Exclusive + – + – and + 0 – 0 production in two photon
description
Transcript of Exclusive + – + – and + 0 – 0 production in two photon
April, 23-27DIS 2003
Exclusive +–+– and +0–0 production in two photon collision at L3 (page 1)
O. Fedin PNPI, Russia
Exclusive + – + – and + 0 – 0
production in two photon
collisions at LEP
Exclusive + – + – and + 0 – 0
production in two photon
collisions at LEP
O. Fedin, S. Nesterov, G. Sultanov, I. Vorobievrepresenting the L3 collaboration
April, 23-27 DIS 2003
April, 23-27DIS 2003
Exclusive +–+– and +0–0 production in two photon collision at L3 (page 2)
O. Fedin PNPI, Russia
Outline e+e– e+e– + – + – e+e– e+e– + 0 – 0
Exclusive and –production at Q2
0
Exclusive production for
1.2 < Q2 < 30 GeV2 [Subm. to Phys. Lett.]
+ – + – and + 0 – 0 at W > 2.4 GeV
April, 23-27DIS 2003
Exclusive +–+– and +0–0 production in two photon collision at L3 (page 3)
O. Fedin PNPI, Russia
Exclusive production 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 constraint fit
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)
April, 23-27DIS 2003
Exclusive +–+– and +0–0 production in two photon collision at L3 (page 4)
O. Fedin PNPI, Russia
Efficiency and detector acceptance
Trigger efficiency calculated from the data: 91.8% for + – + –
51.8% for + 0 – 0
Detector acceptance and selection efficiency determined from MC (EGPC generator [F.Linde, PhD Thesis, 1988] )
April, 23-27DIS 2003
Exclusive +–+– and +0–0 production in two photon collision at L3 (page 5)
O. Fedin PNPI, Russia
Two pion mass spectra
April, 23-27DIS 2003
Exclusive +–+– and +0–0 production in two photon collision at L3 (page 6)
O. Fedin PNPI, Russia
Partial Wave Analysis methodPerformed in 1.0 < WGeV
Model with in different spin-parity states and isotropic 4M.Althoff et al. Z.Phys. C16, 1982]
*ABW12BW34JPJz+ perm.* A4
JP,Jz) = (0+, 0), (2+, 2), (0–, 0), (2+, 0), (2–, 0(1,2)) and 4 isotropic, no interference, significant only 0+ and (2+, 2); 4isotropic is effective background
MC integration of |A|2
Likekihood fit to the data in each Wbin
April, 23-27DIS 2003
Exclusive +–+– and +0–0 production in two photon collision at L3 (page 7)
O. Fedin PNPI, Russia
Fit results for
• M– and M
M–spectrum Mspectrum
April, 23-27DIS 2003
Exclusive +–+– and +0–0 production in two photon collision at L3 (page 8)
O. Fedin PNPI, Russia
Fit results for •Angle of pion in C.M.S. of with respect to the beam axis (Adair angle)
angle of in CMS angle of in CMS
April, 23-27DIS 2003
Exclusive +–+– and +0–0 production in two photon collision at L3 (page 9)
O. Fedin PNPI, Russia
Cross section for
• Total and dominant partial waves cross sections• Isospin ratio of the cross section is incompatible with I=0, 1
April, 23-27DIS 2003
Exclusive +–+– and +0–0 production in two photon collision at L3 (page 10)
O. Fedin PNPI, Russia
Cross section for
Broad enhancement near threshold of
April, 23-27DIS 2003
Exclusive +–+– and +0–0 production in two photon collision at L3 (page 11)
O. Fedin PNPI, Russia
Exclusive production for 1.2 < Q2 < 30 GeV2
Single tag e+e– e+e–tag e+e–
tag
*tagged electron 25 mrad < < 68 mrad
*p2t (etag––) < 0.2 GeV2
*Etag > 80% Ebeam
Z-pole (s 91 GeV) 1.2 < Q 2 < 8.5 GeV2, L e+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 with WGeV at high energy sample of 498 events with W > GeV
April, 23-27DIS 2003
Exclusive +–+– and +0–0 production in two photon collision at L3 (page 12)
O. Fedin PNPI, Russia
M( + –) spectrum
April, 23-27DIS 2003
Exclusive +–+– and +0–0 production in two photon collision at L3 (page 13)
O. Fedin PNPI, Russia
Box method [D.M.Schmidt et al. NIM A328(1993)]
2 million MC events for channel
* 0 0
* 0 + –
* + – + –
Likelihood fit to the data
April, 23-27DIS 2003
Exclusive +–+– and +0–0 production in two photon collision at L3 (page 14)
O. Fedin PNPI, Russia
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
April, 23-27DIS 2003
Exclusive +–+– and +0–0 production in two photon collision at L3 (page 15)
O. Fedin PNPI, Russia
• Production angle and angle between decay planes
Points represent the data, histogram shows fit results, hatched area shows 0 0 component
Fit results for 0 0
April, 23-27DIS 2003
Exclusive +–+– and +0–0 production in two photon collision at L3 (page 16)
O. Fedin PNPI, Russia
Cross section of * 0 0
Z-pole data High energy data
• Broad enhancement near threshold of as seen in measurements at Q2 0
• Interval 1.1 < W< 3.0 GeV is chosen for Q2-dependence
April, 23-27DIS 2003
Exclusive +–+– and +0–0 production in two photon collision at L3 (page 17)
O. Fedin PNPI, Russia
Agrees well with GVDM form factor, pole is not sufficient
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]
Cross section of * 0 0
April, 23-27DIS 2003
Exclusive +–+– and +0–0 production in two photon collision at L3 (page 18)
O. Fedin PNPI, Russia
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
April, 23-27DIS 2003
Exclusive +–+– and +0–0 production in two photon collision at L3 (page 19)
O. Fedin PNPI, Russia
Breit-Wigner fit for high W
M = 763 4 GeV
= 170 21 GeV
Mf2 = 1282 15 GeV
f2 = 273 130 GeV
April, 23-27DIS 2003
Exclusive +–+– and +0–0 production in two photon collision at L3 (page 20)
O. Fedin PNPI, Russia
SummaryExclusive production at Q2
* Dominance of(JP, Jz) = (2+, 2) spin-parity state * Broad enhancement of near threshold* Cross section ratio is incompatible with isospin
I=0,1Exclusive production at high Q2
* Broad enhancement of near threshold as for Q2 ~ * Good agreement with the QCD expectation for differential cross
section de+e/dQ2
* GDVM form factor describes well Q2 dependence of
* Measurements of the at Q2 ~ and for Q2 > 1.2 GeV are consistent
* Low and high Q2 data are consistent with the same QCD prediction
High Wregion
* In + – + – (770), f2 (1270) and (1700) are clearly seen* In + 0 – 0 (770) and f2 (1270) are seen
April, 23-27DIS 2003
Exclusive +–+– and +0–0 production in two photon collision at L3 (page 21)
O. Fedin PNPI, Russia
Cross section + – + –
Comparison of total + –+ – cross section