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Han, S.

Publications and source records attributed to Han, S..

At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Constraining the mass and radius of neutron stars in globular clusters

In this paper, we analyse observations of eight quiescent low-mass X-ray binaries in globular clusters and combine them to determine the neutron star mass–radius curve and the equation of state of dense matter. We determine the effect that several uncertainties may have on our results, including uncertainties in the distance, the atmosphere composition, the neutron star maximum mass, the neutron star mass distribution, the possible presence of a hotspot on the neutron star surface, and the prior choice for the equation of state of dense matter. The distance uncertainty is implemented in a new Gaussian blurring method that can be directly applied to the probability distribution over mass and radius. We find that the radius of a 1.4 solar mass neutron star is most likely from 10 to 14 km and that tighter constraints are only possible with stronger assumptions about the nature of the neutron stars, the systematics of the observations, or the nature of dense matter. Finally, strong phase transitions in the equation of state are preferred, and in this case, the radius is likely smaller than 12 km. However, radii larger than 12 km are preferred if the neutron stars have uneven temperature distributions.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Search for ψ ( 3686 ) → γ η c ( η ( 1405 ) ) → γ π + π - π 0

Using a sample of 448.1×10 6 ψ(3686) events collected with the BESIII detector, a search for the isospin violating decay η c → π⁺π⁻π⁰ via ψ(3686) → γ η c is presented. No signal is observed, and the upper limit on B(ψ(3686) → γ η c ) × B( η c → π⁺π⁻π⁰) is determined to be 1.6 × 10 -6 at the 90% confidence level. In addition, a search for η (1405) → f 0 (980)π 0 in (3686) radiative decays is performed. No signal is observed, and the branching fraction B(ψ(3686) → γη(1405))×B( η (1405) → f 0 (980)π 0 ) × B(f 0 (980) → π⁺π⁻ is calculated to be less than 5.0 × 10 -7 at the 90% confidence level.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Branching fraction measurement of J / ψ → K S K L and search for J / ψ → K S K S

Using a sample of 1.31×10 9 J/ψ events collected with the BESIII detector at the BEPCII collider, we study the decays of J/ψ→ K S K L and K S K S . The branching fraction of J/ψ→ K S K L is determined to be B(J/ψ→ K S K L ) = (1:93 0:01 (stat:) 0:05 (syst:))×10 -4 , which signi cantly improves on previous measurements. No clear signal is observed for the J/ψ→ K S K S process, and the upper limit at the 95% con dence level for its branching fraction is determined to be B(J= ! K S K S ) < 1:4×10 -8 , which improves on the previous searches by 2 orders in magnitude and reaches the order of the Einstein-Podolsky-Rosen expectation.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Search for the rare decays J / ψ → D 0 e + e - + c . c . and ψ ( 3686 ) → D 0 e + e - + c . c .

Using the data samples of (1310.6 ± 7.2) × 10 6 J / ψ events and (448.1 ± 2.9) × 106 (3686) events collected with the BESIII detector, we search for the rare decays J / ψ → D 0 e + e - + c.c. and (3686) → D 0 e + e - + c.c.. No significant signals are observed and the corresponding upper limits on the branching fractions at the 90% confidence level are determined to be B( J / ψ → D0e+e- + c.c.) < 8.5 × 10 -8 and B( (3686) → D0e+e- + c.c.) < 1.4 × 10 -7 , respectively. Our limit on B( J / ψ → D 0 e + e - + c.c.) is more stringent by two orders of magnitude than the previous results, and the B( (3686) → D 0 e + e - + c.c.) is measured for the first time.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Observation of the helicity-selection-rule suppressed decay of the χ c 2 charmonium state

The decays of χ c 2 → K + K - π 0 , K S K ± π ∓ , and π + π - π 0 are studied with the ψ ( 3686 ) data samples collected with the Beijing Spectrometer (BESIII). For the first time, the branching fractions of χ c 2 → K*$\bar{K}$ , χ c 2 → $a_2^±$(1320)π ∓ /$a_2^0$(1320)π 0 , and χ c 2 → ρ( 770 ) ± π ∓ are measured. Here, K*$\bar{K}$ denotes both K* ± K ∓ and its isospin-conjugated process K* 0 $\bar{K}$ 0 +c.c., and K* denotes the resonances K*(892), $K_2^*$(1430), and $K_3^*$(1780). The observations indicate a strong violation of the helicity selection rule in χ c 2 decays into vector and pseudoscalar meson pairs. The measured branching fractions of χ c 2 → K*(892)$\bar{K}$ are more than ten times larger than the upper limit of χ c 2 → ρ ( 770 ) ± π ∓ , which is so far the first direct observation of a significant U -spin symmetry breaking effect in charmonium decays.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗