arXiv subjects

R. Ataíde Da Silva

Publications and source records attributed to R. Ataíde Da Silva.

At least 19 recordsLinked to original sources

arXiv2026

Measurement of the local and nonlocal amplitudes in $B^{+}\to K^{+}μ^{+}μ^{-}$ decays

This paper presents a thorough study of the local and nonlocal amplitudes in $B^+ \to K^+μ^+μ^-$ transitions through an amplitude analysis of the dimuon mass spectrum of the decay. The analysis is based on $pp$ collision data corresponding to an integrated luminosity of 8.4fb$^{-1}$ collected by the LHCb experiment. This measurement employs a model that describes both one-particle and two-particle nonlocal amplitudes across the entirety of the dimuon mass spectrum, enabling the determination of both short- and long-distance contributions to the decay. The compatibility of the Wilson coefficient combinations $C_9+C_9'$ and $C_{10}+C_{10}'$ with the Standard Model prediction is found to vary between $1.6\,σ$ and $4\,σ$, depending on the choice of local form factors.

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arXiv2026

Evidence for the decay $B^0_s\toϕη'$

Using a dataset corresponding to an integrated luminosity of $9 \,\textrm{fb}^{-1}$ collected in proton-proton collisions between 2011 and 2018 by the LHCb experiment, evidence is found for the decay $B^0_s\toϕη'$ with $3.5 σ$ significance. The branching ratio relative to the $B^0_s\toϕϕ$ decay is determined to be $R=(3.56 \pm 0.79\pm 0.18\pm 0.06)\times10^{-2}$. This corresponds to a branching fraction, $B(B^0_s\toϕη')=(0.66 \pm 0.15 \pm 0.03 \pm 0.02) \times 10^{-6}$ where, in both cases, the first uncertainty is statistical, the second systematic, and the third due to external branching fractions.

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arXiv2026

Branching fraction measurement of the $B^0\to K^+π^-μ^+μ^-$ decay at high dihadron mass

This Letter presents the first measurement of the $B^{0} \to K^{+}π^{-}μ^{+}μ^{-}$ differential branching fraction in the region of the dihadron $K^+π^-$ mass, $m_{Kπ}$, $1000< m_{Kπ} < 1835\,\text{MeV}/c^{2}$. This decay mode is mediated by the quark-level transition $b \to s\ell^{+}\ell^{-}$, for which the measured effective couplings show tensions with Standard Model predictions. The analysis is performed using proton-proton collision data collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of $8.4\,\text{fb}^{-1}$. The differential branching fraction is determined across different regions of dimuon mass squared, $q^2$, in the interval $0.1 < q^2 < 18.0\,\text{GeV}^2/c^{4}$, as well as in different regions of $ m_{Kπ}$ in the interval $1.1 < q^2 < 6.0\,\text{GeV}^2/c^{4}$. The results represent the first differential measurement of the branching fraction across $m_{Kπ}$ within the selected dihadron-mass region, and the first observation of the decay within this region above the $J/ψ$ resonance.

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arXiv2026

Energy-energy correlators within $Z$-tagged jets in proton-proton collisions at $\sqrt{s}$ = 13 TeV

Energy-energy correlators probe perturbative and nonperturbative QCD regimes of jet formation through momentum-weighted angular correlations between hadrons. First measurements in light-quark-enriched jets are presented for inclusive, like-sign, and opposite-sign charged-hadron pairs, using proton-proton collisions at LHCb. The results support universality of the confinement scale for light-quark-initiated jets across collision systems and the reported transverse momentum scale of the jet. In the charge-dependent measurements, opposite-sign correlations are enhanced as angular separation decreases down to the confinement-scale region, a behavior that is well described by simulations.

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arXiv2026

Measurement of the ratio of branching fractions $\mathcal{B}(B_c^+ \to J/ψτ^+ ν_τ)/\mathcal{B}(B_c^+ \to J/ψμ^+ ν_μ)$

A measurement of the ratio of semileptonic branching fractions $\mathcal{R}(Jψ)$, defined as $\mathcal{R}(J/ψ) \equiv \mathcal{B}(B_c^+ \to J/ψτ^+ ν_τ)/\mathcal{B}(B_c^+ \to J/ψμ^+ ν_μ)$, is reported using a sample of proton-proton collision data corresponding to an integrated luminosity of 5.4 fb$^{-1}$ recorded by the LHCb experiment in 2016--2018 at a center-of-mass energy of 13 TeV. The measured value is found to be $\mathcal{R}(J/ψ) = 0.51 \pm 0.12\text{(stat)} \pm 0.08\text{(syst)}$, which is within 1.8 standard deviations of the predictions from the Standard Model assuming lepton flavor universality.

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arXiv2026

Angular analysis of the $B^+\toπ^+μ^+μ^-$ decay

This paper presents the first measurement of the forward-backward asymmetry, $A_{\rm FB}$, and the flat term, $F_{H}$, that parameterise the angular distribution of the $B^+\toπ^+μ^+μ^-$ decay. The proton-proton collision dataset used in the analysis corresponds to an integrated luminosity of 9 fb$^{-1}$, collected with the LHCb experiment between 2011 and 2018. The analysis is performed in two intervals of dimuon mass squared, one above and one below the region containing the $J\mskip -3mu/\mskip -2muψ$ and $ψ(2S)$ narrow charmonium resonances. The Standard Model predictions lie within the obtained $68\%$ confidence level interval in the high-mass and within the $99\%$ interval in the low-mass region.

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arXiv2026

First measurement of the forward rapidity dependence of $W$ boson transverse helicity fractions

The transverse helicity fractions of $W$ bosons are measured as a function of the $W$ boson rapidity, $y_{W}$, in the range $0 \leq y_{W} \leq 5$ using $W\toμν_μ$ decays in $pp$ collisions at $\sqrt{s}$ = 13 TeV recorded by the LHCb experiment and corresponding to an integrated luminosity of $5.1$ fb$^{-1}$. The fractions are extracted from a template fit to the muon transverse momentum and pseudorapidity. The results show a strong rapidity dependence and agree with next-to-leading-order Standard Model predictions, providing the first determination of the transverse helicity fractions of $W$ bosons in the forward region.

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arXiv2026

Search for $τ^-\to μ^-μ^+μ^-$ decays at the LHCb experiment with Run 2 data

A search for the lepton-flavour-violating decay $τ^-\to μ^-μ^+μ^-$ is carried out using data collected by the LHCb experiment between 2016 and 2018 in proton-proton collisions at the LHC at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb$^{-1}$. An upper limit of $1.9\,(2.3)\times 10^{-8}$ is set at the 90% (95%) confidence level on the branching fraction of the decay.

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arXiv2026

Discovery of an unexpectedly light and narrow beauty-strange state

As the essential building blocks of visible matter, hadrons have traditionally been classified by the quark model as mesons composed of quark-antiquark pairs and baryons built from three valence quarks. Yet, this classical picture does not account for the intricate chiral dynamics of the strong force and the emergence of exotic multi-quark hadrons. While experimental evidence for such unconventional dynamics has surfaced in the charm sector, the open-beauty system remains the long-sought frontier for testing the universality of these mechanisms. Here the observation of a new resonance in the beauty-strange sector with a global significance exceeding seven standard deviations is reported using proton-proton collision data recorded by the Large Hadron Collider beauty (LHCb) experiment at the European Organization for Nuclear Research (CERN). It exhibits a narrow natural width and a substantial mass deficit compared to the conventional quark model predictions. This result marks the first observation of a nonconventional single-beauty hadron, providing crucial insights into the chiral dynamics of the strong interaction and heavy-quark spin symmetry in the exotic domain.

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arXiv2026

Measurement of the $Ω_b^-$ baryon lifetime

The lifetime ratio ${r_τ\equivτ_{Ω_b^-}/τ_{Ξ_b^-}}$ between the ${Ω_b^-}$ and ${Ξ_b^-}$ baryons is measured using a sample of $pp$ collision data corresponding to an integrated luminosity of 6 fb$^{-1}$ and collected by the LHCb experiment during LHC Run 2 (2015$-$2018). The ratio $r_τ$ is measured in two sets of decays modes, ${ {(Ω_b^-,Ξ_b^-)\to(Ω_c^0π^-,Ξ_c^0π^-)}}$ and ${(Ω_b^-,Ξ_b^-)\to(J/ψΩ^-, J/ψΞ^-)}$, with ${(Ω_c^0,Ξ_c^0)\to pK^-K^-π^+}$, ${(Ω^-,Ξ^-)\to(Λ^0 K^-,Λ^0π^-)}$, ${Λ^0\to pπ^-}$ and $J/ψ\toμ^+μ^-$. The measured $r_τ$ values are averaged and combined with Run 1 (2011$-$2012) measurements in the same decay modes to obtain ${r_τ = 1.109\pm0.055\pm0.010}$. Multiplying by the known ${Ξ_b^-}$ lifetime results in the ${Ω_b^-}$ lifetime ${τ_{Ω_b^-} = 1.751\pm0.089\pm0.022~{\rm ps}}$, where the uncertainties are statistical and systematic. This measurement improves on the precision of the $Ω_b^-$ lifetime by about a factor of two over the previous world average. The value of $r_τ$ is in agreement with the most recent theoretical predictions from the heavy quark expansion framework.

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arXiv2026

Improved branching-fraction measurements of $B^0_{(s)} \to K_S^0 h^+ h^{'-}$ decays and first observation of $B^0_{s} \to K_S^0 K^+ K^-$

This paper presents a study of the charmless three-body decays ${B^0_{(s)} \to K_{\mathrm{S}}^0 h^+ h^{\prime -}}$ (where $h^{(\prime)} = π, K$), using a sample of $pp$ collision data collected by the LHCb experiment during Runs 1 and 2 of the LHC, corresponding to an integrated luminosity of $9\,\mathrm{fb}^{-1}$. The decay ${B^0_s \to K_{\mathrm{S}}^0 K^+ K^-}$ is observed for the first time, and the following ratios of branching fractions are measured: \begin{alignat*}{6} &\frac{{\cal B}(B^0 \to K^0_{\mathrm{S}} K^+ K^-)}{{\cal B}(B^0 \to K^0_{\mathrm{S}} π^+π^-)} &&= 0.578 &&\pm 0.007 &&\pm 0.017\,, &\frac{{\cal B}(B^0 \to K^0_{\mathrm{S}} K^\pmπ^\mp)}{{\cal B}(B^0 \to K^0_{\mathrm{S}} π^+π^-)} &&= 0.1363 &&\pm 0.0035 &&\pm 0.0051\,, &\frac{{\cal B}(B^0_s \to K^0_{\mathrm{S}} π^+π^-)}{{\cal B}(B^0 \to K^0_{\mathrm{S}} π^+π^-)} &&= 0.269 &&\pm 0.011 &&\pm 0.015 && \pm 0.008\,, &\frac{{\cal B}(B^0_s \to K^0_{\mathrm{S}} K^+ K^-)}{{\cal B}(B^0 \to K^0_{\mathrm{S}} π^+π^-)} &&= 0.0303 &&\pm 0.0041 &&\pm 0.0025 && \pm 0.0009\,, &\frac{{\cal B}(B^0_s \to K^0_{\mathrm{S}} K^\pmπ^\mp)}{{\cal B}(B^0 \to K^0_{\mathrm{S}} π^+π^-)} &&= 1.818 &&\pm 0.021 &&\pm 0.031 && \pm 0.056\,, \end{alignat*} where the uncertainties are statistical, systematic, and due to knowledge of the ratio of hadronisation fractions of the $B^0_s$ and $B^0$ mesons, respectively.

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arXiv2026

Observation of the doubly charmed baryon $\varOmega^+_{cc}$

A search for the doubly charmed baryon $\varOmega^+_{cc}$ in the $\varOmega^0_cπ^+$ decay channel is performed using proton-proton collision data corresponding to an integrated luminosity of $6.3\text{fb}^{-1}$, collected with the upgraded LHCb detector in 2024 at a center-of-mass energy of 13.6$\text{TeV}$. A peaking structure with a global significance of $8.7σ$ is observed in the $\varOmega^0_cπ^+$ mass spectrum, where the $\varOmega^0_c$ baryon is reconstructed in the $pK^-K^-π^+$ final state. The structure is consistent with originating from a weakly decaying particle and is identified as the doubly charmed baryon $\varOmega^+_{cc}$. Its mass is determined to be $3725.9 \pm 1.0 \,(\mathrm{stat}) \pm 0.2 \,(\mathrm{syst}) \pm 0.4 \,(\mathrm{lifetime}) \pm 0.6 \,(\mathrm{ext})\,\text{MeV/}c^2$, where the third uncertainty arises from the dependence of the selection-induced bias on the unknown $\varOmega^+_{cc}$ lifetime, and the fourth is due to the uncertainties on the masses of the $\varOmega^0_c$, $\varXi^+_c$, and $\varXi^{++}_{cc}$ baryons.

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arXiv2026

Measurement of the $W$-boson production cross-sections in $pp$ collisions at $\sqrt{s}$ = 13 TeV in the forward region

A precision measurement of the $W$-boson production cross-section is performed using the $W \to μν$ decay channel, based on a sample of proton-proton collision data collected by the LHCb experiment at $\sqrt{s}$ = 13 TeV and corresponding to an integrated luminosity of 5.1 $fb^{-1}$. The cross-section is measured for muons with transverse momentum between 25 and 55 GeV and pseudorapidity between 2.0 and 4.5. The integrated production cross-sections of $W$ bosons are measured to be $$ \begin{array}{lcl} σ_{W^+ \to μ^+ν} &=& 1754.2 \pm 1.5 \pm 11.9 \pm 35.1\text{ pb} \\ σ_{W^- \to μ^-\barν} &=& 1178.1 \pm 1.3 \pm 9.7 \pm 23.6\text{ pb} \end{array} $$ where uncertainties are statistical, systematic, and due to the luminosity determination, respectively. Results are in good agreement with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics. This measurement is significantly more precise than previous results in this kinematic regime.

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arXiv2026

Precision measurement of the muon charge asymmetry from $W$-boson decays in $pp$ collisions at $\sqrt{s}$ = 13 TeV in the forward region

A precision measurement of the muon charge asymmetry from $W$-boson decays in proton-proton collisions at $\sqrt{s}$ = 13 TeV is presented. The analysis utilizes data corresponding to an integrated luminosity of 5.1 $fb^{-1}$, recorded by the LHCb detector during 2016, 2017 and 2018. The asymmetry is measured for muons with transverse momentum between 25 and 55 GeV and pseudorapidity between 2.0 and 4.5. This result represents the most precise determination of the muon charge asymmetry in the forward region to date, exhibiting excellent agreement with next-to-next-to-leading-order predictions in perturbative quantum chromodynamics.

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arXiv2026

Search for the decays $B_{(s)}^0\to J/ψγ$ at LHCb

A search for the rare decays $B_{(s)}^0\to J/ψγ$ is performed with proton-proton collision data collected by the LHCb experiment, corresponding to integrated luminosities of $3~\rm{fb}^{-1}$ at centre-of-mass energies of 7 and 8 TeV, and $6~\rm{fb}^{-1}$ at 13 TeV. Assuming no contribution from $B^0\to J/ψγ$ decay, an upper limit is set on the branching fraction $\mathcal{B}(B_{s}^0\to J/ψγ)<2.9\times10^{-6}$ at the 90% confidence level. If instead no contribution from $B_{s}^0\to J/ψγ$ decay is assumed, the limit is $\mathcal{B}(B^0\to J/ψγ)<2.5\times10^{-6}$ at the 90% confidence level. These results supersede the previous LHCb results, with the limit for $B_{s}^0\to J/ψγ$ improved by a factor of 2.5.

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arXiv2026

Observation of $Ξ_{b}^{0} \to Ξ^{0} J/ψ$ and evidence for $Ξ_{b}^{0} \to Ξ^{0} ψ(2S)$ decays

The first search for the beauty baryon decays $Ξ_{b}^{0} \to Ξ^{0} J/ψ$ and $Ξ_{b}^{0} \to Ξ^{0} ψ(2S)$ is presented using the proton-proton collision dataset collected by the LHCb experiment between 2016 and 2018, corresponding to an integrated luminosity of $5.4\,\mathrm{fb}^{-1}$. The first observation of the decay $Ξ_{b}^{0} \to Ξ^{0} J/ψ$ is reported and evidence of the decay $Ξ_{b}^{0} \to Ξ^{0} ψ(2S)$ is presented. The $Ξ^{0}$ hyperon is fully reconstructed for the first time at an LHC experiment, which is achieved using the $Ξ^{0} \to Λπ^{0}$ decay. The ratio of the branching fractions is measured as $\frac{\cal{B}(Ξ_{b}^{0} \to Ξ^{0} ψ(2S))}{\cal{B}(Ξ_{b}^{0} \to Ξ^{0} J/ψ)} = 0.59 \pm 0.19 \text{(stat)} \pm 0.04 \text{(syst)}$.

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arXiv2026

Branching fraction measurements of $η$ and $η^\prime(958)$ anomalous decays

Branching fractions of $η$ and $η'(958)$ anomalous decays are measured using $pp$ collision data at a center-of-mass energy of $\sqrt{s}=13\,\text{TeV}$ collected by the LHCb experiment and corresponding to an integrated luminosity of $5.4\,\text{fb}^{-1}$. The measured values and upper limits are \begin{align*} \cal{B}(η\toμ^+μ^-) &= (5.02\pm0.14\pm0.18\pm0.26)\times10^{-6} , \\ \cal{B}(η'(958)\toμ^+μ^-) &<1.9\times10^{-7}\textrm{ at 90% CL} , \\ \cal{B}(η\toπ^+π^-μ^+μ^-) &<5.4\times10^{-7}\textrm{ at 90% CL}, \\ \cal{B}(η'(958)\toπ^+π^-μ^+μ^-) &= (2.73\pm0.14\pm0.13\pm0.14)\times10^{-5} , \end{align*} where the uncertainties are, respectively, statistical, systematic, and due to the external branching fraction of the $ϕ(1020)\toμ^+μ^-$ decay, which is used for normalization. This marks the first experimental search for the $η'(958)$ decay, and the most precise measurement of the branching fraction $\cal{B}(η\toμ^+μ^-)$ to date.

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arXiv2026

Stringent limits on $C\!PT$- and Lorentz-invariance violation from $B_s^0$ meson decays

Tests of fundamental symmetries, such as $C\!PT$ and Lorentz invariance, provide sensitive probes of physics beyond the standard quantum-field-theory framework. Possible violations of these symmetries are investigated through interference effects in decays of $B_s^0$ mesons to $D_s^-π^{+}$ states. The analysis uses proton-proton collision data collected with the LHCb detector in 2015-2018 at a centre-of-mass energy of $13~\mathrm{TeV}$, corresponding to an integrated luminosity of $6~\mathrm{fb}^{-1}$. The results are interpreted within the Standard Model Extension framework, yielding sensitivities to the Lorentz-violating parameter $Δa_μ$ at the ${\cal O}(10^{-14})\,\mathrm{GeV}$ level. Without assuming Lorentz-invariance violation, the $C\!PT$-violating parameter $z$ in the $B_s^0$ system is measured to be $\mathcal{R}e(z) = 0.018 \pm 0.016 \pm 0.003$ and $\mathcal{I}m(z) = 0.003 \pm 0.004 \pm 0.002$, where the first uncertainties are statistical and the second systematic. These results represent the most precise constraints on $C\!PT$ violation in the $B_s^0$ system.

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