arXiv subjects

M. He

Publications and source records attributed to M. He.

At least 73 records · Page 4Linked to original sources

arXiv2015

Search for the $η_c(2S)/h_c\to p\bar{p}$ decays and measurements of the $χ_{cJ}\to p\bar{p}$ branching fractions

Using a sample of $1.06\times10^{8}~ψ(3686)$ events collected with the BESIII detector at BEPCII, the decays $η_{c}(2S)\to p\bar{p}$ and $h_{c}\to p\bar{p}$ are searched for, where $η_c(2S)$ and $h_c$ are reconstructed in the decay chains $ψ(3686)\toγη_{c}(2S)$, $η_{c}(2S)\to p\bar{p}$ and $ψ(3686)\toπ^{0}h_{c}$, $h_{c}\to p\bar{p}$, respectively. No significant signals are observed. The upper limits of the product branching fractions are determined to be $\mathcal{B}(ψ(3686)\toγη_c(2S))\times\mathcal{B}(η_{c}(2S)\to p\bar{p})<1.4\times10^{-6}$ and $\mathcal{B}(ψ(3686)\toπ^0h_c)\times\mathcal{B}(h_{c}\to p\bar{p})<1.3\times10^{-7}$ at the 90% C.L.. The branching fractions for $χ_{cJ}\to p\bar{p}$ $(J=0,~1,~2)$ are also measured to be $(24.5\pm0.8\pm1.3,~8.6\pm0.5\pm0.5,~8.4\pm0.5\pm0.5)\times10^{-5}$, which are the world's most precise measurements.

hep-ex↗

arXiv2014

Search for a Light Sterile Neutrino at Daya Bay

A search for light sterile neutrino mixing was performed with the first 217 days of data from the Daya Bay Reactor Antineutrino Experiment. The experiment's unique configuration of multiple baselines from six 2.9~GW$_{\rm th}$ nuclear reactors to six antineutrino detectors deployed in two near (effective baselines 512~m and 561~m) and one far (1579~m) underground experimental halls makes it possible to test for oscillations to a fourth (sterile) neutrino in the $10^{\rm -3}~{\rm eV}^{2} < |Δm_{41}^{2}| < 0.3~{\rm eV}^{2}$ range. The relative spectral distortion due to electron antineutrino disappearance was found to be consistent with that of the three-flavor oscillation model. The derived limits on $\sin^22θ_{14}$ cover the $10^{-3}~{\rm eV}^{2} \lesssim |Δm^{2}_{41}| \lesssim 0.1~{\rm eV}^{2}$ region, which was largely unexplored.

hep-ex↗

arXiv2014

Observation of $J/ψ\rightarrow p\bar{p}a_{0}(980)$ at BESIII

Using $2.25\times10^{8}$ $J/ψ$ events collected with the BESIII detector at the BEPCII storage rings, we observe for the first time the process $J/ψ\rightarrow p\bar{p}a_{0}(980)$, $a_{0}(980)\rightarrow π^{0}η$ with a significance of $6.5σ$ ($3.2σ$ including systematic uncertainties). The product branching fraction of $J/ψ\rightarrow p\bar{p}a_{0}(980)\rightarrow p\bar{p}π^{0}η$ is measured to be $(6.8\pm1.2\pm1.3)\times 10^{-5}$, where the first error is statistical and the second is systematic. This measurement provides information on the $a_{0}$ production near threshold coupling to $p\bar{p}$ and improves the understanding of the dynamics of $J/ψ$ decays to four body processes.

hep-ex↗

arXiv2014

Properties of Thermal Photons at RHIC and LHC

We study the emission characteristics of thermal photons at RHIC and LHC as affected by both the space-time evolution of the bulk medium and the thermal emission rates. For the former we compare the results of two evolution models (expanding fireball and hydrodynamics). For the latter, we detail the influence of hadronic emission components and study a speculative scenario by upscaling the default QGP and hadronic rates around the pseudo-critical region.

nucl-th↗

arXiv2014

Study of e$^+$e$^-$ $\rightarrow \text{p} \overline{\text{p}}π^0$ in the Vicinity of the $ψ\text{(3770)}$

The process $e^+e^-\rightarrow p\overline{p}π^0$ has been studied by analyzing data collected at $\sqrt{s}=3.773$ GeV, at $\sqrt{s}=3.650$ GeV, and during a $ψ(3770)$ line shape scan with the BESIII detector at the BEPCII collider. The Born cross section of $p \overline{p} π^0$ in the vicinity of the $ψ(3770)$ is measured and the Born cross section of $ψ(3770)\rightarrow p \overline{p} π^0$ is extracted considering interference between resonant and continuum production amplitudes. Two solutions with the same probability and a significance of 1.5$σ$ are found, and the Born cross section of $ψ(3770)\rightarrow p \overline{p} π^0$ is determined to be less than 0.22 pb at 90% confidence level and $33.8\pm1.8\pm2.1$ pb, respectively. Using the estimated cross section and a constant decay amplitude approximation, the cross section $σ(p\overline{p} \rightarrow ψ(3770) π^0)$ is calculated for the kinematic situation of the planned $\overline{\text{P}}\text{ANDA}$ experiment. The maximum cross section corresponding to the two solutions is expected to be less than $0.79$ nb at 90% confidence level and $122\pm10$ nb at a center of mass energy of 5.26 GeV.

hep-ex↗

arXiv2014

Study of $e^+e^- \rightarrow p\bar{p}$ in the vicinity of $ψ(3770)$

Using 2917 $\rm{pb}^{-1}$ of data accumulated at 3.773~$\rm{GeV}$, 44.5~$\rm{pb}^{-1}$ of data accumulated at 3.65~$\rm{GeV}$ and data accumulated during a $ψ(3770)$ line-shape scan with the BESIII detector, the reaction $e^+e^-\rightarrow p\bar{p}$ is studied considering a possible interference between resonant and continuum amplitudes. The cross section of $e^+e^-\rightarrowψ(3770)\rightarrow p\bar{p}$, $σ(e^+e^-\rightarrowψ(3770)\rightarrow p\bar{p})$, is found to have two solutions, determined to be ($0.059\pm0.032\pm0.012$) pb with the phase angle $ϕ= (255.8\pm37.9\pm4.8)^\circ$ ($<$0.11 pb at the 90% confidence level), or $σ(e^+e^-\rightarrowψ(3770)\rightarrow p\bar{p}) = (2.57\pm0.12\pm0.12$) pb with $ϕ= (266.9\pm6.1\pm0.9)^\circ$ both of which agree with a destructive interference. Using the obtained cross section of $ψ(3770)\rightarrow p\bar{p}$, the cross section of $p\bar{p}\rightarrow ψ(3770)$, which is useful information for the future PANDA experiment, is estimated to be either ($9.8\pm5.7$) nb ($<17.2$ nb at 90% C.L.) or $(425.6\pm42.9)$ nb.

hep-ex↗

arXiv2014

Observation of $χ_{c1}$ decays into vector meson pairs $ϕϕ$, $ωω$, and $ωϕ$

Decays of $χ_{c1}$ to vector meson pairs $ϕϕ$, $ωω$ and $ωϕ$ are observed for the first time using $(106\pm4)\times 10^6$ $\psip$ events accumulated at the BESIII detector at the BEPCII $e^+e^-$ collider. The branching fractions are measured to be $(4.4\pm 0.3\pm 0.5)\times 10^{-4}$, $(6.0\pm 0.3\pm 0.7)\times 10^{-4}$, and $(2.2\pm 0.6\pm 0.2)\times 10^{-5}$, for $χ_{c1}\to ϕϕ$, $ωω$, and $ωϕ$, respectively. The observation of $χ_{c1}$ decays into a pair of vector mesons $ϕϕ$, $ωω$ and $ωϕ$ indicates that the hadron helicity selection rule is significantly violated in $χ_{cJ}$ decays. In addition, the measurement of $χ_{cJ}\to ωϕ$ gives the rate of doubly OZI-suppressed decay. Branching fractions for $χ_{c0}$ and $χ_{c2}$ decays into other vector meson pairs are also measured with improved precision.

hep-ex↗

arXiv2014

Measurement of $χ_{cJ}$ decaying into $η^{\prime}K^+K^-$

Using $(106.41\pm 0.86) \times 10^{6}$ $ψ(3686)$ events collected with the BESIII detector at BEPCII, we study for the first time the decay $χ_{cJ}\toη'K^+K^-$, where $η'\toγρ^{0}$ and $η'\toηπ^+π^-$. A partial wave analysis in the covariant tensor amplitude formalism is performed for the decay $χ_{c1}\toη'K^+K^-$. Intermediate processes $χ_{c1}\toη' f_0(980)$, $χ_{c1}\toη' f_0(1710)$, $χ_{c1}\toη' f_2'(1525)$ and $χ_{c1}\to K^*_0(1430)^{\pm}K^{\mp}$ ($K^*_0(1430)^{\pm}\toη' K^{\pm}$) are observed with statistical significances larger than 5$σ$, and their branching fractions are measured.

hep-ex↗

arXiv2014

Independent Measurement of Theta13 via Neutron Capture on Hydrogen at Daya Bay

A new measurement of the $θ_{13}$ mixing angle has been obtained at the Daya Bay Reactor Neutrino Experiment via the detection of inverse beta decays tagged by neutron capture on hydrogen. The antineutrino events for hydrogen capture are distinct from those for gadolinium capture with largely different systematic uncertainties, allowing a determination independent of the gadolinium-capture result and an improvement on the precision of $θ_{13}$ measurement. With a 217-day antineutrino data set obtained with six antineutrino detectors and from six 2.9 GW$_{th}$ reactors, the rate deficit observed at the far hall is interpreted as $\sin^22θ_{13}=0.083\pm0.018$ in the three-flavor oscillation model. When combined with the gadolinium-capture result from Daya Bay, we obtain $\sin^22θ_{13}=0.089\pm0.008$ as the final result for the six-antineutrino-detector configuration of the Daya Bay experiment.

hep-ex↗

arXiv2014

Precision Measurement of the Mass of the $τ$ Lepton

An energy scan near the $τ$ pair production threshold has been performed using the BESIII detector. About $24$ pb$^{-1}$ of data, distributed over four scan points, was collected. This analysis is based on $τ$ pair decays to $ee$, $eμ$, $eh$, $μμ$, $μh$, $hh$, $eρ$, $μρ$ and $πρ$ final states, where $h$ denotes a charged $π$ or $K$. The mass of the $τ$ lepton is measured from a maximum likelihood fit to the $τ$ pair production cross section data to be $m_τ = (1776.91\pm0.12 ^{+0.10}_{-0.13}$) MeV/$c^2$, which is currently the most precise value in a single measurement.

hep-ex↗

arXiv2014

Search for the radiative transitions $ψ(3770)\toγη_c$ and $γη_c(2S)$

By using a 2.92 fb$^{-1}$ data sample taken at $\sqrt{s} = 3.773$ GeV with the BESIII detector operating at the BEPCII collider, we search for the radiative transitions $ψ(3770)\toγη_c$ and $γη_c(2S)$ through the hadronic decays $η_c(η_c(2S))\to K^0_SK^\pmπ^\mp$. No significant excess of signal events above background is observed. We set upper limits at a 90% confidence level for the product branching fractions to be $\mathcal{B}(ψ(3770)\toγη_c)\times \mathcal{B}(η_c\to K^0_SK^\pmπ^\mp) < 1.6\times10^{-5}$ and $\mathcal{B}(ψ(3770)\toγη_c(2S))\times \mathcal{B}(η_c(2S)\to K^0_SK^\pmπ^\mp) < 5.6\times10^{-6}$. Combining our result with world-average values of $\mathcal{B}(η_c(η_c(2S))\to K^0_SK^\pmπ^\mp)$, we find the branching fractions $\mathcal{B}(ψ(3770)\toγη_c) < 6.8\times10^{-4}$ and $\mathcal{B}(ψ(3770)\toγη_c(2S)) < 2.0\times10^{-3}$ at a 90% confidence level.

hep-ex↗

arXiv2014

Measurement of the $D\to K^-π^+$ strong phase difference in $ψ(3770)\to D^0\overline{D}{}^0$

We study $D^0\overline{D}{}^0$ pairs produced in $e^+e^-$ collisions at $\sqrt{s}=3.773$ GeV using a data sample of 2.92 fb$^{-1}$ collected with the BESIII detector. We measure the asymmetry $\mathcal{A}^{CP}_{Kπ}$ of the branching fractions of $D \to K^-π^+$ in $CP$-odd and $CP$-even eigenstates to be $(12.7\pm1.3\pm0.7)\times10^{-2}$. $\mathcal{A}^{CP}_{Kπ}$ can be used to extract the strong phase difference $δ_{Kπ}$ between the doubly Cabibbo-suppressed process $\overline{D}{}^{0}\to K^-π^+$ and the Cabibbo-favored process $D^0\to K^- π^+$. Using world-average values of external parameters, we obtain $\cosδ_{Kπ} = 1.02\pm0.11\pm0.06\pm0.01$. Here, the first and second uncertainties are statistical and systematic, respectively, while the third uncertainty arises from the external parameters. This is the most precise measurement of $δ_{Kπ}$ to date.

hep-ex↗

arXiv2014

Precision measurements of $B(D^+ \rightarrow μ^+ ν_μ)$, the pseudoscalar decay constant $f_{D^+}$, and the quark mixing matrix element $|V_{\rm cd}|$

We report a measurement of the branching fraction $B(D^+ \rightarrow μ^+ ν_μ) = [3.71 \pm 0.19 (\rm stat) \pm 0.06 (\rm sys)]\times 10^{-4}$ based on 2.92 ${\rm fb^{-1}}$ of data accumulated at $\sqrt{s}=3.773$ GeV with the BESIII detector at the BEPCII collider. This measurement, in conjunction with the Cabibbo-Kobayashi-Maskawa matrix element $|V_{\rm cd}|$ determined from a global Standard Model fit, implies a value for the weak decay constant $f_{D^+}=(203.2 \pm 5.3 \pm 1.8)$ MeV. Additionally, using this branching fraction measurement together with a Lattice QCD prediction for $f_{D^+}$, we find $|V_{\rm cd}|=0.2210\pm 0.0058 \pm 0.0047$. In either case, these are the most precise results for these quantities to date.

hep-ex↗

arXiv2014

Measurement of the branching fraction for $ψ(3686)\toωK^+ K^-$

With $1.06\times 10^8$ $ψ(3686)$ events collected with the BESIII detector, the branching fraction of $ψ(3686) \to ωK^+ K^-$ is measured to be $(1.54 \pm 0.04 \pm 0.11) \times 10^{-4}$. This is the most precise result to date, due to the largest $ψ(3686)$ sample, improved signal reconstruction efficiency, good simulation of the detector performance, and a more accurate knowledge of the continuum contribution. Using the branching fraction of $J/ψ\to ωK^+ K^-$, the ratio $\mathcal{B}(ψ(3868) \to K^+K^-) / \mathcal{B}(J/ψ\to K^+K^-)$ is determined to be $(18.4 \pm 3.7)\,\%$. This constitutes a significantly improved test of the $12\,\%$ rule, with the uncertainty now dominated by the $J/ψ$ branching fraction.

hep-ex↗

arXiv2014

Observation of Electromagnetic Dalitz decays J/ψ\to P e^+e^-

Based on a sample of (225.3\pm2.8)\times 10^{6} J/ψevents collected with the BESIII detector, the electromagnetic Dalitz decays of J/ψ\to P e^+e^-(P=η'/η/π^0) are studied. By reconstructing the pseudoscalar mesons in various decay modes, the decays J/ψ\to η' e^+e^-, J/ψ\to ηe^+e^- and J/ψ\to π^0 e^+e^- are observed for the first time. The branching fractions are determined to be \mathcal{B}(J/ψ\to η' e^+e^-) = (5.81\pm0.16\pm0.31)\times10^{-5}, \mathcal{B}(J/ψ\to ηe^+e^-) = (1.16\pm0.07\pm0.06)\times10^{-5}, and \mathcal{B}(J/ψ\to π^0 e^+e^-)=(7.56\pm1.32\pm0.50)\times10^{-7}, where the first errors are statistical and the second ones systematic.

hep-ex↗

arXiv2014

PandaX: A Liquid Xenon Dark Matter Experiment at CJPL

PandaX is a large upgradable liquid-xenon detector system that can be used for both direct dark-matter detection and $^{136}$Xe double-beta decay search. It is located in the Jinping Deep-Underground Laboratory in Sichuan, China. The detector operates in dual-phase mode, allowing detection of both prompt scintillation, and ionization charge through proportional scintillation. The central time projection chamber will be staged, with the first stage accommodating a target mass of about 120\,kg. In stage II, the target mass will be increased to about 0.5\,ton. In the final stage, the detector can be upgraded to a multi-ton target mass. In this paper a detailed description of the stage-I detector design and performance results established during the commissioning phase is presented.

physics.ins-det↗

arXiv2014

Observation of $η^{\prime}\toπ^{+}π^{-}π^{+}π^{-}$ and $η^{\prime}\toπ^{+}π^{-}π^{0}π^{0}$

Using a sample of $1.3\times 10^9$ $J/ψ$ events collected with the BESIII detector, we report the first observation of $η^{\prime}\toπ^{+}π^{-}π^{+}π^{-}$ and $η^{\prime}\toπ^{+}π^{-}π^{0}π^{0}$. The measured branching fractions are $\mathcal{B}$($η^{\prime}\toπ^{+}π^{-}π^{+}π^{-}$) = $(8.53\pm0.69({\rm stat.})\pm0.64({\rm syst.}))\times10^{-5}$ and $\mathcal{B}$($η^{\prime}\toπ^{+}π^{-}π^{0}π^{0}$) = $(1.82\pm0.35({\rm stat.})\pm0.18({\rm syst.}))\times10^{-4}$, which are consistent with theoretical predictions based on a combination of chiral perturbation theory and vector-meson dominance.

hep-ex↗

arXiv2014

Search for the rare decays $J/ψ\to D_s^-ρ^+$ and $J/ψ\to \overline{D}{}^0\overline{K}{}^{\ast0}$

A search for the rare decays of $J/ψ\to D_s^-ρ^+ + c.c.$ and $J/ψ\to \overline{D}{}^0\overline{K}{}^{\ast0} + c.c.$ is performed with a data sample of 225.3 million $J/ψ$ events collected with the BESIII detector. No evident signal is observed. Upper limits on the branching fractions are determined to be $\mathcal{B}(J/ψ\to D_s^-ρ^+ + c.c.) < 1.3 \times 10^{-5}$ and $\mathcal{B}(J/ψ\to \overline{D}{}^0\overline{K}{}^{\ast0} + c.c.) < 2.5 \times 10^{-6}$ at the $90\%$ confidence level.

hep-ex↗