| 1. |
- Asano, H., et al.
(author)
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Spectroscopic study of the Λ(1405) resonance via the d (K-, n) reaction at J-PARC
- 2019
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In: 13th International Conference on Hypernuclear and Strange Particle Physics, HYP 2018. - : AIP Publishing. - 9780735418721 ; 2130
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Conference paper (peer-reviewed)abstract
- The structure of the Λ(1405) hyperon is an important and long-standing issue related to the K̄-nucleus interaction. The J-PARC E31 experiment has been performed to investigate the Λ(1405) spectrum shape. Because it is hard to form the Λ(1405) directly by a K̄N scattering in free space, E31 uses the d(K-, n) reaction with an incident kaon momentum of 1 GeV/c. We will identify three final states - ς-π+, ς+π-, ς0π0-so that the isospin structure of hyperon resonance states produced can be decomposed. The first physics run of the E31 experiment was performed in 2016. To enhance the statistics of the data set, we have performed the second physics run in the beginning of 2018. During the second run of E31, around 3.9×1010 kaons impacted on the deuteron target.
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| 2. |
- Biernat, Jacek, et al.
(author)
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Hyperon Structure and Decay with BESIII
- 2019
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In: 13th international conference on hypernuclear and strange particle physics (HYP2018). - : AMER INST PHYSICS. - 9780735418721
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Conference paper (peer-reviewed)abstract
- In these proceedings, we report on the Lambda hyperon structure and decay, studied through two different processes: i) the resonant e(+)e(-) -> J/psi -> Lambda(Lambda) over bar, using a data sample of 1.31 x 10(9) J/psi events and ii) the non -resonant e(+)e(-) -> gamma* > Lambda(Lambda) over bar, using a 66.9 pb(-1) data sample collected at root s = 2.396 GeV. In e(+)e(-) -> J/psi -> Lambda(Lambda) over bar, the phase between the hadronic form factors is measured for the first time to be 42.3 degrees +/- 0.6 degrees +/- 0.5 degrees. The large data sample enabled a multi-dimensional analysis and hence a model-independent measurement of the decay parameters for Lambda -> p pi(-) (alpha(-)), Lambda(Lambda) over bar -> (p) over bar pi(+) (alpha(+)) and (Lambda) over bar -> (n) over bar pi(0) ((pi) over bar (0)). The value obtained, alpha(-) = 0.750 +/- 0.009 +/- 0.004, differs with 50- from the PDG value. The simultaneous measurement for the A, i.e. alpha(+) = 0.758 +/- 0.010 +/- 0.007, allows for the most precise test of CP violation in A decays so far: A(CP) = (alpha(-) + alpha(+))/(alpha(-) - alpha(+)) of -0.006 +/- 0.012 +/- 0.007. Furthermore, the decay asymmetry (kappa) over bar (0) = 0.692 0.016 0.006 is measured for the first time. The large data sample at Ars = 2.396 GeV of the e+ > AA reaction enabled the first complete measurement of the time-like electric and magnetic form factors GE and GM of any baryon. This includes the modulus of the ratio R = vertical bar G(E)/G(M)vertical bar and the relative phase, Delta Phi = Phi(E) - Phi(M). Using the decay asymmetry parameters from the J/psi data as input, the obtained values of R and Delta Phi are R = 0.96 +/- 0.14 +/- 0.02 and Delta Phi = 37 degrees +/- 12 degrees +/- 6 degrees, respectively. In addition, the cross section has been measured to unprecedented precision too sigma = 119.0 +/- 5.3 +/- 5.1 pb, corresponding to an effective form factor value of vertical bar G vertical bar = 0.123 +/- 0.003 +/- 0.003.
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