1 / 61

Status of Pentaquark Search

Status of Pentaquark Search. Valery Kubarovsky Rensselaer Polytechnic Institute / Jlab. Introduction Review of theoretical models Current Experimental Status Second generation experiments Conclusion . Introduction.

kohana
Download Presentation

Status of Pentaquark Search

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Status of Pentaquark Search Valery Kubarovsky Rensselaer Polytechnic Institute / Jlab • Introduction • Review of theoretical models • Current Experimental Status • Second generation experiments • Conclusion Valery Kubarovsky BEACH2004 06/29/04

  2. Introduction • Several experiments have recently reported the observation of the baryon with exotic quantum numbers • Light: M=1525-1555 MeV • Narrow:G< 9-25 MeV (possibly ~1 MeV) • Strangeness S=+1 (opposite to the strangeness of the usual baryons) • This new state was identified as the Q+ pentaquark baryon with quark contents . • There is also evidence for two related states with the strangeness S=-2, Valery Kubarovsky BEACH2004 06/29/04

  3. The Anti-decuplet in the cSMD. Diakonov, V. Petrov, M. Polyakov, Z.Phys.A359, 305 (1997) S=+1 updated version D. Diakonov, V. Petrov, arXiv:hep-ph/0310212 Dm = 108 MeV S=0 S=-1 S=-2 Valery Kubarovsky BEACH2004 06/29/04

  4. Theory Response to the Pentaquark • Anti-charmedQoc and anti-beautyQ+b • Q+andQ+produced in quark-gluon plasma • Instantons and diquark clustering • Triquark-diquark cluster model • Pentaquarks and radially excited baryons • Peanut-shaped quark-diquark model • Pentaquarks in the color-flavor-locking • superconducting phase • ……. • Chiral soliton P=+ • Kaon-Skyrmion P=+ • (qq)2-q P=+ or P=- • Kaon-nucleon resonance • Super radiance resonance • QCD sum rules • Lattice QCD P=-, or find no signal • Higher exotic baryon multiplets • Pentaquarks in string dynamics • P11(1440) as pentaquark • P11(1710) as pentaquark • Q+as isotensor pentaquark • Topological soliton • Q+(1540) as a heptaquark • Exotic baryons in the large Nc limit More than 220 papers since July 1, 2003 Valery Kubarovsky BEACH2004 06/29/04

  5. Quark description (Jaffe, Wilczek) L=0 (ud) s L=1 (ud) L=1, one unit of orbital angular momentum needed to obtain as in the cSM Soliton: (naïve version) JP = ½+ Q-LQCD: JP = ½- Meson fields Pentaquarks models Chiral soliton model: (Diakonov, Petrov, Polyakov) Predicted the mass and the width of 5Q. ‘Pentaquark’ comes out naturally from these models. They represent rotational excitations of the soliton JP = ½+ Valery Kubarovsky BEACH2004 06/29/04

  6. Baryons (8) 4Q Mesons Mesons 5Q Baryons DiBaryons Baryons (10) QCD instantons (Shuryak hep-ph/0310270) DiQuarks are building blocks of multiquark states: pentaquarks and dibaryons A nucleon is made of a quark and deeply bound scalar-isoscalar diquarks, absent in the decuplet. In the instanton liquid model there are two kind of diquarks, the scalar and the tensor (with spin=1) Valery Kubarovsky BEACH2004 06/29/04

  7. QCD instantons • The DiQuark mass is about the constituent mass. • Two possible scenario: Scalar DiQuarks are in a P-wave M(Q+) = 1880 MeV Scalar and tensor DiQuarks in S-wave M(Q+) = 1550 MeV • G(Q+) = 2.6 MeV • The narrowness of the partial widths follows from the small overlap between the three and five quarks wave functions due to the different internal structure. Valery Kubarovsky BEACH2004 06/29/04

  8. Current Experimental Status Valery Kubarovsky BEACH2004 06/29/04

  9. Super Photonring-8GeVSPring-8 • Third-generation synchrotron radiation facility • Circumference: 1436 m • 8 GeV • 100 mA • 62 beamlines Valery Kubarovsky BEACH2004 06/29/04

  10. LEPS detector g 1m Valery Kubarovsky BEACH2004 06/29/04

  11. K/p separation (positive charge) Reconstructed mass p- p+ p+ p K+ K+ Events d Momentum (GeV) K- Mass(GeV) Mass/Charge (GeV) Charged particle identification s(mass) = 30 MeV/c2 for 1 GeV/c Kaon Valery Kubarovsky BEACH2004 06/29/04

  12. Non-resonant KK L(1520) Q+? LEPS analysis • Problems: • no neutron target • CH start counter • Fermi motion corrections • Background • fK+K- • (produced from n & p) • K- missing mass gives Q+ mass • K+K- missing mass gives n Valery Kubarovsky BEACH2004 06/29/04

  13. Q+: published mass plot M = 1.540.01 MeV G < 25 MeV Gaussian significance 4.6s • Background level is estimated by a fit in a mass region above 1.59 GeV. • Assumption: • Background is from non-resonant K+K- production off the neutron/nucleus • … is nearly identical to non-resonant K+K- production off the proton background Phys.Rev.Lett. 91 (2003) 012002 hep-ex/0301020 Valery Kubarovsky BEACH2004 06/29/04

  14. DIANA/ITEP (Moscow) • 750 MeV K+ beam incident on 700 liters Xe bubble chamber. • Interaction energy is determined by the range of the kaon. • Charged particles are identified by ionization, momentum is measured by the range. Charge exchange reaction K+N]Q+]pK0S K0S]p+p- Valery Kubarovsky BEACH2004 06/29/04

  15. DIANA • Selecting forward going protons and kaons - Qk and Qp < 100o. • p and K0 are emitted back-to-back - cosFpK < 0. • Peak at 1.539 GeV in the invariant mass of K0p. • Statistical significance4.4s. • Measured widthG < 9 MeV The best limit for width Valery Kubarovsky BEACH2004 06/29/04

  16. Jefferson Lab (CEBAF) Continuous Electron Beam Accelerator Facility Valery Kubarovsky BEACH2004 06/29/04

  17. Torus magnet 6 superconducting coils Electromagnetic calorimeters Lead/scintillator, 1296 photomultipliers Liquid D2 (H2)target + g start counter; e minitorus Drift chambers argon/CO2 gas, 35,000 cells Gas Cherenkov counters e/p separation, 256 PMTs Time-of-flight counters plastic scintillators, 684 photomultipliers CLAS - CEBAF Large Acceptance Spectrometer Valery Kubarovsky BEACH2004 06/29/04

  18. CLAS-gd: Exclusive reaction • Exclusive photoproduction on deuterium: • Experimental data from 1999 run; • Tagged photons with up to 3 GeV energy; • Target: 10 cm long liquid deuterium; Possible reaction mechanism • No correction for Fermi smearing is needed. • Aids significantly to reduce the background. Valery Kubarovsky BEACH2004 06/29/04

  19. CLAS • 15% of non pKK events within ±3sof the peak. • Almost no background under the neutron peak with tight timing cut,DtK. Valery Kubarovsky BEACH2004 06/29/04

  20. CLAS: Cut out known resonances • Several known processes can contribute to the pK+K-(n) final state • gd→fp(n), f→K+K- • gd→L(1520)K+(n), L(1520)→pK- • Both reactions proceed predominantly on the proton (neutron is a spectator). • Kinematics of both reactions are not a good match forQ+production. Valery Kubarovsky BEACH2004 06/29/04

  21. CLAS Q+ M = 1.542 GeV G < 21 MeV (sM=9 MeV) Stat.sig. = 5.2s (4.6-5.8) Gaussian background Simulated background Distribution ofL(1520) events Valery Kubarovsky BEACH2004 06/29/04

  22. CLAS: Photoproduction onhydrogen After PID n Valery Kubarovsky BEACH2004 06/29/04

  23. Possible Q+ production mechanisms in the reaction W. Liu, C.M. Ko, V. Kubarovsky, nucl-th/0310087 Valery Kubarovsky BEACH2004 06/29/04

  24. g p+ K- p p N* Q+ Q+ Production via N* decays Valery Kubarovsky BEACH2004 06/29/04

  25. Q+ • Cosq*(p+) > 0.8 g p+ K- p p N* Q+ CLAS-gp: with forward going p+ • Fitted mass 1.555 GeV • G< 28 MeV consistent with detector resolution • Estimated significance7.8s M(nK+) Valery Kubarovsky BEACH2004 06/29/04

  26. Q+ N* ? g p+ K- p p N* Q+ CLAS-gp: Indicationfor a heavy N*(2430)? There are no pN scattering data in the relevant energy range. M(K-Q+) [GeV] Valery Kubarovsky BEACH2004 06/29/04

  27. CERN/NA49 • Proton-proton collisions at 158 GeV. Similar to CLAS gp Valery Kubarovsky BEACH2004 06/29/04

  28. JP = ½- JP = ½+ What do we know about the width of Q+? Widths seen in experimental analyses are dominated by resolution effects. More precise information is obtained in analyses with theoretical constraints. • HERMES, PLB585, 213 (2004) GQ = 17+/-9+/-3 MeV • S. Nussinov et al., hep-ph/0307357 GQ < 6 MeV (non-observation) • R. Arndt et al., PRC68, 42201 (2003) GQ < 1 MeV (non-observation) • R. Cahn and G. Trilling, PRD69, 11401(2004) GQ= 0.9 +/- 0.3MeV (from DIANA results) • A. Sibirtsev, et al., hep-ph/0405099 (2004) GQ < 1 MeV (K+d Kopp) • First positive identification of Q+ in K+d, including double scattering. • W. Gibbs, nucl-th/0405024 (2004) GQ = 0.9 +/-0.2 MeV (K+d X) Valery Kubarovsky BEACH2004 06/29/04

  29. Q2 < 1 GeV2 M = (3099 +/- 3 +/- 5) MeV Minimal quark content: uuddc Yet to be confirmed! H1-A charmed pentaquark Qo(3100)? c hep-ex/040305 (2004) Q2 = 1 – 100 GeV2 Valery Kubarovsky BEACH2004 06/29/04

  30. JLab-d Spring8 DIANA ELSA ITEP SVD/IHEP JLab-p HERMES ZEUS COSY-TOF CERN/NA49 H1 pp  S+Q+. Evidence for Penta-Quark States Valery Kubarovsky BEACH2004 06/29/04

  31. K+d for ½+ W. Gibbs (nucl-th/0405024) K+d for ½- DM ~ 12 MeV HERMES Spring-8 SAPHIR CLAS-d CLAS-p DIANA COSY ZEUS IHEP ITEP Summary of Experimental Masses Shift could be due to different background shapes and interference effects. Valery Kubarovsky BEACH2004 06/29/04

  32. Null 5Q Results - - Valery Kubarovsky BEACH2004 06/29/04

  33. Dead lock ? • The direct comparison between positive and negative results is possible but difficult due to the lack of theoretical models and experimental data. • Only new high statistics experiments can “cut the knot”. • And these experiments are coming. Valery Kubarovsky BEACH2004 06/29/04

  34. Second Generation Dedicated Experiments Valery Kubarovsky BEACH2004 06/29/04

  35. Q+ K+ g K- n K+ g K- L(1520) p p p n n LEPS-2/Spring8: deuterium target Must correct for Fermi motion of target nucleon bound state in the nucleus “Standard” baryon “Exotic” S=-1 S=+1 Valery Kubarovsky BEACH2004 06/29/04

  36. LEPS: “Default” analysis Preliminary! Nucleon mass f meson M(K+K-) MM(K+K-) Q+ mass [f,N cuts] L(1520) [f,N cuts] MM(K-) MM(K-) Valery Kubarovsky BEACH2004 06/29/04

  37. LEPS-2/Spring8: deuterium target Preliminary • Dedicated experiment • Aimed for 4x statistics • of 2003 result • Announced at N*2004 Valery Kubarovsky BEACH2004 06/29/04

  38. Conclusion of LEPS experimental group • LEPS high statistics experiment has reconfirmed the peak, very unlikely to be due to statistical fluctuations. • The preliminary study shows no indication that the peak is generated by kinematical reflections, detector acceptance, Fermi-motion correction, nor cuts. • “existence ranges from very likely to certain, but further confirmation is desirable” - “three-star” definition by PDG. Valery Kubarovsky BEACH2004 06/29/04

  39. PAC24 (June 2003) approved search for Q+ on deuterium - G10 run -gd K-K+p(n) (data taking completed in May 2004) • CLAS - Search for Q+, Q*+, Q*++ • - G11 run gpvarious final states (running NOW) • Hall A - Search for Q++, So • E04-012 ep eK-X++, eK+Xo (data taking completed) • CLAS – Search for X pentaquarks • EG3 run eD X--, X- X (scheduled for 2004/5) • CLAS- Exotic hadron spectroscopy (to run in 2005/6) - G12 run gp at 6 GeV, high luminosity 5 5 5 Pentaquark Searches at JLab Major program approved by PAC25 (Jan 2004) to search for pentaquark states Valery Kubarovsky BEACH2004 06/29/04

  40. G10 performance (deuterium target) • Exceptional performance of the machine and the CLAS detector. • At each torus current setting accumulated electron beam charge is ~4 times bigger than G2a (target is 2.4 times longer). Valery Kubarovsky BEACH2004 06/29/04

  41. n f L(1520) CLAS- G10 “online” plots gd K-pK+n Fully exclusive processes: L(1820) Ks gd K-pKs(p+p-)psp Valery Kubarovsky BEACH2004 06/29/04

  42. CLAS- G11 Spectroscopy of Exotic Baryons with CLAS: Search for Ground and Excited States RUNNING NOW ! Ks Valery Kubarovsky BEACH2004 06/29/04

  43. New Start Conter: trigger & PID Specifications Extended target cell coverage (40 cm) 2mm thick scintillator + light guide Higher azimuthal segmentation (4 x 6) Time resolution < 1ns (~200 ps in rec) Valery Kubarovsky BEACH2004 06/29/04

  44. G11 status e1c Valery Kubarovsky BEACH2004 06/29/04

  45. CLAS- G11 “online” plots p K0 S- S0 S0 L(1520) L Valery Kubarovsky BEACH2004 06/29/04

  46. G10, G11 Analysis efforts Common rules for all analyses: • Fully calibrated detector system • Use only selected “golden runs” • (fully functioning equipment) • Analysis in well defined CLAS fiducial volume • Energy and momentum corrections • that use independent well-studied channels • Analysis without and with kinematical constraints • whenever possible • Independent analyses by several groups. Valery Kubarovsky BEACH2004 06/29/04

  47. Jlab: Hall A - Search forQ++and S5 Run is completed M=1540 - 1620 MeV s=1.3 MeV Online-analysis M=1560 - 1860 MeV GPDG = 15.6 +/- 1.0 MeV MPDG = 1519.5 +/-1.0 MeV MM(eK+) Valery Kubarovsky BEACH2004 06/29/04

  48. Hall A: Online missing mass distributions s=1.3 MeV Valery Kubarovsky BEACH2004 06/29/04

  49. CLAS- Search forX5Pentaquark States • The search for narrow X5 states can be approached • in at least two ways: • Missing mass technique • Reconstruction of all decay particles • We will explore both possibilities Valery Kubarovsky BEACH2004 06/29/04

  50. 1320 1530 X-(1862)? CLAS –missing mass technique Data from run at Eg < 3.8 GeV • Good missing mass • resolution and low • background. • Needs Eg > 5 GeV, • new start counter Valery Kubarovsky BEACH2004 06/29/04

More Related