Direct observation of longitudinally polarized $W^\pm$ bosons

The three different helicity states of W ± bosons, produced in the reaction e + e − → W + W − → ℓνq q ̄ are studied using leptonic and hadronic W decays at s =183 GeV and 189 GeV. The W polarisation is also measured as a function of the scattering angle between the W − and the direction of the e − beam. The analysis demonstrates that W bosons are produced with all three helicities, the longitudinal and the two transverse states. Combining the results from the two center-of-mass energies and with leptonic and hadronic W decays, the fraction of longitudinally polarised W ± bosons is measured to be 0.261 ± 0.051(stat.) ± 0.016(syst.) in agreement with the expectation from the Standard Model.

electron positron: colliding beams
electron positron: annihilation
W: pair production
W: hadronic decay
W: leptonic decay
W: helicity
W: longitudinal
W: angular distribution
L3
experimental results

References(28)

Figures(5)

Measurement of mass and width of the $W$ boson at LEP

L3

Collaboration

•

M. Acciarri

et al.

- Phys.Lett.B 454 (1999) 386-398
•
e-Print:
- hep-ex/9909010
•
DOI:
- 10.1016/S0370-2693(99)00348-2

Measurement of $W$ pair cross-sections in $e^{+} e^{-}$ interactions at $S^{(1/2)}$ = 183-GeV and $W$ decay branching fractions

L3

Collaboration

•

M. Acciarri

et al.

- Phys.Lett.B 436 (1998) 437-452
•
DOI:
- 10.1016/S0370-2693(98)01036-3

Measurement of the $W$ mass in $e^{+} e^{-}$ collisions at 183-GeV

ALEPH

Collaboration

•

R. Barate
(
- Annecy, LAPP
)

et al.

- Phys.Lett.B 453 (1999) 121-137
•
DOI:
- 10.1016/S0370-2693(99)00305-6

Measurement of W pair production in e+ e- collisions at 183-GeV

ALEPH

Collaboration

•

R. Barate
(
- Annecy, LAPP
)

et al.

- Phys.Lett.B 453 (1999) 107-120
•
e-Print:
- hep-ex/9903053
•
DOI:
- 10.1016/S0370-2693(99)00304-4

Measurements of the trilinear gauge boson couplings W W V (V = gamma,Z) in e+ e- collisions at 183-GeV

DELPHI

Collaboration

•

P. Abreu

et al.

- Phys.Lett.B 459 (1999) 382-396
•
DOI:
- 10.1016/S0370-2693(99)00671-1

W pair production cross-section and W branching fractions in e+ e- interactions at 183-GeV

DELPHI

Collaboration

•

P. Abreu

et al.

- Phys.Lett.B 456 (1999) 310-321
•
DOI:
- 10.1016/S0370-2693(99)00488-8

Measurement of the $W$ mass and width in $e^{+} e^{-}$ collisions at 183-GeV

OPAL

Collaboration

•

G. Abbiendi

et al.

- Phys.Lett.B 453 (1999) 138-152
•
e-Print:
- hep-ex/9901025
•
DOI:
- 10.1016/S0370-2693(99)00308-1

Measurement of triple gauge boson couplings from $W^{+} W^{-}$ production at $S^{(1/2)}$ = 172-GeV

OPAL

Collaboration

•

K. Ackerstaff

et al.

- Eur.Phys.J.C 2 (1998) 597-606
•
e-Print:
- hep-ex/9709023
•
DOI:
- 10.1007/s100520050164

$W^{+} W^{-}$ production and triple gauge boson couplings at LEP energies up to 183-GeV

OPAL

Collaboration

•

G. Abbiendi

et al.

- Eur.Phys.J.C 8 (1999) 191-215
•
e-Print:
- hep-ex/9811028
•
DOI:
- 10.1007/s100529901106

Partial Symmetries of Weak Interactions

S.L. Glashow
(
- Copenhagen U.
)

- Nucl.Phys. 22 (1961) 579-588,
- Also in *Lai, C. H. (Ed.): Gauge Theory Of Weak and Electromagnetic Interactions*, 171-180
•
DOI:
- 10.1016/0029-5582(61)90469-2

A Model of Leptons

Steven Weinberg
(
- MIT, LNS
)

- Phys.Rev.Lett. 19 (1967) 1264-1266,
- Also in *Lichtenberg, D. B. (ed.), Rosen, S. P. (ed.): Developments In The Quark Theory Of Hadrons, Vol. 1*, 157-159,
- In *Lai, C. H. (ed.): Gauge Theory Of Weak and Electromagnetic Interactions*, 185-187,
- In *Rosner, J. L. (ed.): New Particles*, 26-28
•
DOI:
- 10.1103/PhysRevLett.19.1264

Weak and Electromagnetic Interactions

Abdus Salam
(
- Imperial Coll., London and
- ICTP, Trieste
)

- Conf.Proc.C 680519 (1968) 367-377,
- Reprinted in *Lichtenberg, D. B. (ed.), Rosen, S. P. (ed.): Developments In The Quark Theory Of Hadrons, Vol. 1*, 160-170, and in *Lai, C. H. (ed.): Gauge Theory Of Weak and Electromagnetic Interactions*, 188-198,
- Also in *Rosner, J.L. (ed.): New particles* 29-39,
- Also in *Ali, A. (ed.) et al.: Selected papers of Abdus Salam* 244-254
•
DOI:
- 10.1142/9789812795915_0034

Perturbation theory of massive Yang-Mills fields

M.J.G. Veltman
(
- Utrecht U. and
- Orsay, LPT
)

- Nucl.Phys.B 7 (1968) 637-650
•
DOI:
- 10.1016/0550-3213(68)90197-1

Renormalizable Lagrangians for Massive Yang-Mills Fields

Gerard 't Hooft
(
- Utrecht U.
)

- Nucl.Phys.B 35 (1971) 167-188,
- Also in *Lichtenberg, D. B. ( Ed.), Rosen, S. P. ( Ed.): Developments In The Quark Theory Of Hadrons, Vol. 1*, 171-192, and in *Lai, C.H. (ed.) Gauge Theory of Weak and Electromagnetic Interactions*, 300-321,
•
DOI:
- 10.1016/0550-3213(71)90139-8

Regularization and Renormalization of Gauge Fields

Gerard 't Hooft
(
- Utrecht U.
)
,
M.J.G. Veltman
(
- Utrecht U.
)

- Nucl.Phys.B 44 (1972) 189-213,
- Also in *Lai, C. H. ( Ed.): Gauge Theory Of Weak and Electromagnetic Interactions*, 322-346
•
DOI:
- 10.1016/0550-3213(72)90279-9