Using data samples of 983.0 fb−1 and 427.9 fb−1 accumulated with the Belle and Belle II detectors operating at the KEKB and SuperKEKB asymmetric-energy e+e− colliders, singly Cabibbo-suppressed decays <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_25717_Article_IEq4.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="81" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <msubsup> <mi mathvariant="normal">Ξ</mi> <mi>c</mi> <mo>+</mo> </msubsup> <mo>→</mo> <mi>p</mi> <msubsup> <mi>K</mi> <mi>S</mi> <mn>0</mn> </msubsup> </math></EquationSource> <EquationSource Format="TEX">$ {\Xi}_c^{+}\to p{K}_S^0 $</EquationSource> </InlineEquation>, <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_25717_Article_IEq5.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="79" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <msubsup> <mi mathvariant="normal">Ξ</mi> <mi>c</mi> <mo>+</mo> </msubsup> <mo>→</mo> <mi mathvariant="normal">Λ</mi> <msup> <mi>π</mi> <mo>+</mo> </msup> </math></EquationSource> <EquationSource Format="TEX">$ {\Xi}_c^{+}\to \Lambda {\pi}^{+} $</EquationSource> </InlineEquation>, and <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_25717_Article_IEq6.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="86" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <msubsup> <mi mathvariant="normal">Ξ</mi> <mi>c</mi> <mo>+</mo> </msubsup> <mo>→</mo> <msup> <mi mathvariant="normal">Σ</mi> <mn>0</mn> </msup> <msup> <mi>π</mi> <mo>+</mo> </msup> </math></EquationSource> <EquationSource Format="TEX">$ {\Xi}_c^{+}\to {\Sigma}^0{\pi}^{+} $</EquationSource> </InlineEquation> are observed for the first time. The ratios of branching fractions of <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_25717_Article_IEq7.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="81" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <msubsup> <mi mathvariant="normal">Ξ</mi> <mi>c</mi> <mo>+</mo> </msubsup> <mo>→</mo> <mi>p</mi> <msubsup> <mi>K</mi> <mi>S</mi> <mn>0</mn> </msubsup> </math></EquationSource> <EquationSource Format="TEX">$ {\Xi}_c^{+}\to p{K}_S^0 $</EquationSource> </InlineEquation>, <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_25717_Article_IEq8.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="79" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <msubsup> <mi mathvariant="normal">Ξ</mi> <mi>c</mi> <mo>+</mo> </msubsup> <mo>→</mo> <mi mathvariant="normal">Λ</mi> <msup> <mi>π</mi> <mo>+</mo> </msup> </math></EquationSource> <EquationSource Format="TEX">$ {\Xi}_c^{+}\to \Lambda {\pi}^{+} $</EquationSource> </InlineEquation>, and <InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_25717_Article_IEq9.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="86" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <msubsup> <mi mathvariant="normal">Ξ</mi> <mi>c</mi> <mo>+</mo> </msubsup> <mo>→</mo> <msup> <mi mathvariant="normal">Σ</mi> <mn>0</mn> </msup> <msup> <mi>π</mi> <mo>+</mo> </msup> </math></EquationSource> <EquationSource Format="TEX">$ {\Xi}_c^{+}\to {\Sigma}^0{\pi}^{+} $</EquationSource> </InlineEquation> relative to that of <InlineEquation ID="IEq10"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_25717_Article_IEq10.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="108" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <msubsup> <mi mathvariant="normal">Ξ</mi> <mi>c</mi> <mo>+</mo> </msubsup> <mo>→</mo> <msup> <mi mathvariant="normal">Ξ</mi> <mo>−</mo> </msup> <msup> <mi>π</mi> <mo>+</mo> </msup> <msup> <mi>π</mi> <mo>+</mo> </msup> </math></EquationSource> <EquationSource Format="TEX">$ {\Xi}_c^{+}\to {\Xi}^{-}{\pi}^{+}{\pi}^{+} $</EquationSource> </InlineEquation> are measured to be<Equation ID="Equa"> <MediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_25717_Article_Equa.gif" Format="GIF" Height="111" Rendition="HTML" Resolution="72" Type="Linedraw" Width="281" /> </MediaObject> <EquationSource Format="MATHML"><math display="block"> <mtable displaystyle="true"> <mtr> <mtd> <mfrac> <mrow> <mi mathvariant="script">B</mi> <mfenced close=")" open="("> <mrow> <msubsup> <mi mathvariant="normal">Ξ</mi> <mi>c</mi> <mo>+</mo> </msubsup> <mo>→</mo> <mi>p</mi> <msubsup> <mi>K</mi> <mi>S</mi> <mn>0</mn> </msubsup> </mrow> </mfenced> </mrow> <mrow> <mi mathvariant="script">B</mi> <mfenced close=")" open="("> <mrow> <msubsup> <mi mathvariant="normal">Ξ</mi> <mi>c</mi> <mo>+</mo> </msubsup> <mo>→</mo> <msup> <mi mathvariant="normal">Ξ</mi> <mo>−</mo> </msup> <msup> <mi>π</mi> <mo>+</mo> </msup> <msup> <mi>π</mi> <mo>+</mo> </msup> </mrow> </mfenced> </mrow> </mfrac> <mo>=</mo> <mfenced close=")" open="("> <mrow> <mn>2.47</mn> <mo>±</mo> <mn>0.16</mn> <mo>±</mo> <mn>0.07</mn> </mrow> </mfenced> <mo>%</mo> <mo>,</mo> </mtd> </mtr> <mtr> <mtd> <mfrac> <mrow> <mi mathvariant="script">B</mi> <mfenced close=")" open="("> <mrow> <msubsup> <mi mathvariant="normal">Ξ</mi> <mi>c</mi> <mo>+</mo> </msubsup> <mo>→</mo> <mi mathvariant="normal">Λ</mi> <msup> <mi>π</mi> <mo>+</mo> </msup> </mrow> </mfenced> </mrow> <mrow> <mi mathvariant="script">B</mi> <mfenced close=")" open="("> <mrow> <msubsup> <mi mathvariant="normal">Ξ</mi> <mi>c</mi> <mo>+</mo> </msubsup> <mo>→</mo> <msup> <mi mathvariant="normal">Ξ</mi> <mo>−</mo> </msup> <msup> <mi>π</mi> <mo>+</mo> </msup> <msup> <mi>π</mi> <mo>+</mo> </msup> </mrow> </mfenced> </mrow> </mfrac> <mo>=</mo> <mfenced close=")" open="("> <mrow> <mn>1.56</mn> <mo>±</mo> <mn>0.14</mn> <mo>±</mo> <mn>0.09</mn> </mrow> </mfenced> <mo>%</mo> <mo>,</mo> </mtd> </mtr> <mtr> <mtd> <mfrac> <mrow> <mi mathvariant="script">B</mi> <mfenced close=")" open="("> <mrow> <msubsup> <mi mathvariant="normal">Ξ</mi> <mi>c</mi> <mo>+</mo> </msubsup> <mo>→</mo> <msup> <mi mathvariant="normal">Σ</mi> <mn>0</mn> </msup> <msup> <mi>π</mi> <mo>+</mo> </msup> </mrow> </mfenced> </mrow> <mrow> <mi mathvariant="script">B</mi> <mfenced close=")" open="("> <mrow> <msubsup> <mi mathvariant="normal">Ξ</mi> <mi>c</mi> <mo>+</mo> </msubsup> <mo>→</mo> <msup> <mi mathvariant="normal">Ξ</mi> <mo>−</mo> </msup> <msup> <mi>π</mi> <mo>+</mo> </msup> <msup> <mi>π</mi> <mo>+</mo> </msup> </mrow> </mfenced> </mrow> </mfrac> <mo>=</mo> <mfenced close=")" open="("> <mrow> <mn>4.13</mn> <mo>±</mo> <mn>0.26</mn> <mo>±</mo> <mn>0.22</mn> </mrow> </mfenced> <mo>%</mo> <mo>.</mo> </mtd> </mtr> </mtable> </math></EquationSource> <EquationSource Format="TEX">$ {\displaystyle \begin{array}{c}\frac{\mathcal{B}\left({\Xi}_c^{+}\to p{K}_S^0\right)}{\mathcal{B}\left({\Xi}_c^{+}\to {\Xi}^{-}{\pi}^{+}{\pi}^{+}\right)}=\left(2.47\pm 0.16\pm 0.07\right)\%,\\ {}\frac{\mathcal{B}\left({\Xi}_c^{+}\to \Lambda {\pi}^{+}\right)}{\mathcal{B}\left({\Xi}_c^{+}\to {\Xi}^{-}{\pi}^{+}{\pi}^{+}\right)}=\left(1.56\pm 0.14\pm 0.09\right)\%,\\ {}\frac{\mathcal{B}\left({\Xi}_c^{+}\to {\Sigma}^0{\pi}^{+}\right)}{\mathcal{B}\left({\Xi}_c^{+}\to {\Xi}^{-}{\pi}^{+}{\pi}^{+}\right)}=\left(4.13\pm 0.26\pm 0.22\right)\%.\end{array}} $</EquationSource> </Equation>Multiplying these values by the branching fraction of the normalization channel, <InlineEquation ID="IEq11"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_25717_Article_IEq11.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="248" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <mi mathvariant="script">B</mi> <mfenced close=")" open="("> <mrow> <msubsup> <mi mathvariant="normal">Ξ</mi> <mi>c</mi> <mo>+</mo> </msubsup> <mo>→</mo> <msup> <mi mathvariant="normal">Ξ</mi> <mo>−</mo> </msup> <msup> <mi>π</mi> <mo>+</mo> </msup> <msup> <mi>π</mi> <mo>+</mo> </msup> </mrow> </mfenced> <mo>=</mo> <mfenced close=")" open="("> <mrow> <mn>2.9</mn> <mo>±</mo> <mn>1.3</mn> </mrow> </mfenced> <mo>%</mo> </math></EquationSource> <EquationSource Format="TEX">$ \mathcal{B}\left({\Xi}_c^{+}\to {\Xi}^{-}{\pi}^{+}{\pi}^{+}\right)=\left(2.9\pm 1.3\right)\% $</EquationSource> </InlineEquation>, the absolute branching fractions are determined to be<Equation ID="Equb"> <MediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_25717_Article_Equb.gif" Format="GIF" Height="66" Rendition="HTML" Resolution="72" Type="Linedraw" Width="385" /> </MediaObject> <EquationSource Format="MATHML"><math display="block"> <mtable displaystyle="true"> <mtr> <mtd> <mi mathvariant="script">B</mi> <mfenced close=")" open="("> <mrow> <msubsup> <mi mathvariant="normal">Ξ</mi> <mi>c</mi> <mo>+</mo> </msubsup> <mo>→</mo> <mi>p</mi> <msubsup> <mi>K</mi> <mi>S</mi> <mn>0</mn> </msubsup> </mrow> </mfenced> <mo>=</mo> <mfenced close=")" open="("> <mrow> <mn>7.16</mn> <mo>±</mo> <mn>0.46</mn> <mo>±</mo> <mn>0.20</mn> <mo>±</mo> <mn>3.21</mn> </mrow> </mfenced> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>4</mn> </mrow> </msup> <mo>,</mo> </mtd> </mtr> <mtr> <mtd> <mi mathvariant="script">B</mi> <mfenced close=")" open="("> <mrow> <msubsup> <mi mathvariant="normal">Ξ</mi> <mi>c</mi> <mo>+</mo> </msubsup> <mo>→</mo> <mi mathvariant="normal">Λ</mi> <msup> <mi>π</mi> <mo>+</mo> </msup> </mrow> </mfenced> <mo>=</mo> <mfenced close=")" open="("> <mrow> <mn>4.52</mn> <mo>±</mo> <mn>0.41</mn> <mo>±</mo> <mn>0.26</mn> <mo>±</mo> <mn>2.03</mn> </mrow> </mfenced> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>4</mn> </mrow> </msup> <mo>,</mo> </mtd> </mtr> <mtr> <mtd> <mi mathvariant="script">B</mi> <mfenced close=")" open="("> <mrow> <msubsup> <mi mathvariant="normal">Ξ</mi> <mi>c</mi> <mo>+</mo> </msubsup> <mo>→</mo> <msup> <mi mathvariant="normal">Σ</mi> <mn>0</mn> </msup> <msup> <mi>π</mi> <mo>+</mo> </msup> </mrow> </mfenced> <mo>=</mo> <mfenced close=")" open="("> <mrow> <mn>1.20</mn> <mo>±</mo> <mn>0.08</mn> <mo>±</mo> <mn>0.07</mn> <mo>±</mo> <mn>0.54</mn> </mrow> </mfenced> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>3</mn> </mrow> </msup> <mo>.</mo> </mtd> </mtr> </mtable> </math></EquationSource> <EquationSource Format="TEX">$ {\displaystyle \begin{array}{c}\mathcal{B}\left({\Xi}_c^{+}\to p{K}_S^0\right)=\left(7.16\pm 0.46\pm 0.20\pm 3.21\right)\times {10}^{-4},\\ {}\mathcal{B}\left({\Xi}_c^{+}\to \Lambda {\pi}^{+}\right)=\left(4.52\pm 0.41\pm 0.26\pm 2.03\right)\times {10}^{-4},\\ {}\mathcal{B}\left({\Xi}_c^{+}\to {\Sigma}^0{\pi}^{+}\right)=\left(1.20\pm 0.08\pm 0.07\pm 0.54\right)\times {10}^{-3}.\end{array}} $</EquationSource> </Equation>The first and second uncertainties above are statistical and systematic, respectively, while the third ones arise from the uncertainty in <InlineEquation ID="IEq12"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_25717_Article_IEq12.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="136" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <mi mathvariant="script">B</mi> <mfenced close=")" open="("> <mrow> <msubsup> <mi mathvariant="normal">Ξ</mi> <mi>c</mi> <mo>+</mo> </msubsup> <mo>→</mo> <msup> <mi mathvariant="normal">Ξ</mi> <mo>−</mo> </msup> <msup> <mi>π</mi> <mo>+</mo> </msup> <msup> <mi>π</mi> <mo>+</mo> </msup> </mrow> </mfenced> </math></EquationSource> <EquationSource Format="TEX">$ \mathcal{B}\left({\Xi}_c^{+}\to {\Xi}^{-}{\pi}^{+}{\pi}^{+}\right) $</EquationSource> </InlineEquation>.

Observations of the singly Cabibbo-suppressed decays $ {\Xi}_c^{+}\to p{K}_S^0 $, $ {\Xi}_c^{+}\to \Lambda {\pi}^{+} $, and $ {\Xi}_c^{+}\to {\Sigma}^0{\pi}^{+} $ at Belle and Belle II

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2025年3月11日

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I. Adachi,
L. Aggarwal,
N. Akopov,
M. Alhakami,
A. Aloisio,
N. Althubiti,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
T. Aushev,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
N. K. Baghel,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
M. Barrett,
J. Baudot,
A. Baur,
A. Beaubien,
J. Becker,
J. V. Bennett,
V. Bertacchi,
M. Bertemes,
E. Bertholet,
M. Bessner,
S. Bettarini,
B. Bhuyan,
F. Bianchi,
D. Biswas,
A. Bobrov,
D. Bodrov,
A. Bolz,
A. Bondar,
J. Borah,
A. Boschetti,
A. Bozek,
P. Branchini,
R. A. Briere,
T. E. Browder,
A. Budano,
S. Bussino,
Q. Campagna,
M. Campajola,
G. Casarosa,
C. Cecchi,
J. Cerasoli,
M.-C. Chang,
R. Cheaib,
P. Cheema,
K. Chilikin,
K. Chirapatpimol,
H.-E. Cho,
K. Cho,
S.-J. Cho,
S.-K. Choi,
S. Choudhury,
L. Corona,
J. X. Cui,
E. De La Cruz-Burelo,
S. A. De La Motte,
G. De Nardo,
G. De Pietro,
R. de Sangro,
M. Destefanis,
S. Dey,
A. Di Canto,
F. Di Capua,
J. Dingfelder,
Z. Doležal,
I. Domínguez Jiménez,
T. V. Dong,
M. Dorigo,
D. Dossett,
K. Dugic,
G. Dujany,
P. Ecker,
D. Epifanov,
P. Feichtinger,
T. Ferber,
T. Fillinger,
G. Finocchiaro,
F. Forti,
B. G. Fulsom,
A. Gabrielli,
M. Garcia-Hernandez,
G. Gaudino,
V. Gaur,
A. Gaz,
A. Gellrich,
G. Ghevondyan,
D. Ghosh,
H. Ghumaryan,
G. Giakoustidis,
R. Giordano,
A. Giri,
P. Gironella Gironell,
B. Gobbo,
R. Godang,
O. Gogota,
P. Goldenzweig,
W. Gradl,
E. Graziani,
D. Greenwald,
Z. Gruberová,
K. Gudkova,
I. Haide,
C. Harris,
H. Hayashii,
A. Heidelbach,
I. Heredia de la Cruz,
M. Hernández Villanueva,
T. Higuchi,
M. Hoek,
M. Hohmann,
R. Hoppe,
P. Horak,
T. Humair,
T. Iijima,
K. Inami,
N. Ipsita,
A. Ishikawa,
R. Itoh,
M. Iwasaki,
D. Jacobi,
W. W. Jacobs,
D. E. Jaffe,
E.-J. Jang,
Y. Jin,
A. Johnson,
H. Junkerkalefeld,
M. Kaleta,
A. B. Kaliyar,
J. Kandra,
G. Karyan,
T. Kawasaki,
F. Keil,
C. Ketter,
C. Kiesling,
C.-H. Kim,
D. Y. Kim,
J.-Y. Kim,
K.-H. Kim,
Y.-K. Kim,
K. Kinoshita,
P. Kodyš,
T. Koga,
S. Kohani,
K. Kojima,
A. Korobov,
S. Korpar,
E. Kovalenko,
R. Kowalewski,
P. Križan,
P. Krokovny,
T. Kuhr,
Y. Kulii,
R. Kumar,
K. Kumara,
T. Kunigo,
A. Kuzmin,
Y.-J. Kwon,
S. Lacaprara,
K. Lalwani,
T. Lam,
L. Lanceri,
J. S. Lange,
T. S. Lau,
M. Laurenza,
R. Leboucher,
F. R. Le Diberder,
M. J. Lee,
P. Leo,
L. K. Li,
Q. M. Li,
W. Z. Li,
Y. Li,
Y. B. Li,
Y. P. Liao,
J. Libby,
J. Lin,
M. H. Liu,
Q. Y. Liu,
Z. Q. Liu,
D. Liventsev,
S. Longo,
T. Lueck,
C. Lyu,
Y. Ma,
C. Madaan,
M. Maggiora,
R. Maiti,
G. Mancinelli,
R. Manfredi,
M. Mantovano,
D. Marcantonio,
S. Marcello,
C. Marinas,
C. Martellini,
A. Martens,
T. Martinov,
L. Massaccesi,
M. Masuda,
D. Matvienko,
M. Maushart,
J. A. McKenna,
F. Meier,
D. Meleshko,
M. Merola,
C. Miller,
M. Mirra,
S. Mitra,
H. Miyake,
S. Moneta,
H.-G. Moser,
R. Mussa,
I. Nakamura,
M. Nakao,
Y. Nakazawa,
M. Naruki,
Z. Natkaniec,
A. Natochii,
M. Nayak,
G. Nazaryan,
M. Neu,
S. Nishida,
S. Ogawa,
H. Ono,
Y. Onuki,
G. Pakhlova,
S. Pardi,
H. Park,
J. Park,
K. Park,
S.-H. Park,
S. Patra,
T. K. Pedlar,
I. Peruzzi,
R. Peschke,
R. Pestotnik,
L. E. Piilonen,
T. Podobnik,
S. Pokharel,
C. Praz,
S. Prell,
E. Prencipe,
M. T. Prim,
H. Purwar,
S. Raiz,
K. Ravindran,
J. U. Rehman,
M. Reif,
S. Reiter,
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L. Reuter,
D. Ricalde Herrmann,
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G. Rizzo,
M. Roehrken,
J. M. Roney,
A. Rostomyan,
D. A. Sanders,
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L. Santelj,
V. Savinov,
B. Scavino,
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Y. Seino,
A. Selce,
K. Senyo,
J. Serrano,
M. E. Sevior,
C. Sfienti,
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C. P. Shen,
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T. Shillington,
T. Shimasaki,
J.-G. Shiu,
D. Shtol,
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F. Simon,
J. Skorupa,
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M. Sobotzik,
A. Soffer,
A. Sokolov,
E. Solovieva,
S. Spataro,
B. Spruck,
W. Song,
M. Starič,
P. Stavroulakis,
R. Stroili,
M. Sumihama,
N. Suwonjandee,
H. Svidras,
M. Takizawa,
U. Tamponi,
K. Tanida,
F. Tenchini,
A. Thaller,
O. Tittel,
E. Torassa,
K. Trabelsi,
I. Tsaklidis,
I. Ueda,
K. Unger,
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K. Uno,
S. Uno,
P. Urquijo,
Y. Ushiroda,
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M. Veronesi,
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V. Vobbilisetti,
R. Volpe,
S. Wallner,
M.-Z. Wang,
A. Warburton,
M. Watanabe,
S. Watanuki,
C. Wessel,
E. Won,
X. P. Xu,
B. D. Yabsley,
S. Yamada,
W. Yan,
J. Yelton,
J. H. Yin,
K. Yoshihara,
C. Z. Yuan,
J. Yuan,
Y. Yusa,
L. Zani,
V. Zhilich,
J. S. Zhou,
Q. D. Zhou,
L. Zhu,
R. Žlebčík

摘要

Using data samples of 983.0 fb⁻¹ and 427.9 fb⁻¹ accumulated with the Belle and Belle II detectors operating at the KEKB and SuperKEKB asymmetric-energy e⁺e⁻ colliders, singly Cabibbo-suppressed decays $Ξ_{c}^{+} \to p K_{S}^{0}$ $ {\Xi}_c^{+}\to p{K}_S^0 $ , $Ξ_{c}^{+} \to Λ π^{+}$ $ {\Xi}_c^{+}\to \Lambda {\pi}^{+} $ , and $Ξ_{c}^{+} \to Σ^{0} π^{+}$ $ {\Xi}_c^{+}\to {\Sigma}^0{\pi}^{+} $ are observed for the first time. The ratios of branching fractions of $Ξ_{c}^{+} \to p K_{S}^{0}$ $ {\Xi}_c^{+}\to p{K}_S^0 $ , $Ξ_{c}^{+} \to Λ π^{+}$ $ {\Xi}_c^{+}\to \Lambda {\pi}^{+} $ , and $Ξ_{c}^{+} \to Σ^{0} π^{+}$ $ {\Xi}_c^{+}\to {\Sigma}^0{\pi}^{+} $ relative to that of $Ξ_{c}^{+} \to Ξ^{-} π^{+} π^{+}$ $ {\Xi}_c^{+}\to {\Xi}^{-}{\pi}^{+}{\pi}^{+} $ are measured to be $\begin{matrix} \frac{B (Ξ_{c}^{+} \to p K_{S}^{0})}{B (Ξ_{c}^{+} \to Ξ^{-} π^{+} π^{+})} = (2.47 \pm 0.16 \pm 0.07) %, \\ \frac{B (Ξ_{c}^{+} \to Λ π^{+})}{B (Ξ_{c}^{+} \to Ξ^{-} π^{+} π^{+})} = (1.56 \pm 0.14 \pm 0.09) %, \\ \frac{B (Ξ_{c}^{+} \to Σ^{0} π^{+})}{B (Ξ_{c}^{+} \to Ξ^{-} π^{+} π^{+})} = (4.13 \pm 0.26 \pm 0.22) % . \end{matrix}$ $ {\displaystyle \begin{array}{c}\frac{\mathcal{B}\left({\Xi}_c^{+}\to p{K}_S^0\right)}{\mathcal{B}\left({\Xi}_c^{+}\to {\Xi}^{-}{\pi}^{+}{\pi}^{+}\right)}=\left(2.47\pm 0.16\pm 0.07\right)\%,\\ {}\frac{\mathcal{B}\left({\Xi}_c^{+}\to \Lambda {\pi}^{+}\right)}{\mathcal{B}\left({\Xi}_c^{+}\to {\Xi}^{-}{\pi}^{+}{\pi}^{+}\right)}=\left(1.56\pm 0.14\pm 0.09\right)\%,\\ {}\frac{\mathcal{B}\left({\Xi}_c^{+}\to {\Sigma}^0{\pi}^{+}\right)}{\mathcal{B}\left({\Xi}_c^{+}\to {\Xi}^{-}{\pi}^{+}{\pi}^{+}\right)}=\left(4.13\pm 0.26\pm 0.22\right)\%.\end{array}} $

Multiplying these values by the branching fraction of the normalization channel, $B (Ξ_{c}^{+} \to Ξ^{-} π^{+} π^{+}) = (2.9 \pm 1.3) %$ $ \mathcal{B}\left({\Xi}_c^{+}\to {\Xi}^{-}{\pi}^{+}{\pi}^{+}\right)=\left(2.9\pm 1.3\right)\% $ , the absolute branching fractions are determined to be $\begin{matrix} B (Ξ_{c}^{+} \to p K_{S}^{0}) = (7.16 \pm 0.46 \pm 0.20 \pm 3.21) \times 10^{- 4}, \\ B (Ξ_{c}^{+} \to Λ π^{+}) = (4.52 \pm 0.41 \pm 0.26 \pm 2.03) \times 10^{- 4}, \\ B (Ξ_{c}^{+} \to Σ^{0} π^{+}) = (1.20 \pm 0.08 \pm 0.07 \pm 0.54) \times 10^{- 3} . \end{matrix}$ $ {\displaystyle \begin{array}{c}\mathcal{B}\left({\Xi}_c^{+}\to p{K}_S^0\right)=\left(7.16\pm 0.46\pm 0.20\pm 3.21\right)\times {10}^{-4},\\ {}\mathcal{B}\left({\Xi}_c^{+}\to \Lambda {\pi}^{+}\right)=\left(4.52\pm 0.41\pm 0.26\pm 2.03\right)\times {10}^{-4},\\ {}\mathcal{B}\left({\Xi}_c^{+}\to {\Sigma}^0{\pi}^{+}\right)=\left(1.20\pm 0.08\pm 0.07\pm 0.54\right)\times {10}^{-3}.\end{array}} $

The first and second uncertainties above are statistical and systematic, respectively, while the third ones arise from the uncertainty in $B (Ξ_{c}^{+} \to Ξ^{-} π^{+} π^{+})$ $ \mathcal{B}\left({\Xi}_c^{+}\to {\Xi}^{-}{\pi}^{+}{\pi}^{+}\right) $ .

Observations of the singly Cabibbo-suppressed decays \( {\Xi}_c^{+}\to p{K}_S^0 \), \( {\Xi}_c^{+}\to \Lambda {\pi}^{+} \), and \( {\Xi}_c^{+}\to {\Sigma}^0{\pi}^{+} \) at Belle and Belle II

摘要