arXiv subjects

P. Adlarson

Publications and source records attributed to P. Adlarson.

At least 271 records · Page 15Linked to original sources

arXiv2025

Improved Measurements of $D^+ \to ηe^+ν_e$ and $D^+ \to ημ^+ν_μ$

Using 20.3 fb$^{-1}$ of $e^+e^-$ collision data collected at the center-of-mass energy of 3.773 GeV with the BESIII detector, we measure the branching fractions of $D^+\to ηe^+ν_e$ and $D^+\to ημ^+ν_μ$ to be $(9.75\pm0.29\pm0.28)\times10^{-4}$ and $(9.08\pm0.35\pm0.23)\times10^{-4}$, where the first and second uncertainties are statistical and systematic, respectively. From a simultaneous fit to their partial decay rates, we determine the product of the hadronic form factor $f^η_+(0)$ and the modulus of the $c\to d$ Cabibbo-Kobayashi-Maskawa matrix element $|V_{cd}|$ to be $f^η_+(0)|V_{cd}|=0.078\pm0.002\pm0.001$. Taking the $|V_{cd}|$ value from the Standard Model global fit as input, we obtain $f^η_+(0)=0.345\pm0.008\pm0.003$. The ratio between the measured branching fractions of $D^+\toη^+μ^+ν_μ$ and $D^+\toηe^+ν_e$, is determined to be $0.93\pm0.05_{\rm stat.}\pm0.02_{\rm syst.}$, indicating no violation of lepton flavor universality.

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arXiv2025

Precision Measurement of the Branching Fraction of $D^{+}\to μ^{+}ν_μ$

Using $20.3~\mathrm{fb}^{-1}$ of $e^+e^-$ collision data collected at a center-of-mass energy of $E_{\rm c.m.}=3.773$ GeV with the BESIII detector operating at the BEPCII collider, we determine the branching fraction of the leptonic decay $D^+\toμ^+ν_μ$ to be $(4.034\pm0.080_{\rm stat}\pm0.040_{\rm syst})\times10^{-4}$. Interpreting our measurement with knowledge of the Fermi coupling constant $G_F$, the masses of the $D^+$ and $μ^+$ as well as the lifetime of the $D^+$, we determine $f_{D^+}|V_{cd}|=(48.02\pm0.48_{\rm stat}\pm0.24_{\rm syst}\pm0.12_{\rm input}\pm0.15_{\rm EM})~\mathrm{MeV}$ after taking into account necessary radiative corrections. This result is a factor of 2.3 more precise than the previous best measurement. Using the value of the magnitude of the $c\to d$ Cabibbo-Kobayashi-Maskawa matrix element $|V_{cd}|$ given by the global standard model fit, we obtain the $D^+$ decay constant $f_{D^+}=(213.5\pm2.1_{\rm stat}\pm1.1_{\rm syst}\pm0.8_{\rm input}\pm0.7_{\rm EM})$\,MeV. Alternatively, using the value of $f_{D^+}$ from a precise lattice quantum chromodynamics calculation, we extract $|V_{cd}|=0.2265\pm0.0023_{\rm stat}\pm0.0011_{\rm syst}\pm0.0009_{\rm input}\pm0.0007_{\rm EM}$.

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arXiv2025

First Measurement of the $D_s^+\rightarrow K^0μ^+ν_μ$ Decay

We report the first measurement of the semileptonic decay $D^+_s \rightarrow K^0μ^+ν_μ$, using a sample of $e^+e^-$ annihilation data corresponding to an integrated luminosity of $7.33~\mathrm{fb}^{-1}$ collected at center-of-mass energies between 4.128 to 4.226~GeV with the BESIII detector at the BEPCII collider. The branching fraction of the decay is measured to be $\mathcal{B}(D^+_s\rightarrow K^0μ^+ν_μ) = (2.89 \pm 0.27_{\rm stat} \pm 0.12_{\rm syst})\times 10^{-3}$, where the first uncertainty is statistical and the second is systematic. Based on a simultaneous fit to the partial decay rates in $q^2$ intervals measured in $D^+_s \rightarrow K^0μ^+ν_μ$ and $D^+_s \rightarrow K^0e^+ν_{e}$ decays, the product value of the form factor $f^{K^0}_{+}(0)$ and the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cd}|$ is measured to be $f^{K^0}_{+}(0)|V_{cd}|=0.140\pm0.008_{\rm stat}\pm0.002_{\rm syst}$. Using $|V_{cd}|=0.22486\pm0.00068$ as an input, the hadronic form factor is determined to be $f^{K^0}_{+}(0)=0.623\pm0.036_{\rm stat} \pm 0.009_{\rm syst}$ at $q^2=0$. This is the most precise determination of $f^{K^0}_{+}(0)$ in the $D^+_s \rightarrow K^0$ transition to date. The measured branching fraction and form factor presented in this work provide the most stringent test on various non-perturbative theoretical calculations. Taking $f^{K^0}_{+}(0)=0.6307\pm0.0020$ from lattice calculations as an input, we obtain $|V_{cd}|=0.220\pm0.013_{\rm stat}\pm0.003_{\rm syst}\pm0.001_{\rm LQCD}$, which is the most precise determination of $|V_{cd}|$ using the $D_s^+\rightarrow K^0\ell^+ν_{\ell}$ decays. In addition, lepton flavor universality is tested for the first time with $D^+_s \rightarrow K^0\ell^+ν_{\ell}$ decays in full and separate $q^2$ intervals. No obvious violation is found.

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arXiv2025

Measurement of the $Ω_c^0$ and $Ξ_c^0$ baryon lifetimes using hadronic $b$-baryon decays

The lifetimes of the $Ω_c^0$ and $Ξ_c^0$ baryons are measured using a $pp$ collision dataset collected by the LHCb experiment, corresponding to an integrated luminosity of $9~\rm{fb^{-1}}$. The charm baryons are produced in the fully reconstructed decay chains $Ω_b^- \rightarrow Ω_c^0 (\rightarrow pK^-K^-π^+)~π^-$ and $Ξ_b^- \rightarrow Ξ_c^0 (\rightarrow pK^-K^-π^+)~π^-$. The measurement uses topologically and kinematically similar $B^- \rightarrow D^0(\rightarrow K^-K^+π^-π^+)~π^-$ decays for normalisation. The measured lifetimes are $τ_{Ω_c^0} = 276.3 \pm 19.4~\rm{(stat)} \pm 1.8~\rm{(syst)} \pm 0.7~(τ_{D^0})~\rm{fs}$, $τ_{Ξ_c^0} = 149.2 \pm ~\,2.5~\rm{(stat)} \pm 0.9~\rm{(syst)} \pm 0.4~(τ_{D^0})~\rm{fs}$, where the first uncertainty is statistical, the second systematic and the third due to the uncertainty of the $D^0$ lifetime. These results are consistent with previous measurements performed by the LHCb experiment.

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arXiv2025

Search for $J/ψ\rightarrow K^{0}_{S}K^{0}_{S}$ and $ψ(3686)\rightarrow K^{0}_{S}K^{0}_{S}$

Using data samples of $(10087\pm 44)\times10^{6}$ $J/ψ$ events and $(2712.4\pm 14.3)\times10^{6}$ $ψ(3686)$ events collected with the BESIII detector at the BEPCII collider, we search for the CP violating decays $J/ψ\rightarrow K^{0}_{S}K^{0}_{S}$ and $ψ(3686)\rightarrow K^{0}_{S}K^{0}_{S}$. No significant signals are observed over the expected background yields. The upper limits on their branching fractions are set as $\mathcal{B}(J/ψ\rightarrow K^{0}_{S}K^{0}_{S}) <4.7\times 10^{-9}$ and $\mathcal{B}(ψ(3686)\rightarrow K^{0}_{S}K^{0}_{S}) <1.1\times 10^{-8}$ at the 90% confidence level. These results improve the previous limits by a factor of three for $J/ψ\rightarrow K^{0}_{S} K^{0}_{S}$ and two orders of magnitude for $ψ(3686)\rightarrow K^{0}_{S} K^{0}_{S}$.

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arXiv2025

First observation of the $\mathitΛ_b^{0}\!\rightarrow\mathitΛ_{c}^{+}D_{s}^{-}K^{+}K^{-}$ decay and search for pentaquarks in the $\mathitΛ_{c}^{+}D_{s}^{-}$ system

The $\mathitΛ_b^{0}\!\rightarrow\mathitΛ_{c}^{+}D_{s}^{-}K^{+}K^{-}$ decay is observed for the first time using the data sample from proton-proton collisions recorded at a center-of-mass energy of $13\,\text{TeV}$ with the LHCb detector, corresponding to an integrated luminosity of $6\,\text{fb}^{-1}$. The ratio of branching fraction to that of $\mathitΛ_b^{0} \!\rightarrow\mathitΛ_{c}^{+}D_{s}^{-}$ decays is measured as $0.0141 \pm 0.0019 \pm 0.0012$, where the first uncertainty is statistical and the second systematic. A search for hidden-charm pentaquarks with strangeness is performed in the $\mathitΛ_{c}^{+}D_{s}^{-}$ system. No evidence is found, and upper limits on the production ratio of $P_{c\bar{c}s}(4338)^0$ and $P_{c\bar{c}s}(4459)^0$ pentaquarks relative to the $\mathitΛ_{c}^{+}D_{s}^{-}$ final state are set at the $95\%$ confidence level as $0.12$ and $0.20$, respectively.

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arXiv2025

Precision measurement of the ${\itΞ}_b^0$ baryon lifetime

A sample of $pp$ collision data, corresponding to an integrated luminosity of 5.4 fb$^{-1}$ and collected by the LHCb experiment during LHC Run 2, is used to measure the ratio of the lifetime of the ${\itΞ}_b^0$ baryon to that of the ${\itΛ}_b^0$ baryon, $r_τ\equivτ_{{\itΞ}_b^0}/τ_{{\itΛ}_b^0}$. The value ${r_τ^{\rm Run\,2}=1.004\pm0.009\pm0.006}$ is obtained, where the first uncertainty is statistical and the second systematic. This value is averaged with the corresponding value from Run 1 to obtain ${r_τ = 1.004\pm0.008\pm0.005}$. Multiplying by the known value of the ${\itΛ}_b^0$ lifetime yields ${{τ_{{\itΞ}_b^0}} = 1.475\pm0.012\pm0.008\pm0.009~{\rm ps}}$, where the last uncertainty is due to the limited knowledge of the ${\itΛ}_b^0$ lifetime. This measurement improves the precision of the current world average of the ${\itΞ}_b^0$ lifetime by about a factor of two, and is in good agreement with the most recent theoretical predictions.

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arXiv2025

Search for the lepton number violating decay $η\to π^+π^+e^-e^- + c.c.$ via $J/ψ\toϕη$

Based on a sample of $ (10.087\pm 0.044)\times 10^{9} J/ψ$ events collected by the BESIII detector at the BEPCII collider, we perform the first search for the lepton number violating decay $η\to π^+π^+ e^-e^- + \text{c.c.}$ No signal is found, and an upper limit on the branching fraction of $η\to π^+π^+ e^-e^- + c.c.$ is set to be $4.6 \times 10^{-6}$ at the 90\% confidence level.

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arXiv2025

Observation of Transverse Polarization and Determination of Psionic Form Factors of the $Λ$ Hyperon at $\sqrt{s}= 3.773$ GeV

Using a data sample of $e^{+}e^{-}$ collision data corresponding to an integrated luminosity of 20.3 fb$^{-1}$ collected by the BESIII detector at the BEPCII collider, we present an observation of transverse polarization and a complete determination of the psionic form factors of the $Λ$ hyperon in $e^{+}e^{-}\toΛ\barΛ$ decay with the entangled $Λ-\barΛ$ pair at $\sqrt{s}=3.773$ GeV. The relative phase between the psionic form factors is determined to be $ΔΦ=(1.53\pm0.36\pm0.03)$~rad with a significance of 5.5 $σ$ taking into account systematic uncertainty. This result indicates a non-zero phase between the transition amplitudes of the $Λ\barΛ$ helicity states. Additionally, we measure the angular distribution parameter and the modulus of the ratio between the psionic form factors to be $η=0.86\pm0.05\pm0.03$ and $R(s)=|G_{E}(s)/G_{M}(s)|=0.47\pm0.08\pm0.05$, where the first uncertainty is statistical and the second systematic.

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arXiv2025

Measurements of $ψ{(2S)}$ and $χ_{c1}(3872)$ production within fully reconstructed jets

This paper presents the first measurement of $ψ{(2S)}$ and $χ_{c1}(3872)$ meson production within fully reconstructed jets. Each quarkonium state (tag) is reconstructed via its decay to the $J/ψ$($\rightarrowμ^+μ^-$)$π^+π^-$ final state in the forward region using proton-proton collision data collected by the LHCb experiment at the center-of-mass-energy of $13 \text{TeV}$ in 2016, corresponding to an integrated luminosity of $1.64 \text{fb}^{-1}$. The fragmentation function, presented as the ratio of the quarkonium-tag transverse momentum to the full jet transverse momentum ($p_{\mathrm{T}}(\text{tag})/p_{\mathrm{T}}(\text{jet})$), is measured differentially in $p_{\mathrm{T}}(\text{jet})$ and $p_{\mathrm{T}}(\text{tag})$ bins. The distributions are separated into promptly produced quarkonia from proton-proton collisions and quarkonia produced from displaced $b$-hadron decays. While the displaced quarkonia fragmentation functions are in general well described by parton-shower predictions, the prompt quarkonium distributions differ significantly from fixed-order non-relativistic QCD (NRQCD) predictions followed by a QCD parton shower.

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arXiv2025

Search for the radiative leptonic decay $D^+\toγe^+ν_e$ using Deep Learning

Using 20.3$~\rm fb^{-1}$ of $e^+e^-$ annihilation data collected at a center-of-mass energy of 3.773$~\rm GeV$ with the BESIII detector, we report an improved search for the radiative leptonic decay $D^+\toγe^+ν_e$. An upper limit on its partial branching fraction for photon energies $E_γ>10~\rm MeV$ was determined to be $1.2\times10^{-5}$ at 90\% confidence level; this excludes most current theoretical predictions. A sophisticated deep learning approach, which includes thorough validation and is based on the Transformer architecture, was implemented to efficiently distinguish the signal from massive backgrounds.

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arXiv2025

Search for sub-GeV invisible particles in inclusive decays of $J/ψ$ to $ϕ$

A search for an invisible particle, $X$, with a mass between 0 and 0.96 $\textrm{GeV}/\textit{c}^{2}$, is performed in the process $J/ψ\rightarrowϕ+ X$ using $(8774.0\pm39.4)\times10^{6}$ $J/ψ$ events collected with the BESIII detector from 2017 to 2019. The $ϕ$ meson is fully reconstructed and an efficient veto of photons, neutral and charged hadrons up to twice the $K_L^0$ mass is applied to the rest of the event and the recoil mass against the $ϕ$ is obtained precisely from the kinematic constraint in the event. No significant signal over the expected background is observed in the investigated region and the upper limit on the inclusive branching fraction of $J/ψ\rightarrowϕ+ X$ is determined to be $7.0\times10^{-8}$ at 90\% confidence level. Upper limits at a 90\% confidence level are also given for this branching fraction as a function of the invisible particle mass, varying from $4\times10^{-9}$ to $4\times10^{-8}$ over the investigated mass range. Additionally, a 90\% confidence level upper limit on the branching fraction of $η\rightarrow \rm{invisible}$ is determined to $2.4\times10^{-5}$, which improves the previous best results by more than four times. The analysis technique in this work offers a clean window to search for sub-GeV invisible particles, which can be adapted for other $J/ψ$ decays and direct $e^+e^-$ annihilation experiments in future studies, and improve the sensitivity by orders of magnitude.

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arXiv2025

First Observation of $Λ$ Hyperon Transverse Polarization in $ψ(3686)\toΛ\barΛ$

Based on $(448.1\pm2.9)\times10^{6}$ $ψ(3686)$ events collected with the BESIII detector at the BEPCII collider, we present the first observation of spin transverse polarization of $Λ$ and $\barΛ$ hyperons produced coherently in the decay $ψ(3686)\toΛ(\to pπ^-)\barΛ(\to\bar pπ^+)$. The relative phase between the electric and magnetic hadronic form factors is measured to be $ΔΦ=(21.0\pm3.7_{\rm stat.}\pm0.8_{\rm syst.})^{\circ}$. The angular distribution parameter $α_ψ=0.83\pm0.02_{\rm stat.}\pm0.01_{\rm syst.}$ is determined with a precision improved by a factor of 3.7 compared to the previous measurement. The relative phase between the $S$- and $D$-wave amplitudes for $Λ\barΛ$ is observed, and the effective interaction radius is determined to be $0.0450\pm0.0026_{\rm stat.}\pm0.0012_{\rm syst.}$ fm. These results provide new insights into the strong interaction mechanisms and the internal structure of baryons.

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arXiv2025

Measurement of the space-like $π^0$ transition form factor

Based on $2.93\,\text{fb}^{-1}$ of $e^+e^-$ collision data taken with the BESIII detector at a center-of-mass energy of $3.773\,\text{GeV}$, the two-photon fusion process $e^+e^-\to e^+e^-π^0$ is investigated using a single-tag approach. The differential Born cross section $\text{d}σ/\text{d}Q^2$ and the space-like transition form factor $|F(Q^2)|$ of the $π^0$ are measured as functions of the squared momentum transfer $Q^2$ of the tagged, scattered lepton. The measurement covers the range $0.2 < Q^2 < 3.5\,\text{GeV}^2$. The results are consistent with previous measurements, and provide a significant improvement for $Q^2<2\,\text{GeV}^2$.

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arXiv2025

Angular analysis of $B^0\rightarrow K^{*0}e^{+}e^{-}$ decays

An angular analysis of $B^0\rightarrow K^{*0}e^{+}e^{-}$ decays is presented using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb$^{-1}$. The analysis is performed in the region of the dilepton invariant mass squared of 1.1-6.0 GeV$^{2}/c^{4}$. In addition, a test of lepton flavour universality is performed by comparing the obtained angular observables with those measured in $B^0\rightarrow K^{*0}μ^{+}μ^{-}$ decays. In general, the angular observables are found to be consistent with the Standard Model expectations as well as with global analyses of other $b \rightarrow s \ell^{+} \ell^{-}$ processes, where $\ell$ is either a muon or an electron. No sign of lepton-flavour-violating effects is observed.

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arXiv2025

Observation of the $Λ_b^0 \to J/ψΞ^- K^+$ and $Ξ_b^0 \to J/ψΞ^- π^+$ decays

The first observation of the $Ξ_b^0 \to J/ψΞ^- π^+$ decay and the most precise measurement of the branching fraction of the $Λ_b^0 \to J/ψΞ^- K^+$ decay are reported, using proton-proton collision data from the LHCb experiment collected in 2016--2018 at a centre-of-mass energy of 13~TeV, corresponding to an integrated luminosity of 5.4~fb$^{-1}$. Using the $Λ_b^0 \to J/ψΛ$ and $Ξ_b^0 \to J/ψΞ^-$ decays as normalisation channels, the ratios of branching fractions are measured to be: \[ \frac{\mathcal{B}(Λ_b^0 \to J/ψΞ^- K^+)}{\mathcal{B}(Λ_b^0 \to J/ψΛ)} = (1.17 \pm 0.14 \pm 0.08)\times 10^{-2} \, , \] \[ \frac{\mathcal{B}(Ξ_b^0 \to J/ψΞ^- π^+)}{\mathcal{B}(Ξ_b^0 \to J/ψΞ^-)} = (11.9 \pm 1.4 \pm 0.6)\times 10^{-2}\, , \] where the first uncertainty is statistical and the second systematic.

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arXiv2025

Observation of exotic $J/ψϕ$ resonant structure in diffractive processes in proton-proton collisions

The first study of $J/ψϕ$ production in diffractive processes in proton-proton collisions is presented. The study is based on an LHCb dataset recorded at centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5 fb$^{-1}$. The data disfavour a nonresonant $J/ψϕ$ production but are consistent with a resonant model including several resonant states observed previously only in $B^+ \to J/ψϕK^+$ decays. The $χ_{c0}(4500)$ state is observed with a significance over $6σ$ and the $χ_{c1}(4274)$ is confirmed with a significance of more than $4σ$.

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arXiv2025

Three-pion Bose-Einstein correlations measured in proton-proton collisions

A study on the Bose-Einstein correlations for triplets of same-sign pions is presented. The analysis is performed using proton-proton collisions at a centre-of-mass energy of $\sqrt{s}$ = 7 TeV, recorded by the LHCb experiment, corresponding to an integrated luminosity of 1.0 fb$^{-1}$. For the first time, the results are interpreted in the core-halo model. The parameters of the model are determined in regions of charged-particle multiplicity. This measurement provides insight into the nature of hadronisation in terms of coherence, showing a coherent emission of pions.

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