arXiv subjects

Y. Huang

Publications and source records attributed to Y. Huang.

At least 271 records · Page 15Linked to original sources

arXiv2013

Study of $J/ψ\rightarrow ωp \bar{p}$ at BESIII

The decay $J/ψ\rightarrow ωp \bar{p}$ has been studied, using $225.3\times 10^{6}$ $J/ψ$ events accumulated at BESIII. No significant enhancement near the $p\bar{p}$ invariant-mass threshold (denoted as $X(p\bar{p})$) is observed. The upper limit of the branching fraction $\mathcal{B}(J/ψ\rightarrow ωX(p\bar{p}) \rightarrow ωp \bar{p})$ is determined to be $3.9\times10^{-6}$ at the 95% confidence level. The branching fraction of $J/ψ\rightarrow ωp \bar{p}$ is measured to be $\mathcal{B}(J/ψ\rightarrow ωp \bar{p}) =(9.0 \pm 0.2\ (\text{stat.})\pm 0.9\ (\text{syst.})) \times 10^{-4}$.

hep-ex↗

arXiv2013

Search for Baryonic Decays of ψ(3770) and ψ(4040)

By analyzing data samples of 2.9 fb^{-1} collected at \sqrt s=3.773 GeV, 482 pb^{-1} collected at \sqrt s=4.009 GeV and 67 pb^{-1} collected at \sqrt s=3.542, 3.554, 3.561, 3.600 and 3.650 GeV with the BESIII detector at the BEPCII storage ring, we search for ψ(3770) and ψ(4040) decay to baryonic final states, including Λ\barΛπ^+π^-, Λ\barΛπ^0, Λ\barΛη, Σ^+ \barΣ^-, Σ^0 \barΣ^0, Ξ^-\barΞ^+ and Ξ^0\barΞ^0 decays. None are observed, and upper limits are set at the 90% confidence level.

hep-ex↗

arXiv2013

Observation of a charged charmoniumlike structure in e+e- to pi+pi-J/psi at \sqrt{s}=4.26 GeV

We study the process e+e- to pi+pi-J/psi at a center-of-mass energy of 4.260 GeV using a 525 pb^{-1} data sample collected with the BESIII detector operating at the Beijing Electron Positron Collider. The Born cross section is measured to be (62.9\pm 1.9\pm 3.7) pb, consistent with the production of the Y(4260). We observe a structure at around 3.9 GeV/c^2 in the π^\pm J/psi mass spectrum, which we refer to as the Z_c(3900). If interpreted as a new particle, it is unusual in that it carries an electric charge and couples to charmonium. A fit to the π^\pm J/psi invariant mass spectrum, neglecting interference, results in a mass of (3899.0\pm 3.6\pm 4.9) MeV/c^2 and a width of (46\pm 10\pm 20) MeV. Its production ratio is measured to be R=\frac{σ(e+e- to π^\pm Z_c(3900)^\mp to pi+pi-J/psi))} {σ(e+e- to pi+pi-J/psi)}=(21.5\pm 3.3\pm 7.5)%. In all measurements the first errors are statistical and the second are systematic.

hep-ex↗

arXiv2013

Search for the Lepton Flavor Violation Process $J/ψ\to eμ$ at BESIII

We search for the lepton-flavor-violating decay of the $J/ψ$ into an electron and a muon using $(225.3\pm2.8)\times 10^{6}$ $J/ψ$ events collected with the BESIII detector at the BEPCII collider. Four candidate events are found in the signal region, consistent with background expectations. An upper limit on the branching fraction of $\mathcal{B}(J/ψ\to eμ)< 1.5 \times 10^{-7}$ (90% C.L.) is obtained.

hep-ex↗

arXiv2013

Partial wave analysis of $ψ(2S) \to p \bar{p}η$

Using a sample of $1.06 \times 10^{8}$ $ψ(2S)$ events collected with the BESIII detector at BEPCII, the decay $ψ(2S) \to p \bar{p}η$ is studied. A partial wave analysis determines that the intermediate state N(1535) with a mass of $1524\pm5^{+10}_{-4}$ MeV/$c^2$ and a width of $130^{+27+57}_{-24-10}$ MeV/$c^2$ is dominant in the decay; the product branching fraction is determined to be $B(ψ(2S) \to N(1535)\bar{p})\times B(N(1535)\to pη)+c.c. = (5.2\pm0.3^{+3.2}_{-1.2})\times 10^{-5}$. Furthermore, the branching fraction of $ψ(2S) \to ηp \bar{p}$ is measured to be $(6.4\pm0.2\pm0.6)\times 10^{-5}$.

hep-ex↗

arXiv2013

Measurement of $η^\prime\rightarrow π^+π^- e^+e^-$ and $η^\prime\rightarrow π^+π^-μ^+μ^-$

Based on a sample of 225.3 million J/ψevents accumulated with the BESIII detector at the BEPCII, the decays of η' to pi+pi-l+l- are studied via J/ψto γη'. A clear η' signal is observed in the pi+pi-e+e- mass spectrum, and the branching fraction is measured to be \BR(η' to pi+pi-e+e-) = (2.11\pm0.12 (stat.)\pm0.15 (syst.))\times10^{-3}, which is in good agreement with theoretical predictions and the previous measurement, but is determined with much higher precision. No η' signal is found in the pi+ pi- mu+ mu- mass spectrum, and the upper limit is determined to be \BR(η' to pi+ pi- mu+ mu-)<2.9\times10^{-5} at the 90% confidence level.

hep-ex↗

arXiv2013

Measurements of Baryon Pair Decays of $χ_{cJ}$ Mesons

Using 106 $\times 10^{6}$ $ψ^{\prime}$ decays collected with the BESIII detector at the BEPCII, three decays of $χ_{cJ}$ ($J=0,1,2$) with baryon pairs ($\llb$, $\ssb$, $\SSB$) in the final state have been studied. The branching fractions are measured to be $\cal{B}$$(χ_{c0,1,2}\rightarrowΛ\barΛ) =(33.3 \pm 2.0 \pm 2.6)\times 10^{-5}$, $(12.2 \pm 1.1 \pm 1.1)\times 10^{-5}$, $(20.8 \pm 1.6 \pm 2.3)\times 10^{-5}$; $\cal{B}$$(χ_{c0,1,2}\rightarrowΣ^{0}\barΣ^{0})$ = $(47.8 \pm 3.4 \pm 3.9)\times 10^{-5}$, $(3.8 \pm 1.0 \pm 0.5)\times 10^{-5}$, $(4.0 \pm 1.1 \pm 0.5) \times 10^{-5}$; and $\cal{B}$$(χ_{c0,1,2}\rightarrowΣ^{+}\barΣ^{-})$ = $(45.4 \pm 4.2 \pm 3.0)\times 10^{-5}$, $(5.4 \pm 1.5 \pm 0.5)\times 10^{-5}$, $(4.9 \pm 1.9 \pm 0.7)\times 10^{-5}$, where the first error is statistical and the second is systematic. Upper limits on the branching fractions for the decays of $χ_{c1,2}\rightarrowΣ^{0}\barΣ^{0}$, $Σ^{+}\barΣ^{-}$, are estimated to be $\cal{B}$$(χ_{c1}\rightarrowΣ^{0}\barΣ^{0}) < 6.2\times 10^{-5}$, $\cal{B}$$(χ_{c2}\rightarrowΣ^{0}\barΣ^{0}) < 6.5\times 10^{-5}$, $\cal{B}$$(χ_{c1}\rightarrowΣ^{+}\barΣ^{-}) < 8.7\times 10^{-5}$ and $\cal{B}$$(χ_{c2}\rightarrowΣ^{+}\barΣ^{-}) < 8.8\times 10^{-5}$ at the 90% confidence level.

hep-ex↗

arXiv2013

Search for $η$ and $η^\prime\to π^+ e^- \barν_e +c.c.$ decays in $\jpsi \to ϕη$ and $ϕη^\prime$

Using a sample of 225.3 million $\jpsi$ events collected with the BESIII detector at the BEPCII $e^+e^-$ collider in 2009, searches for the decays of $η$ and $η^\prime\toπ^+ e^- \barν_e +c.c.$ in $\jpsi \to ϕη$ and $ϕη^\prime$ are performed. The $ϕ$ signals, which are reconstructed in $K^+K^-$ final states, are used to tag $η$ and $η^\prime$ semileptonic decays. No signals are observed for either $η$ or $η^\prime$, and upper limits at the 90% confidence level are determined to be $7.3\times 10^{-4}$ and $5.0\times 10^{-4}$ for the ratios $\frac{{\mathcal B}(η\to π^+ e^- \barν_e +c.c.)}{{\mathcal B}(η\to \pip\pim\piz)}$ and $\frac{{\mathcal B}(η^\prime\to π^+ e^-\barν_e +c.c.)}{{\mathcal B}(η^\prime \to \pip\pimη)}$, respectively. These are the first upper limit values determined for $η$ and $η^\prime$ semileptonic weak decays.

hep-ex↗

arXiv2013

Formation of the density wave energy gap in Na$_2$Ti$_2$Sb$_2$O: an optical spectroscopy study

We performed optical spectroscopy measurement on single crystals of Na$_2$Ti$_2$Sb$_2$O, which is the parent compound for the newly discovered Ti-based superconductors. The study reveals significant spectral change across the phase transition at 114 K and formation of a density-wave type energy gap. The opening of the gap removes most part of the free carrier spectral weight and causes a dramatic reduction of the carrier scattering rate. The ratio of 2$Δ/k_BT_s\approx$14 is considerably larger than the mean-field value based on the weak-coupling BCS theory. The study also reveals a weak correlation effect in the titanium oxypnictides.

cond-mat.supr-con↗

arXiv2013

Partial wave analysis of $J/ψ\to γηη$

Based on a sample of $2.25\times 10^{8}$ $J/ψ$ events collected with the BESIII detector at BEPCII, a full partial wave analysis on $J/ψ\toγηη$ was performed using the relativistic covariant tensor amplitude method. The results show that the dominant $0^{++}$ and $2^{++}$ components are from the $f_0(1710)$, $f_0(2100)$, $f_0(1500)$, $f_2'(1525)$, $f_2(1810)$ and $f_2(2340)$. The resonance parameters and branching fractions are also presented.

hep-ex↗

arXiv2012

Study of the near-threshold $ωϕ$ mass enhancement in doubly OZI suppressed $J/ψ\to γωϕ$ decays

A 2.25$\times10^8$ $\jpsi$ event sample accumulated with the BESIII detector is used to study the doubly OZI suppressed decay modes $\jpsi\toγ\of$, $ω\to\ppp$, $ϕ\to\kk$. A strong deviation ($>$ 30$σ$) from three-body $\jpsi\toγωϕ$ phase space is observed near the $ωϕ$ mass threshold that is consistent with a previous observation reported by the BESII experiment. A partial wave analysis with a tensor covariant amplitude that assumes that the enhancement is due to the presence of a resonance, the X(1810), is performed, and confirms that the spin-parity of the X(1810) is $0^{++}$. The mass and width of the X(1810) are determined to be $M=1795\pm7$(stat)$^{+13}_{-5}$(syst)$\pm$19(mod) MeV/$c^2$ and $Γ=95\pm10$(stat)$^{+21}_{-34}$(syst)$\pm$75(mod) MeV/$c^2$, respectively, and the product branching fraction is measured to be ${\cal B}(\jpsi\toγX(1810))\times{\cal B}(X(1810)\to\of)=(2.00\pm0.08$(stat)$^{+0.45}_{-1.00}$(syst)$\pm$1.30(mod))$\times10^{-4}$. %where the first error is the statistical error and the second the systematical error. These results are consistent within errors with those of the BESII experiment.

hep-ex↗

arXiv2012

Effect of disorder in the charge-density-wave compounds LaTe$_{1.95}$ and CeTe$_{1.95-x}$Se$_x$ (x=0 and 0.16) as revealed by optical spectroscopy

We present optical spectroscopy measurements on rare-earth ditelluride single crystals of LaTe$_{1.95}$ and CeTe$_{1.95-x}$Se$_x$ (x=0 and 0.16). The measurements reveal formation of charge density wave energy gaps at rather high energy levels, e.g. 2$Δ\sim$ 8500 \cm for LaTe$_{1.95}$, and 6800 \cm for CeTe$_{1.95}$. More strikingly, the study reveals that, different from the rare-earth tri-tellurides, the Te vacancies and disorder effect play a key role in the low-energy charge excitations of ditelluride systems. Although an eminent peak is observed between 800 and 1500 \cm in conductivity spectra for LaTe$_{1.95}$, and CeTe$_{1.95-x}$Se$_x$ (x=0. 0.16), our analysis indicates that it could not be attributed to the formation of a small energy gap, instead it could be well accounted for by the localization modified Drude model. Our study also indicates that the low-tempreature optical spectroscopic features are distinctly different from a semiconducting CDW state with entirely gapped Fermi surfaces.

cond-mat.str-el↗

arXiv2012

Beaming Effect in Fermi Blazars

The γ-ray loud blazars (flat spectrum radio quasars--FSRQs and BL Lacertae objects-BLs) are very bright in the γ-ray bands, which is perhaps associated with a beaming effect. Therefore, one can expect that the γ-ray luminosity is correlated with the beaming factor. In this paper, we investigated the relation between the radio Doppler factors and the gamma-ray luminosities. Our analysis suggests that the γ-ray luminosity be strongly correlated with the factor of δ_R for the whole sample, FSRQs, and BLs. When the effect of a common redshift is excluded, the correlation still exists for the FSRQs sub-sample suggesting that the γ-rays are strongly beamed. However, the partial correlation analysis does not show a correlation for the small BL Lac sample.

astro-ph.HE↗

arXiv2012

Surface adatom conductance filtering in scanning tunneling spectroscopy of Co-doped BaFe2As2 iron pnictide superconductors

We establish in a combination of ab initio theory and experiments that the tunneling process in scanning tunneling microscopy/spectroscopy on the A-122 iron pnictide superconductors - in this case BaFe$_{2-x}$Co$_x$As$_2$ - involve a strong adatom filtering of the differential conductance from the near-EF Fe3d states, which in turn originates from the top-most sub-surface Fe layer of the crystal. The calculations show that the dominance of surface Ba-related tunneling pathways leaves fingerprints found in the experimental differential conductance data, including large particle-hole asymmetry and an energy-dependent contrast inversion.

cond-mat.supr-con↗

arXiv2011

Hertz-level Measurement of the 40Ca+ 4s 2S1/2-3d 2D5/2 Clock Transition Frequency With Respect to the SI Second through GPS

We report a frequency measurement of the clock transition of a single ^40Ca^+ ion trapped and laser cooled in a miniature ring Paul trap with 10^-15 level uncertainty. In the measurement, we used an optical frequency comb referenced to a Hydrogen maser, which was calibrated to the SI second through the Global Positioning System (GPS). Two rounds of measurements were taken in May and June 2011, respectively. The frequency was measured to be 411 042 129 776 393.0(1.6) Hz with a fractional uncertainty of 3.9{\times}10^-15 in a total averaging time of > 2{\times}10^6 s within 32 days.

physics.atom-ph↗

arXiv2011

Equilibria of biological aggregations with nonlocal repulsive-attractive interactions

We consider the aggregation equation $ρ_{t}-\nabla\cdot(ρ\nabla K\astρ) =0$ in $\mathbb{R}^{n}$, where the interaction potential $K$ incorporates short-range Newtonian repulsion and long-range power-law attraction. We study the global well-posedness of solutions and investigate analytically and numerically the equilibrium solutions. We show that there exist unique equilibria supported on a ball of $\mathbb{R}^n$. By using the method of moving planes we prove that such equilibria are radially symmetric and monotone in the radial coordinate. We perform asymptotic studies for the limiting cases when the exponent of the power-law attraction approaches infinity and a Newtonian singularity, respectively. Numerical simulations suggest that equilibria studied here are global attractors for the dynamics of the aggregation model.

math.AP↗

arXiv2010

Mini review of Poincaré invariant quantum theory

We review the construction and applications of exactly Poincaré invariant quantum mechanical models of few-degree of freedom systems. We discuss the construction of dynamical representations of the Poincaré group on few-particle Hilbert spaces, the relation to quantum field theory, the formulation of cluster properties, and practical considerations related to the construction of realistic interactions and the solution of the dynamical equations. Selected applications illustrate the utility of this approach.

math-ph↗

arXiv2009

Optical properties of BaFe$_{2-x}$Co$_x$As$_2$

We present detailed temperature dependent optical data on BaFe$_{2-x}$Co$_{x}$As$_{2}$ (BCFA), with x = 0.14, between 4 meV and 6.5 eV. We analyze our spectra to determine the main optical parameters and show that in this material the interband conductivity already starts around 10 meV. We determine the superfluid density to be 2.2 10^{7}$ cm^{-2}, which places optimally doped BFCA close to the Uemura line. Our experimental data shows clear signs of a superconducting gap with 2$Δ_{1}$ = 6.2 $\pm$ 0.8 meV. In addition we show that the optical spectra are consistent with the presence of an additional band of strongly scattered carriers with a larger gap, 2$Δ_{2}$ = 14 $\pm$ 2 meV.

cond-mat.supr-con↗