0000000000132086
AUTHOR
Hai Yu
showing 16 related works from this author
Systematic study of charged-pion and kaon femtoscopy in Au + Au collisions atsNN=200GeV
2015
We present a systematic study of charged-pion and kaon interferometry in Au + Au collisions at root s(NN) = 200 GeV. The kaon mean source radii are found to be larger than pion radii in the outward and longitudinal directions for the same transverse mass; this difference increases for more central collisions. The azimuthal-angle dependence of the radii was measured with respect to the second-order event plane and similar oscillations of the source radii were found for pions and kaons. Hydrodynamic models qualitatively describe the similar oscillations of the mean source radii for pions and kaons, but they do not fully describe the transverse-mass dependence of the oscillations.
Observation of a Charged(DD¯*)±Mass Peak ine+e−→πDD¯*ats=4.26 GeV
2014
We report on a study of the process e(+)e(-) -> pi(+/-) (D (D) over bar*)(-/+) at root s = 4.26 GeV using a 525 pb(-1) data sample collected with the BESIII detector at the BEPCII storage ring. A distinct charged structure is observed in the (D (D) over bar*)(-/+) invariant mass distribution. When fitted to a mass- dependent- width Breit- Wigner line shape, the pole mass and width are determined to be M-pole (3883: 9 +/- 1.5 (stat) +/- 4.2 dsyst__ MeV= c(2) and Gamma(pole) = (24: 8 +/- 3.3 (stat) +/- 11: 0 (syst)) MeV. The mass and width of the structure, which we refer to as Z(c)(3885), are 2 sigma and 1 sigma, respectively, below those of the Z(c)(3900) -> pi(+/-) J/psi peak observed by B…
Search for the weak decays J/ψ→Ds(*)−e+νe+c.c.
2014
Using a sample of 2.25 x 10(8) J/psi events collected with the BESIII detector at the BEPCII collider, we search for the J/psi semileptonic weak decay J/psi -> D-s(-) e(+)nu(e) +c.c. with a much higher sensitivity than previous searches. We also perform the first search for J/psi -> D-s(*-) e(+) nu(e) + c.c. No significant excess of a signal above background is observed in either channel. At the 90% confidence level, the upper limits are determined to be B(J/psi -> D-s(-) e(+) nu(e) + c.c.) D-s*(-) e(+) nu(e) + c.c.) < 1.8 x 10(-6), respectively. Both are consistent with Standard Model predictions.
Search forηandη′invisible decays inJ/ψ→ϕηandϕη′
2013
Using a sample of (225.3 +/- 2.8) x 10(6) J/psi decays collected with the BESIII detector at BEPCII, searches for invisible decays of eta and eta ' in J/psi -> phi eta and phi eta ' are performed. Decays of phi -> K+K- are used to tag the eta and eta ' decays. No signals above background are found for the invisible decays, and upper limits at the 90% confidence level are determined to be 2.6 x 10(-4) for the ratio B(eta -> invisible)/B(eta ->gamma gamma) and 2.4 x 10(-2) for B(eta '-> invisible)/B(eta '->gamma gamma). These limits may be used to constrain light dark matter particles or spin-1 U bosons. DOI: 10.1103/PhysRevD.87.012009
Observation of a Charged Charmoniumlike Structure ine+e−→π+π−J/ψats=4.26 GeV
2013
We study the process e(+)e(-) -> 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 +/- 1.9 +/- 3.7) pb, consistent with the production of the Y(4260). We observe a structure at around 3.9 GeV/c(2) in the pi(+/-) 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 pi(+/-) J/psi invariant mass spectrum, neglecting interference, results in a mass of (3899.0 +/- 3.6 +/- 4.9) MeV/c(2) and a width…
Search forC-parity violation inJ/ψ→γγandγϕ
2014
Using 1.06 x 10(8) psi(3686) events recorded in e(+)e(-) collisions at root s = 3.686 GeV with the BESIII at the BEPCII collider, we present searches for C-parity violation in J/psi -> gamma gamma and gamma phi decays via psi(3686) -> J/psi pi(+)pi(-). No significant signals are observed in either channel. Upper limits on the branching fractions are set to be B(J/psi -> gamma gamma) gamma phi) < 1.4 x 10(-6) at the 90% confidence level. The former is one order of magnitude more stringent than the previous upper limit, and the latter represents the first limit on this decay channel.
Measurements of baryon pair decays of chi(cJ) mesons
2013
Using 106 $\times 10^{6}$ $\psi^{\prime}$ decays collected with the BESIII detector at the BEPCII, three decays of $\chi_{cJ}$ ($J=0,1,2$) with baryon pairs ($\llb$, $\ssb$, $\SSB$) in the final state have been studied. The branching fractions are measured to be $\cal{B}$$(\chi_{c0,1,2}\rightarrow\Lambda\bar\Lambda) =(33.3 \pm 2.0 \pm 2.6)\times 10^{-5}$, $(12.2 \pm 1.1 \pm 1.1)\times 10^{-5}$, $(20.8 \pm 1.6 \pm 2.3)\times 10^{-5}$; $\cal{B}$$(\chi_{c0,1,2}\rightarrow\Sigma^{0}\bar\Sigma^{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}$$(\chi_{c0,1,2}\rightarrow\Sigma^{+}\bar\Sigma^{-})$ = $(45.4 \pm…
Observation of a Charged Charmoniumlike StructureZc(4020)and Search for theZc(3900)ine+e−→π+π−hc
2013
We study e(+)e(-) -> pi(+) pi(-)h(c) at center-of-mass energies from 3.90 to 4.42 GeV by using data samples collected with the BESIII detector operating at the Beijing Electron Positron Collider. The Born cross sections are measured at 13 energies and are found to be of the same order of magnitude as those of e(+)e(-) -> pi(+) pi(-) J/Psi but with a different line shape. In the pi(+/-)h(c) mass spectrum, a distinct structure, referred to as Z(c)(4020) is observed at 4. 02 GeV/c(2). The Z(c)(4020) carries an electric charge and couples to charmonium. A fit to the pi(+/-)h(c) invariant mass spectrum, neglecting possible interferences, results in a mass of (4022.9 +/- 0.8 +/- 2.7) MeV/c(2) and…
Search for baryonic decays ofψ(3770)andψ(4040)
2013
By analyzing data samples of 2.9 fb(-1) collected at root s = 3.773 GeV, 482 pb(-1) collected at root s = 4.009 GeV and 67 pb(-1) collected at root 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 psi(3770) and psi(4040) decay to baryonic final states, including Lambda(Lambda) over bar pi(+)pi(-), Lambda(Lambda) over bar pi(0), Lambda(Lambda) over bar eta , Sigma(0)(Sigma) over bar (0) and Xi(0) (Xi) over bar (0) decays. None are observed, and upper limits are set at the 90% confidence level.
Partial wave analysis of ψ(2S)→ppˉη
2013
Using a sample of 1.06 x 10(8) psi(2) events collected with the BESIII detector at BEPCII, the decay psi(2S) -> p (p) over bar eta is studied. A partial wave analysis determines that the intermediate state N(1535) with a mass of 1524 +/- 5(-4)(+10) MeV/c(2) and a width of 130(-24-10)(+27+57) MeV/c(2) is dominant in the decay; the product branching fraction is determined to be B(psi(2S) -> N(1535)(p) over bar x B(N(1535) -> p eta + c.c. = 5.2 +/- 0.3(-1.2)(+3.2)) x 10(-5). Furthermore, the branching fraction of psi(2S) -> p (p) over bar eta is measured to be (6.4 +/- 0.2 +/- 0.6) x 10(-5). Here, the first error is statistical and the second is systematic.
Amplitude analysis of theD+→KS0π+π0Dalitz plot
2014
We perform an analysis of the D+ -> K-S(0)pi + (0)(pi) Dalitz plot using a data set of 2.92 fb(-1) of e(+) e(-) collisions at the (3770) mass accumulated by the BESIII experiment, in which 166694 candidate events are selected with a background of 15.1%. The Dalitz plot is found to be well represented by a combination of six quasitwo- body decay channels [k(SP)(0)(+) (1450)(+,) ] plus a small nonresonant component. Using the fit fractions from this analysis, partial branching ratios are updated with higher precision than previous measurements.
Dielectron production in Au + Au collisions atsNN=200GeV
2016
We present measurements of e+e- production at midrapidity in Au+Au collisions at sNN=200 GeV. The invariant yield is studied within the PHENIX detector acceptance over a wide range of mass (mee<5 GeV/c2) and pair transverse momentum (pT<5 GeV/c) for minimum bias and for five centrality classes. The e+e- yield is compared to the expectations from known sources. In the low-mass region (mee=0.30-0.76 GeV/c2) there is an enhancement that increases with centrality and is distributed over the entire pair pT range measured. It is significantly smaller than previously reported by the PHENIX experiment and amounts to 2.3±0.4(stat)±0.4(syst)±0.2(model) or to 1.7±0.3(stat)±0.3(syst)±0.2(model) for min…
Measurement of thee+e−→ηJ/ψcross section and search fore+e−→π0J/ψat center-of-mass energies between 3.810 and 4.600 GeV
2015
Using data samples collected with the BESIII detector operating at the BEPCII collider at 17 center-of-mass energies from 3.810 to 4.600 GeV, we perform a study of e(+)e(-) -> eta J/psi and pi(0)J/psi The Born cross sections of these two processes are measured at each center-of-mass energy. The measured energy-dependent Born cross section for e(+)e(-) -> eta J/psi shows an enhancement around 4.2 GeV. The measurement is compatible with an earlier measurement by Belle.
Observation of a Charged Charmoniumlike Structure ine+e−→(D*D¯*)±π∓ats=4.26 GeV
2014
We study the process e(+)e(-) -> (D* (D) over bar*)(+/-)pi(-/+) at a center-of-mass energy of 4.26 GeV using a 827 pb(-1) data sample obtained with the BESIII detector at the Beijing Electron Positron Collider. Based on a partial reconstruction technique, the Born cross section is measured to be (137 +/- 9 +/- 15) pb. We observe a structure near the (D* (D) over bar*)(+/-) threshold in the pi(-/+) recoil mass spectrum, which we denote as the Z(c)(+/-) (4025). The measured mass and width of the structure are (4026.3 +/- 2.6 +/- 3.7) MeV/c(2) and (24.8 +/- 5.6 +/- 7.7) MeV, respectively. Its production ratio sigma(e(+)e(-) -> Z(c)(+/-)(4025)pi(-/+)-> (D* (D) over bar*)(+/-)pi(-/+)/sigma(e(+)e…
Search for the Lepton Flavor Violation Process J/ψ→eμ at BESIII
2013
We search for the lepton-flavor-violating decay of the $J/\psi$ into an electron and a muon using $(225.3\pm2.8)\times 10^{6}$ $J/\psi$ 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/\psi \to e\mu)< 1.5 \times 10^{-7}$ (90% C.L.) is obtained.
Measurements of Elliptic and Triangular Flow in High-MultiplicityHe3+AuCollisions atsNN=200 GeV
2015
We present the first measurement of elliptic ($v_2$) and triangular ($v_3$) flow in high-multiplicity $^{3}$He$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV. Two-particle correlations, where the particles have a large separation in pseudorapidity, are compared in $^{3}$He$+$Au and in $p$$+$$p$ collisions and indicate that collective effects dominate the second and third Fourier components for the correlations observed in the $^{3}$He$+$Au system. The collective behavior is quantified in terms of elliptic $v_2$ and triangular $v_3$ anisotropy coefficients measured with respect to their corresponding event planes. The $v_2$ values are comparable to those previously measured in $d$$+$Au collis…