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

This research presentation outlines the observation of a new pentaquark candidate state X3/2 in proton-proton collisions using the NA49 detector at the Ruđer Bošković Institute in Zagreb, Croatia. The study includes the analysis of X-p invariant mass spectra, systematic studies, and preliminary X(1530)0p spectra. Experimental evidence for different pentaquark states like Q+ is discussed, along with models proposed by various researchers over the years. The text provides insights into the experimental setup, data samples, event analyses, acceptance criteria, and statistical findings related to the observed pentaquark state X3/2.

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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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