arXiv subjects

T. Blake

Publications and source records attributed to T. Blake.

At least 55 records · Page 3Linked to original sources

arXiv2026

Search for $C\!P$ violation in $D^+ \to ϕπ^+$ decays

A search for charge-parity ($C\!P$) violation in the Cabibbo-suppressed $D^+ \to ϕπ^+$ decay is presented, using proton-proton collision data corresponding to an integrated luminosity of $6\text{ fb}^{-1}$, collected at a centre-of-mass energy of $13\text{ TeV}$ with the LHCb detector during Run 2. An abundant sample of $D^+ \to K_{\rm S}^0 π^+$ decays is employed to correct for asymmetries arising from the production of the charmed meson and from detection effects associated with the charged pion accompanying the $ϕ$ meson. Asymmetries induced by interference of multiple processes, such as neutral kaon mixing, regeneration of neutral kaons, and interference between the Cabibbo-favoured $D^+ \to \overline{K}^0 π^+$ and the doubly Cabibbo-suppressed $D^+ \to {K}^0 π^+$ decay, are subtracted. The direct $C\!P$ asymmetry in the $D^+ \to ϕπ^+$ decay is measured to be \begin{equation*} a_{C\!P}(D^+ \to ϕπ^+) = \left(0.1 \pm 4.9\text{ (stat)} \pm 2.4\text{ (syst)} \right)\times 10^{-4}. \end{equation*} For the first time at a hadron collider, the modulus of the ratio and the relative strong phase of the $D^+ \to {K}^0 π^+$ to $D^+ \to \overline{ K}^0 π^+$ decay amplitudes are also investigated. Two-dimensional confidence intervals are reported for these parameters.

hep-ex↗

arXiv2026

Search for the decays $B^+_{(c)} \to μ^+ ν_μγ$

A search for the radiative leptonic decays $B^+\toμ^+ν_μγ$ and $B^+_c\toμ^+ν_μγ$ is performed using proton-proton collision data collected with the LHCb experiment at a center-of-mass energy of $13~{\rm TeV}$, corresponding to an integrated luminosity of $5.4~{\rm fb}^{-1}$. No evidence for an excess of events over background is observed for either signal decay. Upper limits at 90% confidence level are set on the branching fractions: \begin{align} {\cal{B}}(B^+\toμ^+ν_μγ)_{E_γ^\ast > 1\,\rm{GeV}} &< 4.0 \times 10^{-6},\\ {\cal{B}}(B_c^+\toμ^+ν_μγ)_{E_γ^\ast > 1\,\rm{GeV}} &< 1.6 \times 10^{-3}, \end{align} where the photon energy in the $B$-meson rest frame, $E_γ^\ast$, is required to be greater than $1~{\rm GeV}$. This constitutes the first search for these decays at a hadron collider and the first experimental investigation of the $B_c^+\toμ^+ν_μγ$ decay to date.

hep-ex↗

arXiv2026

Study of the $B^0 \to Λ_c^+ \barΛ_c^- K_S^0$ decay

The decay $B^0 \to Λ_c^+ \barΛ_c^- K_S^0$ is studied at LHCb for the first time using proton-proton collision data recorded by the LHCb experiment at a center-of-mass energy of $\sqrt{s} = 13$ TeV, corresponding to an integrated luminosity of 5.4 fb$^{-1}$. The branching ratio relative to the decay $B^+ \to Λ_c^+ \barΛ_c^- K^+$ is measured to be $$ \frac{{\cal B}(B^0 \to Λ_c^+ \barΛ_c^- K_S^0)}{{\cal B}(B^+ \to Λ_c^+ \barΛ_c^- K^+)} = 0.53 \pm 0.05 \pm 0.05, $$ where the first uncertainty is statistical and the second is systematic. Evidence is found for contributions from two resonant states, $Ξ_c(2923)^+$ and $Ξ_c(2939)^+$, in the $Λ_c^+ K_S^0$ system. The two states show a significance of $3.9σ$ relative to the nonresonant hypothesis. These two $Ξ_c^+$ states are consistent with being the isospin partners of the states observed in $Λ_c^+ K^-$ system.

hep-ex↗

arXiv2026

Observation of new excited $\itΣ_{c}^{0}$ states in the $B^-\rightarrow \itΛ^+_c\overline{p}π^{-}$ decay

An amplitude analysis of the $B^-\rightarrow \itΛ^+_c\overline{p}π^{-}$ decay is performed using proton-proton collision data, corresponding to an integrated luminosity of $9\text{ fb}^{-1}$, collected with the \mbox{LHCb} detector at center-of-mass energies of 7, 8, and 13$\text{ TeV}$. In the $\itΛ^+_cπ^{-}$ invariant-mass spectrum, the known $\itΣ_c(2455)^0$, $\itΣ_c(2520)^0$, $\itΣ_c(2800)^0$ baryons are observed, along with two new states: $\itΣ_c(2900)^0$ and $\itΣ_c(3200)^0$. The masses and widths of the three high-mass states, modeled with Breit--Wigner line shapes, are determined. This result expands the landscape of charm baryon spectroscopy and provides crucial data for understanding charm baryon structure and dynamics.

hep-ex↗

arXiv2026

Comprehensive analysis of the $B^0\to K^{*0}μ^+μ^-$ decay

An analysis of the $B^{0}\rightarrow K^{*0}(\to K^+ π^-)μ^{+}μ^{-}$ decay is presented using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 8.4 fb$^{-1}$. The full set of $CP$-averaged and $CP$-asymmetric angular observables is determined in bins of the invariant mass squared of the dimuon system, as well as the branching fraction relative to the $B^{0}\rightarrow J/ψ(\toμ^{+}μ^{-})K^+π^-$ decay. For the first time, the full set of observables pertaining to the $K^+π^-$ S-wave contribution to the final state are presented and consideration is given to effects arising from the mass of the muons. The measurements of the $CP$-averaged observables and the branching fractions continue to exhibit the pattern of tensions with the Standard Model predictions that have been seen in previous analyses that use part of the dataset considered in this Letter.

hep-ex↗

arXiv2026

Observation of the doubly charmed baryon $\itΞ_{cc}^+$ with the LHCb Run 3 detector

The first observation of the doubly charmed baryon $\itΞ_{cc}^+$ is reported through its decay to the $\itΛ_c^+ K^-π^+$ final state, with a statistical significance exceeding seven standard deviations. The observation is made using proton-proton collision data collected in 2024 with the LHCb Run 3 detector at a center-of-mass energy of 13.6 TeV, corresponding to a total integrated luminosity of $6.9\,\mathrm{fb}^{-1}$. The $\itΞ_{cc}^+$ mass is measured to be $3619.97 \pm 0.83 \pm 0.26 \,^{+1.90}_{-1.30}\,\mathrm{MeV}/c^2$, where the first uncertainty is statistical, the second is systematic, and the third is due to the unknown $\itΞ_{cc}^+$ lifetime, which is assumed to lie in the range 15-160 fs with a baseline value of 45 fs. The difference between the masses of the $\itΞ_{cc}^+$ and $\itΞ_{cc}^{++}$ baryons is determined to be $-1.77 \pm 0.84 \pm 0.15 \,^{+1.90}_{-1.30}\,\mathrm{MeV}/c^2$. This is the first observation of a new particle made with the LHCb Run 3 detector.

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arXiv2026

First measurement of time-dependent $CP$ violation in the flavor-changing neutral-current decay $B^{0}\rightarrow K_{S}^{0}μ^{+}μ^{-}$

A flavor-tagged time-dependent analysis of $B^{0}\rightarrow K_{S}^{0}μ^{+}μ^{-}$ decays is performed across the full dimuon mass range excluding the $J/ψ$ and $ψ(2S)$ resonance regions. The analysis uses proton-proton collision data collected by the LHCb experiment in 2011--2018 at center-of-mass energies of 7, 8 and 13TeV, corresponding to an integrated luminosity of 9$fb^{-1}$. The CP violation parameters are determined to be $C=-0.13 \pm 0.32 \pm 0.04$ and $S= +0.82\pm 0.29 \pm 0.05$, where the first uncertainties are statistical and the second are systematic. The results are consistent with the Standard Model prediction. This is the first experimental study of time-dependent CP violation in $b\rightarrow sl^{+}l^{-}$ processes.

hep-ex↗

arXiv2026

Differential measurement of the branching fraction and $C\!P$ asymmetry of the decay $B^\pm\to π^\pmμ^+μ^-$

Differential measurements of the branching fraction and $C\!P$ asymmetry of the decay $B^\pm\to π^\pmμ^+μ^-$ are performed in intervals of the dimuon mass squared, $q^2$, using proton-proton collision data corresponding to an integrated luminosity of 9 fb$^{-1}$ recorded by the LHCb experiment at centre-of-mass energies of 7 TeV, 8 TeV and 13 TeV. The ratios of the branching fractions of $B^\pm\to π^\pmμ^+μ^-$ and $B^\pm\to K^\pmμ^+μ^-$ decays are also reported in the same $q^2$ intervals. The measured branching fractions are compatible with the predictions of the Standard Model, with consistency varying between 1.4$σ$ and 3.8$σ$ depending on the model assumptions.

hep-ex↗

arXiv2026

Probing the nature of the $χ_{c1}(3872)$ state using radiative decays

The radiative decays $χ_{c1}(3872)\rightarrowψ(2S)γ$ and $χ_{c1}(3872)\rightarrow J/ψγ$ are used to probe the~nature of the~$χ_{c1}(3872)$ state using proton-proton collision data collected with the LHCb detector, corresponding to an~integrated luminosity of~9fb$^{-1}$. Using the~$B^+\rightarrow χ_{c1}(3872)K^+$decay, the $χ_{c1}(3872)\rightarrow ψ(2S)γ$ process is observed for the first time and the ratio of its partial width to that of the $χ_{c1}(3872)\rightarrow J/ψγ$ decay is measured to be $$ \frac{Γ_{χ_{c1}(3872)\rightarrow ψ(2S)γ}} {Γ_{χ_{c1}(3872)\rightarrow J/ψγ}} = 1.67 \pm 0.21 \pm 0.12 \pm0.04 , $$ where the first uncertainty is statistical, the second systematic and the third is due to the uncertainties on the branching fractions of the $ψ(2S)$ and $J/ψ$ mesons. The measured ratio makes the interpretation of the $χ_{c1}(3872)$ state as a~pure $D^0\bar{D}^{*0}+\bar{D}^0D^{*0}$ molecule questionable and strongly indicates a sizeable compact charmonium or tetraquark component within the $χ_{c1}(3872)$ state.

hep-ex↗

arXiv2026

Study of nuclear effects on charm production in light-ion collisions

The onset of nuclear effects in light-ion collisions is studied by measuring the ratio of $D^0$ meson production between NeNe and OO collisions at a center-of-mass energy per nucleon pair of $5.36\,{\rm TeV}$ recorded by the LHCb detector. The $D^0$ meson yields are measured differentially in transverse momentum ($p_{\rm T}$) for $0.5<p_{\rm T}<20\,{\rm GeV}$ in the rapidity ($y$) region $2.0<y<4.5$, and are normalized to the total number of recorded inelastic nucleus-nucleus collisions in each data sample. The resulting production ratio shows evidence of variation as a function of $p_{\rm T}$, which is inconsistent with predictions based on nuclear modification of nucleon structure alone. This measurement is consistent with the onset of quark-gluon plasma production with increasing nucleus size in high-energy nuclear collisions.

nucl-ex↗

arXiv2026

Measurement of the branching fractions and longitudinal polarisations of $B^0_{(s)} \to K^{0} \kern 0.18em \overline{\kern -0.18em K}{}^{0}$ decays

A time- and flavour-integrated amplitude analysis of $B^0$ and $B^0_s$ decays to the $(K^+π^-)(K^-π^+)$ final state in the $K^*(892)^0 \kern 0.18em \overline{\kern -0.18em K}{}^{*}(892)^0$ region is presented, using $pp$ collision data recorded with the LHCb detector in 2011--2018, corresponding to an integrated luminosity of $9\,\text{fb}^{-1}$. The branching fractions of the $B^0$ and $B^0_s$ decays are measured relative to the $B^0 \to D^-π^+$ and $B^0_s \to D^-_s π^+$ modes, respectively. The corresponding longitudinal polarisation fractions are found to be $f_L^{d} = 0.600 \pm 0.022 \pm 0.017$ and $f_L^{s} = 0.159 \pm 0.010 \pm 0.007$, where the uncertainties are statistical and systematic, respectively. The theory-motivated ratio of the squared $B^0_s$ to $B^0$ longitudinally polarised decay amplitudes is found to be $L_{K^{*0} \kern 0.18em \overline{\kern -0.18em K}{}^{*0}} = 4.92 \pm 0.55 \pm 0.48 \pm 0.02 \pm 0.10$, where the uncertainties are statistical, systematic, due to uncertainty of external mass and lifetime measurements, and due to knowledge of the fragmentation fraction ratio, respectively. This confirms the previously reported tension between experimental determinations and theoretical predictions of longitudinal polarisation in $B \to VV$ decays at the level of 4.4 standard deviations.

hep-ex↗

arXiv2026

Search for $K_{\mathrm{S(L)}}^{0} \rightarrow π^{+}π^{-}μ^{+}μ^{-}$ decays at LHCb

A search for $K_{\mathrm{S(L)}}^{0} \rightarrow π^{+}π^{-}μ^{+}μ^{-}$ decays is performed using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of $13\,\mathrm{TeV}$, corresponding to an integrated luminosity of $5.4\,\mathrm{fb^{-1}}$. No $K_{\mathrm{S(L)}}^{0} \rightarrow π^{+}π^{-}μ^{+}μ^{-}$ signals are found and upper limits are set for the first time on the branching fractions $\mathcal{B}(K_\text{S}^{0} \rightarrow π^{+}π^{-}μ^{+}μ^{-}) < 1.4 \times 10^{-9}$ and $\mathcal{B}(K_\text{L}^{0} \rightarrow π^{+}π^{-}μ^{+}μ^{-}) < 6.6 \times 10^{-7}$, at the 90% confidence level.

hep-ex↗

arXiv2026

First evidence of the decay $B^+\toπ^+ e^+ e^-$

The first evidence for the decay $B^+\toπ^+ e^+ e^-$ is reported using proton-proton collision data recorded by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb$^{-1}$. A signal excess with a significance of 3.2$σ$ is observed and the branching fraction is measured to be $\cal{BR}(B^+\toπ^+ e^+ e^-) = (2.4\,{}^{+0.9}_{-0.8} \,{}^{+0.4}_{-0.2}) \times 10^{-8}$, where the first set of uncertainties is statistical and the second is systematic. The result is consistent with the Standard Model expectation.

hep-ex↗

arXiv2026

Observation of a new excited charm-strange meson $D_{s1}(2933)^+$ in $B^0\to D^+ D^- K^+ π^-$ decays

A new excited charm-strange meson is observed through an amplitude analysis of the full phase space of $B^0\to D^+ D^- K^+ π^-$ decays. The analysis is based on a proton-proton collision data sample collected by the \lhcb experiment at a center-of-mass energy $\sqrt{s} = 13\,\text{TeV}$, corresponding to an integrated luminosity of $5.4\text{fb}^{-1}$. The statistical significance of the new state exceeds $10$ standard deviations. Its Breit--Wigner mass and width are measured to be $m_0 = {2933}^{+6}_{-5}(\text{stat})^{+4}_{-3}(\text{syst}) \,\text{MeV} $ and $Γ_0 = {72}^{+18}_{-12}(\text{stat})^{+\phantom{0}7}_{-10}(\text{syst}) \,\text{MeV} $, respectively, and its spin-parity quantum numbers are determined to be $J^P = 1^+$. This new meson, denoted as $D_{s1}(2933)^+$, is a candidate for a $D_s(2P^{(\prime)}_{1})^+$ state.

hep-ex↗

arXiv2026

Measurement of charged-hadron distributions in heavy-flavor jets in proton-proton collisions at $\sqrt{s}$=13 TeV

Charged-hadron distributions in heavy-flavor jets are measured in proton-proton collisions at a center-of-mass energy of $\sqrt{s}$ = 13 TeV collected by the LHCb experiment. Distributions of the longitudinal momentum fraction, transverse momentum, and radial profile of charged hadrons are measured separately in beauty and charm jets. The distributions are compared to those previously measured by the LHCb collaboration in jets produced back-to-back with a $Z$ boson, which in the forward region are primarily light-quark-initiated, to compare the hadronization mechanisms of heavy and light quarks. The observed differences between the heavy- and light-jet distributions are consistent with the heavy-quark dynamics expected to arise from the dead-cone effect, as well as with a hard fragmentation of the heavy-flavor hadron as previously measured in single-hadron fragmentation functions. This measurement provides additional constraints for the extraction of collinear and transverse-momentum-dependent heavy-flavor fragmentation functions and offers another approach to probing the mechanisms that govern heavy-flavor hadronization.

hep-ex↗

arXiv2026

Precision measurement of CP violation and branching fractions in $B^{\pm} \to K^0_{\mathrm{S}} h^{\pm}$ $(h = π, K)$ decays and search for the rare decay $B_c^{\pm} \to K^0_{\mathrm{S}} K^{\pm}$

The decay $B^{\pm} \to K^0_{\mathrm{S}} π^{\pm}$, with a $CP$ asymmetry expected to be close to zero in the Standard Model, is theoretically clean and sensitive to potential new physics. An analysis of the decays $B^{\pm} \to K^0_{\mathrm{S}} π^{\pm}$ and $B^{\pm} \to K^0_{\mathrm{S}} K^{\pm}$ is performed using proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of $13\,\mathrm{TeV}$, corresponding to an integrated luminosity of $5.4\,\mathrm{fb}^{-1}$. The \CP asymmetries are determined to be ${\cal A}^{CP}(B^{\pm} \to K^0_{\mathrm{S}} π^{\pm})=-0.028\pm 0.009\pm 0.009$ and ${\cal A}^{CP}(B^{\pm} \to K^0_{\mathrm{S}} K^{\pm})=0.118\pm 0.062 \pm 0.031$, and the branching fraction ratio is measured to be ${\cal B}(B^{\pm} \to K^0_{\mathrm{S}} K^{\pm})/{\cal B}(B^{\pm} \to K^0_{\mathrm{S}} π^{\pm})=0.055\pm 0.004 \pm 0.002$, where the first uncertainties are statistical and the second are systematic. These results are the most precise measurements of these quantities to date. A search for the rare decay $B_c^{\pm} \to K^0_{\mathrm{S}} K^{\pm}$ is also performed. No significant signal is observed, and the upper limit on the product of the branching fraction ratio ${\cal B}(B_c^{\pm} \to K^0_{\mathrm{S}} K^{\pm})/{\cal B}(B^{\pm} \to K^0_{\mathrm{S}} π^{\pm})$ and the fragmentation-fraction ratio $f_c/f_u$ is set to be 0.015 (0.016) at the 90\% (95\%) confidence level.

hep-ex↗

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.

hep-ex↗

arXiv2026

Search for the lepton-flavour violating decays $B^+ \to π^+ μ^\pm e^\mp$

The first search for the lepton-flavour violating decays $B^+ \to π^+ μ^{\pm} e^{\mp}$ in proton-proton collisions is presented, using data collected by the LHCb experiment between 2011 and 2018, corresponding to an integrated luminosity of 9 fb$^{-1}$. No significant signal is observed and an upper limit on the branching fraction is set at $\mathcal{B}(B^+ \to π^+ μ^{\pm} e^{\mp}) < 1.8 \times 10^{-9}$ at the $90\%$ confidence level, two orders of magnitude more restrictive than the current world average. This is the first constraint on lepton-flavour violating $b \to d$ quark transitions at the LHC and also sets the most stringent upper limits to date on $b \to d μ^{\pm} e^{\mp}$ transitions. Limits on left-handed and scalar scenarios beyond the Standard Model are also reported.

hep-ex↗