118632086
J/psi polarization in photoproduction up to the next-to-leading order of QCD
We investigate the J/psi polarization in photoproduction at the Hadron Electron Ring Accelerator (HERA) up to the next-to-leading order of QCD. The results show that the transverse momentum p(t) and energy fraction z distributions of J/psi production do not agree with the observed ones very well. The theoretical uncertainties for the z distributions of the J/psi polarization parameters with respect to various choices of the renormalization and factorization scales are too large to give a definite predication. The uncertainties for the p(t) distributions of these parameters are small when p(t) > 3 GeV and the obtained p(t) distributions cannot describe the experimental data even in this region.
123412047
UNIVERSALLY TREATING THE QUARK PAIR WITH A VACUUM QUANTUM NUMBER IN THE RELATED CHARM DECAYS
A method for universally treating the quark pair with a vacuum quantum number is proposed and it is applied to calculating some charm meson decays as examples. The smallness for W-exchange and annihilation mechanisms has new explanation and the result obtained by means of the proposed method on the decay fits the experimental data well.
118291411
Next-to-Leading-Order QCD corrections to $J/\psi (\upsilon) + \gamma$ production at the LHC
In this work, we calculate the next-to-leading-order (NLO) QCD corrections to the process $p+p \to J/\psi + \gamma$ via the color-singlet mechanism at the LHC. The results show that the partial cross section ($p_t^{J/\psi}>$3GeV and $|y^{J/\psi,\gamma}|<$3) is enhanced by a factor of about 2.0, and the differential cross section can be enhanced by two orders of magnitude in the large transverse momentum region of $J/\psi$. Furthermore, the polarization of $J/\psi$ changes from transverse polarization at leading-order to longitudinal polarization at NLO. For the inclusive $J/\psi$ hadroproduction, it is known that the color-octet contributions are one order of magnitude larger than the color-singlet contribution, and the polarization distribution is dominated by the color-octet behavior at NLO. In contrast, for $J/\psi+\gamma$ production the color-singlet contribution is of the same order as the color-octet contribution, and the polarization distribution arises from both the color-singlet and color-octet. Therefore, measurements of $J/\psi$ production associated with a direct photon at the hadron collider could be an important supplement to testify the theoretical framework treating with the heavy quarkonium. In addition, an NLO QCD correction to $\Upsilon+\gamma$ production at the LHC is also presented in this paper.
118808651
Inclusive J/\psi Production In \Upsilon Decay Via Color-singlet Mechanism
In this work, we have calculated the tree level color-singlet contribution to the inclusive $J/\ensuremath{\psi}$ production in $\ensuremath{\Upsilon}$ decay of the ${\ensuremath{\alpha}}_{s}^{5}$ order QCD process $\ensuremath{\Upsilon}\ensuremath{\rightarrow}J/\ensuremath{\psi}+c\overline{c}g$ and ${\ensuremath{\alpha}}^{2}{\ensuremath{\alpha}}_{s}^{2}$ order QED processes $\ensuremath{\Upsilon}\ensuremath{\rightarrow}{\ensuremath{\gamma}}^{*}\ensuremath{\rightarrow}J/\ensuremath{\psi}+c\overline{c}$ and $\ensuremath{\Upsilon}\ensuremath{\rightarrow}J/\ensuremath{\psi}+gg$. It is found that the contribution of the QED processes is comparable with that of the QCD process and the numerical results of the QCD process alone are about an order of magnitude smaller than the previous theoretical predictions. Our prediction in total is $4.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ which is about an order of magnitude smaller than the recent CLEO measurement on the branching fraction $\mathcal{B}(\ensuremath{\Upsilon}\ensuremath{\rightarrow}J/\ensuremath{\psi}+X)$. It indicates that the $J/\ensuremath{\psi}$ production mechanism in $\ensuremath{\Upsilon}$ decay is not well understood and further theoretical work and experimental analysis are still necessary.
124445984
The Chiral Anomalies in W and Z Decays
Some of the important W± and Z decay amplitudes, relating to the chiral anomalies of the quark sector in the Standard Model, are given by means of the interactions determined by the effective Lagrangian (action) of the nonlinear σ model for the pseudogoldstone bosons. The corresponding decay rates are calculated. It is shown that the decay rates are quite large, especially, the rate of the decay W →πγ and probably that of W → Dsγ are predicted being unexpectedly great (ΓW→πγ = 0.35 GeV). This indicates that the chiral anomalies and our approach should receive tests from SPPS and Tevantron experiments.
32063766
Next-to-leading-order QCD corrections to e+e- -->J/psi gg at the B factories.
We calculate the next-to-leading-order (NLO) QCD corrections to e;{+}e;{-}-->J/psi gg via color singlet J/psi(3S1) at the B factories. The result shows that the cross section is enhanced to 0.373 pb by a K factor (NLO/LO) of about 1.21. By considering its dependence on the charm quark mass and renormalization scale, the NLO cross section can range from 0.294 to 0.409 pb. Further including the psi;{'} feed-down, sigma[e;{+}e;{-}-->J/psi X(non-cc[over ])] is enhanced by another factor of about 1.29 and reach 0.482 pb. In addition, the momentum distributions of J/psi production and polarization are presented. Recent measurements from Belle agree well with our prediction for the cross section and momentum distribution. It is expected that this process can serve as a very good channel to clarify the J/psi polarization puzzle by performing further experimental measurements.
117815272
${\mathcal O}(\alpha_s v^2)$ correction to $J/\psi$ plus $\eta_c$ production in $e^+e^-$ annihilation at $\sqrt{s}=10.6GeV
Based on the nonrelativistic QCD factorization approach, ${\mathcal O}(\alpha_s v^2)$ corrections to $\jpsi$ plus $\eta_c$ production in $e^+e^-$ annihilation at $\sqrt{s}=10.6 \gev$ is calculated in this work. The numerical results show that the correction at $\alpha_s v^2$ order is only about a few percent for the total theoretical result. It indicates that the perturbative expansions for the theoretical prediction become convergence and higher order correction will be smaller. The uncertainties from the long-distance matrix elements, renormalization scale and the measurement in experiment are also discussed. Our result is in agreement with previous result in ref [1].
10811384
Measurement of associated W + charm production in pp collisions at $ \sqrt{s} $ = 7 TeV
A bstractMeasurements are presented of the associated production of a W boson and a charm-quark jet (W + c) in pp collisions at a center-of-mass energy of 7 TeV. The analysis is conducted with a data sample corresponding to a total integrated luminosity of 5 fb−1, collected by the CMS detector at the LHC. W boson candidates are identified by their decay into a charged lepton (muon or electron) and a neutrino. The W + c measurements are performed for charm-quark jets in the kinematic region $ p_{\mathrm{T}}^{\mathrm{jet}} $> 25 GeV, |ηjet| < 2.5, for two different thresholds for the transverse momentum of the lepton from the W-boson decay, and in the pseudorapidity range |ηℓ| < 2.1. Hadronic and inclusive semileptonic decays of charm hadrons are used to measure the following total cross sections: σ(pp → W + c + X) × $ \mathcal{B} $(W → ℓν) = 107.7 ± 3.3 (stat.) ± 6.9 (syst.) pb ($ p_{\mathrm{T}}^{\ell } $> 25 GeV) and σ(pp → W + c + X)×$ \mathcal{B} $(W → ℓν) = 84.1 ± 2.0 (stat.) ± 4.9 (syst.) pb ($ p_{\mathrm{T}}^{\ell } $> 35 GeV), and the cross section ratios σ(pp → W+ + $ \overline{c} $ + X)/σ(pp → W− + c + X) = 0.954 ± 0.025 (stat.) ± 0.004 (syst.) ($ p_{\mathrm{T}}^{\ell } $> 25 GeV) and σ(pp → W+ + $ \overline{\mathrm{c}} $ + X)/σ(pp → W− + c + X) = 0.938 ± 0.019 (stat.) ± 0.006 (syst.) ($ p_{\mathrm{T}}^{\ell } $> 35 GeV). Cross sections and cross section ratios are also measured differentially with respect to the absolute value of the pseudorapidity of the lepton from the W-boson decay. These are the first measurements from the LHC directly sensitive to the strange quark and antiquark content of the proton. Results are compared with theoretical predictions and are consistent with the predictions based on global fits of parton distribution functions.

118350998
Next-to-leading order QCD predictions for graviton and photon associated production in the Large Extra Dimensions model at the LHC
We present the calculations of the complete next-to-leading order (NLO) QCD corrections to the inclusive total cross sections for the Kaluza-Klein (KK) graviton and photon associated production process pp{yields}{gamma}G{sub KK}+X in the large extra dimensions model at the LHC. We show that the NLO QCD corrections in general enhance the total cross sections and reduce the dependence of the total cross sections on the factorization and renormalization scales. When jet veto is considered, the NLO corrections reduce the total cross sections. We also calculate some important differential cross sections for this process at NLO: the missing transverse momentum distribution, the transverse momentum distribution, and the pseudorapidity distribution of photon.
117483857
Search for quark contact interactions in dijet angular distributions in pp collisions at s=7 TeV measured with the ATLAS detector
Dijet angular distributions from the first LHC pp collisions at center-of-mass energy sqrt(s) = 7 TeV have been measured with the ATLAS detector. The dataset used for this analysis represents an integrated luminosity of 3.1 pb-1. Dijet $\chi$ distributions and centrality ratios have been measured up to dijet masses of 2.8 TeV, and found to be in good agreement with Standard Model predictions. Analysis of the $\chi$ distributions excludes quark contact interactions with a compositeness scale $\Lambda$ below 3.4 TeV, at 95% confidence level, significantly exceeding previous limits.
125141344
Studies of B0 ---> rho+- pi-+ and evidence of B0 ----> rho0 pi0