NKS 2 Meeting 3 charged event KL Kyo

Event selection Data : Jan + Jun(~1509) • Basic cuts – – – One

Finding K+ • Mass of another track can be calculated. • Missing Mass of

Redraw the IM • Basic cuts • 0. 3 < Masstr 3 < 0.

Kinematics of K+L • Momentum of L is calculated by the momenta of proton

Missing mass of target • Basic cuts • 0. 3 < Masstr 3 <

Missing mass of target • Basic cuts • 0. 4 < Masstr 3 <

Energy dependence • Basic cuts • 0. 4 < Masstr 3 < 0. 6

Momentum and angle distributions • • • Basic cuts 0. 4 < Masstr 3

Problems • How to correct the acceptance – Generate K+ and L uniformly and

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NKS 2 Meeting -- 3 charged event (K+L) -- Kyo Tsukada 2007/12/20 1

Finding K+ • Mass of another track can be calculated. • Missing Mass of p(g, L)X can be estimated assuming the proton at rest. K+ • Of course, the fermi momentum of proton should be considered. 2007/12/20 3

Redraw the IM • Basic cuts • 0. 3 < Masstr 3 < 0. 7 Ge. V/c 2 • 0. 3 < MM[p(g, L)X] < 0. 7 Ge. V/c 2 Black : before K+ cut Red : after K+ cut 2007/12/20 4

Kinematics of K+L • Momentum of L is calculated by the momenta of proton and p-. • Momentum of K+ is calculated by a assumption as shown figure. Vertex point of L and X axis PTrack: : calc. Initial. Momentum( pos, dist ) 1. 1 < IM < 1. 13 Ge. V/c 2 （実際には、3次元的に最近接点での傾きを元に導出してます。） 2007/12/20 5

Missing mass of target • Basic cuts • 0. 3 < Masstr 3 < 0. 7 Ge. V/c 2 2007/12/20 6

Missing mass of target • Basic cuts • 0. 4 < Masstr 3 < 0. 6 Ge. V/c 2 2007/12/20 7

Energy dependence • Basic cuts • 0. 4 < Masstr 3 < 0. 6 Ge. V/c 2 • It’s true that K+ disappear in the energy region under the threshold. 0. 35 < MMK+ < 0. 55 Ge. V/c 2 0. 85 < MMp < 0. 95 Ge. V/c 2 2007/12/20 8

Momentum and angle distributions • • • Basic cuts 0. 4 < Masstr 3 < 0. 6 Ge. V/c 2 0. 35 < MMK+ < 0. 6 Ge. V/c 2 0. 85 < MMtarget < 1. 0 Ge. V/c 2 1. 1 < IML < 1. 13 Ge. V/c 2 Background is very small. 2007/12/20 9

Laboratory system 2007/12/20 10

Center of mass system 2007/12/20 11

Problems • How to correct the acceptance – Generate K+ and L uniformly and independently – Laboratory distributions can be corrected. – CM distributions? • How to calculate the polarization of L – Laboratory system ? – The momentum of L should not be used? – In exclusive detection by using NKS 2, it is emphasized that K+ and proton are emitted in the same plane. • How to estimate the contribution of S • How to estimate the contribution of non-strangeness B. G. 2007/12/20 12