring-8/LEPS can (in principle) trigger on pions of K0s decay. Th. S. Bauer - NIKHEF

  18. CLAS Th. S. Bauer - NIKHEF

  19. CLAS ( g + 2D, g + 1H ) Some salient features: • Large acceptance experiment, several years of operation; • domain: Baryon resonances; • Eg < 2.9 GeV and < 5 GeV , (respectively) • H2target and 2Dtarget ; • PID through ToF and magnetic field; • Correction for Fermi-motion (when needed). Th. S. Bauer - NIKHEF

  20. CLAS • attempt: analyze D-target data, assuming g + n Q+ + K- , Fermi correction treated as by SPring-8 collaboration: • Problem: “No statistical significant result obtained!” and “CLAS ... unfavorable... for direct Q+photoproduction detection” (Luminita Todor, Seminar@JLAB, Aug. 15, 2003) • --- how to proceed ??? Th. S. Bauer - NIKHEF

  21. CLAS • Goal: n + gQ+ + K-; • Problem: no free neutron target ; • apply trick : • use n in D-target; • require double scattering process to eject proton; • measurement kinematically complete Th. S. Bauer - NIKHEF

  22. CLAS • Prize for re-scattering: yield goes down (later called “quenching”) . (implicit claim CLAS:“~50 %”) • reported yields: f: 124 L1520 : 228 Q+: 42 Attention: difficult to compare: • acceptances not known, presumably not equal. • yield Q/yield L1520 ≈ 0.4 – probably even larger! • Need Monte Carlo in order to determine acceptance and cross section. Th. S. Bauer - NIKHEF

  23. CLAS -- new data • apparently not yet available, though shown at workshop in Trento, Febr. 12, 2004 • two peaks, at 1.528 and 1.578 GeV • yield of 1.578 GeV peak is ~2 times stronger Th. S. Bauer - NIKHEF

  24. SAPHIR Th. S. Bauer - NIKHEF

  25. SAPHIR (Elsa-Bonn) ( g + 1H ) • 133 M events (taken ~5 years ago) • trigger = 2 charged tracks • signal: ~ 50 events • corresponds to production cross section of s ~200 nb. this is “≈ 20 % of L, S and L1520 cross sections” “rising with energy” – and decreasingwith time . Th. S. Bauer - NIKHEF

  26. X-- another member of the anti-decuplet... X- - = { u d d s s }. Q+ = { u u d d s } Th. S. Bauer - NIKHEF

  27. NA49 Th. S. Bauer - NIKHEF

  28. NA49 (p-p, √ s = 17 GeV) • p-p scattering at √ s = 17 GeV • signals for X-- : • combining X- and p- • cross check with other charge combinations. • can use X0*1530 as benchmark. Th. S. Bauer - NIKHEF

  29. NA49 Remarks: • opening angle Qlab > 4.5 º Th. S. Bauer - NIKHEF

  30. NA49 Remarks: • opening angle Qlab > 4.5 º • Qlabis not a physical parameter !!! Th. S. Bauer - NIKHEF

  31. NA49 Remarks: • opening angle Qlab > 4.5 º • Qlabis not a physical parameter !!! • X*01530 visible, but weaker than X--(1860) (due to some cuts... total X*01530 signal is ~150 evts.) Th. S. Bauer - NIKHEF

  32. NA49 versus NA49 • Criticism: (Thanks to H.G. Fischer and S. Wenig, CERN, hep-ex / 0401014 – 12 Jan 2004) • NA49 used 1640 X- and 551 X+ events • NA49 sees a total of ~ 150 X*01530 • S.N. Gangule et al.(NP. B128-408, (1977) report ~ 800 X*01530 from S.N. Gangule et al. Nucl.Phys. B128, 408, (1977) Th. S. Bauer - NIKHEF

  33. NA49 (p-p, √ s = 17 GeV) X-- Th. S. Bauer - NIKHEF

  34. NA49 versus (?) WA89 *) *) taken from Pochodzalla, Mainz, talk at JLab, Oct 2003 Th. S. Bauer - NIKHEF

  35. What is hidden beyond 1.8 GeV inWA89 ?? Note: 63 000 ± 6 000 X0* ? total: ~150 X0* Th. S. Bauer - NIKHEF

  36. NA49 Q+ nK+ what has NA49 to say about Q+ ? Th. S. Bauer - NIKHEF

  37. NA49 Q+ nK+ • nK+ inv. mass spectrum; • deviation from polynomial; Th. S. Bauer - NIKHEF

  38. NA49 Q+ nK+ • nK+ inv. mass spectrum; • deviation from polynomial; • 30 % of L1520 added as a hypothetical Q+ ; • statistical significance of added signal. • note: different E-scale! Th. S. Bauer - NIKHEF

  39. Hermes Th. S. Bauer - NIKHEF

  40. Hermes (e-A, Ee = 27 GeV) How stable is this signal? quoted signal: 54 ... 59 ± 16 Th. S. Bauer - NIKHEF

  41. Hermes (e-A, Ee = 27 GeV) First: one can do much more with 33 datapoints... Th. S. Bauer - NIKHEF

  42. Hermes (e-A, Ee = 27 GeV) 121 40 121 40 Th. S. Bauer - NIKHEF

  43. Hermes (e-A, Ee = 27 GeV) Th. S. Bauer - NIKHEF

  44. Hermes (e-A, Ee = 27 GeV) Th. S. Bauer - NIKHEF

  45. Hermes (e-A, Ee = 27 GeV) L-channel note: width L1670 small (25 ~ 50 MeV/c2) width L1690 small (50 ~ 70 MeV/c2) Th. S. Bauer - NIKHEF

  46. Hermes -- another regard on these data bckgrnd = 5 Gauss + mixing = 6 params signal = Gauss (3param) pretty superfluous!! total = 9 params bckgrnd = parabola (3 params) signal = Gauss (3param) total = 6 params  2/n = 0.64 bckgrnd = parabola (3 params) only total = 3 params  2/n = 1.097 most likely!! from Hermes publication: Th. S. Bauer - NIKHEF

  47. other work • R. A. Arndt, I.I. Strakovsky and R.L. Workman: (nucl-th/0311030, 10 Nov. 2003) • reexamine existing K+p and K+d database; • “how could such a state have been missed”? • “The lack of structure in database implies: • “ a width of an MeV or less , assuming a state exists near 1540 MeV.” Th. S. Bauer - NIKHEF

  48. Hera-B Th. S. Bauer - NIKHEF

  49. Hera-B (p-A, √ s = 42 GeV) K0 - p finally, a signal which one would like to believe... Th. S. Bauer - NIKHEF

  50. Hera-B (p-A, √ s = 42 GeV) finally a signal which we can enhance... Th. S. Bauer - NIKHEF