Search for anomalous production of high mass photon pairs in e+ e- collisions at LEP

A search for events with photon pairs of large invariant mass is described based on a data sample of 43 pb −1 collected with the OPAL detector. This search is motivated by the L3 observation of four events of the type e + e − → l + l − γγ with an invariant mass of the two photons, m γγ , clustering around 60 GeV. In the OPAL data, four ℓ + ℓ − γγ events are found with m γγ above 40 GeV. The number of observed events is consistent with the QED expectation and no obvious resonance structure is seen. Three candidate qq̄γγ events with m γγ above 40 GeV are found and no νν̄nγγ candidate with m γγ > 5 GeV is found. From these searches an upper limit is set on any anomalous production of ℓ + ℓ − γγ (ℓ = e, μ , τ ) events, where the ℓ + ℓ − pair comes from a virtual Z 0 and m γγ is near 60 GeV , of B( Z 0 → Z ∗0 γγ → ℓ + ℓ − γγ) < 6.0 × 10 −7 at the 95% CL. In a similar search in the reaction e + e − → γγγ , seven events are observed with a photon pairing of mass near 60 GeV compared to an expected background of 2.7 ± 0.4 from QED. In a search for the production of a 60 GeV resonance X in two-photon collisions, an upper limit is set on Γ X B 2 (X → γγ ) of 2.6 MeV at the 95% CL. A search is also performed for ℓ + ℓ − X (ℓ = e, μ ) events in non-γγ decay modes of X. No indication of a 60 GeV resonance is seen. Combining these two searches, Γ X values greater than 110 MeV are excluded at the 95% CL for ℓ + ℓ − γγ (ℓ = e, μ ) cross-sections greater than 0.05 pb.

electron positron: colliding beams
colliding beams: electron positron
electron positron: annihilation
annihilation: electron positron
electron positron: inelastic scattering
inelastic scattering: electron positron
photon: pair production
pair production: photon
lepton: pair production
pair production: lepton

References(27)

Figures(0)

High mass photon pairs in lepton+ lepton- gamma gamma events at LEP

L3

Collaboration

•

O. Adriani
(
- Florence U. and
- INFN, Florence
)

et al.

- Phys.Lett.B 295 (1992) 337-346
•
DOI:
- 10.1016/0370-2693(92)91576-U

Final state multiple photon effects in fermion pair production at SLC / LEP

S. Jadach
(
- CERN and
- Jagiellonian U.
)
,
B.F.L. Ward
(
- Tennessee U. and
- SLAC
)

- Phys.Lett.B 274 (1992) 470-472,
- Krakow Univ. - TPJU-91-18 (91/09,rec.Dec.) 4 p. Tennessee Univ. Knoxville - UTHEP-91-0903 (91/09,rec.Dec.) 4 p. (submitted to Phys. Lett. B),
- Phys. Lett. B274 (1992) 470-472 and Krakow Univ. - TPJU-91-18 (91/09,rec.Dec.) 4 p
•
DOI:
- 10.1016/0370-2693(92)92017-B

Search for heavy neutral spinless particles using e+ e- ---> e+ e- and e+ e- ---> gamma gamma reactions in the center-of-mass energy range between 54-GeV and 64-GeV

VENUS

Collaboration

•

K. Abe
(
- Tohoku U.
)

et al.

- Phys.Lett.B 302 (1993) 119-124
•
DOI:
- 10.1016/0370-2693(93)90645-X

Evidence for Final State Photons in Multi - Hadronic Decays of the $\Z^0$

OPAL

Collaboration

•

M.Z. Akrawy
(
- Queen Mary, U. of London
)

et al.

- Phys.Lett.B 246 (1990) 285-296
•
DOI:
- 10.1016/0370-2693(90)91347-E

A Measurement of photon radiation in lepton pair events from Z0 decays

OPAL

Collaboration

•

P.D. Acton
(
- Brunel U.
)

et al.

- Phys.Lett.B 273 (1991) 338-354
•
DOI:
- 10.1016/0370-2693(91)91694-Q

A Direct measurement of the Z0 invisible width by single photon counting

OPAL

Collaboration

•

M.Z. Akrawy

et al.

- Z.Phys.C 50 (1991) 373-384
•
DOI:
- 10.1007/BF01551449

The OPAL detector at LEP

OPAL

Collaboration

•

K. Ahmet

et al.

- Nucl.Instrum.Meth.A 305 (1991) 275-319
•
DOI:
- 10.1016/0168-9002(91)90547-4

The Trigger system of the OPAL experiment at LEP

OPAL

Collaboration

•

M. Arignon
(
- Saclay
)

et al.

- Nucl.Instrum.Meth.A 313 (1992) 103-125
•
DOI:
- 10.1016/0168-9002(92)90087-K

A Search for Acoplanar Pairs of Leptons or Jets in $\Z^0$ Decays: Mass Limits on Supersymmetric Particles

OPAL

Collaboration

•

M.Z. Akrawy
(
- Queen Mary, U. of London
)

et al.

- Phys.Lett.B 240 (1990) 261-270
•
DOI:
- 10.1016/0370-2693(90)90444-B

Measurement of the $Z^0$ line shape parameters and the electroweak couplings of charged leptons

OPAL

Collaboration

•

G. Alexander

et al.

- Z.Phys.C 52 (1991) 175-208

The Detector simulation program for the OPAL experiment at LEP

OPAL

Collaboration

•

J. Allison
(
- Manchester U.
)

et al.

- Nucl.Instrum.Meth.A 317 (1992) 47-74
•
DOI:
- 10.1016/0168-9002(92)90593-S

Initial State Radiation at LEP Energies and the Corrections to Higgs Boson Production

Frits A. Berends
(
- Leiden U.
)
,
R. Kleiss
(
- Leiden U.
)

- Nucl.Phys.B 260 (1985) 32-60
•
DOI:
- 10.1016/0550-3213(85)90309-8

The Lund Monte Carlo for Jet Fragmentation and e+ e- Physics: Jetset Version 6.2

Torbjorn Sjostrand
(
- Lund U., Dept. Theor. Phys.
)

- Comput.Phys.Commun. 39 (1986) 347-407
•
DOI:
- 10.1016/0010-4655(86)90096-2

Radiative Corrections to the Process $e^+ e^- \to$ Neutrino Anti-neutrino $\gamma$

Frits A. Berends
(
- Leiden U.
)
,
G.J.H. Burgers
(
- CERN
)
,
C. Mana
(
- CERN
)
,
M. Martinez
(
- Barcelona, Autonoma U.
)
,
W.L. van Neerven
(
- Leiden U.
)

- Nucl.Phys.B 301 (1988) 583-600
•
DOI:
- 10.1016/0550-3213(88)90278-7

- Z.Phys.C 47 309

Electroweak parameters of the $Z^0$ resonance and the Standard Model: the LEP Collaborations

LEP and
ALEPH and
DELPHI and
L3 and
OPAL

Collaborations

•

G. Alexander

et al.

- Phys.Lett.B 276 (1992) 247-253
•
DOI:
- 10.1016/0370-2693(92)90572-L

Isolated hard photon emission in hadronic Z0 decays

L3

Collaboration

•

O. Adriani
(
- Florence U. and
- INFN, Florence
)

et al.

- Phys.Lett.B 292 (1992) 472-484
•
DOI:
- 10.1016/0370-2693(92)91205-N

Measurement of the cross-sections of the reactions e+ e- ---> gamma gamma and e+ e- ---> gamma gamma gamma at LEP

OPAL

Collaboration

•

M.Z. Akwawy
(
- Queen Mary, U. of London
)

et al.

- Phys.Lett.B 257 (1991) 531-540,
- Phys. Lett. B257 (1991) 531-540 and CERN Geneva - CERN-PPE-90-189 (90/12,rec.Jan.91) 21 p
•
DOI:
- 10.1016/0370-2693(91)91932-L

The reaction e+ e- ---> gamma gamma (gamma) at Z0 energies

DELPHI

Collaboration

•

P. Abreu
(
- LIP, Lisbon
)

et al.

- Phys.Lett.B 268 (1991) 296-304,
- Phys. Lett. B268 (1991) 296-304 and CERN Geneva - CERN-PPE-91-109 (91/07,rec.Sep.) 13 p
•
DOI:
- 10.1016/0370-2693(91)90819-C

A Test of quantum electrodynamics in the reaction e+ e- ---> gamma gamma (gamma)

L3

Collaboration

•

O. Adriani
(
- Florence U. and
- INFN, Florence
)

et al.

- Phys.Lett.B 288 (1992) 404-411
•
DOI:
- 10.1016/0370-2693(92)91120-X

Distributions for electron-Positron Annihilation Into Two and Three Photons

Frits A. Berends
(
- Leiden U. and
- DESY
)
,
R. Kleiss
(
- Leiden U. and
- DESY
)

- Nucl.Phys.B 186 (1981) 22-34
•
DOI:
- 10.1016/0550-3213(81)90090-0

Review of particle properties. Particle Data Group

et al.

- Phys.Rev.D 45 (1992) S1,
- Phys.Rev.D 46 (1992) 5210 (erratum)
•
DOI:
- 10.1103/PhysRevD.45.S1

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

Search for the minimal standard model Higgs boson in e+ e- collisions at LEP

OPAL

Collaboration

•

M.Z. Akrawy
(
- Queen Mary, U. of London
)

et al.

- Phys.Lett.B 253 (1991) 511-523
•
DOI:
- 10.1016/0370-2693(91)91761-J

Radiative Corrections to the Process $e^+ e^- \to e^+ e^- \mu^+ \mu^-$

- Nucl.Phys.B 253 (1985) 421,
- Preprint - BERENDS, F.A. (REC.JUL.84) 43p,
- Abstract Only In *Granlibakken 1984, Proceedings, Photon-photon Collisions*, 430
•
DOI:
- 10.1016/0550-3213(85)90540-1

1-25 of 27
1
2
25 / page