Multi-jet cross sections at NLO with BlackHat and Sherpa

In this talk, we report on a recent next-to-leading order QCD calculation of the production of a W boson in association with three jets at hadron colliders. The computation is performed by combining two programs, BlackHat for the computation of the virtual one-loop matrix elements and Sherpa for the real emission part.Comment: 4 pages, contribution to the proceedings of the XLIIIth Rencontres de Moriond (QCD

Next-to-Leading Order Jet Physics with BlackHat

We present several results obtained using the BlackHat next-to-leading order QCD program library, in conjunction with SHERPA. In particular, we present distributions for vector boson plus 1,2,3-jet production at the Tevatron and at the asymptotic running energy of the Large Hadron Collider, including new Z+3-jet distributions. The Z+2-jet predictions for the second-jet P_T distribution are compared to CDF data. We present the jet-emission probability at NLO in W+2-jet events at the LHC, where the tagging jets are taken to be the ones furthest apart in pseudorapidity. We analyze further the large left-handed W polarization, identified in our previous study, for W bosons produced at high P_T at the LHC.Comment: Presented at RADCOR 2009 - 9th International Symposium on Radiative Corrections (Applications of Quantum Field Theory to Phenomenology), October 25 - 30 2009, Ascona, Switzerland}, 12 pages, 9 figures, LaTeX, v2 updated small correction to polarization effect plo

Estimation of liveweight from chest circumference in double purpose crossbred calves during growth as a function of sex and racial group in the Maracaibo Lake basin

With the objective of estimating live weight (LW) as a function of racial group and sex and calculating its relationship to chest circumference (CC) in growing crossbred double purpose calves under tropical conditions, 589 measurements were taken of animals in three herds distributed in the Maracaibo Lake basin and grouped by predominant race (indicus or Taurus) and sex. General analysis of the data yielded a correlation between LW and CC (P <0.001) with R2 = 0.96. The corresponding exponential (quadratic) general regression equation was LW = 115.10 + (-2.83 × CC) + (0.03 × CC2); LW in kg and CC in cm. Sex had a highly significant effect (P<0.001) on both LW and CC, but the racial group did not. According to these results, CC is a good indicator of LW in double purpose cattle during growth. The data were used to prepare a table presenting the variations of LW and CC, which can be used on farms not possessing a weight scale to estimate LW changes in the animals

Predicción de peso de carcasa a la edad de beneficio en cuyes del genotipo Cieneguilla con base a una síntesis de medidas corporales

The objective of the present study was to predict carcass weight (PC) in guinea pigs (Cavia porcellus) at the age of slaughtering (16±2 weeks), considering their biometric measurements. The following measures and weights were taken before and after the slaughter of 150 male guinea pigs of the Cieneguilla genotype: live body weight (PV), body length (LC), head length (LCA), head width (AC), loin length (LL), loin width (AL), chest girth (PT), thigh perimeter (PM), thigh length (LM), arm perimeter (PB), arm length (LB), and rump middle square (CMG), as well as the carcass weight (PC). The data were analyzed to determine the best regression equation and to establish the best predictive linear model of carcass weight. The «Step-Wise Regression» process of the SAS statistical package was used. The combinations of independent variables in the model revealed that the variables PV, PT, AC, and LL give a better explanation of the CP at the benefit age (R2=0.71; Cp-Mallows=1.63).El objetivo del presente estudio fue predecir el peso de carcasa (PC) en cuyes (Cavia porcellus) a la edad de beneficio (16 ± 2 semanas), tomando como referencia sus medidas biométricas. Se tomaron las siguientes medidas y pesos antes y después del beneficio a 150 cuyes machos del genotipo Cieneguilla: peso vivo al beneficio (PV), largo de cuerpo (LC), largo de cabeza (LCA), ancho de cabeza (AC), largo de lomo (LL), ancho de lomo (AL), perímetro torácico (PT), perímetro de muslo (PM), largo de muslo (LM), perímetro de brazuelo (PB), largo de brazuelo (LB) y cuadrado medio de la grupa (CMG), así como el peso de carcasa (PC). Los datos fueron analizados para determinar la mejor ecuación de regresión y establecer el mejor modelo lineal predictivo del peso de carcasa. Se utilizó el proceso «Step-Wise Regression» del paquete estadístico SAS. Las combinaciones de variables independientes en el modelo revelaron que las variables PV, PT, AC y LL dan una mejor explicación del PC a la edad de beneficio (R2 =0.71; Cp-Mallows=1.63)

Heavy-quark mass dependence in global PDF analyses and 3- and 4-flavour parton distributions

We study the sensitivity of our recent MSTW 2008 NLO and NNLO PDF analyses to the values of the charm- and bottom-quark masses, and we provide additional public PDF sets for a wide range of these heavy-quark masses. We quantify the impact of varying m_c and m_b on the cross sections for W, Z and Higgs production at the Tevatron and the LHC. We generate 3- and 4-flavour versions of the (5-flavour) MSTW 2008 PDFs by evolving the input PDFs and alpha_S determined from fits in the 5-flavour scheme, including the eigenvector PDF sets necessary for calculation of PDF uncertainties. As an example of their use, we study the difference in the Z total cross sections at the Tevatron and LHC in the 4- and 5-flavour schemes. Significant differences are found, illustrating the need to resum large logarithms in Q^2/m_b^2 by using the 5-flavour scheme. The 4-flavour scheme is still necessary, however, if cuts are imposed on associated (massive) b-quarks, as is the case for the experimental measurement of Z b bbar production and similar processes.Comment: 40 pages, 11 figures. Grids can be found at http://projects.hepforge.org/mstwpdf/ and in LHAPDF V5.8.4. v2: version published in EPJ

One-Loop Calculations with BlackHat

We describe BlackHat, an automated C++ program for calculating one-loop amplitudes, and the techniques used in its construction. These include the unitarity method and on-shell recursion. The other ingredients are compact analytic formulae for tree amplitudes for four-dimensional helicity states. The program computes amplitudes numerically, using analytic formulae only for the tree amplitudes, the starting point for the recursion, and the loop integrals. We make use of recently developed on-shell methods for evaluating coefficients of loop integrals, in particular a discrete Fourier projection as a means of improving numerical stability. We illustrate the good numerical stability of this approach by computing six-, seven- and eight-gluon amplitudes in QCD and comparing against known analytic results.Comment: To appear in the proceedings of 9th Workshop on Elementary Particle Theory: Loops and Legs in Quantum Field Theory, Sondershausen, Germany, 20-25 Apr 200

Towards W b bbar + j at NLO with an automatized approach to one-loop computations

We present results for the O(alpha_s) virtual corrections to q g -> W b bbar q' obtained with a new automatized approach to the evaluation of one-loop amplitudes in terms of Feynman diagrams. Together with the O(alpha_s) corrections to q q' -> W b bbar g, which can be obtained from our results by crossing symmetry, this represents the bulk of the next-to-leading order virtual QCD corrections to W b bbar + j and W b + j hadronic production, calculated in a fixed-flavor scheme with four light flavors. Furthermore, these corrections represent a well defined and independent subset of the 1-loop amplitudes needed for the NNLO calculation of W b bbar. Our approach was tested against several existing results for NLO amplitudes including selected O(alpha_s) one-loop corrections to W + 3 j hadronic production. We discuss the efficiency of our method both with respect to evaluation time and numerical stability.Comment: 14 pages, 3 figure

Arrest History and Intimate Partner Violence Perpetration in a Sample of Men and Women Arrested for Domestic Violence

Intimate partner violence (IPV) is a serious and prevalent problem throughout the United States. Currently, individuals arrested for domestic violence are often court mandated to batterer intervention programs (BIPs). However, little is known about the arrest histories of these individuals, especially women. The current study examined the arrest histories of men (n = 303) and women (n = 82) arrested for domestic violence and court-referred to BIPs. Results demonstrated that over 30% of the entire sample had been previously arrested for a non-violent offense, and over 25% of the participants had been previously arrested for a violent offense other than domestic violence. Moreover, men were arrested significantly more frequently for violence-related and non-violent offenses than their female counterparts. In addition, men were more likely than women to have consumed binge-levels of alcohol prior to the offense that led to their most recent arrest and court-referral to a BIP. Lastly, arrest history was positively associated with physical and psychological aggression perpetration against an intimate partner for men only, such that more previous arrests were associated with more frequent aggression. These results provide evidence that many men and women arrested for domestic violence have engaged in a number of diverse criminal acts during their lifetimes, suggesting that BIPs may need to address general criminal behavior