Lithium isotope compositions were determined for synthetic calcite and fluid, reported in Füger et al. (2019). Calcite was precipitated at 25 °C, and mineral growth rate and pH varied within the ...range of 10−8.1 ≤ rp (mol m−2 s−1) ≤ 10−7.2 and 6.3 ≤ pH ≤ 9.5, respectively. At pH = 8.25 ± 0.15, the Δ7Licalcite-fluid = δ7Licalcite - δ7Lifluid value of −2.76 ± 0.22‰ (n = 4) was yielded when calcite growth rate was lower than ∼ 10−7.7 (mol m−2 s−1). As calcite growth rate increased, Δ7Licalcite-fluid values progressively decreased to about −4.5‰. The dependence of Li isotope fractionation on calcite growth rate is described by the surface reaction kinetic model developed by DePaolo (2011). In this model the equilibrium and kinetic isotope fractionation factors obtain values of −2.7 ± 0.1‰ and −8.8 ± 0.1‰, respectively. In addition, for experiments performed under similar surface-normalized growth rate of 10−7.7±0.2 (mol m−2 s−1) a significant decrease in Δ7Licalcite-fluid from pH 9.5 to 6.3 was observed. These variations of Δ7Licalcite-fluid as a function of pH for experiments performed under low degrees of solution saturation with respect to calcite point towards the incorporation of two or more Li-bearing species in the solid phase. Thus, the Li isotope composition of the solid reflects the abundance of these species, which depends on solution pH and fluid composition.
Overall the results of this study suggest that both calcite growth rate and pH are parameters that can significantly affect the measured Li isotope fractionation between calcite and fluid. The high sensitivity of Δ7Licalcite-fluid to calcite growth rate observed in this study suggests that a high variability of δ7Licalcite in natural samples, such as foraminifera, brachiopods, and speleothems can be expected in natural environments. The implications for the potential use of elemental and isotope fractionation of Li during calcite formation are discussed in the light of reconstruction of paleo-environmental conditions.
We study the process e^{+}e^{-}→Λ_{c}^{+}Λover ¯_{c}^{-} at twelve center-of-mass energies from 4.6119 to 4.9509 GeV using data samples collected by the BESIII detector at the BEPCII collider. The ...Born cross sections and effective form factors (|G_{eff}|) are determined with unprecedented precision after combining the single and double-tag methods based on the decay process Λ_{c}^{+}→pK^{-}π^{+}. Flat cross sections around 4.63 GeV are obtained and no indication of the resonant structure Y(4630), as reported by Belle, is found. In addition, no oscillatory behavior is discerned in the |G_{eff}| energy dependence of Λ_{c}^{+}, in contrast to what is seen for the proton and neutron cases. Analyzing the cross section together with the polar-angle distribution of the Λ_{c}^{+} baryon at each energy point, the moduli of electric and magnetic form factors (|G_{E}| and |G_{M}|) are extracted and separated. For the first time, the energy dependence of the form factor ratio |G_{E}/G_{M}| is observed, which can be well described by an oscillatory function.
A search for the charged lepton flavor violating decay J/ψ → e± τ∓ with τ∓ → π∓ π0 ντ is performed with about 10 × 10 9 J/ψ events collected with the BESIII detector at the BEPCII. No significant ...signal is observed, and an upper limit is set on the branching fraction B (J/ψ → e± τ∓) < 7.5 × 10−8 at the 90% confidence level. This improves the previously published limit by two orders of magnitude.
Using 6.32 fb–1 of electron-positron collision data recorded by the BESIII detector at center-of-mass energies between 4.178 and 4.226 GeV, we present the first search for the decay $D^{+}_{s}$ → ...a0(980)0e+νe, a0(980)0 → π0η, which could proceed via a0(980) – f0(980) mixing. No significant signal is observed. An upper limit of 1.2 × 10–4 at the 90% confidence level is set on the product of the branching fractions of $D^{+}_{s}$ → a0(980)0e+νe and a0(980)0 → π0η decays.
The decays ψ2(3823 ) → γχc0,1,2, π+π− J/ψ, π0π0J/ψ , ηJ/ψ, and π0J/ψ are searched for using the reaction e+e− → π+π− ψ2 (3823) in a 19 fb−1 data sample collected at center-of-mass energies between ...4.1 and 4.7 GeV with the BESIII detector. The process ψ2(3823) → γχc1 is observed in a 9 fb−1 data sample in the center-of-mass energy range 4.3–4.7 GeV, which confirms a previous observation but with a higher significance of 11.8 σ , and evidence for ψ2(3823) → γχc2 is found with a significance of 3.2 σ for the first time. The branching-fraction ratio ... is determined. No significant ψ2 (3823) signals are observed for any of the other decay channels. Upper limits of branching-fraction ratios for ψ2(3823 ) → π+π− J/ψ , π0π0 J/ψ, ηJ/ψ , π0 J/ψ, γ χc0 relative to ψ2 (3823) → γχc1 are reported. The process e+e− → π0π0ψ2 (3823) is also searched for, and we find evidence for the process with a significance of 4.3 σ . The average cross-section ratio σ (e+e− → π0π0ψ2 (3823)) σ (e+e− → π+π− ψ2 (3823)) is also determined. (ProQuest: ... denotes formula omited.).
A massless particle beyond the Standard Model is searched for in the two-body decay Σ+→p+invisible using (1.0087±0.0044)×1010J/ψ events collected at a center-of-mass energy of s=3.097GeV with the ...BESIII detector at the BEPCII collider. No significant signal is observed, and the upper limit on the branching fraction B(Σ+→p+invisible) is determined to be 3.2×10−5 at the 90% confidence level. This is the first search for a flavor-changing neutral current process with missing energy in hyperon decays which plays an important role in constraining new physics models.
Observation of η ′ → π + π − μ + μ Achasov, M. N.; Adlarson, P.; Ahmed, S. ...
Physical review. D,
04/2021, Letnik:
103, Številka:
7
Journal Article
Recenzirano
Odprti dostop
Using ( 1310.6 ± 7.0 ) × 106 J / ψ events acquired with the BESIII detector at the BEPCII storage rings, the decay η ′ → π+ π−μ+μ− is observed for the first time with a significance of 8 σ via the ...process J / ψ → γ η ′ . We measure the branching fraction of η ′ → π+ π−μ+μ− to be B ( η ′ → π+ π−μ+μ− ) = ( 1.97 ± 0.33 ( stat ) ± 0.19 ( syst ) ) × 10−5, where the first and second uncertainties are statistical and systematic, respectively.
The spin and parity of the charmed mesons Ds⁎+, D⁎0 and D⁎+ are determined for the first time to be JP=1− with significances greater than 10σ over other hypotheses of 2+ and 3−, using an e+e− ...collision data sample with an integrated luminosity of 3.19 fb−1 collected by the BESIII detector at a center-of-mass energy of 4.178 GeV. Different spin-parity hypotheses are tested via a helicity amplitude analysis of the processes e+e−→Ds⁎+Ds−, D⁎0D0 and D⁎+D−, with Ds⁎+→Ds+γ, D⁎0→D0π0, and D⁎+→D+π0. The results confirm the quark model predictions.
A
bstract
Using 15
.
6 fb
−
1
of
e
+
e
−
collision data collected at twenty-four center-of-mass energies from 4
.
0 to 4
.
6 GeV with the BESIII detector, the helicity amplitudes of the process
e
+
e
...−
→
π
+
π
−
ω
are analyzed for the first time. Born cross section measurements of two-body intermediate resonance states with statistical significance greater than 5
σ
are presented, such as
f
0
(500),
f
0
(980),
f
2
(1270),
f
0
(1370),
b
1
(1235)
±
, and
ρ
(1450)
±
. In addition, evidence of a resonance state in
e
+
e
−
→
π
+
π
−
ω
production is found. The mass of this state obtained by line shape fitting is about 4
.
2 GeV/
c
2
, which is consistent with the production of
ψ
(4160) or
Y
(4220).
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