Using e+e− annihilation data corresponding to an integrated luminosity of 3.19 fb−1 collected at a center-of-mass energy of 4.178 GeV with the BESIII detector, we measure the absolute branching ...fractions BDs+→ηe+νe = (2.323±0.063stat ± 0.063syst)% and BDs+→η′e+νe = (0.824±0.073stat ± 0.027syst)% via a tagged analysis technique, where one Ds is fully reconstructed in a hadronic mode. Combining these measurements with previous BESIII measurements of BD+→η(′)e+νe, the η−η′ mixing angle in the quark flavor basis is determined to be ϕP = (40.1±2.1stat ± 0.7syst)°. From the first measurements of the dynamics of Ds+ → η(′)e+νe decays, the products of the hadronic form factors f+η(′)(0) and the Cabibbo-Kobayashi-Maskawa matrix element |Vcs| are determined with different form factor parametrizations. For the two-parameter series expansion, the results are f+η(0)|Vcs| = 0.4455±0.0053stat±0.0044syst and f+η′(0)|Vcs|=0.477±0.049stat±0.011syst.
We report the first observation of D+→τ+ντ with a significance of 5.1σ. We measure B(D+→τ+ντ)=(1.20±0.24stat±0.12syst)×10−3. Taking the world average B(D+→μ+νμ)=(3.74±0.17)×10−4, we obtain ...Rτ/μ=Γ(D+→τ+ντ)/Γ(D+→μ+νμ)=3.21±0.64stat±0.43syst., which is consistent with the standard model expectation of lepton flavor universality. Using external inputs, our results give values for the D+ decay constant fD+ and the Cabibbo-Kobayashi-Maskawa matrix element |Vcd| that are consistent with, but less precise than, other determinations.
By analyzing 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, we measure for the first time the ...absolute branching fraction of the D+ → ημ+νμ decay to be BD+→ημ+νμ = ( 10.4 ± 1.0stat ± 0.5syst) × 10−4. Using the world averaged value of BD+ → ηe+νe, the ratio of the two branching fractions is determined to be BD+ → ημ+νμ/BD+ → ηe+νe = 0.91 ± 0.13(stat+syst), which agrees with the theoretical expectation of lepton flavor universality within uncertainty. By studying the differential decay rates in five four-momentum transfer intervals, we obtain the product of the hadronic form factor f+η(0) and the c → d Cabibbo-Kobayashi-Maskawa matrix element |Vcd| to be fη+(0) |Vcd| = 0.087 ± 0.008stat ± 0.002syst. Taking the input of |Vcd| from the global fit in the standard model, we determine fη+(0) = 0.39 ± 0.04stat ± 0.01syst. On the other hand, using the value of fη+(0) calculated in theory, we find |Vcd| = 0.242 ± 0.022stat ± 0.00 6 syst ± 0.033theory.
Using an e+e− collision data sample of 2.93 fb−1 collected at a center-of-mass energy of 3.773 GeV by the BESIII detector at BEPCII, we report the observation of D0→a0(980)−e+νe and evidence for ...D+→a0(980)0e+νe with significances of 6.4σ and 2.9σ, respectively. The absolute branching fractions are determined to be B(D0→a0(980)−e+νe)×B(a0(980)−→ηπ−)=1.33−0.29+0.33(stat)±0.09(syst)×10−4 and B(D+→a0(980)0e+νe)×B(a0(980)0→ηπ0)=1.66−0.66+0.81(stat)±0.11(syst)×10−4. This is the first time the a0(980) meson has been measured in a D0 semileptonic decay, which would open one more interesting page in the investigation of the nature of the puzzling a0(980) states.
Abstract
From December 2019 to June 2021, the BESIII experiment collected approximately 5.85 fb
−1
of data at center-of-mass energies between 4.61 and 4.95 GeV. This is the highest collision energy ...BEPCII has reached to date. The accumulated
annihilation data samples are useful for studying charmonium(-like) states and charmed-hadron decays. By adopting a novel method of analyzing the production of
pairs in
annihilation, the center-of-mass energies are measured with a precision of
0.6 MeV. Integrated luminosities are measured with a precision of better than 1% by analyzing the events of large-angle Bhabha scattering. These measurements provide important inputs to analyses based on these data samples.
The IDEA detector concept has been designed to operate at a future large circular e+e− collider, like FCC-ee or CEPC. The IDEA detector has an innovative design with a central tracker enclosed in a ...superconducting solenoidal magnet. Going outwards, a preshower system followed by a dual readout calorimeter is foreseen. In the iron yoke, that closes the magnetic field, are then located three stations of muon detectors. The preshower and muon detectors are based on the μ-RWELL technology that inherits the best characteristics of the GEM, in particular the layout of the amplification stage, and Micromega detectors, that inspired the presence of a resistive stage. To profit of the industrial production capabilities of this technology, a modular design has been adopted for both systems: the μ-RWELL tile will have an active area of 50 × 50 cm2, but with a pitch between the readout strips of 400μm for the preshower and about 1 mm for the muon system. Other requirements are: a spatial resolution of the order of 100μm for the preshower and a reasonable total number of front-end channels for the muon system. To optimize the resistivity and the strip pitch, we have built a set of prototypes with active area of 5 × 40 cm2 and 40 cm long strips. The DLC resistivity is ranging from 10 to 80 MΩ/□. All these detectors have been exposed in October 2021 to a muon beam at the CERN SPS. The very positive results obtained pave the way for a completely new and competitive MPGD tracking device for high energy physics experiments.
We present the first amplitude analysis of the decay Ds+→π+π0η. We use an e+e− collision data sample corresponding to an integrated luminosity of 3.19 fb−1 collected with the BESIII detector at a ...center-of-mass energy of 4.178 GeV. We observe for the first time the W-annihilation dominant decays Ds+→a0(980)+π0 and Ds+→a0(980)0π+. We measure the absolute branching fraction B(Ds+→a0(980)+(0)π0(+),a0(980)+(0)→π+(0)η)=(1.46±0.15stat±0.23sys)%, which is larger than the branching fractions of other measured pure W-annihilation decays by at least one order of magnitude. In addition, we measure the branching fraction of Ds+→π+π0η with significantly improved precision.
We report the first observation of a$0\atop{0}$(980)-f0(980) mixing in the decays of J/$\psi$ → Φf0(980) → Φa$0\atop{0}$(980) → Φηπ0 and χc1 → a$0\atop{0}$(980)π0 → f0(980)π0 → π+ π- π0, using data ...samples of 1.31 × 109 J/$\psi$ events and 4.48 × 108 $\psi$(3686) events accumulated with the BESIII detector. The signals of f0(980) → a$0\atop{0}$(980) and a$0\atop{0}$(980) → f0(980) mixing are observed with a statistical significance of 7.4σ and 5.5σ, respectively. The corresponding branching fractions and mixing intensities are measured, and the constraint regions on the coupling constants, ga0K+K- and gf0K+K-, are estimated. The results improve the understanding of the nature of a$0\atop{0}$(980) and f0(980).
From 1310.6 x 10(6) J/psi and 448.1 x 10(6) psi (3686) events collected with the BESIII experiment, we report the first observation of Sigma(+) and (Sigma) over bar (-) spin polarization in e(+)e(-) ...-> J/psipsi(3686) -> Sigma(+)(Sigma) over bar (-) decays. The relative phases of the form factors Delta Phi have been measured to be (-15.5 +/- 0.7 +/- 0.5)degrees and (21.7 +/- 4.0 +/- 0.8)degrees with J/psi and psi(3686) data, respectively. The nonzero value of Delta Phi allows for a direct and simultaneous measurement of the decay asymmetry parameters of Sigma(+)-> p pi(0) (alpha(0) = -0.998 +/- 0.037 +/- 0.009) and (Sigma) over bar (-)-> (p) over bar pi(0) ((alpha) over bar (0) = 0.990 +/- 0.037 +/- 0.011), the latter value being determined for the first time. The average decay asymmetry, (alpha(0 )- (alpha) over bar (0))/2, is calculated to be -0.994 +/- 0.004 +/- 0.002. The CP asymmetry A(CP,Sigma) = (alpha(0) + (alpha) over bar (0))/(alpha(0) - (alpha) over bar (0)) = -0.004 +/- 0.037 +/- 0.010 is extracted for the first time, and is found to be consistent with CP conservation.
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