Test of local realism via entangled $$\Lambda \bar{\Lambda }$$ system
Not provided.
Science & Technology - Other Topics↗
Engineering topics
Chang, W.
Publications and source records attributed to Chang, W..
Extracting the femtometer structure of strange baryons using the vacuum polarization effect
Abstract One of the fundamental goals of particle physics is to gain a microscopic understanding of the strong interaction. Electromagnetic form factors quantify the structure of hadrons in terms of charge and magnetization distributions. While the nucleon structure has been investigated extensively, data on hyperons are still scarce. It has recently been demonstrated that electron-positron annihilations into hyperon-antihyperon pairs provide a powerful tool to investigate their inner structure. We present a method useful for hyperon-antihyperon pairs of different types which exploits the cross section enhancement due to the effect of vacuum polarization at theJ/ψresonance. Using the 10 billionJ/ψevents collected with the BESIII detector, this allows a precise determination of the hyperon structure function. The result is essentially a precise snapshot of the$$\bar{\Lambda }{\Sigma }^{0}\,(\Lambda {\bar{\Sigma }}^{0})$$ Λ ¯ Σ 0 ( Λ Σ ¯ 0 ) transition process, encoded in the transition form factor ratio and phase. Their values are measured to beR = 0.860 ± 0.029(stat.) ± 0.015(syst.),$$\Delta {\Phi }_{\bar{\Lambda }{\Sigma }^{0}}=(1.011\pm 0.094({{\rm{stat.}}})\pm 0.010({{\rm{syst.}}}))\,{{\rm{r}}}ad$$ Δ Φ Λ ¯ Σ 0 = ( 1.011 ± 0.094 ( stat. ) ± 0.010 ( syst. ) ) r a d and$$\Delta {\Phi }_{\Lambda {\bar{\Sigma }}^{0}}=(2.128\pm 0.094({{\rm{stat.}}})\pm 0.010({{\rm{syst.}}}))\,{{\rm{r}}}ad$$ Δ Φ Λ Σ ¯ 0 = ( 2.128 ± 0.094 ( stat. ) ± 0.010 ( syst. ) ) r a d . Furthermore, charge-parity (CP) breaking is investigated in this reaction and found to be consistent with CP symmetry.
Science & Technology - Other Topics↗
Observation of the semileptonic decays $$ {\textrm{D}}^0\to {\textrm{K}}_{\textrm{S}}^0{\pi}^{-}{\pi}^0{\textrm{e}}^{+}{\nu}_{\textrm{e}} $$ and $$ {\textrm{D}}^{+}\to {\textrm{K}}_{\textrm{S}}^0{\pi}^{+}{\pi}^{-}{\textrm{e}}^{+}{\nu}_{\textrm{e}} $$
Abstract By analyzinge + e − annihilation data corresponding to an integrated luminosity of 2.93 fb −1 collected at a center-of-mass energy of 3.773 GeV with the BESIII detector, the first observation of the semileptonic decays$$ {D}^0\to {K}_S^0{\pi}^{-}{\pi}^0{e}^{+}{\nu}_e $$ D 0 → K S 0 π − π 0 e + ν e and$$ {D}^{+}\to {K}_S^0{\pi}^{+}{\pi}^{-}{e}^{+}{\nu}_e $$ D + → K S 0 π + π − e + ν e is reported. In the hypothesis that all events correspond toK 1 (1270) decays, the branching fractions are measured to be$$ \mathcal{B}\left({D}^0\to {K}_1{(1270)}^{-}\left(\to {K}_S^0{\pi}^{-}{\pi}^0\right){e}^{+}{\nu}_e\right)=\left({1.69}_{-0.46}^{+0.53}\pm 0.15\right)\times {10}^{-4} $$ B D 0 → K 1 1270 − → K S 0 π − π 0 e + ν e = 1.69 − 0.46 + 0.53 ± 0.15 × 10 − 4 and$$ \mathcal{B}\left({D}^{+}\to {\overline{K}}_1{(1270)}^0\left(\to {K}_S^0{\pi}^{+}{\pi}^{-}\right){e}^{+}{\nu}^e\right)=\left({1.47}_{-0.40}^{+0.45}\pm 0.14\right)\times {10}^{-4} $$ B D + → K ¯ 1 1270 0 → K S 0 π + π − e + ν e = 1.47 − 0.40 + 0.45 ± 0.14 × 10 − 4 with statistical significance of 5.4σand 5.6σ, respectively. When combined with measurements of theK 1 (1270)→ K + π − πdecays, the absolute branching fractions are determined to be$$ \mathcal{B}\left({D}^0\to {K}_1{(1270)}^{-}{e}^{+}{\nu}_e\right)=\left({1.08}_{-0.13-0.10}^{+0.14+0.08}\pm 0.21\right)\times {10}^{-3} $$ B D 0 → K 1 1270 − e + ν e = 1.08 − 0.13 − 0.10 + 0.14 + 0.08 ± 0.21 × 10 − 3 and$$ \mathcal{B}\left({D}^{+}\to {\overline{K}}_1{(1270)}^0{e}^{+}{\nu}_e\right)=\left({1.70}_{-0.23}^{+0.26}\pm 0.13\pm 0.35\right)\times {10}^{-3} $$ B D + → K ¯ 1 1270 0 e + ν e = 1.70 − 0.23 + 0.26 ± 0.13 ± 0.35 × 10 − 3 . The first and second uncertainties are statistical and systematic, respectively, and the third uncertainties originate from the assumed branching fractions of theK 1 (1270)→ Kππdecays.
Physics↗
Amplitude analysis of the decays and *
Abstract Usingannihilation data corresponding to an integrated luminosity of 2.93taken at the center-of-mass energyGeV with the BESIII detector, a joint amplitude analysis is performed on the decaysand(non-η). The fit fractions of individual components are obtained, and large interferences among the dominant components of the decays,,, andare observed in both channels. With the obtained amplitude model, the-even fractions ofand(non-η) are determined to be% and%, respectively. The branching fractions ofand(non-η) are measured to be% and%, respectively. The amplitude analysis provides an important model for the binning strategy in measuring the strong phase parameters ofwhen used to determine the CKM anglevia thedecay.
Physics↗
Measurement of e+e− → ωη′ cross sections at $$ \sqrt{s} $$ = 2.000 to 3.080 GeV
Abstract We measured the Born cross sections for the processe + e − →ωη′ at 22 center-of-mass energies from 2.000 to 3.080 GeV with the BESIII detector at the BEPCII collider. We observed a resonant structure with a statistical significance of 9.6σ. A Breit-Wigner fit determines its mass to beM R = (2153±30±31) MeV/c 2 and its width to be Γ R = (167±77±7) MeV, where the first uncertainties are statistical and the second are systematic.
Physics↗
Study of η′ → π+π−l+l− decays at BESIII
Abstract With a sample of (10087±44)×10 6 J/ψevents accumulated with the BESIII detector, we analyze the decaysη′→ π + π − l + l − (l=e, μ) via the processJ/ψ → γη′. The branching fractions are measured to be$$ \mathcal{B} $$ B (η′→ π + π − e + e − ) = (2.45±0.02(stat.)±0.08(syst.))×10 −3 and$$ \mathcal{B} $$ B (η′→ π + π − μ + μ − ) = (2.16±0.12(stat.)±0.06(syst.))×10 −5 , and the ratio is$$ \frac{\mathcal{B}\left({\eta}^{\prime}\to {\pi}^{+}{\pi}^{-}{e}^{+}{e}^{-}\right)}{\mathcal{B}\left({\eta}^{\prime}\to {\pi}^{+}{\pi}^{-}{\mu}^{+}{\mu}^{-}\right)}=113.4\pm 0.9\left(\textrm{stat}.\right)\pm 3.7\left(\textrm{syst}.\right) $$ B η ′ → π + π − e + e − B η ′ → π + π − μ + μ − = 113.4 ± 0.9 stat . ± 3.7 syst . . In addition, by combining theη′ →π + π − e + e − andη′ →π + π − μ + μ − decays, the slope parameter of the electromagnetic transition form factor is measured to beb η′ = 1.30 ± 0.19 (GeV/c 2 ) −2 , which is consistent with previous measurements from BESIII and theoretical predictions from the VMD model. The asymmetry in the angle between theπ + π − andl + l − decay planes, which has the potential to reveal theCP-violation originating from an unconventional electric dipole transition, is also investigated. The asymmetry parameters are determined to be$$ {\mathcal{A}}_{CP}\left({\eta}^{\prime}\to {\pi}^{+}{\pi}^{-}{e}^{+}{e}^{-}\right)=\left(-0.21\pm 0.73\left(\textrm{stat}.\right)\pm 0.01\left(\textrm{syst}.\right)\right)\% $$ A CP η ′ → π + π − e + e − = − 0.21 ± 0.73 stat . ± 0.01 syst . % and$$ {\mathcal{A}}_{CP}\left({\eta}^{\prime}\to {\pi}^{+}{\pi}^{-}{\mu}^{+}{\mu}^{-}\right)=\left(0.62\pm 4.71\left(\textrm{stat}.\right)\pm 0.08\left(\textrm{syst}.\right)\right)\% $$ A CP η ′ → π + π − μ + μ − = 0.62 ± 4.71 stat . ± 0.08 syst . % , implying that no evidence ofCP-violation is observed at the present statistics. Finally, an axion-like particle is searched for via the decayη′ →π + π − a, a→e + e − , and upper limits of the branching fractions are presented for the mass assumptions of the axion-like particle in the range of 0−500 MeV/c 2 .
Physics↗
Technological developments and accelerator improvements for the FRIB beam power ramp-up
The Facility for Rare Isotope Beams (FRIB) began operation with 1 kW beam power for scientific users in May 2022 upon completion of 8 years of project construction. The ramp-up to the ultimate beam power of 400 kW, planned over a 6-year period, will enable the facility to reach its full potential for scientific discovery in isotope science and applications. In December 2023, a record-high beam power of 10.4 kW uranium was delivered to the target. Technological developments and accelerator improvements are being made over the entire facility and are key to completion of the power ramp-up. Major technological developments entail the phased deployment of high-power beam-intercepting systems, including the charge strippers, the charge selection systems, the production target, and the beam dump, along with support systems, including non-conventional utilities (NCU) and remote handling facilities. Major accelerator improvements include renovations to aging legacy systems associated with experimental beam lines and system automation for improved operational efficiency and better machine availability. Experience must be gained to safely handle the increased radiological impacts associated with high beam power; extensive machine studies and advanced beam tuning procedures are needed to minimize uncontrolled beam losses for the desired operating conditions. This paper discusses the technological developments and accelerator improvements with emphasis on major R&D efforts.
43 PARTICLE ACCELERATORS↗
Search for the semi-muonic charmonium decay J/ψ → D−μ+νμ + c.c.
Abstract Using (10087 ± 44) × 10 6 J/ψevents collected with the BESIII detector at the BEPCIIe + e − storage ring at the center-of-mass energy of$$ \sqrt{s} $$ s = 3.097 GeV, we present a search for the rare semi-muonic charmonium decayJ/ψ→D − μ + ν μ + c.c.. Since no significant signal is observed, we set an upper limit of the branching fraction to be$$ \mathcal{B} $$ B (J/ψ→D − μ + ν μ + c.c.) < 5.6 × 10 −7 at 90% confidence level. This is the first search for the weak decay of charmonium with a muon in the final state.
Physics↗
Measurement of the e+e− → $$ {K}_S^0{K}_L^0 $$π0 cross sections from $$ \sqrt{s} $$ = 2.000 to 3.080 GeV
Abstract Based one + e − collision data collected at center-of-mass energies from 2.000 to 3.080 GeV by the BESIII detector at the BEPCII collider, a partial wave analysis is performed for the processe + e − →$$ {K}_S^0{K}_L^0 $$ K S 0 K L 0 π 0 . The results allow the Born cross sections of the processe + e − →$$ {K}_S^0{K}_L^0 $$ K S 0 K L 0 π 0 , as well as its subprocessese + e − →K ∗ (892) 0 $$ \overline{K} $$ K ¯ 0 and$$ {K}_2^{\ast } $$ K 2 ∗ (1430) 0 $$ \overline{K} $$ K ¯ 0 to be measured. The Born cross sections fore + e − →$$ {K}_S^0{K}_L^0 $$ K S 0 K L 0 π 0 are consistent with previous measurements by BaBar, but with substantially improved precision. The Born cross section lineshape of the processe + e − K ∗ (892) 0 $$ \overline{K} $$ K ¯ 0 is consistent with a vector meson state around 2.2 GeV with a significance of 3.2σ. A Breit-Wigner fit determines its mass asM Y = (2164.7±9.1±3.1) MeV/c 2 and its width as Γ Y = (32.4±21.0±1.8) MeV.
Physics↗
Measurement of $$ {e}^{+}{e}^{-}\to p{K}^{-}\overline{\Lambda}+c.c. $$ cross sections between 4.009 GeV and 4.951 GeV
Abstract Usinge + e − collision datasets corresponding to a total integrated luminosity of 21.7 fb −1 collected with the BESIII detector at the BEPCII collider at center-of-mass energies ranging from 4.009 GeV to 4.951 GeV, the energy-dependent cross sections of$$ {e}^{+}{e}^{-}\to p{K}^{-}\overline{\Lambda}+c.c. $$ e + e − → p K − Λ ¯ + c . c . are measured for the first time. By fitting these energy-dependent cross sections, we search for the excitedψstatesψ(4160) andψ(4415), and the vector charmonium-like statesψ(4230),ψ(4360), andψ(4660). No evidence for these is observed and the upper limits on the branching fractions of these states decaying into$$ p{K}^{-}\overline{\Lambda}+c.c. $$ p K − Λ ¯ + c . c . are set at the 90% confidence level.
Physics↗
Studies of the decay $$ {\textrm{D}}_{\textrm{s}}^{+}\to {\textrm{K}}^{+}{\textrm{K}}^{-}{\mu}^{+}{\nu}_{\mu } $$
Abstract The$$ {D}_s^{+}\to {K}^{+}{K}^{-}{\mu}^{+}{\nu}_{\mu } $$ D s + → K + K − μ + ν μ decay is studied based on 7.33 fb −1 ofe + e − collision data collected with the BESIII detector at center-of-mass energies in the range from 4.128 to 4.226 GeV. The absolute branching fraction is measured as$$ \mathcal{B}\left({D}_s^{+}\to \phi {\mu}^{+}{\nu}_{\mu}\right)=\left(2.25\pm 0.09\pm 0.07\right)\times {10}^{-2} $$ B D s + → ϕ μ + ν μ = 2.25 ± 0.09 ± 0.07 × 10 − 2 , the most precise measurement to date. Combining with the world average of$$ \mathcal{B}\left({D}_s^{+}\to \phi {e}^{+}{\nu}_e\right) $$ B D s + → ϕ e + ν e , the ratio of the branching fractions obtained is$$ \frac{\mathcal{B}\left({D}_s^{+}\to \phi {\mu}^{+}{\nu}_{\mu}\right)}{\mathcal{B}\left({D}_s^{+}\to \phi {e}^{+}{\nu}_e\right)}=0.94\pm 0.08 $$ B D s + → ϕ μ + ν μ B D s + → ϕ e + ν e = 0.94 ± 0.08 , in agreement with lepton universality. By performing a partial wave analysis, the hadronic form factor ratios atq 2 = 0 are extracted, finding$$ {r}_V=\frac{V(0)}{A_1(0)}=1.58\pm 0.17\pm 0.02 $$ r V = V 0 A 1 0 = 1.58 ± 0.17 ± 0.02 and$$ {r}_2=\frac{A_2(0)}{A_1(0)}=0.71\pm 0.14\pm 0.02 $$ r 2 = A 2 0 A 1 0 = 0.71 ± 0.14 ± 0.02 , where the first uncertainties are statistical and the second are systematic. No significantS-wave contribution fromf 0 (980)→ K + K − is found. The upper limit$$ \mathcal{B}\left({D}_s^{+}\to {f}_0(980){\mu}^{+}{\nu}_{\mu}\right)\cdot \mathcal{B}\left({f}_0(980)\to {K}^{+}{K}^{-}\right)<5.45\times {10}^{-4} $$ B D s + → f 0 980 μ + ν μ ⋅ B f 0 980 → K + K − < 5.45 × 10 − 4 is set at 90% credibility level.
Physics↗
Updated measurement of the branching fraction of D s + → τ + ν τ via τ + → π + ν ¯ τ
Not Available
Ablikim, M.↗
Measurement of the branching fractions of the singly Cabibbo-suppressed decays $$ {\Lambda}_{\textrm{c}}^{+}\to \textrm{p}\eta $$ and $$ {\Lambda}_{\textrm{c}}^{+}\to \textrm{p}\omega $$
Abstract Based on 4.5 fb −1 e + e − collision data collected with BESIII detector at seven energy points between 4.600 and 4.699 GeV, the branching fractions for$$ {\Lambda}_c^{+}\to p\eta $$ Λ c + → pη and$$ {\Lambda}_c^{+}\to p\omega $$ Λ c + → pω were measured by means of single-tag method. The branching fractions of$$ {\Lambda}_c^{+}\to p\eta $$ Λ c + → pη and$$ {\Lambda}_c^{+}\to p\omega $$ Λ c + → pω are determined to be (1.57±0.11 stat ±0.04 syst )×10 −3 and (1.11±0.20 stat ±0.07 syst )×10 −3 , with a statistical significance of greater than 10σand 5.7σ, respectively. These results are consistent with the previous measurements by BESIII, LHCb and Belle, and the result of$$ {\Lambda}_c^{+}\to p\eta $$ Λ c + → pη is the most precise to date.
Physics↗
Measurement of the cross section of $$ {e}^{+}{e}^{-}\to {\Xi}^{-}{\overline{\Xi}}^{+} $$ at center-of-mass energies between 3.510 and 4.843 GeV
Abstract Usinge + e − collision data corresponding to a total integrated luminosity of 12.9 fb −1 collected with the BESIII detector at the BEPCII collider, the exclusive Born cross sections and the effective form factors of the reaction$$ {e}^{+}{e}^{-}\to {\Xi}^{-}{\overline{\Xi}}^{+} $$ e + e − → Ξ − Ξ ¯ + are measured via the single baryon-tag method at 23 center-of-mass energies between 3.510 and 4.843 GeV. Evidence for the decay$$ \psi (3770)\to {\Xi}^{-}{\overline{\Xi}}^{+} $$ ψ 3770 → Ξ − Ξ ¯ + is observed with a significance of 4.5σby analyzing the measured cross sections together with earlier BESIII results. For the other charmonium(-like) statesψ(4040),ψ(4160),Y(4230),Y(4360),ψ(4415), andY(4660), no significant signal of their decay to$$ {\Xi}^{-}{\overline{\Xi}}^{+} $$ Ξ − Ξ ¯ + is found. For these states, upper limits of the products of the branching fraction and the electronic partial width at the 90% confidence level are provided.
Physics↗
Measurement of Λ transverse polarization in e+e− collisions at $$ \sqrt{s} $$ = 3.68 − 3.71 GeV
Abstract With data samples collected with the BESIII detector at seven energy points at$$ \sqrt{s} $$ s = 3.68−3.71 GeV, corresponding to an integrated luminosity of 333 pb −1 , we present a study of the Λ transverse polarization in thee + e − →$$ \Lambda \overline{\Lambda} $$ Λ Λ ¯ reaction. The significance of polarization by combining the seven energy points is found to be 2.6σincluding the systematic uncertainty, which implies a non-zero phase between the transition amplitudes of the$$ \Lambda \overline{\Lambda} $$ Λ Λ ¯ helicity states. The modulus ratio and the relative phase of EM-psionicform factors combined with all energy points are measured to beR Ψ =$$ {0.71}_{-0.10}^{+0.10} $$ 0.71 − 0.10 + 0.10 ±0.03 and ∆Φ Ψ =$$ {23}_{-8.0}^{+8.8} $$ 23 − 8.0 + 8.8 ±1.6°, where the first uncertainties are statistical and the second systematic.
Physics↗