arXiv subjects

Y. Guo

Publications and source records attributed to Y. Guo.

At least 127 records · Page 7Linked to original sources

arXiv2016

Sub-kpc ALMA imaging of compact star-forming galaxies at z~2.5: revealing the formation of dense galactic cores in the progenitors of compact quiescent galaxies

We present spatially-resolved Atacama Large Millimeter/sub-millimeter Array (ALMA) 870 $μ$m dust continuum maps of six massive, compact, dusty star-forming galaxies (SFGs) at $z\sim2.5$. These galaxies are selected for their small rest-frame optical sizes ($r_{\rm e, F160W}\sim1.6$ kpc) and high stellar-mass densities that suggest that they are direct progenitors of compact quiescent galaxies at $z\sim2$. The deep observations yield high far-infrared (FIR) luminosities of L$_{\rm IR}=10^{12.3-12.8}$ L$_{\odot}$ and star formation rates (SFRs) of SFR$=200-700$ M$_{\odot}$yr$^{-1}$, consistent with those of typical star-forming "main sequence" galaxies. The high-spatial resolution (FWHM$\sim$0.12"-0.18") ALMA and HST photometry are combined to construct deconvolved, mean radial profiles of their stellar mass and (UV+IR) SFR. We find that the dusty, nuclear IR-SFR overwhelmingly dominates the bolometric SFR up to $r\sim5$ kpc, by a factor of over 100$\times$ from the unobscured UV-SFR. Furthermore, the effective radius of the mean SFR profile ($r_{\rm e, SFR}\sim1$ kpc) is $\sim$30% smaller than that of the stellar mass profile. The implied structural evolution, if such nuclear starburst last for the estimated gas depletion time of $Δt=\pm100$ Myr, is a 4$\times$ increase of the stellar mass density within the central 1 kpc and a 1.6$\times$ decrease of the half-mass radius. This structural evolution fully supports dissipation-driven, formation scenarios in which strong nuclear starbursts transform larger, star-forming progenitors into compact quiescent galaxies.

astro-ph.GA↗

arXiv2016

Observation of $e^+e^- \rightarrow ωχ_{c1,2}$ near $\sqrt{s}$ = 4.42 and 4.6 GeV

Based on data samples collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies $\sqrt{s} >$ 4.4 GeV, the processes $e^+e^- \rightarrow ωχ_{c1,2}$ are observed for the first time. With an integrated luminosity of $1074 pb^{-1}$ near $\sqrt{s} =$ 4.42 GeV, a significant $ωχ_{c2}$ signal is found, and the cross section is measured to be $(20.9 \pm 3.2 \pm 2.5)\pb$. With $567 pb^{-1}$ near $\sqrt{s} =$ 4.6 GeV, a clear $ωχ_{c1}$ signal is seen, and the cross section is measured to be $(9.5 \pm 2.1 \pm 1.3) \pb$, while evidence is found for an $ωχ_{c2}$ signal. The first errors are statistical and the second are systematic. Due to low luminosity or low cross section at other energies, no significant signals are observed. In the $ωχ_{c2}$ cross section, an enhancement is seen around $\sqrt{s} =$ 4.42 GeV. Fitting the cross section with a coherent sum of the $ψ(4415)$ Breit-Wigner function and a phase space term, the branching fraction $\mathcal{B}(ψ(4415)\toωχ_{c2})$ is obtained to be of the order of $10^{-3}$.

hep-ex↗

arXiv2016

Observation of $h_{c}$ radiative decay $h_{c} \rightarrow γη'$ and evidence for $h_{c} \rightarrow γη$

A search for radiative decays of the $P$-wave spin singlet charmonium resonance $h_c$ is performed based on $4.48 \times 10^{8}$ $ψ'$ events collected with the BESIII detector operating at the BEPCII storage ring. Events of the reaction channels $h_{c} \rightarrow γη'$ and $γη$ are observed with a statistical significance of $8.4 σ$ and $4.0 σ$, respectively, for the first time. The branching fractions of $h_{c} \rightarrow γη'$ and $h_{c} \rightarrow γη$ are measured to be $\mathcal{B}(h_{c} \rightarrow γη')=(1.52 \pm 0.27 \pm 0.29)\times10^{-3}$ and $\mathcal{B}(h_{c} \rightarrow γη)=(4.7 \pm 1.5 \pm 1.4)\times10^{-4}$, respectively, where the first errors are statistical and the second are systematic uncertainties.

hep-ex↗

arXiv2016

Improved measurement of the absolute branching fraction of $D^{+}\rightarrow \bar K^0 μ^{+}ν_μ$

By analyzing 2.93 fb$^{-1}$ of data collected at $\sqrt s=3.773$ GeV with the BESIII detector, we measure the absolute branching fraction ${\mathcal B}(D^{+}\rightarrow\bar K^0μ^{+}ν_μ)=(8.72 \pm 0.07_{\rm stat.} \pm 0.18_{\rm sys.})\%$, which is consistent with previous measurements within uncertainties but with significantly improved precision. Combining the Particle Data Group values of ${\mathcal B}(D^0\to K^-μ^+ν_μ)$, ${\mathcal B}(D^{+}\rightarrow\bar K^0 e^{+}ν_{e})$, and the lifetimes of the $D^0$ and $D^+$ mesons with the value of ${\mathcal B}(D^{+}\rightarrow\bar K^0 μ^{+}ν_μ)$ measured in this work, we determine the following ratios of partial widths: $Γ(D^0\to K^-μ^+ν_μ)/Γ(D^{+}\rightarrow\bar K^0μ^{+}ν_μ)=0.963\pm0.044$ and $Γ(D^{+}\rightarrow\bar K^0 μ^{+}ν_μ)/Γ(D^{+}\rightarrow\bar K^0 e^{+}ν_{e})=0.988\pm0.033$.

hep-ex↗

arXiv2016

Observation of $e^{+}e^{-} \to η^{\prime} J/ψ$ at center-of-mass energies between 4.189 and 4.600 GeV

The process $e^{+}e^{-}\to η^{\prime} J/ψ$ is observed for the first time with a statistical significance of $8.6σ$ at center-of-mass energy $\sqrt{s} = 4.226$ GeV and $7.3σ$ at $\sqrt{s} = 4.258$ GeV using data samples collected with the BESIII detector. The Born cross sections are measured to be $(3.7 \pm 0.7 \pm 0.3)$ and $(3.9 \pm 0.8 \pm 0.3)$ pb at $\sqrt{s} = 4.226$ and $4.258$ GeV, respectively, where the first errors are statistical and the second systematic. Upper limits at the 90% confidence level of the Born cross sections are also reported at other 12 energy points.

hep-ex↗

arXiv2016

Explosive Chromospheric Evaporation in a Circular-ribbon Flare

In this paper, we report our multiwavelength observations of the C4.2 circular-ribbon flare in active region (AR) 12434 on 2015 October 16. The short-lived flare was associated with positive magnetic polarities and a negative polarity inside, as revealed by the photospheric line-of-sight magnetograms. Such magnetic pattern is strongly indicative of a magnetic null point and spine-fan configuration in the corona. The flare was triggered by the eruption of a mini-filament residing in the AR, which produced the inner flare ribbon (IFR) and the southern part of a closed circular flare ribbon (CFR). When the eruptive filament reached the null point, it triggered null point magnetic reconnection with the ambient open field and generated the bright CFR and a blowout jet. Raster observations of the \textit{Interface Region Imaging Spectrograph} (\textit{IRIS}) show plasma upflow at speed of 35$-$120 km s$^{-1}$ in the Fe {\sc xxi} 1354.09 Å line ($\log T\approx7.05$) and downflow at speed of 10$-$60 km s$^{-1}$ in the Si {\sc iv} 1393.77 Å line ($\log T\approx4.8$) at certain locations of the CFR and IFR during the impulsive phase of flare, indicating explosive chromospheric evaporation. Coincidence of the single HXR source at 12$-$25 keV with the IFR and calculation based on the thick-target model suggest that the explosive evaporation was most probably driven by nonthermal electrons.

astro-ph.SR↗

arXiv2016

Measurement of the absolute branching fraction of $D^{+}\rightarrow\bar K^0 e^{+}ν_{e}$ via $\bar K^0\toπ^0π^0$

By analyzing 2.93 fb$^{-1}$ data collected at the center-of-mass energy $\sqrt s=3.773$ GeV with the BESIII detector, we measure the absolute branching fraction of the semileptonic decay $D^+\rightarrow\bar K^0 e^{+}ν_{e}$ to be ${\mathcal B}(D^{+}\rightarrow\bar K^0 e^{+}ν_{e})=(8.59 \pm 0.14 \pm 0.21)\%$ using $\bar K^0\to K^0_S\to π^0π^0$, where the first uncertainty is statistical and the second systematic. Our result is consistent with previous measurements within uncertainties.

hep-ex↗

arXiv2016

Observation of an anomalous line shape of the $η^{\prime}π^{+}π^{-}$ mass spectrum near the $p\bar{p}$ mass threshold in $J/ψ\rightarrowγη^{\prime}π^{+}π^{-}$

Using $1.09\times10^{9}$ $J/ψ$ events collected by the BESIII experiment in 2012, we study the $J/ψ\rightarrowγη^{\prime}π^{+}π^{-}$ process and observe a significant abrupt change in the slope of the $η^{\prime}π^{+}π^{-}$ invariant mass distribution at the proton-antiproton ($p\bar{p}$) mass threshold. We use two models to characterize the $η^{\prime}π^{+}π^{-}$ line shape around $1.85~\text{GeV}/c^{2}$: one which explicitly incorporates the opening of a decay threshold in the mass spectrum (Flatté formula), and another which is the coherent sum of two resonant amplitudes. Both fits show almost equally good agreement with data, and suggest the existence of either a broad state around $1.85~\text{GeV}/c^{2}$ with strong couplings to $p\bar{p}$ final states or a narrow state just below the $p\bar{p}$ mass threshold. Although we cannot distinguish between the fits, either one supports the existence of a $p\bar{p}$ molecule-like state or bound state with greater than $7σ$ significance.

hep-ex↗

arXiv2016

Study of $ψ$ decays to the $Ξ^{-}\barΞ^{+}$ and $Σ(1385)^{\mp}\barΣ(1385)^{\pm}$ final states

We study the decays of the charmonium resonances $J/ψ$ and $ψ(3686)$ to the final states $Ξ^{-}\barΞ^{+}$, $Σ(1385)^{\mp}\barΣ(1385)^{\pm}$ based on a single baryon tag method using data samples of $(223.7 \pm 1.4) \times 10^{6}$ $J/ψ$ and $(106.4 \pm 0.9) \times 10^{6}$ $ψ(3686)$ events collected with the BESIII detector at the BEPCII collider. The decay $ψ(3686)\rightarrowΣ(1385)^{\mp}\barΣ(1385)^{\pm}$ is observed for the first time, and the measurements of the other processes, including the branching fractions and angular distributions, are in good agreement with and much more precise than the previously published results. Additionally, the ratios $\frac{\cal{B}(ψ(3686)\rightarrowΞ^{-}\barΞ^{+})}{\cal{B}(J/ψ\rightarrowΞ^{-}\barΞ^{+})}$, $\frac{\cal{B}(ψ(3686)\rightarrowΣ(1385)^{-}\barΣ(1385)^{+})}{\cal{B}(J/ψ\rightarrowΣ(1385)^{-}\barΣ(1385)^{+})}$ and $\frac{\cal{B}(ψ(3686)\rightarrowΣ(1385)^{+}\barΣ(1385)^{-})}{\cal{B}(J/ψ\rightarrowΣ(1385)^{+}\barΣ(1385)^{-})}$ are determined.

hep-ex↗

arXiv2016

Topologically protected edge gap solitons of interacting Bosons in one-dimensional superlattices

We comprehensively investigate the nontrivial states of interacting Bose system in one-dimensional optical superlattices under the open boundary condition. Our results show that there exists a kind of stable localized states: edge gap solitons. We argue that the states originate from the eigenstates of independent edge parabolas. In particular, the edge gap solitons exhibit a nonzero topological invariant. The topological nature is due to the connection of the present model to the quantized adiabatic particle transport problem. In addition, the composition relations between the gap solitons and the extend states under the open boundary condition are discussed.

cond-mat.quant-gas↗

arXiv2016

The Dynamics of the Schrodinger-Newton System with Self-Field Coupling

We probe the dynamics of a modified form of the Schrodinger-Newton system of gravity coupled to single particle quantum mechanics. At the masses of interest here, the ones associated with the onset of "collapse" (where the gravitational attraction is competitive with the quantum mechanical dissipation), we show that the Schrodinger ground state energies match the Dirac ones with an error of ~ 10%. At the Planck mass scale, we predict the critical mass at which a potential collapse could occur for the self-coupled gravitational case, m ~ 3.3 Planck mass, and show that gravitational attraction opposes Gaussian spreading at around this value, which is a factor of two higher than the one predicted (and verified) for the Schrodinger-Newton system. Unlike the Schrodinger-Newton dynamics, we do not find that the self-coupled case tends to decay towards its ground state; there is no collapse in this case.

gr-qc↗

arXiv2016

Study of $J/ψ\to p\bar{p}ϕ$ at BESIII

Using a data sample of $1.31 \times 10^{9}$ $J/ψ$ events accumulated with the BESIII detector, the decay $J/ψ\to p\bar{p}ϕ$ is studied via two decay modes, $ϕ\to K^{0}_{S}K^{0}_{L}$ and $ϕ\to K^{+}K^{-}$. The branching fraction of $J/ψ\to p\bar{p}ϕ$ is measured to be $\mathcal{B}(J/ψ\to p\bar{p}ϕ)=[5.23\pm0.06(\mbox{stat})\pm0.33(\mbox{syst})]\times10^{-5}$, which agrees well with a previously published measurement, but with a significantly improved precision. No evident enhancement near the $p\bar{p}$ mass threshold, denoted as $X(p\bar{p})$, is observed, and the upper limit on the branching fraction of $J/ψ\to X(p\bar{p})ϕ\to p\bar{p}ϕ$ is determined to be $\mathcal{B}(J/ψ\to X(p\bar{p})ϕ\to p\bar{p}ϕ)<2.1\times10^{-7}$ at the 90\% confidence level.

hep-ex↗

arXiv2016

Search for the weak decay $η^{\prime}\to K^{\pm}π^{\mp}$ and precise measurement of the branching fraction ${\cal B}(J/ψ\toϕη^{\prime})$

We present the first search for the rare decay of $η^\prime$ into $K^{\pm}π^{\mp}$ in $J/ψ\toϕη^{\prime}$, using a sample of $1.3\times10^{9}$ $J/ψ$ events collected with the BESIII detector. No significant signal is observed, and the upper limit at the 90\% confidence level for the ratio $\frac{{\cal B}(η^{\prime}\to K^{\pm}π^{\mp})}{{\cal B}(η^{\prime}\toγπ^{+}π^{-})}$ is determined to be $1.3\times10^{-4}$. In addition, we report the measurement of the branching fraction of $J/ψ\toϕη^{\prime}$ to be $(5.10\pm0.03(\text{stat.})\pm0.32(\text{syst.}))\times10^{-4}$, which agrees with previous results from BESII.

hep-ex↗

arXiv2016

Measurement of the transverse single-spin asymmetry in $p^\uparrow+p \to W^{\pm}/Z^0$ at RHIC

We present the measurement of the transverse single-spin asymmetry of weak boson production in transversely polarized proton-proton collisions at $\sqrt{s} = 500~\text{GeV}$ by the STAR experiment at RHIC. The measured observable is sensitive to the Sivers function, one of the transverse momentum dependent parton distribution functions, which is predicted to have the opposite sign in proton-proton collisions from that observed in deep inelastic lepton-proton scattering. These data provide the first experimental investigation of the non-universality of the Sivers function, fundamental to our understanding of QCD.

nucl-ex↗

arXiv2016

Measurements of absolute hadronic branching fractions of $Λ_{c}^{+}$ baryon

Using $567\rm{pb}^{-1}$ of $e^+e^-$ collisions recorded at $\sqrt{s}=4.599\rm{GeV}$ with the BESIII detector, we report first measurements of absolute hadronic branching fractions of Cabibbo-favored decays of the $Λ_{c}^{+}$ baryon with a double-tag technique. A global least-square fitter is utilized to improve the measured precision. Among the measurements for twelve $Λ_{c}^{+}$ decay modes, the branching fraction for $Λ_{c}^{+} \rightarrow pK^-π^+$ is determined to be $(5.84\pm0.27\pm0.23)\%$, where the first uncertainty is statistical and the second is systematic. In addition, the measurements of the branching fractions of the other eleven Cabbibo-favored hadronic decay modes are significantly improved.

hep-ex↗

arXiv2016

The $ϕ(1020)\rightarrow e^{+}e^{-}$ meson decay measured with the STAR experiment in Au+Au collisions at $\sqrt{s_{_{NN}}}$ = 200 GeV

We report the measurement of the leptonic ($e^{+}e^{-}$) decay channel of the $ϕ$(1020) meson in Au+Au collisions at $\sqrt{s_{_{NN}}}$ = 200 GeV by the STAR experiment. The transverse momentum ($p_{\rm T}$) spectrum is measured for 0.1 $\le p_{\rm T} \le 2.5$ GeV/$c$ at mid-rapidity ($|y|\le1$). We obtain the $p_{\rm T}$-integrated $ϕ$(1020) mass $M_ϕ=1017.7\pm0.8 (\rm {stat.}) \pm0.9 (\rm {sys.})$ MeV/$c^{2}$ and width $Γ_ϕ = 8.0\pm 2.5(\rm {stat.}) \pm 2.3(\rm {sys.}) \textrm{MeV/}c^{2}$, which are within 1.5\,$σ$ and 1.1\,$σ$ of the vacuum values, respectively. No significant difference is observed in the measured $p_{\rm T}$ spectrum, $dN/dy$, or $\left $ of the $ϕ$(1020) meson between the $e^{+}e^{-}$ and hadronic ($K^{+}K^{-}$) decay channels as measured by the same experiment. The experimental results are compared to a theoretical model including medium-modified $ϕ$(1020).

hep-ex↗

arXiv2016

Measurement of azimuthal asymmetries in inclusive charged dipion production in $e^+e^-$ annihilations at $\sqrt{s}$ = 3.65 GeV

We present a measurement of the azimuthal asymmetries of two charged pions in the inclusive process $e^+e^-\rightarrow ππX$ based on a data set of 62 $\rm{pb}^{-1}$ at the center-of-mass energy $\sqrt{s}=3.65$ GeV collected with the BESIII detector. These asymmetries can be attributed to the Collins fragmentation function. We observe a nonzero asymmetry, which increases with increasing pion momentum. As our energy scale is close to that of the existing semi-inclusive deep inelastic scattering experimental data, the measured asymmetries are important inputs for the global analysis of extracting the quark transversity distribution inside the nucleon and are valuable to explore the energy evolution of the spin-dependent fragmentation function.

hep-ex↗

arXiv2016

Measurement of elliptic flow of light nuclei at $\sqrt{s_{NN}}$ = 200, 62.4, 39, 27, 19.6, 11.5, and 7.7 GeV at RHIC

We present measurements of 2$^{nd}$ order azimuthal anisotropy ($v_{2}$) at mid-rapidity $(|y|<1.0)$ for light nuclei d, t, $^{3}$He (for $\sqrt{s_{NN}}$ = 200, 62.4, 39, 27, 19.6, 11.5, and 7.7 GeV) and anti-nuclei $\bar{\rm d}$ ($\sqrt{s_{NN}}$ = 200, 62.4, 39, 27, and 19.6 GeV) and $^{3}\bar{\rm He}$ ($\sqrt{s_{NN}}$ = 200 GeV) in the STAR (Solenoidal Tracker at RHIC) experiment. The $v_{2}$ for these light nuclei produced in heavy-ion collisions is compared with those for p and $\bar{\rm p}$. We observe mass ordering in nuclei $v_{2}(p_{T})$ at low transverse momenta ($p_{T}<2.0$ GeV/$c$). We also find a centrality dependence of $v_{2}$ for d and $\bar{\rm d}$. The magnitude of $v_{2}$ for t and $^{3}$He agree within statistical errors. Light-nuclei $v_{2}$ are compared with predictions from a blast wave model. Atomic mass number ($A$) scaling of light-nuclei $v_{2}(p_{T})$ seems to hold for $p_{T}/A < 1.5$ GeV/$c$. Results on light-nuclei $v_{2}$ from a transport-plus-coalescence model are consistent with the experimental measurements.

nucl-ex↗