Measurement of branching fractions and search for CP violation in D0 → π+π−η, D0 → K+K−η, and D0 → ϕη at Belle
Authors:   The Belle collaboration, Li L. K. , Schwartz A. J. , Kinoshita K. , Adachi I. , Aihara H. , Al Said S. , Asner D. M. , Atmacan H. , Aulchenko V. , Aushev T. , Ayad R. , Babu V. , Bahinipati S. , Behera P. , Bennett J. , Bessner M. , Bilka T. , Biswal J. , Bobrov A. , Bonvicini G. , Bozek A. , Bračko M. , Branchini P. , Browder T. E. , Budano A. , Campajola M. , Červenkov D. , Chang M.-C. , Chang P. , Chekelian V. , Chen A. , Chen Y. Q. , Cheon B. G. , Chilikin K. , Cho H. E. , Cho K. , Cho S.-J. , Choi S.-K. , Choi Y. , Choudhury S. , Cinabro D. , Cunliffe S. , Das S. , Dash N. , De Nardo G. , De Pietro G. , Dhamija R. , Di Capua F. , Doležal Z. , Dong T. V. , Eidelman S. , Epifanov D. , Ferber T. , Fulsom B. G. , Garg R. , Gaur V. , Giri A. , Goldenzweig P. , Golob B. , Graziani E. , Gu T. , Guan Y. , Hadjivasiliou C. , Halder S. , Hayasaka K. , Hou W.-S. , Inami K. , Ishikawa A. , Iwasaki M. , Iwasaki Y. , Jacobs W. W. , Jang E.-J. , Jia S. , Jin Y. , Joo K. K. , Kang K. H. , Karyan G. , Kiesling C. , Kim C. H. , Kim D. Y. , Kim K.-H. , Kim S. H. , Kim Y.-K. , Kodyš P. , Konno T. , Korobov A. , Korpar S. , Kovalenko E. , Križan P. , Kroeger R. , Krokovny P. , Kuhr T. , Kumar M. , Kumara K. , Kuzmin A. , Kwon Y.-J. , Lalwani K. , Laurenza M. , Lee S. C. , Li C. H. , Gioi L. Li , Libby J. , Lieret K. , Liventsev D. , Masuda M. , Matvienko D. , Merola M. , Metzner F. , Miyabayashi K. , Mizuk R. , Mohanty G. B. , Mori T. , Nakao M. , Natkaniec Z. , Natochii A. , Nayak L. , Nayak M. , Niiyama M. , Nisar N. K. , Nishida S. , Nishimura K. , Ono H. , Oskin P. , Pakhlov P. , Pakhlova G. , Pardi S. , Park S.-H. , Passeri A. , Paul S. , Pedlar T. K. , Pestotnik R. , Piilonen L. E. , Podobnik T. , Popov V. , Prencipe E. , Prim M. T. , Rout N. , Russo G. , Sahoo D. , Sakai Y. , Sandilya S. , Sangal A. , Santelj L. , Sanuki T. , Savinov V. , Schnell G. , Schwanda C. , Seino Y. , Senyo K. , Shapkin M. , Sharma C. , Shen C. P. , Shiu J.-G. , Shwartz B. , Sokolov A. , Solovieva E. , Starič M. , Stottler Z. S. , Sumihama M. , Sumiyoshi T. , Takizawa M. , Tanida K. , Tenchini F. , Uchida M. , Uglov T. , Unno Y. , Uno K. , Uno S. , Vahsen S. E. , Van Tonder R. , Varner G. , Vinokurova A. , Waheed E. , Wang C. H. , Wang M.-Z. , Wang P. , Wang X. L. , Watanuki S. , Won E. , Yabsley B. D. , Yan W. B. , Yang S. B. , Ye H. , Yelton J. , Yin J. H. , Yusa Y. , Zhang Z. P. , Zhilich V. , Zhukova V. 
Published: September 2021

Abstract
We measure the branching fractions and CP asymmetries for the singly Cabibbo-suppressed decays D0 → π+π−η, D0 → K+K−η, and D0 → ϕη, using 980 fb−1 of data from the Belle experiment at the KEKB e+e− collider. We obtain$$ {\displaystyle \begin{array}{c}\mathcal{B}\left({D}^0\to {\pi}^{+}{\pi}^{-}\eta \right)=\left[1.22\pm 0.02\left(\mathrm{stat}\right)\pm 0.02\left(\mathrm{syst}\right)\pm 0.03\left({\mathcal{B}}_{\mathrm{ref}}\right)\right]\times {10}^{-3},\\ {}\mathcal{B}\left({D}^0\to {K}^{+}{K}^{-}\eta \right)=\left[{1.80}_{-0.06}^{+0.07}\left(\mathrm{stat}\right)\pm 0.04\left(\mathrm{syst}\right)\pm 0.05\left({\mathcal{B}}_{\mathrm{ref}}\right)\right]\times {10}^{-4},\\ {}\mathcal{B}\left({D}^0\to \phi \eta \right)=\left[1.84\pm 0.09\left(\mathrm{stat}\right)\pm 0.06\left(\mathrm{syst}\right)\pm 0.05\left({\mathcal{B}}_{\mathrm{ref}}\right)\right]\times {10}^{-4},\end{array}} $$

B

D
0

→

π
+

π
−

η

=

1.22
±
0.02

stat

±
0.02

syst

±
0.03

B
ref

×

10

−
3

,

B

D
0

→

K
+

K
−

η

=

1.80

−
0.06

+
0.07

stat

±
0.04

syst

±
0.05

B
ref

×

10

−
4

,

B

D
0

→
ϕη

=

1.84
±
0.09

stat

±
0.06

syst

±
0.05

B
ref

×

10

−
4

,

where the third uncertainty ($$ \mathcal{B} $$
B
ref) is from the uncertainty in the branching fraction of the reference mode D0 → K−π+η. The color-suppressed decay D0 → ϕη is observed for the first time, with very high significance. The results for the CP asymmetries are$$ {\displaystyle \begin{array}{c}{A}_{CP}\left({D}^0\ {\pi}^{+}{\pi}^{-}\eta \right)=\left[0.9\pm 1.2\left(\mathrm{stat}\right)\pm 0.5\left(\mathrm{syst}\right)\right]\%,\\ {}{A}_{CP}\left({D}^0\to {K}^{+}{K}^{-}\eta \right)=\left[-1.4\pm 3.3\left(\mathrm{stat}\right)\pm 1.1\left(\mathrm{syst}\right)\right]\%,\\ {} ACP\ \left({D}^0\to \phi \eta \right)=\left[-1.9\pm 4.4\left(\mathrm{stat}\right)\pm 0.6\left(\mathrm{syst}\right)\right]\%.\end{array}} $$

A
CP

D
0

π
+

π
−

η

=

0.9
±
1.2

stat

±
0.5

syst

%
,

A
CP

D
0

→

K
+

K
−

η

=

−
1.4
±
3.3

stat

±
1.1

syst

%
,

ACP

D
0

→
ϕη

=

−
1.9
±
4.4

stat

±
0.6

syst

%
.

The results for D0 → π+π−η are a significant improvement over previous results. The branching fraction and ACP results for D0 → K+K−η, and the ACP result for D0 → ϕη, are the first such measurements. No evidence for CP violation is found in any of these decays.