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M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004 1 Observations of PentaQuarks: A Mini-Review By A. Dolgolenko and M. Kubantsev.

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Presentation on theme: "M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004 1 Observations of PentaQuarks: A Mini-Review By A. Dolgolenko and M. Kubantsev."— Presentation transcript:

1 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May Observations of PentaQuarks: A Mini-Review By A. Dolgolenko and M. Kubantsev

2 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May Introduction Observations of the Θ + (1540) state: year of 2003: 2004 results (up to mid-May): Other possible exotic baryons. Further studies, summary and outlook Content First evidence from photo production (Spring-8) Low energy kaon beam (ITEP) Photo/electro-production (JLAB, ELSA, HERMES) High energy electro-production (ZEUS) Low energy proton beam (COSY) High energy hadron beams (Serpukhov, Dubna, Fermilab,CERN, RICK) e + e - -collisions at BES and LEP Neutrino beam (ITEP-CERN-FNAL) } over 200 citations!

3 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May Introduction All well established baryon states can be understood as combinations of three valence quarks: u, d, s. These combinations are grouped in SU(3) singlets, octets and decuplets:

4 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May Any baryons that can not be made with this triplet are to be considered as exotic. The simplest configuration might consist of four quarks plus anti-quark: QQQQQ. This state is called a pentaquark. Truly exotic states has Q with other flavor then other four quarks: uudds (S =+1, Q =+1) ssuud (S = -2, Q = +1) ssddu (S= -2, Q =-2) Other states can mix with standard baryons. ( No heavy flavors considered in this talk (see H1 talk) Why is the Baryon State called Exotic ?

5 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May Indeed, history of S = +1 system search was not encouraging:

6 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May In 1997 D. Diakonov, V. Petrov and M. Polyakov proposed, on basis of a chiral soliton model, a low-mass anti-decuplet of pentaquarks (qqqqq). Predicted lower mass, s=+1 state has mass of 1530 MeV/c 2 and narrow width <15 MeV/c 2. Three baryons in the triangle corners are exotic. They have been bold enough to persuade experimentalists to look for these states, so in the beginning of 2003… Z +( 1530), later Θ + (1530) S = +1 N(1710) Σ (1890) Ξ(2070) nK + or pK 0 uudds uussd Ξ 0 π + or Σ + K 0 ddssu Ξ - π - or Σ - K - Prediction of narrow and exotic light baryons /2 I -1/21/23/21

7 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May LEPS at SPRING-8: FIRST OBSERVATION S = +1 baryon resonance in K - missing mass spectrum of γn K + K - n reaction on carbon was found: Mass of 1540 ± 10 Mev/c 2. Peak significance is 4.6 σ Peak width is < 25 MeV/c 2 γ K-K- K+K+ nn Θ+Θ+

8 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May DIANA BC at ITEP(MOSCOW) The peak near 1540 MeV/c 2 of total 73 events has estimated background of 44 events, resulting in statistical significance of 4.4 σ Gaussian fit of the peak yields: M = 1539 ± 2 MeV/c 2 Γ <9MeV/ c 2 (compatible with instrumental resolution)

9 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May CLAS with D target at JLAB

10 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May Θ + signal(fit): N Θ+ = 63±13 events M = 1540 ± 4 ± 2 MeV/c 2 Γ < 25 MeV/c 2 Significance: 5.2 σ σ(Θ + ): σ(Λ 0 (1520))= 1:15 No signal in Θ ++ K + p suggests isoscalar state SAPHIR at ELSA

11 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May events with ~15 events of the background; significance of 6.7 σ. Neon plus Deuterium Mass=1533 ± 5 MeV/c2 Width <20MeV/c2 Observation of Θ + in neutrino interactions:ITEP-FNAL-CERN A.E.Asratyan et al.,hep-ex/ Phys. Atom.Nucl. 67,682(2004) Re-analysis of data from FNAL (E180,E632) and CERN(WA21, WA25,WA59) bubble chambers with H, D, Ne fills. Signal is seen only on D and Ne.

12 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May CLAS with p-target at JLAB V. Kubarovsky et al., hep-ex/ Phys. Rev.Lett.92,032001(2004) N Θ+ = 41±10 events M = 1555 ± 10 MeV/c 2 Γ = 26 ± 7 MeV/c 2 Significance: 7.8 ± 1 σ No signal in pK + system, so Θ + is possibly isoscalar

13 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May Propane 2-meter bubble chamber in heavy ion beam (C) of Dubna accellerator. The signal is impressive: ~ 9 σ effect(!?) R. Togoo et al., Proc. Mongolian Acad.Sci.,4(2003),2 Dubna:C-C interactions at 4.2 GeV/nucleon

14 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May A.Airapetian et al., hep-ex/ , Phys.Lett.B585,213(2004) HERMES(e + D) at DESY N Θ+ = 56 events M = 1528 ± 2.6 ± 2.1 MeV/c 2 Γ = 19 ± 5 ± 2 MeV/c 2 Significance: 4 – 6 σ e + (27.6 GeV)D K 0 (π + π - )pX

15 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May SVD(pA) at Serpukhov A.Aleev et al., hep-ex/ N Θ+ = 50 events M = 1526 ± 3.1 MeV/c 2 Γ <24 MeV/c 2 Significance: 4 – 6 σ Production cross section for X F > 0 (30-120) mkb

16 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May COSY -TOF M =1530 ± 5 MeV

17 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May S. Chekanov for ZEUS: hep-ex/ (latest update) GeV C.M.S. energy with integrated luminosity 121 pb -1 N Θ+ = 221 ± 48 events M = 1522 ± 3.1 MeV/c 2 Γ = 8 ± 4 MeV/c 2 Significance: 4.6 σ No Θ ++ observed: isoscalar(?) Evidence from e-p collider experiment ZEUS

18 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May S.Salur for STAR at RHIC: hep-ex/ Preliminary results from STAR(p-p collisions ) 200 GeV C.M.S. energy with 8 million events Possible ~1520 Mev/c 2

19 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May Average 1531±3±4 Summary of observations

20 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May Summary of observations (supplemental) Reaction and energy (GeV)Θ++ signal Production cross- section, μb Collaboration γd→ K - p K + n (2.5


21 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May CERN: K + p  pK 0 X Bubble Chamber Data 1.54 GeV A.Berthon, et al., Nucl. Phys. B63, 54 (1973) The unclaimed   (1540) ? Presented by V.D.Burkert at Penta-Quark 2003.

22 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May Estimation of Θ + width (summary) Direct high resolution width measurements are under way now.

23 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May Estimation of Θ + width (summary,cont.) Kaon experiments Direct observation(DIANA): < 9 MeV R. Cahn and G.Trilling (DIANA re-analysis) 0.9 MeV S. Nussinov (K + n and K + d) <6 MeV R. Arndt et al (K + n and K + d) <1.5 MeV I.Strakovsky et al: PWA for K + n(I=0) with P 01 (J p =3/2 + ) <1-2 Mev Other partial waves: S 01 (J p =1/2 - ) and P 03 (J p =3/2 + ) are not conclusive W.R. Gibbs (K + d cross section re-analysis) 0.9±0.2 Mev (nucl-th/ , May ) Data from T. Bowen et al. Phys.Rev. D2,2599(1970), A.S. Carrol et al. Phys. Lett.45B, 531(1973) : 1.Masses are peferable for S 01 and P 01

24 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May Possible two candidates for members in the anti-decuplet with strangeness -2 and possible isospin 3/2 are observed: Ξ -- 3/2 Ξ - π - - an exotic state Ξ 0 3/2 Ξ – π + - a non-exotic state Ξ(?!) NA49(pp)at CERN SPS Experiment NA49 at CERN study proton-proton interactions on at √ s = 17.2 GeV with large acceptance (-0.2

25 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May Decay Ξ -- 3/2 Ξ - π - of the exotic state with mass M = 1862 ± 2 MeV/c 2 Γ = 18 Mev/c 2 Significance ~ 4 σ At the same mass the non-exotic state decay is observed: Ξ 0 3/2 Ξ – π + Corresponding antiparticles spectra show enhancements at the same place. Ξ - π - Ξ - π + NA49(pp)at CERN SPS C.Alt et al., hep-ex/ , Phys.Rev.Lett.92, (2004) pp Ξ πX

26 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May H1 Collaboration, submitted to Phys. Lett. B (Mar 2004) M=3.099± GeV uuddc H1: Narrow anti-charm baryon state

27 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May However, not all experiments NOW looking for pentaquarks see the signal (after 2003)

28 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May Summary of Observations 2004(May) WhereReactionMass interval LimitComment BESe + e -  J/ψ  KNX < (branching) Azimov: < HERA-BpA  K 0 p X15N/Avs NA49,SVD PHENIXdAu  K + n X N/Avs STAR, Dubna CDFpp  Z  K 0 p X1525–1545<87(79) eventsvs ZEUS, STAR ALEPHe + e -  Z  K 0 p X1525–1545<.003 (events)No D-events (K-L) DELPHIe + e -  Z  K 0 p X1500–1750<.006(events)No D-events (K-L) ZEUSep  Ξ π X N/Avs NA49 CDFpp  Ξ π X /?vs NA49 FOCUS  A  Dp XN/A vs H1 WA89 Σ- A  Ξ π X N/Avs NA49 Summary of 2004 non-observations(by May)

29 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May LEPS(04) is a dedicated experiment for pentaquark search. Preliminary results are presented by T.Nakano on March 24 and K. Hicks on May 4. Jefferson Lab has an pentaquark experimental program (V.D. Burkert): CLAS-G11 –> 20X increase of statistics (March-April) PQE(Jlab ) –> high resolution study(running) Several Jlab experiments are under preparation. All previous experiments were not designed for pentaquark search(except LEPS(03) and DIANA).Several high statistics dedicated experiments are now in progress:

30 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May LEPS: new deuterium results Preliminary data (not yet published) Higher statistics (5-10 times more) Minimal “cuts” on the data: –Particle ID of K+, K- –Missing mass = Nucleon mass –Remove  -meson production events Further cuts: –Photon energy –Remove events with more than 2 tracks –Remove  (1520) New LEPS experiment (2004) : γ D  K+K-n

31 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May New LEPS experiment (2004) : γ D  K+K-n LEPS  d: remove  (1520) Ken Hicks (Ohio University) Denver APS Meeting May 2, 2004 Θ -peak: 2003: 18 events 2004: ~100 events (x5-10 fold statistics) Preliminary!

32 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May Last news: CLAS-G11(2004) CLAS: Neutron peak has about 10 times the statistics of the earlier CLAS data. This data set will provide a high-statistics test of the  +. MM(K + K - p) Ken Hicks (Ohio University) Denver APS Meeting May 2, 2004 Preliminary!

33 M.Kubantsev ITEP,Moscow/NWU HSQCD-2004,St.Petersburg, Repino,Russia, May AFTER COFEE BREAK… Continue…


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