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1 Xian-Hui Zhong Department of Physics, Hunan Normal University In collaboration with: Qiang Zhao The S=-1 baryons in the K - p scattering

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2 New data from Crystal Ball The recent measurements of K-p neutrals reactions at crystal b all had been reported at eight momentum beams between 514 and 750 MeV/c were reported, which provides us a good opportunity to study the properties of these low-lying Σ and Λ resonances systematically The unwell-established resonances Motivation R. Manweiler et al, PRC77, (2008); S. Prakhov at el, The S=-1 baryon spectrum is still not well established, such as th e quantum numbers of Σ(1480,1560,1670,1690) (bumps) in PDG are still unknown.

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3 Chiral quark model The meson is looked as a pointed-like particle, which couples to the quarks. Diagrams of the processes X.H.Zhong, Q.Zhao, J.He and B.Saghai, PRC76,065205(2007); X.H Zhong, Qiang. Zhao, PR C79,045202(2009)

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4 Chiral quark model Quark-meson couplings For pseudoscalar- mesons: For vector-mesons:

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5 Chiral quark model The possible resonances in the reactions according to the quark model

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6 Chiral quark model The partial wave amplitudes up to n=2 shell X.H.Zhong, Q.Zhao, J.He and B.Saghai, PRC76,065205(2007); X.H Zhong, Qiang. Zhao, PR C79,045202(2009)

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7 Results Resonance parameters There are very low mass S wave states Σ(1480,1560) !

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8 Results couplings large couplings of Σ resonances to Λπ are needed, large coup ling of Λ (1520) to KN is needed! Small coupling of Λ(1670) to KN is needed. In agreement with the UChPT results [ E.Oset, A.Ramos and C.Bennhold,PLB527,99(2002) ].

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9 Total cross sections Results

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10 Results (K - p Λπ 0 ) Differential cross sections

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11 Differential cross sections Results (K - p Σ 0 π 0 )

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12 Differential cross sections Results (K - p K 0 n)

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13 S wave contributions Obvious evidence of Σ(1480) ! Oller et al., also predicted such a low mass state with UChPT (EPJA28,63;31,527). Results (K - p Λπ 0 )

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14 D wave contributions Results (K - p Λπ 0 )

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15 P wave and background contributions u and t channel contributions are important ! Results (K - p Λπ 0 )

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16 S and D wave contributions Results ( K - p Σ 0 π 0 )

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17 Results ( K-p Σ 0 π 0 ) P wave and background contributions u and t channel contributions are important !

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18 S wave contributions Further evidences of Σ(1480) are found! Results ( K - p K 0 n)

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19 D wave contributions Results ( K-p K 0 n)

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20 P wave and background contributions Results ( K-p K 0 n) The higher P waves J P =3/2 + are important in the region P_k ~1000 MeV/c

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21 We investigated the K - p reactions with a chiral qua rk model. A successful description of the different ial cross sections and the cross sections at low ene rgy region was obtained. Obvious evidences of Σ(1480) with broad width and Σ(1560) are found in the reactions. The t and u channel contributions are important. The amplitudes of Σ resonances are larger than th e quark model predictions, which implies that the Σ resonances contain q-qbar components. The q-qba r components also exist in Λ(1405). The large coupling of Λ(1520) to KN implies that t he Λ(1520) contains s-sbar components. Summary

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22 Thank you very much!

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