Scalar meson photoproduction

Transcription

1 Scalar eson photoproduction Šukasz Bibrzycki H. Niewodnicza«ski Institute of Nuclear Physics PAN, Cracow, Poland Nov. 11, 29 Š. Bibrzycki (IFJ PAN) Scalar eson photoproduction Nov. 11, 29 1 / 2

2 Outline 1 Why study scalar esons in the photoproduction? 2 Partial wave analysis of eson-eson photoproduction 3 Model description 4 Results for γp K + K p 5 Results for γp π + π p 6 Suary and outlook Š. Bibrzycki (IFJ PAN) Scalar eson photoproduction Nov. 11, 29 2 / 2

3 Nonet assignent of scalar esons - various scenarios (incoplete list) 1st scenario (Asler, Close '95; Anisovich '95) Meson Isospin Coposition σ(6) ππ, qqqq 1 κ(8) Kπ, qqqq 2 a (98) 1 K K, qqqq f (98) K K, qqqq f (137) dd + uu 1 K (143) us, ds, su, sd 2 a (145) 1 dd, du, dd uu f (171) ss or f (15)?? Q1: Why the surplus of isoscalars? Q2: Is the f (15) a glueball? Š. Bibrzycki (IFJ PAN) Scalar eson photoproduction Nov. 11, 29 3 / 2

4 Nonet assignent ctd. A1: No denite answer but the ixing of the isoscalars in the ass range MeV with the ground-state glueball akes a clue. A2: The f (15) is unlikely a pure glue. The glueball should decay into ππ, ηη, ηη and K K with relative ratios 3:1::4 which is contradicted by easureents. Ground state glueball ass in quenched LQCD is estiated around 16 MeV. However, unquenched LQCD calculations iply the uch lower ass of the glueball 1 GeV, which akes the ixing with higher ass isoscalars probleatic. Š. Bibrzycki (IFJ PAN) Scalar eson photoproduction Nov. 11, 29 4 / 2

5 Nonet assignent ctd. 2nd scenario (Narison '6) σ(6), κ(8), a (98), f (98) - create a qq nonet which is coupled to the low ass glueball f (137), f (15) and f (171) are then 2 3 P radial excitations with signicant glueball ixing Other scenarios are conceivable with predictions strongly dependent on: ixing details, ground state glueball ass. Š. Bibrzycki (IFJ PAN) Scalar eson photoproduction Nov. 11, 29 5 / 2

6 Nonet assignent ctd. Electroagnetic processes: predictions for the radiative decays (both V Sγ and S V γ) strongly discriinate aong various nonet assignent scenarios, precise easureents of the radiative decay widths are necessary, studies of the scalar eson photoproduction can be an alternative. Donnachie, Kalashnikova '8 Š. Bibrzycki (IFJ PAN) Scalar eson photoproduction Nov. 11, 29 6 / 2

7 E ective π + π ass distributions in γ p π + π p Early experients: Balla '72 (SLAC), Struczinski '76 (DESY) Mass spectru doinated by vector esons (ρ(77) in the π + π channel and φ(12) in the K + K channel) σ/dm S 2 + P P 2 + P d No indication of the S -wave resonances in the ass spectru. Bibrzycki (IFJ PAN) Scalar eson photoproduction Nov. 11, 29 7 / 2

8 Model description - production echaniss a) diractive photoproduction of the vector esons, =K ±, π ±, γ IP φ/ b) S-wave photoproduction of the K + K and π + π pairs with the t-channel ρ and ω exchange plus nal state interactions leading to dynaical scalar resonance generation; c=π, K, ϱ, ω, K ; =π ±, π, K ±, K, c) diractive Drell echanis, (for M pπ >2 GeV), γ γ p p c ρ/ω p p π π+ π T d) resonant Drell echanis ( ), (for M pπ <2 GeV). p p γ π π + π + ++ p p Š. Bibrzycki (IFJ PAN) Scalar eson photoproduction Nov. 11, 29 8 / 2

9 Söding odel revisited Drell aplitudes are included in the odel to account for the ρ ass distribution asyetry. The asyetry is due to the interference of the Drell aplitudes and direct ρ photoproduction aplitudes. Š. Bibrzycki (IFJ PAN) Scalar eson photoproduction Nov. 11, 29 9 / 2

10 Söding odel revisited In the Balla analyses based on the Söding odel the interediate production aplitude A Drell was added incoherently and the S-wave aplitude was neglected: W Balla (θ, φ) A ρ + A di Drell 2 + A Drell 2. Our odel: W (θ, φ) A ρ + A di Drell + A Drell + A S 2 Š. Bibrzycki (IFJ PAN) Scalar eson photoproduction Nov. 11, 29 1 / 2

11 Partial wave analysis M ππ [GeV] Moents of the angular distribution YM L = dωy L M (Ω)W (cos θ, φ). Soe structures observable in the Y 1 oent are not explicable in the Söding odel (solid line). Hints of the interference with the resonant S wave (σ, f (98)). Š. Bibrzycki (IFJ PAN) Scalar eson photoproduction Nov. 11, / 2

12 S-wave aplitude - iportant notes γ S ρ/ω p p Instead of using a point-like γvs vertex... Š. Bibrzycki (IFJ PAN) Scalar eson photoproduction Nov. 11, / 2

13 S-wave aplitude - iportant notes γ S ρ/ω p p Instead of using a point-like γvs vertex... γ c ρ/ω p p T...we assue the scalar eson to be dynaically generated in the nal state. Š. Bibrzycki (IFJ PAN) Scalar eson photoproduction Nov. 11, / 2

14 S-wave aplitude - iportant notes γ S ρ/ω p p Instead of using a point-like γvs vertex... Justication: γ c ρ/ω p p T...we assue the scalar eson to be dynaically generated in the nal state. at least the structure of σ and f (98) sees to be olecular-like, iportant data fro ππ and K K scattering (phase shifts, inelasticities) ebedded in the FSI transition atrix, any channels in the interediate and nal states described siultaneously by the coupled channel foralis, unitarity and analyticity contraints respected in the eson-eson aplitudes. Š. Bibrzycki (IFJ PAN) Scalar eson photoproduction Nov. 11, / 2

15 Results for γp K + K p dσ/dt [µb/gev 2 ] Cross section and oents of the angular distribution YM L / Y, DESY data (Behrend et al, '78) dσ/dt P *BR dσ/dt S 1-3,1,2,3,4 -t (GeV 2 ) φ µb/gev ,4,2 -,2 -,4 -,6 dσ/dm KK,4 <Y 1 >/<Y >,4 <Y1 1 >/<Y > 1, 1,2 1,4 M KK (GeV),2 -,2 -,4 -,6,2 -,2 -,4 -,6 1, 1,2 1,4 M KK (GeV),2 -,2 -,4 -,6 <Y 2 >/<Y >,4 <Y2 1 >/<Y >,4 <Y2 2 >/<Y >,2 -,2 -,4 -,6 1, 1,2 1,4 M KK (GeV) Also Daresbury data (Barber et al. '82) were properly described by the odel of Š.B., L.Le±niak, A.Szczepaniak, Eur. Phys. J. C34, 335 (24). Š. Bibrzycki (IFJ PAN) Scalar eson photoproduction Nov. 11, / 2

16 Results for γp K + K p Cross sections [nb] Daresbury (E γ =4 GeV) DESY (E γ =5.65 GeV) t ax 1.5 GeV 2.2 GeV 2 M KK range (.997,1.42) GeV (1.1,1.3) GeV S-wave exp. 96.2±2. 2.7±1.5 S-wave theor P -wave theor P-(all helicities) exp. 226±9 123±1 P-(all helicities) theor ± ± 9.4 Large discrepancy for the S-wave cross sections between two exp. analyses. According to our odel the S-wave K + K photoproduction cross section is equal to (2-5)% of the total cross section for the reaction γp φp K + K p. Š. Bibrzycki (IFJ PAN) Scalar eson photoproduction Nov. 11, / 2

17 Results for γp π + π p Cross section dσ/dt - coparison of the SLAC data (Balla '72) and odel predictions at E γ =4.7 GeV dσ/dt [µb/gev 2 ] Balla f ρ Drell-diff. Drell- su,1,1,2,3,4,5,6,7,8,9 1 -t [GeV 2 ] Š. Bibrzycki (IFJ PAN) Scalar eson photoproduction Nov. 11, / 2

18 Results for γp π + π p (Eγ=4.7 GeV) π + π ass distribution for.2< t<.5 GeV Y 2 oent for.2< t<.4 GeV 2 dσ/dtdm ππ [µb/gev 3 ] f ρ ρ-drell int. su,4,6,8 1 1,2 1,4 M ππ [GeV] <Y 2 > [events/4 MeV] S+P+D+F all waves,4,6,8 1 1,2 1,4 1,6 1,8 M ππ [GeV] Š. Bibrzycki (IFJ PAN) Scalar eson photoproduction Nov. 11, / 2

19 Results for γp π + π p <Y 1 > [events/4 MeV] oent Y 1 (Balla '72) for.2< t<.4 GeV 2 and odel predictions (E γ =4.7 GeV) sall statistics large errors all waves f +ρ S+P+D+F f (98),4,6,8 1 1,2 1,4 1,6 1,8 M ππ [GeV] oents Y 1 and Y 1 1 for.5< t<.6 GeV 2 and energy E γ =3.5 GeV Battaglieri et al., (CLAS), PRL 12, 121, 29 - rst observation of the f (98) in photoproduction! Š. Bibrzycki (IFJ PAN) Scalar eson photoproduction Nov. 11, / 2

20 Results for γp π + π p Integrated photoproduction cross sections in the eective ass range.93<m ππ <1.3 GeV (f (98) range) for E γ =4.7 GeV Reaction echanis γp π + π p Cross section [nb] f (98) photoproduction 75 Resonant Drell echanis ( ) 1 f Drell interference -7 Diractive Drell echanis 1 3 S-wave - all echaniss 69 All waves 6 Total experiental ρ photoproduction cross section σ(γp ρ p)=(15.2±1.4) 1 3 nb (Balla '72) The integrated S-wave cross section of the π + π photoproduction in the ass range of f (98): equals to.5% of the total ρ photoproduction cross section. Š. Bibrzycki (IFJ PAN) Scalar eson photoproduction Nov. 11, / 2

21 Suary Although the S-wave cross section is sall for both K + K and π + π channels, the ipact of the S-wave is observed in the data. The eect is ore visible in the recent CLAS data due to uch larger statistics. First observation of the f (98) in the photoproduction! Š. Bibrzycki (IFJ PAN) Scalar eson photoproduction Nov. 11, / 2

22 Outlook The odel ay be suitable for: further analyses of CLAS data, COMPASS, GlueX. Model we used to describe the FSI in the photoproduction can be transferred to the description of heavy eson decays: (J/ψ, B, D...) into hadronic nal states. Š. Bibrzycki (IFJ PAN) Scalar eson photoproduction Nov. 11, 29 2 / 2