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.
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.
3155142
Further study on U(1) gauge invariance restoration
To further investigate the applicability of the projection scheme for eliminating the unphysical divergence s/m(e)(2) due to U(1) gauge invariance violation, we study the process e(-) + W+ --> e(-) + (t) over bar + b which possesses advantages of simplicity and clearness. Our study indicates that the projection scheme can indeed eliminate the unphysical divergence s/m(e)(2) caused by the U(1) gauge invariance violation and the scheme can be applied to very high energy region.
33938812
Projection scheme for handling large-number cancellation related to gauge invariance.
A scheme, the so-called {open_quote}{open_quote}projection,{close_quote}{close_quote} for handling singularities in processes such as {ital e}{sup +}{ital e}{sup {minus}}{r_arrow}{ital t{bar b}e{sup {minus}}}{bar {nu}} (or {ital e}{sup +}{ital e}{sup {minus}}{r_arrow}{ital u{bar d}e{sup {minus}}}{bar {nu}}) is proposed. In the scheme, with the help of gauge invariance, the large power quantities ({ital s}/{ital m}{sup 2}{sub {ital e}}){sup {ital n}} ({ital n}{ge}1;{ital s}{r_arrow}{infinity}) are removed from the calculation totally, while in the usual schemes the large quantities appear and only will be canceled at last. The advantages of the scheme in numerical calculations are obvious; thus, we focus our discussions mainly on the advantages of the scheme in the special case where the absorptive part for some propagators relevant to the process could not be ignored, and a not satisfactory but widely adopted approximation is made; i.e., a finite constant {open_quote}{open_quote}width{close_quote}{close_quote} is introduced to approximate the absorptive part of the propagators phenomenologically even though QED gauge invariance is violated. {copyright} {ital 1996 The American Physical Society.}
119107795
Improved Resummation Prediction on Higgs Boson Production at Hadron Colliders
We improve the resummation calculations in the ResBos program for the Higgs boson production via gluon-gluon fusion by including the NNLO Wilson coefficient functions and G-functions. The improvement leads to increasing the total cross section predictions of the new ResBos program, dubbed as ResBos2, for Higgs boson production by about 8% and 6% at the Tevatron and the LHC, respectively, as compared to the old ResBos program. Furthermore, the improved predictions are compared with those from the programs HNNLO and HqT2. We find that they agree well for the total cross sections but differ slightly for the transverse momentum QT distributions. With ResBos2, we present the distributions of the two variables aT and � � , which can have better experimental resolutions than QT, for the process of Higgs boson decaying into a photon pair. Theoretical uncertainties of the ResBos2 predictions are also discussed.
990161
Searches for electroweak production of charginos, neutralinos, and sleptons decaying to leptons and W, Z, and Higgs bosons in pp collisions at 8 TeV
Searches for the direct electroweak production of supersymmetric charginos, neutralinos, and sleptons in a variety of signatures with leptons and $$\mathrm{W}$$W, $$\mathrm{Z}$$Z, and Higgs bosons are presented. Results are based on a sample of proton-proton collision data collected at center-of-mass energy $$\sqrt{s}=8\,\mathrm{TeV}$$s=8TeV with the CMS detector in 2012, corresponding to an integrated luminosity of 19.5 $$\,\text {fb}^\text {-1}$$fb-1. The observed event rates are in agreement with expectations from the standard model. These results probe charginos and neutralinos with masses up to 720 $$\,\text {GeV}$$GeV, and sleptons up to 260 $$\,\text {GeV}$$GeV, depending on the model details.
11911902
Performance of prototype BTeV silicon pixel detectors in a high-energy pion beam
Abstract The silicon pixel vertex detector is a key element of the BTeV spectrometer. Sensors bump bonded to prototype front-end devices were tested in a high-energy pion beam at Fermilab. The spatial resolution and occupancies as a function of the pion incident angle were measured for various sensor-readout combinations. The data are compared with predictions from our Monte Carlo simulation and very good agreement is found.
28811657
Observation of D+(s)K- and evidence for D+(s)pi- final states in neutral B decays.
We report the first observation of a B meson decay that is not accessible by a direct spectator process. The channel B(0)-->D(+)(s)K- is found in a sample of 85 x 10(6) BB; events, collected with the Belle detector at KEKB, with a branching fraction B(B(0)-->D(+)(s)K-)=(4.6(+1.2)(-1.1)+/-1.3) x 10(-5). We also obtain evidence for the B0-->D(+)(s)pi(-) decay with branching fraction B(B0-->D(+)(s)pi(-))=(2.4(+1.0)(-0.8)+/-0.7) x 10(-5). This value may be used to extract a model-dependent value of |V(ub)|.
118444339
Threshold resummation effects in Higgs boson pair production at the LHC
A bstractWe investigate the resummation effects in the Standard Model Higgs boson pair production through gluon-gluon fusion at the LHC with soft-collinear effective theory. We calculate the total cross section and the invariant mass distribution at Next-to-Next-to-Leading-Logarithmic level with π2-enhanced terms resummed, which are matched to the QCD Next-to-Leading Order results. In the high order QCD predictions exact top quark mass effects are included in full form factors. Our results show that the resummation effects increase the Next-to-Leading Order results by about 20% ~ 30%, and the scale uncertainty is reduced to 8%, which leads to increased confidence on the theoretical predictions. The PDF+αs uncertainties are almost not changed after including resummation effects. We also study the sensitivities of the total cross section and the invariant mass distribution to the Higgs boson self-coupling. We find that the total cross section and the invariant mass distribution shape depend strongly on the Higgs boson self-coupling, and therefore it is possible to extract Higgs boson self-coupling from the total cross section and invariant mass distribution when the measurement precision increases at the LHC.