arXiv subjects

Y. Gao

Publications and source records attributed to Y. Gao.

At least 253 records · Page 14Linked to original sources

arXiv2018

Search for $h_{c}\rightarrowπ^+π^-J/ψ$ via $ψ(3686)\rightarrow π^0π^+π^-J/ψ$

Using a data sample of $448.1\times10^6$ $ψ(3686)$ events collected with the BESIII detector operating at the BEPCII, we perform search for the hadronic transition $h_c\rightarrowπ^+π^-J/ψ$ via $ψ(3686)\rightarrowπ^0h_c$. No signals of the transition are observed, and the upper limit on the product branching fraction $\mathcal{B}(ψ(3686)\rightarrowπ^0h_c)\mathcal{B}(h_c\rightarrowπ^+π^-J/ψ)$ at the 90% confidence level is determined to be $2.0\times10^{-6}$. This is the most stringent upper limit to date.

hep-ex↗

arXiv2018

Study of the decays $D^+\rightarrowη^{(\prime)} e^+ν_{e}$

The charm semileptonic decays $D^+\toηe^+ν_{e}$ and $D^+\toη'e^+ν_{e}$ are studied with a sample of $e^+e^-$ collision data corresponding to an integrated luminosity of 2.93 fb$^{-1}$ collected at $\sqrt{s}$ = 3.773 GeV with the BESIII detector. We measure the branching fractions for $D^+\toηe^+ν_{e}$ to be $(10.74\pm0.81\pm0.51)\times10^{-4}$, and for $D^+\toη'e^+ν_{e}$ to be $(1.91\pm0.51\pm0.13)\times10^{-4}$, where the uncertainties are statistical and systematic, respectively. In addition, we perform a measurement of the form factor in the decay $D^+\toηe^+ν_{e}$. All the results are consistent with those obtained by the CLEO-c experiment.

hep-ex↗

arXiv2018

Measurement of absolute branching fraction of the inclusive decay $Λ_{c}^{+} \to Λ+ X$

Based on an $e^+e^-$ collision data sample corresponding to an integrated luminosity of 567$\,\rm{pb}^{-1}$ taken at the center-of-mass energy of $\sqrt{s} = 4.6$ GeV with the BESIII detector, we measure the absolute branching fraction of the inclusive decay $Λ_{c}^{+} \to Λ+ X$ to be $\mathcal{B}(Λ_{c}^{+} \to Λ+ X)=(38.2^{+2.8}_{-2.2}\pm0.8)\%$ using the double-tag method, where $X$ refers to any possible final state particles. In addition, we search for direct CP violation in the charge asymmetry of this inclusive decay for the first time, and obtain $\mathcal{A}_{CP} \equiv \frac{\mathcal{B}(Λ_{c}^{+} \to Λ+ X)-\mathcal{B}(\barΛ_{c}^{-} \to \barΛ + X)}{\mathcal{B}(Λ_{c}^{+} \to Λ+ X)+\mathcal{B}(\barΛ_{c}^{-} \to \barΛ + X)} = (2.1^{+7.0}_{-6.6}\pm1.4)\%$, a statistically limited result with no evidence of CP violation.

hep-ex↗

arXiv2018

Search for Baryon and Lepton Number Violation in $J/ψ\toΛ_c^+e^-+c.c.$

Using $1.31\times10^9$ $J/ψ$ events collected by the BESIII detector at the Beijing Electron Positron Collider, we search for the process $J/ψ\toΛ_c^+e^-+c.c.$ for the first time. In this process, both baryon and lepton number conservation is violated. No signal is found and the upper limit on the branching fraction $\mathcal{B}(J/ψ\toΛ_c^+e^-+c.c.)$ is set to be $6.9\times10^{-8}$ at the 90\% Confidence Level.

hep-ex↗

arXiv2018

Observation of the Semileptonic Decay $D^0 \to a_0(980)^- e^+ ν_e$ and Evidence for $D^+ \to a_0(980)^0 e^+ ν_e$

Using an $e^+e^-$ collision data sample of 2.93 fb$^{-1}$ collected at a center-of-mass energy of 3.773 GeV by the BESIII detector at BEPCII, we report the observation of $D^0 \to a_0(980)^- e^+ ν_e$ and evidence for $D^+ \to a_0(980)^0 e^+ ν_e~$ with significances of $6.4σ$ and $2.9σ$, respectively. The absolute branching fractions are determined to be $\mathcal{B}(D^0 \to a_0(980)^- e^+ ν_e)\times\mathcal{B}(a_0(980)^- \to ηπ^-) = (1.33_{-0.29}^{+0.33}({\rm stat})\pm0.09({\rm syst}))\times10^{-4}~$ and $\mathcal{B}(D^+ \to a_0(980)^0 e^+ ν_e)\times\mathcal{B}(a_0(980)^0 \to ηπ^0) = (1.66_{-0.66}^{+0.81}({\rm stat})\pm0.11({\rm syst}))\times10^{-4}~$. An upper limit of $\mathcal{B}(D^+ \to a_0(980)^0 e^+ ν_e)\times\mathcal{B}(a_0(980)^0 \to ηπ^0)<3.0\times10^{-4}~$ is also determined at the $90\%~$ confidence level.

hep-ex↗

arXiv2018

Observation of $e^{+}e^{-} \to ϕχ_{c1}$ and $ϕχ_{c2}$ at $\sqrt{s}$=4.600 GeV

Using a data sample collected with the BESIII detector operating at the BEPCII storage ring at a center-of-mass energy of $\sqrt{s}=4.600$ GeV, we search for the production of $e^{+}e^{-} \to ϕχ_{c0,1,2}$ and the charmonium-like state $Y(4140)$ in the radiative transition $e^{+}e^{-} \to γY(4140)$ with $Y(4140)$ subsequently decaying into $ϕJ/ψ$. The processes $e^{+}e^{-} \to ϕχ_{c1}$ and $ϕχ_{c2}$ are observed for the first time, each with a statistical significance of more than 10σ, and the Born cross sections are measured to be $(4.2^{+1.7}_{-1.0}\pm 0.3)$ pb and $(6.7^{+3.4}_{-1.7}\pm 0.5)$ pb, respectively, where the first uncertainties are statistical and the second systematic. No significant signals are observed for $e^{+}e^{-} \to ϕχ_{c0}$ and $e^{+}e^{-} \to γY(4140)$ and upper limits on the Born cross sections at $90\%$ confidence level are provided at $\sqrt{s}=4.600$ GeV.

hep-ex↗

arXiv2018

Measurements of the Branching Fractions of the Singly-Cabibbo-Suppressed Decays $D^0\toωη$, $η^{(\prime)}π^0$ and $η^{(\prime)}η$

By analyzing a data sample of 2.93 fb$^{-1}$ collected at $\sqrt s=$ 3.773 GeV with the BESIII detector operated at the BEPCII storage rings, we measure the branching fractions ${\mathcal B}(D^0\toωη)=(2.15\pm0.17_{\rm stat.}\pm0.15_{\rm sys.})\times 10^{-3}$, ${\mathcal B}(D^0\toηπ^0)=(0.58\pm0.05_{\rm stat.}\pm0.05_{\rm sys.})\times 10^{-3}$, ${\mathcal B}(D^0\toη^\primeπ^0)=(0.93\pm0.11_{\rm stat.}\pm0.09_{\rm sys.})\times 10^{-3}$, ${\mathcal B}(D^0\toηη)=(2.20\pm0.07_{\rm stat.}\pm0.06_{\rm sys.})\times 10^{-3}$ and ${\mathcal B}(D^0\toη^\primeη)=(0.94\pm0.25_{\rm stat.}\pm0.11_{\rm sys.})\times 10^{-3}$. We note that ${\mathcal B}(D^0\to ωη)$ is measured for the first time and that ${\mathcal B}(D^0\to ηη)$ is measured with much improved precision.

hep-ex↗

arXiv2018

Study of two-photon decays of pseudoscalar mesons via $J/ψ$ radiative decays

Using a sample of $4.48\times10^{8}$ $ψ(3686)$ events collected with the BESIII detector at the BEPCII collider, we study the two-photon decays of the pseudoscalar mesons $π^0$, $η$, $η^\prime$, $η(1405)$, $η(1475)$, $η(1760)$, and $X(1835)$ in $J/ψ$ radiative decays using $ψ(3686)\toπ^{+}π^{-}J/ψ$ events. The $π^0$, $η$ and $η^\prime$ mesons are clearly observed in the two-photon mass spectra, and the branching fractions are determined to be $B(J/ψ\toγπ^{0}\to3γ)=(3.57\pm0.12\pm0.16)\times10^{-5}$, $B(J/ψ\toγη\to3γ)=(4.42\pm0.04\pm0.18)\times10^{-4}$, and $B(J/ψ\toγη'\to3γ)=(1.26\pm0.02\pm0.05)\times10^{-4}$, where the first errors are statistical and the second systematic. No clear signal for $η(1405)$, $η(1475)$, $η(1760)$ or $X(1835)$ is observed in the two-photon mass spectra, and upper limits at the $90\%$ confidence level on the product branching fractions are obtained.

hep-ex↗

arXiv2018

Measurements of absolute branching fractions for $D$ mesons decays into two pseudoscalar mesons

Using a data sample of $e^+e^-$ collision data with an integrated luminosity of 2.93 fb$^{-1}$ taken at the center-of-mass energy $\sqrt s= 3.773$~GeV with the BESIII detector operating at the BEPCII storage rings, we measure the absolute branching fractions of the two-body hadronic decays $D^+\to π^+π^0$, $K^+ π^0$, $π^+ η$, $K^+η$, $π^+η^\prime$, $K^+η^\prime$, $K_S^0 π^+$, $K_S^0 K^+$, and $D^0\to π^+ π^-$, $K^+ K^-$, $K^\mp π^\pm$, $K_S^0 π^0$, $K_S^0 η$, $K_S^0 η^\prime$. Our results are consistent with previous measurements within uncertainties. Among them, the branching fractions for $D^+\toπ^+π^0$, $K^+π^0$, $π^+η$, $π^+η^\prime$, $K_S^0 π^+$, $K_S^0 K^+$ and $D^0 \to K_S^0 π^0$, $K_S^0 η$, $K_S^0 η^\prime$ are determined with improved precision compared to the world average values.

hep-ex↗

arXiv2018

Observation of $e^{+}e^{-} \rightarrow K\bar{K}J/ψ$ at center-of-mass energies from 4.189 to 4.600 GeV

We investigate the process $e^{+}e^{-} \rightarrow K\bar{K}J/ψ$ at center-of-mass energies from 4.189 to 4.600 GeV using 4.7 fb$^{-1}$ of data collected by the BESIII detector at the BEPCII collider. The Born cross sections for the reactions $e^{+}e^{-} \rightarrow K^{+}K^{-}J/ψ$ and $K_{S}^{0} K_{S}^{0} J/ψ$ are measured as a function of center-of-mass energy. The energy dependence of the cross section for $e^{+}e^{-} \rightarrow K^{+}K^{-}J/ψ$ is shown to differ from that for $π^{+}π^{-}J/ψ$ in the region around the $Y(4260)$. In addition, there is evidence for a structure around 4.5 GeV in the $e^{+}e^{-} \rightarrow K^{+}K^{-}J/ψ$ cross section that is not present in $π^{+}π^{-}J/ψ$.

hep-ex↗

arXiv2018

Herschel Spectroscopy of the Taffy Galaxies (UGC 12914/12915 = VV 254): Enhanced [C II] emission in the collisionally-formed bridge

Using the PACS and SPIRE spectrometers on-board Herschel, we obtained observations of the Taffy galaxies (UGC 12914/12915) and bridge. The Taffy system is believed to be the result of a face-on collision between two gas-rich galaxies, in which the stellar disks passed through each other, but the gas was dispersed into a massive H I and molecular bridge between them. Emission is detected and mapped in both galaxies and the bridge in the [C II]157.7 $μ$m and [O I]63.2 $μ$m fine-structure lines. Additionally, SPIRE FTS spectroscopy detects the [C I] $^3$P$_2$$\rightarrow$$^3$P$_1$(809.3 GHz) and [C I] $^3$P$_1$$\rightarrow$$3$P$_0$(492.2 GHz) neutral carbon lines, and weakly detects high-J CO transitions in the bridge. These results indicate that the bridge is composed of a warm multi-phase medium consistent with shock and turbulent heating. Despite low star formation rates in the bridge, the [C II] emission appears to be enhanced, reaching [C II]/FIR ratios of 3.3% in parts of the bridge. Both the [C II] and [O I] lines show broad intrinsic multi-component profiles, similar to those seen in previous CO 1-0 and H I observations. The [C II] emission shares similar line profiles with both the double-peaked H I profiles and shares a high-velocity component with single-peaked CO profiles in the bridge, suggesting that the [C II] emission originates in both the neutral and molecular phases. We show that it is feasible that a combination of turbulently heated H$_2$ and high column-density H I, resulting from the galaxy collision, is responsible for the enhanced [C II] emission.

astro-ph.GA↗

arXiv2018

Measurement of the matrix elements for the decays $η^{\prime}\rightarrowηπ^+π^-$ and $η^{\prime}\rightarrowηπ^0π^0$

Based on a sample of $1.31\times10^9$ $J/ψ$ events collected with the BESIII detector, the matrix elements for the decays $η^{\prime}\toηπ^{+}π^{-}$ and $η^{\prime}\toηπ^{0}π^{0}$ are determined using 351,016 $η^{\prime}\to(η\toγγ)π^+π^-$ and 56,249 $η^{\prime}\to(η\toγγ)π^0π^0$ events with background levels less than 1\%. Two commonly used representations are used to describe the Dalitz plot density. We find that an assumption of a linear amplitude does not describe the data well. A small deviation of the obtained matrix elements between $η^{\prime}\toηπ^{+}π^{-}$ and $η^{\prime}\toηπ^{0}π^{0}$ is probably caused by the mass difference between charged and neutral pions or radiative corrections. No cusp structure in $η^{\prime}\toηπ^{0}π^{0}$ is observed.

hep-ex↗

arXiv2018

Study of $η(1475)$ and $X(1835)$ in radiative $J/ψ$ decays to $γϕ$

The decay $J/ψ\rightarrow γγϕ$ is studied using a sample of $1.31 \times10^{9}$ $J/ψ$ events collected with the BESIII detector. Two structures around 1475 MeV/c$^2$ and 1835 MeV/c$^2$ are observed in the $γϕ$ invariant mass spectrum for the first time. With a fit on the $γϕ$ invariant mass, which takes into account the interference between the two structures, and a simple analysis of the angular distribution, the structure around 1475 MeV/c$^2$ is found to favor an assignment as the $η(1475)$ and the mass and width for the structure around 1835 MeV/c$^2$ are consistent with the $X(1835)$. The statistical significances of the two structures are $13.5 σ$ and $6.3 σ$, respectively. The results indicate that both $η(1475)$ and $X(1835)$ contain a sizeable $s\bar{s}$ component.

hep-ex↗

arXiv2018

Search for $ψ(3686)\to γη_c(η(1405))\to γπ^{+}π^{-}π^{0}$

Using a sample of $448.1\times10^{6}$ $ψ(3686)$ events collected with the BESIII detector, a search for the isospin violating decay $η_{c}\toπ^{+}π^{-}π^{0}$ via $ψ(3686)\toγη_{c}$ is presented. No signal is observed, and the upper limit on $\mathcal{B}(ψ(3686)\to γη_{c}\to γπ^{+}π^{-}π^{0} )$ is determined to be $1.6\times10^{-6}$ at the $90\%$ confidence level. In addition, a search for $η(1405)\to f_{0}(980)π^{0}$ in $ψ(3686)$ radiative decays is performed. No signal is observed, and the branching fraction $\mathcal{B}(ψ(3686)\toγη(1405)\to γf_{0}(980)π^{0}\toγπ^+π^-π^0 )$ is calculated to be less than $ 5.0\times10^{-7}$ at the $90\%$ confidence level.

hep-ex↗

arXiv2017

Observation of $χ_{c2}\toη'η'$ and $χ_{c0,2}\toηη'$

Using a sample of $447.9\times 10^6$ $ψ(3686)$ events collected with the BESIII detector in 2009 and 2012, we study the decays $χ_{c0,2}\to$ $η'η'$ and $ηη'$. The decays $χ_{c2}\toη'η'$, $χ_{c0}\toηη'$ and $χ_{c2}\toηη'$ are observed for the first time with statistical significances of $9.6σ$, $13.4σ$ and $7.5σ$, respectively. The branching fractions are determined to be $\mathcal{B}(χ_{c0}\toη'η') =(2.19\pm0.03\pm0.14)\times10^{-3}$, $\mathcal{B}(χ_{c2}\toη'η') = (4.76\pm0.56\pm0.38)\times10^{-5}$, $\mathcal{B}(χ_{c0}\toηη') = (8.92\pm0.84\pm0.65)\times10^{-5}$ and $\mathcal{B}(χ_{c2}\toηη') = (2.27\pm0.43\pm0.25)\times10^{-5}$, where the first uncertainties are statistical and the second systematic. The precision for the measurement of $\mathcal{B}(χ_{c0}\toη'η')$ is significantly improved compared to previous measurements. Based on the measured branching fractions, the role played by the doubly and singly Okubo-Zweig-Iizuka disconnected transition amplitudes for $χ_{c0,2}$ decays into pseudoscalar meson pairs can be clarified.

hep-ex↗

arXiv2017

Physics perspectives with AFTER@LHC (A Fixed Target ExpeRiment at LHC)

AFTER@LHC is an ambitious fixed-target project in order to address open questions in the domain of proton and neutron spins, Quark Gluon Plasma and high-$x$ physics, at the highest energy ever reached in the fixed-target mode. Indeed, thanks to the highly energetic 7 TeV proton and 2.76 A.TeV lead LHC beams, center-of-mass energies as large as $\sqrt{s_{NN}}$ = 115 GeV in pp/pA and $\sqrt{s_{NN}}$ = 72 GeV in AA can be reached, corresponding to an uncharted energy domain between SPS and RHIC. We report two main ways of performing fixed-target collisions at the LHC, both allowing for the usage of one of the existing LHC experiments. In these proceedings, after discussing the projected luminosities considered for one year of data taking at the LHC, we will present a selection of projections for light and heavy-flavour production.

hep-ex↗

arXiv2017

Branching fraction measurement of $J/ψ\rightarrow K_S K_L$ and search for $J/ψ\rightarrow K_S K_S$

Using a sample of $1.31 \times 10^{9}$ $J/ψ$ events collected with the BESIII detector at the BEPCII collider, we study the decays of $J/ψ\rightarrow K_S K_L$ and $K_S K_S$. The branching fraction of$J/ψ\rightarrow K_S K_L$ is determined to be ${\cal B}(J/ψ\rightarrow K_S K_L)=(1.93\pm0.01~(\rm{stat.})\pm0.05~(\rm{syst.}))\times10^{-4}$, which significantly improves on previous measurements. No clear signal is observed for the $J/ψ\rightarrow K_S K_S$ process, and the upper limit at the 95% confidence level for its branching fraction is determined to be ${\cal B}(J/ψ\rightarrow K_S K_S)<1.4\times10^{-8}$, which improves on the previous searches by two orders in magnitude and reaches the order of the Einstein-Podolsky-Rosen expectation.

hep-ex↗

arXiv2017

Measurement of the absolute branching fraction of $D_{s0}^{*\pm}(2317)\to π^0 D_{s}^{\pm}$

The process $e^+ e^- \to D_{s}^{*+} D_{s0}^{*-}(2317)+c.c.$ is observed for the first time with the data sample of 567~pb$^{-1}$ collected with the BESIII detector operating at the BEPCII collider at a center-of-mass energy $\sqrt{s} = 4.6$~GeV. The statistical significance of the $D_{s0}^{*-}(2317)$ signal is $5.8σ$ and the mass is measured to be ($2318.3\pm 1.2\pm 1.2$)~MeV/$c^{2}$. The absolute branching fraction $\mathcal{B}(D_{s0}^{*-}(2317)\to π^0 D_{s}^{-})$ is measured as $1.00^{+0.00}_{-0.14}\pm 0.14$ for the first time. The uncertainties are statistical and systematic, respectively.

hep-ex↗