arXiv subjects

P. Adlarson

Publications and source records attributed to P. Adlarson.

At least 145 records · Page 8Linked to original sources

arXiv2026

Observation of the decay $χ_{c1}(3872)\rightarrow J\mskip -3mu/\mskip -2muψμ^+μ^-$

The first observation of the $χ_{c1}(3872)\rightarrow J\mskip -3mu/\mskip -2muψμ^+μ^-$ decay is reported using proton-proton collision data recorded with the LHCb detector corresponding to an integrated luminosity of $9fb^{-1}$. The decay mode is observed for the first time, with a significance of $6.5σ$. Its branching fraction is measured relative to the $χ_{c1}(3872)\rightarrow J\mskip -3mu/\mskip -2muψπ^+π^-$ decay mode \begin{align*} \frac{\cal{BF}(χ_{c1}(3872)\rightarrow J\mskip -3mu/\mskip -2muψμ^+μ^-)}{\cal{BF}(χ_{c1}(3872)\rightarrow J\mskip -3mu/\mskip -2muψπ^+π^-)} = \left(1.68\pm 0.32\pm 0.05\right)\times10^{-3}, \end{align*} where the first uncertainty includes both statistical contributions and systematic contributions which are uncorrelated between data-taking periods, and the second represents the systematic contributions that are correlated between data-taking periods.

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

Evidence of transverse polarization of $Ξ^0$ hyperon in $ψ(3686)\rightarrowΞ^0\barΞ^0$

Using $(2.712\pm0.014)\times10^{9}$ $ψ(3686)$ events collected with the BESIII detector at the BEPCII collider, we report an evidence of $Ξ^{0}$ transverse polarization with a significance of 4.4$σ$, a precise measurement of the branching fraction and the ratios between the $S$-wave and $D$-wave contributions of $ψ(3686)\toΞ^{0}\barΞ^{0}$. The weak decay parameters ($ϕ_{Ξ^0/\barΞ^{0}}$, $α_{Ξ^0/\barΞ^{0}}$) and the angular distribution ($α_ψ$) are also measured with higher precision compared to the previous measurements. Furthermore, two the $CP$ observables are also determined to be $A^{Ξ^0}_{CP} = -0.014 \pm 0.030 \pm 0.010$ and $Δϕ^{Ξ^0}_{CP} = 0.000 \pm 0.028 \pm 0.003$~rad, which are still consistent with $CP$ conservation at 1$σ$ level under the current statistics.

hep-ex↗

arXiv2026

First evidence of the $B_s^0\rightarrow K^-π^+γ$ decay

The first search for the $B_s^0\rightarrow K^-π^+γ$ decay in the range $796<m(K^-π^+)<1800\,\text{MeV/}c^2$ is performed using data from proton-proton collisions 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 photons are reconstructed through their conversion into an electron-positron pair, which significantly improves the mass resolution of the reconstructed decays with respect to decays with an unconverted photon. A signal excess with a significance of 3.5 standard deviations is measured, constituting the first experimental evidence for this decay. In the range $796<m(K^-π^+)<996\,\text{MeV/}c^2$, the ratio ${\cal R}$ between the branching fractions of the signal decay and the favoured $\kern 0.18em\overline{\kern -0.18em B}{}^0\rightarrow K^- π^+γ$ decay is measured to be ${\cal R} = (3.7\pm1.2\pm0.4)\times10^{-2}$ where the first uncertainty is statistical and the second is systematic. This measurement is consistent with the value predicted in the Standard Model. In the range $996<m(K^-π^+)<1800\,\text{MeV/}c^2$, the ratio ${\cal R} = (0.2\pm2.7\pm1.3)\times10^{-2}$ is measured.

hep-ex↗

arXiv2026

Observation of a Doubly-strange Hyperon $Ξ(1720)$ in $J/ψ\rightarrow{}K^{-}Σ^0\barΞ^{+}+c.c.$

Based on a sample of $(10087 \pm 44) \times 10^6$ $J/ψ$ events collected with the BESIII detector at BEPCII, we report the first observation of the decay $J/ψ\rightarrow K^- Σ^0 \barΞ^++c.c.$. A partial wave analysis is performed to investigate the involved excited states. In addition to the well-established $Ξ(1690)$, a new doubly-strange hyperon $Ξ(1720) $ is observed decaying to $K^- Σ^0$ with a mass of $1721.0 \pm 5.2_{\rm stat.} \pm 3.4_{\rm syst.} ~{\rm MeV}/c^2$ and a width of $31.3 \pm 18.3_{\rm stat.} \pm 15.4_{\rm syst.} ~{\rm MeV}$, with a statistical significance exceeding $10σ$. The spin-parity hypothesis testing across various quantum number configurations reveals that the spin-parity of $Ξ(1720)$ favors $J^P = {\frac{3}{2}}^+$. Furthermore, the branching fraction of $J/ψ\rightarrow K^- Σ^0 \barΞ^++c.c.$ is determined to be $(2.68 \pm 0.04_{\rm stat.} \pm 0.17_{\rm syst.}) \times 10^{-5}$.

hep-ex↗

arXiv2026

Amplitude Analysis of the Isospin-Violating Decay $J/ψ\rightarrowγηπ^{0}$

Using $(10\,087 \pm 44) \times 10^6$ $J/ψ$ events collected with the BESIII detector, we perform the first amplitude analysis of the process $J/ψ\toγηπ^0$. The decay is dominated by the intermediate processes $J/ψ\toπ^0 b_1(1235)^0 \toγηπ^0$, $J/ψ\toπ^{0}ρ(1450)^0 \toγηπ^0$ and $J/ψ\toηh_1(1170) \toγηπ^0$. Contributions from $J/ψ\toγa_0(980)^0\toγηπ^0$, $J/ψ\toγa_2(1320)^0\toγηπ^0$ and $J/ψ\toγa_2(1700)^0\toγηπ^0$ are observed with a statistical significance exceeding $5σ$, constituting the first observation of radiative transitions of $J/ψ$ to isospin-triplet scalar mesons. The total branching fraction of $J/ψ\toγηπ^0$ is measured to be $(25.7\pm0.3\pm1.5)\times 10^{-6}$, where the first uncertainty is statistical and the second systematic. This result is consistent with the previous measurement, with the precision improved by more than a factor of two.

hep-ex↗

arXiv2026

Search for the decays $X(3872)\to K_{S}^{0}K^{\pm}π^{\mp}$ and $K^*(892)\bar{K}$ at BESIII

Using a 10.9 fb$^{-1}$ data sample collected by the BESIII detector at center-of-mass energies from 4.16 to 4.34 GeV, we search for the charmless decays $X(3872) \to K_{S}^{0}K^{\pm}π^{\mp}$ and $K^*(892)\bar{K}$, where the $X(3872)$ is produced via the radiative process $e^+e^- \to γX(3872)$. No significant signal is observed. We set upper limits on the relative branching fractions $\mathcal{B}[X(3872)\to K_S K^{\pm} π^{\mp}]/\mathcal{B}[X(3872)\toπ^+π^- J/ψ] <0.07$ and $\mathcal{B}[X(3872)\to K^* (892)\bar{K}]/\mathcal{B}[X(3872)\to π^+π^- J/ψ] <0.10$ at the 90$\%$ confidence level. Additionally, upper limits on the product of the cross section $σ[e^+e^-\toγX(3872)]$ and the branching fractions $\mathcal{B}[X(3872)\to K_{S}^{0}K^{\pm}π^{\mp}]$ and $\mathcal{B}[X(3872)\to K^*(892)\bar{K}]$ are reported at each energy point. In all cases, $K^*(892)\bar{K}$ refers to the sum of the modes $K^*(892)^+K^{-}+\text{c.c.}$ and $K^*(892)^0\bar{K}^0+\text{c.c.}$, where c.c. denotes the corresponding charge-conjugate modes.

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

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.

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

Branching fraction measurement of the $\mathitΛ \to p μ^- \overlineν_μ$ decay

A measurement of the branching fraction for the decay $\mathitΛ \to p μ^- \overlineν_μ$ is presented using $\textit{pp}$ collision data collected by the LHCb experiment at a centre-of-mass energy of 13 TeV. The analysis is based on data recorded between 2016 and 2018, corresponding to an integrated luminosity of $5.4 \ \text{fb}^{-1}$. The result is obtained using $\mathitΛ \to p π^-$ decays as a normalisation channel. The measured branching fraction is $B(\mathitΛ \to p μ^- \overlineν_μ)= (1.462 \pm 0.016 \pm 0.100 \pm 0.011 ) \times 10^{-4}$, where the uncertainties are statistical, systematic, and due to the limited knowledge of the normalisation mode branching fraction, respectively. This result improves the precision of the branching fraction measurement by a factor of two compared to the previous best measurement and sets a more stringent bound on lepton flavour universality in $s \to u$ quark transitions. It is consistent with previous measurements, and the extracted lepton flavour universality test observable, $R^{μe} = \frac{Γ(\mathitΛ \to p μ^- \overlineν_μ)}{Γ(\mathitΛ \to p e^- \overlineν_e)} = 0.175 \pm 0.012$, agrees with the Standard Model prediction.

hep-ex↗

arXiv2026

Observation of a threshold enhancement in the $π^+π^-$ spectrum in $ψ(3686) \rightarrow π^{+}π^{-}J/ψ$ decays

Based on the $(2712.4\pm14.4)\times 10^{6}$ $ψ(3686)$ events collected with the BESIII detector, we present a high-precision study of the $π^+π^-$ mass spectrum in $ψ(3686)\rightarrowπ^{+}π^{-}J/ψ$ decays. A clear resonance like structure is observed near the $π^+π^-$ mass threshold for the first time. A fit with a Breit-Wigner function yields a mass of $285.6\pm 2.5~{\rm MeV}/c^2$ and a width of $16.3\pm 0.9~{\rm MeV}$ with a statistical significance exceeding 10$σ$. To interpret the data, we incorporate final state interactions (FSI) within two theoretical frameworks: chiral perturbation theory (ChPT) and QCD multipole expansion (QCDME). ChPT describes the spectrum above 0.3 GeV/$c^2$ but fails to reproduce the threshold enhancement. In contrast, the QCDME model assuming the $ψ(3686)$ is an admixture of S and D wave charmonium reproduces the data well. The pronounced dip near 0.3 GeV/$c^2$ offers new insight into the interplay between chiral dynamics and low-energy QCD.

hep-ex↗

arXiv2026

First Observation of \boldmath{$D^+ \to a_0(980)ρ$ and $D^+ \to a_0(980)^+ f_0(500)$} in \boldmath{$D^+ \to π^+π^+π^-η$ and $D^+ \to π^+π^0π^0η$} Decays

We perform the first amplitude analysis of the singly Cabibbo-suppressed decays $D^+ \to π^+ π^{+(0)} π^{-(0)} η$, using $e^+e^-$ collision data collected with the BESIII detector at the center-of-mass energy of 3.773\,GeV, corresponding to an integrated luminosity of 20.3 $\rm{fb}^{-1}$. The absolute branching fractions of the $D^+ \to π^+ π^+ π^- η$ and $D^+ \to π^+ π^0 π^0 η$ decays are measured to be $(3.20\pm0.06_{\text{stat.}}\pm0.03_{\text{syst.}})\times 10^{-3}$ and $(2.43 \pm 0.11_{\text{stat.}} \pm 0.04_{\text{syst.}}) \times 10^{-3}$, respectively. % , both achieving three times better precision than the current PDG values. The decay process $D^{+}\to a_0(980)^{+}f_0(500)$ is observed for the first time with an unexpectedly large branching fraction. Moreover, we observe the decays $D^+ \to a_0(980)^{+(0)} ρ(770)^{0(+)}$ and measure the ratio $r_{+/0} \equiv \frac{\mathcal{B}(D^+ \to a_0(980)^+ ρ(770)^0)}{\mathcal{B}(D^+ \to a_0(980)^0 ρ(770)^+)}$ for the first time to be $0.55\pm0.08_{\text{stat.}}\pm0.05_{\text{syst.}}$. These results offer a novel insight into our comprehension of the nature of the $a_0(980)$ and $f_0(500)$ states.

hep-ex↗

arXiv2026

Observation of the Exotic State $π_{1}(1600)$ in $ψ(2S)\rightarrowγχ_{c1},χ_{c1}\rightarrowπ^{+}π^{-}η'$

A partial wave analysis of the process $ψ(2S)\rightarrowγχ_{c1}, χ_{c1}\rightarrowπ^+π^-η^{\prime}$ is performed using $(2712.4\pm14.3)\times10^{6}$ $ψ(2S)$ events collected with the BESIII detector. An isovector state with exotic quantum numbers $J^{PC}=1^{-+}$, denoted as $π_{1}(1600)$, is observed for the first time in the charmonium decay of $χ_{c1}\rightarrowπ_{1}^{\pm}(1600)π^{\mp}$, $π_{1}^{\pm}(1600)\rightarrowπ^{\pm}η^{\prime}$ with a statistical significance over $21σ$. Its mass and width are determined to be $1828 \pm 8 ({\rm stat})^{+11}_{-33}({\rm syst})~\mathrm{MeV}/c^2$ and $638 \pm 26 ({\rm stat})^{+35}_{-86}({\rm syst})~\mathrm{MeV}$, respectively, using a relativistic Breit-Wigner function with a mass-dependent width. The corresponding product of branching fractions is determined to be $\mathcal{B}\left[χ_{c1}\rightarrowπ_{1}(1600)^{\pm}π^{\mp} \right] \times \mathcal{B}\left[π_{1}(1600)^{\pm}\rightarrowπ^{\pm}η^{\prime}\right] = \left( 4.30 \pm 0.14 ({\rm stat})^{+1.04}_{-1.03}({\rm syst})~ \right) \times 10^{-4}$.

hep-ex↗

arXiv2026

Observation of $\barΛp\to K^{+}π^{+}π^{-}π^{0}$ and $\barΛp\to K^{+}π^{+}π^{-}2π^{0}$

Using $(10087 \pm 44) \times 10^6$ $J/ψ$ events collected with the BESIII detector at a center-of-mass energy of $\sqrt{s}=3.097$ GeV, the antihyperon-nucleon annihilation processes $\barΛ p \to K^+ π^+ π^- + kπ^0$ ($k=1,2,3$) are studied at an incident $\barΛ$ momentum of approximately 1.074 GeV/$c$. The reactions $\barΛ p \to K^+ π^+ π^- π^0$ and $\barΛ p \to K^+ π^+ π^- 2π^0$ are observed for the first time, with corresponding cross sections $σ_{\barΛ p \to K^+ π^+ π^- π^0} = 8.5^{+1.2}_{-1.1} (\rm{stat.}) \pm 0.4 (\rm {syst.})$ mb and $σ_{\barΛ p \to K^+ π^+ π^- 2π^0} = 7.9^{+1.9}_{-1.7} \pm 0.4$ mb. No significant signal is found for $\barΛ p \to K^+ π^+ π^- 3π^0$, and an upper limit of 7.2 mb is set at a 90\% confidence level. An evidence for the $K^{*}(892)^+$ resonance is seen in the $K^+π^0$ invariant mass spectrum $M_{K^+π^0}$ for $k=1$, and the corresponding cross section for $\barΛ p \to K^{*}(892)^+ π^+ π^-$ is measured to be $σ_{\barΛ p \to K^{*}(892)^+ π^+ π^-} = 12.5^{+3.8}_{-3.4} \pm 1.2$ mb. Owing to the limited statistics, possible interference effects are not considered. These findings offer crucial input to deepen our understanding of the antihyperon-nucleon interactions.

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

Measurement of the branching fractions of $χ_{cJ} \to π^{+}π^{-}π^{0}π^{0}$ via $ψ(3686) \to γχ_{cJ}$

Using $(2712.4\pm14.3)\times 10^6$ $ψ(3686)$ events collected with the BESIII detector operating at BEPCII, the branching fractions of $χ_{cJ}\toπ^+π^-π^0π^0$ ($J=0,~1,~2$) are measured via the radiative transition $ψ(3686)\toγχ_{cJ}$. The results are $\mathcal{B}(χ_{c0} \to π^{+}π^{-}π^{0}π^{0}) = (3.10 \pm 0.01 \pm 0.14) \times 10^{-2}$, $\mathcal{B}(χ_{c1} \to π^{+}π^{-}π^{0}π^{0}) = (1.16 \pm 0.01 \pm 0.05) \times 10^{-2}$, and $\mathcal{B}(χ_{c2} \to π^{+}π^{-}π^{0}π^{0}) = (1.92 \pm 0.01 \pm 0.08) \times 10^{-2}$, where the first uncertainties are statistical and the second systematic. The dominant intermediate states are found to be $χ_{cJ}\toρ^+ρ^-$. These results supersede the previous most precise measurements and provide significantly improved precision.

hep-ex↗