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Observation of a new Pentaquark Candidate State X 3/2 in pp Collisions with the NA49 Detector

K. Kadija. Observation of a new Pentaquark Candidate State X 3/2 in pp Collisions with the NA49 Detector. Ruđer Bošković Institute, Zagreb, Croatia. The NA49 Collaboration. 1. Outline. Introduction NA49 experiment Analysis X - p invariant mass spectra

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Observation of a new Pentaquark Candidate State X 3/2 in pp Collisions with the NA49 Detector

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  1. K. Kadija Observation of a new Pentaquark Candidate State X3/2 in pp Collisions with the NA49 Detector Ruđer Bošković Institute, Zagreb, Croatia

  2. The NA49 Collaboration 1

  3. Outline • Introduction • NA49 experiment • Analysis • X- p invariant mass spectra • Systematic studies and checks • Preliminary X(1530)0 p spectra • Conclusion and outlook 1

  4. Introduction

  5. Experimental evidence for Q+ LEPS at Spring-8 SAPHIR at ELSA n KK+ gn K+K-n 0 gp (pK+K-) S M = 1.54 ± 0.004 ± 0.002 GeV/c2 M = 1.54 ± 0.01GeV/c2 G≤ 0.025 GeV/c2 G≤ 0.025 GeV/c2

  6. Experimental evidence for Q+ CLASS at JLAB CLASS at JLAB gp p+K+K- (n) gd pK+K- (n) M = 1.542 ± 0.01 GeV/c2 M = 1.54 ± 0.01GeV/c2 G≤ 0.032 GeV/c2 G≤ 0.021 GeV/c2

  7. Experimental evidence for Q+ HERMES at DESY A.E. Asratyan, A.G. Dolgenko, M.A. Kubantsev } 0 nm (n m) D pK + X + 0 S pK + X eD nm (n m) Ne S pK + X 0 S M = 1.526 ± 0.002 ± 0.002 GeV/c2 M = 1.533± 0.005GeV/c2 s = 0.0075±0.0024 GeV/c2 G≤ 0.020 GeV/c2

  8. Experimental evidence for Q+ DIANA at ITEP 0 K+Xe KS p Xe’ M = 1.539 ± 0.002 GeV/c2 G ≤ 0.009 GeV/c2

  9. Experimental evidence for Q+ Width = ? IP = 0?

  10. Models: Chiral Soliton Suggested anti-decuplet of baryons: JP=1/2+ D. Diakonov, V. Petrov, M. Polyakov, Z.Phys. A 359 (1997) 305 (ududs) ! Q+(1530) (G≤ 15 MeV) Input N(1710) D m ~ 180 MeV ~ 10 S(1890) (G X3/2 Xp 42 MeV) ~ X3/2(2070) ~ (dsdsu) (ususd) + - - X3/2 X3/2

  11. Models: Correlated quarks Suggested 10f 8f of baryons: JP=1/2+ + R. Jaffe and F. Wilczek, arXiv:hep-ph/0307341 Input MQ = 1540 MeV /c2 Q+ |(ud)2S> 3 Input + MN = 1440 MeV /c2 N |(ud)2d> MN = 1700 MeV /c2 NS |(ud)(su)s> S + MS =1600 MeV /c2 S |(ud)(su)d> 3 MS =1850 MeV /c2 S S |(su)2s> S 1- 1/2- = 1/2+ , 3/2+ O 3 3 3 8f + 10f O O MX =1750 MeV /c2 - - + X3/2 |(ds)2u> X3/2 |(us)2d> ~ GX 1.5 * GQ ~

  12. Models: Lattice QCD F. Csikor, Z. Fodor, S.D. Katz, T.G. Kovacs, arXiv: hep-lat/0309090 Continuum extrapolated mass ratio for the lowest pentaquark states Continuum extrapolation of the mass ratio IP m5q = mQ + I P Nucleon mass in Lattice units

  13. Models + Chiral soliton model Correlated quarks PARITY Uncorrelated quarks - Lattice QCD 10 Chiral soliton model Heavy exotic cascades ?? SPECTRUM Quarks Light exotic cascades 10 + 8

  14. NA49 Experiment VTPC-1 (VTPC-2+MTPC) dp/p2 = 7 x (0.3) 10-4 (GeV/c)-1 3-6 % dE/dx resolution sTrig= 28.1 mb

  15. Data Sample p+p at =17.2 GeV Before vertex cut After Vertex Cut 1999 1.2 M 0.66 M 2000 2.7 M 1.5 M 2002 2.9M 1.6 M Total 6.8 M 3.76 M Main vertex cuts: 1.) fit converged 2.) x2+y2< 1 cm2 3.) -590.5 cm < z < -572.5 cm (i.e. within target)

  16. X - y x z MV by bx X3/2selection Applied cuts: • Distance to Bethe- Bloch curve: |dbb| < 3 s • |M(pp-) - 1.115683| < 0.015 MeV • Z X- Zmain_vtx > 12 cm • X- position at main vertex (bx , by): |bx| < 2 cm |by| < 1 cm • p(from X- decay) position at main vertex |by|> 0.5 cm L

  17. V0 and X Invariant Mass Spectra 1640 events |M(Lp)-1.32131| < 0.015GeV 551 events

  18. Primary pion cuts (- , + p) p • |dbb| < 1.5 s, dbb .... distance to Bethe-Bloch curve • position at main vertex (bx , by): |bx| < 1.0 cm |by| < 0.5 cm • # of point cut > 10

  19. X-p Invariant Mass Distribution

  20. X+p Invariant Mass Distribution

  21. Monte Carlo Simulation Input: f(y) ---> flat f(pT) ---> thermal , T=160 MeV Minv ---> 1860 MeV/c2 '' Acceptance '' (y: rapidity)

  22. Additional cuts:Opening Angle From the Monte Carlo simulation q > 4.5 0 Signal Background q: lab. angle betweenX- andp+

  23. Additional cuts:dE/dx+ momentum Negative tracks e- (X- p - ) events p- K P Positive tracks (X- p + ) events

  24. Additional cuts cos(q) < 0.997 (q > 4.5) X-X+ p- -1.5s < dbb< 1.5s-1.5 s < dbb< 1.5 s p+-0.5s < dbb < 1. 5 s -1.5s<dbb < 1.5 s pp > 3 GeV/c pp > 3 GeV/c p p p p

  25. Final Xp Invariant Mass Distributions C. Alt et al., hep-ex/0310014 Accepted for publication in PRL

  26. Systematics study (X-p- ) By changing: - mass cuts around XandL - dE/dx cuts - number of point cuts - bx, by cuts - e.t.c. Peak remains robust !

  27. Systematics study:Resonances events with

  28. Systematics study : Monte Carlo X- pfrom the Venus MC p :all negative particles p : p-

  29. X-p- invariant mass from shoulders

  30. Summed spectra

  31. Mass and width determination M = 1.862 ± 0.002 GeV/c2 M = 1.864± 0.005 GeV/c2 M = 1.862 ± 0.002 GeV/c2 G≤ 18 MeV/c2

  32. X-- Significance B0= 43 S0 ≥ 35 S0 ≥ 38 S0 ≥ 41 Mwindow= M0window± DM (1.850 ≤ M0window≤ 1.8725 ) [GeV/c2]

  33. + X0(1530) p+ X 3/2 X 3/2(1/2) X0(1530) p- X- p+ X- p+ L p- L p- p p- p p- p+ X0(1530) X 3/2(1/2) p- X- L p p- p- Search for X-and X+ via X(1530)0 decay

  34. X(1530)0p- :VERYPRELIMINARY X(1530)0 Entries / 7.5 MeV/c2 M=1.855 ± 0.003 GeV/c2

  35. X(1530)0 p: VERY PRELIMINARY No evidence for X+to X(1530)0 p+ decay X(1530)0 p+ No cuts X(1530)0 p- No evidence for X+to X(1530)0 p+ decay X(1530)0 p+ pp > 3 GeV/c + - 0.5 s < dbb < 1.5 s p X(1530)0 p-

  36. In SU(3) 10 10 8 What do we expect ? Q+ + X3/2 X3/2 - - X3/2 X1/2   X(1530)0 p+ X(1530)0 p- X(1530)0 p-

  37. Conclusion I • A strong evidence for existence of a narrow - -resonance at M = 1.862 ± 0.002 GeV/c2 ( ≤ 18 MeV/c2) is observed • At the same mass a peak is observed in the-+ spectrum • The corresponding antibaryon spectra show enhancement at the same mass 0 0 X3/2 - - X3/2 X1/2

  38. Conclusion II • Some evidence for existence of a narrow (1530)0 p-resonance at M = 1.855 ± 0.003 GeV/c2 is observed • There is no indication for X(1530)0p+ resonance 0 0 - X3/2 - - X3/2 X1/2 X1/2

  39. Outlook Open Questions • Spin is unknown • Parity is unknown • Width ? • Isospin? NA49 • Further improvement of experimental resolution • Search forSs0(-) X- K+ (X- KS) o NA49’ Project (Expression of Interest CERN-SPSC-2003-038) In particular : • (3-6) • 107 p+p events (new DAQ system) • Neutral pions

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