${{\mathit D}_{{{1}}}{(2420)}}$ POLARIZATION AMPLITUDE A$_{{{\mathit D}_{{{1}}}}}$

INSPIRE   PDGID:
M253PAH
A polarization amplitude A$_{{{\mathit D}_{{{1}}}}}$ is a parameter that depends on the initial polarization of the ${{\mathit D}_{{{1}}}}$ and is sensitive to a possible ${\mathit S}{\mathrm -wave}$ contribution to its decay. For ${{\mathit D}_{{{1}}}}$ decays the helicity angle, $\theta _{h}$, distribution varies like 1 + A$_{{{\mathit D}_{{{1}}}}}$cos $^2\theta _{h}$, where $\theta _{h}$ is the angle in the ${{\mathit D}^{*}}$ rest frame between the two pions emitted by the ${{\mathit D}_{{{1}}}}$ $\rightarrow$ ${{\mathit D}^{*}}{{\mathit \pi}}$ and the ${{\mathit D}^{*}}$ $\rightarrow$ ${{\mathit D}}{{\mathit \pi}}$.

Unpolarized ${{\mathit D}_{{{1}}}}$ decaying purely via ${\mathit D}{\mathrm -wave}$ is predicted to give A$_{{{\mathit D}_{{{1}}}}}$ = 3.
VALUE EVTS DOCUMENT ID TECN CHG  COMMENT
$\bf{ 5.73 \pm0.25}$ OUR AVERAGE
$7.8$ ${}^{+6.7}_{-2.7}$ ${}^{+4.6}_{-1.8}$ 2.7k 1
ABRAMOWICZ
2013
ZEUS 0 ${{\mathit e}^{\pm}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit D}^{(*)+}}{{\mathit \pi}^{-}}{{\mathit X}}$
$5.72$ $\pm0.25$ 103k
DEL-AMO-SANCH..
2010P
BABR 0 ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit D}^{*+}}{{\mathit \pi}^{-}}{{\mathit X}}$
$5.9$ ${}^{+3.0}_{-1.7}$ ${}^{+2.4}_{-1.0}$
CHEKANOV
2009
ZEUS 0 ${{\mathit e}^{\pm}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit D}^{*+}}{{\mathit \pi}^{-}}{{\mathit X}}$
• • We do not use the following data for averages, fits, limits, etc. • •
$3.30$ $\pm0.48$ 210k 2
AAIJ
2013CC
LHCB 0 ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit D}^{*+}}{{\mathit \pi}^{-}}{{\mathit X}}$
$3.8$ $\pm0.6$ $\pm0.8$ 3
AUBERT
2009Y
BABR 0 ${{\mathit B}^{+}}$ $\rightarrow$ ${{\mathit D}_{{{1}}}^{0}}{{\mathit \ell}^{+}}{{\mathit \nu}_{{{{{\mathit \ell}}}}}}$
$3.8$ $\pm0.6$ $\pm0.8$ 3
AUBERT
2009Y
BABR + ${{\mathit B}^{0}}$ $\rightarrow$ ${{\mathit D}_{{{1}}}^{-}}{{\mathit \ell}^{+}}{{\mathit \nu}_{{{{{\mathit \ell}}}}}}$
$2.74$ ${}^{+1.40}_{-0.93}$ 4
AVERY
1994C
CLE2 0 ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit D}^{*+}}{{\mathit \pi}^{-}}{{\mathit X}}$
1  From the combined fit of the ${{\mathit M}}({{\mathit D}^{+}}{{\mathit \pi}^{-}}$) and ${{\mathit M}}({{\mathit D}^{*+}}{{\mathit \pi}^{-}}$) distributions. and A$_{{{\mathit D}_{{{2}}}}}$ fixed to the theoretical prediction of $-1$. A pure ${\mathit D}{\mathrm -wave}$ not excluded although some ${\mathit S}{\mathrm -wave}$ mixing possible.
2  Systematic uncertainty not estimated. Resonance parameters fixed.
3  Assuming $\Gamma $( ${{\mathit \Upsilon}{(4S)}}$ $\rightarrow$ ${{\mathit B}^{+}}{{\mathit B}^{-}}$) $/$ $\Gamma $( ${{\mathit \Upsilon}{(4S)}}$ $\rightarrow$ ${{\mathit B}^{0}}{{\overline{\mathit B}}^{0}}$) = $1.065$ $\pm0.026$ and equal partial widths and helicity angle distributions for charged and neutral ${{\mathit D}_{{{1}}}}$ mesons.
4  Systematic uncertainties not estimated.
References