We apply the light-cone QCD sum rules with chiral currents to compute transition form factors of the semileptonic decay of the charmed and bottom scalar mesons <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><mo>/</mo><mi>B</mi></math> to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>a</mi><mn>0</mn></msub><mo stretchy="false">(</mo><mn>980</mn><mo stretchy="false">)</mo><msup><mi>l</mi><mo>+</mo></msup><msub><mi>ν</mi><mi>l</mi></msub></math> <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mo stretchy="false">(</mo><mi>l</mi><mo>=</mo><mi>e</mi><mo>,</mo><mi>μ</mi><mo stretchy="false">)</mo></mrow></math>, where the scalar meson <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>a</mi><mn>0</mn></msub><mo stretchy="false">(</mo><mn>980</mn><mo stretchy="false">)</mo></math> are firstly regarded as two quark states, and contributions from the tetraquark component are then added via proper modulation of four distribution amplitudes considered. The obtained transition form factors and branching fraction are free of the contribution from the light-cone distribution amplitudes at the level of twist-three and two simple relations connecting their form factors are obtained. Our computations indicates that the decay branch fractions are on the margin of the measurements reported by the Beijing Spectrometer III in the pure two-quark scenario and are in good agreement with observations when tetraquark component is considered.

China

Di Gao

JiangShan Lan

Duojie Jia

Xingbo Zhao

Yanjun Sun

Transition form factors for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><mo>/</mo><mi>B</mi></math> to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>a</mi><mn>0</mn></msub><mo stretchy="false">(</mo><mn>980</mn><mo stretchy="false">)</mo></math> from light-cone QCD sum rules

Results are presented on <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>χ</mi></mrow><mrow><mi>b</mi><mn>1</mn><mo>,</mo><mn>2</mn></mrow></msub><mo stretchy="false">(</mo><mn>2</mn><mi>P</mi><mo stretchy="false">)</mo><mo stretchy="false">→</mo><mi>ω</mi><mi mathvariant="normal">ϒ</mi><mo stretchy="false">(</mo><mn>1</mn><mi>S</mi><mo stretchy="false">)</mo></mrow></math> transitions from <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mrow><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow><mo stretchy="false">→</mo><mi mathvariant="normal">ϒ</mi><mo stretchy="false">(</mo><mn>3</mn><mi>S</mi><mo stretchy="false">)</mo><mo stretchy="false">→</mo><mi>γ</mi><msub><mrow><mi>χ</mi></mrow><mrow><mi>b</mi><mn>1</mn><mo>,</mo><mn>2</mn></mrow></msub><mo stretchy="false">(</mo><mn>2</mn><mi>P</mi><mo stretchy="false">)</mo></mrow></math> decays. The data were collected with the BABAR detector at the PEP-II asymmetric-energy <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></math> collider at SLAC. The integrated luminosity of the data sample is <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>28.0</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math>, corresponding to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>121.3</mn><mo>×</mo><msup><mn>10</mn><mn>6</mn></msup></math> <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">ϒ</mi><mo stretchy="false">(</mo><mn>3</mn><mi>S</mi><mo stretchy="false">)</mo></math> decays. Signals of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>χ</mi><mrow><mi>b</mi><mn>1</mn><mo>,</mo><mn>2</mn></mrow></msub><mo stretchy="false">(</mo><mn>2</mn><mi>P</mi><mo stretchy="false">)</mo></math> are observed over a negligible background. Improved precision measurements of branching fractions are obtained. First measurements of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>χ</mi><mrow><mi>b</mi><mn>1</mn><mo>,</mo><mn>2</mn></mrow></msub><mo stretchy="false">(</mo><mn>2</mn><mi>P</mi><mo stretchy="false">)</mo></math> angular distributions are performed. No evidence is found for the presence of a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mi>χ</mi><mrow><mi>b</mi><mn>0</mn></mrow></msub><mo stretchy="false">(</mo><mn>2</mn><mi>P</mi><mo stretchy="false">)</mo></mrow><mo stretchy="false">→</mo><mi>ω</mi><mrow><mi mathvariant="normal">ϒ</mi><mrow><mo stretchy="false">(</mo><mn>1</mn><mi>S</mi><mo stretchy="false">)</mo></mrow></mrow></math> decay mode.

J.P. Lees

V. Poireau

V. Tisserand

E. Grauges

A. Palano

G. Eigen

D.N. Brown

Yu. G. Kolomensky

M. Fritsch

H. Koch

R. Cheaib

C. Hearty

T.S. Mattison

J.A. McKenna

R.Y. So

V.E. Blinov

A.R. Buzykaev

V.P. Druzhinin

E.A. Kozyrev

E.A. Kravchenko

S.I. Serednyakov

Yu. I. Skovpen

E.P. Solodov

K. Yu. Todyshev

A.J. Lankford

B. Dey

J.W. Gary

O. Long

A.M. Eisner

W.S. Lockman

W. Panduro Vazquez

D.S. Chao

C.H. Cheng

B. Echenard

K.T. Flood

D.G. Hitlin

Y. Li

D.X. Lin

S. Middleton

T.S. Miyashita

P. Ongmongkolkul

J. Oyang

F.C. Porter

M. Röhrken

B.T. Meadows

M.D. Sokoloff

J.G. Smith

S.R. Wagner

D. Bernard

M. Verderi

D. Bettoni

C. Bozzi

R. Calabrese

G. Cibinetto

E. Fioravanti

I. Garzia

E. Luppi

V. Santoro

A. Calcaterra

R. de Sangro

G. Finocchiaro

S. Martellotti

P. Patteri

I.M. Peruzzi

M. Piccolo

M. Rotondo

A. Zallo

S. Passaggio

C. Patrignani

B.J. Shuve

H.M. Lacker

B. Bhuyan

U. Mallik

C. Chen

J. Cochran

S. Prell

A.V. Gritsan

N. Arnaud

M. Davier

F. Le Diberder

A.M. Lutz

G. Wormser

D.J. Lange

D.M. Wright

J.P. Coleman

D.E. Hutchcroft

D.J. Payne

C. Touramanis

A.J. Bevan

M. Bona

F. Di Lodovico

G. Cowan

Sw. Banerjee

C.L. Davis

A.G. Denig

W. Gradl

K. Griessinger

A. Hafner

K.R. Schubert

Study of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>χ</mi></mrow><mrow><mi>b</mi><mn>1</mn><mo>,</mo><mn>2</mn></mrow></msub><mo stretchy="false">(</mo><mn>2</mn><mi>P</mi><mo stretchy="false">)</mo><mo stretchy="false">→</mo><mi>ω</mi><mi mathvariant="normal">ϒ</mi><mo stretchy="false">(</mo><mn>1</mn><mi>S</mi><mo stretchy="false">)</mo></mrow></math> transitions in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">ϒ</mi><mo stretchy="false">(</mo><mn>3</mn><mi>S</mi><mo stretchy="false">)</mo><mo stretchy="false">→</mo><mi>γ</mi><msub><mrow><mi>χ</mi></mrow><mrow><mi>b</mi><mn>1</mn><mo>,</mo><mn>2</mn></mrow></msub><mo stretchy="false">(</mo><mn>2</mn><mi>P</mi><mo stretchy="false">)</mo></mrow></math> decays at BABAR

The scale of the seesaw mechanism is typically much larger than the electroweak scale. This hierarchy can be naturally explained by U(1) symmetry, which after spontaneous symmetry breaking, simultaneously generates Majorana masses for neutrinos and produces a network of cosmic strings. Such strings generate a gravitational wave (GW) spectrum which is expected to be almost uniform in frequency unless there is a departure from the usual early radiation domination. We explore this possibility in Type I, II and III seesaw frameworks, finding that only for Type-I, long-lived right-handed neutrinos (RHN) may provide a period of early matter domination for parts of the parameter space, even if they are thermally produced. Such a period leaves distinctive imprints in the GW spectrum in the form of characteristic breaks and a knee feature, arising due to the end and start of the periods of RHN domination. These features, if detected, directly determine the right-handed neutrino mass $\textit{M}$, and associated left-handed effective neutrino mass $$ \overset{\sim }{m} $$ of the dominating RHN. We find that GW detectors like LISA and ET could probe RHN masses in the range $\textit{M}$ ∈ [0.1, 10 ] GeV and effective neutrino masses in the $$ \overset{\sim }{m} $$ ∈ [10 , 10 ] eV range. We investigate the phenomenological implications of long-lived right-handed neutrinos for both local and global U(1) strings, focusing on dark matter production and leptogenesis. We map the viable and detectable parameter space for successful baryogenesis and asymmetric dark matter production from right-handed neutrino decays. We derive analytical and semi-analytical relations correlating the characteristic gravitational-wave frequencies to the neutrino parameters $$ \overset{\sim }{m} $$ and $\textit{M}$, as well as to the relic abundances of dark matter and baryons. We find that the detectable parameter space reaches the boundary of hierarchical leptogenesis and encompasses a substantial portion of the near-resonant regime.

Satyabrata Datta

Poland

United Kingdom

Anish Ghoshal

Angus Spalding

Graham White

Gravitational wave spectral shapes as a probe of long lived right-handed neutrinos, leptogenesis and dark matter. Global versus local $\textit{B}$ − $\textit{L}$ cosmic strings

We perform an improved perturbative QCD study of the decays <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>B</mi><mi>c</mi><mo>+</mo></msubsup><mo stretchy="false">→</mo><msub><mi>η</mi><mi>c</mi></msub><msup><mi>L</mi><mo>+</mo></msup></math>, where <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>L</mi></math> denotes the light ground-state pseudoscalar, vector mesons and the corresponding <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>p</mi></math>-wave scalar, axial-vector, and tensor ones, and predict their branching ratios (BRs) associated with relative ratios at leading order in the strong coupling <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>α</mi><mi>s</mi></msub></math>. Our results <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>BR</mi></mrow><mo stretchy="false">(</mo><msubsup><mi>B</mi><mi>c</mi><mo>+</mo></msubsup><mo stretchy="false">→</mo><msub><mi>η</mi><mi>c</mi></msub><msup><mi>π</mi><mo>+</mo></msup><mo stretchy="false">)</mo><mo>=</mo><mo stretchy="false">(</mo><mn>2.0</mn><msubsup><mn>3</mn><mrow><mo>−</mo><mn>0.41</mn></mrow><mrow><mo>+</mo><mn>0.53</mn></mrow></msubsup><mo stretchy="false">)</mo><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>3</mn></mrow></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>BR</mi></mrow><mo stretchy="false">(</mo><msubsup><mi>B</mi><mi>c</mi><mo>+</mo></msubsup><mo stretchy="false">→</mo><msub><mi>η</mi><mi>c</mi></msub><msup><mi>π</mi><mo>+</mo></msup><mo stretchy="false">)</mo><mo>/</mo><mrow><mi>BR</mi></mrow><mo stretchy="false">(</mo><msubsup><mi>B</mi><mi>c</mi><mo>+</mo></msubsup><mo stretchy="false">→</mo><mi>J</mi><mo>/</mo><mi>ψ</mi><msup><mi>π</mi><mo>+</mo></msup><mo stretchy="false">)</mo><mo>=</mo><mn>1.7</mn><msubsup><mn>4</mn><mrow><mo>−</mo><mn>0.50</mn></mrow><mrow><mo>+</mo><mn>0.66</mn></mrow></msubsup></math> are consistent with several available predictions in different approaches within uncertainties. Inputting the measured <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>η</mi><mi>c</mi></msub><mo stretchy="false">→</mo><mi>p</mi><mover accent="true"><mi>p</mi><mo stretchy="false">¯</mo></mover></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>η</mi><mi>c</mi></msub><mo stretchy="false">→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup><mo stretchy="false">(</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup><mo>,</mo><msup><mi>K</mi><mo>+</mo></msup><msup><mi>K</mi><mo>−</mo></msup><mo>,</mo><mi>p</mi><mover accent="true"><mi>p</mi><mo stretchy="false">¯</mo></mover><mo stretchy="false">)</mo></math> BRs with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>p</mi></math> here being a proton, we derive the multibody <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>B</mi><mi>c</mi><mo>+</mo></msubsup><mo stretchy="false">→</mo><msub><mi>η</mi><mi>c</mi></msub><mo stretchy="false">(</mo><mi>π</mi><mo>,</mo><mi>ρ</mi><msup><mo stretchy="false">)</mo><mo>+</mo></msup></math> BRs through secondary decay chains via resonance <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>η</mi><mi>c</mi></msub></math> under the narrow-width approximation, which might facilitate the (near-)future tests of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>B</mi><mi>c</mi></msub><mo stretchy="false">→</mo><msub><mi>η</mi><mi>c</mi></msub></math> decays. Under the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>q</mi><mover accent="true"><mi>q</mi><mo stretchy="false">¯</mo></mover></math> assignment for light scalars, different to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>B</mi><mi>c</mi></msub></math> decaying into <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi></math> plus a scalar meson and other <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>B</mi><mi>c</mi><mo>+</mo></msubsup><mo stretchy="false">→</mo><msub><mi>η</mi><mi>c</mi></msub><msup><mi>L</mi><mo>+</mo></msup></math> modes, surprisingly small <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi><mi>S</mi><mo>=</mo><mn>0</mn></math> BRs around <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>7</mn></mrow></msup><mo>−</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>9</mn></mrow></msup><mo stretchy="false">)</mo></math> and highly large ratios near <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><msup><mn>10</mn><mn>2</mn></msup><mo stretchy="false">)</mo></math> between the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi><mi>S</mi><mo>=</mo><mn>1</mn></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi><mi>S</mi><mo>=</mo><mn>0</mn></math> BRs are found in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>B</mi><mi>c</mi></msub></math> decays to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>η</mi><mi>c</mi></msub></math> plus light scalars, with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi></math> being strange number. Many large BRs and interesting ratios presented in this work could be tested by the Large Hadron Collider experiments, which would help us to examine the reliability of this improved perturbative QCD formalism for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>B</mi><mi>c</mi></msub></math>-meson decays and further understand the QCD dynamics in the considered decay modes as well as in the related hadrons.

Wen-Jing Zhang

Xin Liu

Improved perturbative QCD study of the decay <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>B</mi><mi>c</mi><mo>+</mo></msubsup><mo stretchy="false">→</mo><msub><mi>η</mi><mi>c</mi></msub><msup><mi>L</mi><mo>+</mo></msup></math>

We study the decays of $\textit{B}$ mesons into light pseudoscalar mesons under the SU(3) flavour symmetry. Assuming exact SU(3) symmetry at the level of the amplitudes leads to a simple parametrisation. Using the available experimental data and accounting for mixing effects in the $$ {B}_s^0 $$ branching ratios, we find that the data cannot be described with this assumption. We improve this parametrisation by including $\textit{factorizable}$ SU(3) -breaking effects. This new approach allows for an excellent description of the data, with a fit $\textit{p}$ value of 32$\textit{.}$3%. We provide posterior predictions for all observables and identify several decay channels that would significantly impact our analysis. Finally, we briefly compare our results with the predictions of QCD factorisation, paving the way to a more detailed analysis which could provide insights into QCD effects at low energy scales.

Netherlands

M. Marcos

France

M. Reboud

K. Vos

Detailed SU(3) flavour symmetry analysis of charmless two-body $\textit{B}$-meson decays including factorizable corrections

The precise measurement of the width difference ∆Γ among the mass eigenstates of the $\textit{B}$ - $$ {\overline{B}}_s $$ system requires the calculation of the corresponding decay matrix to order $\textit{α}$ /$\textit{m}$ . QCD corrections to power-suppressed terms in the Heavy Quark Expansion involve the renormalization of dimension-7 four-quark operators for which no general methodology is available yet. In the $$ \overline{\textrm{MS}} $$ scheme one-loop corrections to matrix elements of dimension-7 operators violate the power counting, but we find the responsible terms to be infrared-finite and show that they can be absorbed into finite counterterms proportional to dimension-6 operators. We calculate all these counterterms and subsequently verify the consistency of our results with hadronic matrix elements calculated in the limit of a large number $\textit{N}$ of colours. The condition of correct power counting implies constraints on the possible definitions of evanescent operators.

Armenia

Artyom Hovhannisyan

Germany

Ulrich Nierste

Decay matrix of $\textit{B}$- $$ \overline{B} $$ mixing: mixing of dimension-seven operators into dimension-six operators under renormalization

We present updated and comprehensive Standard Model predictions for the inclusive rare decay $$ B\to {X}_s\nu \overline{\nu} $$ . Using a state-of-the-art determination of the short-distance coefficient, including NLO QCD and electroweak effects, and implementing a consistent treatment of heavy-quark masses and power corrections within the kinetic scheme, we compute the total decay rate and the neutrino invariant mass spectrum. We incorporate all known perturbative contributions in the heavy quark limit up to $$ \mathcal{O}\left({\alpha}_s^3\right) $$ , evaluate non-perturbative corrections through the Heavy Quark Expansion up to $$ 1/{m}_b^3 $$ , and include estimates of four-quark operator matrix elements from HQET sum rules. We obtain the Standard Model branching ratios Br( $$ {B}^0\to {X}_s\nu \overline{\nu} $$ ) = (3.35 ± 0.10) × 10 and Br( $$ {B}^{+}\to {X}_s\nu \overline{\nu} $$ ) = (3.62 ± 0.11) × 10 , representing a significant improvement in both central value and precision compared to previous determinations. We also provide predictions for partial rates with kinematic cuts relevant to Belle II. Our results are timely in view of recent measurements of $$ B\to K\nu \overline{\nu} $$ and the first upper limits on inclusive $$ B\to {X}_s\nu \overline{\nu} $$ , and they offer a robust baseline for future searches for physics beyond the Standard Model in $$ b\to s\nu \overline{\nu} $$ transitions.

Italy

Matteo Fael

Jack Jenkins

United States

Enrico Lunghi

Switzerland

Slovenia

Zachary Polonsky

The Standard Model prediction for the rare decay $$ B\to {X}_s\nu \overline{\nu} $$

We present an analysis of the processes <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">→</mo><mi>η</mi><mi mathvariant="normal">ϒ</mi><mo stretchy="false">(</mo><mn>1</mn><mi>S</mi><mo stretchy="false">)</mo></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>η</mi><mi mathvariant="normal">ϒ</mi><mo stretchy="false">(</mo><mn>2</mn><mi>S</mi><mo stretchy="false">)</mo></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>γ</mi><msub><mi>X</mi><mi>b</mi></msub></math> with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>X</mi><mi>b</mi></msub><mo stretchy="false">→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup><msub><mi>χ</mi><mrow><mi>b</mi><mi>J</mi></mrow></msub><mo>,</mo><msub><mi>χ</mi><mrow><mi>b</mi><mi>J</mi></mrow></msub><mo stretchy="false">→</mo><mi>γ</mi><mi mathvariant="normal">ϒ</mi><mo stretchy="false">(</mo><mn>1</mn><mi>S</mi><mo stretchy="false">)</mo></math> (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>J</mi><mo>=</mo><mn>1</mn></mrow></math>, 2) reconstructed from <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>γ</mi><mi>γ</mi><msup><mrow><mi>π</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>π</mi></mrow><mrow><mo>−</mo></mrow></msup><msup><mrow><mo>ℓ</mo></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mo>ℓ</mo></mrow><mrow><mo>−</mo></mrow></msup></mrow></math> <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mo stretchy="false">(</mo><mo>ℓ</mo><mo>=</mo><mi>e</mi><mo>,</mo><mi>μ</mi><mo stretchy="false">)</mo></mrow></math> final states in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>19.6</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math> of Belle II data collected at four energy points near the peak of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">ϒ</mi><mo stretchy="false">(</mo><mn>10753</mn><mo stretchy="false">)</mo></math> resonance. Here, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>X</mi><mi>b</mi></msub></math> is a hypothetical bottomonium-sector partner of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>X</mi><mo stretchy="false">(</mo><mn>3872</mn><mo stretchy="false">)</mo></math>. In the process <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">→</mo><mi>η</mi><mi mathvariant="normal">ϒ</mi><mo stretchy="false">(</mo><mn>2</mn><mi>S</mi><mo stretchy="false">)</mo></math>, we observe a signal with a significance that exceeds <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>6.0</mn><mi>σ</mi></math> when all energy points are combined. A signal with a significance of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>4.2</mn><mi>σ</mi></mrow></math> is observed at a center-of-mass energy of 10.653 GeV, close to the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>B</mi><mo>*</mo></msup><msup><mover accent="true"><mi>B</mi><mo stretchy="false">¯</mo></mover><mo>*</mo></msup></math> threshold. At this energy, we measure <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>σ</mi><mo stretchy="false">(</mo><mi>η</mi><mi mathvariant="normal">ϒ</mi><mo stretchy="false">(</mo><mn>2</mn><mi>S</mi><mo stretchy="false">)</mo><mo stretchy="false">)</mo><mo>/</mo><mi>σ</mi><mo stretchy="false">(</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup><mi mathvariant="normal">ϒ</mi><mo stretchy="false">(</mo><mn>2</mn><mi>S</mi><mo stretchy="false">)</mo><mo stretchy="false">)</mo><mo>&gt;</mo><mn>23</mn></math> at the 90% confidence level, indicating a strong violation of heavy-quark spin symmetry. No significant signal is observed for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">→</mo><mi>η</mi><mi mathvariant="normal">ϒ</mi><mo stretchy="false">(</mo><mn>1</mn><mi>S</mi><mo stretchy="false">)</mo></math> or <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>γ</mi><msub><mi>X</mi><mi>b</mi></msub></math>. Upper limits on the Born cross sections for the processes <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">→</mo><mi>η</mi><mi mathvariant="normal">ϒ</mi><mo stretchy="false">(</mo><mn>1</mn><mi>S</mi><mo stretchy="false">)</mo></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">→</mo><mi>γ</mi><msub><mi>X</mi><mi>b</mi></msub></math> with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>X</mi><mi>b</mi></msub><mo stretchy="false">→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup><msub><mi>χ</mi><mrow><mi>b</mi><mi>J</mi></mrow></msub></math> are determined.

I. Adachi

L. Aggarwal

H. Ahmed

Y. Ahn

H. Aihara

N. Akopov

S. Alghamdi

M. Alhakami

A. Aloisio

N. Althubiti

K. Amos

M. Angelsmark

N. Anh Ky

C. Antonioli

D.M. Asner

H. Atmacan

T. Aushev

V. Aushev

M. Aversano

R. Ayad

V. Babu

H. Bae

N.K. Baghel

S. Bahinipati

P. Bambade

S. Bansal

M. Barrett

M. Bartl

J. Baudot

A. Baur

A. Beaubien

F. Becherer

J. Becker

J.V. Bennett

F.U. Bernlochner

V. Bertacchi

M. Bertemes

E. Bertholet

M. Bessner

S. Bettarini

V. Bhardwaj

F. Bianchi

T. Bilka

D. Biswas

A. Bobrov

D. Bodrov

A. Bondar

G. Bonvicini

A. Boschetti

A. Bozek

M. Bračko

P. Branchini

R.A. Briere

T.E. Browder

A. Budano

S. Bussino

Observation of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">→</mo><mi>η</mi><mi mathvariant="normal">ϒ</mi><mo stretchy="false">(</mo><mn>2</mn><mi>S</mi><mo stretchy="false">)</mo></math> and search for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup><mo stretchy="false">→</mo><mi>η</mi><mi mathvariant="normal">ϒ</mi><mo stretchy="false">(</mo><mn>1</mn><mi>S</mi><mo stretchy="false">)</mo></mrow></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>γ</mi><msub><mrow><mi>X</mi></mrow><mrow><mi>b</mi></mrow></msub></mrow></math> at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt></math> near 10.75 GeV