The first evidence for the decay <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>B</mi></mrow><mrow><mo>+</mo></mrow></msup><mo stretchy="false">→</mo><msup><mrow><mi>π</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math> is reported using proton-proton collision data recorded by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>9</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math>. A signal excess with a significance of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>3.2</mn><mi>σ</mi></mrow></math> is observed and the branching fraction is measured to be <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="script">B</mi><mo stretchy="false">(</mo><msup><mrow><mi>B</mi></mrow><mrow><mo>+</mo></mrow></msup><mo stretchy="false">→</mo><msup><mrow><mi>π</mi></mrow><mrow><mo>+</mo></mrow></msup><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><mo>=</mo><mo stretchy="false">(</mo><msubsup><mrow><mn>2.4</mn></mrow><mrow><mo>−</mo><mn>0.8</mn></mrow><mrow><mo>+</mo><mn>0.9</mn></mrow></msubsup><msubsup><mrow><mtext> </mtext></mrow><mrow><mo>−</mo><mn>0.2</mn></mrow><mrow><mo>+</mo><mn>0.4</mn></mrow></msubsup><mo stretchy="false">)</mo><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>8</mn></mrow></msup></mrow></math>, where the first set of uncertainties is statistical and the second is systematic. The result is consistent with the Standard Model expectation.

Netherlands

R. Aaij

United Kingdom

A.S.W. Abdelmotteleb

Switzerland

C. Abellan Beteta

F. Abudinén

T. Ackernley

United States

A.A. Adefisoye

Spain

B. Adeva

M. Adinolfi

P. Adlarson

France

C. Agapopoulou

C.A. Aidala

Z. Ajaltouni

S. Akar

K. Akiba

Poland

M. Akthar

Italy

P. Albicocco

Germany

J. Albrecht

R. Aleksiejunas

CERN

F. Alessio

P. Alvarez Cartelle

R. Amalric

Brazil

S. Amato

J.L. Amey

Y. Amhis

China

L. An

L. Anderlini

M. Andersson

P. Andreola

M. Andreotti

S. Andres Estrada

A. Anelli

D. Ao

C. Arata

F. Archilli

Z. Areg

M. Argenton

Costa Rica

S. Arguedas Cuendis

L. Arnone

A. Artamonov

M. Artuso

E. Aslanides

R. Ataíde Da Silva

M. Atzeni

B. Audurier

J.A. Authier

D. Bacher

I. Bachiller Perea

S. Bachmann

M. Bachmayer

J.J. Back

P. Baladron Rodriguez

V. Balagura

A. Balboni

W. Baldini

Z. Baldwin

L. Balzani

H. Bao

J. Baptista de Souza Leite

C. Barbero Pretel

M. Barbetti

I.R. Barbosa

R.J. Barlow

M. Barnyakov

S. Barsuk

W. Barter

J. Bartz

S. Bashir

B. Batsukh

P.B. Battista

A. Bay

A. Beck

M. Becker

F. Bedeschi

I.B. Bediaga

N.A. Behling

S. Belin

A. Bellavista

K. Belous

I. Belov

I. Belyaev

G. Benane

G. Bencivenni

E. Ben-Haim

A. Berezhnoy

R. Bernet

S. Bernet Andres

A. Bertolin

F. Betti

J. Bex

O. Bezshyyko

S. Bhattacharya

M.S. Bieker

N.V. Biesuz

A. Biolchini

M. Birch

F.C.R. Bishop

A. Bitadze

A. Bizzeti

T. Blake

F. Blanc

First Evidence of the Decay <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>B</mi><mo>+</mo></msup><mo stretchy="false">→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></math>

In this study, we calculate the <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>γ</mi><mi>Z</mi></mrow></math>-exchange contribution to elastic <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>e</mi><mi>p</mi></mrow></math> scattering at large momentum transfer within perturbative quantum chromodynamics (pQCD). We present analytical expressions for the <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>γ</mi><mi>Z</mi></mrow></math>-exchange contributions to the amplitudes. We also estimate the asymptotic behaviors of the amplitude contributions and of the physical quantity <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>A</mi><mtext>PV</mtext></msub></math> at high momentum transfer. These asymptotic behaviors determine the subtraction order in the dispersion relations (DRs) satisfied by the amplitudes. At high <math xmlns="http://www.w3.org/1998/Math/MathML"><msup><mi>Q</mi><mn>2</mn></msup></math> beyond the forward limit, our pQCD analysis shows that this subtraction order is fixed by the high-<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>ν</mi></math> behavior of the amplitude coefficients <math xmlns="http://www.w3.org/1998/Math/MathML"><msubsup><mi>c</mi><mi>i</mi><mrow><mi>γ</mi><mi>Z</mi><mo>,</mo><mtext>PV</mtext></mrow></msubsup></math>, and that <math xmlns="http://www.w3.org/1998/Math/MathML"><msubsup><mi>c</mi><mrow><mn>3</mn><mo>,</mo><mi>A</mi></mrow><mrow><mi>γ</mi><mi>Z</mi><mo>,</mo><mtext>PV</mtext></mrow></msubsup></math> requires a once-subtracted DR. Within the present pQCD framework and the adopted proton distribution amplitudes, these high-energy results also provide nontrivial constraints on low-energy DR assumptions.

Qian-Qian Guo

Hui-Yun Cao

Hai-Qing Zhou

<math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>γ</mi><mi>Z</mi></mrow></math>-exchange contribution in elastic <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>e</mi><mi>p</mi></mrow></math> scattering by perturbative QCD

The Real Higgs Triplet model, known as the $$\varDelta $$ SM, is a minimal extension of the Standard Model (SM) obtained by adding a hypercharge 0 triplet ( $$\varDelta $$ ). This simple model is motivated by the multi-lepton anomalies and excesses in di-photon, $$Z\gamma $$ , and $\textit{WW}$ spectra at $$\approx 152$$ GeV. The model contains, in addition to the SM particle content, a $\textit{CP}$-even neutral Higgs ( $$\varDelta ^0$$ ) and a charged state ( $$\varDelta ^\pm $$ ), which are quasi-degenerate in mass. Observing the charged scalar at the LHC and measuring its mass is very challenging, since it dominantly decays to $\textit{WZ}$, $\textit{tb}$, and $$\tau \nu $$ . In this article, we consider the discovery prospects of the charged Higgs with mass 150 GeV at future electron-positron colliders. Taking into account $$e^+e^- \rightarrow \gamma ^*,Z^* \rightarrow \varDelta ^\pm \varDelta ^\mp $$ as the production mechanism and the dominant decay modes, we define three signal regions (SR) to study the 150 GeV charged Higgs properties: SR1: $$\ge 3j + 1\ell $$ , SR2: $$\ge 3\ell + \tau _{\text {had}}$$ , SR3: $$\ge 4j + \tau _{\text {had}}$$ . For $$m_{\varDelta ^\pm }=150\,\text {GeV}$$ , a $$5\sigma $$ significance can be achieved in SR1 with an integrated luminosity of less than $$1\text {~fb}^{-1}$$ . SR2 is very clean with leptonic final states having low background and small systematic uncertainties. Furthermore, SR3 is crucial for reconstructing the charged scalar invariant mass, which can be measured with $$\mathcal {O}(1)$$ GeV accuracy with an integrated luminosity of $$500\text {~fb}^{-1}$$ .

South Africa

India

Siddharth Maharathy

Phodiso Maroeshe

Paballo Ndhlovu

Srimoy Bhattacharya

Andreas Crivellin

Mukesh Kumar

Rachid Mazini

Bruce Mellado

Discovery prospects for the 150 GeV charged scalar at future $$e^+e^-$$ colliders

The first search for the lepton-flavor violating decays <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>B</mi></mrow><mrow><mo>+</mo></mrow></msup><mo stretchy="false">→</mo><mrow><msup><mrow><mi>π</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>μ</mi></mrow><mrow><mo>±</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>∓</mo></mrow></msup></mrow></mrow></math> in proton-proton collisions is presented, using data collected by the LHCb experiment between 2011 and 2018, corresponding to an integrated luminosity of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>9</mn><mtext> </mtext><mtext> </mtext><msup><mrow><mi>fb</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math>. No significant signal is observed and an upper limit on the branching fraction is set at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="script">B</mi><mo stretchy="false">(</mo><mrow><msup><mrow><mi>B</mi></mrow><mrow><mo>+</mo></mrow></msup><mo stretchy="false">→</mo><mrow><msup><mrow><mi>π</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>μ</mi></mrow><mrow><mo>±</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>∓</mo></mrow></msup></mrow></mrow><mo stretchy="false">)</mo><mo>&lt;</mo><mn>1.8</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>9</mn></mrow></msup></mrow></math> at the 90% confidence level, 2 orders of magnitude more restrictive than the most stringent upper limit to date. This is the first constraint on lepton-flavor violating <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi><mo stretchy="false">→</mo><mi>d</mi></math> quark transitions at the LHC and also sets the most stringent upper limits to date on <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi><mo stretchy="false">→</mo><mrow><mi>d</mi><msup><mi>μ</mi><mo>±</mo></msup><msup><mi>e</mi><mo>∓</mo></msup></mrow></math> transitions. Limits on left-handed and scalar scenarios beyond the standard model are also reported.

M. Abdelfatah

Z.B. Bai

S. Baron

A. Bavarchee

J.L.M. Berkey

J.E. Blank

S. Blusk

J.A. Boelhauve

O. Boente Garcia

Search for the Lepton-Flavor Violating Decays <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>B</mi></mrow><mrow><mo>+</mo></mrow></msup><mo stretchy="false">→</mo><msup><mrow><mi>π</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>μ</mi></mrow><mrow><mo>±</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>∓</mo></mrow></msup></mrow></math>

We explore the sensitivity of the <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><msup><mi>K</mi><mo>+</mo></msup><msup><mi>K</mi><mo>−</mo></msup><mn>2</mn><msup><mi>π</mi><mn>0</mn></msup></math> cross section to the magnetic dipole moment (MDM) of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>K</mi><mo>*</mo></msup></math> vector meson. We describe the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>γ</mi><mo>*</mo></msup><mo stretchy="false">→</mo><mn>2</mn><mi>K</mi><mn>2</mn><mi>π</mi></math> vertex using a vector meson dominance model, including the intermediate resonant contributions relevant for energies below 2.4 GeV. Using <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>B</mi><mi>A</mi><mi>B</mi><mi>A</mi><mi>R</mi></math> data for this process, we show that this observable is indeed sensitive to the MDM of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>K</mi><mo>*</mo></msup></math>; we obtain a central value for the MDM of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>μ</mi><msup><mi>K</mi><mo>*</mo></msup></msub><mo>=</mo><mn>4.5</mn></math> and an upper bound of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mover accent="true"><mi>μ</mi><mo stretchy="false">¯</mo></mover><msup><mi>K</mi><mo>*</mo></msup></msub><mo>=</mo><mn>6.3</mn></math>, in units of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>e</mi><mo>/</mo><mn>2</mn><msub><mi>m</mi><msup><mi>K</mi><mo>*</mo></msup></msub></math>. We emphasize the need for higher precision data to provide a first data-driven determination of this parameter to confront it with theoretical predictions.

Mexico

Luis A. Jiménez Pérez

Antonio Rojas

Genaro Toledo

Effect of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>K</mi><mo>*</mo></msup></math> meson magnetic dipole moment on the <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><msup><mi>K</mi><mo>+</mo></msup><msup><mi>K</mi><mo>−</mo></msup><msup><mi>π</mi><mn>0</mn></msup><msup><mi>π</mi><mn>0</mn></msup></math> cross section

The process of elastic scattering of photons ( $$\gamma \gamma \rightarrow \gamma \gamma $$ , light-by-light scattering) has attracted significant interest in recent years as a loop-induced process sensitive to all charged particles. To date, this process has been studied through Delbrück scattering, photon splitting in the nuclear Coulomb field, and ultra-peripheral heavy-ion collisions at the LHC. Future precision measurements are anticipated at high-luminosity $$e^+e^-$$ colliders (SuperKEKb, FCC, CEPC, ILC, CLIC), their $$e^-e^-$$ options, and $$\gamma \gamma $$ colliders based on the backscattering of laser photons. In this paper, we show that background QED processes severely limit the study of elastic light-by-light scattering at $$e^+e^-$$ colliders. For the $$e^+e^-$$ case, the main background arises from $$e^+e^-$$ annihilation into two photons within the detector acceptance after the initial electron and positron emit hard ISR photons at small angles. Since only two photons with a small total transverse momentum are registered in the detector in both cases, this process effectively mimics the $$\gamma \gamma \rightarrow \gamma \gamma $$ signal with a significantly larger cross section at high invariant masses. Other relevant background QED processes for both types of collisions are also comprehensively analyzed and discussed.

Russia

K. Beloborodov

T. Kharlamova

V. Telnov

Impact of QED backgrounds on light-by-light scattering measurements at $$e^+e^-$$ and $$e^-e^-$$ colliders

Using a sample of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">(</mo><mn>10087</mn><mo>±</mo><mn>44</mn><mo stretchy="false">)</mo><mo>×</mo><msup><mn>10</mn><mn>6</mn></msup><mtext> </mtext><mtext> </mtext><mi>J</mi><mo>/</mo><mi>ψ</mi></math> events collected with the BESIII detector, an improved measurement of the decay <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>η</mi><mo>′</mo></msup><mo stretchy="false">→</mo><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mi>ω</mi></math>, with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ω</mi><mo stretchy="false">→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup><msup><mi>π</mi><mn>0</mn></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>π</mi><mn>0</mn></msup><mo stretchy="false">→</mo><mi>γ</mi><mi>γ</mi></math> is performed. The branching fraction is determined to be <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">B</mi><mo stretchy="false">(</mo><msup><mi>η</mi><mo>′</mo></msup><mo stretchy="false">→</mo><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mi>ω</mi><mo stretchy="false">)</mo><mo>=</mo><mo stretchy="false">(</mo><mn>1.79</mn><mo>±</mo><mn>0.09</mn><mo>±</mo><mn>0.12</mn><mo stretchy="false">)</mo><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>4</mn></mrow></msup></math>, where the first uncertainty is statistical and the second is systematic. This result is consistent with the previous measurement and is obtained with significantly improved precision. Furthermore, the first measurement of the transition form factor cutoff parameter for this decay is reported, with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi mathvariant="normal">Λ</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup><mo>=</mo><mo stretchy="false">(</mo><mn>2.92</mn><mo>±</mo><mn>0.83</mn><mo>±</mo><mn>0.15</mn><mo stretchy="false">)</mo><mtext> </mtext><mtext> </mtext><msup><mrow><mi>GeV</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math>. These measurements provide valuable input for understanding the internal structure of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>η</mi><mo>′</mo></msup></math> meson and testing theoretical models.

M. Ablikim

M.N. Achasov

Sweden

X.C. Ai

C.S. Akondi

R. Aliberti

A. Amoroso

Q. An

Y.H. An

Y. Bai

JINR

O. Bakina

H.R. Bao

X.L. Bao

M. Barbagiovanni

V. Batozskaya

Mongolia

K. Begzsuren

N. Berger

M. Berlowski

M.B. Bertani

D. Bettoni

F. Bianchi

E. Bianco

A. Bortone

I. Boyko

R.A. Briere

A. Brueggemann

D. Cabiati

H. Cai

M.H. Cai

X. Cai

A. Calcaterra

G.F. Cao

N. Cao

Türkiye

S.A. Cetin

X.Y. Chai

J.F. Chang

T.T. Chang

G.R. Che

Y.Z. Che

C.H. Chen

Chao Chen

G. Chen

Improved measurement of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>η</mi></mrow><mrow><mo>′</mo></mrow></msup><mo stretchy="false">→</mo><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup><mi>ω</mi></mrow></math>