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Register a new userFragmentation of charm to charmonium in $e^+e^-$ and $pp$ collisions
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We perform numerical comparison of the fragmentation mechanism of charmonium production ($g,gto c,bar{c}$ followed by $ctopsi,c$) with the full leading order calculation ($g,gtopsi,c,bar{c}$ at ${O} (alpha_s^4)$). We conclude that the non-fragmentation contributions remain important up to $J/psi$ transverse momenta about as large as 50 GeV, thus making questionable the applicability of the fragmentation approximation at smaller transverse momenta.
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We report BELLE measurements of the exclusive cross sections for the processes e+e-->DD*, e+e-->DD, e+e-->DDpi, the first observation of psi(4415)-> DD*2(2460)bar decay and new state, Y(4660), using ISR. In addition, another cluster of events at around 4.05GeV/c2 is reported.
We study the possibility of the scalar charmonium and glueball mixing in $e^+ e^-$ annihilation at $sqrt{s}=10.6$ GeV. The effects can be used to explain the unexpected large cross section ($12pm 4$ fb) and the anomalous angular distribution ($alpha= -1.1^{+0.8}_{-0.6}$) of the exclusive $e^+e^-to J/psichi_{c0}$ process observed by Belle experiments at KEKB. We calculate the helicity amplitudes for the process $e^+ e^- to J/psi H(0^{++})$ in NRQCD, where $H(0^{++})$ is the mixed state. We present a detailed analysis on the total cross section and various angular asymmetries which could be useful to reveal the existence of the scalar glueball state.
In continuation of our earlier work, in which we analysed the charged particle multiplicities in leptonic and hadronic interactions at different center of mass energies in full phase space as well as in restricted phase space with the shifted Gompertz distribution, a detailed analysis of the normalized and factorial moments is reported here. A two-component model in which probability distribution function is obtained from the superposition of two shifted Gompertz distributions introduced in our earlier work has also been used for the analysis. This is the first analysis of the moments with the shifted Gompertz distribution. Analysis has also been done to predict the moments of multiplicity distribution for the electron-positron collisions at c.m. energy of 500 GeV at a future Collider.
Large Hadron Collider (LHC) has provided direct evidence of Yukawa couplings between the third generation charged fermions and the 125 GeV Higgs boson. Whether the first two generation charged fermions arise from exactly the same mechanism becomes the next interesting question. Therefore, direct measurements of charm or muon Yukawa couplings will be crucial to answering this puzzle. The charm Yukawa measurement at the LHC suffers from severe QCD background and it is extremely difficult to reach the sensitivity. In this paper, we compare the potential of probing charm Yukawa coupling at the two proposed future Higgs Factory experiments, the Large Hadron electron Collider (LHeC) and Circular electron positron collider (CEPC). At the LHeC, Higgs bosons will be produced via weak boson fusion and the energetic forward jet may suppress the background significantly. However, due to huge $gamma-g$ scattering background, the potential of LHeC search is still limited. With $-80%$ polarized electron beam of 60 GeV, the signal significance can only reach $2sigma$ for $ kappa_{c}simeq 1$ with a 3 ab$^{-1}$ integrated luminosity. In comparison, measurement at the CEPC can then reach $8.0sigma$ for $kappa_{c}simeq 1$ with a 2 ab$^{-1}$ of data.
Using a model calculation of dihadron fragmentation functions, we fit the spin asymmetry recently extracted by HERMES for the semi-inclusive pion pair production in deep-inelastic scattering on a transversely polarized proton target. By evolving the obtained dihadron fragmentation functions, we make predictions for the correlation of the angular distributions of two pion pairs produced in electron-positron annihilations at BELLE kinematics. Our study shows that the combination of two-hadron inclusive deep-inelastic scattering and electron-positron annihilation measurements can provide a valid alternative to Collins effect for the extraction of the quark transversity distribution in the nucleon.
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