Differential branching fraction and angular analysis of Λb0 → Λμ+μ− decays
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Author(s)
Aaij, R.
Adeva, B.
Adinolfi, M.
Affolder, A.
Ajaltouni, Z.
Akar, S.
Albrecht, J.
Alessio, F.
Alexander, M.
Ali, S.
Date Issued
June 2015
Journal
Journal of High Energy Physics
Publisher
Springer Berlin Heidelberg
Version
Final published version
Abstract
Abstract
The differential branching fraction of the rare decay Λ
b
0
→ Λμ+μ− is measured as a function of q2, the square of the dimuon invariant mass. The analysis is performed using proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb−1, collected by the LHCb experiment. Evidence of signal is observed in the q2 region below the square of the J/ψ mass. Integrating over 15 < q2 < 20 GeV2/c4 the differential branching fraction is measured as
d
ℬ
Λ
b
0
→
Λ
μ
+
μ
−
/
d
q
2
=
1.18
−
0.08
+
0.09
±
0.03
±
0.27
×
10
−
7
GeV
2
/
c
4
−
1
,
$$ \mathrm{d}\mathrm{\mathcal{B}}\left({\varLambda}_b^0\to \varLambda {\mu}^{+}{\mu}^{-}\right)/d{q}^2=\left({1.18}_{-0.08}^{+0.09}\pm 0.03\pm 0.27\right)\times {10}^{-7}{\left({\mathrm{GeV}}^2/{c}^4\right)}^{-1}, $$
where the uncertainties are statistical, systematic and due to the normalisation mode, Λ
b
0
→ J/ψΛ, respectively. In the q2 intervals where the signal is observed, angular distributions are studied and the forward-backward asymmetries in the dimuon (A
FB
ℓ
) and hadron (A
FB
h
) systems are measured for the first time. In the range 15 < q2 < 20 GeV2/c4 they are found to be
A
F
B
ℓ
=
−
0.05
±
0.09
stat
±
0.03
syst
and
A
F
B
h
=
−
0.29
±
0.07
stat
±
0.03
syst
.
$$ \begin{array}{l}{A}_{\mathrm{FB}}^{\ell }=-0.05\pm 0.09\left(\mathrm{stat}\right)\pm 0.03\left(\mathrm{syst}\right)\;\mathrm{and}\hfill \\ {}{A}_{\mathrm{FB}}^h=-0.29\pm 0.07\left(\mathrm{stat}\right)\pm 0.03\left(\mathrm{syst}\right).\hfill \end{array} $$
MIT Department
Massachusetts Institute of Technology. Department of Physics
Terms of Use
Creative Commons Attribution 4.0 International license
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1007/JHEP06(2015)115
