arXiv subjects

M. Greco

Publications and source records attributed to M. Greco.

At least 91 records · Page 5Linked to original sources

arXiv2021

Cross Section Measurement of $e^+e^- \rightarrow π^+π^-ψ(3686)$ from $\sqrt{s}=4.0076$~GeV to 4.6984~GeV

Using data samples with a total integrated luminosity of $20.1~\rm fb^{-1}$ collected by the BESIII detector operating at the BEPCII collider, the cross section of the process $e^+e^- \rightarrow π^+π^-ψ(3686)$ is measured at center-of-mass energies between 4.0076 and 4.6984 GeV. The measured cross section is consistent with previous results, but with much improved precision. A fit to the measured energy-dependent cross section, which includes three Breit-Wigner functions and a non-resonant contribution, confirms the existence of the charmonium-like states $Y(4220)$, $Y(4390)$, and $Y(4660)$. This is the first observation of the $Y(4660)$ at the BESIII experiment.

hep-ex↗

arXiv2021

Study of the Decay $D^{+}_{s}\rightarrow π^{+}π^{+}π^{-}η$ and Observation of the W-annihilation Decay $D^{+}_{s}\rightarrow a_0(980)^+ρ^0$

The decay $D^{+}_{s}\rightarrow π^{+}π^{+}π^{-}η$ is observed for the first time, using $e^+e^-$ collision data corresponding to an integrated luminosity of 6.32 fb$^{-1}$, collected by the BESIII detector at center-of-mass energies between 4.178 and 4.226 GeV. The absolute branching fraction for this decay is measured to be $\mathcal{B}(D^+_s \to π^+ π^+ π^- η) = (3.12\pm0.13_{\rm stat.}\pm0.09_{\rm syst.})$%. The first amplitude analysis of this decay reveals the sub-structures in $D^{+}_{s}\rightarrow π^{+}π^{+}π^{-}η$ and determines the relative fractions and the phases among these sub-structures. The dominant intermediate process is $D^{+}_{s}\rightarrow a_1(1260)^+ η, a_1(1260)^+ \rightarrow ρ(770)^0π^+$ with a branching fraction of $(1.73 \pm 0.14_{\rm stat.} \pm 0.08_{\rm syst.})$%. We also observe the W-annihilation process $D^{+}_{s}\rightarrow a_0(980)^+ρ(770)^0$, $a_0(980)^+ \to π^+ η$ with a branching fraction of $(0.21\pm0.08_{\rm stat.}\pm0.05_{\rm syst.})$%, which is larger than the branching fractions of other measured pure W-annihilation decays by one order of magnitude.

hep-ex↗

arXiv2021

Amplitude analysis and branching fraction measurement of the decay $D_{s}^{+} \to π^{+}π^{0}π^{0}$

Using a data set corresponding to an integrated luminosity of 6.32~$\rm fb^{-1}$ recorded by the BESIII detector at center-of-mass energies between 4.178 and 4.226~GeV, an amplitude analysis of the decay $D_{s}^{+} \to π^{+}π^{0}π^{0}$ is performed, and the relative fractions and phases of different intermediate processes are determined. The absolute branching fraction of the decay $D_{s}^{+} \to π^{+}π^{0}π^{0}$ is measured to be $(0.50\pm 0.04_{\text{stat}}\pm 0.02_{\text{syst}})\%$. The absolute branching fraction of the intermediate process $D_{s}^{+} \to f_0(980)π^{+}, f_0(980)\toπ^{0}π^{0}$ is determined to be $(0.21\pm 0.03_{\text{stat}}\pm 0.03_{\text{syst}})\%$.

hep-ex↗

arXiv2021

Measurement of the absolute branching fractions for purely leptonic $D_s^+$ decays

We report new measurements of the branching fraction $\cal B(D_s^+\to \ell^+ν)$, where $\ell^+$ is either $μ^+$ or $τ^+(\toπ^+\barν_τ)$, based on $6.32$ fb$^{-1}$ of electron-positron annihilation data collected by the BESIII experiment at six center-of-mass energy points between $4.178$ and $4.226$ GeV. Simultaneously floating the $D_s^+\toμ^+ν_μ$ and $D_s^+\toτ^+ν_τ$ components yields $\cal B(D_s^+\to τ^+ν_τ) = (5.21\pm0.25\pm0.17)\times10^{-2}$, $\cal B(D_s^+\to μ^+ν_μ) = (5.35\pm0.13\pm0.16)\times10^{-3}$, and the ratio of decay widths $R=\frac{Γ(D_s^+\to τ^+ν_τ)}{Γ(D_s^+\to μ^+ν_μ)} = 9.73^{+0.61}_{-0.58}\pm 0.36$, where the first uncertainties are statistical and the second systematic. No evidence of ${\it CP}$ asymmetry is observed in the decay rates $D_s^\pm\toμ^\pmν_μ$ and $D_s^\pm\toτ^\pmν_τ$: $A_{\it CP}(μ^\pmν) = (-1.2\pm2.5\pm1.0)\%$ and $A_{\it CP}(τ^\pmν) = (+2.9\pm4.8\pm1.0)\%$. Constraining our measurement to the Standard Model expectation of lepton universality ($R=9.75$), we find the more precise results $\cal B(D_s^+\to τ^+ν_τ) = (5.22\pm0.10\pm 0.14)\times10^{-2}$ and $A_{\it CP}(τ^\pmν_τ) = (-0.1\pm1.9\pm1.0)\%$. Combining our results with inputs external to our analysis, we determine the $c\to \bar{s}$ quark mixing matrix element, $D_s^+$ decay constant, and ratio of the decay constants to be $|V_{cs}| = 0.973\pm0.009\pm0.014$, $f_{D^+_s} = 249.9\pm2.4\pm3.5~\text{MeV}$, and $f_{D^+_s}/f_{D^+} = 1.232\pm0.035$, respectively.

hep-ex↗

arXiv2021

Search for the hyperon semileptonic decay $Ξ^{-} \rightarrow Ξ^{0} e^{-} \bar{ν_{e}}$

Using $(10.087\pm0.044)\times10^{9}$ $J/ψ$ events collected by the BESIII detector at the BEPCII collider, we search for the hyperon semileptonic decay $Ξ^{-} \rightarrow Ξ^{0} e^{-} \barν_{e}$. No significant signal is observed and the upper limit on the branching fraction $\mathcal B(Ξ^{-} \rightarrow Ξ^{0} e^{-} \barν_{e})$ is set to be $2.59\times10^{-4}$ at 90 % confidence level. This result is one order of magnitude more strict than the previous best limit.

hep-ex↗

arXiv2021

Determination of the absolute branching fractions of $D^0\to K^-e^+ν_e$ and $D^+\to \bar K^0 e^+ν_e$

Using 2.93 fb$^{-1}$ of $e^+e^-$ collision data collected with the BESIII detector at a center-of-mass energy of 3.773 GeV, we measure the absolute branching fractions of the decays $D^0\to K^-e^+ν_e$ and $D^+\to \bar K^0 e^+ν_e$ to be $(3.567\pm0.031_{\rm stat}\pm 0.025_{\rm syst})\%$ and $(8.68\pm0.14_{\rm stat}\pm 0.16_{\rm syst})\%$, respectively. Starting with the process $e^+e^-\to D\bar{D}$, a new reconstruction method is employed to select events that contain candidates for both $D\to \bar Ke^+ν_e$ and $\bar D\to Ke^-\bar ν_e$ decays. The branching fractions reported in this work are consistent within uncertainties with previous BESIII measurements that selected events containing $D\to \bar Ke^+ν_e$ and hadronic $\bar D$ decays. Combining our results with the lifetimes of the $D^0$ and $D^+$ mesons and the previous BESIII measurements leads to a ratio of the two decay partial widths of $\frac{\bar Γ_{D^0\to K^{-}e^+ν_{e}}}{\bar Γ_{D^{+}\to \bar K^{0}e^+ν_{e}}}=1.039\pm0.021$. This ratio supports isospin symmetry in the $D^0\to K^-e^+ν_e$ and $D^+\to \bar K^0 e^+ν_e$ decays within $1.9σ$.

hep-ex↗

arXiv2021

Observation of $ψ(3686)\toΞ(1530)^{0}\barΞ(1530)^{0}$ and $Ξ(1530)^{0}\barΞ^0$

Using $(448.1\pm2.9)\times 10^{6}$ $ψ(3686)$ events collected with the BESIII detector and a single-baryon tagging technique, we present the first observation of the decays $ψ(3686)\toΞ(1530)^{0}\barΞ(1530)^{0}$ and $Ξ(1530)^{0}\barΞ^0$. The branching fractions are measured to be ${\cal{B}}(ψ(3686)\toΞ(1530)^{0}\barΞ(1530)^{0}) = (6.77\pm0.14\pm0.39)\times10^{-5}$ and ${\cal{B}}(ψ(3686)\toΞ(1530)^{0}\barΞ^{0}) = (0.53\pm0.04\pm0.03)\times10^{-5}$. Here, the first and second uncertainties are statistical and systematic, respectively. In addition, the parameter associated with the angular distribution for the decay $ψ(3686)\toΞ(1530)^{0}\barΞ(1530)^0$ is determined to be $α= 0.32\pm0.19\pm0.07$, in agreement with theoretical predictions within one standard deviation.

hep-ex↗

arXiv2021

Measurement of the inclusive branching fraction for $ψ(3686)\rightarrow K_{S}^{0} + \text{anything}$

Using 5.9~pb$^{-1}$ of $e^+e^-$ annihilation data collected at center-of-mass energies from 3.640 to 3.701 GeV with the BESIII detector at the BEPCII Collider, we measure the observed cross sections of $e^+e^-\rightarrow K_{S}^{0} X$ (where $X= \text{anything}$). From a fit to these observed cross sections with the sum of continuum and $ψ(3686)$ and $J/ψ$ Breit-Wigner functions and considering initial state radiation and the BEPCII beam energy spread, we obtain for the first time the product of $ψ(3686)$ leptonic width and inclusive decay branching fraction $Γ^{ee}_{ψ(3686)}\mathcal B(ψ(3686)\rightarrow K_{S}^{0} X) = (373.8 \pm 6.7 \pm 20.0)$ eV, and assuming $Γ^{ee}_{ψ(3686)}$ is $(2.33 \pm 0.04)$ keV from PDG value, we measure $\mathcal B(ψ(3686)\rightarrow K_{S}^{0} X) = (16.04 \pm 0.29 \pm 0.90)\%$, where the first uncertainty is statistical and the second is systematic.

hep-ex↗

arXiv2021

Measurements of the center-of-mass energies of $e^{+}e^{-}$ collisions at BESIII

During the 2016-17 and 2018-19 running periods, the BESIII experiment collected 7.5~fb$^{-1}$ of $e^+e^-$ collision data at center-of-mass energies ranging from 4.13 to 4.44 GeV. These data samples are primarily used for the study of excited charmonium and charmoniumlike states. By analyzing the di-muon process $e^{+}e^{-} \to (γ_{\rm ISR/FSR}) μ^{+}μ^{-}$, we measure the center-of-mass energies of the data samples with a precision of 0.6 MeV. Through a run-by-run study, we find that the center-of-mass energies were stable throughout most of the data-taking period.

hep-ex↗

arXiv2021

Observation of a near-threshold enhancement in the $Λ\barΛ$ mass spectrum from $e^+e^-\toϕΛ\barΛ$ at $\sqrt{s}$ from 3.51 to 4.60 GeV

The process $e^+ e^- \to ϕΛ\barΛ$ is studied using data samples collected with the BESIII detector at the BEPCII collider at center-of-mass energies $\sqrt{s}$ ranging from $3.51$ to $4.60~{\rm GeV}$ . An intermediate resonance structure is observed near the threshold of $Λ\barΛ$. It has a mass of $(2262 \pm 4 \pm 28)~{\rm{MeV}}/c^{2}$ and a width of $(72 \pm 5 \pm 43)~\rm{MeV}$, where the quoted uncertainties are statistical and systematic, respectively. The $J^{PC}$ quantum numbers of $0^{-+}$ and $0^{++}$ are rejected, while other $J^{PC}$ hypotheses are possible, according to the helicity angle study. The energy-dependent cross section of the $e^+ e^- \to ϕΛ\barΛ$ process is measured for the first time in this energy region, and contributions from excited $ψ$ states and vector charmonium-like $Y$-states are investigated.

hep-ex↗

arXiv2021

Observation of $D^0\to K_1(1270)^- e^+ν_e$

Using 2.93 fb$^{-1}$ of $e^+e^-$ collision data taken with the BESIII detector at a center-of-mass energy of 3.773 $\rm \,GeV$, the observation of the $D^0\to K_1(1270)^- e^+ν_e$ semileptonic decay is presented. The statistical significance of the decay $D^0\to K_1(1270)^- e^+ν_e$ is greater than $10σ$. The branching fraction of $D^0\to K_1(1270)^- e^+ν_e$ is measured to be $(1.09\pm0.13^{+0.09}_{-0.16} \pm 0.12)\times10^{-3}$. Here, the first uncertainty is statistical, the second is systematic, and the third originates from the assumed branching fraction of $K_1(1270)^- \rightarrow K^-π^+π^-$. The fraction of longitudinal polarization in $D^0\to K_1(1270)^- e^+ν_e$ is determined for the first time to be $0.50\pm0.19_{\rm stat}\pm0.08_{\rm syst}$.

hep-ex↗

arXiv2021

The CGEM-IT readout chain

An innovative Cylindrical Gas Electron Multiplier (CGEM) detector is under construction for the upgrade of the inner tracker of the BESIII experiment. A novel system has been worked out for the readout of the CGEM detector, including a new ASIC, dubbed TIGER -Torino Integrated GEM Electronics for Readout, designed for the amplification and digitization of the CGEM output signals. The data output by TIGER are collected and processed by a first FPGA-based module, GEM Read Out Card, in charge of configuration and control of the front-end ASICs. A second FPGA-based module, named GEM Data Concentrator, builds the trigger selected event packets containing the data and stores them via the main BESIII data acquisition system. The design of the electronics chain, including the power and signal distribution, will be presented together with its performance.

physics.ins-det↗

arXiv2021

Measurement of the branching fraction of leptonic decay $D_s^+\toτ^+ν_τ$ via $τ^+\toπ^+π^0\bar ν_τ$

By analyzing $6.32~\mathrm{fb}^{-1}$ of $e^+e^-$ annihilation data collected at the center-of-mass energies between 4.178 and 4.226\,GeV with the BESIII detector, we determine the branching fraction of the leptonic decay $D_s^+\toτ^+ν_τ$ with $τ^+\toπ^+π^0\bar ν_τ$, to be $\mathcal{B}_{D_s^+\toτ^+ν_τ}=(5.29\pm0.25_{\rm stat}\pm0.20_{\rm syst})\%$. We estimate the product of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cs}|$ and the $D_s^+$ decay constant $f_{D^+_s}$ to be $f_{D_s^+}|V_{cs}|=(244.8\pm5.8_{\rm stat}\pm4.8_{\rm syst})~\mathrm{MeV}$ using the known values of the $τ^+$ and $D_s^+$ masses as well as the $D_s^+$ lifetime, together with our branching fraction measurement. Combining with the value of $|V_{cs}|$ obtained from a global fit in the standard model and $f_{D_s^+}$ from lattice quantum chromodynamics, we obtain $f_{D_s^+}=(251.6\pm5.9_{\rm stat}\pm4.9_{\rm syst})$\,MeV and $|V_{cs}| = 0.980\pm0.023_{\rm stat}\pm0.019_{\rm syst}$.

hep-ex↗

arXiv2021

Measurement of cross section for $e^{+}e^{-}\rightarrowΞ^{0}\barΞ^{0}$ near threshold

Using $e^+e^-$ collision data at ten center-of-mass energies between 2.644 and 3.080 GeV collected with the BESIII detector at BEPCII and corresponding to an integrated luminosity of about 500 pb$^{-1}$, we measure the cross sections and effective form factors for the process $e^{+}e^{-}\rightarrowΞ^{0}\barΞ^{0}$ utilizing a single-tag method. A fit to the cross section of $e^{+}e^{-}\rightarrowΞ^{0}\barΞ^{0}$ with a pQCD-driven power function is performed, from which no significant resonance or threshold enhancement is observed. In addition, the ratio of cross sections for the processes $e^{+}e^{-}\rightarrowΞ^{-}\barΞ^{+}$ and $Ξ^{0}\barΞ^{0}$ is calculated using recent BESIII measurement and is found to be compatible with expectation from isospin symmetry.

hep-ex↗

arXiv2021

Measurements of Born Cross Sections of $e^+e^-\to D_s^{*+} D_{sJ}^{-} +c.c.$

The Born cross sections are measured for the first time for the processes $e^+e^-\to D_s^{*+}D_{s0}^*(2317)^- +c.c.$ and $e^+e^-\to D_s^{*+}D_{s1}(2460)^- +c.c.$ at the center-of-mass energy $\sqrt{s}=$ 4.600~GeV, 4.612~GeV, 4.626~GeV, 4.640~GeV, 4.660~GeV, 4.68~GeV, and 4.700~GeV, and for $e^+e^-\to D_s^{*+}D_{s1}(2536)^- +c.c.$ at $\sqrt{s}=$ 4.660~GeV, 4.680~GeV, and 4.700~GeV, using data samples collected with the BESIII detector at the BEPCII collider. No structures are observed in cross-section distributions for any of the processes.

hep-ex↗

arXiv2021

Amplitude analysis and branching fraction measurement of $D_{s}^{+} \rightarrow K^{+}K^{-}π^{+}$

We report an amplitude analysis and branching fraction measurement of $D_{s}^{+} \rightarrow K^{+}K^{-}π^{+}$ decay using a data sample of 3.19 $\rm fb^{-1}$ recorded with BESIII detector at a center-of-mass energy of 4.178 GeV. We perform a model-independent partial wave analysis in the low $K^{+}K^{-}$ mass region to determine the $K^{+}K^{-}$ S-wave lineshape, followed by an amplitude analysis of our very pure high-statistics sample. The amplitude analysis provides an accurate determination of the detection efficiency allowing us to measure the branching fraction ${\cal B}(D_{s}^{+} \rightarrow K^{+}K^{-}π^{+}) = (5.47\pm0.08_{\rm stat}\pm0.13_{\rm sys})\%$.

hep-ex↗

arXiv2021

Study of the decay $D^+\to K^*(892)^+ K_S^0$ in $D^+\to K^+ K_S^0 π^0$

Based on an $e^{+}e^{-}$ collision data sample corresponding to an integrated luminosity of 2.93 $\mathrm{fb}^{-1}$ collected with the BESIII detector at $\sqrt{s}=3.773 \mathrm{GeV}$, the first amplitude analysis of the singly Cabibbo-suppressed decay $D^{+}\to K^+ K_S^0 π^0$ is performed. From the amplitude analysis, the $K^*(892)^+ K_S^0$ component is found to be dominant with a fraction of $(57.1\pm2.6\pm4.2)\%$, where the first uncertainty is statistical and the second systematic. In combination with the absolute branching fraction $\mathcal{B}(D^+\to K^+ K_S^0 π^0)$ measured by BESIII, we obtain $\mathcal{B}(D^+\to K^*(892)^+ K_S^0)=(8.69\pm0.40\pm0.64\pm0.51)\times10^{-3}$, where the third uncertainty is due to the branching fraction $\mathcal{B}(D^+\to K^+ K_S^0 π^0)$. The precision of this result is significantly improved compared to the previous measurement.

hep-ex↗

arXiv2021

First Measurement of the Absolute Branching Fraction of $Λ\to p μ^- \barν_μ$

The absolute branching fraction of $Λ\to p μ^- \barν_μ$ is reported for the first time based on an $e^+e^-$ annihilation sample of ten billion $J/ψ$ events collected with the BESIII detector at $\sqrt{s}=3.097$ GeV. The branching fraction is determined to be ${\mathcal B}(Λ\to pμ^- \barν_μ) = [1.48\pm0.21(\rm stat) \pm 0.08(\rm syst)]\times 10^{-4}$, which is a significant improvement in precision over the previous indirect measurements. Combining this result with the world average of ${\mathcal B}(Λ\to p e^- \barν_{e})$, we obtain the ratio, $\frac{Γ(Λ\to p μ^- \barν_μ)}{Γ(Λ\to p e^- \barν_{e})}$, to be $0.178 \pm 0.028$, which agrees with the standard model prediction assuming lepton flavor universality. The asymmetry of the branching fractions of $Λ\to p μ^- \barν_μ$ and $\barΛ \to \bar{p} μ^+ ν_μ$ is also determined, and no evidence for $CP$ violation is found.

hep-ex↗