16136601
Precise QCD predictions on top quark pair production mediated by massive color-octet vector boson at hadron colliders
We present a theoretical framework for systematically calculating next-to-leading order (NLO) QCD effects to various experimental observables in models with massive COVB in a model independent way at hadron colliders. Specifically, we show the numerical results for the NLO QCD corrections to total cross sections, invariant mass distribution and AFB of top quark pairs production mediated by a massive COVB in both the fixed scale (top quark mass) scheme and the dynamical scale (top pair invariant mass) scheme. Our results show that the NLO QCD calculations in the dynamical scale scheme is more reasonable than the fixed scheme and the naive estimate of the NLO effects by simple rescaling of the LO results with the SM NLO K-factor is not appropriate.
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.
118458984
Next-to-leading order QCD predictions for the signal of dark matter and photon associated production at the LHC
We study the potential of the LHC to discover the signal of dark matter associated production with a photon induced by a dimension six effective operator, including next-to-leading order QCD corrections. We investigate the main backgrounds from the standard model, i.e. $Z$ boson and a photon associated production with invisible decay of $Z$ boson, and $Z$ boson and a jet production with the jet misidentified as a photon. We find that the ${p}_{T}^{\ensuremath{\gamma}}$ distributions of the backgrounds decrease faster than that of the signal with increasing of the transverse momentum of the photon. The ${\ensuremath{\eta}}^{\ensuremath{\gamma}}$ distributions of the backgrounds are almost flat in the full range of ${\ensuremath{\eta}}^{\ensuremath{\gamma}}$. In contrast, the signal lies mainly in the central region of ${\ensuremath{\eta}}^{\ensuremath{\gamma}}$. These characteristics may help to select the events in experiments. We show that in the parameter space allowed by the relic abundance constraint, which we have calculated at the next-to-leading-order QCD level, the LHC with $\sqrt{S}=7\text{ }\text{ }\mathrm{TeV}$ may discover this signal at the $5\ensuremath{\sigma}$ level after collecting an integrated luminosity of $1\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$. On the other hand, if this signal is not observed at the LHC, we can set a lower limit on the new physics scale at the $3\ensuremath{\sigma}$ level.
117852493
Factorization and resummation of s-channel single top quark production
We study the factorization and resummation of s-channel single top quark production in the Standard Model at both the Tevatron and the LHC. We show that the production cross section in the threshold limit can be factorized into a convolution of hard function, soft function and jet function via soft-collinear effective theory (SCET), and resummation can be performed using renormalization group equation in the momentum space resummation formalism. We find that the resummation effects significantly reduce the factorization scale dependence of the total cross section at the Tevatron, while at the LHC we find that the factorization scale dependence has not been improved, compared with the NLO results.
119253997
Constraints on flavor-changing neutral-current $Htq$ couplings from the signal of $tH$ associated production with QCD next-to-leading order accuracy at the LHC
We study a generic Higgs boson and a top quark associated production via model-independent flavor-changing neutral-current couplings at the LHC, including complete QCD next-to-leading order (NLO) corrections to the production and decay of the top quark and the Higgs boson. We find that QCD NLO corrections can increase the total production cross sections by about 48.9% and 57.9% for the Htu and Htc coupling induced processes at the LHC, respectively. After kinematic cuts are imposed on the decay products of the top quark and the Higgs boson, the QCD NLO corrections are reduced to 11% for the Htu coupling induced process and almost vanish for the Htc coupling induced process. Moreover, QCD NLO corrections reduce the dependence of the total cross sections on the renormalization and factorization scales. We also discuss signals of the
118552734
Next-to-leading order QCD effect of $W'$ on top quark Forward-Backward Asymmetry
We present the calculations of the complete next-to-leading order (NLO) QCD corrections to the total cross section, invariant mass distribution and the forward-backward asymmetry ($\rm A_{FB}$) of top quark pair production mediated by $W'$ boson. Our results show that in the best fit point in the parameter space allowed by data at the Tevatron, the NLO corrections change the new physics contributions to the total cross section slightly, but increase the $\rm A_{FB}$ in the large invariant mass region by about 9%. Moreover, we evaluate the total cross section and charge asymmetry ($\rm{A}_{\rm{C}}$) of top pair production at the LHC, and find that both total cross section and $A_{\rm C}$ can be used to distinguish NP from SM with the integrated luminosity increasing.
27175391
Microwave Cold-Testing Techniques for the NLC *
The R & D program for the Next Linear Collider Test Accelerator (NLCTA) includes the development of microwave techniques for testing Xband accelerating structures at different stages of design, manufacturing and assembly. During the design phase, short stacks were built and tested to finalize dimensions. Cell by cell measurements were performed on the NLCTA injector cells as a microwave quality control (QC) after manufacturing. The two injector sections were tuned using a moveable plunger and tested using a semiautomated system of bead-pull. Using this perturbation technique, we were able to map the amplitude and phase of the electric field on the axis throughout the assembled structures under traveling-wave conditions. The development of high-gradient X-band accelerator sections for the Next Linear Collider (NLC), requires low power rf testing techniques that ensure the precise and reliable performance of these sections. For this reason, the NLC Test Accelerator (NLCTA) project [1] provides for an R & D program to develop the low-power testing techniques. These characterizing techniques are aimed at supporting different development phases of the accelerator sections; from the design, through manufacturing, and finally testing of the complete accelerator section. In Fig. 1 we summarize the series of tests that can be used through the development phases of an accelerator section. In this paper, we will outline some of the above testing techniques. Results of measurements performed on the two NLCTA injector sections are presented as examples of the implementation of these testing techniques.
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].
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.
122796602
Performance of the CMS cathode strip chambers with cosmic rays
The Cathode Strip Chambers (CSCs) constitute the primary muon tracking device in 
the CMS endcaps. Their performance has been evaluated using data taken during a cosmic ray 
run in fall 2008. Measured noise levels are low, with the number of noisy channels well below 
1%. Coordinate resolution was measured for all types of chambers, and fall in the range 47 µm to 
243 µm. The efficiencies for local charged track triggers, for hit and for segments reconstruction 
were measured, and are above 99%. The timing resolution per layer is approximately 5 ns.
6830698
Evolution of Cross-Correlation and Time Lag of Cyg X-2 Along the Branches
We report the detections of the anticorrelated soft and hard X-rays, and the time lags of ~hectosecond from the neutron star low-mass X-ray binary Cyg X-2, a well-known Z-type luminous source. Both anticorrelation and the positive correlation were detected during the low-intensity states, while only the latter showed up during high-intensity states. Comparing with the lower part of normal branch and flaring branch, we find that more observations located on the horizontal and the upper normal branches are accompanied with anticorrelation, implying the occurrence of the anticorrelation when there is a low mass accretion rate. So far anticorrelated hard lags of 1000 s timescale are only reported from Galactic black hole candidates in their hard states. Here we provide the first evidence that a similar feature can also be established in neutron star systems such as Cyg X-2. Finally, the possible origins of the observed time lags are discussed under current LMXB models.