5 Main directions of our research SU(3) classification of baryonsProperties of antidecuplet in ChQSM: two approaches- quantization of slow soliton rotation- calculation of light-cone wave functions, Fock decompositionPredictions for processes where pentaquarks are producedPhenomenological analysis of the data
6 SU(3) analysis of antidecuplet Guzey and Polyakov, hep-ph/hep-ph/Gell-Mann, Ne‘eman, 1960s:The hypothesis of approximate flavor SU(3) symmetry ofstrong interactions existence of definite SU(3) multipletsNon-exotic hadrons:mesonsbaryonsExotic hadrons:antidecuplet
7 Gell-Mann, Okubo, 1960s:SU(3) symmetry is broken by mass of strange quarkmass splitting inside multiplets:Gell-Mann—Okubo mass formulasoctetdecupletantidecupletGMO mass formulas work with a few % precision!
8 Samios, Goldberg, Meadows, 1974: Step 1:Assuming that SU(3) symmetry is broken only by non-equalmasses, but holds for coupling constants, SU(3) symmetrygives also a good description of strong decays. We performeda new analysis of all known baryons and suggested newSU(3) systematization of known baryons.Step 2:Apply methods of SU(3) symmetry to antidecuplet.Goal:Model-independent systematization of scarce experimentalinformation on antidecuplet.
11 What is known about the antidecuplet? The lightest member is with MeVThe heaviest member is with MeVThe and members are not establishedHowever, there is candidate with MeVCharacteristic properties:- weakly couples to state, narrow- significantly couples to state- photoproduction on protons is suppressedAlt, NA49, CERNArndt et al., 2004V. Kuznetsov, Graal, 2004A. Rathke, MVP 2003
12 Photon has U-spin = 0. Good filter for multiplets Anti-decuplet N can be photoexcited only from the neutron target(A. Rathke, MVP `03)I3Y
13 Modified PWA of pi N scattering Arndt, Azimov, Strakovsky, Workman,MVP, PRD04
14 Simple analysis: compared with GRAAL GRAAL, V. Kuznetsov et al.hep-exhn coincidence measurementBreit-Wigner + smooth BGM ～ 1666 MeVG ≦ 40 MeVM ～ 1680 MeVG ≦ 30 MeVJ.Kasagi, talk in Kyoto 24.11There is a resonance whose width smaller than 50 MeV,however, resonance parameters strongly depend on BG shape!!
15 Antidecuplet decays: mixing with octet mixing angleoctet couplingconstantsConclusion: A small mixing withnon-exotic octet helps to understandthe trend of the data. Range of mixingangles is in agreement with predictionsof ChQSM
16 SU(3) predictions for antidecuplet decays suppressedsizableonly due to mixinglarge branchingCan be looked forin existing data?
17 Photocoupling to antidecuplet Azimov, Kuznetsov, Strakovsky, MVP, EPJ 05Analysis of GRAAL dataKim, Yang et al. PRD 05Model independent approach inChQSM
18 General Formalism in the SU(3)f χQSM 1w‘s are universal constants, enter also magnetic momentsof octet and decuplet. Obtained from fit to them.
19 K* coupling to antidecuplet and production x-section in photoreactions Using estimated transition magnetic moments, VMD and SU(3)Symmetry one can estimate K* couplingAzimov, Kuznetsov, Strakovsky, MVP `06With these range of values one computesproduction x-section for g+p -> Ks+Qand Compare with CLAS limitsKwee, Guidal, Vanderhaeghen, MVP PRD05CLAS null results do not exclude existence of pentaquark
20 Width of pentaquark is anomalously low! Pentaquark width and Light-Cone baryon wave functionsfrom ChQSMWidth of pentaquark is anomalously low!Cahn and Trilling hep-ph/G = 0.9 0.3 MeVDIANA coll. hep-ph/G = 0.36 0.11 ? MeVWhat ChQSM tells us about pentaquark width?G < 15 MeVOriginal DPP97 prediction, w/o accounting all symmetry breaking effectsG < 2.5 MeVGhil-Seok Yang et al., with full accounting all symmetry breaking effects and new data on axial charges and Sigma-term
21 cQSM, a low energy model of QCD Large-NC arguments allows us to consider a mean classical pion fieldRelativistic Mean Field ApproximationWe need a stable pion field configuration different from the vacuum → solitonWe suppose maximal symmetry→ hedgehog ansatz6/25
22 Light-cone baryon wave functions Advantages of light-cone formulation:The vacuum of the free and interacting theory are the sameThe concept of wave function is meaningful and any particle is a superposition of Fock statesThe vector and axial operators do not create or annihilate pairs11/25
23 Light-cone baryon wave functions In the cQSM it is easy to define the wave function at restValence levelp-fieldp-fieldQuark-antiquark sea12/25
24 Light-cone baryon wave functions By definition light-cone wave functions are wave functions in the infinite-momentum frame (IMF)We then perform a boost withA particular baryon B with spin projection k is obtained thanks to its rotational wave function13/25
25 Light-cone baryon wave functions Projection onto a particular Fock component is obtained by means of a SU(3) Clebsch-Gordan techniqueWe used instead explicit group integrals to see symmetries of the quarks wave functions14/25
26 Light-cone baryon wave functions Properties of baryons are then obtained by sandwiching the corresponding operatorCharges:gA, gQKN, mN, mD, …16/25
28 Axial charges are defined as Results and commentsAxial charges are defined asThey are related to the first moment of polarized quark distribution18/25
29 C. Lorce hep-ph/0603231 (published in Phys. Rev. D74; 054019, 2006) Results and commentsMeans that the proton spends0.3 of ist life-time as a 5-quarkProton axial resultsgA(3)gA(8)gA(0)DuDdDsN(5)/N(3)CQM5/31/√314/3-1/3cQSM(5q dir)1.3590.4990.9001.123-0.2360.0120.536(5q dir+ex)1.3600.5000,9011.125-0.2350.550(rel. 5q dir)1.2410.4440.7871.011-0.2300.0060.289Exp.1.257±0.0030.34±0.020.31±0.070.83±0.03-0.43-0.10-C. Lorce hep-ph/ (published in Phys. Rev. D74; , 2006)
31 Results and commentsA more accurate estimation of Q+ width by computing form factors at non-zero momentum transferWe impose energy conservation in IMF
32 Results and commentsMomentum conservation allows only part of quark configurations to decay into a nucleon and a kaonOne can then expect a reduction of the width
33 Results and commentsOne can see that the 5-quark component in nucleon has a non-negiligible impact on its physical observablesOne can then expect the same happening when considering the 7-quark component for the pentaquarkHere are all the possible diagrams
34 Conclusion and outlook Compute the 7-quark componentStudy the quark-antiquark content in detailsStudy magnetic moments and magnetic transitionsParton distributions
36 Analysis of production in reaction V. Guzey, PRC 69 (2004);hep-ph/Motivation:To understand the negativeCLAS results of searchin the reactionS. Niccolai, CLAS, hep-ex/
37 Main idea and method:Assume a particular reactionmechanism for productionandfor the background reaction
38 Conclusion:Cancellation betweennegative interferenceand positive signalcontributions wash outany signs ofCLAS data does not meanthat does not exist!Nice example how very small Theta signal can be enhanced byinterference with strong background !!! Play with it !!!
39 Conclusions and Outlook -We developed a new way to study properties ofbaryons through the LCWF computed in ChQSM- usual baryons are NOT 3-quark states- new systematic way to study various baryon propertiesChQSM naturally accomodates sub-MeV pentaquark width, checkedby two complimentary methodsGlobal SU(3) analysis of baryons allows to restrict considerably properties of possible antidecouplet baryons. This analysis is alsoimportant for usual baryons, any new N resonance should opena new SU(3) multiplet.It seems that null results on pentaquark search do not mean itsnon-existence
40 Conclusions and Outlook -We should not rush to the conclusion that pentaquarks aredead! Instead, we plan to suggest new ways to enhance aparentlysmall signal of pentaquark, e.g. through interferenceTo understand the nature of „anomaly“ in eta photoproductionon the neutron. I think that this should be one of central topicsof our SFB:- potential bright discovery, independently of anti-10 interpretation- good possibility for collaborations of various groups (e.g A2, A4)- if 5-quark, we expect good signal in 2 pi photoproduction ondeuteronThe pentaquark programme is still in the focus of several labs, furtherstudies of 5-quark properties and estimates of processes are urgentlyneeded to analyse new data and possibly reanalize old data.
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