arXiv subjects

P. Baladron Rodriguez

Publications and source records attributed to P. Baladron Rodriguez.

At least 55 records · Page 3Linked to original sources

arXiv2026

Measurement of inclusive production of charmonium states in $b$-hadron decays via their decay into $ϕϕ$

The inclusive production of the $η_c(1S)$, $η_c(2S)$ and $χ_{c}$ charmonium states in $b$-hadron decays is studied with LHCb Run~2 data, corresponding to an integrated luminosity of $5.9~\text{fb}^{-1}$, using charmonia decays to $ϕϕ$ pairs. The production branching fractions of the $χ_{c}(1P)$ states in $b$-hadron decays are measured, using $b \to η_c(1S) (\to ϕϕ) X$ as a normalisation channel, with $X$ indicating any additional particles. The results are \begin{align*} &{\cal{B}} (b \to χ_{c0} X) = (1.34 \pm 0.13 \pm 0.06 \pm 0.37) \times 10^{-3}, &{\cal{B}} (b \to χ_{c1} X) = (1.58 \pm 0.12 \pm 0.09 \pm 0.44) \times 10^{-3}, &{\cal{B}} (b \to χ_{c2} X) = (0.55 \pm 0.08 \pm 0.05 \pm 0.15) \times 10^{-3}, \end{align*} where the first uncertainty is statistical, the second systematic and the last is due to the limited knowledge of externally measured branching fractions. The production branching fraction of $η_c(2S)$ times the branching fraction of its decay into $ϕϕ$ is measured as ${\cal{B}} (b \to η_c(2S) X) \times {\cal{B}} (η_c(2S) \to ϕϕ) = (4.0 \pm 0.6 \pm 0.6 \pm 1.1) \times 10^{-7}$. Furthermore, the mass of the $η_c(1S)$ state is measured to be $M_{η_c(1S)} = 2984.1 \pm 0.5 \pm 0.5$ MeV with the best precision to date.

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arXiv2026

First observation of $CP$ violation and measurement of polarization in $B^+\toρ(770)^0 K^*(892)^+$ decays

An amplitude analysis of the $B^+\to(π^+π^-)(K^0_{\mathrm{S}}π^+)$ decay is performed in the mass regions $0.30 < m_{π^+π^-} < 1.10\,\mathrm{GeV}/c^2$ and $0.75 < m_{K^0_{\mathrm{S}}π^+} < 1.20\,\mathrm{GeV}/c^2$, using $pp$ collision data recorded with the LHCb detector corresponding to an integrated luminosity of $9\,\mathrm{fb}^{-1}$. The polarization fractions and $CP$ asymmetries for $B^+\toρ(770)^0K^*(892)^+$ decays are measured. Violation of the $CP$ symmetry in the decay $B^+\toρ(770)^0K^*(892)^+$ is observed for the first time, with a significance exceeding nine standard deviations. The $CP$ asymmetry is measured to be ${\cal A}_{CP} = 0.507 \pm 0.062\ \text{(stat)} \pm 0.024\ \text{(syst)}$ and the $CP$-averaged longitudinal polarization fraction of $f_L = 0.720 \pm 0.028\ \text{(stat)} \pm 0.009\ \text{(syst)}$. The measurements help to shed light on the polarization puzzle of $B$ mesons decaying to two vector mesons.

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arXiv2026

Observation and investigation of the $T_{c\bar{c}1}(4430)^{+}$ structure in $B^{+} \to ψ(2S) K_{\text{S}}^{0} π^{+}$ decays

The first four-dimensional amplitude analysis of the $B^{+} \to ψ(2S) K_{\text{S}}^{0} π^{+}$ decay is performed with proton-proton collision data collected by the LHCb experiment at $\sqrt{s} = 13~\rm{TeV}$, corresponding to an integrated luminosity of $5.4~\rm{fb^{-1}}$. The data cannot be fully explained by $B^{+} \to ψ(2S) K^{*+}$ contributions alone. A significantly better description of the data is obtained by adding a $T_{c\bar{c}}^{+}$ contribution decaying to $ψ(2S)π^{+}$. The properties of the $T_{c\bar{c}}^{+}$ structure are consistent with the exotic state $T_{c\bar{c}1}(4430)^{+}$ reported in the isospin-related $\bar{B}^{0} \to ψ(2S) K^{-} π^{+}$ decay. Effects of a possible $T_{c\bar{c}1}(4430)^{+} \to \bar{D}_{1}^{*}(2600)^{0} D^{+}$ decay mode on the $T_{c\bar{c}1}(4430)^{+} \to ψ(2S)π^{+}$ mass distribution are investigated through a Flatté parametrization, providing constraints on the relative decay strength. A description of the $T_{c\bar{c}1}(4430)^{+}$ structure using the triangle singularity mechanism is studied and also found to be consistent with the data.

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arXiv2026

Measurement of the $W \to μν_μ$ cross-sections as a function of the muon transverse momentum in $pp$ collisions at 5.02 TeV

The $pp \to W^{\pm} (\to μ^{\pm} ν_μ) X$ cross-sections are measured at a proton-proton centre-of-mass energy $\sqrt{s} = 5.02$ TeV using a dataset corresponding to an integrated luminosity of 100 pb$^{-1}$ recorded by the LHCb experiment. Considering muons in the pseudorapidity range $2.2 < η< 4.4$, the cross-sections are measured differentially in twelve intervals of muon transverse momentum between $28 < p_\mathrm{T} < 52$ GeV. Integrated over $p_\mathrm{T}$, the measured cross-sections are \begin{align*} σ_{W^+ \to μ^+ ν_μ} &= 300.9 \pm 2.4 \pm 3.8 \pm 6.0~\text{pb}, \\ σ_{W^- \to μ^- \barν_μ} &= 236.9 \pm 2.1 \pm 2.7 \pm 4.7~\text{pb}, \end{align*} where the first uncertainties are statistical, the second are systematic, and the third are associated with the luminosity calibration. These integrated results are consistent with theoretical predictions. This analysis introduces a new method to determine the $W$-boson mass using the measured differential cross-sections corrected for detector effects. The measurement is performed on this statistically limited dataset as a proof of principle and yields \begin{align*} m_W = 80369 \pm 130 \pm 33~\text{MeV}, \end{align*} where the first uncertainty is experimental and the second is theoretical.

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arXiv2026

Measurement of CP asymmetries in $\kern 0.18em\overline{\kern -0.18em B}^0 \to D_s^- D^+$ and $\kern 0.18em\overline{\kern -0.18em B}_s^0 \to D_s^+ D^-$ decays

Measurements of the combined CP asymmetries in $\kern 0.18em\overline{\kern -0.18em B}^0 \to D_s^- D^+$ and $\kern 0.18em\overline{\kern -0.18em B}_s^0 \to D_s^+ D^-$ decays are made using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9fb$^{-1}$. The measurements are found to be \begin{aligned} A_{CP}(\kern 0.18em\overline{\kern -0.18em B}^0 \to D_s^- D^+) &= 0.0009 \pm 0.0053 \pm 0.0040, \\ A_{CP}(\kern 0.18em\overline{\kern -0.18em B}_s^0 \to D_s^+ D^-) &= 0.103\phantom{0} \pm 0.053\phantom{0} \pm 0.010, \end{aligned} where the first and second uncertainties are statistical and systematic, respectively. This is the first measurement of this asymmetry in $\kern 0.18em\overline{\kern -0.18em B}_s^0$ decays, and the most precise measurement to date for $\kern 0.18em\overline{\kern -0.18em B}^0$ decays. Both measurements are found to be consistent with CP symmetry.

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arXiv2026

Search for heavy neutral leptons in B-meson decays

A search for long-lived heavy neutral leptons produced in B-meson decays and decaying to a $ μ^\pm π^\mp$ final state is performed with data collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $5\,\mathrm{fb}^{-1}$. The results are interpreted in both lepton-number-conserving and lepton-number-violating scenarios. No significant excess is observed. Constraints are placed on the squared mixing element $|U_{μN}|^2$ to the active muon neutrino, under the assumption that couplings to other lepton flavours are negligible, in the mass range of $1.6$-$5.5$ GeV.

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arXiv2026

Measurement of the branching fraction of the $Λ_b^0\to J/ψΛ$ decay and isospin asymmetry of $B\to J/ψK$ decays

This paper describes a measurement of the $Λ_b^0\to J/ψΛ$ branching fraction using data collected with the LHCb experiment in proton-proton collisions from 2016 to 2018. The dataset corresponds to an integrated luminosity of 5.4$\,\text{fb}^{-1}$. The branching fraction is determined relative to that of $B^0\to J/ψK^0_\text{S}$ decays, $\frac{\mathcal{B}(Λ_b^0\to J/ψΛ)}{\mathcal{B}(B^0\to J/ψK^0_\text{S}} = 0.750 \pm 0.005 \pm 0.022 \pm 0.005 \pm 0.062\,,$ yielding $\mathcal{B}(Λ_b^0\to J/ψΛ) = (3.34 \pm 0.02 \pm 0.10 \pm 0.08 \pm 0.28)\times 10^{-4}$, where the first uncertainty is statistical, the second systematic, the third due to external inputs on branching fractions and the fourth due to the ratio of $Λ_b^0$ baryon and $B^0$ meson hadronisation fractions. In addition, the isospin asymmetry between the rates of $B^0\to J/ψK^0_\text{S}$ and $B^+\to J/ψK^+$ decays is measured to be $A_{\rm I} = -0.0135 \pm 0.0004 \pm 0.0133$, where the first uncertainty is statistical and the second systematic.

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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

A model-independent measurement of the CKM angle $γ$ in the decays $B^\pm\to[K^+K^-π^+π^-]_D h^\pm$ and $B^\pm\to[π^+π^-π^+π^-]_D h^\pm$ ($h = K, π$)

A model-independent determination of the CKM angle $γ$ is presented, using the $B^\pm\to[K^+K^-π^+π^-]_D h^\pm$ and $B^\pm\to[π^+π^-π^+π^-]_D h^\pm$ decays, with $h=K,π$. This measurement is the first phase-space-binned study of these decay modes, and uses a sample of proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of $9$fb$^{-1}$. The phase-space bins are optimised for sensitivity to $γ$, and in each bin external inputs from the BESIII experiment are used to constrain the charm strong-phase parameters. The result of this binned analysis is $γ= (53.9_{-8.9}^{+9.5})^\circ$, where the uncertainty includes both statistical and systematic contributions. Furthermore, when combining with existing phase-space-integrated measurements of the same decay modes, a value of $γ= (52.6_{-6.4}^{+8.5})^\circ$ is obtained, which is one of the most precise determinations of $γ$ to date.

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arXiv2026

Measurement of $C\!P$ asymmetry in $D^0 \to K^0_{\rm S} K^0_{\rm S}$ decays with Run 3 data

A measurement of $C\!P$ asymmetry in $D^0 \to K^0_{\rm S} K^0_{\rm S}$ decays is reported, based on a data sample of proton-proton collisions collected with the LHCb detector in 2024 at a centre-of-mass energy of $13.6\,$TeV, corresponding to an integrated luminosity of $6.2\,\mathrm{fb}^{-1}$. The $D^0 \to K^0_{\rm S} π^+ π^-$ decay is used as calibration channel to cancel residual detection and production asymmetries. The time-integrated $C\!P$ asymmetry for the $D^0 \to K^0_{\rm S} K^0_{\rm S}$ mode is measured to be $$ {\cal A}^{C\!P} (D^0 \to K^0_{\rm S} K^0_{\rm S}) = (1.86 \pm 1.04\pm 0.41)\%, $$ where the first uncertainty is statistical, and the second is systematic. This measurement represents the most precise single-experiment determination of this quantity to date.

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arXiv2026

First evidence of $CP$ violation in beauty baryon to charmonium decays

A study of the difference in the $CP$ asymmetries between $Λ^0_b \rightarrow J / ψp π^-$ and $Λ^0_b \rightarrow J / ψp K^-$ decays, $Δ{\cal A}_{CP}$, is performed using proton-proton collision data collected by the LHCb experiment in the years 2015--2018, corresponding to an integrated luminosity of $6 \,{\rm fb}^{-1}$. This quantity is measured to be $ Δ{\cal A}_{CP}=(4.03\pm 1.18\pm 0.23)\%$, where the first uncertainty is statistical and the second is systematic. When combined with the previous LHCb result, a value of $Δ{\cal A}_{CP} = (4.31 \pm 1.06 \pm 0.28)\%$ is obtained, corresponding to a significance of $3.9σ$ against the $CP$ symmetry hypothesis. Studies of triple-product asymmetries, which provide an additional probe of $CP$ violation, show no significant deviation from $CP$ symmetry.

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arXiv2026

Measurement of $ψ(2S)$ to $J/ψ$ cross-section ratio as function of multiplicity in $p$Pb collisions at$\sqrt{s_{NN}} = 8.16$ TeV

The production ratio of $ψ(2S)$ to $J/ψ$ charmonium states is presented as a function of multiplicity in proton-lead collisions at a centre-of-mass energy of $\sqrt{s_{NN}}=8.16$ TeV, for both prompt and nonprompt sources. The total luminosity recorded by the LHCb experiment corresponds to 13.6 $pb^{-1}$ for $p$Pb collisions and 20.8 $pb^{-1}$ for Pb$p$ collisions, where the first particle indicates the forward direction of the detector. Measurements are performed in the dimuon final state at forward (backward) centre-of-mass rapidity $1.5<y^*<4.0$ ($-5.0<y^*<-2.5$) for $p$Pb (Pb$p$) collisions.A multiplicity dependence of the prompt production ratio is observed in $p$Pb collisions, whereas no dependence is found in nonprompt production, nor in either prompt or nonprompt production in Pb$p$ collisions. These results suggest that in the Pb-going direction additional suppression mechanisms beyond comover effects may be present, possibly related to the formation of quark-gluon plasma. This highlights a transition from small to large collision systems and provides important insight into the suppression of charmonia in proton-nucleus collisions.

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arXiv2026

Observation of $B_c^+ \to D h^+ h^-$ decays

Searches are presented for $B_{c}^{+} \to D h^+ h^-$ decays, where $D$ is a charmed meson and $h^{\pm}$ is a charged pion or kaon, using $pp$ collision data collected by the LHCb experiment corresponding to an integrated luminosity of $9~\text{fb}^{-1}$. The decays $B_c^+\to D^+ K^+π^-$, $B_c^+\to D^{*+} K^+π^-$ and $B_c^+\to D_s^+ K^+ K^-$ are observed for the first time. Their branching fractions, expressed as ratios relative to that of the $B_c^+\to B_s^0π^+$ decay, are determined to be \begin{align*} \mathcal{R}(B_c^+\to D^+ K^+π^-) =(1.96 \pm 0.23\pm 0.08 \pm 0.10)\times 10^{-3},&\\ \mathcal{R}(B_c^+\to D^{*+} K^+π^-) =(3.67 \pm 0.55 \pm 0.24\pm 0.20)\times 10^{-3},&\\ \mathcal{R}(B_c^+\to D_s^+ K^+ K^-) =(1.61 \pm 0.35\pm 0.13\pm 0.07)\times 10^{-3}, \end{align*} where the first uncertainty is statistical, the second is systematic, and the third is due to the limited precision on the $D$-meson branching fractions. The decay channels proceed primarily through excited $K^0$ or $D^0$ resonances or $ϕ$ mesons, and open a new avenue for studies of charge-parity violation in beauty mesons.

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arXiv2026

A method for luminosity determination based on real-time hit reconstruction with the LHCb silicon pixel detector

The data acquisition system of the upgraded LHCb experiment includes the fast reconstruction of all hits in the vertex locator (VELO) pixel detector at the beam-crossing rate of 40 MHz, implemented as on-the-fly clustering embedded in the firmware of the readout board FPGAs. The availability of a high rate of reconstructed clusters in real time enables a new fast approach for measuring luminosity and monitoring the LHCb luminous region, directly at the detector readout level. This methodology has been implemented as an array of real-time cluster counters in the VELO readout FPGAs and has been in operation since the start of the 2024 physics run of LHCb. This paper describes the methodology and its features and performance, both on proton-proton and lead-lead collision data. The method shows a statistical resolution better than the percent level, and a sensitivity to variable running conditions of the same level. This is achieved with an intrinsic time granularity better than 100 ms , undersampled to 3 s for analysis purposes. Nonlinear behaviour is compatible with zero in a luminosity range including the LHCb Run 3 operating point.

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arXiv2026

First observation of the $\overline{B}_{s}^{0}\toΛ_{c}^{+}\overlineΛ_{c}{}^{-}$ decay and evidence for the $\overline{B}^{0}\toΛ_{c}^{+}\overlineΛ_{c}{}^{-}$ decay

A search is presented for the two-body charmed baryonic decays $\overline{B}_{(s)}^{0}\toΛ_{c}^{+}\overlineΛ_{c}{}^{-}$, using a data sample collected by the LHCb experiment during 2011--2012 and 2015--2018 corresponding to an integrated luminosity of $9\,\mathrm{fb}^{-1}$. The first observation of the $\overline{B}_{s}^{0}\toΛ_{c}^{+}\overlineΛ_{c}{}^{-}$ decay is reported with $6.2σ$ significance, along with $4.3σ$ evidence for the $\overline{B}^{0}\toΛ_{c}^{+}\overlineΛ_{c}{}^{-}$ decay. The branching fractions are measured to be $\mathcal{B}{}(\overline{B}^{0}\toΛ_{c}^{+}\overlineΛ_{c}{}^{-}) = (1.01^{+0.27}_{-0.28} \pm 0.08 \pm 0.15) \times 10^{-5}$ and $\mathcal{B}{}(\overline{B}_{s}^{0}\toΛ_{c}^{+}\overlineΛ_{c}{}^{-}) = (5.0 \pm 1.3 \pm 0.5 \pm 0.8) \times 10^{-5}$, where the first uncertainty is statistical, the second systematic, and the third due to external inputs. These results provide novel experimental inputs for the theoretical framework describing two-body baryonic decays of $B$ mesons via $W$-emission and $W$-exchange mechanisms.

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arXiv2026

Observation of the rare baryonic decay $B^{+}\rightarrow p \bar{\itΛ}$ and measurement of its weak decay parameter

The first observation of the decay $B^{+}\rightarrow p \bar{\itΛ}$ is presented, using proton-proton collision data collected by the LHCb experiment between 2016 and 2018 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $5.4\,\mathrm{fb}^{-1}$. The signal significance exceeds seven standard deviations. Using the $B^{+} \rightarrow K^{\mathrm{0}}_{\mathrm{S}} π^{+}$ decay as a normalization channel, the branching fraction is measured and combined with previous LHCb results based on data collected at 7 and 8 TeV in 2011 and 2012, yielding $\mathcal{B}(B^{+}\rightarrow p \bar{\itΛ})=(1.24\pm 0.17\pm 0.05\pm 0.03)\times 10^{-7}$, where the first uncertainty is statistical, the second is systematic, and the third comes from the uncertainty on the branching fraction of the normalization channel. The $B^{+}\rightarrow p \bar{\itΛ}$ weak decay parameter is measured to be $α_B = 0.87_{-0.29}^{+0.26} \pm 0.09$, indicating the presence of comparable S-wave and P-wave decay amplitudes.

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arXiv2026

Study of charm mixing and CP violation with $D^0\to K^\pmπ^\mpπ^\pmπ^\mp$ decays

A study of charm mixing and CP violation in $D^0\to K^\pmπ^\mpπ^\pmπ^\mp$ decays is performed using data collected by the LHCb experiment in proton-proton collisions from 2015 to 2018, corresponding to an integrated luminosity of 6$\text{fb}^{-1}$. The ratio of promptly produced $D^0\to K^+π^- π^+π^-$ to $D^0\to K^-π^+ π^-π^+$ decay rates is measured as a function of $D^0$ decay time, both inclusive over phase space and in bins of phase space. Taking external inputs for the $D^0 -\overline{D}^0$ mixing parameters $x$ and $y$ allows constraints to be obtained on the hadronic parameters of the charm decay. When combined with previous measurements from charm-threshold experiments and at LHCb, improved knowledge is obtained for these parameters, which is valuable for studies of the angle $γ$ of the Unitarity Triangle. An alternative analysis is also performed, in which external inputs are taken for the hadronic parameters, and the mixing parameters are determined, including $Δx$ and $Δy$, which are nonzero in the presence of CP violation. It is found that $x=\left(0.85^{+0.15}_{-0.24}\right)\%$, $y=\left( 0.21^{+0.29}{-0.27} \right)\%$, $Δx=\left( -0.02\pm {0.04} \right)\% $ and $Δy=\left( 0.02^{+0.04}_{-0.03} \right)\%$. These results are consistent with previous measurements and the hypothesis of CP conservation.

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arXiv2026

Measurement of transverse $Λ$ and $\barΛ$ hyperon polarization in $p$Pb collisions at $\sqrt{s_{NN}} = 5.02$ TeV

The transverse polarization of $Λ$ and $\barΛ$ hyperons is measured in $p$Pb collisions collected by the LHCb experiment at a nucleon-nucleon center-of-mass energy of $5.02$ TeV. The polarization is averaged over hyperon transverse momentum in the ranges $0.15 < p_{T} < 6.00 $ GeV/$c$, and Feynman-$x$ in the ranges $0.005 < x_{F} < 0.040$ (forward region) and $-0.10 < x_{F} < -0.01$ (backward region) defined relative to the proton beam direction. The transverse polarization is found to be compatible with zero for both $Λ$ and $\barΛ$ hyperons. The results are also measured as a function of $p_{T}$ and $x_{F}$ with no significant dependence on these variables observed. The results are compared with previous experimental measurements at different center-of-mass energies and collision environments.

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