We present the first results of the search for sub-MeV fermionic dark matter absorbed by electron targets of germanium using the 205.4 kg . day data collected by the CDEX-10 experiment, with the analysis threshold of 160 eVee. No significant dark matter (DM) signals over the background are observed. Results are presented as limits on the cross section of DM-electron interaction. We present new constraints of cross section in the DM range of 0.1-10 keV/c(2) for vector and axial-vector interaction. The upper limit on the cross section is set to be 6.8 x 10(-46) cm(2) for vector interaction, and 2.3 x 10(-46) cm(2) for axial-vector interaction at DM mass of 5 keV/c(2).

Based on 6.1  fb^{-1} of e^{+}e^{-} annihilation data collected at center-of-mass energies from 4.600 to 4.843 GeV with the BESIII detector at the BEPCII collider, a partial wave analysis of Λ_{c}^{+}→Λπ^{+}η is performed, and branching fractions and decay asymmetry parameters of intermediate processes are determined. The process Λ_{c}^{+}→Λa_{0}(980)^{+} is observed for the first time, and evidence for the pentaquark candidate Σ(1380)^{+} decaying into Λπ^{+} is found with statistical significance larger than 3σ with mass and width fixed to theoretical predictions. The branching fraction product B[Λ_{c}^{+}→Λa_{0}(980)^{+}]B[a_{0}(980)^{+}→π^{+}η] is determined to be (1.05±0.16_{stat}±0.05_{syst}±0.07_{ext})%, which is larger than theoretical calculations by 1-2 orders of magnitude. Here the third (external) systematic is from B(Λ_{c}^{+}→Λπ^{+}η). Finally, we precisely obtain the absolute branching fraction B(Λ_{c}^{+}→Λπ^{+}η)=(1.94±0.07_{stat}±0.11_{syst})%.

Based on a sample of (2712.4 ± 14.3) × 106 ψ(3686) events collected with the BESIII detector, a partial wave analysis of the decay ψ (3686)→ΛΣ^0π^0 + c.c. is performed to investigate Λ* and Σ* resonances in the π^0Σ^0 and π0Λ invariant mass distributions. Significant contributions are found from the Λ(1405), Λ(1520), Λ(1600), Λ(1670), Λ(1690), Λ(1800), Λ(1890), Λ(2325), Σ(1385), Σ(1660), Σ(1670), Σ(1750), and Σ(1910). The masses, widths, and production branching fractions for each component are determined. In addition, the branching fraction of ψ (3686)→ΛΣ^0π^0 + c.c. is measured to be (1.544 ± 0.013 ± 0.071) × 10−4 for the first time, where the first uncertainty is statistical and the second systematic.

A bstract Based on 7.33 fb − 1 of e + e − collision data collected by the BESIII detector operating at the BEPCII collider at center-of-mass energies from 4.128 to 4.226 GeV, a search for the Majorana neutrino ν m is conducted in the lepton-number-violating decays of $$ {D}_{\textrm{s}}^{+} $$ D s + → h − h 0 e + e + . Here, h − represents a K − or π − , and h 0 represents a π 0 , $$ {K}_S^0 $$ K S 0 or ϕ . No significant signal is observed, and the upper limits of their branching fractions at the 90% confidence level are determined to be $$ \mathcal{B} $$ B ( $$ {D}_{\textrm{s}}^{+} $$ D s + → ϕπ − e + e + ) < 6 . 9 × 10 − 5 , $$ \mathcal{B} $$ B ( $$ {D}_{\textrm{s}}^{+} $$ D s + → ϕK − e + e + ) < 9 . 9 × 10 − 5 , $$ \mathcal{B} $$ B ( $$ {D}_{\textrm{s}}^{+} $$ D s + → $$ {K}_S^0 $$ K S 0 π − e + e + ) < 1 . 3 × 10 − 5 , $$ \mathcal{B} $$ B ( $$ {D}_{\textrm{s}}^{+} $$ D s + → $$ {K}_S^0 $$ K S 0 K − e + e + ) < 2 . 9 × 10 − 5 , $$ \mathcal{B} $$ B ( $$ {D}_{\textrm{s}}^{+} $$ D s + → π − π 0 e + e + ) < 2 . 9 × 10 − 5 and $$ \mathcal{B} $$ B ( $$ {D}_{\textrm{s}}^{+} $$ D s + → K − π 0 e + e + ) < 3 . 4 × 10 − 5 . The Majorana neutrino is searched for with different mass assumptions within the range [0 . 20 , 0 . 80] GeV /c 2 in the decay of $$ {D}_{\textrm{s}}^{+} $$ D s + → ϕe + ν m with ν m → π − e + , and the upper limits of the branching fractions at the 90% confidence level are at the level of 10 − 5 –10 − 2 , depending on the mass of the Majorana neutrino.

Long gamma-ray bursts (GRBs) are believed to originate from core collapse of massive stars. High-redshift GRBs can probe the star formation and reionization history of the early Universe, but their detection remains rare. Here we report the detection of a GRB triggered in the 0.5–4 keV band by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated as EP240315a, whose bright peak was also detected by the Swift Burst Alert Telescope and Konus-Wind through off-line analyses. At a redshift of z = 4.859, EP240315a showed a much longer and more complicated light curve in the soft-X-ray band than in gamma rays. Benefiting from a large field of view ( 3,600°2) and a high sensitivity, EP-WXT captured the earlier engine activation and extended late engine activity through a continuous detection. With a peak X-ray flux at the faint end of previously known high-z GRBs, the detection of EP240315a demonstrates the great potential for EP to study the early universe via GRBs. The death of massive stars has traditionally been discovered by explosive events in the gamma-ray band. Liu et al. show that the sensitive wide-field monitor on board Einstein Probe can reveal a weak soft-X-ray signal much earlier than gamma rays.

A bstract By analyzing e + e − collision data with an integrated luminosity of 7.9 fb − 1 collected with the BESIII detector at the center-of-mass energy of 3.773 GeV, the branching fraction of D + → τ + ν τ is determined as $$ \mathcal{B} $$ B = (9.9 ± 1.1 stat ± 0.5 syst ) × 10 − 4 . Using the most precise result $$ \mathcal{B} $$ B ( D + → μ + ν μ ) = (3.981 ± 0.079 stat ± 0.040 syst ) × 10 − 4 [1], we determine R τ/μ = Γ( D + → τ + ν τ )/Γ( D + → μ + ν μ ) = 2.49 ± 0.31, achieving a factor of two improvement in precision compared to the previous BESIII result. This measurement is in agreement with the standard model prediction of lepton flavor universality within one standard deviation.

Massive stars end their lives as core-collapse supernovae, among which some extremes are broad-lined type Ic supernovae from Wolf-Rayet stars associated with long-duration gamma-ray bursts (LGRBs) with powerful relativistic jets. Their less-extreme brethren make unsuccessful jets that are choked inside the stars, appearing as X-ray flashes or low-luminosity GRBs. However, there exists a population of extragalactic fast X-ray transients with timescales ranging from seconds to thousands of seconds, whose origins remain obscure. Here we report the discovery of the bright X-ray transient EP240414a detected by the Einstein Probe, which is associated with the type Ic supernova SN 2024gsa at a redshift of 0.401. The X-ray emission evolution is characterized by a very soft energy spectrum peaking at <1.3 keV, which makes it different from known LGRBs, X-ray flashes or low-luminosity GRBs. Follow-up observations at optical and radio bands revealed the existence of a weak relativistic jet that interacts with an extended shell surrounding the progenitor star. Located on the outskirts of a massive galaxy, this event reveals a population of explosions of Wolf-Rayet stars characterized by a less powerful engine that drives a successful but weak jet, possibly owing to a progenitor star with a smaller core angular momentum than in traditional LGRB progenitors.

Using 20.3  fb^{-1} of e^{+}e^{-} collision data collected at a center-of-mass energy of E_{c.m.}=3.773  GeV with the BESIII detector operating at the BEPCII collider, we determine the branching fraction of the leptonic decay D^{+}→μ^{+}ν_{μ} to be (4.034±0.080_{stat}±0.040_{syst})×10^{-4}. Interpreting our measurement with knowledge of the Fermi coupling constant G_{F}, the masses of the D^{+} and μ^{+} as well as the lifetime of the D^{+}, we determine f_{D^{+}}|V_{cd}|=(48.02±0.48_{stat}±0.24_{syst}±0.12_{input}±0.15_{EM})  MeV after taking into account necessary radiative corrections. This result is a factor of 2.3 more precise than the previous best measurement. Using the value of the magnitude of the c→d Cabibbo-Kobayashi-Maskawa matrix element |V_{cd}| given by the global standard model fit, we obtain the D^{+} decay constant f_{D^{+}}=(213.5±2.1_{stat}±1.1_{syst}±0.8_{input}±0.7_{EM})  MeV. Alternatively, using the value of f_{D^{+}} from a precise lattice quantum chromodynamics calculation, we extract |V_{cd}|=0.2265±0.0023_{stat}±0.0011_{syst}±0.0009_{input}±0.0007_{EM}.

Utilizing a dataset of 6.7 fb(-1) from electron-positron collisions recorded by the BESIII detector at the BEPCII storage ring, a search is conducted for the processes e(+)e(-) -> phi chi(c0) and phi eta(c2)(1D) across centerof-mass energies from 4.47 to 4.95 GeV. In the absence of any significant signals, upper limits are set. These include limits on the dressed cross sections for e(+)e(-) -> phi chi(c0), as well as the product of the dressed cross section for e(+)e(-) -> phi eta(c2)(1D) and a sum of five branching fractions. Furthermore, the product of the electronic width of Y(4660) and the branching fraction of the Y(4660) ->phi chi(c0), denoted as Gamma Y-e+e-((4660)) B-Y(4660)->phi chi(c0), is determined to be <0.35 eV at the 90% confidence level.

One of the main goals of studying semileptonic decays in flavor physics is to gain a better understanding of hadronic transitions in the nonperturbative region of Quantum Chromodynamics. This involves measuring Cabibbo-Kobayashi-Maskawa matrix elements, understanding form factors, and comparing them with theoretical predictions. We report a first study of the semileptonic decay D^{0}→K^{-}π^{0}μ^{+}ν_{μ} by analyzing an e^{+}e^{-} annihilation data sample of 7.93  fb^{-1} collected at the center-of-mass energy of 3.773 GeV with the BESIII detector. The absolute branching fraction of D^{0}→K^{-}π^{0}μ^{+}ν_{μ} is measured for the first time, providing necessary input for extracting the c→s Cabibbo-Kobayashi-Maskawa matrix element through this process. This measurement allows us to test lepton flavor universality, with no indication of violation found. Furthermore, a series of hadronic form factors have been determined and compared with theoretical predictions, which will impose stricter constraints on theoretical models.

The neutron-rich rare isotope 190W is discussed as a candidate for a prolate-oblate transitional nucleus with maximum γ-softness. The collectivity of this isotope is assessed for the first time by the measurement of the reduced E2 transition probability of its first 2+ state to the ground state. The experiment employed the FAst TIming Array (FATIMA), comprised of 36 LaBr3(Ce) scintillators, which was part of the DESPEC setup at GSI, Darmstadt. The 41+ and 21+ states of 190W were populated subsequently to the decay of its 127(12) μs isomeric Jπ=10− state. The mean lifetime of the 21+ state was determined to be τ=274(28) ps, which corresponds to a B(E2;21+→01+) value of 95(10) W.u. The results motivated a revision of previous calculations within an energy-density functional-based interacting boson model-2 approach, yielding E2 transition properties and spectroscopic quadrupole moments for tungsten isotopes. From comparison to theory, the new data suggest that 190W is at the transition from prolate to oblate structure along the W isotopic chain, which had previously been discussed as a nuclear shape-phase transition.

The Belle II experiment at the SuperKEKB $e^{+}e^{-}$ collider took data from 2019 to 2022 (Run 1) and is currently undergoing its planned first long shutdown (LS1). During its operational period, SuperKEKB achieved a record-breaking instantaneous luminosity of 4.7 x 10$^{34}$ cm$^{-2}$s$^{-1}$ [1] and Belle II recorded a dataset corresponding to 428 fb$^{-1}$. The Belle II Pixel Vertex Detector (PXD), which is the innermost sub-detector, is based on the DEpleted P-channel Field Effect Transistor (DEPFET) technology [2]. Along with the Silicon Vertex Detector (SVD) [3], utilizing double-sided silicon strips, this forms the Belle II Vertex Detector system (VXD), enabling precise reconstruction of primary and decay vertices. The PXD module features a 75 $\mu$m-thin DEPFET sensor area with varying pixel sizes from 50 x 55 $\mu$m to 50 x 85 $\mu$m while maintaining a hit efficiency of about 99 %. Its average material budget inside the physics acceptance corresponds to 0.2 % X$_{0}$ per layer. PXD consist of 20 ladders arranged in two cylindrical layers around the beam axis. The Run 1 PXD was installed in a reduced configuration comprising the full inner layer (L1, eight ladders) and only two out of twelve outer layer (L2) ladders. In this article, we will illuminate the performance and operational challenges observed during its 4-year operation in a harsh environment characterized by a high beam background level. A fully populated detector can compensate acceptance losses by redundancy and reduce the probability of wrong hit assignment introduced by higher background levels resulting from increased instantaneous luminosity. During LS1 PXD was replaced by a new, fully populated PXD2. Its commissioning and testing phase during LS1 will be described. A hit efficiency of $>$98 % was measured in most regions using cosmic particles. The current installation schedule foresees beam operation to resume in winter 23/24.

Using e+e− collision data collected with the BESIII detector at the BEPCII collider at center-of-mass energies between 3.510 and 4.914 GeV, corresponding to an integrated luminosity of 25 fb−1, we measure the Born cross sections for the process e^+e^-→K^-Ξ^+Λ /Σ^0 at thirty-five energy points with a partial-reconstruction strategy. By fitting the dressed cross sections of e^+e^-→K^-Ξ^+Λ /Σ^0 , evidence for ψ (4160)→K^-Ξ^+Λ is found for the first time with a significance of 4.4σ, including systematic uncertainties. No evidence for other possible resonances is found. In addition, the products of electronic partial width and branching fraction for all assumed resonances decaying into K^-Ξ^+Λ /Σ^0 are determined.

Based on (2.712 +/- 0.014) x 10(9) psi(3686) events collected by the BESIII Collaboration, evidence of the hadronic decay h(c) -> (KSK+)-K-0 pi(-) + c.c. is found with a significance of 4.3 sigma in the psi(3686) -> pi(0)h(c) process. The branching fraction of h(c) -> (KSK+)-K-0 pi(-) + c.c. is measured to be (7.3 +/- 1.8 +/- 0.8) x 10(-4), where the first and second uncertainties are statistical and systematic, respectively. Combining with the exclusive decay width of eta(c) -> K (K) over bar pi, our result indicates inconsistencies with both pQCD and NRQCD predictions.

Based on (10.09 +/- 0.04) x 10(9) J/psi events collected with the BESIII detector operating at the BEPCII collider, a partial wave analysis of the decay J/psi -> phi pi(0 eta). is performed. We observe for the first time two new structures on the phi eta invariant mass distribution, with significances exceeding 27 sigma and 13 sigma; the first with J(PC) = 1(+-), mass M = (1908 +/- 6(stat)(-4)(+8) (sys)) MeV/c(2), and width Gamma = (175 +/- 13(stat)(-16)(+7) (sys)) MeV, the second with J(PC) = 1(--), mass M = (1992 +/- 12 (stat)(-6)(+15) (sys)) MeV/c(2), and width Gamma = (132 +/- 22(stat)(-4)(+17) (sys)) MeV. These measurements provide important input for the strangeonium spectrum. In addition, the f(0) (980) - a(0)(980)(0) mixing signal in J/psi -> phi f(0)(980) -> phi a(0)(980)(0) and the corresponding electromagnetic decay J/psi -> phi a(0)(980)(0) are measured with improved precision, providing crucial information to understand the nature of a(0)(980)(0) and f(0)(980).

The CP-even fractions (F_+) of the decays D^0→π^+π^-π^0 and D^0→ K^+K^-π^0 are measured with a quantum-correlated ψ(3770)→ DD̅ data sample collected by the BESIII experiment corresponding to an integrated luminosity of 7.93 fb^-1. The results are F_+^π^+π^-π^0=0.9406±0.0036±0.0021 and F_+^K^+K^-π^0=0.631±0.014±0.011, where the first uncertainties are statistical and the second systematic. These measurements are consistent with the previous determinations, and the uncertainties for F_+^π^+π^-π^0 and F_+^K^+K^-π^0 are reduced by factors of 3.9 and 2.6, respectively. The reported results provide important inputs for the precise measurement of the angle γ of the Cabibbo-Kobayashi-Maskawa matrix and indirect CP violation in charm mixing.

Based on (2712.4±14.3)×106 e+e−→ψ(3686) events collected with the BESIII detector operating at the BEPCII Collider, we report the first evidence of χc0→ΛΛ¯ϕ decays and the first observation of χc1,2→ΛΛ¯ϕ decays, with significances of 4.1σ, 11.3σ and 13.0σ, respectively. The decay branching fractions of χc0,1,2→ΛΛ¯ϕ are measured to be (2.99±1.24±0.19)×10−5, (6.01±0.90±0.40)×10−5, and (7.13±0.81±0.36)×10−5, where the first uncertainties are statistical and the second systematic. No obvious enhancement near the ΛΛ¯ production threshold or excited Λ state is found in the Λϕ (or Λ¯ϕ) system. Published by the American Physical Society 2024

We present cross sections for the reaction e(+)e(-) -> (KSKL0)-K-0 at center-of-mass energies ranging from 3.51 to 4.95 GeV using data samples collected in the BESIII experiment, corresponding to a total integrated luminosity of 26.5 fb(-1). The ratio of neutral-to-charged kaon form factors at large momentum transfers (12 < Q(2) < 25 GeV2) is determined to be 0.21 +/- 0.01, which indicates a small but significant effect of flavor-SU(3) breaking in the kaon wave function, and, consequently, excludes the possibility that flavor-SU(3) breaking is the primary reason for the strong experimental violation of the pQCD prediction vertical bar F(pi(+/-))vertical bar/vertical bar F(K-+/-)vertical bar = f(pi)(2)/f(K)(2), where F(pi(+/-)) and F(K-+/-) are the form factors, and f(pi) and f(K) are the decay constants of charged pions and kaons, respectively. We also observe a significant signal for the charmless decay psi(3770)->(KSKL0)-K-0 for the first time. Within a 1 sigma contour of the likelihood value, the branching fraction for psi(3770)-> K K-0(S)L(0) is determined to be B=(2.63(-1.59)(+1.40)) x 10(-5), and the relative phase between the continuum and psi(3770) amplitudes is phi = (-0.39(-0.10)(+0.05))pi. The branching fraction is in good agreement with the S- and D-wave charmonia mixing scheme proposed in the interpretation of the "rho pi puzzle" between J/psi and psi(3686) decays.

Using e(+)e(-) annihilation data sets corresponding to an integrated luminosity of 4.5 fb(-1), collected with the BESIII detector at center-of-mass energies between 4.600 and 4.699 GeV, we report the first measurements of the absolute branching fractions B(Lambda(+)(c)-> pK(L)(0) = (1.67 +/- 0.06 +/- 0.04)%, B(Lambda(+)(c)-> pK(L)(0) pi(+)pi(-) = (1.69 +/- 0.10 +/- 0.05)%, and B(Lambda(+)(c)-> pK(L)(0)pi(0) = (2.02 +/- 0.13 +/- 0.05)%, where the first uncertainties are statistical and the second systematic. Combining with the known branching fractions of Lambda(+)(c)-> pK(S)(0), Lambda(+)(c)-> pK(S)(0) pi(+)pi(-), and Lambda(+)(c)-> pK(S)(0)pi(0), we present the first measurements of the K-S(0)-K-L(0) asymmetries R(Lambda K-+(c)S,L(0) X) = B(Lambda(+)(c) -> (KSX)-X-0-B (Lambda(+)(c)-> K-L(0) X/B(Lambda(+)(c)->(KSX)-X-0)+B(Lambda(+)(c)->(KLX)-X-0) in charmed baryon decays: R(Lambda(+)(c)pK(S,L)(0)) = -0.025 +/- 0.031, R(Lambda(+)(c)pK(S,L)(0) pi(+)pi(-)) = -0.027 +/- 0.048 and R(Lambda(+)(c)pK(S,L)(0)pi(0) = -0.015 +/- 0.046. No significant asymmetries with statistical significance are observed.

Abstract Using e + e − collision data collected by the BESIII detector at BEPCII corresponding to an integrated luminosity of 30 fb −1, we measure Born cross sections and effective form factors for the process e + e − → Ξ 0 Ξ ¯ 0 $$ {e}^{+}{e}^{-}\to {\Xi}^0{\overline{\Xi}}^0 $$ at forty-five center-of-mass energies between 3.51 and 4.95 GeV. The dressed cross section is fitted, assuming a power-law function plus a charmonium(-like) state, i.e., ψ(3770), ψ(4040), ψ(4160), ψ(4230), ψ(4360), ψ(4415) or ψ(4660). No significant charmonium(-like) state decaying into Ξ 0 Ξ ¯ 0 $$ {\Xi}^0{\overline{\Xi}}^0 $$ is observed. Upper limits at the 90% confidence level on the product of the branching fraction and the electronic partial width are provided for each decay. In addition, ratios of the Born cross sections and the effective form factors for e + e − → Ξ 0 Ξ ¯ 0 $$ {e}^{+}{e}^{-}\to {\Xi}^0{\overline{\Xi}}^0 $$ and e + e − → Ξ − Ξ ¯ + $$ {e}^{+}{e}^{-}\to {\Xi}^{-}{\overline{\Xi}}^{+} $$ are also presented to test isospin symmetry and the vector meson dominance model.