10137265
Next-to-leading-order QCD corrections to J/psi polarization at Tevatron and Large-Hadron-Collider energies.
We calculate the next-to-leading-order QCD corrections to J/psi polarization at the Fermilab Tevatron and CERN Large Hadron Collider. Our results show that the J/psi polarization status drastically changes from transverse-polarization dominant at leading order to longitudinal-polarization dominant at next-to-leading order. Although the theoretical evaluation predicts a larger longitudinal polarization than the value measured at the Tevatron, it may provide a solution towards the previous large discrepancy for J/psi polarization between theoretical predication and experimental measurement.
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.
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.
119071655
The $J/\psi$ production associated with a hard photon and the color octet signature in $e^{+} e^{-}$ annihilation
$J/\ensuremath{\psi}$ production associated with a hard photon in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation, being of a QED nature, is investigated thoroughly in this paper. To show its influence on the observation of the color-octet signature in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation via $J/\ensuremath{\psi}$ inclusive production, the cross sections of $J/\ensuremath{\psi}$ production through different mechanisms at various energies are compared quantitatively by presenting them in figures together. The contribution from the production associated with a hard photon to the inclusive production of $J/\ensuremath{\psi}$ is pointed out to be significant at the concerned energies; thus, the influence of it on the observation of the color-octet signature should be dealt with carefully.
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.
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.
44320275
Next-to-leading QCD effect on the quark compositeness search at the LHC.
We present the exact next-to-leading order (NLO) QCD corrections to the dijet production induced by the quark contact interactions at the CERN Large Hadron Collider. We show that, as compared to the exact calculation, the scaled NLO QCD prediction adopted by the ATLAS Collaboration has overestimated the new physics effect on some direct observables by more than 30% and renders a higher limit on the quark compositeness scale. The destructive contribution from the exact NLO correction will also lower the compositeness scale limit set by the CMS Collaboration.
119257780
Model independent analysis of top quark forward-backward asymmetry at the Tevatron up to $\mathcal{O}(\as^2/\Lambda^2)$
We present the complete calculations of the forward-backward asymmetry ($A_{\rm FB}$) and the total cross section of top quark pair production induced by dimension-six four quark operators at the Tevatron up to $\mathcal{O}(\as^2/\Lambda^2)$. Our results show that next-to-leading order (NLO) QCD corrections can change $A_{\rm FB}$ and the total cross section by about 10%. Moreover, NLO QCD corrections reduce the dependence of $A_{\rm FB}$ and total cross section on the renormalization and factorization scales significantly. We also evaluate the total cross section and the charge asymmetry ($A_{\rm C}$) induced by these operators at the Large Hadron Collider (LHC) up to $\mathcal{O}(\as^2/\Lambda^2)$, for the parameter space allowed by the Tevatron data. We find that the value of $A_{\rm C}$ induced by these operators is much larger than SM prediction, and LHC has potential to discover these NP effects when the measurement precision increases.
118589254
A CHANDRA STUDY OF THE ROSETTE STAR-FORMING COMPLEX. III. THE NGC 2237 CLUSTER AND THE REGION'S STAR FORMATION HISTORY
We present high spatial resolution Chandra X-ray images of the NGC 2237 young stellar cluster on the periphery of the Rosette Nebula. We detect 168 X-ray sources, 80% of which have stellar counterparts in USNO, Two Micron All Sky Survey, and deep FLAMINGOS images. These constitute the first census of the cluster members with 0.2 {approx}< M {approx}< 2 M {sub sun}. Star locations in near-infrared color-magnitude diagrams indicate a cluster age around 2 Myr with a visual extinction of 1 {approx}< A{sub V} {approx}< 3 at 1.4 kpc, the distance of the Rosette Nebula's main cluster NGC 2244. We derive the K-band luminosity function and the X-ray luminosity function of the cluster, which indicate a population {approx}400-600 stars. The X-ray-selected sample shows a K-excess disk frequency of 13%. The young Class II counterparts are aligned in an arc {approx}3 pc long suggestive of a triggered formation process induced by the O stars in NGC 2244. The diskless Class III sources are more dispersed. Several X-ray emitting stars are located inside the molecular cloud and around gaseous pillars projecting from the cloud. These stars, together with a previously unreported optical outflow originating inside the cloud, indicate that star formation ismore » continuing at a low level and the cluster is still growing. This X-ray view of young stars on the western side of the Rosette Nebula complements our earlier studies of the central cluster NGC 2244 and the embedded clusters on the eastern side of the Nebula. The large-scale distribution of the clusters and molecular material is consistent with a scenario in which the rich central NGC 2244 cluster formed first, and its expanding H II region triggered the formation of the now-unobscured satellite clusters Rosette Molecular Cloud (RMC) XA and NGC 2237. A large swept-up shell material around the H II region is now in a second phase of collect-and-collapse fragmentation, leading to the recent formation of subclusters. Other clusters deeper in the molecular cloud appear unaffected by the Rosette Nebula expansion.« less
209835030
Alignment of the CMS Silicon Tracker during Commissioning with Cosmic Rays
This is the Pre-print version of the Article. The official published version of the Paper can be accessed from the link below - Copyright @ 2010 IOP
126572691
Simulations of wake effects on a high-current electron beam at the KEKB injector linac