arXiv subjects

L. Fava

Publications and source records attributed to L. Fava.

At least 559 records · Page 31Linked to original sources

arXiv2020

Measurement of {\boldmath $J/ψ\toΞ(1530)^{-}\barΞ^{+}$} and evidence for the radiative decay {\boldmath $Ξ(1530)^{-}\toγΞ^-$}

The SU(3)-flavor violating decay $J/ψ\toΞ(1530)^{-}\barΞ^{+}+c.c.$ is studied using $(1310.6\pm7.0)\times 10^{6} ~J/ψ$ events collected with the BESIII detector at BEPCII and the branching fraction is measured to be ${\cal{B}}(J/ψ\toΞ(1530)^{-}\barΞ^{+}+c.c.)=(3.17\pm0.02_{\rm stat.}\pm0.08_{\rm syst.})\times10^{-4}$. This is consistent with previous measurements with an improved precision. The angular parameter for this decay is measured for the first time and is found to be $α=-0.21\pm0.04_{\rm stat.}\pm0.06_{\rm syst.}$. In addition, we report evidence for the radiative decay $Ξ(1530)^{-}\toγΞ^- $ with a significance of 3.9$σ$, including the systematic uncertainties. The 90\% confidence level upper limit on the branching fraction is determined to be $\mathcal{B}(Ξ(1530)^{-}\toγΞ^- )\leq3.7$\%.

hep-ex↗

arXiv2019

Measurement of the $e^+e^-\toπ^+π^-π^0$ cross section from 0.7 GeV to 3.0 GeV via initial-state radiation

The cross section of the process $e^+e^-\toπ^+π^-π^0$ is measured with a precision of 1.6% to 25% in the energy range between $0.7$ and 3.0 GeV using the Initial State Radiation method. A data set with an integrated luminosity of $2.93$fb$^{-1}$ taken at the center-of-mass energy of $\sqrt{s}=3.773$GeV with the BESIII detector at the BEPCII collider is used. The product branching fractions for $ω$, $ϕ$, $ω(1420)$, and $ω(1650)$ are measured to be $\mathcal{B}(ω\to e^+e^-) \times \mathcal{B}(ω\to π^+π^-π^0)=(6.94\pm0.08\pm0.16) \times 10^{-5}$, $\mathcal{B}(ϕ\to e^+e^-) \times \mathcal{B}(ϕ\toπ^+π^-π^0) = (4.20\pm0.08\pm0.19) \times 10^{-5}$, $\mathcal{B}(ω(1420)\to e^+e^-) \times \mathcal{B}(ω(1420) \to π^+π^-π^0) = (0.84\pm0.09\pm0.09) \times 10^{-6}$, and $\mathcal{B}(ω(1650) \to e^+e^) \times \mathcal{B}(ω(1650)\to π^+π^-π^0) = (1.14\pm0.15\pm0.15)\times10^{-6}$, respectively. The branching fraction $\mathcal{B}(J/ψ\to π^+π^-π^0)$ is measured to be $(2.188 \pm 0.024 \pm 0.024 \pm0.040 (Γ_{ee}^{J/ψ}))\%$, where $Γ_{ee}^{J/ψ}$ is the dileptonic width of $J/ψ$. The first errors are of statistical, the second and third ones of systematic nature.

hep-ex↗

arXiv2019

Observation of the $X(2370)$ and search for the $X(2120)$ in $J/ψ\toγK\bar{K} η'$

Using a sample of $1.31\times10^{9} ~J/ψ$ events collected with the BESIII detector, we perform a study of $J/ψ\toγK\bar{K}η'$. The $X(2370)$ is observed in the $K\bar{K}η'$ invariant-mass distribution with a statistical significance of 8.3$σ$. Its resonance parameters are measured to be $M = 2341.6 \pm 6.5\text{(stat.)} \pm 5.7\text{(syst.)}$~MeV/$c^{2}$ and $Γ= 117 \pm 10 \text{(stat.)} \pm 8 \text{(syst.)}$~MeV. The product branching fractions for $J/ψ\to γX(2370), X(2370) \to K^{+} K^{-}η'$ and $J/ψ\to γX(2370), X(2370) \to K_{S}^{0} K_{S}^{0}η'$ are determined to be $(1.79 \pm 0.23 \text{(stat.)} \pm 0.65 \text{(syst.)}) \times 10^{-5}$ and $(1.18 \pm 0.32\ text{(stat.)} \pm 0.39 \text{(syst.)}) \times 10^{-5}$, respectively. No evident signal for the $X(2120)$ is observed in the $K\bar{K}η'$ invariant-mass distribution. The upper limits for the product branching fractions of $\mathcal{B}(J/ψ\to γX(2120)\toγK^{+} K^{-} η')$ and $\mathcal{B}(J/ψ\toγX(2120)\toγK_{S}^{0} K_{S}^{0} η')$ are determined to be $1.49\times10^{-5}$ and $6.38\times10^{-6}$ at the 90% confidence level, respectively.

hep-ex↗

arXiv2019

Observation of the Semileptonic $D^+$ Transition into an Axial-Vector Meson $\bar K_1(1270)^0$

By analyzing a 2.93~$\rm fb^{-1}$ data sample of $e^+e^-$ collisions, recorded at a center-of-mass energy of 3.773 $\rm \,GeV$ with the BESIII detector operated at the BEPCII collider, we have searched for the semileptonic $D^+$ transition into the axial-vector meson ${\bar{K}}_{1}(1270)^{0}$. The $D^{+} \rightarrow {\bar{K}}_{1}(1270)^{0}e^{+}ν_{e}$ decay is observed for the first time with a statistical significance greater than $10σ$. Its decay branching fraction is determined to be ${\mathcal B}[D^+\to \bar K_1(1270)^0 e^+ν_e]=(2.30\pm0.26\pm 0.18 \pm 0.25)\times10^{-3}$, where the first and second uncertainties are statistical and systematic, respectively, and the third originates from the input branching fraction of ${\bar{K}}_{1}(1270)^{0} \rightarrow K^{-} π^{+} π^{0}$.

hep-ex↗

arXiv2019

Measurement of Branching Fractions of $ψ(3686)\rightarrowϕη^\prime, ϕf_1(1285)$ and $ϕη(1405)$

Using a sample of $448.1\times10^6$ $ψ(3686)$ events collected with the BESIII detector, we perform a study of the decay $ψ(3686) \rightarrow ϕπ^{+}π^{-}η$. The branching fraction of $ψ(3686)\rightarrowϕη^\prime$ is determined to be $(1.51\pm0.16\pm0.12)\times 10^{-5}$, which is consistent with the previous measurement but with significantly improved precision. The resonances $f_{1}(1285)$ and $η(1405)$ are clearly observed in the $π^{+}π^{-}η$ mass spectrum with statistical significances of $18σ$ and $9.7σ$, respectively. The corresponding product branching fractions are measured to be $\mathcal{B}(ψ(3686)\rightarrowϕf_{1}(1285),f_{1}(1285)\rightarrowπ^{+}π^{-}η) =(1.03\pm0.10\pm0.09)\times 10^{-5}$ and $\mathcal{B}(ψ(3686)\rightarrowϕη(1405),η(1405)\rightarrowπ^{+}π^{-}η) =(8.46\pm1.37\pm0.92)\times 10^{-6}$.

hep-ex↗

arXiv2019

Observation of the leptonic decay $D^+ \to τ^+ ν_τ$

We report the first observation of $D^+\toτ^+ν_τ$ with a significance of $5.1σ$. We measure ${\cal B}(D^+\toτ^+ν_τ) = (1.20\pm0.24_{\text{stat.}}\pm0.12_{\text{syst.}})\times10^{-3}$. Taking the world average ${\cal B}(D^+\toμ^+ν_μ) = (3.74\pm0.17)\times10^{-4}$, we obtain $R_{τ/μ} =Γ(D^+\toτ^+ν_τ)/Γ(D^+\toμ^+ν_μ) = 3.21\pm0.64_{\text{stat.}}\pm0.43_{\text{syst.}}$, which is consistent with the Standard Model expectation of lepton flavor universality. Using external inputs, our results give values for the $D^+$ decay constant $f_{D^+}$ and the CKM matrix element $|V_{cd}|$ that are consistent with, but less precise than, other determinations.

hep-ex↗

arXiv2019

Partial-wave analysis of $J/ψ\to K^+K^-π^0$

A partial-wave analysis of the decay $J/ψ\to K^+K^-π^0$ has been made using $(223.7\pm1.4)\times 10^{6}$ $J/ψ$ events collected with the BESIII detector in 2009. The analysis, which is performed within the isobar-model approach, reveals contributions from $K^*_2(1430)^\pm$, $K^*_2(1980)^\pm$ and $K^*_4(2045)^\pm$ decaying to $K^\pmπ^0$. The two latter states are observed in $J/ψ$ decays for the first time. Two resonance signals decaying to $K^+K^-$ are also observed. These contributions can not be reliably identified and their possible interpretations are discussed. The measured branching fraction $B(J/ψ\to K^+K^-π^0)$ of $(2.88\pm0.01\pm0.12)\times10^{-3}$ is more precise than previous results. Branching fractions for the reported contributions are presented as well. The results of the partial-wave analysis differ significantly from those previously obtained by BESII and BABAR.

hep-ex↗

arXiv2019

Observation of the decays $χ_{cJ} \to ϕϕη$

Using a data sample of $(448.1\pm2.9)\times10^{6}$ $ψ(3686)$ decays collected by the BESIII detector at the Beijing Electron Positron Collider (BEPCII), we observe the decays $χ_{cJ}\to ϕϕη~(J=0,~1,~2)$, where the $χ_{cJ}$ are produced via the radiative processes $ψ(3686)\toγχ_{cJ}$. The branching fractions are measured to be $\mathcal B(χ_{c0}\toϕϕη)=(8.41\pm0.74\pm0.62)\times10^{-4}$, $\mathcal B(χ_{c1}\toϕϕη)=(2.96\pm0.43\pm0.22)\times 10^{-4}$, and $\mathcal B(χ_{c2} \to ϕϕη)=(5.33\pm0.52\pm0.39) \times 10^{-4}$, where the first uncertainties are statistical and the second are systematic. We also search for intermediate states in the $ϕϕ$ or $ηϕ$ combinations, but no significant structure is seen due to the limited statistics.

hep-ex↗

arXiv2019

Search for the decay $D_{s}^{+} \to p\bar{p}e^{+}ν_{e}$

Using a $3.19~\mathrm{fb}^{-1}$ data sample collected at the $\sqrt{s}~=~4.178$ GeV with the BESIII detector, we search for the rare decay $D_{s}^{+} \rightarrow p \bar{p} e^{+} ν_{e} $. No significant signal is observed, and an upper limit of $\mathcal{B}(D_{s}^{+} \rightarrow p \bar{p} e^{+} ν_{e}) < 2.0 \times 10^{-4}$ is set at the 90\% confidence level. This measurement is useful input in understanding the baryonic transition of $D_{s}^{+}$ mesons.

hep-ex↗

arXiv2019

Improved measurements of the absolute branching fractions of the inclusive decays $D^{+(0)}\toϕX$

By analyzing 2.93 fb$^{-1}$ of $e^+e^-$ annihilation data taken at the center-of-mass energy $\sqrt s=$ 3.773 GeV with the BESIII detector, we determine the branching fractions of the inclusive decays $D^+\toϕX$ and $D^0\toϕX$ to be $(1.135\pm0.034\pm0.031)\%$ and $(1.091\pm0.027\pm0.035)\%$, respectively, where $X$ denotes any possible particle combination. The first uncertainties are statistical and the second systematic. We also determine the branching fractions of the decays $D\toϕX$ and their charge conjugate modes $\bar{D}\toϕ\bar{X}$ separately for the first time, and no significant CP asymmetry is observed.

hep-ex↗

arXiv2019

Measurement of branching fractions for $D$ meson decaying into $ϕ$ meson and a pseudoscalar meson

The four decay modes $D^{0}\toϕπ^{0}$, $D^{0}\toϕη$, $D^{+}\toϕπ^{+}$, and $D^{+}\toϕK^{+}$ are studied by using a data sample taken at the centre-of-mass energy $\sqrt{s} = 3.773$~GeV~with the BESIII detector, corresponding to an integrated luminosity of 2.93 fb$^{-1}$. The branching fractions of the first three decay modes are measured to be ${\cal B}(D^{0}\toϕπ^{0})=(1.168\pm0.028\pm0.028)\times10^{-3}$, ${\cal B}(D^{0}\toϕη)=(1.81\pm0.46\pm0.06)\times10^{-4}$, and ${\cal B}(D^{+}\toϕπ^{+})=(5.70\pm0.05\pm0.13)\times10^{-3}$, respectively, where the first uncertainties are statistical and the second are systematic. No significant signal is observed of the decay $D^+\toϕ{K^+}$ and the upper limit of its branching fraction is set for the first time, to be $2.1\times10^{-5}$ at the $90\%$ confidence level. The ratio of ${\cal B}(D^0\toϕπ^0)$ to $\cal B(D^+\toϕπ^+)$ is calculated to be $(20.49\pm0.50\pm0.45)\%$, which is consistent with the theoretical prediction based on isospin symmetry between these two decay modes.

hep-ex↗

arXiv2019

Study of the decays $ψ(3686)\rightarrowγχ_{cJ}\rightarrowγ\bar{p}K^{+}Λ+c.c.$ and $ψ(3686)\rightarrow\bar{p}K^{+}Λ+c.c.$

Based on the data sample of $448.1\times10^{6}$ $ψ(3686)$ events collected with the BESIII detector at BEPCII, we present a study of the decays $ψ(3686)\rightarrowγχ_{cJ}\rightarrowγ\bar{p}K^{*+}Λ+c.c.$ and $ψ(3686)\rightarrow\bar{p}K^{*+}Λ+c.c.$. The branching fractions of $χ_{cJ}\rightarrow\bar{p}K^{*+}Λ+c.c.$ ($J$=0, 1, 2) are measured to be $(4.8\pm0.7\pm0.5)\times10^{-4}$, $(5.0\pm0.5\pm0.4)\times10^{-4}$, and $(8.2\pm0.9\pm0.7)\times10^{-4}$, respectively, where the first uncertainties are statistical and the second systematic. The branching fraction of $ψ(3686)\rightarrow\bar{p}K^{*+}Λ+c.c.$ is measured to be $(6.3\pm0.5\pm0.5)\times10^{-5}$. All these decay modes are observed for the first time.

hep-ex↗

arXiv2019

Observation of $ψ(3686)\rightarrowΞ(1530)^{-}\barΞ(1530)^{+}$ and $Ξ(1530)^{-}\barΞ^{+}$

Using 448.1 $\times$ $10^{6}$ $ψ(3686)$ events collected with the BESIII detector at BEPCII, we employ a single-baryon tagging technique to make the first observation of $ψ(3686)\rightarrowΞ(1530)^{-}\barΞ(1530)^{+}$ and $Ξ(1530)^{-}\barΞ^{+}$ decays with a statistical significance of more than 10$σ$ and 5.0$σ$, respectively. The branching fractions are measured to be $\cal{B}$$[ψ(3686)\rightarrowΞ(1530)^{-}\barΞ(1530)^{+}] $ = (11.45 $\pm$ 0.40 $\pm$ 0.59) $\times$ $10^{-5}$ and $\cal{B}$$[ψ(3686)\rightarrowΞ(1530)^{-}\barΞ^{+}]$ = (0.70 $\pm$ 0.11 $\pm$ 0.04) $\times$ $10^{-5}$. The angular distribution parameter for $ψ(3686)\rightarrowΞ(1530)^{-}\barΞ(1530)^{+}$ is determined to be $α$ = 0.40 $\pm$ 0.24 $\pm$ 0.06, which agrees with the theoretical predictions within 1$σ$. The first uncertainties are statistical, and the second systematic.

hep-ex↗

arXiv2019

First observation of the decay $χ_{cJ}\to Σ^{+}\bar{p}K_{S}^{0}+c.c. ~(J = 0, 1, 2)$

Using E1 radiative transitions $ψ(3686) \to γχ_{cJ}$ from a sample of $(448.1 \pm 2.9)\times10^{6}$ $ψ(3686)$ events collected with the BESIII detector, the decays $χ_{cJ}\to Σ^{+}\bar{p}K_{S}^{0}+c.c.~(J = 0, 1, 2)$ are studied. The decay branching fractions are measured to be $\mathcal{B}(χ_{c0}\to Σ^{+}\bar{p}K_{S}^{0}+c.c.) = (3.52 \pm 0.19\pm 0.21)\times10^{-4}$, $\mathcal{B}(χ_{c1}\to Σ^{+}\bar{p}K_{S}^{0}+c.c.) = (1.53 \pm 0.10\pm 0.08)\times10^{-4}$, and $\mathcal{B}(χ_{c2}\to Σ^{+}\bar{p}K_{S}^{0}+c.c.) = (8.25 \pm 0.83 \pm 0.49)\times10^{-5}$, where the first and second uncertainties are the statistical and systematic ones, respectively. No evident intermediate resonances are observed in the studied processes.

hep-ex↗

arXiv2019

Triple GEM performance in magnetic field

Performance of triple GEM prototypes in strong magnetic field has been evaluated bymeans of a muon beam at the H4 line of the SPS test area at CERN. Data have been reconstructedand analyzed offline with two reconstruction methods: the charge centroid and the micro-Time-Projection-Chamber exploiting the charge and the time measurement respectively. A combinationof the two reconstruction methods is capable to guarantee a spatial resolution better than 150μmin magnetic field up to a 1 T.

physics.ins-det↗

arXiv2019

Search for the rare decay $η'\rightarrowπ^{0}π^{0}π^{0}π^{0}$ at BESIII

Based on a sample of 1.31 billion $J/ψ$ events collected with the BESIII detector, we perform a search for the rare decay $η'\rightarrow 4π^{0}$ via $J/ψ\rightarrowγη'$. No significant $η'$ signal is observed in the invariant mass spectrum of 4$π^{0}$. With a Bayesian approach, the upper limit on the branching fraction of $η'\rightarrow 4π^{0}$ is determined to be $\mathcal{B}(η'\rightarrow 4π^{0})$ $< 4.94\times10^{-5}$ at the 90\% confidence level, which is a factor of six smaller than the previous experimental limit.

hep-ex↗

arXiv2019

Evidence for the decays of $Λ^+_{c}\toΣ^+η$ and $Σ^+η^\prime$

We study the hadronic decays of $Λ_{c}^{+}$ to the final states $Σ^{+}η$ and $Σ^+η^\prime$, using an $e^{+}e^{-}$ annihilation data sample of 567 pb$^{-1}$ taken at a center-of-mass energy of 4.6 GeV with the BESIII detector at the BEPCII collider. We find evidence for the decays $Λ_{c}^{+}\rightarrowΣ^{+}η$ and $Σ^+η^\prime$ with statistical significance of $2.5σ$ and $3.2σ$, respectively. Normalizing to the reference decays $Λ_c^+\toΣ^+π^0$ and $Σ^+ω$, we obtain the ratios of the branching fractions $\frac{{\mathcal B}(Λ_c^+\toΣ^+η)}{{\mathcal B}(Λ_c^+\toΣ^+π^0)}$ and $\frac{{\mathcal B}(Λ_c^+\toΣ^+η^\prime)}{{\mathcal B}(Λ_c^+\toΣ^+ω)}$ to be $0.35 \pm 0.16 \pm 0.03$ and $0.86 \pm 0.34 \pm 0.07$, respectively. The upper limits at the 90\% confidence level are set to be $\frac{{\mathcal B}(Λ_c^+\toΣ^+η)}{{\mathcal B}(Λ_c^+\toΣ^+π^0)}<0.58$ and $\frac{{\mathcal B}(Λ_c^+\toΣ^+η^\prime)}{{\mathcal B}(Λ_c^+\toΣ^+ω)}<1.2$. Using BESIII measurements of the branching fractions of the reference decays, we determine $\mathcal B({Λ_{c}^{+}\rightarrowΣ^{+}η})=(0.41\pm0.19\pm0.05)\%$ ($<0.68\%$) and $\mathcal B({Λ_{c}^{+}\rightarrowΣ^{+}η'})=(1.34\pm0.53\pm0.21)\%$ ($<1.9\%$). Here, the first uncertainties are statistical and the second systematic. The obtained branching fraction of $Λ_c^+\toΣ^+η$ is consistent with the previous measurement, and the branching fraction of $Λ_{c}^{+}\rightarrowΣ^{+}η^{\prime}$ is measured for the first time.

hep-ex↗

arXiv2019

Cross section measurements of $e^{+}e^{-} \to K^{+}K^{-}K^{+}K^{-} $ and $ ϕK^{+}K^{-}$ at center-of-mass energies from 2.10 to 3.08 GeV

We measure the Born cross sections of the process $e^{+}e^{-} \to K^{+}K^{-}K^{+}K^{-}$ at center-of-mass (c.m.) energies, $\sqrt{s}$, between 2.100 and 3.080 GeV. The data were collected using the BESIII detector at the BEPCII collider. An enhancement at $\sqrt{s}= 2.232$ GeV is observed, very close to the $e^{+}e^{-} \to Λ\overlineΛ$ production threshold. A similar enhancement at the same c.m. energy is observed in the $e^{+}e^{-} \to ϕK^{+}K^{-}$ cross section. The energy dependence of the $K^{+}K^{-}K^{+}K^{-}$ and $ϕK^{+}K^{-}$ cross sections differs significantly from that of $e^{+}e^{-} \to ϕπ^{+}π^{-}$.

hep-ex↗