Dong Liu State Key Laboratory of Particle Detection and Electronics University of Science and Technology of China ISSP, Erice, 7
Outline Introduction of BESIII experiment Motivation of the study Data sample Event selection Efficiency and correction factor Cross section and form factor Uncertainty Summary ISSP, Erice, 7 D. Liu USTC
BEPCII and BESIII CsI crystal, Δ Ε /Ε =.5% @ GeV σ T = ps barrel, 65 ps endcaps σ p /p=.5% @ GeV, σ de/dx =6% Muon ID: RPCs T Super conducting BESIII ISSP, Erice, 7 D. Liu USTC 3
Motivation: Y(75) BaBar PRD 74. 93 (6) in e / e γφf ( (98) BESII PRL. 3 (8) in J/ψ ηφf ( (98) Y(75) PLB 657 (7) 49 in Flux Tube Model 9.8 3. 67..9 48.7 378
Motivation: precision K F 4 3 F K BaBar PRD 88 (3) 33.5..5..4.6.8 3 3. 3.5.5 3 3.5 4 4.5 5 s (GeV) ISSP, Erice, 7 D. Liu USTC 5 s (GeV)
Motivation: FF e + s γ u F( q ) = d 3 rρ ( r)e iq r - e u s K F 4 3 PRD 88 (3) 33.5..5..4.6.8 3 3. F K = 6πα s ( s) f / s K 3.5.5 3 3.5 4 4.5 5 s (GeV) Phys. Lett. 87B, 359 (979) ISSP, Erice, 7 D. Liu USTC 6
Data samples l Experimental data l MC samples ISSP, Erice, 7 D. Liu USTC 7
Event selection Good charged tracks: (MDC) Vr < cm, Vz < cm, cosθ <.93, N + = N - = cosθ + <.8, cosθ - >-.8 E/p: (EMC+MDC) E/p < (E/p) cut, cut optimized with signal to noise ratio S/ (S+N), cut value ~.6.8 Back to back: (,)>79 TOF: TOF-TOF < 3 ns (TOF) Select -prong event ISSP, Erice, 7 D. Liu USTC 8
Event selection K ± separated from background with momentum E p exp = m K compare p of tracks p of prong process.4. p p p p p e µ π K p.6.5.4 p K p µ σ 3 σ 5 σ.3..8..6.4.9..4.6.8 3 s (GeV) Use momentum to select Kaon..4.6.8 3 ISSP, Erice, 7 D. Liu USTC 9 s (GeV)
- Signal extraction Example at. GeV (GeV/c) p K...9 p in p exp ± 3σ Events / (. GeV ) 3 3 µ =.8736 ±.6 σ =.47 ±. signal = 84. ± 43.9 χ /(-) =.645.8.7 signals.6.6.7.8.9.. (GeV/c) p + K.85.9.95 Signal: MC Gaus Background: MC Gaus σ = N L ε (+ δ ) ISSP, Erice, 7 D. Liu USTC
Efficiency and +δ σ (nb) 4 3 BaBar PRD 88 (3) 33 σ = N L ε (+ δ ) 3 3 4 5 s (GeV) ISSP, Erice, 7 D. Liu USTC
Cross section ISSP, Erice, 7 D. Liu USTC
Cross section σ (nb).5.4 BESIII BABAR 3 BABAR 5 fit.3 m =.98 ±.53 GeV Γ =.437 ±. GeV.. Eur. Phys. J. C 39, 4 54 (5)..4.6.8 3 3. s (GeV) ISSP, Erice, 7 D. Liu USTC 3
Form factor Ø Form factor extraction: 3s' σ F K ( s' ) = KK ( s' ) πα ( ) β K σ KK : dressed cross section; : bare cross section ; : final-state correction β K = 4m K / s C FS Ø Fitting function: F K α s = Aα s s ( ) / s n : strong coupling n theory = n =.94±.9 C FS σ KK s' F K σ KK.4...8.6.4. ( ) = σ KK ( s' ) α ( s' ) α ( ) BESIII preliminary BABAR result fit only BESIII result with s >.38 GeV..4.6.8 3 s ISSP, Erice, 7 D. Liu USTC 4 (GeV)
Form factor ISSP, Erice, 7 D. Liu USTC 5
Uncertainty systematic uncertainty on the K K cross section. E cm (GeV)..5..5.5.75..34.394.3864.396 L.9.9.9.8.9.9.9.9.9.9.9.....3.....3.3 +...3.3.5.3.3.5..4.4 p cut.7 <.. <. <..3.4. <...3 E/p.6.7.5.6.6.6.6.5.6.4.4 open.8.7.8.7.7.7.8.8.7.9. tracking e ciency.9...5.5.6.6.5..7.8 fitting range..7..3...5..6.5.4 signal shape.....3.4.4.5.7.. background shape.4.4.4.4.4.4.4.4.5.5.6 sum.8.6.5.5.5.6.7.6.7.. E cm (GeV).5.6444.6464.7.8.9.95.98 3. 3. 3.8 L.9.9.9.9.9.9.9.9.9.9.9.3.3.3.3.3.4.4.4.4.4.4 +..3.3.3.3.3.3.3.3.3.3 p cut.4.4.5.5.5...5.6.. E/p.6.6.6.4.7.4.4.5.4.5.4 open.8.9.8.9.3.8.9..9.9. tracking e ciency....5.4..3.6.7.7.9 fitting range.3.7.8....3..7.7.8 signal shape.3.7.7..5 3. 3.3 3.4 3.5 3.6 3.9 background shape.6.7.8.. 3. 3.5 3.8 3.9 4. 4.6 sum 3. 3.8.8 3.3 4. 4.7 5. 5.6 6. 6. 8.8 Systematic uncertainty is only a few percent. ISSP, Erice, 7 D. Liu USTC 6!
Summary With momentum and other requirement, the kaon is well separated from background. σ(e + e - à K + K - ) measured with BESIII data are consistent with BaBar experiment. Precision of our result is much precise than previous experiments. From cross section, the form factors of charged kaon are extracted. Both cross section and form factor show clear structure near. GeV. ISSP, Erice, 7 D. Liu USTC 7
Disscussion (MeV) Γ 6 4 PDG: ρ(5) - GAMS: π p ω π n + - BABAR: f (85) π π γ - + - BESIII preliminary: K K - GAMS: π p ω π n + - BABAR: η' π π γ + + + RVUE: π π, K K RVUE: 3(π π ), (π π π ) - + - - (MeV) Γ PDG: φ(7) 4 3 + - BESIII preliminary: K K BESII: J/ ψ η φ f + - BESIII: J/ψ η φ π π BABAR: φ η γ ISR + - BELLE: K K π + π - γ ISR + - - BABAR: K K π + π γ ISR + - BABAR: K K π π γ ISR 5 5 5 M (MeV) M (MeV) ISSP, Erice, 7 D. Liu USTC 8
backup ISSP, Erice, 7 D. Liu USTC 9
Motivation (g-) μ hint of new physics experiments: BaBar, Belle, KLOE, BESIII, SND, CMD a had,lo µ = αm µ 3π sth ds R(s)K(s) s ISSP, Erice, 7 D. Liu USTC
Backup: Momentum spectra Events / (. GeV ) 3 µ =.8736 ±.6 σ =.47 ±. signal = 84. ± 43.9 χ /(-) =.645 Events / (. GeV/c ) µ =.89834 ±.8 5 σ =.45 ±.8 signal = 54. ±.9 χ =.98 Events / (. GeV/c ) 5 µ =.966 ±.6 σ =.437 ±.8 signal = 48.7 ± 38. χ =.596 5.85.9.95.85.9.95.9.95.5 Events / (. GeV/c ).5 3 µ =.946 ±.6 σ =.999 ±.48 signal = 88.7 ± 7.5 χ =.9 Events / (. GeV/c ) 4 3 µ =.95556 ±.44 σ =.486 ±.38 signal = 63. ± 6.3 χ =.64 Events / (. GeV/c ) 5 µ =.96887 ±.4 σ =.539 ±.4 signal = 9. ± 33.9 χ =.647.5 5.9.95.5.95.5..95.5. Events / (. GeV/c ) µ =.9837 ±.6 σ =.463 ±.7 signal = 697.6 ± 4.4 χ =.83 Events / (. GeV/c ) 5 µ =.55 ±.6 σ =.3 ±.55 signal = 63.5 ± 4.4 χ =.76 Events / (. GeV/c ) µ =.4343 ±.6 σ =.3 ±. signal = 8.3 ± 47. χ =.568 5.95.5..5..5.5..5 ISSP, Erice, 7 D. Liu USTC
Backup: Momentum spectra Events / (. GeV/c ) 5 µ =.864 ±.3 5 σ =.63 ±.5 signal = 69.4 ± 36. χ =.57 Events / (. GeV/c ) 4 µ =.955 ±.4 σ =.4 ±.53 signal = 384.7 ± 7.6 χ =.753 Events / (. GeV/c ) 5 µ =.4783 ±. σ =.3 ±.757 signal = 53.4 ± 7.5 χ =.75.5..5..5..5...5..5 Events / (.3 GeV/c ) 5 5 µ =.664 ±.33 σ =.79 ±.86 signal = 7.3 ± 4. χ =.764 Events / (.3 GeV/c ) 5 5 µ =.783 ±.3 σ =.3 ±.53 signal = 45. ± 4.7 χ =.56 Events / (.3 GeV/c ) 5 µ =.5553 ±.83 σ =.844 ±.54 signal =. ± 5. χ =.8..3.4..3.4..3.4 Events / (.3 GeV/c ) 5 µ =.3994 ±.49 σ =.47 ±.67 signal = 8. ± 6.5 χ =.649 Events / (.3 GeV/c ) 4 µ =.3638 ±.9 σ =.3 ±.78 signal = 997.5 ± 58.5 χ =.8 Events / (.3 GeV/c ) 5 µ =.38987 ±.7 σ =.699 ±.84 signal = 65. ±.5 χ =.75.3.4.5.3.4.5.3.4.5 ISSP, Erice, 7 D. Liu USTC
Backup: Momentum spectra Events / (.3 GeV/c ) µ =.459 ±.8 5 σ =.89 ±.79 signal = 87. ±. χ =.63 Events / (.3 GeV/c ) 5 µ =.4595 ±. σ =.67 ±.746 signal = 3.7 ± 8.8 χ =.63 Events / (.3 GeV/c ) 5 µ =.458 ±.9 σ =.4 ±.6 signal = 64.6 ± 3.3 χ =.6.4.5.6.4.5.6.4.5.6 Events / (.3 GeV/c ) 8 µ =.45764 ±.47 6 4 σ =.95 ±.6 signal = 47. ± 7.5 χ =.393 Events / (.3 GeV/c ) µ =.4564 ±.3 5 σ =.3 ±.8 signal = 364.6 ± 37. χ =.588 5.4.5.6.4.5.6 ISSP, Erice, 7 D. Liu USTC 3
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