Status of the data analysis on KK pair production

Transcription

1 Status of the data analysis on KK pair production Alexey Dzyuba (PNPI, Gatchina) for the ANKE collaboration Scalar mesons a 0 /f 0 (980) Scientific program ANKE spectrometer pp dk + K 0 pn dk + K - dd 4 HeK + K -

2 Scalar mesons a 0 /f 0 (980) Masses around KK threshold Widths ~ MeV Unknown nature: qq-state ('true' meson) tetraquark KK-molecule Alexey CGSWHP

3 COoler SYnchrotron Protons and deuterons Polarized and unpolarized Momentum up to 3700 MeV/c Internal and external experiments ANKE best kaons identification WASA neutral channels Alexey CGSWHP

4 a 0 /f 0 (980) production at ANKE and WASA Reaction Production Experiment T beam, GeV Status pp d K + K 0 a 0 + =1) ANKE V.Kleber et. at. PRL 91 (2003) 377 Paper accepted pn d K + K - pp pp K + K - 0 f 0 /a 0 =0,1) ANKE 2.65 analysis in progress dd 4 He K + K - f 0 =0) ANKE 2.28 analysis started 4 He π 0 η a 0 0 =0, I fin =1) WASA Alexey CGSWHP

5 a 0 /f 0 (980) production at ANKE and WASA Reaction Production Experiment T beam, GeV Status pp d K + K 0 a 0 + =1) ANKE V.Kleber et. at. PRL 91 (2003) 377 Paper accepted pn d K + K - pp pp K + K - 0 f 0 /a 0 =0,1) ANKE 2.65 analysis in progress dd 4 He K + K - f 0 =0) ANKE 2.28 analysis started 4 He π 0 η a 0 0 =0, I fin =1) WASA Alexey CGSWHP

6 a 0 /f 0 (980) production at ANKE and WASA Reaction Production Experiment T beam, GeV Status pp d K + K 0 a 0 + =1) ANKE V.Kleber et. at. PRL 91 (2003) 377 Paper accepted pn d K + K - pp pp K + K - 0 f 0 /a 0 =0,1) ANKE 2.65 analysis in progress dd 4 He K + K - f 0 =0) ANKE 2.28 analysis started 4 He π 0 η a 0 0 =0, I fin =1) WASA Alexey CGSWHP

7 a 0 /f 0 (980) production at ANKE and WASA Reaction Production Experiment T beam, GeV Status pp d K + K 0 a 0 + =1) ANKE V.Kleber et. at. PRL 91 (2003) 377 Paper accepted pn d K + K - pp pp K + K - 0 f 0 /a 0 =0,1) ANKE 2.65 analysis in progress dd 4 He K + K - f 0 =0) ANKE 2.28 analysis started 4 He π 0 η a 0 0 =0, I fin =1) WASA Alexey CGSWHP

8 Apparatus for Nucleonic and Kaon Ejectiles Alexey CGSWHP

9 pp dk + K Alexey CGSWHP

10 pp dk + K 0 (Tp=2.83 GeV) K 0 dk + coincidence measurements Γ = 27 MeV/c 2 ~2000 ev. Identification via TOF, E and momenta K 0 via missing mass spectrum Background subtraction Kinematical fit ( m(kk)= MeV/c 2 ) ~10% bg Alexey CGSWHP

11 Differential distributions without acceptance corrections CMS q t (kaon) p (proton) k (deutron) (kaon) The transition matrix element under s- and p-waves assumption: M 2 = C 0 k k 2 + C 1 (p k) C 0 q q 2 + C 2 (p q) C 3 (k q) + C 4 (p k)(p q) Alexey CGSWHP

12 Acceptance Corrected Distributions M 2 = C 0 k k 2 + C 1 (p k) 2 + [(KK) S d] P [(KK) P d] S + C 0 q q 2 + C 2 (p q) C 3 (k q) + C 4 (p k)(p q) interference term Coefficients fix partial waves contributions: ~90% [(KK) s d] p (a 0+ -channel) ~10% [(KK) p d] s (only nonresonant) Alexey CGSWHP

13 Acceptance corrected Dalitz plot Alexey CGSWHP

14 Where is the a 0 + (980)? Different contribution (α) of Flatte (width 75 MeV) to [(KK) s d] p Different width of Flatte (α=100%) Alexey CGSWHP

15 Total cross-section pp dk + K 0 Q = 105 MeV : σ tot = (190 ± 4 stat ± 39 sys ) nb Q = 46 MeV : σ tot = (38 ± 2 stat ± 14 sys ) nb V.Kleber et al., PRL 91 (2003) Alexey CGSWHP

16 pn dk + K Alexey CGSWHP

17 pn dk + K - (Tp=2.65 GeV) possible a 0 /f 0 φ(see talk of I. Keshelashvilli) D 2 as an effective neutron target, unobserved «spectator» proton K + K - d coincidence measurements invariant mass spectrum of K + K - system Alexey CGSWHP

18 Rates expected from pp dk + K Alexey CGSWHP

19 Fit of differential distributions cut on M inv (K + K - ) < GeV/c 2 different assumption for M 2 : 1) M 2 = const [(KK) s d] s 2) M 2 as for pp: [(KK) s d] p and [(KK) p d] s 3) (1)+(2) two additional terms (is on this slide) 4) split Q on three part and make the fit (3) Only 4 th has a good χ 2 (< 2/ndf)! Alexey CGSWHP

20 dd 4 HeK + K Alexey CGSWHP

21 dd 4 HeK + K - (Td=2.28 GeV) ANKE@COSY f 0 K + K - N.N. Achasov et al., Phys. Lett. B 88, 367 (1979) C. Harnhard, Phys. Rept. 397, 155 (2004) Alexey CGSWHP

22 dd 4 HeK + K - (Td=2.28 GeV) 4 He selection in coincidence with pions: Setup: 4 weeks of beamtime in April 4 HeK + coincidence d and 4 He 4 He line Energy loss of 4 He in trigger 3 He Difficulties: Huge background Small total number of kaons First analysis: 3 He π ~5000 events 4 He π ~500 events 4 He 4 He after all cuts dk + 4 HeK + ~700 events 30 events Alexey CGSWHP

23 Summary pp dk + K 0 : data analysis is finished dominance of [(KK) s d] p term no evidence of the a 0+ (980) in M inv (KK) pn dk + K - : phi meson dominance σ(pn dk+ K - ) is the same order as σ(pp dk + K 0 ) differential spectra can be discribed by s- and p- waves dd 4 HeK + K 0 : huge background small number of 4 HeK + events Alexey CGSWHP

24 People A.Dzyuba, V.Koptev, S.Mikirtychiants PNPI, Gatchina, Russia M.Büscher, P.Fedorets, C.Hanhart, M.Hartmann, V.Hejny, S.Krewald, Y.Maeda, M.Nekipelov, H.Ströher IKP, FZ Jülich C.Wilkin University of London U.-G.Meiβ ner, V.Kleber, A.Sibirtsev Bonn University L.Kondratyuk, A.Kudryavtsev, V.Tarasov ITEP, Moscow, Russia V.Grishina INR, Moscow, Russia Experiment Theory and the ANKE collaboration This work is supported by DFG and COSY-FFE projects Alexey CGSWHP

25 Checking for the FSI effects Cuts on the dk + and dk invariant mass Alexey CGSWHP

26 Fit Results T p GeV GeV M 2 = C k2 + C (p k) 2 + C q2 + C (p q) 2 + 0k 1 0q 2 symbol squares circles [(KK) S d] P [(KK) P d] S interference + C 3 (k q) + C 4 (p k)(p q) term c 0 q c 0 k 0.89 fixed c 1 c 2 c 3 c 4 χ 2 /ndf ~ ~ Alexey CGSWHP