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

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

3. Th. S. Bauer - NIKHEF  with ? s Some questions and critical remarks to the recently reported exotic states:  +  { u u d d s } at 1.540 GeV and  - - = { u d d s s } at 1.862 GeV.

4. Th. S. Bauer - NIKHEF 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;

5. Th. S. Bauer - NIKHEF 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 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...

6. Th. S. Bauer - NIKHEF List of experiments: 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  -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)...  e-scatt. (K + + Xe) (p + A) (p + p) e-p scatt. WA89; Graal; H1;H1; CoSy; Hera-B...

7. Th. S. Bauer - NIKHEF  and  resonances  + {uudds} decays to n  + and to p K 0

8. Th. S. Bauer - NIKHEF  resonances  - - {ssddu} decays to  -  -

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

10. Th. S. Bauer - NIKHEF SPring-8 (LEPS) (  + 12 C) Some salient features: new experiment, optimized for  -physics *) ; uses real photons from Synchr. Radiation Source; E  < 2.4 GeV; LH 2 target and 12 C target - only 12 C 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.

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

12. Th. S. Bauer - NIKHEF SPring-8 (LEPS) Particle Identification: magnetic field + Time of Flight ( + Cherenkov ) possible problem: 43 * 10 6 triggers 8000 events with K + K -, final signal = 19 events need purity of 10 -6 !! (including other cuts)

13. Th. S. Bauer - NIKHEF SPring-8 (LEPS) A closer look at Fermi motion: due to nuclear target ; “correlated with Q-value”; correction crucial for final result!   n  - n-n- n+n+ Q (MeV) 37120107  (MeV) <1042~20 p (cms) 104193244 However measured width of  +  n K + much smaller than width of  !!  ( 20 MeV vs. 42 MeV) by the way: shouldn’t the width rather be correlated to momentum in cms...? which would make things worse.

14. Th. S. Bauer - NIKHEF SPring-8 (LEPS) Identification of   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!

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

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

17. Th. S. Bauer - NIKHEF SPring-8 (LEPS) Question: “removing” 5 events destroys peak. Thus: how can we gain trust in result ? Answer: Use data on LH 2 : must be able to see  +  p + K 0 s ; no no problem with proton-veto ; no no problem with Fermi-motion. (from Nakano et al.) Note: SPring-8/LEPS can (in principle) trigger on pions of K 0 s decay.

18. Th. S. Bauer - NIKHEF CLAS

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

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

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

22. Th. S. Bauer - NIKHEF CLAS Prize for re-scattering: yield goes down (later called “quenching”). (implicit claim CLAS: “~50 %” ) reported yields:  : 124  1520 : 228  + : 42 Attention: difficult to compare: acceptances not known, presumably not equal. yield  / yield    ≈ 0.4 – probably even larger! Need Monte Carlo in order to determine acceptance and cross section.

23. Th. S. Bauer - NIKHEF 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

24. Th. S. Bauer - NIKHEF SAPHIR

25. Th. S. Bauer - NIKHEF 133 M events (taken ~5 years ago) trigger = 2 charged tracks signal: ~ 50 events corresponds to production cross section of  ~ 200 nb. SAPHIR (Elsa-Bonn) (  + 1 H ) this is “≈ 20 % of ,  and  1520 cross sections” – and d ec r e a s i n g with time. “rising with energy”

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

27. Th. S. Bauer - NIKHEF NA49

28. Th. S. Bauer - NIKHEF NA49 ( p-p, √ s = 17 GeV) p-p scattering at √ s = 17 GeV signals for  -- : combining  - and  - cross check with other charge combinations. can use  0* 1530 as benchmark.

29. Th. S. Bauer - NIKHEF NA49 Remarks: opening angle  lab > 4.5 º

30. Th. S. Bauer - NIKHEF NA49 Remarks: opening angle  lab > 4.5 º !!!  lab is not a physical parameter !!!

31. Th. S. Bauer - NIKHEF NA49 Remarks: opening angle  lab > 4.5 º !!!  lab is not a physical parameter !!!   0 1530 visible, but weaker than  - - (1860) (due to some cuts... total  *0 1530 signal is ~150 evts.)

32. Th. S. Bauer - NIKHEF NA49 versus NA49 Criticism: (Thanks to H.G. Fischer and S. Wenig, CERN, hep-ex / 0401014 – 12 Jan 2004) NA49 used 1640  - and 551  + events NA49 sees a total of ~ 150  *0 1530 S.N. Gangule et al. (NP. B128-408, (1977) report ~ 800  *0 1530 from S.N. Gangule et al. Nucl.Phys. B128, 408, (1977)

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

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

35. Th. S. Bauer - NIKHEF What is hidden beyond 1.8 GeV in WA89 ?? total: ~ 150  0* Note: 63 000 ± 6 000  0* ?

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

37. Th. S. Bauer - NIKHEF NA49  +  nK + a)nK + inv. mass spectrum; b) deviation from polynomial;

38. Th. S. Bauer - NIKHEF NA49  +  nK + a)nK + inv. mass spectrum; b) deviation from polynomial; c) 30 % of  1520 added as a hypothetical  + ; d)statistical significance of added signal. note: different E-scale!

39. Th. S. Bauer - NIKHEF Hermes

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

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

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

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

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

45. Th. S. Bauer - NIKHEF Hermes ( e-A, E e = 27 GeV) note: width  1670 small (25 ~ 50 MeV/c 2 ) width  1690 small (50 ~ 70 MeV/c 2 )  -channel

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

47. Th. S. Bauer - NIKHEF 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.”

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

49. Th. S. Bauer - NIKHEF Hera-B ( p-A, √ s = 42 GeV) finally, a signal which one would like to believe... K 0 - p

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

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

52. Th. S. Bauer - NIKHEF Hera-B ( p-A, √ s = 42 GeV) and let come back...

53. Th. S. Bauer - NIKHEF Hera-B ( p-A, √ s = 42 GeV) if only we couldn’t make it come and go...... a signal which we would like to believe... ? ? ? ? let me explain:

54. Th. S. Bauer - NIKHEF K s – proton as artefact: 1. take the Armenteros-Podolanski plot for K s and  2. select overlap region between K s and 

55. Th. S. Bauer - NIKHEF 3. add third particle (proton) with momentum ≈ to one of the pions. K s – proton as artefact: Result: This is a MC generated peak!

56. Th. S. Bauer - NIKHEF Hera-B ( p-A, √ s = 42 GeV) this “   ” signal appears if : -  -K s ambiguity not 100 % removed; - clones not 100 % removed - protons not 100 % identified

57. Th. S. Bauer - NIKHEF Hera-B ( p-A, √ s = 42 GeV) REAL RESULT p likelihood > 0.95 No evidence of resonances in the mass region around 1.530 GeV.

58. Th. S. Bauer - NIKHEF NA49 versus Hera-B  *0  --

59. Th. S. Bauer - NIKHEF NA49 versus Hera-B  *0  -- note: Resolution Hera-B ≈ 3.5 MeV note: different scales!

60. Th. S. Bauer - NIKHEF Yields and  (taken from publications) ++   (1520) SPring-819 ± 2.84.6 ≈ 1500≈ 35 CLAS-d43 ± ?5.8 ≈ 126≈ 212 CLAS-p27 ± 84.8 -- SAPHIR63 ± 134.8 --530 ± 90 Neutrino27 ± 86.7 -- Diana27 ± ?4.4 -- Hermes≈ 70 ± 18≈ 4 ?? (≈ 400) SVD-2~ 50 ± ?≈ 5.6  - -  NA49no signal !36 ± 6 ?5.6

61. Th. S. Bauer - NIKHEF Summary by now, >8 experiments claim positive signals; all signals are weak: << 100 events;  between ~ 3 and 6 or 7 (could be discussed) but...

62. Th. S. Bauer - NIKHEF SPring-8: correction for Fermi motion ? Particle identification ? proton veto through SSD, and only in region where proton expected. Problems

63. Th. S. Bauer - NIKHEF CLAS : Problems - 2 Quenching through rescattering process likely to be strongly underestimated; Newest results show two peaks: 1.528 GeV and 1.578 GeV first peak agrees with other experiments SPring-8 Fermi motion correction does not work; second is new and is not seen by other expts.

64. Th. S. Bauer - NIKHEF  ++ SAPHIR : ≈ 200 nb Problems - 3 Hermes : ≈ 100... 200 nb ≈ 1.5.. 3 0.3 equal?? CLAS : ≈ 10... 20 nb *) *) includes rescattering (presumably) cross section 30 % of  1520 added as a hypothetical  + ;

65. Th. S. Bauer - NIKHEF Problems – 4  -- NA49 claim not confirmed by high-statistics experiments; NA49 doesn’t see established resonances; NA49 even doesn’t see the  +... *) *) that is to say: if it exists

66. Th. S. Bauer - NIKHEF Problems – 5 Hermes needs * and ** -resonances to fit background in p-K 0 ; Note: p-K - channel 30 times more efficient than p-K 0 channel... but doesn’t see well established *** and **** resonances in p-K - channel;

67. Th. S. Bauer - NIKHEF Problems – 6 p-K 0 peak can be created by clones together with excess at K 0 -  crossing...

68. Th. S. Bauer - NIKHEF a way out ?? What about the width???

69. Th. S. Bauer - NIKHEF a way out ?? What about the width??? How can a state at this energy be so narrow??

70. Th. S. Bauer - NIKHEF a way out ?? What about the width??? How can a state at this energy be so narrow?? my (an experimentalist’s) theoretical prediction is:

71. Th. S. Bauer - NIKHEF a way out ?? What about the width??? How can a state at this energy be so narrow?? my (an experimentalist’s) theoretical prediction is :  ≈ 10 -22 eV

72. Th. S. Bauer - NIKHEF a way out ?? What about the width??? How can a state at this energy be so narrow?? my (an experimentalist’s) theoretical prediction is :  ≈ 10 7 s

73. Th. S. Bauer - NIKHEF a way out ?? What about the width??? How can a state at this energy be so narrow?? my (an experimentalist’s) theoretical prediction is :  ≈ 10 7 s

74. Th. S. Bauer - NIKHEF Thomas S. Bauer - NIKHEF

75. Th. S. Bauer - NIKHEF Thomas S. Bauer - NIKHEF

76. Th. S. Bauer - NIKHEF