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Xian-Hui ZhongXian-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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New data from Crystal Ball

The recent measurements of K-pneutrals reactions at crystal ball 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, 015205 (2008); S. Prakhov at el, 0812.1888

The S=-1 baryon spectrum is still not well established, such as the quantum numbers of Σ(1480,1560,1670,1690) (bumps) in PDG are still unknown.

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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, PRC79,045202(2009)

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Chiral quark modelQuark-meson couplings

For pseudoscalar-mesons:

For vector-mesons:

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Chiral quark modelThe possible resonances in the reactions according to the quark model

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Chiral quark modelThe 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, PRC79,045202(2009)

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ResultsResonance parameters

There are very low mass S wave states Σ(1480,1560) !

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Results

couplings

large couplings of Σ resonances to Λπ are needed, large coupling 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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Total cross sections

Results

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Results (K-pΛπ0)Differential cross sections

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Differential cross sections

Results (K-pΣ0π0)

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Differential cross sections

Results (K-pK0n)

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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-pΛπ0)

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D wave contributions

Results (K-pΛπ0)

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P wave and background contributions

u and t channel contributions are important !

Results (K-pΛπ0)

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S and D wave contributions

Results ( K-pΣ0π0)

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Results ( K-pΣ0π0)P wave and background contributions

u and t channel contributions are important !

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S wave contributions

Further evidences of Σ(1480) are found!

Results ( K-pK0n)

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D wave contributions

Results ( K-pK0n)

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P wave and background contributions

Results ( K-pK0n)

The higher P waves JP=3/2+ are important in the region P_k~1000 MeV/c

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• We investigated the K-p reactions with a chiral quark model. A successful description of the differential cross sections and the cross sections at low energy 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 the quark model predictions, which implies that the Σ resonances contain q-qbar components. The q-qbar components also exist in Λ(1405).

• The large coupling of Λ(1520) to KN implies that the Λ(1520) contains s-sbar components.

Summary

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Thank you very much!