Seth Quackenbush

FEWZ 2.0: A code for hadronic Z production at next-to-next-to-leading order ☆

Abstract We introduce an improved version of the simulation code FEWZ (Fully Exclusive W and Z Production) for hadron collider production of lepton pairs through the Drell–Yan process at next-to-next-to-leading order (NNLO) in the strong coupling constant. The program is fully differential in the phase space of leptons and additional hadronic radiation. The new version offers users significantly more options for customization. FEWZ now bins multiple, user-selectable histograms during a single run, and produces parton distribution function (PDF) errors automatically. It also features a significantly improved integration routine, and can take advantage of multiple processor cores locally or on the Condor distributed computing system. We illustrate the new features of FEWZ by presenting numerous phenomenological results for LHC physics. We compare NNLO QCD with initial ATLAS and CMS results, and discuss in detail the effects of detector acceptance on the measurement of angular quantities associated with Z-boson production. We address the issue of technical precision in the presence of severe phase-space cuts. Program summary Program title: FEWZ Catalogue identifier: AEJP_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEJP_v1_0.html Program obtainable from: CPC Program Library, Queenʼs University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 6 280 771 No. of bytes in distributed program, including test data, etc.: 173 027 645 Distribution format: tar.gz Programming language: Fortran 77, C++, Python Computer: Mac, PC Operating system: Mac OSX, Unix/Linux Has the code been vectorized or parallelized?: Yes. User-selectable, 1 to 219 RAM: 200 Mbytes for common parton distribution functions Classification: 11.1 External routines: CUBA numerical integration library, numerous parton distribution sets (see text); these are provided with the code. Nature of problem: Determination of the Drell–Yan Z / photon production cross section and decay into leptons, with kinematic distributions of leptons and jets including full spin correlations, at next-to-next-to-leading order in the strong coupling constant. Solution method: Virtual loop integrals are decomposed into master integrals using automated techniques. Singularities are extracted from real radiation terms via sector decomposition, which separates singularities and maps onto suitable phase space variables. Result is convoluted with parton distribution functions. Each piece is numerically integrated over phase space, which allows arbitrary cuts on the observed particles. Each sample point may be binned during numerical integration, providing histograms, and reweighted by parton distribution function error eigenvectors, which provides PDF errors. Restrictions: Output does not correspond to unweighted events, and cannot be interfaced with a shower Monte Carlo. Additional comments: !!!!! The distribution file for this program is over 170 Mbytes and therefore is not delivered directly when download or E-mail is requested. Instead a html file giving details of how the program can be obtained is sent. Running time: One day for total cross sections with 0.1% integration errors assuming typical cuts, up to 1 week for smooth kinematic distributions with sub-percent integration errors for each bin.

Topological String Theory on Compact Calabi–Yau: Modularity and Boundary Conditions

The topological string partition function Z(λ,t,t) =exp(λ2 g-2 Fg(t, t)) is calculated on a compact Calabi–Yau M. The Fg(t, t) fulfil the holomorphic anomaly equations, which imply that ψ=Z transforms as a wave function on the symplectic space H3(M, Z). This defines it everywhere in the moduli space M(M) along with preferred local coordinates. Modular properties of the sections Fg as well as local constraints from the 4d effective action allow us to fix Z to a large extent. Currently with a newly found gap condition at the conifold, regularity at the orbifold and the most naive bounds from Castelnuovo’s theory, we can provide the boundary data, which specify Z, e.g. up to genus 51 for the quintic.

W physics at the LHC with FEWZ 2.1

Abstract We present an updated version of the FEWZ ( F ully E xclusive W and Z production) code for the calculation of W ± and γ ∗ / Z production at next-to-next-to-leading order in the strong coupling. Several new features and observables are introduced, and an order-of-magnitude speed improvement over the performance of FEWZ 2.0 is demonstrated. New phenomenological results for W ± production and comparisons with LHC data are presented, and used to illustrate the range of physics studies possible with the features of FEWZ 2.1. We demonstrate with an example the importance of directly comparing fiducial-region measurements with theoretical predictions, rather than first extrapolating them to the full phase space. Program summary Program title : FEWZ 2.1 Catalogue identifier : AEJP_v1_1 Program summary URL : http://cpc.cs.qub.ac.uk/summaries/AEJP_v1_1.html Program obtainable from : CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions : Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc. : 12003230 No. of bytes in distributed program, including test data, etc. : 769 Distribution format : tar.gz Programming language : Fortran 77, C++, Python 2.4. Computer : x86/x86-64. Operating system : Unix/Linux, Mac OSX. RAM : 200 Mbytes Classification : 11.1. External routines : CUBA (included), LHAPDF (optional) Catalogue identifier of previous version : AEJP_v1_0 Journal reference of previous version : Comput. Phys. Comm. 182 (2011) 2388 Does the new version supersede the previous version? : Yes Nature of problem : Calculation of hadroproduction of W bosons, with differential distributions, at next-to-next-to-leading order in the strong coupling. Solution method : Integral reduction, sector decomposition, numerical integration Reasons for new version : Reintroduction of W boson to FEWZ 2 Summary of revisions : Addition of W boson production, now can run in W or Z/gamma mode. LHAPDF interface added. Large speed improvements achieved through caching repeat function calls. New observables and histograms. Improved histogram binning. Additional comments : Running with all histograms on requires approx. 1 GB of disk space to store intermediate files. !!!!! The distribution file for this program is over 290 Mbytes and therefore is not delivered directly when download or e-mail is requested. Instead an html file giving details of how the program can be obtained is sent.!!!!! Running time : 2 hours to achieve NNLO precision in cross section on multicore machines, up to a few days for quality kinematic distributions. Cluster running is considerably faster.

Calculation of W b b ¯ production via double parton scattering at the LHC

We investigate the potential to observe double parton scattering at the Large Hadron Collider in pp{yields}WbbX{yields}l{nu}bbX at 7 TeV. Our analysis tests the efficacy of several kinematic variables in isolating the double parton process of interest from the single parton process and relevant backgrounds for the first 10 fb{sup -1} of integrated luminosity. These variables are constructed to expose the independent nature of the two subprocesses in double parton scattering, pp{yields}l{nu}X and pp{yields}bbX. We use next-to-leading order perturbative predictions for the double parton and single parton scattering components of Wbb and for the pertinent backgrounds. The next-to-leading order contributions are important for a proper description of some of the observables we compute. We find that the double parton process can be identified and measured with significance S/{radical}(B){approx}10, provided the double parton scattering effective cross section {sigma}{sub eff}{approx}12 mb.

Parton distributions and the

We examine the sources of parton distribution errors in the

W

W

mass measurement

mass measurement, and point out shortcomings in the existing literature. Optimistic assumptions about strategies to reduce the error by normalizing to

Precision studies of vector-boson production with heavy quarks at the LHC: the case of

Z

Z + b

observables are examined and found to rely too heavily on assumptions about the parametrization and degrees of freedom of the parton distribution functions (PDFs). We devise a strategy to combine measurements as efficiently as possible using error correlations to reduce the overall uncertainty of the measurement, including

jet.

Z