arXiv subjects

P. Adlarson

Publications and source records attributed to P. Adlarson.

At least 487 records · Page 27Linked to original sources

arXiv2024

Measurement of associated $J/ψ$-$ψ(2S)$ production cross-section in $pp$ collisions at $\sqrt{s}=13$ TeV

The cross-section of associated $J/ψ$-$ψ(2S)$ production in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=13$ TeV is measured using a data sample corresponding to an integrated luminosity of 4.2 fb$^{-1}$, collected by the LHCb experiment. The measurement is performed for both $J/ψ$ and $ψ(2S)$ mesons having transverse momentum $p_{\text{T}}<14$ GeV/$c$ and rapidity $2.0<y<4.5$, assuming negligible polarisation of the $J/ψ$ and $ψ(2S)$ mesons. The production cross-section is measured to be $4.5\pm0.7\pm0.3$ nb, where the first uncertainty is statistical and the second systematic. The differential cross-sections are measured as functions of several kinematic variables of the $J/ψ$-$ψ(2S)$ candidates. The results are combined with a measurement of $J/ψ$-$J/ψ$ production, giving a cross-section ratio between $J/ψ$-$ψ(2S)$ and $J/ψ$-$J/ψ$ production of $0.274\pm0.044\pm0.008$, where the first uncertainty is statistical and the second systematic.

hep-ex↗

arXiv2024

Determination of the number of $ψ(3686)$ events taken at BESIII

The number of $ψ(3686)$ events collected by the BESIII detector during the 2021 run period is determined to be $(2259.3\pm 11.1)\times 10^6$ by counting inclusive $ψ(3686)$ hadronic events. The uncertainty is systematic and the statistical uncertainty is negligible. Meanwhile, the numbers of $ψ(3686)$ events collected during the 2009 and 2012 run periods are updated to be $(107.7\pm0.6)\times 10^6$ and $(345.4\pm 2.6)\times 10^6$, respectively. Both numbers are consistent with the previous measurements within one standard deviation. The total number of $ψ(3686)$ events in the three data samples is $(2712.4\pm14.3)\times10^6$.

hep-ex↗

arXiv2024

Measurement of the Branching Fraction of $B^{0} \rightarrow J/ψπ^{0}$ Decays

The ratio of branching fractions between $B^{0} \rightarrow J/ψπ^{0}$ and $B^{+} \rightarrow J/ψK^{*+}$ decays is measured with proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb$^{-1}$. The measured value is $\frac{\mathcal{B}_{B^{0} \rightarrow J/ψπ^{0}}}{\mathcal{B}_{B^{+} \rightarrow J/ψK^{*+}}} = (1.153 \pm 0.053 \pm 0.048 ) \times 10^{-2}$, where the first uncertainty is statistical and the second is systematic. The branching fraction for $B^{0} \rightarrow J/ψπ^{0}$ decays is determined using the branching fraction of the normalisation channel, resulting in $\mathcal{B}_{B^{0} \rightarrow J/ψπ^{0}} = (1.670 \pm 0.077 \pm 0.069 \pm 0.095) \times 10^{-5}$, where the last uncertainty corresponds to that of the external input. This result is consistent with the current world average value and competitive with the most precise single measurement to date.

hep-ex↗

arXiv2024

Study of the decays $χ_{cJ}\toΛ\barΛω$

Using $(27.12\pm 0.14)\times10^{8}$ $ψ(3686)$ events collected with the BESIII detector, we present the first observation of the decays $χ_{cJ}\toΛ\barΛω$, where $J=0, 1, 2$, with statistical significances of $11.7 σ, 11.2 σ$, and $11.8 σ$. The branching fractions of these decays are determined to be $\mathcal{B}(χ_{c0}\toΛ\barΛω)=({2.37 \pm 0.22 \pm 0.23}) \times 10^{-4}$, $\mathcal{B}(χ_{c1}\toΛ\barΛω)=({1.01 \pm 0.10 \pm 0.11}) \times 10^{-4}$, and $\mathcal{B}(χ_{c2}\toΛ\barΛω)=({1.40 \pm 0.13 \pm 0.17}) \times 10^{-4}$, where the first uncertainties are statistical and the second are systematic. We observe no clear intermediate structures.

hep-ex↗

arXiv2024

Search for $B_c^+\toπ^+μ^+μ^-$ decays and measurement of the branching fraction ratio ${\cal B}(B_c^+\toψ(2S)π^+)/{\cal B}(B_c^+\to J/ψπ^+)$

The first search for nonresonant $B_c^+\toπ^+μ^+μ^-$ decays is reported. The analysis uses proton-proton collision data collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 fb$^{-1}$. No evidence for an excess of signal events over background is observed and an upper limit is set on the branching fraction ratio ${\cal B}(B_c^+\toπ^+μ^+μ^-)/{\cal B}(B_c^+\to J/ψπ^+) < 2.1\times 10^{-4}$ at $90\%$ confidence level. Additionally, an updated measurement of the ratio of the $B_c^+\toψ(2S)π^+$ and $B_c^+\to J/ψπ^+$ branching fractions is reported. The ratio ${\cal B}(B_c^+\toψ(2S)π^+)/{\cal B}(B_c^+\to J/ψπ^+)$ is measured to be $0.254\pm 0.018 \pm 0.003 \pm 0.005$, where the first uncertainty is statistical, the second systematic, and the third is due to the uncertainties on the branching fractions of the leptonic $J/ψ$ and $ψ(2S)$ decays. This measurement is the most precise to date and is consistent with previous LHCb results.

hep-ex↗

arXiv2024

Precision measurement of the branching fraction of \boldmath $J/ψ\rightarrow K^+K^-$ via $ψ(2S)\rightarrow π^+π^-J/ψ$

Using a sample of $448.1 \times 10^6$ $ψ(2S)$ events collected with the BESIII detector, we perform a study of the decay $J/ψ\rightarrow K^+K^-$ via $ψ(2S)\rightarrow π^+π^-J/ψ$. The branching fraction of $J/ψ\rightarrow K^+K^-$ is determined to be $\mathcal{B}_{K^+K^-}=(3.072\pm 0.023({\rm stat.})\pm 0.050({\rm syst.}))\times 10^{-4}$, which is consistent with previous measurements but with significantly improved precision.

hep-ex↗

arXiv2024

First study of antihyperon-nucleon scattering $\barΛp\rightarrow\barΛp$ and measurement of $Λp\rightarrowΛp$ cross section

Using $(10.087\pm0.044)\times10^{9}$ $J/ψ$ events collected with the BESIII detector at the BEPCII storage ring, the processes $Λp\rightarrowΛp$ and $\barΛp\rightarrow\barΛp$ are studied, where the $Λ/\barΛ$ baryons are produced in the process $J/ψ\rightarrowΛ\barΛ$ and the protons are the hydrogen nuclei in the cooling oil of the beam pipe. Clear signals are observed for the two reactions. The cross sections in $-0.9\leq\rm{cos}θ_{Λ/\barΛ}\leq0.9$ are measured to be $σ(Λp\rightarrowΛp)=(12.2\pm1.6_{\rm{stat}}\pm1.1_{\rm{sys}})$ mb and $σ(\barΛ p\rightarrow\barΛ p)=(17.5\pm2.1_{\rm{stat}}\pm1.6_{\rm{sys}})$ mb at the $Λ/\barΛ$ momentum of $1.074$ GeV/$c$ within a range of $\pm0.017$ GeV/$c$, where the $θ_{Λ/\barΛ}$ are the scattering angles of the $Λ/\barΛ$ in the $Λp/\barΛp$ rest frames. Furthermore, the differential cross sections of the two reactions are also measured, where there is a slight tendency of forward scattering for $Λp\rightarrowΛp$, and a strong forward peak for $\barΛp\rightarrow\barΛp$. We present an approach to extract the total elastic cross sections by extrapolation. The study of $\barΛp\rightarrow\barΛp$ represents the first study of antihyperon-nucleon scattering, and these new measurements will serve as important inputs for the theoretical understanding of the (anti)hyperon-nucleon interaction.

hep-ex↗

arXiv2024

Measurement of forward charged hadron flow harmonics in peripheral PbPb collisions at $\sqrt{s_{NN}}=5.02$ TeV with the LHCb detector

Flow harmonic coefficients, $v_n$, which are the key to studying the hydrodynamics of the quark-gluon plasma (QGP) created in heavy-ion collisions, have been measured in various collision systems and kinematic regions and using various particle species. The study of flow harmonics in a wide pseudorapidity range is particularly valuable to understand the temperature dependence of the shear viscosity to entropy density ratio of the QGP. This paper presents the first LHCb results of the second- and the third-order flow harmonic coefficients of charged hadrons as a function of transverse momentum in the forward region, corresponding to pseudorapidities between 2.0 and 4.9, using the data collected from PbPb collisions in 2018 at a center-of-mass energy of $5.02$ TeV. The coefficients measured using the two-particle angular correlation analysis method are smaller than the central-pseudorapidity measurements at ALICE and ATLAS from the same collision system but share similar features.

nucl-ex↗

arXiv2024

Observation of the $B_c^+ \to J/ψπ^+ π^0$ decay

The first observation of the $B_c^+ \to J/ψπ^+ π^0$ decay is reported with high significance using proton-proton collision data, corresponding to an integrated luminosity of 9fb$^{-1}$, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV. The ratio of its branching fraction relative to the $B_c^+ \to J/ψπ^+$ channel is measured to be $$ \frac{ {\cal{B}}( B_c^+ \to J/ψπ^+π^0 ) } { {\cal{B}}( B_c^+ \to J/ψπ^+ ) } = 2.80 \pm 0.15 \pm 0.11 \pm 0.16 \,, $$ where the first uncertainty is statistical, the second systematic and the third related to imprecise knowledge of the branching fractions for $B^+ \to J/ψK^{*+}$ and $B^+ \to J/ψK^+$ decays, which are used to determine the $π^0$ detection efficiency. The $π^+π^0$ mass spectrum is found to be consistent with the dominance of an intermediate $ρ^+$ contribution in accordance with a model based on QCD factorisation.

hep-ex↗

arXiv2024

Search for the leptonic decays $D^{+}\to e^+ν_e$ and $D^{+}\to μ^+ν_μ$

We present the first search for the leptonic decays $D^{*+}\to e^+ν_e$ and $D^{*+}\to μ^+ν_μ$ by analyzing a data sample of electron-positron collisions recorded with the BESIII detector at center-of-mass energies between 4.178 and 4.226 GeV, corresponding to an integrated luminosity of 6.32~fb$^{-1}$. No significant signal is observed. The upper limits on the branching fractions for $D^{*+}\to e^+ν_e$ and $D^{*+}\to μ^+ν_μ$ are set to be $1.1 \times 10^{-5}$ and $4.3 \times 10^{-6}$ at 90\% confidence level, respectively.

hep-ex↗

arXiv2024

Study of $CP$ violation in $B^0_{(s)} \to D K^{*}(892)^0$ decays with $D \to K π( ππ)$, $ ππ( ππ)$, and $KK$ final states

A measurement of $CP$-violating observables associated with the interference of $B^0\to D^0 K^{*}(892)^0$ and $B^0\to \bar{D}^0 K^*(892)^0$ decay amplitudes is performed in the $D^0 \to K^{\mp}π^{\pm}(π^+π^-),$ $D^0 \to π^+π^-(π^+π^-)$, and $D^0\to K^+K^-$ final states using data collected by the LHCb experiment corresponding to an integrated luminosity of $9$ $\text{fb}^{-1}$. $CP$-violating observables related to the interference of $B^0_s\to D^0 \bar{K}^*(892)^0$ and $B_s^0\to \bar{D}^0 \bar{K}^*(892)^0$ are also measured, but no evidence for interference is found. The $B^0$ observables are used to constrain the parameter space of the CKM angle $γ$ and the hadronic parameters $r_{B^0}^{DK^*}$ and $δ_{B^0}^{DK^*}$ with inputs from other measurements. In a combined analysis, these measurements allow for four solutions in the parameter space, only one of which is consistent with the world average.

hep-ex↗

arXiv2024

Test of lepton flavour universality using $B^0 \to D^{*-}τ^+ν_τ$ decays with hadronic $τ$ channels

The branching fraction $\mathcal{B}(B^0 \to D^{*-}τ^+ν_τ)$ is measured relative to that of the normalization mode $B^0 \to D^{*-}π^+π^-π^+$ using hadronic $τ^+ \to π^+π^-π^+(π^0)\overlineν_τ$ decays in proton-proton collision data at a center-of-mass energy of 13 TeV collected by the LHCb experiment, corresponding to an integrated luminosity of 2 fb$^{-1}$. The measured ratio is $\mathcal{B}(B^0 \to D^{*-}τ^+ν_τ)/\mathcal{B}(B^0 \to D^{*-}π^+π^-π^+) = 1.79 \pm 0.11 \pm 0.11$, where the first uncertainty is statistical and the second is related to systematic effects. Using established branching fractions for the $B^0 \to D^{*-}π^+π^-π^+$ and $B^0 \to D^{*-}μ^+ν_μ$ modes, the lepton universality test, $\mathcal{R}(D^{*-}) \equiv \mathcal{B}(B^0 \to D^{*-}τ^+ν_τ)/\mathcal{B}(B^0 \to D^{*-}μ^+ν_μ)$ is calculated, $$ \mathcal{R}(D^{*-}) = 0.260 \pm 0.015 \pm 0.016 \pm 0.012\, , $$ where the third uncertainty is due to the uncertainties on the external branching fractions. This result is consistent with the Standard Model prediction and with previous measurements.

hep-ex↗

arXiv2024

First Observation of a Three-Resonance Structure in $e^+e^-\rightarrow$Nonopen Charm Hadrons

We report the measurement of the inclusive cross sections for $e^+e^-$$\rightarrow$nOCH (where nOCH denotes non-open charm hadrons) with improved precision at center-of-mass (c.m.) energies from 3.645 to 3.871 GeV. We observe three resonances: $\mathcal R(3760)$, $\mathcal R(3780)$, and $\mathcal R(3810)$ with significances of $8.1σ$, $13.7σ$, and $8.8σ$, respectively. The $\mathcal R(3810)$ state is observed for the first time, while the $\mathcal R(3760)$ and $\mathcal R(3780)$ states are observed for the first time in the nOCH cross sections. Two sets of resonance parameters describe the energy-dependent line shape of the cross sections well. In set I [set II], the $\mathcal R(3810)$ state has mass $(3805.7 \pm 1.1 \pm 2.7)$ [$(3805.7 \pm 1.1 \pm 2.7)$] MeV/$c^2$, total width $(11.6 \pm 2.9 \pm 1.9)$ [$(11.5 \pm 2.8 \pm 1.9)$] MeV, and an electronic width multiplied by the nOCH decay branching fraction of $(10.9\pm 3.8\pm 2.5)$ [$(11.0\pm 3.4\pm 2.5)$] eV. In addition, we measure the branching fractions ${\mathcal B}[{\mathcal R}(3760)$$\rightarrow$nOCH$]=(25.2 \pm 16.1 \pm 30.4)\% [(6.4 \pm 4.8 \pm 7.7)\%]$ and ${\mathcal B}[\mathcal R(3780)$$\rightarrow$nOCH$]=(12.3 \pm 6.6 \pm 8.3)\% [(10.4 \pm 4.8 \pm 7.0)\%]$ for the first time. The $\mathcal R(3760)$ state can be interpreted as an open-charm (OC) molecular state, but containing a simple four-quark state component. The $\mathcal R(3810)$ state can be interpreted as a hadrocharmonium state.

hep-ex↗

arXiv2024

Measurement of the ${e}^{+}{e}^{-}\to p \bar{p}π^{0}$ cross section at $\sqrt{s}=2.1000-3.0800$ GeV

The process $e^{+}e^{-}\to p\bar{p}π^{0}$ is studied at 20 center-of-mass energies ranging from 2.1000 to 3.0800 GeV using 636.8 pb$^{-1}$ of data collected with the BESIII detector operating at the BEPCII collider. The Born cross sections for $e^{+}e^{-}\to p\bar{p}π^{0}$ are measured with high precision. Since the lowest center-of-mass energy, 2.1000 GeV, is less than 90 MeV above the $p\bar{p}π^0$ energy threshold, we can probe the threshold behavior for this reaction. However, no anomalous threshold enhancement is found in the cross sections for $e^{+}e^{-}\to p\bar{p}π^{0}$.

hep-ex↗

arXiv2024

Measurement of the absolute branching fraction of the three-body decay $Λ_{c}^+ \to Ξ^{0}K^{+}π^{0}$ and search for $Λ_{c}^+ \to nK^+π^0$, $Σ^{0}K^{+}π^{0}$ and $ΛK^{+}π^{0}$

The Cabbibo-favored decay $Λ_{c}^+ \to Ξ^{0}K^{+}π^{0}$ is studied for the first time using 6.1 fb$^{-1}$ of $e^+e^-$ collision data at center-of-mass energies between 4.600 and 4.840 GeV, collected with the BESIII detector at the BEPCII collider. With a double-tag method, the branching fraction of the three-body decay $Λ_{c}^+ \to Ξ^{0}K^{+}π^{0}$ is measured to be $(7.79 \pm 1.46 _{\rm} \pm0.71 _{\rm}) \times 10^{ - 3}$, where the first and second uncertainties are statistical and systematic, respectively. The branching fraction of the two-body decay $Λ_{c}^+ \to Ξ(1530)^{0}K^+$ is $(5.99\pm1.04\pm0.29)\times10^{-3}$, which is consistent with the previous result of $(5.02\pm0.99\pm0.31)\times 10^{-3}$. In addition, the upper limit on the branching fraction of the doubly Cabbibo-suppressed decay $Λ_{c}^+ \to nK^+π^0$ is $7.1 \times 10^{-4}$ at the 90$\%$ confidence level. The upper limits on the branching fractions of $Λ_{c}^+ \to Σ^{0}K^{+}π^{0}$ and $ΛK^{+}π^{0}$ are also determined to be $1.8\times 10^{-3}$ and $ 2.0 \times 10^{-3}$, respectively.

hep-ex↗

arXiv2024

Observation of the Singly Cabibbo-Suppressed Decay $Λ_{c}^{+}\to Σ^{-}K^{+}π^{+}$

The singly Cabibbo-suppressed decay $Λ_{c}^{+}\to Σ^{-}K^{+}π^{+}$ is observed for the first time with a statistical significance of $6.4σ$ by using 4.5 fb$^{-1}$ of $e^+e^-$ collision data collected at center-of-mass energies between 4.600 and 4.699 GeV with the BESIII detector at BEPCII. The absolute branching fraction of $Λ_{c}^{+}\to Σ^{-}K^{+}π^{+}$ is measured to be $(3.8\pm1.3_{\rm stat}\pm0.2_{\rm syst})\times 10^{-4}$ in a model-independent approach. This is the first observation of a Cabibbo-suppressed $Λ_{c}^{+}$ decay involving $Σ^-$ in the final state. The ratio of branching fractions between $Λ_{c}^{+}\to Σ^{-}K^{+}π^{+}$ and the Cabibbo-favored decay $Λ_{c}^{+}\to Σ^- π^+π^+$ is calculated to be $(0.4 \pm 0.1)s_{c}^{2}$, where $s_{c} \equiv \sinθ_c = 0.2248$ with $θ_c$ the Cabibbo mixing angle. This ratio significantly deviates from $1.0s_{c}^{2}$ and provides important information for the understanding of nonfactorization contributions in $Λ_{c}^{+}$ decays.

hep-ex↗

arXiv2024

Measurements of Born Cross Sections for $e^+e^-\to Λ_{c}^+ \barΛ_{c}(2595)^- + {\rm c.c.}$ and $e^+e^-\to Λ_{c}^+ \barΛ_{c}(2625)^- + {\rm c.c.}$ at $\sqrt{s}=$4918.0 and 4950.9 MeV

Using $e^+e^-$ collision data collected with the BESIII detector operating at the BEPCII collider, the Born cross sections of $e^+e^-\to Λ_{c}^+ \barΛ_{c}(2595)^- + \rm{c.c.}$ and $e^+e^-\to Λ_{c}^+ \barΛ_{c}(2625)^- + \rm{c.c.}$ are measured for the first time at center-of-mass energies of $\sqrt{s}=4918.0$ and 4950.9 MeV. Non-zero cross sections are observed very close to the production threshold. The measured Born cross sections of $e^+e^-\to Λ_{c}^+ \barΛ_{c}(2625)^- + \rm{c.c.}$ are about $2\sim3$ times greater than those of $e^+e^-\to Λ_{c}^+ \barΛ_{c}(2595)^- + \rm{c.c.}$, thereby indicating that the exotic structure potentially exists in the excited charmed baryons. The Born cross sections are $15.6\pm3.1\pm0.9$ pb and $29.4\pm3.7\pm2.7$ pb for $e^+e^-\to Λ_{c}^+ \barΛ_{c}(2595)^- + \rm{c.c.}$, and are $43.4\pm4.0\pm4.1$ pb and $76.8\pm6.5\pm4.2$ pb for $e^+e^-\to Λ_{c}^+ \barΛ_{c}(2625)^- +\rm{c.c.}$ at $\sqrt s=4918.0$ and 4950.9 MeV, respectively. Based on the polar angle distributions of the $\barΛ_{c}(2625)^-$ and $Λ_{c}(2625)^+$, the form-factor ratios $\sqrt{|G_{E}|^2 + 3|G_{M}|^2}/|G_{C}|$ are determined for $e^+e^-\to Λ_{c}^+ \barΛ_{c}(2625)^- + \rm{c.c.}$ for the first time, which are $5.95\pm4.07\pm0.15$ and $0.94\pm0.32\pm0.02$ at $\sqrt s=4918.0$ and 4950.9 MeV, respectively. All of these first uncertainties are statistical and second systematic.

hep-ex↗

arXiv2024

Measurement of Born cross section of $e^{+}e^{-}\rightarrowΣ^{+}\barΣ^{-}$ at center-of-mass energies between 3.510 and 4.951 GeV

Using 24.1 fb$^{-1}$ of $e^{+}e^{-}$ collision data collected with the BESIII detector at the BEPCII collider, the Born cross sections and effective form factors of the $e^{+}e^{-}\rightarrowΣ^{+}\barΣ^{-}$ reaction are measured. The measurements are performed at center-of-mass energies ranging from 3.510 to 4.951 GeV. No significant evidence for the decay of the charmonium(-like) states, $ψ(3770)$, $ψ(4040)$, $ψ(4160)$, $Y(4230)$, $Y(4360)$, $ψ(4415)$, and $Y(4660)$, into a $Σ^{+}\barΣ^{-}$ final state is observed. Consequently, upper limits for the products of the branching fractions and the electronic partial widths at the 90% confidence level are reported for these decays.

hep-ex↗