Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userObservation of a cross-section enhancement near mass threshold in $e^{+}e^{-}rightarrowLambdabar{Lambda}$
183
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The process $e^{+}e^{-}rightarrowLambdabar{Lambda}$ is studied using data samples at $sqrt{s}=2.2324$, 2.400, 2.800 and 3.080 GeV collected with the BESIII detector operating at the BEPCII collider. The Born cross section is measured at $sqrt{s}$=2.2324 GeV, which is 1.0 MeV above the $Lambdabar{Lambda}$ mass threshold, to be $305pm45^{+66}_{-36}$ pb, where the first uncertainty is statistical and the second systematic. The substantial cross section near threshold is significantly larger than that expected from theory, which predicts the cross section to vanish at threshold. The Born cross sections at $sqrt{s}$=2.400, 2.800 and 3.080 GeV are measured and found to be consistent with previous experimental results, but with improved precision. Finally, the corresponding effective electromagnetic form factors of $Lambda$ are deduced.
rate research
Read More
We report a measurement of the exclusive e+e- -->Lambda_c+ Lambda_c- cross section as a function of center-of-mass energy near the Lambda_c+ Lambda_c- threshold. A clear peak with a significance of 8.2 sigma is observed in the Lambda_c+ Lambda_c- invariant mass distribution just above threshold. With an assumption of a resonance origin for the observed peak, a mass and width of M=(4634^{+8}_{-7}(stat.)^{+5}_{-8}(sys.))Mev/c2 and Gamma_tot=(92^{+40}_{-24}(stat.)}^{+10}_{-21}(sys.))MeV are determined. The analysis is based on a study of events with initial-state-radiation photons in a data sample collected with the Belle detector at the Upsilon(4S) resonance and nearby continuum with an integrated luminosity of 695/fb at the KEKB asymmetric-energy e+e- collider.
The Born cross section of the $e^{+}e^{-}~rightarrow~Lambda_{c}^{+} bar{Lambda}_{c}^{-}$ process is measured with unprecedented precision using data collected with the BESIII detector at $sqrt{s}=4574.5$, $45580.0$, $4590.0$ and $4599.5$ $mathrm{MeV}$. The non-zero cross section near the $Lambda_{c}^{+} bar{Lambda}_{c}^{-}$ production threshold is discerned. At center-of-mass energies $sqrt{s}=4574.5$ and $4599.5 $ $mathrm{MeV}$, the higher statistics data enable us to measure the $Lambda_{c}$ polar angle distributions. From these, the ratio between the $Lambda_{c}$ electric and magnetic form factors ($|G_{E}/G_{M}|$) is measured for the first time. They are found to be $1.14pm0.14pm0.07$ and $1.23pm0.05pm0.03$ respectively, where the first uncertainties are statistical and the second are systematic.
The process $e^+ e^- to phi Lambda bar{Lambda}$ is studied using data samples collected with the BESIII detector at the BEPCII collider at center-of-mass energies $sqrt{s}$ ranging from $3.51$ to $4.60~{rm GeV}$ . An intermediate resonance structure is observed near the threshold of $Lambda bar{Lambda}$. It has a mass of $(2262 pm 4 pm 28)~{rm{MeV}}/c^{2}$ and a width of $(72 pm 5 pm 43)~rm{MeV}$, where the quoted uncertainties are statistical and systematic, respectively. The $J^{PC}$ quantum numbers of $0^{-+}$ and $0^{++}$ are rejected, while other $J^{PC}$ hypotheses are possible, according to the helicity angle study. The energy-dependent cross section of the $e^+ e^- to phi Lambda bar{Lambda}$ process is measured for the first time in this energy region, and contributions from excited $psi$ states and vector charmonium-like $Y$-states are investigated.
Using $e^+e^-$ collision data at ten center-of-mass energies between 2.644 and 3.080 GeV collected with the BESIII detector at BEPCII and corresponding to an integrated luminosity of about 500 pb$^{-1}$, we measure the cross sections and effective form factors for the process $e^{+}e^{-}rightarrowXi^{0}bar{Xi}^{0}$ utilizing a single-tag method. A fit to the cross section of $e^{+}e^{-}rightarrowXi^{0}bar{Xi}^{0}$ with a pQCD-driven power function is performed, from which no significant resonance or threshold enhancement is observed. In addition, the ratio of cross sections for the processes $e^{+}e^{-}rightarrowXi^{-}bar{Xi}^{+}$ and $Xi^{0}bar{Xi}^{0}$ is calculated using recent BESIII measurement and is found to be compatible with expectation from isospin symmetry.
The Born cross-sections and effective form factors for process $e^+e^-toXi^-bar{Xi}^+$ are measured at eight center-of-mass energies between 2.644 and 3.080 GeV, using a total integrated luminosity of 363.9 pb$^{-1}$ $e^+e^-$ collision data collected with the BESIII detector at BEPCII. After performing a fit to the Born cross-section of $e^+e^-toXi^-bar{Xi}^+$, no significant threshold effect is observed.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
