Formation of the $eta_c$ in two photon collisions at LEP

The two-photon width Γ γγ of the η c meson has been measured with the L3 detector at LEP. The η c is studied in the decay modes π + π − π + π − , π + π − K + K − , K 0 s K ± π ∓ , K + K − π 0 , π + π − η , π + π − η ′, and ρ + ρ − using an integrated luminosity of 140 pb −1 at s ≃91 GeV and of 52 pb −1 at s ≃183 GeV. The result is Γ γγ (η c )=6.9±1.7 stat ±0.8 sys ±2.0 (BR) keV. The Q 2 dependence of the η c cross section is studied for Q 2 <9 GeV 2 . It is found to be better described by a Vector Meson Dominance model form factor with a J-pole than with a ρ -pole. In addition, a signal of 29±11 events is observed at the χ c0 mass. Upper limits for the two-photon widths of the χ c0 , χ c2 , and η c ′ are also given.

electron positron: colliding beams
exchange: two-photon
photon photon: interaction
eta/c(2980): photoproduction
eta/c(2980): hadronic decay
eta/c(2980): width
channel cross section: momentum transfer
mass spectrum
vector dominance
form factor: pole

References(30)

Figures(6)

The Two photon particle production mechanism. Physical problems. Applications. Equivalent photon approximation

V.M. Budnev
(
- Sobolev IM, Novosibirsk
)
,
I.F. Ginzburg
(
- Sobolev IM, Novosibirsk
)
,
G.V. Meledin
(
- Sobolev IM, Novosibirsk
)
,
V.G. Serbo
(
- Sobolev IM, Novosibirsk
)

- Phys.Rept. 15 (1975) 181-281
•
DOI:
- 10.1016/0370-1573(75)90009-5

On the angular momentum of a system of two photons

L.D. Landau
(
- Moscow, Inst. Phys. Problems
)

- Dokl.Akad.Nauk SSSR 60 (1948) 2, 207-209
•
DOI:
- 10.1016/B978-0-08-010586-4.50070-5

Selection Rules for the Dematerialization of a Particle Into Two Photons

Chen-Ning Yang
(
- Chicago U., EFI
)

- Phys.Rev. 77 (1950) 242-245,
- In *Yang, C.N.: Selected Papers 1945-1980*, 127-130
•
DOI:
- 10.1103/PhysRev.77.242

Observation of an eta(c)-prime Candidate State with Mass 3592-MeV +- 5-MeV

et al.

- Phys.Rev.Lett. 48 (1982) 70
•
DOI:
- 10.1103/PhysRevLett.48.70

A Search for $\eta'_c$ Production in Photon-Photon Fusion at LEP

DELPHI

Collaboration

•

P. Abreu

et al.

- Phys.Lett.B 441 (1998) 1-4, 479-490
•
e-Print:
- hep-ex/9810030
•
DOI:
- 10.1016/S0370-2693(98)01300-8

Two photon widths of singlet positronium and quarkonium with arbitrary total angular momentum

E.S. Ackleh
(
- Tennessee U.
)
,
Ted Barnes
(
- Oak Ridge and
- Tennessee U.
)

- Phys.Rev.D 45 (1992) 232-240
•
DOI:
- 10.1103/PhysRevD.45.232

The Decay eta(c) ---> gamma gamma: A Test for potential models

- Phys.Rev.D 51 (1995) 141-146
•
e-Print:
- hep-ph/9401315
•
DOI:
- 10.1103/PhysRevD.51.141

Two photon decays of mesons in a relativistic quark model

Claus R. Munz
(
- Bonn U.
)

- Nucl.Phys.A 609 (1996) 364-376
•
e-Print:
- hep-ph/9601206
•
DOI:
- 10.1016/S0375-9474(96)00265-5

Pseudoscalar heavy quarkonium decays with both relativistic and QCD radiative corrections

Kuang-Ta Chao
(
- CCAST World Lab, Beijing and
- Peking U.
)
,
Han-Wen Huang
(
- Peking U.
)
,
Jing-Hua Liu
(
- Peking U.
)
,
Jian Tang
(
- Peking U.
)

- Phys.Rev.D 56 (1997) 368-376
•
e-Print:
- hep-ph/9601381
•
DOI:
- 10.1103/PhysRevD.56.368

A Perturbative approach to the eta(c) gamma transition form-factor

Thorsten Feldmann
(
- Wuppertal U.
)
,
Peter Kroll
(
- Wuppertal U.
)

- Phys.Lett.B 413 (1997) 410-415
•
e-Print:
- hep-ph/9709203
•
DOI:
- 10.1016/S0370-2693(97)01120-9

Meson photon transition form-factors and resonance cross-sections in e+ e- collisions

G.A. Schuler
(
- CERN
)
,
Frits A. Berends
(
- CERN and
- Leiden U.
)
,
R. van Gulik
(
- Leiden U.
)

- Nucl.Phys.B 523 (1998) 423-438
•
e-Print:
- hep-ph/9710462
•
DOI:
- 10.1016/S0550-3213(98)00128-X

Measurement of eta(c) production in untagged two photon collisions at LEP

L3

Collaboration

•

O. Adriani

et al.

- Phys.Lett.B 318 (1993) 575-582,
- Phys. Lett. B318 (1993) 575-582. and CERN Geneva - CERN-PPE-93-173 (93/09,rec.Feb.94) 17 p
•
DOI:
- 10.1016/0370-2693(93)91558-5

Review of particle physics. Particle Data Group

et al.

- Eur.Phys.J.C 3 (1998) 1-794
•
DOI:
- 10.1007/s10052-998-0104-x

The Construction of the L3 Experiment

L3

Collaboration

•

B. Adeva
(
- CERN
)

et al.

- Nucl.Instrum.Meth.A 289 (1990) 35-102
•
DOI:
- 10.1016/0168-9002(90)90250-A

The L3 silicon microvertex detector

L3 SMD

Collaboration

•

M. Acciarri
(
- Aachen, Tech. Hochsch.
)

et al.

- Nucl.Instrum.Meth.A 351 (1994) 300-312
•
DOI:
- 10.1016/0168-9002(94)91357-9

The L3 lead scintillating fiber calorimeter

G. Basti
(
- Rome U. and
- INFN, Rome
)
,
Mario Campanelli
(
- Rome U. and
- INFN, Rome
)
,
F. Cavallari
(
- Rome U. and
- INFN, Rome
)
,
F. de Notaristefani
(
- Rome U. and
- INFN, Rome
)
,
M. Diemoz
(
- Rome U. and
- INFN, Rome
)

et al.

- Nucl.Instrum.Meth.A 374 (1996) 293-298
•
DOI:
- 10.1016/0168-9002(96)00206-9

Luminosity Measurement in the L3 Detector at LEP

et al.

- Nucl.Instrum.Meth.A 381 (1996) 236-266
•
DOI:
- 10.1016/S0168-9002(96)00734-6

The Forward muon detector of L3

et al.

- Nucl.Instrum.Meth.A 383 (1996) 342-366
•
DOI:
- 10.1016/S0168-9002(96)00777-2

First level charged particle trigger for the L3 detector

et al.

- Nucl.Instrum.Meth.A 306 (1991) 150-158
•
DOI:
- 10.1016/0168-9002(91)90313-F

Charmonium Spectroscopy from Inclusive psi-prime and J/psi Radiative Decays

et al.

- Phys.Rev.D 34 (1986) 711
•
DOI:
- 10.1103/PhysRevD.34.711

Evidence for Exclusive $\eta_c$ Production in $\gamma \gamma$ Interactions

PLUTO

Collaboration

•

Christoph Berger
(
- Aachen, Tech. Hochsch.
)

et al.

- Phys.Lett.B 167 (1986) 120-126,
- Phys. Lett. B167 ( 1986) 120-126 and Hamburg Desy - DESY 85-130 (85,REC.NOV.) 13p
•
DOI:
- 10.1016/0370-2693(86)90558-7