1 / 21

Exclusive  +  –  +  – and  +  0  –  0 production in two photon

Exclusive  +  –  +  – and  +  0  –  0 production in two photon collisions at LEP. O. Fedin, S. Nesterov, G. Sultanov, I. Vorobiev representing the L3 collaboration. April, 23-27 DIS 2003. e + e –  e + e –  +  –  +  – e + e –  e + e –  +  0  –  0.

gordon
Download Presentation

Exclusive  +  –  +  – and  +  0  –  0 production in two photon

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Exclusive  + – + –and  + 0 – 0 production in two photon collisions at LEP O. Fedin, S. Nesterov, G. Sultanov, I. Vorobiev representing the L3 collaboration April, 23-27 DIS 2003 Exclusive +–+– and +0–0production in two photon collision at L3 (page 1)

  2. e+e–  e+e– + – + – e+e–  e+e–  + 0 – 0 Outline • Exclusive r 0r 0and r +r –production at Q2 0 • Exclusive r 0r 0 production for 1.2 < Q2 < 30 GeV2[Subm. to Phys. Lett.] •  + – + – and + 0 – 0 at W> 2.4 GeV Exclusive +–+– and +0–0production in two photon collision at L3 (page 2)

  3. Exclusive r 0r 0production at Q2 0 • high energy data (161 < s < 208 GeV), integrated luminosity 686.7 pb-1 • e+e–  e+e– + – + – • 4 tracks with zero charge • no photons • dE/dx CL(4) > 6% • e+e–  e+e–  + 0 – 0 • two tracks with zero charge • dE/dx CL(2) > 6% • 4 photons E > 100 MeV • two best  0 from constraintfit • p2t(4) < 0.02 GeV2 Sample of  + – + – — 69542 events (66838 in 1.0 < W<3.0 GeV) Sample of  + 0 – 0—5253 events (4740 in 1.0 < W  < 3.0 GeV) Exclusive +–+– and +0–0production in two photon collision at L3 (page 3)

  4. Efficiency and detector acceptance Detector acceptance and selection efficiency  determined from MC (EGPC generator[F.Linde, PhD Thesis, 1988] ) • Trigger efficiency calculated from the data: • 91.8% for  + – + – • 51.8% for + 0 – 0 Exclusive +–+– and +0–0production in two photon collision at L3 (page 4)

  5. Two pion mass spectra Exclusive +–+– and +0–0production in two photon collision at L3 (page 5)

  6. Partial Wave Analysis method • Performed in 1.0 < Wgg < 3.0 GeV • Model with rrin different spin-parity states and isotropic 4p[M.Althoff et al. Z.Phys. C16, 1982] • Arr BW12BW34JPJz+ perm. • A4p 1 • rr(JP,Jz) = (0+, 0), (2+, 2), (0–, 0), (2+, 0), (2–, 0(1,2)) and 4p isotropic, no interference, significant rr only 0+ and (2+, 2); 4pisotropic is effective background • MC integration of |Arr|2 • Likekihood fit to the data in each Wggbin Exclusive +–+– and +0–0production in two photon collision at L3 (page 6)

  7. Fit results for • M(p +p –) and M(p p 0) M(p +p –) spectrum M(p p 0) spectrum Exclusive +–+– and +0–0production in two photon collision at L3 (page 7)

  8. Fit results for • Angle of pion in C.M.S. of r with respect to the beam axis (Adair angle) angle of p + in r 0CMS angle of p  in rCMS Exclusive +–+– and +0–0production in two photon collision at L3 (page 8)

  9. Cross section for   • Total  and dominant partial waves cross sections • Isospin ratio of the  cross section is incompatible with I=0, 1 Exclusive +–+– and +0–0production in two photon collision at L3 (page 9)

  10. Cross section for   Broad enhancement near threshold of    Exclusive +–+– and +0–0production in two photon collision at L3 (page 10)

  11. Exclusive r0r0production for 1.2 < Q2 < 30 GeV2 • Single tage+e– e+e–taggg*  e+e–tagr 0r 0 • tagged electron 25 mrad <  < 68 mrad • p2t (etagp+p–p+p –) < 0.2 GeV2 • Etag> 80% Ebeam  Z-pole (s  91 GeV) 1.2 < Q 2 < 8.5 GeV2, Le+e– = 148.7 pb-1  high energy data (s  195 GeV) 8.8 < Q 2 < 30 GeV2, L e+e– = 706.0 pb-1  at Z-pole sample of 851 events withWgg > 1 GeV  at high energy sample of 498 events with Wgg > 1 GeV Exclusive +–+– and +0–0production in two photon collision at L3 (page 11)

  12. M( + –) spectrum Exclusive +–+– and +0–0production in two photon collision at L3 (page 12)

  13. Box method[D.M.Schmidt et al. NIM A328(1993)] • 2 million MC events for channel • * 0 0 • * 0 + – • * + – + – • Likelihood fit to thedata Exclusive +–+– and +0–0production in two photon collision at L3 (page 13)

  14. Fit results for 0 0 • M( + –) in different Q2 and Wregions Points represent the data, histogram shows fit results, hatched area shows  0 0 component Exclusive +–+– and +0–0production in two photon collision at L3 (page 14)

  15. Fit results for 0 0 • Production angle and angle between decay planes Points represent the data, histogram shows fit results, hatched area shows  0 0 component Exclusive +–+– and +0–0production in two photon collision at L3 (page 15)

  16. Cross section of *  0 0 Z-pole data High energy data • Broad enhancement near threshold of gg  r0r0as seen in measurements at Q2  0 • Interval 1.1 < Wgg < 3.0 GeV is chosen for Q2-dependence Exclusive +–+– and +0–0production in two photon collision at L3 (page 16)

  17. Cross section of *  0 0 • Fit with 1/(Qn(Q2+<W>2)2) • n = 2.4  0.3(<W> = 1.945) • Agrees with QCD expectation n= 2 [M.Diehl et al. PRD 62 073014] • Agrees well with GVDM form • factor,r-pole is not sufficient Exclusive +–+– and +0–0production in two photon collision at L3 (page 17)

  18. High Wtwo pion mass spectra M= 763  4 GeV  = 170  21 GeV Mf2 = 1282  15 GeV f2 = 273  130 GeV M = 1738  19 GeV  = 130  61 GeV • (770), f2(1270),  (1700) are clearly seen Exclusive +–+– and +0–0production in two photon collision at L3 (page 18)

  19. Breit-Wigner fit for high W M= 763  4 GeV  = 170  21 GeV Mf2 = 1282  15 GeV f2 = 273  130 GeV Exclusive +–+– and +0–0production in two photon collision at L3 (page 19)

  20. Summary • Exclusive rrproduction at Q2 0 • Dominance of(JP, Jz) = (2+, 2) spin-parity state • Broad enhancement of rr near threshold • Cross section ratio s(r0r0)/s(r+r-) is incompatible with isospin I=0,1 • Exclusive r0r0 production at high Q2 • Broad enhancement of rrnear threshold as for Q2 ~ 0 • Good agreement with the QCD expectation for differential cross section ds e+e-/dQ2 • GDVM form factor describes well Q2 dependence of sgg • Measurements of the sgg at Q2 ~ 0 and for Q2 > 1.2 GeV are consistent • Low and high Q2 data are consistent with the same QCD prediction • High Wggregion • In  + – + –(770), f2 (1270) and (1700) are clearly seen • In  + 0 – 0(770) and f2 (1270) are seen Exclusive +–+– and +0–0production in two photon collision at L3 (page 20)

  21. Cross section    + – + –  Comparison of total   + –+ – cross section Exclusive +–+– and +0–0production in two photon collision at L3 (page 21)

More Related