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A determination of the CP-even fraction F+ in the decay D0→K+K−π+π− is presented. Using 2.93 fb−1 of e+e−→ψ(3770)→DD¯ data collected by the BESIII detector, one charm meson is reconstructed in the signal mode and the other in a CP eigenstate or the decay D→K0S,Lπ+π−. Analysis of the relative rates of these double-tagged events yields the result F+=0.730±0.037±0.021, where the first uncertainty is statistical and the second is systematic. This is the first model-independent measurement of F+ in D0→K+K−π+π− decays.
A determination of the CP-even fraction F+ in the decay D0→K+K−π+π− is presented. Using 2.93 fb−1 of e+e−→ψ(3770)→DD¯ data collected by the BESIII detector, one charm meson is reconstructed in the signal mode and the other in a CP eigenstate or the decay D→K0S,Lπ+π−. Analysis of the relative rates of these double-tagged events yields the result F+=0.730±0.037±0.021, where the first uncertainty is statistical and the second is systematic. This is the first model-independent measurement of F+ in D0→K+K−π+π− decays.
Behaviorally irrelevant feature matching increases neural and behavioral working memory readout
(2024)
There is an ongoing debate about whether working memory (WM) maintenance relies on persistent activity and/or short-term synaptic plasticity. This is a challenging question, because neuroimaging techniques in cognitive neuroscience measure activity only. Recently, neural perturbation techniques have been developed to tackle this issue, such as visual impulse perturbation or “pinging”, which reveals (un)attended WM content during maintenance. There are contrasting explanations of how pinging reveals WM content, which is central to the debate. Pinging could reveal mnemonic representations by perturbing content-specific networks or by increasing the neural signal-to-noise ratio of active neural states. Here we tested the extent to which the neural impulse response is patterned by the WM network, by presenting two different impulse stimuli. If the impulse interacts with WM networks, the WM-specific impulse response should be enhanced by physical overlap between the initial memory item and the subsequent external perturbation stimulus. This prediction was tested in a delayed orientation match-to-sample task by matching or mismatching task-irrelevant spatial frequencies between memory items and impulse stimuli, as well as probes. Matching probe spatial frequency with memory items resulted in faster behavioral response times and matching impulse spatial frequency with memory items increased the specificity of the neural impulse response as measured from EEG. Matching spatial frequencies did neither result in globally stronger neural responses nor in a larger decrease in trial-to-trial variability compared to mismatching spatial frequencies. The improved neural and behavioural readout of irrelevant feature matching provide evidence that impulse perturbation interacts directly with the memory representations.
The activity-silent framework of working memory (WM) posits that the neural activity during object perception and encoding leaves behind patterned, “activity-silent” neural traces that enable WM maintenance without the need for continuous, memory-specific neural activity. The presence of such traces in the memory network subsequently patterns its responses to external stimulation, which can be used to readout the contents of WM using an impulse perturbation or “pinging” approach. The extent to which the neural impulse response is patterned by the WM network should be modulated by the physical overlap between the initial memory item and the subsequent external perturbation stimulus, with higher overlap increasing WM readout. Here we tested this prediction in a delayed orientation match-to-sample task, by either matching or mismatching task-irrelevant spatial frequencies between memory items and impulse stimuli, and between memory items and probes. Matching frequencies resulted in faster behavioral response times, and increased the WM-specificity of the neural impulse response as measured from the EEG signal. We found no evidence that matching spatial frequencies resulted in globally stronger or different neural responses, but rather in distinct neural activation patterns. The beneficial effects of feature matching in our task support the tenets of the activity-silent framework of WM, and confirm that impulse perturbation interacts directly with the representations that are held in memory.
The activity-silent framework of working memory (WM) posits that the neural activity during object perception and encoding leaves behind patterned, “activity-silent” neural traces that enable WM maintenance without the need for continuous, memory-specific neural activity. The presence of such traces in the memory network subsequently patterns its responses to external stimulation, which can be used to readout the contents of WM using an impulse perturbation or “pinging” approach. The extent to which the neural impulse response is patterned by the WM network should be modulated by the physical overlap between the initial memory item and the subsequent external perturbation stimulus, with higher overlap increasing WM readout. Here we tested this prediction in a delayed orientation match-to-sample task, by either matching or mismatching task-irrelevant spatial frequencies between memory items and impulse stimuli, and between memory items and probes. Matching frequencies resulted in faster behavioral response times, and increased the WM-specificity of the neural impulse response as measured from the EEG signal. We found no evidence that matching spatial frequencies resulted in globally stronger or different neural responses, but rather in distinct neural activation patterns. The beneficial effects of feature matching in our task support the tenets of the activity-silent framework of WM, and confirm that impulse perturbation interacts directly with the representations that are held in memory.
The singly Cabibbo-suppressed decay Λ+c→nπ+ is observed for the first time with a statistical significance of 7.3σ by using 3.9 fb−1 of e+e− collision data collected at center-of-mass energies between 4.612 and 4.699 GeV with the BESIII detector at BEPCII. The branching fraction of Λ+c→nπ+ is measured to be (6.6±1.2stat±0.4syst)×10−4. By taking the upper limit of branching fractions of Λ+c→pπ0 from the Belle experiment, the ratio of branching fractions between Λ+c→nπ+ and Λ+c→pπ0 is calculated to be larger than 7.2 at the 90% confidence level, which disagrees with the current predictions of available phenomenological models. In addition, the branching fractions of the Cabibbo-favored decays Λ+c→Λπ+ and Λ+c→Σ0π+ are measured to be (1.31±0.08stat±0.05syst)×10−2 and (1.22±0.08stat±0.07syst)×10−2, respectively, which are consistent with previous results.
The singly Cabibbo-suppressed decay Λ+c→nπ+ is observed for the first time with a statistical significance of 7.3σ by using 3.9 fb−1 of e+e− collision data collected at center-of-mass energies between 4.612 and 4.699 GeV with the BESIII detector at BEPCII. The branching fraction of Λ+c→nπ+ is measured to be (6.6±1.2stat±0.4syst)×10−4. By taking the upper limit of branching fractions of Λ+c→pπ0 from the Belle experiment, the ratio of branching fractions between Λ+c→nπ+ and Λ+c→pπ0 is calculated to be larger than 7.2 at the 90% confidence level, which disagrees with the current predictions of available phenomenological models. In addition, the branching fractions of the Cabibbo-favored decays Λ+c→Λπ+ and Λ+c→Σ0π+ are measured to be (1.31±0.08stat±0.05syst)×10−2 and (1.22±0.08stat±0.07syst)×10−2, respectively, which are consistent with previous results.
The cross sections of the e+e−→ϕη′ process at center-of-mass energies from 3.508 to 4.951 GeV are measured with high precision using 26.1 fb−1 data collected with the BESIII detector operating at the BEPCII storage ring. The cross sections are of the order of a few picobarn, and decrease as the center-of-mass energy increases as s−n/2 with n=4.35±0.14. This result is in agreement with the Nambu-Jona-Lasinio model prediction of n=3.5±0.9. In addition, the charmless decay ψ(3770)→ϕη′ is searched for by fitting the measured cross sections, yet no significant signal is observed. The upper limit of B(ψ(3770)→ϕη′) at the 90\% confidence level is determined to be 2.3×10−5.
The cross sections of the e+e−→ϕη′ process at center-of-mass energies from 3.508 to 4.951 GeV are measured with high precision using 26.1 fb−1 data collected with the BESIII detector operating at the BEPCII storage ring. The cross sections are of the order of a few picobarn, and decrease as the center-of-mass energy increases as s−n/2 with n=4.35±0.14. This result is in agreement with the Nambu-Jona-Lasinio model prediction of n=3.5±0.9. In addition, the charmless decay ψ(3770)→ϕη′ is searched for by fitting the measured cross sections, yet no significant signal is observed. The upper limit of B(ψ(3770)→ϕη′) at the 90\% confidence level is determined to be 2.3×10−5.
Using a data sample 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 at the BEPCII collider, we search for a scalar partner of the X(3872), denoted as X(3700), via ψ(3770)→γηη′ and γπ+π−J/ψ processes. No significant signals are observed and the upper limits of the product branching fractions B(ψ(3770)→γX(3700))⋅B(X(3700)→ηη′) and B(ψ(3770)→γX(3700))⋅B(X(3700)→π+π−J/ψ) are determined at the 90\% confidence level, for the narrow X(3700) with a mass ranging from 3710 to 3740 MeV/c2, which are from 0.8 to 1.8 (×10−5) and 0.9 to 3.4 (×10−5), respectively.