pdgLive

MRKJ

$\Gamma\mathrm {( {{\mathit X}^{0}} \rightarrow {{\mathit e}^{+}} {{\mathit e}^{-}} )}$=10 keV

$>48$

MRKJ

$\Gamma\mathrm {( {{\mathit X}^{0}} \rightarrow {{\mathit e}^{+}} {{\mathit e}^{-}} )}$=4 MeV

⁴

BERGER

PLUT

$\text{none 39.8 - 45.5}$

MRKJ

$\Gamma\mathrm {( {{\mathit X}^{0}} \rightarrow {{\mathit e}^{+}} {{\mathit e}^{-}} )}$=10 keV

$>47.8$

MRKJ

$\Gamma\mathrm {( {{\mathit X}^{0}} \rightarrow {{\mathit e}^{+}} {{\mathit e}^{-}} )}$=4 MeV

$\text{none 39.8 - 45.2}$

BEHREND

CELL

$>47$

BEHREND

CELL

$\Gamma\mathrm {( {{\mathit X}^{0}} \rightarrow {{\mathit e}^{+}} {{\mathit e}^{-}} )}$=4 MeV

¹	ODAKA 1989 looked for a narrow or wide scalar resonance in ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ hadrons at $\mathit E_{{\mathrm {cm}}}$ = $55.0-60.8$ GeV.

DERRICK 1986 found no deviation from the Standard Model Bhabha scattering at $\mathit E_{{\mathrm {cm}}}$= 29 GeV and set limits on the possible scalar boson ${{\mathit e}^{+}}{{\mathit e}^{-}}$ coupling. See their figure 4 for excluded region in the $\Gamma\mathrm {( {{\mathit X}^{0}} \rightarrow {{\mathit e}^{+}} {{\mathit e}^{-}} )}-{\mathit m}_{{{\mathit X}^{0}}}$ plane. Electronic chiral invariance requires a parity doublet of ${{\mathit X}^{0}}$, in which case the limit applies for $\Gamma\mathrm {( {{\mathit X}^{0}} \rightarrow {{\mathit e}^{+}} {{\mathit e}^{-}} )}$ = 3 MeV.

³	ADEVA 1985 first limit is from 2${{\mathit \gamma}}$, ${{\mathit \mu}^{+}}{{\mathit \mu}^{-}}$ , hadrons assuming ${{\mathit X}^{0}}$ is a scalar. Second limit is from ${{\mathit e}^{+}}{{\mathit e}^{-}}$ channel. $\mathit E_{{\mathrm {cm}}}$ = 40$-$47 GeV. Supersedes ADEVA 1984 .

⁴

BERGER 1985B looked for effect of spin-0 boson exchange in ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit e}^{-}}$ and ${{\mathit \mu}^{+}}{{\mathit \mu}^{-}}$ at $\mathit E_{{\mathrm {cm}}}$ = $34.7$ GeV. See Fig.$~$5 for excluded region in the ${\mathit m}_{{{\mathit X}^{0}}}−\Gamma\mathrm {({{\mathit X}^{0}})}$ plane.

⁵

ADEVA 1984 and BEHREND 1984C have $\mathit E_{{\mathrm {cm}}}$ = 39.8$-$45.5 GeV. MARK-J searched ${{\mathit X}^{0}}$ in ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ hadrons, 2${{\mathit \gamma}}$, ${{\mathit \mu}^{+}}{{\mathit \mu}^{-}}$ , ${{\mathit e}^{+}}{{\mathit e}^{-}}$ and CELLO in the same channels plus ${{\mathit \tau}}$ pair. No narrow or broad ${{\mathit X}^{0}}$ is found in the energy range. They also searched for the effect of ${{\mathit X}^{0}}$ with ${\mathit m}_{{{\mathit X}}}$ $>\mathit E_{{\mathrm {cm}}}$. The second limits are from Bhabha data and for spin-0 singlet. The same limits apply for $\Gamma\mathrm {( {{\mathit X}^{0}} \rightarrow {{\mathit e}^{+}} {{\mathit e}^{-}} )}$ = 2 MeV if ${{\mathit X}^{0}}$ is a spin-0 doublet. The second limit of BEHREND 1984C was read off from their figure 2. The original papers also list limits in other channels.

References:

ODAKA

1989

JPSJ 58 3037

New Limits on Neutral Scalar Bosons

DERRICK

1986

PL 166B 463

New Results from Bhabha Scattering at 29 GeV

Also

PR D34 3286

Experimental Study of the Reactions ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit e}^{-}}$ and ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}$ at 29 GeV

PL 152B 439

New Particles Searches

Also

PRPL 109 131

A Summary of Experimental Results from MARK-J: High Energy ${{\mathit e}^{+}}{{\mathit e}^{-}}$ Collisions at PETRA

BERGER

1985B

ZPHY C27 341

Tests of the Standard Model with Lepton Pair Production in ${{\mathit e}^{+}}{{\mathit e}^{-}}$ Reactions