QCD Supersymmetry and Low Energy Gravity

In this contributed paper we discuss some aspects of scenarios with Extra Dimensions at the LHC and in cosmic rays.Comment: Contributed paper to the Conference "Quark confinement ant the Hadron Spectrum VI 2004". Latex, 3 page

Full one-loop amplitudes from tree amplitudes

We establish an efficient polynomial-complexity algorithm for one-loop calculations, based on generalized $D$-dimensional unitarity. It allows automated computations of both cut-constructible {\it and} rational parts of one-loop scattering amplitudes from on-shell tree amplitudes. We illustrate the method by (re)-computing all four-, five- and six-gluon scattering amplitudes in QCD at one-loop.Comment: 27 pages, revte

Classical ultra-relativistic scattering in ADD

The classical differential cross-section is calculated for high-energy small-angle gravitational scattering in the factorizable model with toroidal extra dimensions. The three main features of the classical computation are: (a) It involves summation over the infinite Kaluza-Klein towers but, contrary to the Born amplitude, it is finite with no need of an ultraviolet cutoff. (b) It is shown to correspond to the non-perturbative saddle-point approximation of the eikonal amplitude, obtained by the summation of an infinite number of ladder graphs of the quantum theory. (c) In the absence of extra dimensions it reproduces all previously known results.Comment: 12 pages, minor change

Current care services provided for patients with COPD in the Eastern province in Saudi Arabia: a descriptive study

Background: COPD is a leading cause of morbidity and mortality worldwide. The prevalence rate of COPD in the general Saudi population is estimated to be 2.4% and 14.2% among smokers. Not much is known about current health care services for patients with COPD in Saudi Arabia. The objective of this study was to determine the current care services for patients with COPD provided by government hospitals in the Eastern province of Saudi Arabia. Methods: A cross-sectional study was conducted in the Eastern province of Saudi Arabia. Directors of the Department of Internal Medicine from all 22 general government hospitals that are under the responsibility of the Ministry of Health or the Ministry of Higher Education in this region were asked to participate. Data were collected using a questionnaire. Results: The study results indicated that there are limited hospital facilities for patients with COPD: no respiratory departments in any of the included hospitals, no spirometry in 77.3% of the hospitals, no intensive care units in 63.7% of the hospitals, and no pulmonary rehabilitation program in any of the hospitals. Among the included 22 hospitals, 24 respiratory physicians, 29 respiratory therapists, and three physiotherapists were involved in COPD care. Conclusion: In conclusion, current care services provided by government hospitals in the Eastern province of Saudi Arabia for patients with COPD do not meet international recommendations for COPD management. Increased awareness, knowledge, and implementation of COPD guidelines by health care providers will most probably improve COPD management in Saudi Arabia. In addition, the government could improve dissemination of information about COPD management through national programs and by offering specific education regarding respiratory diseases.Mohammed E Alsubaiei, Paul A Cafarella, Peter A Frith, R Doug McEvoy, Tanja W Effin

Feynman Rules for the Rational Part of the QCD 1-loop amplitudes

We compute the complete set of Feynman Rules producing the Rational Terms of kind R_2 needed to perform any QCD 1-loop calculation. We also explicitly check that in order to account for the entire R_2 contribution, even in case of processes with more than four external legs, only up to four-point vertices are needed. Our results are expressed both in the 't Hooft Veltman regularization scheme and in the Four Dimensional Helicity scheme, using explicit color configurations as well as the color connection language.Comment: 18 pages, 11 figures. Misprints corrected in Appendix A. Version to be published in JHE

NNLO massive corrections to Bhabha scattering and theoretical precision of BabaYaga@NLO

We provide an exact calculation of next-to-next-to-leading order (NNLO) massive corrections to Bhabha scattering in QED, relevant for precision luminosity monitoring at meson factories. Using realistic reference event selections, exact numerical results for leptonic and hadronic corrections are given and compared with the corresponding approximate predictions of the event generator BabaYaga@NLO. It is shown that the NNLO massive corrections are necessary for luminosity measurements with per mille precision. At the same time they are found to be well accounted for in the generator at an accuracy level below the one per mille. An update of the total theoretical precision of BabaYaga@NLO is presented and possible directions for a further error reduction are sketched.Comment: 5 pages, 3 tables, contrib. to proceedings of International Workshop on e+e- collisions: from Phi to Psi, PHIPSI11, BINP, Novosibirsk, Russia, September 19-22, 201

Polarizing the Dipoles

We extend the massless dipole formalism of Catani and Seymour, as well as its massive version as developed by Catani, Dittmaier, Seymour and Trocsanyi, to arbitrary helicity eigenstates of the external partons. We modify the real radiation subtraction terms only, the primary aim being an improved efficiency of the numerical Monte Carlo integration of this contribution as part of a complete next-to-leading order calculation. In consequence, our extension is only applicable to unpolarized scattering. Upon summation over the helicities of the emitter pairs, our formulae trivially reduce to their original form. We implement our extension within the framework of Helac-Phegas, and give some examples of results pertinent to recent studies of backgrounds for the LHC. The code is publicly available. Since the integrated dipole contributions do not require any modifications, we do not discuss them, but they are implemented in the software.Comment: 20 pages, 4 figures, Integrated dipoles implemented for massless and massive case

Efficient Color-Dressed Calculation of Virtual Corrections

With the advent of generalized unitarity and parametric integration techniques, the construction of a generic Next-to-Leading Order Monte Carlo becomes feasible. Such a generator will entail the treatment of QCD color in the amplitudes. We extend the concept of color dressing to one-loop amplitudes, resulting in the formulation of an explicit algorithmic solution for the calculation of arbitrary scattering processes at Next-to-Leading order. The resulting algorithm is of exponential complexity, that is the numerical evaluation time of the virtual corrections grows by a constant multiplicative factor as the number of external partons is increased. To study the properties of the method, we calculate the virtual corrections to $n$-gluon scattering.Comment: 48 pages, 23 figure

Nonperturbative contributions to a resummed leptonic angular distribution in inclusive Z/γ∗Z/\gamma^* boson production

We summarize a new analysis of the distribution $\phi_{\eta}^{*}$ of charged leptons produced in decays of $Z$ and $\gamma^{*}$ bosons in the Collins-Soper-Sterman (CSS) formalism for transverse momentum resummation. By comparing the $\phi_{\eta}^{*}$ distribution measured at the Tevatron with the resummed CSS cross section with approximate ${\cal O}(\alpha_{s}^{2})$ Wilson coefficients, we constrain the magnitude of the nonperturbative Gaussian smearing factor and analyze its uncertainty caused by variations in scale parameters. We find excellent agreement between the $\phi_{\eta}^{*}$ data and our theoretical prediction, provided by the \textsc{ResBos} resummation program. The nonperturbative factor that we obtained can be used to update resummed QCD predictions for precision measurements in inclusive $W$ and $Z$ production and for comparisons to various models of nonperturbative dynamics.Comment: 8 pages, 3 figures. Presented at conference: "The QCD Evolution Workshop", May 14-17 2012, Thomas Jefferson National Accelerator Facility, Newport News, V

Evaluation of the Theoretical Uncertainties in the Z to ll Cross Sections at the LHC

We study the sources of systematic errors in the measurement of the Z to ll cross-sections at the LHC. We consider the systematic errors in both the total cross-section and acceptance for anticipated experimental cuts. We include the best available analysis of QCD effects at NNLO in assessing the effect of higher order corrections and PDF and scale uncertainties on the theoretical acceptance. In addition, we evaluate the error due to missing NLO electroweak corrections and propose which MC generators and computational schemes should be implemented to best simulate the events.Comment: 23 pages, 52 eps figures, LaTeX with JHEP3.cls, epsfig. Added a reference, acknowledgment, and a few clarifying comments. 4/29: Changes in references, minor rewordings and misprint corrections, and one new table (Table 4) comparing CTEQ and MRST PDFs in the NNLO calculation. Version 6 adds email addresses and corrects one referenc